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Sample records for age sex ratio

  1. Analysis of web height ratios according to age and sex.

    PubMed

    Sari, Elif

    2015-06-01

    Each component of the web space, a three-dimensional structure, should be carefully created during reconstruction of web space loss. One of these web space components is the web height. In this study, the dorsal view of subjects' hands was analyzed to determine the web height ratios. The web height ratios were then compared with respect to age and sex. The second and third web height ratios differed between adult men and women and between children and adults. However, no differences were observed among children. This study is unique because it focuses on the web height ratios of all web spaces according to age and sex and provides a very easy-to-use scale that may help surgeons to perform web space reconstruction. Moreover, the present study adds to the literature by providing information on the first web height ratios of the hand.

  2. Age at marriage, sex-ratios, and ethnic heterogamy.

    PubMed

    Stier, H; Shavit, Y

    1994-05-01

    "This paper focuses on the effects of age at marriage and the sex-ratio on patterns of ethnic homogamy among Israeli women. We hypothesize that later marriages are more likely than early marriages to be heterogamous as the 'marriage market' shifts from school to the work-place. By the same token, when facing severe marriage squeezes women will be forced to out-marry. Employing data from the 1983 census, we model mate selection of women from Afro-Asian and Euro-American origin in various birth-cohorts. The results do not fully support our hypotheses: we find that in and of itself, age at marriage does not enhance ethnic heterogamy."

  3. Brief Report: Parental Age and the Sex Ratio in Autism

    ERIC Educational Resources Information Center

    Anello, Alene; Reichenberg, Abraham; Luo, Xiaodong; Schmeidler, James; Hollander, Eric; Smith, Christopher J.; Puleo, Connor M.; Kryzak, Lauren A.; Silverman, Jeremy M.

    2009-01-01

    The male-to-female (M:F) ratio for autism spectrum disorders (ASD), typically about 4:1, appears to decrease with increasing paternal age, but this relationship has not been systematically tested. With 393 ASD cases from families with two or more ASD cases, we categorized paternal age into five age groups (less than 30, 30-34, 35-39, 40-44, 45+)…

  4. Sex ratio of equine offspring is affected by the ages of the mare and stallion.

    PubMed

    Santos, Marianna Machado; Maia, Leonardo Lara; Nobre, Daniel Magalhães; Oliveira Neto, José Ferraz; Garcia, Tiago Rezende; Lage, Maria Coeli Gomes Reis; de Melo, Maria Isabel Vaz; Viana, Walmir Santos; Palhares, Maristela Silveira; da Silva Filho, José Monteiro; Santos, Renato Lima; Valle, Guilherme Ribeiro

    2015-10-15

    The aim of this study was to determine the influence of parental age on the sex ratio of offspring in horses. Two trials were performed. In the first trial, the data from a randomly obtained population with a 1:1 sex ratio of 59,950 Mangalarga Marchador horses born in Brazil from 1990 to 2011 were analyzed. The sex ratios of the offspring were compared among groups according to the mare and the stallion ages (from 3 to 25 years). In the first step of the analysis, the mares and stallions were grouped according to age in 5-year intervals. In the second step, the groups were based on the parental age gap at conception. In the third step, the group of the mares and stallions with similar ages from the second step was subdivided, and the different parental age subgroups that were divided into 5-year intervals were compared. In the fourth step, the sex ratio of the offspring was determined according to the ages of the mares and the stallions at conception. The second trial was based on the data from 253 horses of several breeds that were born after natural gestation into a herd from 1989 to 2010, and the offspring of groups that were younger or older than 15 years were compared. The data from both trials were analyzed using a chi-square test (P ≤ 0.01 for the first trial; and P ≤ 0.05 for the second trial) for the comparisons of the sex ratios. In the first trial, the Spearman test (P ≤ 0.01) was used to verify the correlations between the parental age and the offspring sex ratio. In the first trial, the offspring sex ratio decreased as the mare or stallion age increased, and the decrease was more marked for the mares than for the stallions. In the second trial, the mares older than 15 years had more fillies than the younger mares, but the stallion age had no effect on the sex of the offspring. The first trial, with a large number of horses, revealed the pattern of the distribution of the sex ratios of offspring according to the parental age in horses, whereas the

  5. Age and Sex Ratios in a High-Density Wild Red-Legged Partridge Population

    PubMed Central

    Nadal, Jesús; Ponz, Carolina; Margalida, Antoni

    2016-01-01

    The dynamics of a wild red-legged partridge population were examined over a 14-year period in Spain to identify patterns in age and sex ratios in relation to weather parameters, and to assess the importance of these parameters in population dynamics and management. The results gave age ratios of 1.07 (but 2.13 in July counts), juvenile sex ratios of 1.01 and adult sex ratios of 1.47. Overall, 12% more females were hatched and female juvenile mortality was 7.3% higher than in males. Sex differential mortality explains the 19.2% deficit in adult females, which are more heavily predated than males during the breeding period. Accordingly, age ratios are dependent on sex ratios and both are density dependent. Over time, ratios and density changes appear to be influenced by weather and management. When the habitat is well conserved, partridge population dynamics can be explained by a causal chain: weather operates on net primary production, thereby affecting partridge reproduction and predation and, as a result, age and sex ratios in the October population. A reduction in the impact of predation (i.e. the effects of ground predators on eggs, chicks and breeding females) is the key factor to improve the conservation of partridge populations and associated biological processes. PMID:27508503

  6. Large-scale age-dependent skewed sex ratio in a sexually dimorphic avian scavenger.

    PubMed

    Lambertucci, Sergio A; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando

    2012-01-01

    Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed.

  7. Large-Scale Age-Dependent Skewed Sex Ratio in a Sexually Dimorphic Avian Scavenger

    PubMed Central

    Lambertucci, Sergio A.; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando

    2012-01-01

    Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed. PMID:23029488

  8. Offspring sex ratio in red-winged blackbirds is dependent on maternal age.

    PubMed

    Blank, J L; Nolan, V

    1983-10-01

    In a marsh-breeding population of red-winged blackbirds, the sex ratio of offspring that survived to leave the nest varied with maternal age. Old mothers produced an excess of male fledglings, middle-aged mothers produced almost equal proportions of males and females, and young mothers produced nearly twice as many females as males. More males than females hatched from the eggs of old mothers, whereas among newly hatched progeny of middle-aged and young mothers the sex ratio did not differ from unity. The hatching rate of eggs of old mothers was unusually low, suggesting that the biased sex ratio of their hatchlings may have been caused by more frequent death of female embryos, although other possibilities can be imagined. Starvation of nestlings after hatching also affected the sex ratio among young that left the nest. When starvation occurred, it fell principally on young produced by the last and next-to-last eggs laid in the clutch. Because old mothers allocated relatively more energy to those eggs than to earlier-laid eggs, whereas young mothers apportioned energy equally to their eggs, few nestlings of old mothers but many nestlings of young mothers starved. Most nestlings that died were male. It followed that the male bias in sex ratio of progeny of old mothers did not change between hatching and nestleaving, but the ratio among progeny of young mothers shifted after hatching to a strong bias favoring females at nest-leaving.

  9. Does breeding population trajectory and age of nesting females influence disparate nestling sex ratios in two populations of Cooper's hawks?

    PubMed

    Rosenfield, Robert N; Stout, William E; Giovanni, Matthew D; Levine, Noah H; Cava, Jenna A; Hardin, Madeline G; Haynes, Taylor G

    2015-09-01

    Offspring sex ratios at the termination of parental care should theoretically be skewed toward the less expensive sex, which in most avian species would be females, the smaller gender. Among birds, however, raptors offer an unusual dynamic because they exhibit reversed size dimorphism with females being larger than males. And thus theory would predict a preponderance of male offspring. Results for raptors and birds in general have been varied although population-level estimates of sex ratios in avian offspring are generally at unity. Adaptive adjustment of sex ratios in avian offspring is difficult to predict perhaps in part due to a lack of life-history details and short-term investigations that cannot account for precision or repeatability of sex ratios across time. We conducted a novel comparative study of sex ratios in nestling Cooper's hawks (Accipiter cooperii) in two study populations across breeding generations during 11 years in Wisconsin, 2001-2011. One breeding population recently colonized metropolitan Milwaukee and exhibited rapidly increasing population growth, while the ex-Milwaukee breeding population was stable. Following life-history trade-off theory and our prediction regarding this socially monogamous species in which reversed sexual size dimorphism is extreme, first-time breeding one-year-old, second-year females in both study populations produced a preponderance of the smaller and cheaper sex, males, whereas ASY (after-second-year), ≥2-year-old females in Milwaukee produced a nestling sex ratio near unity and predictably therefore a greater proportion of females compared to ASY females in ex-Milwaukee who produced a preponderance of males. Adjustment of sex ratios in both study populations occurred at conception. Life histories and selective pressures related to breeding population trajectory in two age cohorts of nesting female Cooper's hawk likely vary, and it is possible that these differences influenced the sex ratios we documented for

  10. Sex ratio of congenital abnormalities in the function of maternal age: a population-based study.

    PubMed

    Csermely, Gyula; Urbán, Robert; Czeizel, Andrew E; Veszprémi, Béla

    2015-05-01

    Maternal age effect is well-known in the origin of numerical chromosomal aberrations and some isolated congenital abnormalities (CAs). The sex ratio (SR), i.e. number of males divided by the number of males and females together, of most CAs deviates from the SR of newborn population (0.51). The objective of this analysis was to evaluate the possible association of maternal age with the SR of isolated CAs in a population-based large dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-1996. First, SR of 24 CA entities/groups was estimated in 21,494 patients with isolated CA. In the next step SR of different maternal age groups was compared to the mean SR of the given CA-groups. The SR of four CA-groups showed some deviation in certain maternal age groups. Cases with anencephaly had female excess in young mothers (<25 years). Cases with skull's CAs particularly craniosynostosis had a male excess in cases born to women over 30 years. Two other CA groups (cleft lip ± palate and valvar pulmonic stenosis within the group of right-sided obstructive defect of heart) had significant deviation in SR of certain maternal age groups from the mean SR, but these deviations were not harmonized with joining age groups and thus were considered as a chance effect due to multiple testing. In conclusion, our study did not suggest that in general SR of isolated CAs might be modified by certain maternal age groups with some exception such as anencephaly and craniosynostosis.

  11. Auger electron spectroscopy for the determination of sex and age related Ca/P ratio at different bone sites

    SciTech Connect

    Balatsoukas, Ioannis; Kourkoumelis, Nikolaos; Tzaphlidou, Margaret

    2010-10-15

    The Ca/P ratio of normal cortical and trabecular rat bone was measured by Auger electron spectroscopy (AES). Semiquantitative analysis was carried out using ratio techniques to draw conclusions on how age, sex and bone site affect the relative composition of calcium and phosphorus. Results show that Ca/P ratio is not sex dependent; quite the opposite, bone sites exhibit variations in elemental stoichiometry where femoral sections demonstrate higher Ca/P ratio than rear and front tibias. Age-related changes are more distinct for cortical bone in comparison with the trabecular bone. The latter's Ca/P ratio remains unaffected from all the parameters under study. This study confirms that AES is able to successfully quantify bone mineral main elements when certain critical points, related to the experimental conditions, are addressed effectively.

  12. Reanalysis of Bell, Weinberg, and Hammersmith's data on birth order, sibling sex ratio, and parental age in homosexual men.

    PubMed

    Blanchard, R; Zucker, K J

    1994-09-01

    The authors compared parental age, birth order, and sex ratio of siblings for 575 homosexual men and 284 heterosexual men, matched on age and education. They were originally part of Bell, Weinberg, and Hammersmith's large-scale study of male and female homosexuality. The results confirmed the previous findings that homosexual men have older fathers and later births than do heterosexual men but not the finding that homosexual men have larger proportions of brothers. The collective findings suggest that birth order is perhaps the single most reliable demographic difference between homosexual and heterosexual men.

  13. Variance in age-specific sex composition of Pacific halibut catches, and comparison of statistical and genetic methods for reconstructing sex ratios

    NASA Astrophysics Data System (ADS)

    Loher, Timothy; Woods, Monica A.; Jimenez-Hidalgo, Isadora; Hauser, Lorenz

    2016-01-01

    Declines in size at age of Pacific halibut Hippoglossus stenolepis, in concert with sexually-dimorphic growth and a constant minimum commercial size limit, have led to the expectation that the sex composition of commercial catches should be increasingly female-biased. Sensitivity analyses suggest that variance in sex composition of landings may be the most influential source of uncertainty affecting current understanding of spawning stock biomass. However, there is no reliable way to determine sex at landing because all halibut are eviscerated at sea. In 2014, a statistical method based on survey data was developed to estimate the probability that fish of any given length at age (LAA) would be female, derived from the fundamental observation that large, young fish are likely female whereas small, old fish have a high probability of being male. Here, we examine variability in age-specific sex composition using at-sea commercial and closed-season survey catches, and compare the accuracy of the survey-based LAA technique to genetic markers for reconstructing the sex composition of catches. Sexing by LAA performed best for summer-collected samples, consistent with the hypothesis that the ability to characterize catches can be influenced by seasonal demographic shifts. Additionally, differences between survey and commercial selectivity that allow fishers to harvest larger fish within cohorts may generate important mismatch between survey and commercial datasets. Length-at-age-based estimates ranged from 4.7% underestimation of female proportion to 12.0% overestimation, with mean error of 5.8 ± 1.5%. Ratios determined by genetics were closer to true sample proportions and displayed less variability; estimation to within < 1% of true ratios was limited to genetics. Genetic estimation of female proportions ranged from 4.9% underestimation to 2.5% overestimation, with a mean absolute error of 1.2 ± 1.2%. Males were generally more difficult to assign than females: 6.7% of

  14. The relationship between paternal age, sex ratios, and aneuploidy frequencies in human sperm, as assessed by multicolor FISH

    SciTech Connect

    Martin, R.H.; Spriggs, E. |; Ko, E.

    1995-12-01

    We studied the frequencies of X- and Y-chromosome bearing sperm, diploidy and disomy for chromosomes 1, 12, X, and Y in sperm from 10 normal men aged 21 - 52 years, to determine whether there was any relationship between donor age and any of these variables. Multicolor FISH was used to control for lack of probe hybridization and to distinguish diploid sperm from disomic sperm. A minimum of 10,000 sperm per donor was evaluated for each chromosome, for a total of 225,846 sperm studied. Sperm were considered disomic if two fluorescent signals were separated by a minimal distance of one signal domain. The mean frequencies of X- and Y-bearing sperm were 50.1% and 49.0%, respectively; not significantly different from 50%. There was no correlation between paternal age and {open_quotes}sex ratio {close_quotes} in sperm. Similarly, there was no association between the frequency of diploid sperm (mean, .16%; range, .06%-.42%) and donor age. For disomy frequencies, there was no relationship between donor age and disomy 12 (mean, .16%; range, .10%-.25%), XX (mean, .07%; range, .03%-.17%), and XY sperm (mean, .16%; range, .08%-.24%). There was a significant increase in the frequency of YY sperm (P = .04; mean, .18%; range, .10%-.43%) and disomy 1 sperm (P = .01; mean, .11%; range, .05%-.18%) with donor age. In summary, our results do not support a correlation between paternal age and sex ratio or diploidy. A relationship between paternal age and disomy was observed for disomy 1 and YY sperm but not for disomy 12, XX or XY sperm. 37 refs., 3 tabs.

  15. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy.

    PubMed

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; Sam Ma, Zhanshan

    2016-12-23

    There are three sex ratio strategies (SRS) in nature-male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton's local mate competition (LMC) and Clark's local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC &LRC) in the field of SRS research.

  16. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy

    PubMed Central

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; (Sam) Ma, Zhanshan

    2016-01-01

    There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s local mate competition (LMC) and Clark’s local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research. PMID:28009000

  17. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy

    NASA Astrophysics Data System (ADS)

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; (Sam) Ma, Zhanshan

    2016-12-01

    There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s local mate competition (LMC) and Clark’s local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research.

  18. Growth, age at metamorphosis, and sex ratio of northern brook lamprey in a tributary of southern Lake Superior

    USGS Publications Warehouse

    Purvis, Harold A.

    1970-01-01

    Growth was studied of five year classes of the northern brook lamprey, Ichthyomyzon fossor, collected from the Sturgeon River during intervals between treatment of the stream with a lampricide. Growth varied considerably among year classes. Larvae of the 1963 year class were slightly longer at age II and 30% longer at age III than the III-group larvae of the 1960 year class. About 6% of 558 III-group lampreys of the 1963 year class had metamorphosed by 17 August 1966. Although the sex ratio of larvae was about 1:1, 97% of the metamorphosed lampreys were males. The distribution of pigmentation on the caudal fin and upper lip in ammocoetes less than 40 mm long permitted accurate and rapid separation of northern brook lampreys from the sea lamprey, Petromyzon marinus.

  19. On the variability of alligator sex ratios

    USGS Publications Warehouse

    Nichols, J.D.; Chabreck, R.H.

    1980-01-01

    Samples of alligators from wild and 'farm' populations exhibited disproportionate sex ratios. Males predominated among young alligators from wild populations, whereas females were much more abundant than males in the farm population, where resources were superabundant. These results and other considerations lead us to hypothesize that environmental factors influence sex determination in alligators. During favorable environmental conditions natural selection is expected to favor a preponderance of the sex whose individuals exhibit the greater environmentally associated variation in relative fitness. We hypothesize that environmentally associated variation in age at sexual maturity of females produces sufficient variation in relative fitness of females to result in selection for low sex ratios during periods of resource abundance.

  20. Sex ratios in pheasant research and management

    USGS Publications Warehouse

    Dale, F.H.

    1952-01-01

    Sex ratios are of primary importance in interpretation of extensive studies of pheasant populations. They are necessary for converting crowing-cock indices to population estimates even where annual trends are to be studied in the same area. Reliability of population estimates from hunting season kill of pheasants suffers primarily from inability to estimate sex ratios accurately. Fall sex ratio is an index to production and where adult sex ratios are divergent can serve as a good check on production per hen. Age ratios of cocks cannot be interpreted directly as an index of productivity, even within the boundaries of one state, unless adult sex ratios are known. The relationship between observed and actual sex ratio varies significantly from season to season and according to the method of observation. In view of their importance in population studies and the lack of reliability of present methods, it is believed that intensive studies on techniques for obtaining sex ratios are a major need in pheasant research.

  1. Sex ratios in bumble bees

    PubMed Central

    Bourke, A. F. G.

    1997-01-01

    The median proportion of investment in females among 11 populations of seven bumble bee (Bombus) species was 0.32 (range 0.07 to 0.64). By contrast, two species of workerless social parasites in the related genus Psithyrus had female-biased sex allocation, the reasons for which remain unclear. Male-biased sex allocation in Bombus contradicts the predictions of Trivers and Hare's sex ratio model for the social Hymenoptera, which are that the population sex investment ratio should be 0.5 (1:1) under queen control and 0.75 (3:1 females:males) under worker control (assuming single, once-mated, outbred queens and non-reproductive workers). Male bias in Bombus does not appear to be either an artefact, or purely the result of symbiotic sex ratio distorters. According to modifications of the Trivers–Hare model, the level of worker male-production in Bombus is insufficient to account for observed levels of male bias. There is also no evidence that male bias arises from either local resource competition (related females compete for resources) or local mate enhancement (related males cooperate in securing mates). Bulmer presented models predicting sexual selection for protandry (males are produced before females) in annual social Hymenoptera and, as a consequence (given some parameter values), male-biased sex allocation. Bumble bees fit the assumptions of Bulmer's models and are protandrous. These models therefore represent the best current explanation for the bees' male-biased sex investment ratios. This conclusion suggests that the relative timing of the production of the sexes strongly influences sex allocation in the social Hymenoptera.

  2. Evolutionarily stable sex ratios and mutation load.

    PubMed

    Hough, Josh; Immler, Simone; Barrett, Spencer C H; Otto, Sarah P

    2013-07-01

    Frequency-dependent selection should drive dioecious populations toward a 1:1 sex ratio, but biased sex ratios are widespread, especially among plants with sex chromosomes. Here, we develop population genetic models to investigate the relationships between evolutionarily stable sex ratios, haploid selection, and deleterious mutation load. We confirm that when haploid selection acts only on the relative fitness of X- and Y-bearing pollen and the sex ratio is controlled by the maternal genotype, seed sex ratios evolve toward 1:1. When we also consider haploid selection acting on deleterious mutations, however, we find that biased sex ratios can be stably maintained, reflecting a balance between the advantages of purging deleterious mutations via haploid selection, and the disadvantages of haploid selection on the sex ratio. Our results provide a plausible evolutionary explanation for biased sex ratios in dioecious plants, given the extensive gene expression that occurs across plant genomes at the haploid stage.

  3. Egg laying pattern, egg weight, body weight at hatch, and sex ratio bias relative to oviposition time of young-and mid-age broiler breeders.

    PubMed

    Zakaria, A H; Omar, O H

    2013-09-01

    Two experiments were conducted to determine oviposition pattern and the effect of oviposition time on egg weight, body weight at hatch, and sex ratio of hatched chickens. In Experiment 1, eggs were collected from young and mid-age broiler flocks for 6 consecutive days at hourly intervals between 0400 and 2000h. In Experiment 2, eggs were categorized to represent eggs where oviposition occurred early, middle and late in the clutch (later in the day). These eggs were incubated to determine body weight at hatch and sex ratio of hatched chickens relative to oviposition time. Time of oviposition was affected by age. For the young flock, the percentage of ovipositions occurring before the 1100h was 79%. In contrast to the young flock, the percentage of ovipositions occurring before the 1100h in the mid-age flock was less (68%; P<0.01). Furthermore, for the mid-age flock, the percentage of ovipositions occurring from 1200 to 1700h was greater (P<0.01) at 32% in comparison to that of the younger flock at 21%. Egg weights when oviposition occurred earlier in the day were greater (P<0.01) than when oviposition occurred in the middle and later in the clutch (later in the day). Similarly, body weight at hatch of chicks from eggs where oviposition occurred earlier in the day was heavier than when oviposition occurred in the middle and later in the clutch (later in the day).With hatching of the eggs from hens when ovipositions occurred earlier in the day, there was a female sex bias. Differences in egg weights, body weight at hatch, and sex ratio due to time of oviposition suggest that oviposition time together with incubation conditions should be considered for obtaining greater uniformity and growth of chickens.

  4. Sex ratio in relation to fathers' occupations.

    PubMed Central

    Dickinson, H O; Parker, L

    1997-01-01

    OBJECTIVE: To investigate whether the sex ratio of children varies between fathers of different occupations. METHODS: The sex ratio (the ratio of the number of boys to the number of girls at birth) was calculated in relation to paternal occupation in the cohort of all 253,433 live births in Cumbria, north west England, from 1950-89. Exact binomial confidence intervals were used to estimate whether the sex ratio in each occupational category was significantly different from that for the rest of the cohort. RESULTS: There were fewer occupational categories with significantly different sex ratios at the 5% level than expected by chance alone, assuming the same binomial distribution of sexes at birth within each paternal occupation. CONCLUSIONS: Significant variation of the sex ratio with fathers' occupations was not found. There is some evidence that the sex ratio shows less variance than expected under a binomial model which assumes independence of the sex of each child; a possible explanation of this may be parental preference for limiting family size after children of both sexes have been born or some other factor which results in children within a family being more likely to be of both sexes rather than the same sex. PMID:9470894

  5. Radiation and the sex ratio in man.

    PubMed

    SCHULL, W J; NEEL, J V

    1958-08-15

    An analysis of new data concerning the sex of children born to the survivors of the atomic bombings of Hiroshima and Nagasaki, together with a reanalysis of the data previously presented by Neel and Schull (9), reveals significant changes in the sex ratio of these children, changes in the direction to be expected if exposure had resulted in the induction of sex-linked lethal mutations (16).

  6. Sex ratios in fetuses and liveborn infants with autosomal aneuploidy

    SciTech Connect

    Heuther, C.A.; Martin, R.L.M.; Stoppelman, S.M.

    1996-06-14

    Ten data sources were used substantially to increase the available data for estimating fetal and livebirth sex ratios for Patau (trisomy 13), Edwards (trisomy 18), and Down (trisomy 21) syndromes and controls. The fetal sex ratio estimate was 0.88 (N = 584) for trisomy 13, 0.90 (N = 1702) for trisomy 18, and 1.16 (N = 3154) for trisomy 21. All were significantly different from prenatal controls (1.07). The estimated ratios in prenatal controls were 1.28 (N = 1409) for CVSs and 1.06 (N = 49427) for amniocenteses, indicating a clear differential selection against males, mostly during the first half of fetal development. By contrast, there were no sex ratio differences for any of the trisomies when comparing gestational ages <16 and >16 weeks. The livebirth sex ratio estimate was 0.90 (N = 293) for trisomy 13, 0.63 (N = 497) for trisomy 18, and 1.15 (N = 6424) for trisomy 21, the latter two being statistically different than controls (1.05) (N = 3660707). These ratios for trisomies 13 and 18 were also statistically different than the ratio for trisomy 21. Only in trisomy 18 did the sex ratios in fetuses and livebirths differ, indicating a prenatal selection against males >16 weeks. No effects of maternal age or race were found on these estimates for any of the fetal or livebirth trisomies. Sex ratios for translocations and mosaics were also estimated for these aneuploids. Compared to previous estimates, these results are less extreme, most likely because of larger sample sizes and less sample bias. They support the hypothesis that these trisomy sex ratios are skewed at conception, or become so during embryonic development through differential intrauterine selection. The estimate for Down syndrome livebirths is also consistent with the hypothesis that its higher sex ratio is associated with paternal nondisjunction. 36 refs., 5 tabs.

  7. The age, growth, sexual maturity, and sex ratio of the common whitefish, Coregonus clupeaformis (Mitchill), of Lake Huron

    USGS Publications Warehouse

    Van Oosten, John

    1939-01-01

    During five years (1939-43) of nutritional research on pen-reared bobwhite quail at the Patuxent Research Refuge, Bowie, Maryland, observations on picking among birds of all ages showed the following results: 1. Picking occurred on all grains tested: corn, wheat, oats, oat groats, barley, millet, buckwheat, kaffir, and mixtures of cereals. The lowest incidence was with buckwheat as the sole grain in a growing diet....2. Picking occurred on all levels of fiber from one to 11per cent in a growing diet....3. Picking occurred on various grinds of corn, barley, and oats, but was least when these cereals were ground in a hammer mill with 3/32 inch mesh screen....4. The incidence was as high on diets containing animal protein as on those containing no animal protein. ....5. After picking began, the addition of one or two per cent of salt to the diet for several days was effective, in many instances, in checking the disorder. Results at the Refuge and the answers to questionnaires from 222 private propagators of gamebirds showed that in two-thirds. of the cases, treatment with an increased quantity of salt successfully stopped the trouble. As a preventative, however, salt was of little value. Picking occurred on both low and high levels of salt.....6. Supplementing the regular diet with certain feed concentrates such as fishmeal, soybean oil meal, liver meal, or chopped greens offered in a separate feeder for a day or two, was as efficacious as the addition of salt.....7. More picking occurred among quail chicks on a 22 per cent level of protein than on higher levels.....8. There was less picking on diets relished by the birds than on those seemingly unpalatable.....9. There was no correlation. between the amount of floor space per chick and the incidence of picking.....10. Increasing the feeding and drinking space seemed to have a marked beneficial effect.....11. Some adult birds on wire floors resorted to self-picking of their feet after the toes were frost-bitten.

  8. Human behaviour: sex ratio and the city.

    PubMed

    Székely, Áron; Székely, Tamás

    2012-09-11

    The ratio of males to females in a population is known to influence the behaviour, life histories and demography of animals. A recent experimental study finds that sex ratio also affects human economic behaviour, and in a manner consistent with evolutionary theory.

  9. Child underreporting, fertility, and sex ratio imbalance in China.

    PubMed

    Goodkind, Daniel

    2011-02-01

    Child underreporting is often neglected in studies of fertility and sex ratio imbalance in China. To improve estimates of these measures, I use intercensal comparisons to identify a rise in underreporting, which followed the increased enforcement and penalization under the birth planning system in 1991. A new triangulation of evidence indicates that about 19% of children at ages 0-4 were unreported in the 2000 census, more than double that of the 1990 census. This evidence contradicts assumptions underlying the fertility estimates of most recent studies. Yet, the analysis also suggests that China's fertility in the late 1990s (and perhaps beyond) was below officially adjusted levels. I then conduct a similar intercensal analysis of sex ratios of births and children, which are the world's highest primarily because of prenatal sex selection. However, given excess underreporting of young daughters, especially pronounced just after 1990, estimated ratios are lower than reported ratios. Sex ratios in areas with a "1.5-child" policy are especially distorted because of excess daughter underreporting, as well as sex-linked stopping rules and other factors, although it is unclear whether such policies increase use of prenatal sex selection. China's sex ratio at birth, once it is standardized by birth order, fell between 2000 and 2005 and showed a continuing excess in urban China, not rural China.

  10. Is Canada's sex ratio in decline?

    PubMed Central

    Dodds, L; Armson, B A

    1997-01-01

    In this issue (see pages 37 to 41) Dr. Bruce B. Allan and associates report a small but statistically significant decrease--of about 0.2%--in the proportion of male live births in Canada over the period 1970-90. In this editorial, factors that have been reported in the literature to influence sex ratio are examined within a Canadian context. The authors suggest that although the reasons for the apparent decline in the sex ratio in Canada are unclear, the increasing use of ovulation induction may be a contributing factor. Data from the Nova Scotia Atlee Perinatal Database are discussed with a view to explaining the trend observed in Atlantic Canada, but no obvious explanation emerges. The authors argue that when the period of observation is extended no overall change in the sex ratio is apparent. This would suggest a tendency toward stabilization rather than decline. PMID:9006564

  11. Kinship Institutions and Sex Ratios in India

    PubMed Central

    CHAKRABORTY, TANIKA; KIM, SUKKOO

    2010-01-01

    This article explores the relationship between kinship institutions and sex ratios in India at the turn of the twentieth century. Because kinship rules vary by caste, language, religion, and region, we construct sex ratios by these categories at the district level by using data from the 1901 Census of India for Punjab (North), Bengal (East), and Madras (South). We find that the male-to-female sex ratio varied positively with caste rank, fell as one moved from the North to the East and then to the South, was higher for Hindus than for Muslims, and was higher for northern Indo-Aryan speakers than for the southern Dravidian-speaking people. We argue that these systematic patterns in the data are consistent with variations in the institution of family, kinship, and inheritance. PMID:21308567

  12. Male pygmy hippopotamus influence offspring sex ratio

    PubMed Central

    Saragusty, Joseph; Hermes, Robert; Hofer, Heribert; Bouts, Tim; Göritz, Frank; Hildebrandt, Thomas B.

    2012-01-01

    Pre-determining fetal sex is against the random and equal opportunity that both conceptus sexes have by nature. Yet, under a wide variety of circumstances, populations shift their birth sex ratio from the expected unity. Here we show, using fluorescence in situ hybridization, that in a population of pygmy hippopotamus (Choeropsis liberiensis) with 42.5% male offspring, males bias the ratio of X- and Y-chromosome-bearing spermatozoa in their ejaculates, resulting in a 0.4337±0.0094 (mean±s.d.) proportion of Y-chromosome-bearing spermatozoa. Three alternative hypotheses for the shifted population sex ratio were compared: female counteract male, female indifferent, or male and female in agreement. We conclude that there appears little or no antagonistic sexual conflict, unexpected by prevailing theories. Our results indicate that males possess a mechanism to adjust the ratio of X- and Y-chromosome-bearing spermatozoa in the ejaculate, thereby substantially expanding currently known male options in sexual conflict. PMID:22426218

  13. Male pygmy hippopotamus influence offspring sex ratio.

    PubMed

    Saragusty, Joseph; Hermes, Robert; Hofer, Heribert; Bouts, Tim; Göritz, Frank; Hildebrandt, Thomas B

    2012-02-28

    Pre-determining fetal sex is against the random and equal opportunity that both conceptus sexes have by nature. Yet, under a wide variety of circumstances, populations shift their birth sex ratio from the expected unity. Here we show, using fluorescence in situ hybridization, that in a population of pygmy hippopotamus (Choeropsis liberiensis) with 42.5% male offspring, males bias the ratio of X- and Y-chromosome-bearing spermatozoa in their ejaculates, resulting in a 0.4337±0.0094 (mean±s.d.) proportion of Y-chromosome-bearing spermatozoa. Three alternative hypotheses for the shifted population sex ratio were compared: female counteract male, female indifferent, or male and female in agreement. We conclude that there appears little or no antagonistic sexual conflict, unexpected by prevailing theories. Our results indicate that males possess a mechanism to adjust the ratio of X- and Y-chromosome-bearing spermatozoa in the ejaculate, thereby substantially expanding currently known male options in sexual conflict.

  14. Sex Ratios at Birth and Environmental Temperatures

    NASA Astrophysics Data System (ADS)

    Lerchl, Alexander

    The relationship between average monthly air temperature and sex ratios at birth (SRB) was analyzed for children born in Germany during the period 1946-1995. Both the absolute temperature and - more markedly - the monthly temperature deviations from the overall mean were significantly positively correlated with the SRB (P<0.01) when temperatures were time-lagged against the SRB data by -10 or -11months. It is concluded that the sex of the offspring is partially determined by environmental temperatures prior to conception.

  15. Intragenomic conflict produces sex ratio dynamics that favor maternal sex ratio distorters.

    PubMed

    Rood, Elaine S; Freedberg, Steven

    2016-11-01

    Maternal sex ratio distorters (MSDs) are selfish elements that enhance their transmission by biasing their host's sex allocation in favor of females. While previous models have predicted that the female-biased populations resulting from sex ratio distortion can benefit from enhanced productivity, these models neglect Fisherian selection for nuclear suppressors, an unrealistic assumption in most systems. We used individual-based computer simulation modeling to explore the intragenomic conflict between sex ratio distorters and their suppressors and explored the impacts of these dynamics on population-level competition between species characterized by MSDs and those lacking them. The conflict between distorters and suppressors was capable of producing large cyclical fluctuations in the population sex ratio and reproductive rate. Despite fitness costs associated with the distorters and suppressors, MSD populations often exhibited enhanced productivity and outcompeted non-MSD populations in single and multiple-population competition simulations. Notably, the conflict itself is beneficial to the success of populations, as sex ratio oscillations limit the competitive deficits associated with prolonged periods of male rarity. Although intragenomic conflict has been historically viewed as deleterious to populations, our results suggest that distorter-suppressor conflict can provide population-level advantages, potentially helping to explain the persistence of sex ratio distorters in a range of taxa.

  16. Sex ratios at birth after induced abortion

    PubMed Central

    Urquia, Marcelo L.; Moineddin, Rahim; Jha, Prabhat; O’Campo, Patricia J.; McKenzie, Kwame; Glazier, Richard H.; Henry, David A.; Ray, Joel G.

    2016-01-01

    Background: Skewed male:female ratios at birth have been observed among certain immigrant groups. Data on abortion practices that might help to explain these findings are lacking. Methods: We examined 1 220 933 births to women with up to 3 consecutive singleton live births between 1993 and 2012 in Ontario. Records of live births, and induced and spontaneous abortions were linked to Canadian immigration records. We determined associations of male:female infant ratios with maternal birthplace, sex of the previous living sibling(s) and prior spontaneous or induced abortions. Results: Male:female infant ratios did not appreciably depart from the normal range among Canadian-born women and most women born outside of Canada, irrespective of the sex of previous children or the characteristics of prior abortions. However, among infants of women who immigrated from India and had previously given birth to 2 girls, the overall male:female ratio was 1.96 (95% confidence interval [CI] 1.75–2.21) for the third live birth. The male:female infant ratio after 2 girls was 1.77 (95% CI 1.26–2.47) times higher if the current birth was preceded by 1 induced abortion, 2.38 (95% CI 1.44–3.94) times higher if preceded by 2 or more induced abortions and 3.88 (95% CI 2.02–7.50) times higher if the induced abortion was performed at 15 weeks or more gestation relative to no preceding abortion. Spontaneous abortions were not associated with male-biased sex ratios in subsequent births. Interpretation: High male:female ratios observed among infants born to women who immigrated from India are associated with induced abortions, especially in the second trimester of pregnancy. PMID:27067818

  17. Maternal transmission, sex ratio distortion, and mitochondria.

    PubMed

    Perlman, Steve J; Hodson, Christina N; Hamilton, Phineas T; Opit, George P; Gowen, Brent E

    2015-08-18

    In virtually all multicellular eukaryotes, mitochondria are transmitted exclusively through one parent, usually the mother. In this short review, we discuss some of the major consequences of uniparental transmission of mitochondria, including deleterious effects in males and selection for increased transmission through females. Many of these consequences, particularly sex ratio distortion, have well-studied parallels in other maternally transmitted genetic elements, such as bacterial endosymbionts of arthropods. We also discuss the consequences of linkage between mitochondria and other maternally transmitted genetic elements, including the role of cytonuclear incompatibilities in maintaining polymorphism. Finally, as a case study, we discuss a recently discovered maternally transmitted sex ratio distortion in an insect that is associated with extraordinarily divergent mitochondria.

  18. Skewed Sex Ratios and Criminal Victimization in India

    PubMed Central

    South, Scott J.; Trent, Katherine; Bose, Sunita

    2014-01-01

    Although substantial research has explored the causes of India’s excessively masculine population sex ratio, few studies have examined the consequences of this surplus of males. We merge individual-level data from the 2004–2005 India Human Development Survey with data from the 2001 India population census to examine the association between the district-level male-to-female sex ratio at ages 15 to 39 and self-reports of victimization by theft, breaking and entering, and assault. Multilevel logistic regression analyses reveal positive and statistically significant albeit substantively modest effects of the district-level sex ratio on all three victimization risks. We also find that higher male-to-female sex ratios are associated with the perception that young unmarried women in the local community are frequently harassed. Household-level indicators of family structure, socioeconomic status, and caste, as well as areal indicators of women’s empowerment and collective efficacy, also emerge as significant predictors of self-reported criminal victimization and the perceived harassment of young women. The implications of these findings for India’s growing sex ratio imbalance are discussed. PMID:24682921

  19. Maladaptive sex ratio adjustment by a sex-changing shrimp in selective-fishing environments.

    PubMed

    Chiba, Susumu; Yoshino, Kenji; Kanaiwa, Minoru; Kawajiri, Toshifumi; Goshima, Seiji

    2013-05-01

    1. Selective harvesting is acknowledged as a serious concern in efforts to conserve wild animal populations. In fisheries, most studies have focused on gradual and directional changes in the life-history traits of target species. While such changes represent the ultimate response of harvested animals, it is also well known that the life history of target species plastically alters with harvesting. However, research on the adaptive significance of these types of condition-dependent changes has been limited. 2. We explored the adaptive significance of annual changes in the age at sex-change of the protandrous (male-first) hermaphroditic shrimp and examined how selective harvesting affects life-history variation, by conducting field observations across 13 years and a controlled laboratory experiment. In addition, we considered whether plastic responses by the shrimp would be favourable, negligible or negative with respect to the conservation of fishery resources. 3. The age at sex-change and the population structure of the shrimp fluctuated between years during the study period. The results of the field observations and laboratory experiment both indicated that the shrimp could plastically change the timing of sex-change in accordance with the age structure of the population. These findings provide the first concrete evidence of adult sex ratio adjustment by pandalid shrimp, a group that has been treated as a model in the sex allocation theory. 4. The sex ratio adjustment by the shrimp did not always seem to be sufficient, however, as the supplement of females is restricted by their annual somatic growth rate. In addition, adjusted sex ratios are further skewed by the unintentional female-selectivity of fishing activity prior to the breeding season, indicating that the occurrence of males that have postponed sex-change causes sex ratio adjustment to become unfavourable. 5. We conclude that the plastic responses of harvested animals in selective fishing environments

  20. Environmental sex reversal, Trojan sex genes, and sex ratio adjustment: conditions and population consequences.

    PubMed

    Stelkens, Rike B; Wedekind, Claus

    2010-02-01

    The great diversity of sex determination mechanisms in animals and plants ranges from genetic sex determination (GSD, e.g. mammals, birds, and most dioecious plants) to environmental sex determination (ESD, e.g. many reptiles) and includes a mixture of both, for example when an individual's genetically determined sex is environmentally reversed during ontogeny (ESR, environmental sex reversal, e.g. many fish and amphibia). ESD and ESR can lead to widely varying and unstable population sex ratios. Populations exposed to conditions such as endocrine-active substances or temperature shifts may decline over time due to skewed sex ratios, a scenario that may become increasingly relevant with greater anthropogenic interference on watercourses. Continuous exposure of populations to factors causing ESR could lead to the extinction of genetic sex factors and may render a population dependent on the environmental factors that induce the sex change. However, ESR also presents opportunities for population management, especially if the Y or W chromosome is not, or not severely, degenerated. This seems to be the case in many amphibians and fish. Population growth or decline in such species can potentially be controlled through the introduction of so-called Trojan sex genes carriers, individuals that possess sex chromosomes or genes opposite from what their phenotype predicts. Here, we review the conditions for ESR, its prevalence in natural populations, the resulting physiological and reproductive consequences, and how these may become instrumental for population management.

  1. Parasite Stress Predicts Offspring Sex Ratio

    PubMed Central

    Dama, Madhukar Shivajirao

    2012-01-01

    In this study, I predict that the global variation of offspring sex ratio might be influenced in part by the level of parasite stress. From an energetic standpoint, higher gestational costs of producing a male offspring could decrease male births in a population with limited resources. This implies that, any factor that limits the parental resources could be expected to favor female offspring production. Human sex ratio at birth (SRB) is believed to be influenced by numerous socioeconomic, biological, and environmental factors. Here, I test a prediction that parasite stress, by virtue of its effects on the general health condition, may limit the parental investment ability and therefore could influence the SRB at the population level. The statistical analysis supports this prediction, and show that the level of parasite stress has a significant inverse relation with population SRB across the world. Further, this relation is many-folds stronger than the association of SRB with other factors, like; polygyny, fertility, latitude, and son-preference. Hence, I propose that condition affecting ability of parasites (but not adaptive significance) could be a likely causal basis for the striking variation of SRB across populations. PMID:23049967

  2. [[On the change of sex ratio by the Japanese zodiac

    PubMed

    Sakai, H

    1989-04-01

    Changes in the sex ratio in Japan from 1899 to 1986 are analyzed using data from official sources. The emphasis is on differences in the sex ratio according to the signs of the Japanese zodiac. The author notes that although the significance of the zodiac on the sex ratio has been decreasing since the early 1970s, it still has a measurable impact.

  3. Sex investment ratios in eusocial Hymenoptera support inclusive fitness theory.

    PubMed

    Bourke, A F G

    2015-11-01

    Inclusive fitness theory predicts that sex investment ratios in eusocial Hymenoptera are a function of the relatedness asymmetry (relative relatedness to females and males) of the individuals controlling sex allocation. In monogynous ants (with one queen per colony), assuming worker control, the theory therefore predicts female-biased sex investment ratios, as found in natural populations. Recently, E.O. Wilson and M.A. Nowak criticized this explanation and presented an alternative hypothesis. The Wilson-Nowak sex ratio hypothesis proposes that, in monogynous ants, there is selection for a 1 : 1 numerical sex ratio to avoid males remaining unmated, which, given queens exceed males in size, results in a female-biased sex investment ratio. The hypothesis also asserts that, contrary to inclusive fitness theory, queens not workers control sex allocation and queen-worker conflict over sex allocation is absent. Here, I argue that the Wilson-Nowak sex ratio hypothesis is flawed because it contradicts Fisher's sex ratio theory, which shows that selection on sex ratio does not maximize the number of mated offspring and that the sex ratio proposed by the hypothesis is not an equilibrium for the queen. In addition, the hypothesis is not supported by empirical evidence, as it fails to explain 'split' (bimodal) sex ratios or data showing queen and worker control and ongoing queen-worker conflict. By contrast, these phenomena match predictions of inclusive fitness theory. Hence, the Wilson-Nowak sex ratio hypothesis fails both as an alternative hypothesis for sex investment ratios in eusocial Hymenoptera and as a critique of inclusive fitness theory.

  4. Preconception maternal polychlorinated biphenyl concentrations and the secondary sex ratio

    SciTech Connect

    Taylor, Kira C.; Jackson, Leila W.; Lynch, Courtney D.; Kostyniak, Paul J.; Buck Louis, Germaine M. . E-mail: louisg@mail.nih.gov

    2007-01-15

    The secondary sex ratio is the ratio of male to female live births and historically has ranged from 102 to 106 males to 100 females. Temporal declines have been reported in many countries prompting authors to hypothesize an environmental etiology. Blood specimens were obtained from 99 women aged 24-34 prior to attempting pregnancy and quantified for 76 polychlorinated biphenyl (PCB) congeners using dual column gas chromatography with electron capture detection. Women were prospectively followed until pregnancy or 12 cycles of trying. The odds of a male birth for three PCB groupings (total, estrogenic, anti-estrogenic) controlling for maternal characteristics were estimated using logistic regression. Among the 50 women with live births and PCB data, 26 female and 24 male infants were born (ratio 0.92). After adjusting for age and body mass index, odds of a male birth were elevated among women in the second (OR=1.29) and third (OR=1.48) tertiles of estrogenic PCBs; odds (OR=0.70) were reduced among women in the highest tertile of anti-estrogenic PCBs. All confidence intervals included one. The direction of the odds ratios in this preliminary study varied by PCB groupings, supporting the need to study specific PCB patterns when assessing environmental influences on the secondary sex ratio.

  5. Parental care and adaptive brood sex ratio manipulation in birds.

    PubMed Central

    Hasselquist, Dennis; Kempenaers, Bart

    2002-01-01

    Under many circumstances, it might be adaptive for parents to bias the investment in offspring in relation to sex. Recently developed molecular techniques that allow sex determination of newly hatched offspring have caused a surge in studies of avian sex allocation. Whether females bias the primary brood sex ratio in relation to factors such as environmental and parental quality is debated. Progress is hampered because the mechanisms for primary sex ratio manipulation are unknown. Moreover, publication bias against non-significant results may distort our view of adaptive sex ratio manipulation. Despite this, there is recent experimental evidence for adaptive brood sex ratio manipulation in birds. Parental care is a particularly likely candidate to affect the brood sex ratio because it can have strong direct effects on the fitness of both parents and their offspring. We investigate and make predictions of factors that can be important for adaptive brood sex ratio manipulation under different patterns of parental care. We encourage correlational studies based on sufficiently large datasets to ensure high statistical power, studies identifying and experimentally altering factors with sex-differential fitness effects that may cause brood sex ratio skew, and studies that experimentally manipulate brood sex ratio and investigate fitness effects. PMID:11958704

  6. Partnership status and the human sex ratio at birth.

    PubMed

    Norberg, Karen

    2004-11-22

    If two-parent care has different consequences for the reproductive success of sons and daughters, then natural selection may favour adjustment of the sex ratio at birth according to circumstances that forecast later family structure. In humans, this partnership-status hypothesis predicts fewer sons among extra-pair conceptions, but the rival 'attractiveness' hypothesis predicts more sons among extra-pair conceptions, and the 'fixed-phenotype' hypothesis predicts a constant probability of having a son, regardless of partnership status. In a sample of 86 436 human births pooled from five US population-based surveys, I found 51.5% male births reported by respondents who were living with a spouse or partner before the child's conception or birth, and 49.9% male births reported by respondents who were not (chi(2)=16.77 d.f.=1 p<0.0001). The effect was not explained by paternal bias against daughters, by parental age, education, income, ethnicity or by year of observation, and was larger when comparisons were made between siblings. To my knowledge, this is the first direct evidence for conditional adjustment of the sex ratio at birth in humans, and could explain the recent decline in the sex ratio at birth in some developed countries.

  7. Effect of the Lebanese civil war on sex ratio.

    PubMed

    Abu-Musa, Antoine; Usta, Ihab; Hannoun, Antoine; Nassar, Anwar

    2008-01-01

    Sex ratio is a subject of scientific interest but little is known about the factors that affect the sex ratio of humans. The aim of this study was to assess the effect of the Lebanese civil war on sex ratio. Data on all live births delivered at a large university hospital for the years 1977-2005 were used in this study. Study periods were defined as wartime (1977-1992) and post-war (1993-2005). The sex ratio in the study time period was calculated as the male proportion, i.e. males/males + females in live-born infants. Sex ratio during the war was compared with that of the post-war period. The sex ratio was similar in the war and post-war period (0.515 versus 0.513; OR = 1.007; 95% CI 0.98-1.04). The annual variation in the sex ratio during the study period did not show any significant change in any of the years. In conclusion, the Lebanese civil war did not cause a detectable change in sex ratio at birth. Factors that might have affected the sex ratio include the nature of the study population (civilians), the variable intensity of war in different periods, and the effect of stress and environmental toxins.

  8. Secular trends and geographical variations in sex ratio at birth.

    PubMed

    Pavic, Dario

    2015-12-01

    Numerous studies have established the presence of secular trends and geographical variations in sex ratio at birth, albeit with mixed and often contradictory results. In addition, a multitude of environmental, social, economic, demographic and other factors has been proposed to influence the sex ratio at birth, thus complicating the interpretation of both secular trends and geographical variations. In this paper, the current state of knowledge on these issues is presented and critically assessed. Analyzing longer time series of sex ratio at birth with possible cycles and random components is given priority over establishing simple linear trends in the data. In analyzing the geographical variation in the sex ratio at birth, two different levels of analysis are distinguished (global and local), and two different sets of factors affecting the sex ratio at birth are proposed accordingly. Some key guidelines and future research directions are also proposed.

  9. Sex ratio dynamics and fluctuating selection on personality.

    PubMed

    Del Giudice, Marco

    2012-03-21

    Fluctuating selection has often been proposed as an explanation for the maintenance of genetic variation in personality. Here I argue that the temporal dynamics of the sex ratio can be a powerful source of fluctuating selection on personality traits, and develop this hypothesis with respect to humans. First, I review evidence that sex ratios modulate a wide range of social processes related to mating and parenting. Since most personality traits affect mating and parenting behavior, changes in the sex ratio can be expected to result in variable selection on personality. I then show that the temporal dynamics of the sex ratio are intrinsically characterized by fluctuations at various timescales. Finally, I address a number of evolutionary genetic challenges to the hypothesis. I conclude that the sex ratio hypothesis is a plausible explanation of genetic variation in human personality, and may be fruitfully applied to other species as well.

  10. Effect of timing of artificial insemination on sex ratio.

    PubMed

    Rorie, R W

    1999-12-01

    For a number of years, the time of insemination or mating during estrus has been believed to influence the sex ratio of offspring, with early insemination resulting in more females and late insemination, more males. Possible mechanisms of altering the sex ratio include facilitating or inhibiting the transport of either X- or Y-chromosome-bearing sperm through the reproductive tract, preferential selection of sperm at fertilization, or sex-specific death of embryos after fertilization. In livestock species, there is evidence for preferential selection of X- or Y-bearing sperm, based on the maturational state of the oocyte at fertilization. In deer and sheep, early and late insemination appears to skew the sex ratio toward females and males, respectively. In cattle, conflicting reports on the effect of time of insemination on sex ratio make the premise less clear. Many of the published studies lack adequate observations for definitive conclusions and/or are based on infrequent observations of estrus, making it difficult to assess the effect of time of insemination on sex ratio. It is likely that any effect of time of insemination on sex ratio in cattle is relatively small. Evidence is accumulating that treatments used for synchronization of estrus or ovulation in cattle may influence the sex ratio.

  11. A statistical analysis of the effect of warfare on the human secondary sex ratio.

    PubMed

    Graffelman, J; Hoekstra, R F

    2000-06-01

    Many factors have been hypothesized to affect the human secondary sex ratio (the annual percentage of males among all live births), among them race, parental ages, and birth order. Some authors have even proposed warfare as a factor influencing live birth sex ratios. The hypothesis that during and shortly after periods of war the human secondary sex ratio is higher has received little statistical treatment. In this paper we evaluate the war hypothesis using 3 statistical methods: linear regression, randomization, and time-series analysis. Live birth data from 10 different countries were included. Although we cannot speak of a general phenomenon, statistical evidence for an association between warfare and live birth sex ratio was found for several countries. Regression and randomization test results were in agreement. Time-series analysis showed that most human sex-ratio time series can be described by a common model. The results obtained using intervention models differed somewhat from results obtained by regression methods.

  12. Exploring racial variations in the spousal sex ratio of killing.

    PubMed

    Regoeczi, W C

    2001-12-01

    The following article examines differences in the social situation of intimate partners as an explanation of racial differences in the female to male ratio of spousal homicides in Canada. An analysis of homicide data from 1961 to 1983 generated by the Canadian Centre for Justice Statistics reveals that the ratio of women killing their husbands to men killing their wives is highest for Aboriginals and lowest for Blacks, with the ratio for Whites falling in between. The possible sources of racial differences in this ratio include the proportion of couples (a) in common-law relationships, (b) who are co-residing as opposed to being separated, and (c) for whom there is a substantial age disparity between the partners. These factors are related to the spousal sex ratio of killing more generally. An exploration of interracial homicide patterns and racial variation in jealousy-motivated homicides was also undertaken. The findings reveal that controlling for the above factors substantially reduces the importance of race in predicting the gender of the homicide victim.

  13. Population abundance and sex ratio in dioecious helminth parasites.

    PubMed

    Poulin, Robert

    1997-07-01

    Parasite populations are highly fragmented in space and time, and consist of aggregates of genetically similar individuals sharing the same host. To avoid inbreeding, theory predicts that female-biased sex ratios should be strongly favoured when either or both prevalence and intensity of infection are low. Other models indicate that if sex ratios are selected to increase the probability of mating, they should be less biased at a high intensity of infection in polygamous parasites, since at high intensities all females are mated. To test these predictions, the relationship between sex ratio and both the prevalence and intensity of infection was examined in comparative studies across 193 populations of nematode and acanthocephalan parasites. Sex ratios in these two dioecious, polygamous taxa are usually female biased. Among natural populations, no significant relationship was observed once the confounding effects of phylogeny had been removed. However, among experimental populations of nematodes, a negative relationship was found between intensity of infection and sex ratio, even after controlling for phylogeny. In other words, at high intensities, populations of nematodes are less female biased. This result must be treated with caution because of the unusually high numbers of worms per host in experimental infections. Nevertheless, combined with information on the proximate mechanisms regulating sex ratios in these parasites, it suggests a link between the characteristics of parasite populations and their sex ratio.

  14. Patterns of Family Formation in Response to Sex Ratio Variation

    PubMed Central

    Schacht, Ryan; Kramer, Karen L.

    2016-01-01

    The impact that unbalanced sex ratios have on health and societal outcomes is of mounting contemporary concern. However, it is increasingly unclear whether it is male- or female-biased sex ratios that are associated with family and social instability. From a socio-demographic perspective, male-biased sex ratios leave many men unable to find a mate, elevating competition among males, disrupting family formation and negatively affecting social stability. In contrast, from a mating-market perspective, males are expected to be less willing to marry and commit to a family when the sex ratio is female-biased and males are rare. Here we use U.S. data to evaluate predictions from these competing frameworks by testing the relationship between the adult sex ratio and measures of family formation. We find that when women are rare men are more likely to marry, be part of a family and be sexually committed to a single partner. Our results do not support claims that male-biased sex ratios lead to negative family outcomes due to a surplus of unmarried men. Rather, our results highlight the need to pay increased attention to female-biased sex ratios. PMID:27556401

  15. Nestling sex ratios in the southwestern willow flycatcher

    USGS Publications Warehouse

    Paxton, E.H.; Sogge, M.K.; McCarthey, Tracy; Keim, Paul

    2002-01-01

    Using molecular-genetic techniques, we determined the gender of 202 Southwestern Willow Flycatcher (Empidonax traillii extimus) nestlings from 95 nests sampled over a five-year period. Overall nestling sex ratio did not vary significantly from 50:50 among years, by clutch order, or by mating strategy (monogamous vs. polygamous pairings). However, we did observe significant differences among the four sites sampled, with sex ratios biased either toward males or females at the different sites. Given the small population sizes and geographic isolation of many of the endangered subspecies' breeding populations, sex-ratio differences may have localized negative impacts.

  16. Nestling sex ratio in the Southwestern Willow Flycatcher

    USGS Publications Warehouse

    Paxton, E.H.; Sogge, M.K.; McCarthey, T.D.; Keim, P.

    2002-01-01

    Using molecular-genetic techniques, we determined the gender of 202 Southwestern Willow Flycatcher (Empidonax traillii extimus) nestlings from 95 nests sampled over a five-year period. Overall nestling sex ratio did not vary significantly from 50:50 among years, by clutch order, or by mating strategy (monogamous vs. polygamous pairings). However, we did observe significant differences among the four sites sampled, with sex ratios biased either toward males or females at the different sites. Given the small population sizes and geographic isolation of many of the endangered subspecies' breeding populations, sex-ratio differences may have localized negative impacts. ?? The Cooper Ornithological Society 2002.

  17. Sex-different response in growth traits to resource heterogeneity explains male-biased sex ratio

    NASA Astrophysics Data System (ADS)

    Matsushita, Michinari; Takao, Mikako; Makita, Akifumi

    2016-08-01

    In dioecious plants, differences in growth traits between sexes in a response to micro-environmental heterogeneity may affect sex ratio bias and spatial distributions. Here, we examined sex ratios, stem growth traits and spatial distribution patterns in the dioecious clonal shrub Aucuba japonica var. borealis, in stands with varying light intensities. We found that male stems were significantly more decumbent (lower height/length ratio) but female stems were upright (higher height/length ratio). Moreover, we found sex-different response in stem density (no. of stems per unit area) along a light intensity gradient; in males the stem density increased with increases in canopy openness, but not in females. The higher sensitivity of males in increasing stem density to light intensity correlated with male-biased sex ratio; fine-scale sex ratio was strongly male-biased as canopy openness increased. There were also differences between sexes in spatial distributions of stems. Spatial segregation of sexes and male patches occupying larger areas than female patches might result from vigorous growth of males under well-lit environments. In summary, females and males showed different growth responses to environmental variation, and this seemed to be one of possible causes for the sex-differential spatial distributions and locally biased sex ratios.

  18. Hormonal and behavioral determinants of the secondary sex ratio.

    PubMed

    Martin, J F

    1995-01-01

    The timing of insemination relative to ovulation and the frequency of insemination appear prominently in analyses of variations in human secondary sex ratios. Explanations invoking these variables are shown to be inadequate. A new synthetic model of sex determination is proposed in which the sex of offspring is powerfully determined by the state of the cervical mucus. The cervical state is then shown to be a function of hormonal factors endogenous to the female in interaction with the effects of previous inseminations.

  19. Control of mammalian sex ratio by sexing sperm

    SciTech Connect

    Gledhill, B.L.

    1983-11-01

    Preselection of sex is discussed with emphasis on methods which have claimed success in separating X- and Y-chromosome-bearing sperm. Much of the recent experimental work in separating human X and Y sperm judges the success of enrichment solely by staining for the Y sperm with a quinacrine dye, which causes a bright fluorescence of the long arm of the Y chromosome. This method is questioned because the endpoint may be producing spurious results. Flow sorting is believed to be the first verified separation of mammalian sperm, but the sperm were nonviable. Flow cytometry can be used to quickly determine the success of other enrichment techniques. Bulk separation, as contrasted to separation based on determination of individual sperm characteristics, with 80% enrichment seems to be a reasonable future goal.

  20. Secular trends in newborn sex ratios.

    PubMed

    Grech, Victor

    2014-11-01

    A wide variety of factors have been shown to influence the male to female ratio at birth, which invariably displays a male excess. This paper will review and amplify recent work by the author, with specific references to individual countries, regions and entire continents in order to provide a global overview of this subject. It will be shown that stress, including stress related to political events, influences this ratio. Man-made radiation is also shown to have played a significant role in relation to the Windscale fire (1957) and Chernobyl (1986).

  1. Breeding Sex Ratios in Adult Leatherback Turtles (Dermochelys coriacea) May Compensate for Female-Biased Hatchling Sex Ratios

    PubMed Central

    Stewart, Kelly R.; Dutton, Peter H.

    2014-01-01

    For vertebrates with temperature-dependent sex determination, primary (or hatchling) sex ratios are often skewed, an issue of particular relevance to concerns over effects of climate change on populations. However, the ratio of breeding males to females, or the operational sex ratio (OSR), is important to understand because it has consequences for population demographics and determines the capacity of a species to persist. The OSR also affects mating behaviors and mate choice, depending on the more abundant sex. For sea turtles, hatchling and juvenile sex ratios are generally female-biased, and with warming nesting beach temperatures, there is concern that populations may become feminized. Our purpose was to evaluate the breeding sex ratio for leatherback turtles at a nesting beach in St. Croix, USVI. In 2010, we sampled nesting females and later sampled their hatchlings as they emerged from nests. Total genomic DNA was extracted and all individuals were genotyped using 6 polymorphic microsatellite markers. We genotyped 662 hatchlings from 58 females, matching 55 females conclusively to their nests. Of the 55, 42 females mated with one male each, 9 mated with 2 males each and 4 mated with at least 3 males each, for a multiple paternity rate of 23.6%. Using GERUD1.0, we reconstructed parental genotypes, identifying 47 different males and 46 females for an estimated breeding sex ratio of 1.02 males for every female. Thus we demonstrate that there are as many actively breeding males as females in this population. Concerns about female-biased adult sex ratios may be premature, and mate choice or competition may play more of a role in sea turtle reproduction than previously thought. We recommend monitoring breeding sex ratios in the future to allow the integration of this demographic parameter in population models. PMID:24505403

  2. Breeding sex ratios in adult leatherback turtles (Dermochelys coriacea) may compensate for female-biased hatchling sex ratios.

    PubMed

    Stewart, Kelly R; Dutton, Peter H

    2014-01-01

    For vertebrates with temperature-dependent sex determination, primary (or hatchling) sex ratios are often skewed, an issue of particular relevance to concerns over effects of climate change on populations. However, the ratio of breeding males to females, or the operational sex ratio (OSR), is important to understand because it has consequences for population demographics and determines the capacity of a species to persist. The OSR also affects mating behaviors and mate choice, depending on the more abundant sex. For sea turtles, hatchling and juvenile sex ratios are generally female-biased, and with warming nesting beach temperatures, there is concern that populations may become feminized. Our purpose was to evaluate the breeding sex ratio for leatherback turtles at a nesting beach in St. Croix, USVI. In 2010, we sampled nesting females and later sampled their hatchlings as they emerged from nests. Total genomic DNA was extracted and all individuals were genotyped using 6 polymorphic microsatellite markers. We genotyped 662 hatchlings from 58 females, matching 55 females conclusively to their nests. Of the 55, 42 females mated with one male each, 9 mated with 2 males each and 4 mated with at least 3 males each, for a multiple paternity rate of 23.6%. Using GERUD1.0, we reconstructed parental genotypes, identifying 47 different males and 46 females for an estimated breeding sex ratio of 1.02 males for every female. Thus we demonstrate that there are as many actively breeding males as females in this population. Concerns about female-biased adult sex ratios may be premature, and mate choice or competition may play more of a role in sea turtle reproduction than previously thought. We recommend monitoring breeding sex ratios in the future to allow the integration of this demographic parameter in population models.

  3. Temporal trends in the secondary sex ratio in Nordic countries.

    PubMed

    Fellman, Johan; Eriksson, Aldur W

    2011-01-01

    Attempts have been made to identify factors influencing the number of males per 100 females at birth, also called the secondary sex ratio. It has been proposed to vary inversely with the frequency of prenatal losses, but available data lend at best only weak support for this hypothesis. Statistical analyses have shown that comparisons between secondary sex ratios demand large data sets. Variations in the secondary sex ratio that have been reliably identified in family data have mostly been slight and without a notable influence on national birth registers. For Sweden, 1751-1950, the secondary sex ratio among all births and live births revealed increasing trends. The Swedish results are compared with available findings for live births in Finland, Norway, Denmark, and the small Icelandic population. For Norway and Denmark, the secondary sex ratio increased during 1801-1950. A similar, but stronger pattern was observed for Finland (1751-1950) and Iceland (1838-1950). During the latter half of the twentieth century, marked decreases were observed in all countries. Attempts to identify reliable associations between secondary sex ratios and stillbirth rates have been made, but no consistent results have emerged.

  4. Lethal combat and sex ratio evolution in a parasitoid wasp

    PubMed Central

    Innocent, Tabitha M.; Savage, Joanna; West, Stuart A.; Reece, Sarah E.

    2013-01-01

    Sex allocation theory provides excellent opportunities for testing how behavior and life histories are adjusted in response to environmental variation. One of the most successful areas from this respect is Hamilton’s local mate competition theory. As predicted by theory, a large number of animal species have been shown to adjust their offspring sex ratios (proportion male) conditionally, laying less female-biased sex ratios as the number of females that lay eggs on a patch increases. However, recent studies have shown that this predicted pattern is not followed by 2 parasitoid species in the genus Melittobia, which always produce extremely female-biased sex ratios. A possible explanation for this is that males fight fatally and that males produced by the first female to lay eggs on a patch have a competitive advantage over later emerging males. This scenario would negate the advantage of later females producing a less female-biased sex ratio. Here we examine fatal fighting and sex ratio evolution in another species, Melittobia acasta. We show that females of this species also fail to adjust their offspring sex ratio in response to the number of females laying eggs on a patch. We then show that although earlier emerging males do have an advantage in winning fights, this advantage 1) can be reduced by an interaction with body size, with larger males more likely to win fights and 2) only holds for a brief period around the time at which the younger males emerge from their pupae. This suggests that lethal male combat cannot fully explain the lack of sex ratio shift observed in Melittobia species. We discuss alternative explanations. PMID:24273326

  5. Lethal combat and sex ratio evolution in a parasitoid wasp.

    PubMed

    Innocent, Tabitha M; Savage, Joanna; West, Stuart A; Reece, Sarah E

    2007-07-01

    Sex allocation theory provides excellent opportunities for testing how behavior and life histories are adjusted in response to environmental variation. One of the most successful areas from this respect is Hamilton's local mate competition theory. As predicted by theory, a large number of animal species have been shown to adjust their offspring sex ratios (proportion male) conditionally, laying less female-biased sex ratios as the number of females that lay eggs on a patch increases. However, recent studies have shown that this predicted pattern is not followed by 2 parasitoid species in the genus Melittobia, which always produce extremely female-biased sex ratios. A possible explanation for this is that males fight fatally and that males produced by the first female to lay eggs on a patch have a competitive advantage over later emerging males. This scenario would negate the advantage of later females producing a less female-biased sex ratio. Here we examine fatal fighting and sex ratio evolution in another species, Melittobia acasta. We show that females of this species also fail to adjust their offspring sex ratio in response to the number of females laying eggs on a patch. We then show that although earlier emerging males do have an advantage in winning fights, this advantage 1) can be reduced by an interaction with body size, with larger males more likely to win fights and 2) only holds for a brief period around the time at which the younger males emerge from their pupae. This suggests that lethal male combat cannot fully explain the lack of sex ratio shift observed in Melittobia species. We discuss alternative explanations.

  6. Maternal natal environment and breeding territory predict the condition and sex ratio of offspring.

    PubMed

    Bowers, E Keith; Thompson, Charles F; Sakaluk, Scott K

    2017-03-01

    Females in a variety of taxa adjust offspring sex ratios to prevailing ecological conditions. However, little is known about whether conditions experienced during a female's early ontogeny influence the sex ratio of her offspring. We tested for past and present ecological predictors of offspring sex ratios among known-age females that were produced as offspring and bred as adults in a population of house wrens. The body condition of offspring that a female produced and the proportion of her offspring that were male were negatively correlated with the size of the brood in which she herself was reared. The proportion of sons within broods was negatively correlated with maternal hatching date, and varied positively with the quality of a female's current breeding territory as predicted. However, females producing relatively more sons than daughters were less likely to return to breed in the population the following year. Although correlative, our results suggest that the rearing environment can have enduring effects on later maternal investment and sex allocation. Moreover, the overproduction of sons relative to daughters may increase costs to a female's residual reproductive value, constraining the extent to which sons might be produced in high-quality breeding conditions. Sex allocation in birds remains a contentious subject, largely because effects on offspring sex ratios are small. Our results suggest that offspring sex ratios are shaped by various processes and trade-offs that act throughout the female life history and ultimately reduce the extent of sex-ratio adjustment relative to classic theoretical predictions.

  7. Does the Mother or Father Determine the Offspring Sex Ratio? Investigating the Relationship between Maternal Digit Ratio and Offspring Sex Ratio

    PubMed Central

    Kim, Tae Beom; Oh, Jin Kyu; Kim, Kwang Taek; Yoon, Sang Jin; Kim, Soo Woong

    2015-01-01

    Objective In mammals, high parental testosterone levels present around the time of conception are thought to skew offspring sex ratio toward sons. The second to fourth digit ratio (digit ratio) is now widely accepted as a negative correlate of prenatal testosterone. Thus, we investigated the association between digit ratio and offspring sex ratio. Methods A total of 508 Korean patients (257 males and 251 females) less than 60 years old who had one or more offspring were prospectively enrolled. The lengths of the 2nd and 4th digits of the right hand were measured by a single investigator using a digital vernier calliper. Next, the patients’ lifetime offspring birth sex ratios were investigated. Results Maternal (rather than paternal) digit ratio was significantly associated with the number of sons (r = -0.153, p = 0.015), number of daughters (r = 0.130, p = 0.039), and offspring sex ratio (r = -0.171, p = 0.007). And, the maternal digit ratio was a significant factor for predicting offspring sex ratio (B = -1.620, p = 0.008) on multiple linear regression analysis. The female patients with a lower digit ratio (< 0.95) were found to have a higher offspring sex ratio (0.609 versus 0.521, p = 0.046) compared to those with a higher digit ratio (≥ 0.95). Furthermore, females in the low digit ratio group have a probability 1.138 greater of having sons than females in the high digit ratio group. Conclusions Maternal digit ratio was negatively associated with offspring sex ratio. Females with a lower digit ratio were more likely to have more male offspring compared to those with a higher digit ratio. Thus, our results suggest that the sex of offspring might be more influenced by maternal rather than paternal factors. PMID:26575995

  8. Climate Influences Fledgling Sex Ratio and Sex-Specific Dispersal in a Seabird

    PubMed Central

    Barros, Álvaro; Álvarez, David; Velando, Alberto

    2013-01-01

    Climate influences the dynamics of natural populations by direct effects over habitat quality but also modulating the phenotypic responses of organisms’ life-history traits. These responses may be different in males and females, particularly in dimorphic species, due to sex-specific requirements or constraints. Here, in a coastal seabird, the European shag (Phalacrocorax aristotelis), we studied the influence of climate (North Atlantic Oscillation, NAO; Sea Surface Temperature, SST) on two sex-related population parameters: fledgling sex ratio and sex-specific dispersal. We found that fledgling sex ratio was female skewed in NAO-positive years and male skewed in NAO-negative years. Accordingly, females dispersed a longer distance in NAO-positive years when females were overproduced, and on the contrary, males dispersed more in NAO-negative years. Overall, our findings provide rare evidence on vertebrates with genetic sex determination that climate conditions may govern population dynamics by affecting sex-specific density and dispersal. PMID:23951144

  9. Sex choice in plants: facultative adjustment of the sex ratio in the perennial herb Begonia gracilis.

    PubMed

    López, S; Domínguez, C A

    2003-11-01

    Sex allocation theory predicts that reproducing individuals will increase their fitness by facultatively adjusting their relative investment towards the rarer sex in response to population shifts in operational sex ratio (OSR). The evolution of facultative manipulation of sex ratio depends on the ability of the parents to track the conditions favouring skewed sex allocation and on the mechanism controlling sex allocation. In animals, which have well-developed sensorial mechanisms, facultative adjustment of sex ratios has been demonstrated on many occasions. In this paper, we show that plants have mechanisms that allow them to evaluate the population OSR. We simulated three different conditions of population OSR by manipulating the amount of pollen received by the female flowers of a monoecious herb, and examined the effect of this treatment on the allocation to male vs. female flowers. A shortage of pollen on the stigmas resulted in a more male-skewed sex allocation, whereas plants that experienced a relatively pollen rich environment tended to produce a more female-skewed sex allocation pattern. Our results for Begonia gracilis demonstrate that the individuals of this species are able to respond to the levels of pollination intensity experienced by their female flowers and adjust their patterns of sex allocation in accordance to the expectations of sex allocation theory.

  10. China's marriage squeeze: A decomposition into age and sex structure.

    PubMed

    Jiang, Quanbao; Li, Xiaomin; Li, Shuzhuo; Feldman, Marcus W

    2016-06-01

    Most recent studies of marriage patterns in China have emphasized the male-biased sex ratio but have largely neglected age structure as a factor in China's male marriage squeeze. In this paper we develop an index we call "spousal sex ratio" (SSR) to measure the marriage squeeze, and a method of decomposing the proportion of male surplus into age and sex structure effects within a small spousal age difference interval. We project that China's marriage market will be confronted with a relatively severe male squeeze. For the decomposition of the cohort aged 30, from 2010 to 2020 age structure will be dominant, while from 2020 through 2034 the contribution of age structure will gradually decrease and that of sex structure will increase. From then on, sex structure will be dominant. The index and decomposition, concentrated on a specific female birth cohort, can distinguish spousal competition for single cohorts which may be covered by a summary index for the whole marriage market; these can also be used for consecutive cohorts to reflect the situation of the whole marriage market.

  11. The impact of sex ratio and economic status on local birth rates.

    PubMed

    Chipman, A; Morrison, E

    2013-04-23

    Human mating and reproductive behaviour can vary depending on various mechanisms, including the local sex ratio. Previous research shows that as sex ratios become female-biased, women from economically deprived areas are less likely to delay reproductive opportunities to wait for a high-investing mate but instead begin their reproductive careers sooner. Here, we show that the local sex ratio also has an impact on female fertility schedules. At young ages, a female-biased ratio is associated with higher birth rates in the poorest areas, whereas the opposite is true for the richest areas. At older ages, a female-biased ratio is associated with higher birth rates in the richest, but not the poorest areas. These patterns suggest that female-female competition encourages poorer women to adopt a fast life-history strategy and give birth early, and richer women to adopt a slow life-history strategy and delay reproduction.

  12. Sex without sex chromosomes: genetic architecture of multiple loci independently segregating to determine sex ratios in the copepod Tigriopus californicus.

    PubMed

    Alexander, H J; Richardson, J M L; Edmands, S; Anholt, B R

    2015-12-01

    Sex-determining systems are remarkably diverse and may evolve rapidly. Polygenic sex-determination systems are predicted to be transient and evolutionarily unstable, yet examples have been reported across a range of taxa. Here, we provide the first direct evidence of polygenic sex determination in Tigriopus californicus, a harpacticoid copepod with no heteromorphic sex chromosomes. Using genetically distinct inbred lines selected for male- and female-biased clutches, we generated a genetic map with 39 SNPs across 12 chromosomes. Quantitative trait locus mapping of sex ratio phenotype (the proportion of male offspring produced by an F2 female) in four F2 families revealed six independently segregating quantitative trait loci on five separate chromosomes, explaining 19% of the variation in sex ratios. The sex ratio phenotype varied among loci across chromosomes in both direction and magnitude, with the strongest phenotypic effects on chromosome 10 moderated to some degree by loci on four other chromosomes. For a given locus, sex ratio phenotype varied in magnitude for individuals derived from different dam lines. These data, together with the environmental factors known to contribute to sex determination, characterize the underlying complexity and potential lability of sex determination, and confirm the polygenic architecture of sex determination in T. californicus.

  13. Dynamics of sex ratio and female unmatedness under haplodiploidy.

    PubMed

    Gardner, Andy

    2014-05-01

    Haplodiploid sex determination allows unmated females to produce sons. Consequently, a scarcity of males may lead to a significant proportion of females remaining unmated, which may in turn give rise to a surfeit of males in the following generation. Stable oscillation of the sex ratio has been predicted by classic models, and it remains a puzzle as to why this is not observed in natural populations. Here, I investigate the dynamics of sex allocation over ecological and evolutionary timescales to assess the potential for sustained oscillation. I find that, whilst stable oscillation of the sex ratio is possible, the scope for such dynamical behavior is reduced if sex allocation strategies are evolutionary labile, especially if mated females may facultatively adjust their sex allocation according to the present availability of mating partners. My model, taken together with empirical estimates of female unmatedness in haplodiploid taxa, suggests that sustained oscillation of the sex ratio is implausible in natural populations. However, this phenomenon may be relevant to artificially introduced biological control agents.

  14. Age Norms: The Influence of Age, Sex, and Occupational Level.

    ERIC Educational Resources Information Center

    Zepelin, Harold; And Others

    Although informal age norms which influence the timing of major role transitions have been well documented, recent research questions the pervasiveness of this influence. In order to assess the effects of age, sex, and occupational level on perceptions of informal age norms, white-collar and blue-collar men and women (N=462) at two age levels,…

  15. Sibling sex ratio of boys with gender identity disorder.

    PubMed

    Zucker, K J; Green, R; Coates, S; Zuger, B; Cohen-Kettenis, P T; Zecca, G M; Lertora, V; Money, J; Hahn-Burke, S; Bradley, S J; Blanchard, R

    1997-07-01

    Sibling sex ratio (the ratio of brothers to sisters) was calculated for 444 boys with gender identity disorder (or with behaviors consistent with this diagnosis). The probands were ascertained from several researchers with expertise with this disorder and from the English language case report literature between 1938 and 1995. Among the probands with at least one sibling (N = 333), the results showed that boys with gender identity disorder had a significant excess of brothers to sisters, 131.1:100, when compared with the expected secondary sex ratio of 106:100. The excess of brothers replicated a previous study by Blanchard, Zucker, Bradley, and Hume (1995), in which the sibling sex ratio was 140.6:100. Further analyses showed that the probands were born later relative to their brothers than they were relative to their sisters. These findings are amenable to several psychosocial and biological explanations, which require further investigation.

  16. Effective heritability of targets of sex-ratio selection under environmental sex determination.

    PubMed

    McGaugh, S E; Janzen, F J

    2011-04-01

    Selection is expected to maintain primary sex ratios at an evolutionary equilibrium. In organisms with temperature-dependent sex determination (TSD), targets of sex-ratio selection include the thermal sensitivity of the sex-determining pathway (hereafter, sex determination threshold) and nest-site choice. However, offspring sex may be canalized for nests located in thermally extreme environments; thus, genetic variance for the sex determination threshold is not expressed and is invisible to direct selection. The concept of 'effective heritability' accounts for this dependence and provides a more realistic prediction of the expected evolutionary response to selection in the wild. Past estimates of effective heritability of the sex determination threshold, which were derived from laboratory data, suggested that the potential for the sex determination threshold to evolve in the wild was extremely low. We re-evaluated original estimates of this parameter by analysing field-collected measures of nest temperatures, vegetation cover and clutch sex ratios from nests in a population of painted turtles (Chrysemys picta). We coupled these data with measurements of broad-sense heritability of the sex determination threshold in C. picta, using an experiment that splits clutches of eggs between a constant temperature (i.e. typical laboratory incubation) and a daily fluctuating temperature (i.e. similar to natural nests) with the same mean. We found that (i) the effective heritability of the sex determination threshold appears to have been historically underestimated and the effective heritability of nest-site choice has been overestimated and (ii) significant family-by-incubation treatment interaction exists for sex for C. picta between constant- and fluctuating-temperature regimes. Our results suggest that the thermal sensitivity of the sex-determining pathway may play a larger, more complex role in the microevolution of TSD than traditionally thought.

  17. Sex ratio in silver foxes: effects of domestication and the star gene.

    PubMed

    Trut, L N

    1996-01-01

    The course of changes in secondary sex ratio (proportion of males at birth) in silver foxes bred at the fur farm of this Institute was analyzed. Data collected over several years of breeding of a domesticated (experimental) population selected for amenability to domestication and of a commercial (control) were compared. A tendency to increase in secondary sex ratio was demonstrated in both populations. However, the proportion of males at birth was higher in domestic foxes. This proportion, calculated from the combined data for 1978-1993, was 0.538±0.005 and 0.511±0.007 in the selected and commercial populations, respectively. The minimal departure of the observed sex ratio from 0.5 was demonstrated for litters with five pups, which is close to the average litter size in fox populations. The proportion of males increases with both increasing and decreasing litter size. An analysis of secondary sex ratio with respect to maternal age revealed a minimal departure of sex ratio from the expected in offspring from foxes of optimal reproductive age (2-4 years). An effect of the autosomal semidominant coat color mutation star on male excess at birth was also found: secondary sex ratio was higher (0.583±0.015) in offspring of mothers heterozygous for the star mutation than from standard types of the domesticated population. The increase in secondary sex ratio in the analyzed fox populations is viewed as a correlated response to selection for domestication. The hormonal mechanisms mediating the effects of both this selection and the star mutation on sex ratio at birth are discussed.

  18. Persistent sex-by-environment effects on offspring fitness and sex-ratio adjustment in a wild bird population

    PubMed Central

    Bowers, E. Keith; Thompson, Charles F.; Sakaluk, Scott K.

    2014-01-01

    Summary A major component of sex-allocation theory, the Trivers-Willard Model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex-by-environment effects is mixed and little is known about the adaptive significance of producing either sex. Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex-by-environment effect on offspring using two experiments, one in which we manipulated age-differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size. As predicted, females with high investment ability over-produced sons relative to those with lower ability. Males were also over-produced early within breeding seasons. In our experiments, the body mass of sons was more strongly affected by the sibling-competitive environment and resource availability than that of daughters: males grew heavier than females when reared in good conditions but were lighter than females when in poor conditions. Parents rearing broods with 1:1 sex ratios were more productive than parents rearing broods biased more strongly towards sons or daughters, suggesting that selection favours the production of mixed-sex broods. However, differences in the condition of offspring as neonates persisted to adulthood, and their reproductive success as adults varied with the body mass of sons, but not daughters, prior to independence from parental care. Thus, selection should favour slight but predictable variations in the sex ratio in relation to the quality of offspring that

  19. Age and sex selectivity in trapping mule deer

    SciTech Connect

    Garrott, R.A.; White, G.C.

    1982-01-01

    A mule deer (Odocoileus hemionus) trapping experiment is described using modified Clover traps in which changes in the placement of bait and height of the trap door modified the ratio of adult does to male and female fawns captured. The mechanisms responsible for the changes in age-sex capture ratios are discussed and indicate that modified Clover traps selectivity capture mule deer, thus introducing bias into population sampling. (JMT)

  20. Determining age and sex of American coots

    USGS Publications Warehouse

    Eddleman, William R.; Knopf, Fritz L.

    1985-01-01

    Reliable techniques for age and sex determination of migrating and wintering American Coots (Fulica americana) have not been available. Breeding coots can be ages through age 3 by tarsal color (birds 4 years and older were placed in a 4+ age class) (Crawford 1978), and males and females have sex-specific behaviors and calls while on breeding territories (Gullion 1950, 1952). Externally, juvenile coots differ from adults in having gray (as opposed to white) bills and brown (as opposed to red) eyes to an age of 75 days (Gullion 1954-394). Bill color changes to white by about 120 days. No quantitative data have been available, however, on the proportion of juveniles retaining these traits throughout fall and early winter. Nonbreeding coots can be ages as juvenile or adult by internal examination of the thickness of the wall of the bursa of Fabricius, although bursal depth does not predictably decline with age (Fredrickson 1968). Attempts to sex coots by single external measurements of combinations of measurements have met with mixed success. Eight-five percent of 101 fall migrants in Wisconsin could be sexed by the length of the metatarsus-midtoe including claw by using 139.5 mm as a cutoff point (Burton 1959), whereas 88% of 67 coots in California were correctly sexed by the length of the metatarsus-midtoe without claw using 127.5 mm as the cutoff point (Gullion 1952). Two-hundred-thirty-two of 291 coots collected in Iowa, however, were in the zone of overlap between the sexes for this measurement (Fredrickson 1968). Previous studies attempting to develop aging and sexing techniques for American Coots have been limited to a few study sites or to 1 season or year, often failing to take geographical, annual, and seasonal morphological variation into account (e.g., Visser 1976, Fjeldsa 1977). We designed the present study to refine and quantify external and internal age and sex criteria for postbreeding coots, with the objective of defining techniques applicable for all

  1. Persistent unequal sex ratio in a population of grayling (Salmonidae) and possible role of temperature increase.

    PubMed

    Wedekind, Claus; Evanno, Guillaume; Székely, Tamás; Pompini, Manuel; Darbellay, Olivier; Guthruf, Joachim

    2013-02-01

    In some fishes, water chemistry or temperature affects sex determination or creates sex-specific selection pressures. The resulting population sex ratios are hard to predict from laboratory studies if the environmental triggers interact with other factors, whereas in field studies, singular observations of unusual sex ratios may be particularly prone to selective reporting. Long-term monitoring largely avoids these problems. We studied a population of grayling (Thymallus thymallus) in Lake Thun, Switzerland, that has been monitored since 1948. Samples of spawning fish have been caught about 3 times/week around spawning season, and water temperature at the spawning site has been continuously recorded since 1970. We used scale samples collected in different years to determine the average age of spawners (for life-stage specific analyses) and to identify the cohort born in 2003 (an extraordinarily warm year). Recent tissue samples were genotyped on microsatellite markers to test for genetic bottlenecks in the past and to estimate the genetically effective population size (N(e)). Operational sex ratios changed from approximately 65% males before 1993 to approximately 85% males from 1993 to 2011. Sex ratios correlated with the water temperatures the fish experienced in their first year of life. Sex ratios were best explained by the average temperature juvenile fish experienced during their first summer. Grayling abundance is declining, but we found no evidence of a strong genetic bottleneck that would explain the apparent lack of evolutionary response to the unequal sex ratio. Results of other studies show no evidence of endocrine disruptors in the study area. Our findings suggest temperature affects population sex ratio and thereby contributes to population decline.

  2. India’s Distorted Sex Ratio: Dire Consequences for Girls

    PubMed Central

    Roberts, Lisa R.; Montgomery, Susanne B.

    2017-01-01

    Female gender discrimination related to cultural preference for males is a common global problem, especially in Asian countries. Numerous laws intended to prevent discrimination on the basis of gender have been passed in India, yet the distorted female-to-male sex ratio seems to show worsening tendencies. Using detailed, two-year longitudinal chart abstraction data about delivery records of a private mission hospital in rural India, we explored if hospital birth ratio data differed in comparison to regional data, and what demographic and contextual variables may have influenced these outcomes. Using quantitative chart abstraction and qualitative contextual data, study results showed the female-to-male ratio was lower than the reported state ratio at birth. In the context of India’s patriarchal structure, with its strong son preference, women are under tremendous pressure or coerced to access community-based, sex-selective identification and female fetus abortion. Nurses may be key to turning the tide.

  3. Effects of age and sex on olanzapine plasma concentrations.

    PubMed

    Weiss, Ulrike; Marksteiner, Josef; Kemmler, Georg; Saria, Alois; Aichhorn, Wolfgang

    2005-12-01

    Age and sex may influence both efficacy and side effects of second-generation antipsychotics. Women and elderly patients tend to have a higher prevalence for several side effects. Higher plasma levels in these groups of patients may be one reason. We studied the hypothesis that steady-state olanzapine plasma concentrations depend on age and sex. Sixty-seven inpatients on stable olanzapine dose were referred to routine therapeutic drug monitoring of olanzapine. Plasma levels were determined by high-performance liquid chromatography with electrochemical detection. Obtained data were then analyzed by analysis of covariance. Olanzapine plasma levels showed a marked sex difference with significantly higher mean concentrations in female patients (adjusted mean concentrations, 18.5 ng/mL for men and 31.7 ng/mL for women; P = 0.003). On average, the weight-corrected concentration/dose ratios shown by women were 33.5% higher than those shown by men, irrespective of age. Regarding the effect of age, weight-corrected concentration/dose ratios increased by an average of 9.4% per decade of life. All results were adjusted for smoking. Comedication did not significantly influence these results. In conclusion, age and sex are important variables to consider when prescribing olanzapine for women and in the elderly.

  4. Population density affects sex ratio variation in red deer.

    PubMed

    Kruuk, L E; Clutton-Brock, T H; Albon, S D; Pemberton, J M; Guinness, F E

    1999-06-03

    Many mammal populations show significant deviations from an equal sex ratio at birth, but these effects are notoriously inconsistent. This may be because more than one mechanism affects the sex ratio and the action of these mechanisms depends on environmental conditions. Here we show that the adaptive relationship between maternal dominance and offspring sex ratio previously demonstrated in red deer (Cervus elaphus), where dominant females produced more males, disappeared at high population density. The proportion of males born each year declined with increasing population density and with winter rainfall, both of which are environmental variables associated with nutritional stress during pregnancy. These changes in the sex ratio corresponded to reductions in fecundity, suggesting that they were caused by differential fetal loss. In contrast, the earlier association with maternal dominance is presumed to have been generated pre-implantation. The effects of one source of variation superseded the other within about two generations. Comparison with other ungulate studies indicates that positive associations between maternal quality and the proportion of male offspring born have only been documented in populations below carrying capacity.

  5. Sex ratio adjustment by sex-specific maternal cannibalism in hamsters.

    PubMed

    Beery, Annaliese K; Zucker, Irving

    2012-10-10

    Mammalian offspring sex ratios can be biased via prenatal and postnatal mechanisms, including sperm selection, sex-specific embryo loss, and differential postnatal investment in males and females. Syrian hamsters routinely cannibalize some of their pups in the first days after birth. We present evidence that short day lengths, typically predictive of poor autumn and winter field conditions, are associated with male-biased sex ratios, achieved in part through selective perinatal maternal infanticide of female offspring. Higher peak litter sizes were associated with increased cannibalism rates, decreased final litter counts, and increased body mass of pups surviving to weaning. To our knowledge this is the first report of sex ratio adjustment by offspring cannibalism.

  6. Evidence of Self-correction of Child Sex Ratios in India: A District-Level Analysis of Child Sex Ratios From 1981 to 2011.

    PubMed

    Diamond-Smith, Nadia; Bishai, David

    2015-04-01

    Sex ratios in India have become increasingly imbalanced over the past decades. We hypothesize that when sex ratios become very uneven, the shortage of girls will increase girls' future value, leading sex ratios to self-correct. Using data on children under 5 from the last four Indian censuses, we examine the relationship between the sex ratio at one point in time and the change in sex ratio over the next 10 years by district. Fixed-effects models show that when accounting for unobserved district-level characteristics--including total fertility rate, infant mortality rate, percentage literate, percentage rural, percentage scheduled caste, percentage scheduled tribe, and a time trend variable--sex ratios are significantly negatively correlated with the change in sex ratio in the successive 10-year period. This suggests that self-corrective forces are at work on imbalanced sex ratios in India.

  7. Suburbanization, estrogen contamination, and sex ratio in wild amphibian populations

    PubMed Central

    Lambert, Max R.; Giller, Geoffrey S. J.; Barber, Larry B.; Fitzgerald, Kevin C.; Skelly, David K.

    2015-01-01

    Research on endocrine disruption in frog populations, such as shifts in sex ratios and feminization of males, has predominantly focused on agricultural pesticides. Recent evidence suggests that suburban landscapes harbor amphibian populations exhibiting similar levels of endocrine disruption; however the endocrine disrupting chemical (EDC) sources are unknown. Here, we show that sex ratios of metamorphosing frogs become increasingly female-dominated along a suburbanization gradient. We further show that suburban ponds are frequently contaminated by the classical estrogen estrone and a variety of EDCs produced by plants (phytoestrogens), and that the diversity of organic EDCs is correlated with the extent of developed land use and cultivated lawn and gardens around a pond. Our work also raises the possibility that trace-element contamination associated with human land use around suburban ponds may be contributing to the estrogenic load within suburban freshwaters and constitutes another source of estrogenic exposure for wildlife. These data suggest novel, unexplored pathways of EDC contamination in human-altered environments. In particular, we propose that vegetation changes associated with suburban neighborhoods (e.g., from forests to lawns and ornamental plants) increase the distribution of phytoestrogens in surface waters. The result of frog sex ratios varying as a function of human land use implicates a role for environmental modulation of sexual differentiation in amphibians, which are assumed to only have genetic sex determination. Overall, we show that endocrine disruption is widespread in suburban frog populations and that the causes are likely diverse. PMID:26372955

  8. Suburbanization, estrogen contamination, and sex ratio in wild amphibian populations

    USGS Publications Warehouse

    Lambert, Max R.; Giller, Geoffrey S. J.; Barber, Larry B.; Fitzgerald, Kevin C.; Skelly, David K.

    2015-01-01

    Research on endocrine disruption in frog populations, such as shifts in sex ratios and feminization of males, has predominantly focused on agricultural pesticides. Recent evidence suggests that suburban landscapes harbor amphibian populations exhibiting similar levels of endocrine disruption; however the endocrine disrupting chemical (EDC) sources are unknown. Here, we show that sex ratios of metamorphosing frogs become increasingly female-dominated along a suburbanization gradient. We further show that suburban ponds are frequently contaminated by the classical estrogen estrone and a variety of EDCs produced by plants (phytoestrogens), and that the diversity of organic EDCs is correlated with the extent of developed land use and cultivated lawn and gardens around a pond. Our work also raises the possibility that trace-element contamination associated with human land use around suburban ponds may be contributing to the estrogenic load within suburban freshwaters and constitutes another source of estrogenic exposure for wildlife. These data suggest novel, unexplored pathways of EDC contamination in human-altered environments. In particular, we propose that vegetation changes associated with suburban neighborhoods (e.g., from forests to lawns and ornamental plants) increase the distribution of phytoestrogens in surface waters. The result of frog sex ratios varying as a function of human land use implicates a role for environmental modulation of sexual differentiation in amphibians, which are assumed to only have genetic sex determination. Overall, we show that endocrine disruption is widespread in suburban frog populations and that the causes are likely diverse.

  9. Suburbanization, estrogen contamination, and sex ratio in wild amphibian populations.

    PubMed

    Lambert, Max R; Giller, Geoffrey S J; Barber, Larry B; Fitzgerald, Kevin C; Skelly, David K

    2015-09-22

    Research on endocrine disruption in frog populations, such as shifts in sex ratios and feminization of males, has predominantly focused on agricultural pesticides. Recent evidence suggests that suburban landscapes harbor amphibian populations exhibiting similar levels of endocrine disruption; however the endocrine disrupting chemical (EDC) sources are unknown. Here, we show that sex ratios of metamorphosing frogs become increasingly female-dominated along a suburbanization gradient. We further show that suburban ponds are frequently contaminated by the classical estrogen estrone and a variety of EDCs produced by plants (phytoestrogens), and that the diversity of organic EDCs is correlated with the extent of developed land use and cultivated lawn and gardens around a pond. Our work also raises the possibility that trace-element contamination associated with human land use around suburban ponds may be contributing to the estrogenic load within suburban freshwaters and constitutes another source of estrogenic exposure for wildlife. These data suggest novel, unexplored pathways of EDC contamination in human-altered environments. In particular, we propose that vegetation changes associated with suburban neighborhoods (e.g., from forests to lawns and ornamental plants) increase the distribution of phytoestrogens in surface waters. The result of frog sex ratios varying as a function of human land use implicates a role for environmental modulation of sexual differentiation in amphibians, which are assumed to only have genetic sex determination. Overall, we show that endocrine disruption is widespread in suburban frog populations and that the causes are likely diverse.

  10. A predictive relationship between population and genetic sex ratios in clonal species

    NASA Astrophysics Data System (ADS)

    McLetchie, D. Nicholas; García-Ramos, Gisela

    2017-04-01

    Sexual reproduction depends on mate availability that is reflected by local sex ratios. In species where both sexes can clonally expand, the population sex ratio describes the proportion of males, including clonally derived individuals (ramets) in addition to sexually produced individuals (genets). In contrast to population sex ratio that accounts for the overall abundance of the sexes, the genetic sex ratio reflects the relative abundance of genetically unique mates, which is critical in predicting effective population size but is difficult to estimate in the field. While an intuitive positive relationship between population (ramet) sex ratio and genetic (genet) sex ratio is expected, an explicit relationship is unknown. In this study, we determined a mathematical expression in the form of a hyperbola that encompasses a linear to a nonlinear positive relationship between ramet and genet sex ratios. As expected when both sexes clonally have equal number of ramets per genet both sex ratios are identical, and thus ramet sex ratio becomes a linear function of genet sex ratio. Conversely, if sex differences in ramet number occur, this mathematical relationship becomes nonlinear and a discrepancy between the sex ratios amplifies from extreme sex ratios values towards intermediate values. We evaluated our predictions with empirical data that simultaneously quantified ramet and genet sex ratios in populations of several species. We found that the data support the predicted positive nonlinear relationship, indicating sex differences in ramet number across populations. However, some data may also fit the null model, which suggests that sex differences in ramet number were not extensive, or the number of populations was too small to capture the curvature of the nonlinear relationship. Data with lack of fit suggest the presence of factors capable of weakening the positive relationship between the sex ratios. Advantages of this model include predicting genet sex ratio using

  11. Sex Ratios, Economic Power, and Women's Roles: A Theoretical Extension and Empirical Test.

    ERIC Educational Resources Information Center

    South, Scott J.

    1988-01-01

    Tested hypotheses concerning sex ratios, women's roles, and economic power with data from 111 countries. Found undersupply of women positively associated with proportion of women who marry and fertility rate; inversely associated with women's average age at marriage, literacy rate, and divorce rate. Suggests women's economic power may counteract…

  12. Mallard age and sex determination from wings

    USGS Publications Warehouse

    Carney, S.M.; Geis, A.D.

    1960-01-01

    This paper describes characters on the wing plumage of the mallard that indicate age and sex. A key outlines a logical order in which to check age and sex characters on wings. This method was tested and found to be more than 95 percent reliable, although it was found that considerable practice and training with known-age specimens was required to achieve this level of accuracy....The implications of this technique and the sampling procedure it permits are discussed. Wing collections could provide information on production, and, if coupled with a banding program could permit seasonal population estimates to be calculated. In addition, representative samples of wings would provide data to check the reliability of several other waterfowl surveys.

  13. Comparison between primary sex ratio in spermatozoa of bulls and secondary sex ratio in the deriving offspring.

    PubMed

    Amadesi, A; Frana, A; Gandini, L M; Bornaghi, V; Parati, K; Bongioni, G; Puglisi, R; Galli, A

    2015-01-15

    The objectives of the present work were to compare the primary sex ratio in sperm with the secondary sex ratio recorded in the offspring produced by artificial insemination (AI) with the same sperm and assess whether the primary sex ratio is influenced by sperm survival and motility after thawing. Calving data of 98 Holstein Friesian bulls used in AI were collected during 4 years, and commercial semen of the same bulls was analyzed immediately after thawing and after swim-up using a real-time polymerase chain reaction method developed and validated in our laboratory. Calving data relative to single bulls did not reveal any significant deviation between genders from the theoretical 1:1 for none of the bulls, being the mean values of male and female calves born 52.1 ± 2.80% and 47.9 ± 2.71%, respectively. Thereafter, calving events of bulls were classified and analyzed according to four classes of years: 2009 (n = 13,261), 2010 (n = 21,551), 2011 (n = 24,218), and 2012 (n = 41,726), and seasons categorized as winter, spring, summer, and fall. When data aggregated per years were analyzed, the difference between the two sexes was significant (P < 0.005) in favor of the male gender, whereas no influence of the season was evidenced. Real-time polymerase chain reaction did not evidence any difference between the mean values of frequency of Y chromosome-bearing sperm detected in three sperm batches of the same bulls analyzed immediately after thawing (51.1 ± 2.1), nor a difference with respect to the theoretical 1:1 ratio was reported after sperm analysis of one batch of sperm of the bulls analyzed after swim-up and immediately after thawing (50.1 ± 2.1 and 49.8 ± 1.8, respectively). The results are consistent with the observation of the farmers who often report a skewed sex ratio of the calves being born with AI in favor of the male gender. However, we have not evidenced differences in the primary sex ratio with respect to the theoretical 1:1 ratio both at thawing

  14. SEX-RATIO MEIOTIC DRIVE AND INTERSPECIFIC COMPETITION

    PubMed Central

    Unckless, Robert L.; Clark, Andrew G.

    2014-01-01

    It has long been known that processes occurring within a species may impact the interactions between species. For example, since competitive ability is sensitive to parameters including reproductive rate, carrying capacity and competition efficiency, the outcome of interspecific competition may be influenced by any process that alters these attributes. While several such scenarios have been discussed, the influence of selfish genetic elements within one species on competition between species has not received theoretical treatment. We show that, with strong competition, sex-ratio meiotic drive systems can result in a significant shift in community composition because the effective birth rate in the population may be increased by a female-biased sex-ratio. Using empirical data we attempt to estimate the magnitude of this effect in several Drosophila species. We infer that meiotic drive elements, selfish genetic elements within species, can provide a substantial competitive advantage to that species within a community. PMID:24835887

  15. Population sex ratios: another consideration in the reintroduction - reinforcement debate?

    PubMed

    Lambertucci, Sergio A; Carrete, Martina; Speziale, Karina L; Hiraldo, Fernando; Donázar, José Antonio

    2013-01-01

    Reintroduction or reinforcement (RorR) of wild populations is a common conservation strategy. Many conservation projects involve the release of individuals of poorly studied species. This may lead to inefficient results or negative impacts on the conservation efforts. Here, we provide new insights into the conservation implications and potential consequences of a skew in the sex ratio of released birds and of the number of birds supplemented for the demography of a long-lived dimorphic bird species, the Andean condor (Vulturgryphus). We demonstrate that a RorR conservation program may be less effective in conserving a species if the sex ratios of the releases and the recipient populations are not considered. We also show that releases can reduce population declines but only if carried out over long periods (i.e., several decades). This can mean high costs for release programs and the added challenge of maintaining programs over time. If RorR programs are to be implemented, bearing in mind the importance of properly assessing their effectiveness, we urge conservation researchers and managers to consider the implications of sex ratio biases for wild populations, and particularly for dimorphic species with sexually despotic behaviour.

  16. Mating behavior, population growth, and the operational sex ratio: a periodic two-sex model approach.

    PubMed

    Jenouvrier, Stéphanie; Caswell, Hal; Barbraud, Christophe; Weimerskirch, Henri

    2010-06-01

    We present a new approach to modeling two-sex populations, using periodic, nonlinear two-sex matrix models. The models project the population growth rate, the population structure, and any ratio of interest (e.g., operational sex ratio). The periodic formulation permits inclusion of highly seasonal behavioral events. A periodic product of the seasonal matrices describes annual population dynamics. The model is nonlinear because mating probability depends on the structure of the population. To study how the vital rates influence population growth rate, population structure, and operational sex ratio, we used sensitivity analysis of frequency-dependent nonlinear models. In nonlinear two-sex models the vital rates affect growth rate directly and also indirectly through effects on the population structure. The indirect effects can sometimes overwhelm the direct effects and are revealed only by nonlinear analysis. We find that the sensitivity of the population growth rate to female survival is negative for the emperor penguin, a species with highly seasonal breeding behavior. This result could not occur in linear models because changes in population structure have no effect on per capita reproduction. Our approach is applicable to ecological and evolutionary studies of any species in which males and females interact in a seasonal environment.

  17. Woodcock age and sex determination from wings

    USGS Publications Warehouse

    Martin, F.W.

    1964-01-01

    Age of woodcock (Philohela minor) can be accurately determined throughout the year by differences in pattern, color, and wear of secondary feathers. Immature woodcock retain most secondaries during the postjuvenal molt that begins in July or August and ends in October. In contrast, subadults (first-year adults) and older woodcock molt all secondaries during the postnuptial molt beginning in June or July and ending in October. Retention of juvenal secondaries by immatures and molt of these feathers by adults form the basis for age determination. Sex of woodcock can be accurately determined by width of the outer three primaries, which are conspicuously narrower on males.

  18. Sex ratio strategies and the evolution of cue use.

    PubMed

    Moore, Jamie C; Zavodna, Monika; Compton, Stephen G; Gilmartin, Philip M

    2005-06-22

    Quantitative tests of sex allocation theory have often indicated that organism strategies deviate from model predictions. In pollinating fig wasps, Lipporrhopalum tentacularis, whole fig (brood) sex ratios are generally more female-biased than predicted by local mate competition (LMC) theory where females (foundresses) use density as a cue to assess potential LMC. We use microsatellite markers to investigate foundress sex ratios in L. tentacularis and show that they actually use their clutch size as a cue, with strategies closely approximating the predictions of a new model we develop of these conditions. We then provide evidence that the use of clutch size as a cue is common among species experiencing LMC, and given the other predictions of our model argue that this is because their ecologies mean it provides sufficiently accurate information about potential LMC that the use of other more costly cues has not evolved. We further argue that the use of these more costly cues by other species is due to the effect that ecological differences have on cue accuracy. This implies that deviations from earlier theoretical predictions often indicate that the cues used to assess environmental conditions differ from those assumed by models, rather than limits on the ability of natural selection to produce "perfect" organisms.

  19. Sex ratio strategies and the evolution of cue use

    PubMed Central

    Moore, Jamie C; Zavodna, Monika; Compton, Stephen G; Gilmartin, Philip M

    2005-01-01

    Quantitative tests of sex allocation theory have often indicated that organism strategies deviate from model predictions. In pollinating fig wasps, Lipporrhopalum tentacularis, whole fig (brood) sex ratios are generally more female-biased than predicted by local mate competition (LMC) theory where females (foundresses) use density as a cue to assess potential LMC. We use microsatellite markers to investigate foundress sex ratios in L. tentacularis and show that they actually use their clutch size as a cue, with strategies closely approximating the predictions of a new model we develop of these conditions. We then provide evidence that the use of clutch size as a cue is common among species experiencing LMC, and given the other predictions of our model argue that this is because their ecologies mean it provides sufficiently accurate information about potential LMC that the use of other more costly cues has not evolved. We further argue that the use of these more costly cues by other species is due to the effect that ecological differences have on cue accuracy. This implies that deviations from earlier theoretical predictions often indicate that the cues used to assess environmental conditions differ from those assumed by models, rather than limits on the ability of natural selection to produce ‘perfect’ organisms. PMID:16024394

  20. Genetic architecture of sex determination in fish: applications to sex ratio control in aquaculture

    PubMed Central

    Martínez, Paulino; Viñas, Ana M.; Sánchez, Laura; Díaz, Noelia; Ribas, Laia; Piferrer, Francesc

    2014-01-01

    Controlling the sex ratio is essential in finfish farming. A balanced sex ratio is usually good for broodstock management, since it enables to develop appropriate breeding schemes. However, in some species the production of monosex populations is desirable because the existence of sexual dimorphism, primarily in growth or first time of sexual maturation, but also in color or shape, can render one sex more valuable. The knowledge of the genetic architecture of sex determination (SD) is convenient for controlling sex ratio and for the implementation of breeding programs. Unlike mammals and birds, which show highly conserved master genes that control a conserved genetic network responsible for gonad differentiation (GD), a huge diversity of SD mechanisms has been reported in fish. Despite theory predictions, more than one gene is in many cases involved in fish SD and genetic differences have been observed in the GD network. Environmental factors also play a relevant role and epigenetic mechanisms are becoming increasingly recognized for the establishment and maintenance of the GD pathways. Although major genetic factors are frequently involved in fish SD, these observations strongly suggest that SD in this group resembles a complex trait. Accordingly, the application of quantitative genetics combined with genomic tools is desirable to address its study and in fact, when applied, it has frequently demonstrated a multigene trait interacting with environmental factors in model and cultured fish species. This scenario has notable implications for aquaculture and, depending upon the species, from chromosome manipulation or environmental control techniques up to classical selection or marker assisted selection programs, are being applied. In this review, we selected four relevant species or fish groups to illustrate this diversity and hence the technologies that can be used by the industry for the control of sex ratio: turbot and European sea bass, two reference species of

  1. Genetic architecture of sex determination in fish: applications to sex ratio control in aquaculture.

    PubMed

    Martínez, Paulino; Viñas, Ana M; Sánchez, Laura; Díaz, Noelia; Ribas, Laia; Piferrer, Francesc

    2014-01-01

    Controlling the sex ratio is essential in finfish farming. A balanced sex ratio is usually good for broodstock management, since it enables to develop appropriate breeding schemes. However, in some species the production of monosex populations is desirable because the existence of sexual dimorphism, primarily in growth or first time of sexual maturation, but also in color or shape, can render one sex more valuable. The knowledge of the genetic architecture of sex determination (SD) is convenient for controlling sex ratio and for the implementation of breeding programs. Unlike mammals and birds, which show highly conserved master genes that control a conserved genetic network responsible for gonad differentiation (GD), a huge diversity of SD mechanisms has been reported in fish. Despite theory predictions, more than one gene is in many cases involved in fish SD and genetic differences have been observed in the GD network. Environmental factors also play a relevant role and epigenetic mechanisms are becoming increasingly recognized for the establishment and maintenance of the GD pathways. Although major genetic factors are frequently involved in fish SD, these observations strongly suggest that SD in this group resembles a complex trait. Accordingly, the application of quantitative genetics combined with genomic tools is desirable to address its study and in fact, when applied, it has frequently demonstrated a multigene trait interacting with environmental factors in model and cultured fish species. This scenario has notable implications for aquaculture and, depending upon the species, from chromosome manipulation or environmental control techniques up to classical selection or marker assisted selection programs, are being applied. In this review, we selected four relevant species or fish groups to illustrate this diversity and hence the technologies that can be used by the industry for the control of sex ratio: turbot and European sea bass, two reference species of

  2. Identifying sex and age of akiapolaau

    USGS Publications Warehouse

    Pratt, T.K.; Fancy, S.G.; Harada, C.K.; Lindsey, G.D.; Jacobi, J.D.

    1994-01-01

    Methods for identifying the sex and age of the Akiapolaau (Hemignathus munroi), an endangered honeycreeper found only on the island of Hawaii, were developed by examination and measurement of 73 museum specimens and 24 live birds captured in mist nests. Akiapolaau probably undergo a single annual molt, with most birds molting between February and July. The mottled juvenal plumage is replaced by a first basic plumage characterized by yellowish-gray or yellowish-green underparts and often by retained wingbars. Male Akiapolaau may not attain adult plumage until their third molt. In adult females, only the throat and upper breast become yellow, whereas in adult males the superciliaries, cheeks, and entire underparts are yellow. Adult males have greater exposed culmen, gonys, wing chord, tail, and tarsus lengths than do females. Akiapolaau in first prebasic molt or older can be identified as to sex by culmen length, that of males being >23.4 mm.

  3. Age and sex identification of Akohekohe

    USGS Publications Warehouse

    Simon, John C.; Pratt, T.K.; Berlin, Kim E.; Kowalsky, James R.

    1998-01-01

    We present methods to determine the age and sex of Akohekohe (Palmeria dolei), an endangered Hawaiian honeycreeper, developed on the basis of 45 museum specimens and 91 live birds captured on the island of Maui. Akohekohe retained all Juvenal primaries, some Juvenal secondaries, and some body feathers after the first prebasic molt; they attained full adult plumage after the second prebasic molt. Retention of brown Juvenal body feathers, especially on the head, distinguished most birds in the first basic plumage from adults, which have a full complement of distinctive, black lanceolate body feathers with white, gray, or orange tips. Male Akohekohe were heavier than females and had longer wing, tail, and tarsometatarsus lengths. We present a linear discriminant function to sex both adults and juveniles using lengths of their wing and tarsometatarsus.

  4. Bare market: campus sex ratios, romantic relationships, and sexual behavior.

    PubMed

    Uecker, Jeremy E; Regnerus, Mark D

    2010-01-01

    Using a nationally representative sample of college women, we evaluate the effect of campus sex ratios on women's relationship attitudes and behaviors. Our results suggest that women on campuses where they comprise a higher proportion of the student body give more negative appraisals of campus men and relationships, go on fewer traditional dates, are less likely to have had a college boyfriend, and are more likely to be sexually active. These effects appear to stem both from decreased dyadic power among women on campuses where they are more numerous and from their increased difficulty locating a partner on such campuses.

  5. Sex and age identification of palila

    USGS Publications Warehouse

    Jeffrey, J.J.; Fancy, S.G.; Lindsey, G.D.; Banko, P.C.; Pratt, T.K.; Jacobi, J.D.

    1993-01-01

    Methods to sex and age Palila (Loxioides bailleui), an endangered Hawaiian finch restricted to subalpine woodlands on Hawai'i, were identified on the basis of measurements and plumage characteristics of 17 museum specimens and 96 known-age, live Palila. Palila undergo a single annual molt during September-December following the breeding season. Presence of a complete or partial wingbar distinguishes hatch-year and second-year Palila from after-second-year birds. Adult male Palila are distinguished from females by a distinct napeline and lt 30% gray feathers intermixed with yellow feathers on the head. The black or gray feathers of the lores and chin of males are darker than those on the back, whereas the lores and chin of females are lighter or of the same shade as back feathers.

  6. Sex allocation and secondary sex ratio in Cuban boa (Chilabothrus angulifer): mother's body size affects the ratio between sons and daughters.

    PubMed

    Frynta, Daniel; Vejvodová, Tereza; Šimková, Olga

    2016-06-01

    Secondary sex ratios of animals with genetically determined sex may considerably deviate from equality. These deviations may be attributed to several proximate and ultimate factors. Sex ratio theory explains some of them as strategic decisions of mothers improving their fitness by selective investment in sons or daughters, e.g. local resource competition hypothesis (LRC) suggests that philopatric females tend to produce litters with male-biased sex ratios to avoid future competition with their daughters. Until now, only little attention has been paid to examine predictions of sex ratio theory in snakes possessing genetic sex determination and exhibiting large variance in allocation of maternal investment. Cuban boa is an endemic viviparous snake producing large-bodied newborns (∼200 g). Extremely high maternal investment in each offspring increases importance of sex allocation. In a captive colony, we collected breeding records of 42 mothers, 62 litters and 306 newborns and examined secondary sex ratios (SR) and sexual size dimorphism (SSD) of newborns. None of the examined morphometric traits of neonates appeared sexually dimorphic. The sex ratio was slightly male biased (174 males versus 132 females) and litter sex ratio significantly decreased with female snout-vent length. We interpret this relationship as an additional support for LRC as competition between mothers and daughters increases with similarity of body sizes between competing snakes.

  7. Sex allocation and secondary sex ratio in Cuban boa ( Chilabothrus angulifer): mother's body size affects the ratio between sons and daughters

    NASA Astrophysics Data System (ADS)

    Frynta, Daniel; Vejvodová, Tereza; Šimková, Olga

    2016-06-01

    Secondary sex ratios of animals with genetically determined sex may considerably deviate from equality. These deviations may be attributed to several proximate and ultimate factors. Sex ratio theory explains some of them as strategic decisions of mothers improving their fitness by selective investment in sons or daughters, e.g. local resource competition hypothesis (LRC) suggests that philopatric females tend to produce litters with male-biased sex ratios to avoid future competition with their daughters. Until now, only little attention has been paid to examine predictions of sex ratio theory in snakes possessing genetic sex determination and exhibiting large variance in allocation of maternal investment. Cuban boa is an endemic viviparous snake producing large-bodied newborns (˜200 g). Extremely high maternal investment in each offspring increases importance of sex allocation. In a captive colony, we collected breeding records of 42 mothers, 62 litters and 306 newborns and examined secondary sex ratios (SR) and sexual size dimorphism (SSD) of newborns. None of the examined morphometric traits of neonates appeared sexually dimorphic. The sex ratio was slightly male biased (174 males versus 132 females) and litter sex ratio significantly decreased with female snout-vent length. We interpret this relationship as an additional support for LRC as competition between mothers and daughters increases with similarity of body sizes between competing snakes.

  8. Association of Educational Level and Child Sex Ratio in Rural and Urban India

    ERIC Educational Resources Information Center

    Inchani, Lisa R.; Lai, Dejian

    2008-01-01

    Utilizing data from the Census of India, this study compared child sex ratio in rural and urban regions of India and analyzed whether the child sex ratio was associated with mother's education level. The child sex ratios in the rural and urban regions throughout India were analyzed using the two-sample and paired Student's t-test. Further, the…

  9. Population structure and the evolution of sexual size dimorphism and sex ratios in an insular population of Florida box turtles (Terrapene carolina bauri)

    USGS Publications Warehouse

    Dodd, C.K.

    1997-01-01

    Hypotheses in the chelonian literature suggest that in species with sexual size dimorphism, the smaller sex will mature at a smaller size and a younger age than the larger sex, sex ratios should be biased in favor of the earlier maturing sex, and deviations from a 1:1 sex ratio result from maturation of the smaller sex at a younger age. I tested these hypotheses using data collected from 1991 to 1995 on an insular (Egmont Key) population of Florida box turtles, Terrapene carolina bauri. Contrary to predictions, the earlier maturing sex (males) grew to larger sizes than the late maturing sex. Males were significantly larger than females in mean carapace length but not mean body mass. Sex ratios were not balanced, favoring the earlier maturing sex (1.6 males:1 female), but the sex-ratio imbalance did not result from faster maturation of the smaller sex. The imbalance in the sex ratio in Egmont Key's box turtles is not the result of sampling biases; it may result from nest placement. Size-class structure and sex ratios can provide valuable insights into the status and trends of populations of long-lived turtles.

  10. Altruism and Rivalry: An Analysis of Age and Sex Differences.

    ERIC Educational Resources Information Center

    Skarin, Kurt

    This study examined the effects of age and sex on the degree to which altruistic behavior could be manipulated in a laboratory setting. The 192 children who participated were divided equally by sex into three age groups: 5-6 years, 7-9 years, and 10-12 years. Sex was varied both as a recipient and a benefactor characteristic. The experimental…

  11. Sex ratios and sexual dimorphism among recently transformed sea lampreys, Petromyzon marinus Linnaeus

    USGS Publications Warehouse

    Applegate, Vernon C.; Thomas, M.L.H.

    1965-01-01

    The sex, length, and weight were determined of nearly all recently transformed sea lampreys migrating downstream in the Carp Lake River, Michigan, in the fall, winter, and spring of 1960-61. Similar data were collected from samples of an earlier run in the Carp Lake River and of runs in three other tributaries of Lakes Huron and Michigan. The sex ratio of the 1960-61 migrants in the Carp Lake River was 324 males:100 females. Sex ratios of migrants in the other runs varied from 77 to 86 males:100 females. The high proportion of males in the 1960-61 run in the Carp Lake River is attributed to the effective prevention of recruitment of sea lampreys in the river and transformation of the females at an earlier age than is characteristic of the males. A near equal sex ratio among recently transformed migrants is considered normal for the species. The sex composition of a run changed during the period of migration. The proportion of males among the migrants was greatest at the beginning of the run and declined steadily thereafter. The average size was smaller for males than for females. Differences in the mean lengths and weights of the sexes were statistically significant. The length-weight relation differed for the sexes and showed a slower rate of increase of weight with increase in length than is characteristic of other stages of the animals' life cycle. Seasonal changes in the length-weight relation had a trend toward lower weights among the migrants coming downstream in the later months of the run.

  12. Poisson variations of the sex ratio at birth in African demographic surveys.

    PubMed

    Garenne, Michel

    2008-10-01

    Variations of the sex ratio at birth (SRB) were investigated using maternity history data collected in demographic surveys conducted in sub-Saharan Africa. Thirty-three countries were covered, totaling about 2.0 million births. The average SRB was 1.034 and varied by ethnicity, birth order, and maternal age. The effect of maternal age was significant for younger mothers (12-19 years old) and older mothers (40-49 years old), with a decline in sex ratios with increasing maternal age in both cases. The effect of birth order was significant only for the 20-39-year-old women, with a decline in sex ratio with increasing birth order. These two effects were similar for the three main population groups identified: populations from southern, eastern, and central Africa (SRB = 1.015), populations from West Africa and Sahelian countries (SRB = 1.040), and populations from Nigeria and Ethiopia (SRB = 1.087). In contrast, no effect of marital duration was found.

  13. Imbalanced sex ratios, men's sexual behavior, and risk of sexually transmitted infection in China.

    PubMed

    South, Scott J; Trent, Katherine

    2010-12-01

    China has been experiencing pronounced changes in its sex ratio, but little research has explored the consequences of these changes for sexual behavior and health. We merge data from the 1999-2000 Chinese Health and Family Life Survey with community-level data from the 1982, 1990, and 2000 Chinese censuses to examine the relationship between the local sex ratio and several dimensions of men's sexual behavior and sexual health. Multilevel logistic regression models show that, when faced with a relative abundance of age-matched women in their community, Chinese men are slightly less likely to have intercourse with commercial sex workers, but are more likely to engage in premarital noncommercial intercourse and to test positive for a sexually transmitted infection. These findings are consistent with hypotheses derived from demographic-opportunity theory, which suggests that an abundance of opposite-sex partners will increase the risk of early, frequent, and multi-partner sex and, through this, sexually transmitted infection risk.

  14. Sex hormones alter sex ratios in the Indian skipper frog, Euphlyctis cyanophlyctis: Determining sensitive stages for gonadal sex reversal.

    PubMed

    Phuge, S K; Gramapurohit, N P

    2015-09-01

    In amphibians, although genetic factors are involved in sex determination, gonadal sex differentiation can be modified by exogenous steroid hormones suggesting a possible role of sex steroids in regulating the process. We studied the effect of testosterone propionate (TP) and estradiol-17β (E2) on gonadal differentiation and sex ratio at metamorphosis in the Indian skipper frog, Euphlyctis cyanophlyctis with undifferentiated type of gonadal differentiation. A series of experiments were carried out to determine the optimum dose and sensitive stages for gonadal sex reversal. Our results clearly indicate the importance of sex hormones in controlling gonadal differentiation of E. cyanophlyctis. Treatment of tadpoles with 10, 20, 40, and 80μg/L TP throughout larval period resulted in the development of 100% males at metamorphosis at all concentrations. Similarly, treatment of tadpoles with 40μg/L TP during ovarian and testicular differentiation resulted in the development of 90% males, 10% intersexes and 100% males respectively. Treatment of tadpoles with 10, 20, 40, and 80μg/L E2 throughout larval period likewise produced 100% females at all concentrations. Furthermore, exposure to 40μg/L E2 during ovarian and testicular differentiation produced 95% females, 5% intersexes and 91% females, 9% intersexes respectively. Both TP and E2 were also effective in advancing the stages of gonadal development. Present study shows the effectiveness of both T and E2 in inducing complete sex reversal in E. cyanophlyctis. Generally, exposure to E2 increased the larval period resulting in significantly larger females than control group while the larval period of control and TP treated groups was comparable.

  15. Haplodiploidy and the evolution of eusociality: split sex ratios.

    PubMed

    Gardner, Andy; Alpedrinha, João; West, Stuart A

    2012-02-01

    It is generally accepted that from a theoretical perspective, haplodiploidy should facilitate the evolution of eusociality. However, the "haplodiploidy hypothesis" rests on theoretical arguments that were made before recent advances in our empirical understanding of sex allocation and the route by which eusociality evolved. Here we show that several possible promoters of the haplodiploidy effect would have been unimportant on the route to eusociality, because they involve traits that evolved only after eusociality had become established. We then focus on two biological mechanisms that could have played a role: split sex ratios as a result of either queen virginity or queen replacement. We find that these mechanisms can lead haplodiploidy to facilitating the evolution of helping but that their importance varies from appreciable to negligible, depending on the assumptions. Furthermore, under certain conditions, haplodiploidy can even inhibit the evolution of helping. In contrast, we find that the level of promiscuity has a strong and consistently negative influence on selection for helping. Consequently, from a relatedness perspective, monogamy is likely to have been a more important driver of eusociality than the haplodiploidy effect.

  16. Steinernema feltiae Intraspecific Variability: Infection Dynamics and Sex-Ratio

    PubMed Central

    Campos-Herrera, Raquel; Gutiérrez, Carmen

    2014-01-01

    Entomopathogenic nematodes (EPNs) from the Heterorhabditidae and Steinernematidae families are well-known biocontrol agents against numerous insect pests. The infective juveniles (IJs) are naturally occurring in the soil and their success in locating and penetrating the host will be affected by extrinsic/intrinsic factors that modulate their foraging behavior. Characterizing key traits in the infection dynamics of EPNs is critical for establishing differentiating species abilities to complete their life cycles and hence, their long-term persistence, in different habitats. We hypothesized that phenotypic variation in traits related to infection dynamics might occur in populations belonging to the same species. To assess these intraspecific differences, we evaluated the infection dynamics of 14 populations of Steinernema feltiae in two experiments measuring penetration and migration in sand column. Intraspecific variability was observed in the percentage larval mortality, time to kill the insect, penetration rate, and sex-ratio in both experiments (P < 0.01). Larval mortality and nematode penetration percentage were lower in migration experiments than in penetration ones in most of the cases. The sex-ratio was significantly biased toward female-development dominance (P < 0.05). When the populations were grouped by habitat of recovery (natural areas, crop edge, and agricultural groves), nematodes isolated in natural areas exhibited less larval mortality and penetration rates than those from some types of agricultural associated soils, suggesting a possible effect of the habitat on the phenotypic plasticity. This study reinforces the importance of considering intraspecific variability when general biological and ecological questions are addressed using EPNs. PMID:24644369

  17. Steinernema feltiae Intraspecific Variability: Infection Dynamics and Sex-Ratio.

    PubMed

    Campos-Herrera, Raquel; Gutiérrez, Carmen

    2014-03-01

    Entomopathogenic nematodes (EPNs) from the Heterorhabditidae and Steinernematidae families are well-known biocontrol agents against numerous insect pests. The infective juveniles (IJs) are naturally occurring in the soil and their success in locating and penetrating the host will be affected by extrinsic/intrinsic factors that modulate their foraging behavior. Characterizing key traits in the infection dynamics of EPNs is critical for establishing differentiating species abilities to complete their life cycles and hence, their long-term persistence, in different habitats. We hypothesized that phenotypic variation in traits related to infection dynamics might occur in populations belonging to the same species. To assess these intraspecific differences, we evaluated the infection dynamics of 14 populations of Steinernema feltiae in two experiments measuring penetration and migration in sand column. Intraspecific variability was observed in the percentage larval mortality, time to kill the insect, penetration rate, and sex-ratio in both experiments (P < 0.01). Larval mortality and nematode penetration percentage were lower in migration experiments than in penetration ones in most of the cases. The sex-ratio was significantly biased toward female-development dominance (P < 0.05). When the populations were grouped by habitat of recovery (natural areas, crop edge, and agricultural groves), nematodes isolated in natural areas exhibited less larval mortality and penetration rates than those from some types of agricultural associated soils, suggesting a possible effect of the habitat on the phenotypic plasticity. This study reinforces the importance of considering intraspecific variability when general biological and ecological questions are addressed using EPNs.

  18. A method for estimating population sex ratio for sage-grouse using noninvasive genetic samples.

    PubMed

    Baumgardt, J A; Goldberg, C S; Reese, K P; Connelly, J W; Musil, D D; Garton, E O; Waits, L P

    2013-05-01

    Population sex ratio is an important metric for wildlife management and conservation, but estimates can be difficult to obtain, particularly for sexually monomorphic species or for species that differ in detection probability between the sexes. Noninvasive genetic sampling (NGS) using polymerase chain reaction (PCR) has become a common method for identifying sex from sources such as hair, feathers or faeces, and is a potential source for estimating sex ratio. If, however, PCR success is sex-biased, naively using NGS could lead to a biased sex ratio estimator. We measured PCR success rates and error rates for amplifying the W and Z chromosomes from greater sage-grouse (Centrocercus urophasianus) faecal samples, examined how success and error rates for sex identification changed in response to faecal sample exposure time, and used simulation models to evaluate precision and bias of three sex assignment criteria for estimating population sex ratio with variable sample sizes and levels of PCR replication. We found PCR success rates were higher for females than males and that choice of sex assignment criteria influenced the bias and precision of corresponding sex ratio estimates. Our simulations demonstrate the importance of considering the interplay between the sex bias of PCR success, number of genotyping replicates, sample size, true population sex ratio and accuracy of assignment rules for designing future studies. Our results suggest that using faecal DNA for estimating the sex ratio of sage-grouse populations has great potential and, with minor adaptations and similar marker evaluations, should be applicable to numerous species.

  19. A female-biased sex ratio reduces the twofold cost of sex

    PubMed Central

    Kobayashi, Kazuya; Hasegawa, Eisuke

    2016-01-01

    The evolution of sexual reproduction remains a fascinating enigma in biology. Theoretically, populations of sexual organisms investing half of their resources into producing male offspring that don’t contribute to reproduction should grow at only half the rate of their asexual counterparts. This demographic disadvantage due to male production is known as the twofold cost of sex. However, the question of whether this cost is truly twofold for sexual females remains unanswered. The cost of producing males should decrease when the number of male offspring is reduced. Here, we report a case where the cost of males is actually less than twofold. By measuring the numbers of sexual strain coexisting with asexual strain among thrips, our survey revealed that the sexual strain showed female-biased sex ratios and that the relative frequency of sexual strain is negatively correlated with the proportion of males in the sexual strain. Using computer simulations, we confirmed that a female-biased sex ratio evolves in sexual individuals due to the coexistence of asexual individuals. Our results demonstrate that there is a cost of producing males that depends on the number of males. We therefore conclude that sexual reproduction can evolve with far fewer benefits than previously assumed. PMID:27035400

  20. A female-biased sex ratio reduces the twofold cost of sex

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kazuya; Hasegawa, Eisuke

    2016-04-01

    The evolution of sexual reproduction remains a fascinating enigma in biology. Theoretically, populations of sexual organisms investing half of their resources into producing male offspring that don’t contribute to reproduction should grow at only half the rate of their asexual counterparts. This demographic disadvantage due to male production is known as the twofold cost of sex. However, the question of whether this cost is truly twofold for sexual females remains unanswered. The cost of producing males should decrease when the number of male offspring is reduced. Here, we report a case where the cost of males is actually less than twofold. By measuring the numbers of sexual strain coexisting with asexual strain among thrips, our survey revealed that the sexual strain showed female-biased sex ratios and that the relative frequency of sexual strain is negatively correlated with the proportion of males in the sexual strain. Using computer simulations, we confirmed that a female-biased sex ratio evolves in sexual individuals due to the coexistence of asexual individuals. Our results demonstrate that there is a cost of producing males that depends on the number of males. We therefore conclude that sexual reproduction can evolve with far fewer benefits than previously assumed.

  1. Sex ratio estimations of loggerhead sea turtle hatchlings at Kuriat islands, Tunisia: can minor nesting sites contribute to compensate globally female-biased sex ratio?

    PubMed

    Jribi, Imed; Bradai, Mohamed Nejmeddine

    2014-01-01

    Hatchling sex ratios in the loggerhead turtle Caretta caretta were estimated by placing electronic temperature recorders in seven nests at Kuriat islands (Tunisia) during the 2013 nesting season. Based on the mean temperatures during the middle third of the incubation period, and on incubation duration, the sex ratio of hatchlings at Kuriat islands was highly male-biased. Presently, the majority of hatchling sex ratio studies are focused on major nesting areas, whereby the sex ratios are universally believed to be heavily female-biased. Here we present findings from a minor nesting site in the Mediterranean, where the hatchling sex ratio was found to be male-biased, suggesting a potential difference between major and minor nesting sites.

  2. Girl or boy? Prenatal lead, cadmium and mercury exposure and the secondary sex ratio in the ALSPAC study

    PubMed Central

    Taylor, C.M.; Golding, J.; Emond, A.M.

    2014-01-01

    The aim of this study was to evaluate the effect of prenatal exposure to lead, cadmium and mercury levels on the secondary sex ratio. Whole blood samples were collected from pregnant women enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) study at a median gestational age of 11 weeks and were analyzed for lead, cadmium and mercury. Regression analysis was used to identify associations between maternal lead, cadmium and mercury levels and the secondary sex ratio with adjustment for confounders. There was no evidence for associations between maternal lead, cadmium or mercury levels and the secondary sex ratio in this sample. It appears unlikely that alterations in the secondary sex ratio are influenced by exposure to heavy metals, but further work should be done in large cohorts in other countries to confirm these findings. PMID:24703858

  3. Sex ratio of multiple sclerosis in persons born from 1930 to 1979 and its relation to latitude in Norway.

    PubMed

    Kampman, Margitta T; Aarseth, Jan Harald; Grytten, Nina; Benjaminsen, Espen; Celius, Elisabeth Gulowsen; Dahl, Ole Petter; Holmøy, Trygve; Løken-Amsrud, Kristin; Midgard, Rune; Myhr, Kjell-Morten; Risberg, Geir; Vatne, Anita; Torkildsen, Oivind

    2013-06-01

    A remarkable increase in female to male ratio of multiple sclerosis (MS) is recognised in high incidence areas. Norway is a high-risk area for MS, spanning latitudes 58-71 °N. We studied whether the sex ratio has changed over time and whether it differs by clinical phenotype or by latitude. Population-based epidemiological data and data from the Norwegian MS Registry on patients born from 1930 to 1979 were combined in this study. Place of birth was retrieved from the Norwegian Population Registry and information on clinical subtypes was obtained from the Norwegian MS Registry. The female to male ratio ranged from 1.7 to 2.7 (median 2.0) in 5,469 patients born in Norway, and increased slightly by 5-year blocks of year of birth (p = 0.043). The sex ratio was 2.6:1 in 825 patients born 1970-1979, which is significantly higher than in those born 1930-1969 (p < 0.001). In patients with relapsing remitting onset, the sex ratio was 2.4:1, while it was 1.1:1 in those with primary progressive disease. The sex ratio did not differ between the south, the middle and the north of the country. The overall sex ratio of MS is strongly determined by cases with relapsing remitting onset. We did not observe the remarkable increase in sex ratios of MS reported from other high-risk areas. The high sex ratio in the youngest birth cohorts may change as an increasing proportion of cases in this age group is being diagnosed. Sex ratio was not associated with latitude.

  4. Relationship Formation and Stability in Emerging Adulthood: Do Sex Ratios Matter?

    ERIC Educational Resources Information Center

    Warner, Tara D.; Manning, Wendy D.; Giordano, Peggy C.; Longmore, Monica A.

    2011-01-01

    Research links sex ratios with the likelihood of marriage and divorce. However, whether sex ratios similarly influence precursors to marriage (transitions in and out of dating or cohabiting relationships) is unknown. Utilizing data from the Toledo Adolescent Relationships Study and the 2000 U.S. Census, this study assesses whether sex ratios…

  5. Working Late: Do Workplace Sex Ratios Affect Partnership Formation and Dissolution?

    ERIC Educational Resources Information Center

    Svarer, Michael

    2007-01-01

    In this paper, I analyze the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios are not important for the overall transition rate from…

  6. Getting past nature as a guide to the human sex ratio.

    PubMed

    Murphy, Timothy F

    2013-05-01

    Sex selection of children by pre-conception and post-conception techniques remains morally controversial and even illegal in some jurisdictions. Among other things, some critics fear that sex selection will distort the sex ratio, making opposite-sex relationships more difficult to secure, while other critics worry that sex selection will tilt some nations toward military aggression. The human sex ratio varies depending on how one estimates it; there is certainly no one-to-one correspondence between males and females either at birth or across the human lifespan. Complications about who qualifies as 'male' and 'female' complicate judgments about the ratio even further. Even a judiciously estimated sex ratio does not have, however, the kind of normative status that requires society to refrain from antenatal sex selection. Some societies exhibit lopsided sex ratios as a consequence of social policies and practices, and pragmatic estimates of social needs are a better guide to what the sex ratio should be, as against looking to 'nature'. The natural sex ratio cannot be a sound moral basis for prohibiting parents from selecting the sex of their children, since it ultimately lacks any normative meaning for social choices.

  7. Low sex ratio in children of professional basketball players in Spain.

    PubMed

    Palomares, A R; Lendinez Ramirez, A M; Ruiz-Galdon, M; Reyes-Engel, A

    2012-05-01

    The aim of this study was to ascertain the variations in the reproductive sex ratio (number of men to number of women) among male professional basketball players in Spain. This retrospective, cross-sectional study is based on a survey conducted in the Spanish professional basketball leagues during the season 2009-2010. A total of 172 professional basketball players completed an anonymous survey. Forty-seven of the respondents had offspring, with a total of 61 children: 70% girls and 30% boys, with a sex ratio value of 0.42. Thirty-three basketball players were Caucasian (CAU), with 44 children, nine boys and 35 girls (sex ratio = 0.26). Fourteen were black, of African heritage (AFR), with 17 children, nine boys and eight girls, (sex ratio = 1.12). Differences (P < 0.01) were found in offspring sex ratio values for all basketball players (sex ratio = 0.42) and for CAU group (sex ratio = 0.26) when compared with the general Spanish population (sex ratio = 1.06). Moreover, a significant seasonal variation was observed in CAU offspring sex ratio during the first quarter compared with the rest of the year (0.66 versus 0.12) (P < 0.03). In conclusion, a significant increase in the sex ratio value in favour of female offspring was observed in the group of CAU professional basketball players.

  8. Multigenerational response to artificial selection for biased clutch sex ratios in Tigriopus californicus populations.

    PubMed

    Alexander, H J; Richardson, J M L; Anholt, B R

    2014-09-01

    Polygenic sex determination (PSD) is relatively rare and theoretically evolutionary unstable, yet has been reported across a range of taxa. Evidence for multilocus PSD is provided by (i) large between-family variance in sex ratio, (ii) paternal and maternal effects on family sex ratio and (iii) response to selection for family sex ratio. This study tests the polygenic hypothesis of sex determination in the harpacticoid copepod Tigriopus californicus using the criterion of response to selection. We report the first multigenerational quantitative evidence that clutch sex ratio responds to artificial selection in both directions (selection for male- and female-biased families) and in multiple populations of T. californicus. In the five of six lines that showed a response to selection, realized heritability estimated by multigenerational analysis ranged from 0.24 to 0.58. Divergence of clutch sex ratio between selection lines is rapid, with response to selection detectable within the first four generations of selection.

  9. Sex Ratio and Sex Reversal in Two-year-old Class of Oyster, Crassostrea gigas (Bivalvia: Ostreidae).

    PubMed

    Park, Jung Jun; Kim, Hyejin; Kang, Seung Wan; An, Cheul Min; Lee, Sung-Ho; Gye, Myung Chan; Lee, Jung Sick

    2012-12-01

    The sex ratio (F:M) in the same population of oyster, Crassostrea gigas at the commencement of the study (2007) was 1:1.0, but changed to 1:2.8 by the end of the study (2008). The sex reversal rate in two-year-old oysters was 40.2%. Specifically, female to male sex reversal rate was 66.1%, which is higher than the male to female sex reversal rate of 21.1%. The sex reversal pattern of C. gigas appears to go from male⇒female⇒male, and as such is determined to be rhythmical hermaphroditism.

  10. Maternal Condition but Not Corticosterone Is Linked to Offspring Sex Ratio in a Passerine Bird

    PubMed Central

    Henderson, Lindsay J.; Evans, Neil P.; Heidinger, Britt J.; Adams, Aileen; Arnold, Kathryn E.

    2014-01-01

    There is evidence of offspring sex ratio adjustment in a range of species, but the potential mechanisms remain largely unknown. Elevated maternal corticosterone (CORT) is associated with factors that can favour brood sex ratio adjustment, such as reduced maternal condition, food availability and partner attractiveness. Therefore, the steroid hormone has been suggested to play a key role in sex ratio manipulation. However, despite correlative and causal evidence CORT is linked to sex ratio manipulation in some avian species, the timing of adjustment varies between studies. Consequently, whether CORT is consistently involved in sex-ratio adjustment, and how the hormone acts as a mechanism for this adjustment remains unclear. Here we measured maternal baseline CORT and body condition in free-living blue tits (Cyanistes caeruleus) over three years and related these factors to brood sex ratio and nestling quality. In addition, a non-invasive technique was employed to experimentally elevate maternal CORT during egg laying, and its effects upon sex ratio and nestling quality were measured. We found that maternal CORT was not correlated with brood sex ratio, but mothers with elevated CORT fledged lighter offspring. Also, experimental elevation of maternal CORT did not influence brood sex ratio or nestling quality. In one year, mothers in superior body condition produced male biased broods, and maternal condition was positively correlated with both nestling mass and growth rate in all years. Unlike previous studies maternal condition was not correlated with maternal CORT. This study provides evidence that maternal condition is linked to brood sex ratio manipulation in blue tits. However, maternal baseline CORT may not be the mechanistic link between the maternal condition and sex ratio adjustment. Overall, this study serves to highlight the complexity of sex ratio adjustment in birds and the difficulties associated with identifying sex biasing mechanisms. PMID:25347532

  11. Sexual orientation, handedness, sex ratio and fetomaternal tolerance-rejection.

    PubMed

    Valenzuela, Carlos Y

    2010-01-01

    Fraternal birth order (FBO) appears as a prenatal cause of 15% of homosexual males (gays) through mnemonic maternal anti-male factors. Non-right-handed men seem to be protected from homosexuality. Four hypotheses are proposed: (1) androgenic factors of non-right-handedness neutralize anti-male factors; (2) non-right-handedness and homosexuality are lethal or produce mental impairment; (3) non-right-handed male embryos are insensitive to anti-male factors; (4) mothers of non-right-handed fetuses do not produce anti-male factors. Studies of the sex ratio (SR) of older and younger siblings show: (1) a significant heterogeneity in the SR of siblings of right or non-right handed heterosexual men and women; (2) lesbians are born among siblings with high SR; (3) siblings of right-handed gays show a higher SR than non-right-handed gays that present a low SR. Based on our discovery of maternal tolerance-rejection processes, associated with genetic systems (ABO, Rh), where zygotes or embryos different from their mother induce better pregnancy and maternal tolerance than do those that share antigens with their mothers, I propose a new explanation for sexual relationships, sexual orientation, handedness and sibling SR. Lesbian embryos could induce tolerance from mothers with anti-female factors. Non-right-handedness could induce maternal tolerance, or change the maternal compatibility of "gay" embryos. Alternatively, gay embryos could be poor inducers of maternal tolerance towards male traits.

  12. Sex ratio and spatial distribution of male and female Antennaria dioica (Asteraceae) plants

    NASA Astrophysics Data System (ADS)

    Varga, Sandra; Kytöviita, Minna-Maarit

    2011-09-01

    Sex ratio, sex spatial distribution and sexual dimorphism in reproduction and arbuscular mycorrhizal colonisation were investigated in the dioecious clonal plant Antennaria dioica (Asteraceae). Plants were monitored for five consecutive years in six study plots in Oulanka, northern Finland. Sex ratio, spatial distribution of sexes, flowering frequency, number of floral shoots and the number and weight of inflorescences were recorded. In addition, intensity of mycorrhizal fungi in the roots was assessed. Both sexes flowered each year with a similar frequency, but the overall genet sex ratio was strongly female-biased. The bivariate Ripley's analysis of the sex distribution showed that within most plots sexes were randomly distributed except for one plot. Sexual dimorphism was expressed as larger floral and inflorescence production and heavier inflorescences in males. In addition, the roots of both sexes were colonised to a similar extent by arbuscular mycorrhizal fungi. The female sex-biased flowering ratios reported are not consistent among years and cannot be explained in terms of spatial segregation of the sexes or sex lability. The possible reasons for the female-biased sex ratio are discussed.

  13. Maternal exposure to polychlorinated biphenyls and the secondary sex ratio: an occupational cohort study

    PubMed Central

    2011-01-01

    Background Though commercial production of polychlorinated biphenyls was banned in the United States in 1977, exposure continues due to their environmental persistence. Several studies have examined the association between environmental polychlorinated biphenyl exposure and modulations of the secondary sex ratio, with conflicting results. Objective Our objective was to evaluate the association between maternal preconceptional occupational polychlorinated biphenyl exposure and the secondary sex ratio. Methods We examined primipara singleton births of 2595 women, who worked in three capacitor plants at least one year during the period polychlorinated biphenyls were used. Cumulative estimated maternal occupational polychlorinated biphenyl exposure at the time of the infant's conception was calculated from plant-specific job-exposure matrices. A logistic regression analysis was used to evaluate the association between maternal polychlorinated biphenyl exposure and male sex at birth (yes/no). Results Maternal body mass index at age 20, smoking status, and race did not vary between those occupationally exposed and those unexposed before the child's conception. Polychlorinated biphenyl-exposed mothers were, however, more likely to have used oral contraceptives and to have been older at the birth of their first child than non-occupationally exposed women. Among 1506 infants liveborn to polychlorinated biphenyl-exposed primiparous women, 49.8% were male; compared to 49.9% among those not exposed (n = 1089). Multivariate analyses controlling for mother's age and year of birth found no significant association between the odds of a male birth and mother's cumulative estimated polychlorinated biphenyl exposure to time of conception. Conclusions Based on these data, we find no evidence of altered sex ratio among children born to primiparous polychlorinated biphenyl-exposed female workers. PMID:21418576

  14. Sex ratio variation and spatial distribution of Siparuna grandiflora, a tropical dioecious shrub.

    PubMed

    Nicotra, A B

    1998-06-01

    Populations of dioecious plant species often exhibit biased sex ratios. Such biases may arise as a result of sex-based differences in life history traits, or as a result of spatial segregation of the sexes. Of these, sex-based differentiation in life history traits is likely to be the most common cause of bias. In dioecious species, selection can act upon the sexes in a somewhat independent way, leading to differentiation and evolution toward sex-specific ecological optima. I examined sex ratio variation and spatial distribution of the tropical dioecious shrub Siparuna grandiflora to determine whether populations exhibited a biased sex ratio, and if so, whether the bias could be explained in terms of non-random spatial distribution or sex-based differentiation in life history traits. Sex ratio bias was tested using contingency tables, a logistic regression approach was utilized to examine variation in life history traits, and spatial distributions were analyzed using Ripley's K, a second-order neighborhood analysis. I found that although populations of S. grandiflora have a male-biased sex ratio within and among years, there was no evidence of spatial segregation of the sexes. Rather, the sex ratio bias was shown to result primarily from sex-based differentiation in life history traits; males reproduce at a smaller size and more frequently than females. The sexes also differ in the relationship between plant size and reproductive frequency. Light availability was shown to affect reproductive activity in both sexes, though among infrequently flowering plants, females require higher light levels than males to flower. The results of this study demonstrate that ecologically significant sex-based differentiation has evolved in S. grandiflora.

  15. High Adult Sex Ratios and Risky Sexual Behaviors: A Systematic Review

    PubMed Central

    Bien, Cedric H.; Cai, Yong; Emch, Michael E.; Parish, William; Tucker, Joseph D.

    2013-01-01

    Background Thirty-four countries worldwide have abnormally high sex ratios (>102 men per 100 women), resulting in over 100 million missing women. Widespread sex selective abortion, neglect of young girls leading to premature mortality, and gendered migration have contributed to these persistent and increasing distortions. Abnormally high adult sex ratios in communities may drive sexually transmitted disease (STD) spread where women are missing and men cannot find stable partners. We systematically reviewed evidence on the association between high community sex ratios and individual sexual behaviors. Methods and Findings Seven databases (PubMed, Web of Science, Embase, Scopus, The Cochrane Database of Systematic Reviews, Sociological Abstracts, and PopLINE) were searched without restrictions on time or location. We followed PRISMA guidelines and evaluated quality according to STROBE criteria. 1093 citations were identified and six studies describing 57,054 individuals were included for review. All six studies showed an association between high community sex ratios and individual sexual risk behaviors. In high sex ratio communities, women were more likely to have multiple sex partners and men were more likely to delay first sexual intercourse and purchase sex. Only two studies included STD outcomes. Conclusions High community sex ratios were associated with increased individual sexual risk behavior among both men and women. However, none of the studies examined unprotected sex or appropriately adjusted for gendered migration. Further studies are needed to understand the effect of community sex ratios on sexual health and to inform comprehensive STD control interventions. PMID:23967223

  16. Hyperostosis frontalis interna: criteria for sexing and aging a skeleton.

    PubMed

    May, Hila; Peled, Nathan; Dar, Gali; Cohen, Haim; Abbas, Janan; Medlej, Bahaa; Hershkovitz, Israel

    2011-09-01

    Estimation of sex and age in skeletons is essential in anthropological and forensic medicine investigations. The aim of the current study was to examine the potential of hyperostosis frontalis interna (HFI) as a criterion for determining sex and age in forensic cases. Macroscopic examination of the inner aspect of the frontal bone of 768 skulls (326 males and 442 females) aged 1 to 103, which had undergone a head computerized tomography scan, was carried out using the volume rendering technique. HFI was divided into two categories: minor and major. HFI is a sex- and age-dependent phenomena, with females manifesting significantly higher prevalence than males (p<0.01). In both females and males, prevalence of HFI increases as age increases (p<0.01). We present herein the probabilities of designating an unknown skull to a specific sex and age cohort according to the presence of HFI (standardized to age distribution in an Israeli population). Moreover, we present the probability of an individual belonging to a specific sex or age cohort according to age or sex (respectively) and severity of HFI. We suggest a valid, reliable, and easy method for sex and age identification of unknown skulls.

  17. Experimental demonstration that pre- and post-conceptional mechanisms influence sex ratio in mouse embryos.

    PubMed

    Jiménez, Adela; Fernández, Raúl; Madrid-Bury, Ninoska; Moreira, Pedro Nuno; Borque, Concepción; Pintado, Belén; Gutiérrez-Adán, Alfonso

    2003-10-01

    Previously we have demonstrated in two monotocous species (bovine and sheep), a relationship between time of insemination, moment of ovulation, and embryo sex ratio. Here, we have analyzed in a polytocous specie (mice) if in addition to pre-conceptional mechanisms, also post-conceptional ones affect the offspring sex ratio. To verify this hypothesis we carried out two experiments. In the first experiment, we analyzed the effect of mating dynamics on the sex ratio of mice with synchronic male and female embryo development. Females were mated before and after ovulation and sacrificed 13 days later for sex determination of embryos and reabsorptions. A decreased litter size, and an increased offspring sex ratio in matings occurring later in oestrus, supported the view that a biased sex ratio may occur as the result of behavioral differences between the populations of X- or Y-bearing spermatozoa. In the second experiment, embryos developmentally synchronic and asynchronic with the recipient female endometrium were transferred, and again, 13 days later, females were sacrificed for sex determination of embryos and reabsorptions. The male proportion per litter found, indicated that our developmentally asynchronic transfers favored a sex ratio disbalance at birth. When combined, these results become the first experimental evidence supporting the view that both pre- and post-conceptional mechanisms of sex ratio distortion in polytocous species are not mutually exclusive and both may explain, under different conditions, sex ratio deviations at birth.

  18. Sex ratio and fledging success of supplementary-fed Tengmalm's owl broods.

    PubMed

    Hörnfeldt, B; Hipkiss, T; Fridolfsson, A K; Eklund, U; Ellegren, H

    2000-02-01

    A nest box population of Tengmalm's owls (Aegolius funereus) in northern Sweden was studied to investigate the effects of extra food on the sex ratio between hatching and fledging in this sexually size-dimorphic species. The brood size and brood sex ratio of supplementary-fed and control broods were compared. Newly hatched nestlings were blood sampled and sexed by polymerase chain reaction (PCR) amplification of the sex-linked CHD1Z and CHD1W genes. The brood sex ratio at hatching was strongly male biased (65%); this was also the case in broods where all eggs hatched (72%). There was no relationship between hatch order and sex ratio, and hatching sex ratio did not vary significantly with laying date. Brood size decreased between hatching and fledging, but did not differ between fed and control broods at either stage. Brood sex ratio did not differ between hatching and fledging, and fledging sex ratio did not differ between fed and control broods. It was concluded that, at least during the year in which the study was carried out, feeding had no effect on brood reduction, and that male and female nestlings did not show any differential mortality. The mechanisms behind the male-biased sex ratio at hatching, and any possible adaptive reasons for it, are not known.

  19. Ecological context and metapopulation dynamics affect sex-ratio variation among dioecious plant populations

    PubMed Central

    Field, David L.; Pickup, Melinda; Barrett, Spencer C. H.

    2013-01-01

    Background and Aims Populations of dioecious flowering plants commonly exhibit heterogeneity in sex ratios and deviations from the equilibrium expectation of equal numbers of females and males. Yet the role of ecological and demographic factors in contributing towards biased sex ratios is currently not well understood. Methods Species-level studies from the literature were analysed to investigate ecological correlates of among-population sex-ratio variation and metapopulation models and empirical data were used to explore the influence of demography and non-equilibrium conditions on flowering sex ratios. Key Results The survey revealed significant among-population heterogeneity in sex ratios and this was related to the degree of sampling effort. For some species, sex-ratio bias was associated with the proportion of non-reproductive individuals, with greater male bias in populations with a lower proportion of individuals that were flowering. Male-biased ratios were also found at higher altitudes and latitudes, and in more xeric sites. Simulations and empirical data indicated that clonal species exhibited greater heterogeneity in sex ratios than non-clonal species as a result of their slower approach to equilibrium. The simulations also indicated the importance of interactions between reproductive mode and founder effects, with greater departures from equilibrium in clonal populations with fewer founding individuals. Conclusions The results indicate that sex-based differences in costs of reproduction and non-equilibrium conditions can each play important roles in affecting flowering sex ratios in populations of dioecious plants. PMID:23444124

  20. Pollinating fig wasp Ceratosolen solmsi adjusts the offspring sex ratio to other foundresses.

    PubMed

    Hu, Hao-Yuan; Chen, Zhong-Zheng; Jiang, Zi-Feng; Huang, Da-Wei; Niu, Li-Ming; Fu, Yue-Guan

    2013-04-01

    Local mate competition theory predicts that offspring sex ratio in pollinating fig wasps is female-biased when there is only one foundress, and increased foundress density results in increased offspring sex ratio. Information of other foundresses and clutch size have been suggested to be the main proximate explanations for sex ratio adjustment under local mate competition. Our focus was to show the mechanism of sex ratio adjustment in a pollinating fig wasp, Ceratosolen solmsi Mayr, an obligate pollinator of the functionally dioecious fig, Ficus hispida Linn., with controlled experiments in the field. First, we obtained offspring from one pollinator and offspring at different oviposition sequences, and found that offspring sex ratio decreased with clutch size, and pollinators produced most of their male offspring at the start of bouts, followed by mostly females. Second, we found that offspring sex ratio increased with foundress density, and pollinators did adjust their offspring sex ratio to other females in the oviposition patches. We suggest that when oviposition sites are not limited, pollinators will mainly adjust their offspring sex ratio to other foundresses independent of clutch size changes, whereas adjusting clutch size may be used to adjust sex ratio when oviposition sites are limited.

  1. Age and sex differences in estimated tibia strength: influence of measurement site.

    PubMed

    Sherk, Vanessa D; Bemben, Debra A

    2013-01-01

    Variability in peripheral quantitative computed tomography (pQCT) measurement sites and outcome variables limit direct comparisons of results between studies. Furthermore, it is unclear what estimates of bone strength are most indicative of changes due to aging, disease, or interventions. The purpose of this study was to examine age and sex differences in estimates of tibia strength. An additional purpose of this study was to determine which tibia site or sites are most sensitive for detecting age and sex differences in tibia strength. Self-identifying Caucasian men (n=55) and women (n=59) aged 20-59yr had their tibias measured with pQCT from 5% to 85% of limb length in 10% increments distal to proximal. Bone strength index, strength strain index (SSI), moments of inertia (Ip, Imax, and Imin), and strength-to-mass ratios (polar moment of inertia to total bone mineral content [BMC] ratio [Ip:Tot.BMC] and strength strain index to total BMC ratio [SSI:Tot.BMC]) were quantified. There were significant (p<0.01) site effects for all strength variables and strength-to-mass ratios. Site×sex interaction effects were significant (p<0.05) for all strength variables. Men had greater (p<0.01) values than women for all strength variables. Sex differences in Ip, Imax, Ip:Tot.BMC, SSI, and SSI:Tot.BMC ratios were the smallest at the 15% site and peaked at various sites, depending on variable. Site×age interactions existed for Imax, Ip:Tot.BMC, and SSI:Tot.BMC. There were significant age effects, Imax, Ip:Tot.BMC, and SSI:Tot.BMC, as values were the lowest in the 20-29 age group. Age and sex differences varied by measurement site and variable, and larger sex differences existed for moments of inertia than SSI. Strength-to-mass ratios may reflect efficiency of the whole bone architecture.

  2. Exposure to widespread environmental endocrine disrupting chemicals and human sperm sex ratio.

    PubMed

    Jurewicz, Joanna; Radwan, Michał; Sobala, Wojciech; Radwan, Paweł; Jakubowski, Lucjusz; Wielgomas, Bartosz; Ligocka, Danuta; Brzeźnicki, Sławomir; Hanke, Wojciech

    2016-06-01

    In recent years, a trend toward a declining proportion of male births has been noted in several, but not all, industrialized countries. The underlying reason for the drop in the sex ratio is unclear, but one theory states that widespread environmental endocrine disrupting chemicals affecting the male reproductive system in a negative manner could be part of the explanation. The present study was designed to investigate whether the urinary phthalate, pyrethroids and polycyclic aromatic hydrocarbons metabolites concentrations were associated with sperm Y:X ratio. The study population consisted of 194 men aged under 45 years of age who attended infertility clinic in Lodz, Poland for diagnostic purposes with normal semen concentration of 20-300 mln/ml or with slight oligozoospermia (semen concentration of 15-20 mln/ml) (WHO, 1999). The Y:X ratio was assessed by fluorescent in situ hybridization. Urinary concentrations of 1-hydroxypyrene were measured by high performance liquid chromatography, phthalate metabolites were analyzed using a procedure based on the LC-MS/MS methods and metabolites of synthetic pyrethroids were assessed by gas chromatography ion-tap mass spectrometry method. After adjustment for potential confounders (past diseases, age, abstinence, smoking, alcohol consumption, sperm concentration, motility, morphology) 5OH MEHP, CDCCA to TDCCA and 1-OHP was negatively related to Y:X sperm chromosome ratio (p = 0.033, p < 0.001, p = 0.047 respectively). As this is the first study to elucidate the association between the level of metabolites of widespread environmental endocrine disrupting chemicals (phthalates, synthetic pyrethroids, polycyclic aromatic hydrocarbons) on sex chromosome ratio in sperm therefore, these findings require further replication in other populations.

  3. Changes in sex ratio from fertilization to birth in assisted-reproductive-treatment cycles

    PubMed Central

    2014-01-01

    Background In Western gender-neutral countries, the sex ratio at birth is estimated to be approximately 1.06. This ratio is lower than the estimated sex ratio at fertilization which ranges from 1.07 to 1.70 depending on the figures of sex ratio at birth and differential embryo/fetal mortality rates taken into account to perform these estimations. Likewise, little is known about the sex ratio at implantation in natural and assisted-reproduction-treatment (ART) cycles. In this bioessay, we aim to estimate the sex ratio at fertilization and implantation using data from embryos generated by standard in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) in preimplantation genetic diagnosis cycles. Thereafter, we compare sex ratios at implantation and birth in cleavage- and blastocyst-stage-transfer cycles to propose molecular mechanisms accounting for differences in post-implantation male and female mortality and thereby variations in sex ratios at birth in ART cycles. Methods A literature review based on publications up to December 2013 identified by PubMed database searches. Results Sex ratio at both fertilization and implantation is estimated to be between 1.29 and 1.50 in IVF cycles and 1.07 in ICSI cycles. Compared with the estimated sex ratio at implantation, sex ratio at birth is lower in IVF cycles (1.03 after cleavage-stage transfer and 1.25 after blastocyst-stage transfer) but similar and close to unity in ICSI cycles (0.95 after cleavage-stage transfer and 1.04 after blastocyst-stage transfer). Conclusions In-vitro-culture-induced precocious X-chromosome inactivation together with ICSI-induced decrease in number of trophectoderm cells in female blastocysts may account for preferential female mortality at early post-implantation stages and thereby variations in sex ratios at birth in ART cycles. PMID:24957129

  4. Sex ratios in early childhood autism and related conditions.

    PubMed

    Wing, L

    1981-10-01

    Children aged 0-14 on a specified census day, with impairments of verbal and nonverbal communication, social interaction and imaginative play, and with repetitive, stereotyped activities, were identified in an epidemiological study carried out in an area of southeast London. Sociable moderately, severely, and profoundly retarded children were included for comparison. An overall male:female ratio of 2.6:1 was found in those with language and social impairments, but, in the children of this group who were moderately, severely, or profoundly retarded, the ratio was 2.1:1, closely similar to that found in children in the same IQ range with Down's syndrome or cerebral palsy. The excess of males was much more marked in language and socially impaired children who were of higher ability, or who had a history of typical early childhood autism. The findings were linked to hypotheses of genetically greater variability in males, and to male-female differences in visuo-spatial and language skills.

  5. Sex Offenders in the Digital Age.

    PubMed

    Chan, Eric J; McNiel, Dale E; Binder, Renee L

    2016-09-01

    With most youths now using the Internet and social networking sites (SNSs), the public has become increasingly concerned about risks posed by online predators. In response, lawmakers have begun to pass laws that ban or limit sex offenders' use of the Internet and SNSs. At the time of this article, 12 states and the federal government have passed legislation attempting to restrict or ban the use of SNSs by registered sex offenders. These laws have been successfully challenged in 4 states. In this article, we discuss examples of case law that illustrate evolving trends regarding Internet and social networking site restrictions on sex offenders on supervised release, as well as those who have already completed their sentences. We also review constitutional questions and empirical evidence concerning Internet and social networking use by sex offenders. To our knowledge, this is the first paper in the psychiatric literature that addresses the evolving legal landscape in reference to sex offenders and their use of the Internet and SNSs. This article is intended to help inform forensic mental health professionals who work with sex offenders on current concerns in this rapidly evolving legal landscape.

  6. Birth order and sibling sex ratio in two samples of Dutch gender-dysphoric homosexual males.

    PubMed

    Blanchard, R; Zucker, K J; Cohen-Kettenis, P T; Gooren, L J; Bailey, J M

    1996-10-01

    Two studies were undertaken to confirm the previous findings that homosexual men in general tend to have a later than expected birth order and that extremely feminine homosexual men also tend to have a higher than expected proportion of brothers (i.e., a higher sibling sex ratio). Subjects in Study 1 were Dutch, adult and adolescent, biological male patients with gender dysphoria (persistent and recurrent desires to belong to the opposite sex), who were undergoing treatment with feminizing hormones. These comprised 83 patients who reported sexual attraction to other males (the homosexual group) and 58 who reported sexual attraction to females or equal attraction to males and females (the non-homosexual group). Subjects in Study 2 were Dutch adolescent male patients at another hospital. The homosexual group consisted of 21 gender-dysphoric homosexual teenagers referred to a gender identity clinic for children and adolescents. The control group were 21 adolescent males referred to the child psychiatry department of the same hospital for reasons other than gender identity disorder, homosexuality, or transvestism. These were individually matched to the homosexual subjects on age and sibship size. In both studies, the homosexual group had a significantly later average birth order than the comparison group. In Study 1, the homosexual group had a significantly elevated sibling sex ratio; this was not tested in Study 2 because of its small sample size. These studies add to the mounting evidence that late birth orders are common to all homosexual samples and that elevated sibling sex ratios are an additional characteristic of extremely feminine ones.

  7. Comparative analyses of sex-ratio variation in dioecious flowering plants.

    PubMed

    Field, David L; Pickup, Melinda; Barrett, Spencer C H

    2013-03-01

    Dioecious plant species commonly exhibit deviations from the equilibrium expectation of 1:1 sex ratio, but the mechanisms governing this variation are poorly understood. Here, we use comparative analyses of 243 species, representing 123 genera and 61 families to investigate ecological and genetic correlates of variation in the operational (flowering) sex ratio. After controlling for phylogenetic nonindependence, we examined the influence of growth form, clonality, fleshy fruits, pollen and seed dispersal vector, and the possession of sex chromosomes on sex-ratio variation. Male-biased flowering sex ratios were twice as common as female-biased ratios. Male bias was associated with long-lived growth forms (e.g., trees) and biotic seed dispersal and fleshy fruits, whereas female bias was associated with clonality, especially for herbaceous species, and abiotic pollen dispersal. Female bias occurred in species with sex chromosomes and there was some evidence for a greater degree of bias in those with heteromorphic sex chromosomes. Although the role of interactions among these correlates require further study, our results indicate that sex-based differences in costs of reproduction, pollen and seed dispersal mechanisms and sex chromosomes can each play important roles in affecting flowering sex ratios in dioecious plants.

  8. Romanticism as a function of age, sex, and ethnicity.

    PubMed

    Regan, Pamela C; Anguiano, Carlos

    2010-12-01

    This study examined the association between romanticism (operationalized as mean score on the Romantic Beliefs Scale) and age, sex, and ethnicity in a large community sample (N = 436). Age was negatively correlated with romanticism scores; as age increased, romanticism scores decreased. No sex differences were found; men and women had similar, moderate scores. Although ethnicity largely was unrelated to romanticism, Asian/Pacific Islander participants were significantly more romantic than were African-American participants.

  9. Invasion, Coexistence, and Extinction Driven by Preemptive Competition and Sex Ratio

    NASA Astrophysics Data System (ADS)

    Molnar, Ferenc; Caraco, Thomas; Korniss, Gyorgy

    2012-02-01

    We investigate competitive invasion in a simple population dynamics model, where females can differ genetically in the sex ratio of their offspring, and males can differ in mortality. Analyzing of the mean-field dynamics, we obtain conditions for ecological stability of a given sex-ratio allele for any mortality rate parameters. We also found that stable coexistence of the two alleles is possible, but only males can differ; one female phenotype is present. Our results show that the success of invasion is determined by the female birth sex ratio. A lower female ratio never excludes a larger female sex ratio; in case of coexistence, the surviving female phenotype always has the greater female sex ratio. Finally, we identified an interesting invasion-to-extinction scenario: successful invasion followed by extinction occurs when the invader initially propagates with the resident allele, but after excluding the resident, cannot survive on its own.

  10. A method for estimating fall adult sex ratios from production and survival data

    USGS Publications Warehouse

    Wight, H.M.; Heath, R.G.; Geis, A.D.

    1965-01-01

    This paper presents a method of utilizing data relating to the production and survival of a bird population to estimate a basic fall adult sex ratio. This basic adult sex ratio is an average value derived from average production and survival rates. It is an estimate of the average sex ratio about which the fall adult ratios will fluctuate according to annual variations in production and survival. The basic fall adult sex ratio has been calculated as an asymptotic value which is the limit of an infinite series wherein average population characteristics are used as constants. Graphs are provided that allow the determination of basic sex ratios from production and survival data of a population. Where the respective asymptote has been determined, it may be possible to estimate various production and survival rates by use of variations of the formula for estimating the asymptote.

  11. Manipulation of primary sex ratio in birds: lessons from the homing pigeon (Columba livia domestica).

    PubMed

    Goerlich-Jansson, Vivian C; Müller, Martina S; Groothuis, Ton G G

    2013-12-01

    Across various animal taxa not only the secondary sex ratio but also the primary sex ratio (at conception) shows significant deviations from the expected equal proportions of sons and daughters. Birds are especially intriguing to study this phenomenon as avian females are the heterogametic sex (ZW); therefore sex determination might be under direct control of the mother. Avian sex ratios vary in relation to environmental or maternal condition, which can also affect the production of maternal steroids that in turn are involved in reproduction and accumulate in the developing follicle before meiosis. As the proximate mechanisms underlying biased primary sex ratio are largely elusive, we explored how, and to what extent, maternal steroid hormones may be involved in affecting primary or secondary sex ratio in clutches of various species of pigeons. First we demonstrated a clear case of seasonal change in sex ratio in first eggs both in the Rock Pigeon (Columba livia) and in a related species, the Wood Pigeon (Columba palumbus), both producing clutches of two eggs. In the Homing Pigeon (Columba livia domestica), domesticated from the Rock Pigeon, testosterone treatment of breeding females induced a clear male bias, while corticosterone induced a female bias in first eggs and we argue that this is in line with sex allocation theory. We next analyzed treatment effects on follicle formation, yolk mass, and yolk hormones, the latter both pre- and post-ovulatory, in order to test a diversity of potential mechanisms related to both primary and secondary sex ratio manipulation. We conclude that maternal plasma hormone levels may affect several pre-ovulatory mechanisms affecting primary sex ratio, whereas egg hormones are probably involved in secondary sex ratio manipulation only.

  12. Territory Quality and Plumage Morph Predict Offspring Sex Ratio Variation in a Raptor.

    PubMed

    Chakarov, Nayden; Pauli, Martina; Mueller, Anna-Katharina; Potiek, Astrid; Grünkorn, Thomas; Dijkstra, Cor; Krüger, Oliver

    2015-01-01

    Parents may adapt their offspring sex ratio in response to their own phenotype and environmental conditions. The most significant causes for adaptive sex-ratio variation might express themselves as different distributions of fitness components between sexes along a given variable. Several causes for differential sex allocation in raptors with reversed sexual size dimorphism have been suggested. We search for correlates of fledgling sex in an extensive dataset on common buzzards Buteo buteo, a long-lived bird of prey. Larger female offspring could be more resource-demanding and starvation-prone and thus the costly sex. Prominent factors such as brood size and laying date did not predict nestling sex. Nonetheless, lifetime sex ratio (LSR, potentially indicative of individual sex allocation constraints) and overall nestling sex were explained by territory quality with more females being produced in better territories. Additionally, parental plumage morphs and the interaction of morph and prey abundance tended to explain LSR and nestling sex, indicating local adaptation of sex allocation However, in a limited census of nestling mortality, not females but males tended to die more frequently in prey-rich years. Also, although females could have potentially longer reproductive careers, a subset of our data encompassing full individual life histories showed that longevity and lifetime reproductive success were similarly distributed between the sexes. Thus, a basis for adaptive sex allocation in this population remains elusive. Overall, in common buzzards most major determinants of reproductive success appeared to have no effect on sex ratio but sex allocation may be adapted to local conditions in morph-specific patterns.

  13. Territory Quality and Plumage Morph Predict Offspring Sex Ratio Variation in a Raptor

    PubMed Central

    Chakarov, Nayden; Pauli, Martina; Mueller, Anna-Katharina; Potiek, Astrid; Grünkorn, Thomas; Dijkstra, Cor; Krüger, Oliver

    2015-01-01

    Parents may adapt their offspring sex ratio in response to their own phenotype and environmental conditions. The most significant causes for adaptive sex-ratio variation might express themselves as different distributions of fitness components between sexes along a given variable. Several causes for differential sex allocation in raptors with reversed sexual size dimorphism have been suggested. We search for correlates of fledgling sex in an extensive dataset on common buzzards Buteo buteo, a long-lived bird of prey. Larger female offspring could be more resource-demanding and starvation-prone and thus the costly sex. Prominent factors such as brood size and laying date did not predict nestling sex. Nonetheless, lifetime sex ratio (LSR, potentially indicative of individual sex allocation constraints) and overall nestling sex were explained by territory quality with more females being produced in better territories. Additionally, parental plumage morphs and the interaction of morph and prey abundance tended to explain LSR and nestling sex, indicating local adaptation of sex allocation However, in a limited census of nestling mortality, not females but males tended to die more frequently in prey-rich years. Also, although females could have potentially longer reproductive careers, a subset of our data encompassing full individual life histories showed that longevity and lifetime reproductive success were similarly distributed between the sexes. Thus, a basis for adaptive sex allocation in this population remains elusive. Overall, in common buzzards most major determinants of reproductive success appeared to have no effect on sex ratio but sex allocation may be adapted to local conditions in morph-specific patterns. PMID:26445010

  14. How rapidly can maternal behavior affecting primary sex ratio evolve in a reptile with environmental sex determination?

    PubMed

    Morjan, Carrie L

    2003-08-01

    Theoretical models identify maternal behavior as critical for the maintenance and evolution of sex ratios in organisms with environmental sex determination (ESD). Maternal choice of nest site is generally thought to respond more rapidly to sex ratio selection than environmental sensitivity of offspring sex (threshold temperatures) in reptiles with temperature-dependent sex determination (TSD, a form of ESD). However, knowledge of the evolutionary potential for either of these traits in a field setting is limited. I developed a simulation model using local climate data and observed levels of phenotypic variation for nest-site choice and threshold temperatures in painted turtles (Chrysemys picta) with TSD. Both nest-site choice and threshold temperatures, and hence sex ratios, evolved slowly to simulated climate change scenarios. In contrast to expectations from previous models, nest-site choice evolved more slowly than threshold temperatures because of large climatic effects on nest temperatures and indirect selection on maternally expressed traits. A variant of the model, assuming inheritance of nest-site choice through natal imprinting, demonstrated that natal imprinting inhibited adaptive responses in female nest-site choice to climate change. These results predict that females have relatively low potential to adaptively adjust sex ratios through nest-site choice.

  15. Sex through the ages in China.

    PubMed

    Gross, A

    1981-11-01

    This brief article summarizes some of the Chinese sexual customs as revealed by Van Gulik, Needham, Levy, the author, and others. Chinese sexology is related to medicine, philosophy, and cosmology, all of which form a unified view of the universe. Cosmologically, the Chinese view human life as between the sun ("Ying"/man) and the earth ("Yin"/women). Energy particles from the sun continually enter the fingers, pass through arms, head, and body, and exit via the toes, while energy from the earth enter through the toes and exits through the fingers. Illness occurs if there is an imbalance in this system; if either flow stops death ensues. Chinese medicine corrects the energy flow of the sun and earth by means of needles, heat, gymnastics, massage, and sexual practices. Sexual practices, affect this energy exchange by special techniques for relieving physical complaints and ultra-orgasmic practices, sometimes termed "coitus reservatus." Chinese reason that if either man or woman achieve orgasm, then considerable energy can be produced over a longer duration, perhaps increasing one's health and longevity. These beliefs flourished from the Han Dynasty (202 B.C.-220 A.D.) until the close of the Ming Dynasty (1368-1644 A.D.). Practices during this period were to encourage orgasms for men and women with age, health, seasonal factors, and the need for heirs as variables in the practices. For example, in a Sui Dynasty (589-608 A.D.) sex manual, once a day is right for a healthy male of 30, while once every 5-10 days is proper for a 50 year old man. However, these techniques took time to learn and even "perversions" developed. Excesses encouraged the belief that sexual expression should be limited. The Confucionists during the Ching Dynasty (1644-1912) saw ultra-orgasmic exercises as a threat to government and encouraged its end. Ultra-orgasmic techniques may be used today at the village level and are inseparable from the Chinese language and literature. Male homosexuality

  16. Sex Ratio Adaptations to Local Mate Competition in a Parasitic Wasp.

    ERIC Educational Resources Information Center

    Werren, John H.

    1980-01-01

    This study discusses the behavior of the females of the parasitic wasp Nasonia vitripennis, which adjust the sex ratio of their broods according to whether or not they are the first or second wasp to parasitize a host. The results provide a quantitative test of sex ratio theory. (Author/SA)

  17. On the Relationship between Marital Opportunity and Teen Pregnancy: The Sex Ratio Question.

    ERIC Educational Resources Information Center

    Barber, Nigel

    2001-01-01

    Used United Nations cross-national data to examine the relationship between low sex ratio, marital opportunity, and teen pregnancy. Geographical region, per capita gross national product, marital rate, and urban and rural status were used as control variables in analyses that utilized sex ratios to predict teen births. Overall, early childbearing…

  18. The Financial Consequences of Too Many Men: Sex Ratio Effects on Saving, Borrowing, and Spending

    PubMed Central

    Griskevicius, Vladas; Tybur, Joshua M.; Ackerman, Joshua M.; Delton, Andrew W.; Robertson, Theresa E.; White, Andrew E.

    2012-01-01

    The ratio of males to females in a population is an important factor in determining behavior in animals. We propose that sex ratio also has pervasive effects in humans, such as by influencing economic decisions. Using both historical data and experiments, we examined how sex ratio influences saving, borrowing, and spending in the United States. Findings show that male-biased sex ratios (an abundance of men) lead men to discount the future and desire immediate rewards. Male-biased sex ratios decreased men’s desire to save for the future and increased their willingness to incur debt for immediate expenditures. Sex ratio appears to influence behavior by increasing the intensity of same-sex competition for mates. Accordingly, a scarcity of women led people to expect men to spend more money during courtship, such as by paying more for engagement rings. These findings demonstrate experimentally that sex ratio influences human decision making in ways consistent with evolutionary biological theory. Implications for sex ratio effects across cultures are discussed. PMID:21767031

  19. Sibling Sex Ratio of Individuals Diagnosed with Autism Spectrum Disorder as Children

    ERIC Educational Resources Information Center

    Mouridsen, Svend Erik; Rich, Bente; Isager, Torben

    2010-01-01

    Aim: To study the sex ratio (proportion of males) in siblings of individuals diagnosed with autism spectrum disorders (ASDs) as children. Method: In the current study, we extended previous studies dealing with the androgen theory of autism and examined sex ratios in the siblings of 326 individuals with ASD (245 males, 81 females) who had been…

  20. Inter-Annual Variability of Fledgling Sex Ratio in King Penguins

    PubMed Central

    Viblanc, Vincent A.; Gachot-Neveu, Hélène; Beaugey, Magali; Le Maho, Yvon; Le Bohec, Céline

    2014-01-01

    As the number of breeding pairs depends on the adult sex ratio in a monogamous species with biparental care, investigating sex-ratio variability in natural populations is essential to understand population dynamics. Using 10 years of data (2000–2009) in a seasonally monogamous seabird, the king penguin (Aptenodytes patagonicus), we investigated the annual sex ratio at fledging, and the potential environmental causes for its variation. Over more than 4000 birds, the annual sex ratio at fledging was highly variable (ranging from 44.4% to 58.3% of males), and on average slightly biased towards males (51.6%). Yearly variation in sex-ratio bias was neither related to density within the colony, nor to global or local oceanographic conditions known to affect both the productivity and accessibility of penguin foraging areas. However, rising sea surface temperature coincided with an increase in fledging sex-ratio variability. Fledging sex ratio was also correlated with difference in body condition between male and female fledglings. When more males were produced in a given year, their body condition was higher (and reciprocally), suggesting that parents might adopt a sex-biased allocation strategy depending on yearly environmental conditions and/or that the effect of environmental parameters on chick condition and survival may be sex-dependent. The initial bias in sex ratio observed at the juvenile stage tended to return to 1∶1 equilibrium upon first breeding attempts, as would be expected from Fisher’s classic theory of offspring sex-ratio variation. PMID:25493708

  1. Pre-ovulation control of hatchling sex ratio in the Seychelles warbler.

    PubMed Central

    Komdeur, Jan; Magrath, Michael J L; Krackow, Sven

    2002-01-01

    Females of some bird species have a high degree of control over the sex ratio of their offspring at laying. Although several mechanisms have been put forward to explain how females might control the sex of their eggs, virtually nothing is known. As females are the heterogametic sex in birds, adjustment of the clutch sex ratio could arise either by pre- or post-ovulation control mechanisms. The Seychelles warbler (Acrocephalus sechellensis) exhibits extreme adaptive egg sex ratio bias. Typically, warblers produce only single-egg clutches, but by translocating pairs to vacant habitat of very high quality, most females were induced to produce two-egg clutches. Overall, females skewed clutch sex ratios strongly towards daughters (86.6%). This bias was evident in the first egg, but critically, also in the second eggs laid a day apart, even when all absent, unhatched, or unsexed second eggs were assumed to be male. Although a bias in the first egg may arise through either pre- or post-ovulation mechanisms, the skew observed in second eggs could only arise through pre-ovulation control. Post-ovulation adjustment may also contribute to skewed hatchling sex ratios, but as sex-biased release of gametes is likely to be a more efficient process of control, pre-ovulation mechanisms may be the sole means of adjustment in this species. High fitness differentials between sons and daughters, as apparent in the Seychelles warblers, may be necessary for primary sex ratio adjustment to evolve. PMID:12028765

  2. Density-dependent regulation of the sex ratio in an annual plant.

    PubMed

    Dorken, Marcel E; Pannell, John R

    2008-06-01

    Sex ratios are subject to strong frequency-dependent selection regulated by the mating system and the relative male versus female investment. In androdioecious plant populations, where males co-occur with hermaphrodites, the sex ratio depends on the rate of self-fertilization by hermaphrodites and on the relative pollen production of males versus hermaphrodites. Here, we report evolutionary changes in the sex ratio from experimental mating arrays of the androdioecious plant Mercurialis annua. We found that the progeny sex ratio depended strongly on density, with fewer males in the progeny of plants grown under low density. This occurred in part because of a plastic adjustment in pollen production by hermaphrodites, which produced more pollen when grown at low density than at high density. Our results provide support for the prediction that environmental conditions govern sex ratios through their effects on the relative fertility of unisexual versus hermaphrodite individuals.

  3. Birth order and sibling sex ratio of children and adolescents referred to a gender identity service.

    PubMed

    Vanderlaan, Doug P; Blanchard, Ray; Wood, Hayley; Zucker, Kenneth J

    2014-01-01

    In adult male samples, homosexuality is associated with a preponderance of older brothers (i.e., the fraternal birth order effect). In several studies comparing gender dysphoric youth, who are likely to be homosexual in adulthood, to clinical or non-clinical control groups, the findings have been consistent with the fraternal birth order effect in males; however, less is known about unique sibship characteristics of gender dysphoric females. The current study investigated birth order and sibling sex ratio in a large sample of children and adolescents referred to the same Gender Identity Service (N = 768). Probands were classified as heterosexual males, homosexual males, or homosexual females based on clinical diagnostic information. Groups differed significantly in age and sibship size, and homosexual females were significantly more likely to be only children. Subsequent analyses controlled for age and for sibship size. Compared to heterosexual males, homosexual males had a significant preponderance of older brothers and homosexual females had a significant preponderance of older sisters. Similarly, the older sibling sex ratio of homosexual males showed a significant excess of brothers whereas that of homosexual females showed a significant excess of sisters. Like previous studies of gender dysphoric youth and adults, these findings were consistent with the fraternal birth order effect. In addition, the greater frequency of only children and elevated numbers of older sisters among the homosexual female group adds to a small literature on sibship characteristics of potential relevance to the development of gender identity and sexual orientation in females.

  4. Birth Order and Sibling Sex Ratio of Children and Adolescents Referred to a Gender Identity Service

    PubMed Central

    VanderLaan, Doug P.; Blanchard, Ray; Wood, Hayley; Zucker, Kenneth J.

    2014-01-01

    In adult male samples, homosexuality is associated with a preponderance of older brothers (i.e., the fraternal birth order effect). In several studies comparing gender dysphoric youth, who are likely to be homosexual in adulthood, to clinical or non-clinical control groups, the findings have been consistent with the fraternal birth order effect in males; however, less is known about unique sibship characteristics of gender dysphoric females. The current study investigated birth order and sibling sex ratio in a large sample of children and adolescents referred to the same Gender Identity Service (N = 768). Probands were classified as heterosexual males, homosexual males, or homosexual females based on clinical diagnostic information. Groups differed significantly in age and sibship size, and homosexual females were significantly more likely to be only children. Subsequent analyses controlled for age and for sibship size. Compared to heterosexual males, homosexual males had a significant preponderance of older brothers and homosexual females had a significant preponderance of older sisters. Similarly, the older sibling sex ratio of homosexual males showed a significant excess of brothers whereas that of homosexual females showed a significant excess of sisters. Like previous studies of gender dysphoric youth and adults, these findings were consistent with the fraternal birth order effect. In addition, the greater frequency of only children and elevated numbers of older sisters among the homosexual female group adds to a small literature on sibship characteristics of potential relevance to the development of gender identity and sexual orientation in females. PMID:24651045

  5. Manipulation of offspring sex ratio by second-mated female house wrens.

    PubMed Central

    Albrecht, Daniel J; Johnson, L Scott

    2002-01-01

    In 1973, Trivers and Willard proposed that offspring sex ratio should be associated with the quality of parental care likely to be provided to the offspring. We tested this hypothesis by comparing fledgling sex ratios in nests of first- and second-mated female house wrens (Troglodytes aedon). In our Wyoming population, second-mated females typically receive little or no male parental assistance and fledge fewer and lower-quality young compared with first-mated females. Assuming that being of lower quality has stronger negative effects on the future reproductive success of males than that of females in this polygynous population, we predicted that fledgling sex ratios in the nests of second-mated females would be female-biased compared with the fledgling sex ratios of first-mated females. Additionally, we asked whether any sex bias at fledging could have resulted from male-biased nestling mortality caused by sex-biased parental provisioning. As predicted, mean fledgling sex ratios in nests of second-mated females were more female-biased than fledgling sex ratios in nests of first-mated females. However, we found no evidence of either sex-biased nestling mortality or sex-biased parental provisioning. These findings suggest that females are responding to their status as second-mated females and to the associated low-quality parental care that their young are likely to receive by producing female-biased clutches rather than manipulating the offspring sex ratio through sex-biased nestling mortality. PMID:11886637

  6. Fertility transition and adverse child sex ratio in districts of India.

    PubMed

    Mohanty, Sanjay K; Rajbhar, Mamta

    2014-11-01

    Demographic research in India over the last two decades has focused extensively on fertility change and gender bias at the micro-level, and less has been done at the district level. Using data from the Census of India 1991-2011 and other sources, this paper shows the broad pattern of fertility transition and trends in the child sex ratio in India, and examines the determinants of the child sex ratio at the district level. During 1991-2011, while the Total Fertility Rate (TFR) declined by 1.2 children per woman, the child sex ratio fell by 30 points in the districts of India. However, the reduction in fertility was slower in the high-fertility compared with the low-fertility districts. The gender differential in under-five mortality increased in many districts of India over the study period. The decline in the child sex ratio was higher in the transitional compared with the low-fertility districts. The transitional districts are at higher risk of a low child sex ratio due to an increased gender differential in mortality and increase in the practice of sex-selective abortions. The sex ratio at birth and gender differential in mortality explains one-third of the variation, while region alone explains a quarter of the variation in the child sex ratio in the districts of India.

  7. The Maternal Legacy: Female Identity Predicts Offspring Sex Ratio in the Loggerhead Sea Turtle

    PubMed Central

    Reneker, Jaymie L.; Kamel, Stephanie J.

    2016-01-01

    In organisms with temperature-dependent sex determination, the incubation environment plays a key role in determining offspring sex ratios. Given that global temperatures have warmed approximately 0.6 °C in the last century, it is necessary to consider how organisms will adjust to climate change. To better understand the degree to which mothers influence the sex ratios of their offspring, we use 24 years of nesting data for individual female loggerhead sea turtles (Caretta caretta) observed on Bald Head Island, North Carolina. We find that maternal identity is the best predictor of nest sex ratio in univariate and multivariate predictive models. We find significant variability in estimated nest sex ratios among mothers, but a high degree of consistency within mothers, despite substantial spatial and temporal thermal variation. Our results suggest that individual differences in nesting preferences are the main driver behind divergences in nest sex ratios. As such, a female’s ability to plastically adjust her nest sex ratios in response to environmental conditions is constrained, potentially limiting how individuals behaviorally mitigate the effects of environmental change. Given that many loggerhead populations already show female-biased offspring sex ratios, understanding maternal behavioral responses is critical for predicting the future of long-lived species vulnerable to extinction. PMID:27363786

  8. Social Roles Contribute to Age and Sex Stereotypes.

    ERIC Educational Resources Information Center

    Turner, Barbara Formaniak; And Others

    The purpose of this study was to test hypotheses drawn from the social role model about the process that people use in deciding what other people are like, focusing on the difference that other people's age, race, and sex make. A sample of non-Latino White students (N=671) ranging in age from 18 to 81 years used the Bem Sex-Role Inventory (BSRI)…

  9. Pollination intensity influences sex ratios in dioecious Rumex nivalis, a wind-pollinated plant.

    PubMed

    Stehlik, Ivana; Barrett, Spencer C H

    2006-06-01

    Determining the mechanisms governing sex-ratio variation in dioecious organisms represents a central problem in evolutionary biology. It has been proposed that in plants with sex chromosomes competition between pollen tubes of female- versus male-determining microgametophytes (certation) causes female-biased primary sex ratios. Experimental support for this hypothesis is limited and recent workers have cast doubt on whether pollen-tube competition can modify sex ratios in dioecious plants. Here we investigate the influence of variation in pollination intensity on sex ratios in Rumex nivalis, a wind-pollinated alpine herb with strongly female-biased sex ratios. In a garden experiment, we experimentally manipulated pollination intensity using three concentric rings of female recipient plants at different distances from a central group of male pollen donors. This design enabled us to test the hypothesis that increasing pollen load size, by intensifying gametophyte competition, promotes female-biased sex ratios in R. nivalis. We detected a significant decline in pollen load at successive distance classes with concomitant reductions in seed set. Sex ratios of progeny were always female biased, but plants at the closest distance to male donors exhibited significantly greater female bias than more distant plants. The amount of female bias was positively correlated with the seed set of inflorescences. Hand pollination of stigmas resulted in approximately 100-fold higher stigmatic pollen loads than wind-pollinated stigmas and produced exceptionally female-biased progenies (female frequency = 0.96). Our results are the first to demonstrate a functional relation between stigmatic pollen capture, seed set, and sex ratio and suggest that certation can contribute towards female-biased sex ratios in dioecious plants.

  10. Joint evolution of sex ratio and reproductive group size under local mate competition with inbreeding depression.

    PubMed

    Yamauchi, Atsushi; Kobayashi, Yutaka

    2011-02-07

    Local mate competition (LMC) may involve some amount of inbreeding between siblings. Because sib-mating is generally accompanied by inbreeding depression, natural selection may favor a reduced rate of sib-mating, possibly affecting the evolution of sex ratio and reproductive group size. The present study theoretically investigated the evolution of these traits under LMC in the presence of inbreeding depression. When the reproductive group size evolves, the determination mechanism of sex ratio is important because the timescale of the sex ratio response to reproductive group size can affect the evolutionary process. We consider a spectrum of sex ratio determination mechanisms from purely unconditional to purely conditional, including intermediate modes with various relative strengths of unconditional and conditional effects. This analysis revealed that both the evolutionarily stable reproductive group size and ratio of males increase with higher inbreeding depression and with a larger relative strength of an unconditional effect in sex ratio determination. Unexpectedly, when the sex ratio is controlled purely conditionally, the reproductive group size cannot exceed three even under the severest level of inbreeding depression (i.e., lethal effect). The present study reveals the conditions for LMC to evolve through the analysis of the joint evolution of reproductive group size and sex ratio.

  11. 76 FR 80966 - Agency Information Collection Activities; Proposed Collection: Age, Sex, and Race of Persons...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-27

    ... Federal Bureau of Investigation Agency Information Collection Activities; Proposed Collection: Age, Sex, and Race of Persons Arrested 18 Years of Age and Over; Age, Sex, and Race of Persons Arrested Under 18... the form/collection: Age, Sex, and Race of Persons Arrested 18 Years of Age and Over; Age, Sex,...

  12. Experimental evolution of reduced sex ratio adjustment under local mate competition.

    PubMed

    Macke, Emilie; Magalhães, Sara; Bach, Fabien; Olivieri, Isabelle

    2011-11-25

    Theory predicts that local mate competition (LMC) favors the evolution of female-biased sex ratios. Empirical support of this prediction is indirect and comes from comparative studies or from studies showing that individuals can adjust their offspring sex ratio in response to varying LMC intensities. Replicate lines from a population of the spider mite Tetranychus urticae were selected under three LMC intensities for up to 54 generations. Within each selection regime, the final sex ratio matched theoretical predictions. Furthermore, the ability of individuals to adjust their offspring sex ratio diminished in females evolving under strict LMC, but not in females evolving under relaxed LMC levels. These results provide direct experimental evidence for the evolutionary process by which LMC modifies sex-allocation strategies and suggest that evolution under strict and constant LMC may lead to a loss of phenotypic plasticity.

  13. Female philopatry in a heterogeneous environment: ordinary conditions leading to extraordinary ESS sex ratios

    PubMed Central

    Hulin, Vincent; Guillon, Jean-Michel

    2007-01-01

    Background We use a simulation-based model to study the impact of female philopatry and heterogeneity of habitat quality on the evolution of primary sex ratio. Results We show that these conditions may lead to strongly biased ESS habitat-dependent sex ratios, under two kinds of density-dependent population regulation. ESS sex ratios are always biased towards females in good habitats, towards males in poor habitats, and are generally equilibrated considering the whole population. Noticeably, the predicted bias of sex ratio usually increases with decreasing female philopatry. Conclusion The selection forces responsible for these results are fully described. This study provides a new perspective on the evolutionary significance of temperature sex determination. We discuss the case of turtles by comparing our theoretical results with field observations. PMID:17284311

  14. Age and sex differences in the risk of causing vehicle collisions in Spain, 1990 to 1999.

    PubMed

    Claret, Pablo Lardelli; Castillo, Juan de Dios Luna del; Moleón, José Juan Jiménez; Cavanillas, Aurora Bueno; Martín, Miguel García; Vargas, Ramón Gálvez

    2003-03-01

    This retrospective, paired case-control study was designed to estimate crude and adjusted effects of age and sex on the risk of causing collisions between vehicles with four or more wheels in Spain during the period from 1990 to 1999. We selected all 220284 collisions registered from 1990 to 1999 in the Spanish Dirección General de Tráfico (DGT) traffic crash database in which only one driver committed any infraction. Information was collected about age, sex and several confounding factors for both the responsible and paired-by-collision nonresponsible drivers. Crude and adjusted odds ratios (aORs) were calculated for each age and sex category. For men, the lowest risk was seen for drivers aged 25-49 years. Below the age of 35 years the crude odds ratio (cOR) was highest in the 18-24-year-old group (1.61; CI: 1.57-1.65). The risk increased significantly and exponentially after the age of 50 years, to a maximum odds ratio of 3.71 (3.43-4.00) for drivers aged >74 years. In women, the lowest risk values were found for the 25-44-year-old age group. In older women the risk increased significantly with age to a maximum odds ratio of 3.02 (2.31-3.97) in the oldest age group. aOR estimates tended to be lower than crude estimates for drivers younger than 40 years of age, but the opposite was seen for drivers 40 years old and older. Regarding sex differences, among younger drivers crude and aORs for men were higher than for women. Our results suggest that the risk of causing a collision between vehicles with four or more wheels is directly dependent on the driver's age.

  15. Estimating age: college males versus convicted male child sex offenders.

    PubMed

    Marsh, Robert; Romero, Sergio; Patrick, Steven

    2013-01-01

    Two samples, male college students and convicted male child sex offenders, are compared on their abilities to accurately estimate the age group of a series of photographs of a sole female ranging in age from 11 to 29. Both samples tend to overestimate the age group of the subject photos, and no significant difference was found between college students and convicted child sex offenders in their ability to estimate the age of females. Both groups are compared demographically, and only limited differences were found. The implications are discussed in regard to theory and prevention of child sexual abuse.

  16. More Women Than Men: Implications of the Changing Sex Ratio.

    ERIC Educational Resources Information Center

    Skrabanek, R. L.

    Texas, like the rest of the nation, is undergoing a shift toward an excess of females. Review of the changing balance of the sexes reveals that there were only 95.9 males per 100 females in 1970 with a projected drop to 93.8 by 1980. In 1950 Texas had an excess of 15,000 males, but by 1960 females outnumbered males by 90,000 and by 234,000 in…

  17. Rainfall-driven sex-ratio genes in African buffalo suggested by correlations between Y-chromosomal haplotype frequencies and foetal sex ratio

    PubMed Central

    2010-01-01

    Background The Y-chromosomal diversity in the African buffalo (Syncerus caffer) population of Kruger National Park (KNP) is characterized by rainfall-driven haplotype frequency shifts between year cohorts. Stable Y-chromosomal polymorphism is difficult to reconcile with haplotype frequency variations without assuming frequency-dependent selection or specific interactions in the population dynamics of X- and Y-chromosomal genes, since otherwise the fittest haplotype would inevitably sweep to fixation. Stable Y-chromosomal polymorphism due one of these factors only seems possible when there are Y-chromosomal distorters of an equal sex ratio, which act by negatively affecting X-gametes, or Y-chromosomal suppressors of a female-biased sex ratio. These sex-ratio (SR) genes modify (suppress) gamete transmission in their own favour at a fitness cost, allowing for stable polymorphism. Results Here we show temporal correlations between Y-chromosomal haplotype frequencies and foetal sex ratios in the KNP buffalo population, suggesting SR genes. Frequencies varied by a factor of five; too high to be alternatively explained by Y-chromosomal effects on pregnancy loss. Sex ratios were male-biased during wet and female-biased during dry periods (male proportion: 0.47-0.53), seasonally and annually. Both wet and dry periods were associated with a specific haplotype indicating a SR distorter and SR suppressor, respectively. Conclusions The distinctive properties suggested for explaining Y-chromosomal polymorphism in African buffalo may not be restricted to this species alone. SR genes may play a broader and largely overlooked role in mammalian sex-ratio variation. PMID:20416038

  18. Inferences about ungulate population dynamics derived from age ratios

    USGS Publications Warehouse

    Harris, N.C.; Kauffman, M.J.; Mills, L.S.

    2008-01-01

    Age ratios (e.g., calf:cow for elk and fawn:doe for deer) are used regularly to monitor ungulate populations. However, it remains unclear what inferences are appropriate from this index because multiple vital rate changes can influence the observed ratio. We used modeling based on elk (Cervus elaphus) life-history to evaluate both how age ratios are influenced by stage-specific fecundity and survival and how well age ratios track population dynamics. Although all vital rates have the potential to influence calf:adult female ratios (i.e., calf:xow ratios), calf survival explained the vast majority of variation in calf:adult female ratios due to its temporal variation compared to other vital rates. Calf:adult female ratios were positively correlated with population growth rate (??) and often successfully indicated population trajectories. However, calf:adult female ratios performed poorly at detecting imposed declines in calf survival, suggesting that only the most severe declines would be rapidly detected. Our analyses clarify that managers can use accurate, unbiased age ratios to monitor arguably the most important components contributing to sustainable ungulate populations, survival rate of young and ??. However, age ratios are not useful for detecting gradual declines in survival of young or making inferences about fecundity or adult survival in ungulate populations. Therefore, age ratios coupled with independent estimates of population growth or population size are necessary to monitor ungulate population demography and dynamics closely through time.

  19. Effects of mating dynamics and crowding on sex ratio variance in mice.

    PubMed

    Krackow, S

    1997-05-01

    Mating units of six virgin females and one adult stud male were established to test for the effects of timing of mating and crowding of pregnant females on litter sex ratios in mice. Females either copulated during periods when no other female of the mating unit copulated simultaneously (single mating condition) or when more than one female copulated (multiple matings condition). Two crowding conditions were imposed on the animals: the females of 14 mating units were placed into individual cages after mating (isolated condition), while females of the other 13 mating units remained in the original group until shortly before littering (crowded condition). Sex ratio variance did not deviate from random expectation in litters arising from the multiple matings periods. However, in litters arising from single mating periods, extreme sex ratios were found significantly less frequently than expected by chance. Higher sex ratio variance in litters arising from multiple matings periods is attributed to the timing of mating being at higher variance under this condition, which is known to affect sex ratios in other rodents. Crowding significantly reduced sex ratio variance further. Reduced sex ratio variance under single mating and crowded conditions is speculated to follow from competition for resources between preimplantation embryos, which may be further increased by stressful effects of crowding. Loss of embryos after implantation appeared not to be responsible for the above effects.

  20. Sex ratio variation shapes the ecological effects of a globally introduced freshwater fish

    PubMed Central

    Fryxell, David C.; Arnett, Heather A.; Apgar, Travis M.; Kinnison, Michael T.; Palkovacs, Eric P.

    2015-01-01

    Sex ratio and sexual dimorphism have long been of interest in population and evolutionary ecology, but consequences for communities and ecosystems remain untested. Sex ratio could influence ecological conditions whenever sexual dimorphism is associated with ecological dimorphism in species with strong ecological interactions. We tested for ecological implications of sex ratio variation in the sexually dimorphic western mosquitofish, Gambusia affinis. This species causes strong pelagic trophic cascades and exhibits substantial variation in adult sex ratios. We found that female-biased populations induced stronger pelagic trophic cascades compared with male-biased populations, causing larger changes to key community and ecosystem responses, including zooplankton abundance, phytoplankton abundance, productivity, pH and temperature. The magnitude of such effects indicates that sex ratio is important for mediating the ecological role of mosquitofish. Because both sex ratio variation and sexual dimorphism are common features of natural populations, our findings should encourage broader consideration of the ecological significance of sex ratio variation in nature, including the relative contributions of various sexually dimorphic traits to these effects. PMID:26490793

  1. Developmental sexual dimorphism and the evolution of mechanisms for adjustment of sex ratios in mammals.

    PubMed

    Cameron, Elissa Z; Edwards, Amy M; Parsley, Laura M

    2017-02-01

    Sex allocation theory predicts biased offspring sex ratios in relation to local conditions if they would maximize parental lifetime reproductive return. In mammals, the extent of the birth sex bias is often unpredictable and inconsistent, leading some to question its evolutionary significance. For facultative adjustment of sex ratios to occur, males and females would need to be detectably different from an early developmental stage, but classic sexual dimorphism arises from hormonal influences after gonadal development. Recent advances in our understanding of early, pregonadal sexual dimorphism, however, indicate high levels of dimorphism in gene expression, caused by chromosomal rather than hormonal differences. Here, we discuss how such dimorphism would interact with and link previously hypothesized mechanisms for sex-ratio adjustment. These differences between males and females are sufficient for offspring sex both to be detectable to parents and to provide selectable cues for biasing sex ratios from the earliest stages. We suggest ways in which future research could use the advances in our understanding of sexually dimorphic developmental physiology to test the evolutionary significance of sex allocation in mammals. Such an approach would advance our understanding of sex allocation and could be applied to other taxa.

  2. The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos

    PubMed Central

    Labbé, L.

    2016-01-01

    Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates. PMID:27928001

  3. Maternal Lineage of Warmblood Mares Contributes to Variation of Gestation Length and Bias of Foal Sex Ratio.

    PubMed

    Kuhl, J; Stock, K F; Wulf, M; Aurich, C

    2015-01-01

    Maternal lineage influences performance traits in horses. This is probably caused by differences in mitochondrial DNA (mtDNA) transferred to the offspring via the oocyte. In the present study, we investigated if reproductive traits with high variability-gestation length and fetal sex ratio-are influenced by maternal lineage. Data from 142 Warmblood mares from the Brandenburg State Stud at Neustadt (Dosse), Germany, were available for the study. Mares were grouped according to their maternal lineage. Influences on the reproduction parameters gestation length and sex ratio of offspring were analyzed by simple and multiple analyses of variance. A total of 786 cases were included. From the 142 mares, 119 were assigned to six maternal lineages with n≥10 mares per lineage, and 23 mares belonged to smaller maternal lineages. The mean number of live foals produced per mare was 4.6±3.6 (±SD). Live foal rate was 83.5%. Mean gestation length was 338.5±8.9 days (±SD) with a range of 313 to 370 days. Gestation length was affected by maternal lineage (p<0.001). Gestation length was also significantly influenced by the individual mare, age of the mare, year of breeding, month of breeding and sex of the foal (p<0.05). Of the 640 foals born alive at term, 48% were male and 52% female. Mare age group and maternal lineage significantly influenced the sex ratio of the foals (p<0.05). It is concluded that maternal lineage influences reproductive parameters with high variation such as gestation length and foal sex ratio in horses. In young primiparous and aged mares, the percentage of female offspring is higher than the expected 1:1 ratio.

  4. Response of sex ratio to timing of breeding in the small cyprinid Gnathopogon caerulescens.

    PubMed

    Fujioka, Y; Kikko, T; Saegusa, J; Usuki, T; Ohtsuka, T

    2015-10-01

    The influence of hatching date on the sex ratio of wild Gnathopogon caerulescens was examined. Cohorts reared from eggs collected in the early and middle parts of the spawning season showed almost balanced sex ratios, with female bias in some cohorts. Cohorts born later in the season mostly displayed male bias, and the mean proportion of males later in the season was significantly higher than in early- and mid-season cohorts. These results indicate that the sex ratio of G. caerulescens changes with the time of breeding, increasing along with the ambient water temperature of the lake.

  5. Human sex ratio at birth and residential proximity to nuclear facilities in France.

    PubMed

    Scherb, Hagen; Kusmierz, Ralf; Voigt, Kristina

    2016-04-01

    The possible detrimental genetic impact on humans living in the vicinity of nuclear facilities has been previously studied. We found evidence for an increase in the human secondary sex ratio (sex odds) within distances of up to 35km from nuclear facilities in Germany and Switzerland. Here, we extend our pilot investigations using new comprehensive data from France. The French data (1968-2011) account for 36,565 municipalities with 16,968,701 male and 16,145,925 female births. The overall sex ratio was 1.0510. Using linear and nonlinear logistic regression models with dummy variables coding for appropriately grouped municipalities, operation time periods, and corresponding spatiotemporal interactions, we consider the association between annual municipality-level birth sex ratios and minimum distances of municipalities from nuclear facilities. Within 35km from 28 nuclear sites in France, the sex ratio is increased relative to the rest of France with a sex odds ratio (SOR) of 1.0028, (95% CI: 1.0007, 1.0049). The detected association between municipalities' minimum distances from nuclear facilities and the sex ratio in France corroborates our findings for Germany and Switzerland.

  6. Sex ratio and sexual dimorphism of three lice species with contrasting prevalence parasitizing the house sparrow.

    PubMed

    Pap, Péter László; Adam, Costică; Vágási, Csongor István; Benkő, Zoltán; Vincze, Orsolya

    2013-02-01

    Female-biased sex ratio is a common phenomenon in parasites; however, the cause and consequence of the skewed sex ratio is less well known. Here, we studied the difference in sex ratio, a possible mechanism responsible for the development of unbalanced proportion of sexes and its consequences on sexual size dimorphism, between 3 louse species parasitizing the house sparrow Passer domesticus. Philopterus fringillae was more prevalent than Sturnidoecus refractariolus and Brueelia cyclothorax. As expected, the most common species, which was probably least affected by isolation and, hence, inbreeding, was characterized by a balanced sex ratio, whereas the 2 other species with low prevalence were significantly more female biased than expected on the basis of the local mate competition hypothesis. Further, in support of this notion, we found that P. fringillae infrapopulation size significantly, and positively, correlated with the sex ratio. Finally, we found significant differences in sexual dimorphism among the 3 louse species and, as expected, the relative size of males was smallest in species with a more female-biased sex ratio.

  7. Sex and Age Differences in the Endorsement of Sex Stereotypes Associated with Driving.

    PubMed

    Pravossoudovitch, Karyn; Martha, Cécile; Cury, François; Granié, Marie-Axelle

    2015-12-23

    Sex and age differences are particularly pronounced in car accidents. Current psychological research is exploring the relationship between risky driving and compliance with sex stereotypes, notably conformity with social expectations concerning masculinity. Some studies have already shown that sex stereotypes associated with driving (SSAD) may influence driving behaviors. The aim of this research was to explore the participants' sex and age differences in SSAD endorsement. A questionnaire was developed and validated on four dimensions of SSAD: male's driving skills and female's compliance with traffic rules, courtesy behind the wheel, and risk avoidance in driving. SSAD endorsement was measured for 291 licensed drivers from 18 to 64 years of age. Results revealed that females endorsed the female's risk avoidance stereotype more (p < .05), whereas males endorsed the male drivers (driving skills) stereotype more (p < .05). Results also revealed that the endorsement of male's driving skills decreases with age (p < .01) and the endorsement of female's courtesy increases with age among all participants (p = .01), while the endorsement of female's compliance with traffic rules increases with age only among female participants (p < .05). The results are discussed in terms of in-group/out-group relations and sex and age differences.

  8. Skewed sex ratios at birth and future marriage squeeze in China and India, 2005-2100.

    PubMed

    Guilmoto, Christophe Z

    2012-02-01

    I examine the potential impact of the anticipated future marriage squeeze on nuptiality patterns in China and India during the twenty-first century. I use population projections from 2005 to 2100 based on three different scenarios for the sex ratio at birth (SRB). To counteract the limitations of cross-sectional methods commonly used to assess the severity of marriage squeezes, I use a two-sex cohort-based procedure to simulate marriage patterns over the twenty-first century based on the female dominance model. I also examine two more-flexible marriage functions to illustrate the potential impact of changes in marriage schedules as a response to the marriage squeeze. Longitudinal indicators of marriage squeeze indicate that the number of prospective grooms in both countries will exceed that of prospective brides by more 50% for three decades in the most favorable scenario. Rates of male bachelorhood will not peak before 2050, and the squeeze conditions will be felt several decades thereafter, even among cohorts unaffected by adverse SRB. If the SRB is allowed to return to normalcy by 2020, the proportion of men unmarried at age 50 is expected to rise to 15% in China by 2055 and to 10% in India by 2065. India suffers from the additional impact of a delayed fertility transition on its age structures.

  9. Sex ratios, bill deformities, and PCBs in nestling double-crested cormorants

    SciTech Connect

    Stromborg, K.L.; Sileo, L.; Tuinen, P. van

    1995-12-31

    Deformed double-crested cormorant (Phalacrocorax auritus) nestlings examined from 1988--1992 had a sex ratio highly skewed toward females (66 of 81) compared to normal nestlings (43 of 80) (P < 0.005). The collection site, Green Bay, WI, is heavily contaminated with PCBs and the possibility of gender alteration was investigated in a designed study by comparing the sex of nestling birds determined using three techniques. These nestlings were collected at five sites, both contaminated and uncontaminated. Genetic sex was determined by cytogenetic techniques and phenotypic sex was determined by macroscopic and histologic examination of gonads. Differences between techniques resulted in a few instances of classifying genetic males as females by one or the other gonadal examinations. Sex ratios of the nestlings from the five sites were compared to binomial distributions assuming equal probabilities of males and females. Sex ratios of normal nestlings were not different from expected regardless of sex determination technique (P > 0.10). Deformed nestlings sexed cytogenetically or histologically did not differ from expected (P > 0.40), but deformed nestlings tended to be classified , macroscopically as females at a higher rate than expected (P = 0.092). The observed sex ratios obtained by macroscopic techniques did not differ between the 1968--1992 observational study and the designed study (P > 0.50). Histologic examination suggested two explanations for the skewed sex ratio: nestlings with undeterminable macroscopic sex usually had testes and, some gonads which grossly resembled ovaries were, in fact, testes. If phenotypic gender alteration is present in these birds, it is more evident at the gross structural level than at the histologic level.

  10. Naked at Our Age: Talking out Loud about Senior Sex

    ERIC Educational Resources Information Center

    Davis, Melanie

    2012-01-01

    "Naked at Our Age" is an excellent resource for sexually interested and/or active adults over the age of 60. The book combines the author's personal reflections, questions and stories shared by older adults, and advice from sex therapists, sexuality educators, the author, and health care providers. The breadth of topics makes the book useful to…

  11. Sex and Age Differences in Future Temporal Perspective.

    ERIC Educational Resources Information Center

    Grant, Edward; Sawler, Joyce

    This study explored sex differences in the Future Temporal Perspectives (FTP) of children. The influences of age, social class and intelligence were also investigated, or FTP was generally believed to be affected by them. Subjects were 96 boys and 96 girls, selected from 26 schools in Nova Scotia, from three age groups: 9.6-11.0, 12.0-13.6, and…

  12. Under what conditions do climate-driven sex ratios enhance versus diminish population persistence?

    PubMed Central

    Boyle, Maria; Hone, Jim; Schwanz, Lisa E; Georges, Arthur

    2014-01-01

    For many species of reptile, crucial demographic parameters such as embryonic survival and individual sex (male or female) depend on ambient temperature during incubation. While much has been made of the role of climate on offspring sex ratios in species with temperature-dependent sex determination (TSD), the impact of variable sex ratio on populations is likely to depend on how limiting male numbers are to female fecundity in female-biased populations, and whether a climatic effect on embryonic survival overwhelms or interacts with sex ratio. To examine the sensitivity of populations to these interacting factors, we developed a generalized model to explore the effects of embryonic survival, hatchling sex ratio, and the interaction between these, on population size and persistence while varying the levels of male limitation. Populations with TSD reached a greater maximum number of females compared to populations with GSD, although this was often associated with a narrower range of persistence. When survival depended on temperature, TSD populations persisted over a greater range of temperatures than GSD populations. This benefit of TSD was greatly reduced by even modest male limitation, indicating very strong importance of this largely unmeasured biologic factor. Finally, when males were not limiting, a steep relationship between sex ratio and temperature favoured population persistence across a wider range of climates compared to the shallower relationships. The opposite was true when males were limiting – shallow relationships between sex ratio and temperature allowed greater persistence. The results highlight that, if we are to predict the response of populations with TSD to climate change, it is imperative to 1) accurately quantify the extent to which male abundance limits female fecundity, and 2) measure how sex ratios and peak survival coincide over climate. PMID:25512848

  13. Under what conditions do climate-driven sex ratios enhance versus diminish population persistence?

    PubMed

    Boyle, Maria; Hone, Jim; Schwanz, Lisa E; Georges, Arthur

    2014-12-01

    For many species of reptile, crucial demographic parameters such as embryonic survival and individual sex (male or female) depend on ambient temperature during incubation. While much has been made of the role of climate on offspring sex ratios in species with temperature-dependent sex determination (TSD), the impact of variable sex ratio on populations is likely to depend on how limiting male numbers are to female fecundity in female-biased populations, and whether a climatic effect on embryonic survival overwhelms or interacts with sex ratio. To examine the sensitivity of populations to these interacting factors, we developed a generalized model to explore the effects of embryonic survival, hatchling sex ratio, and the interaction between these, on population size and persistence while varying the levels of male limitation. Populations with TSD reached a greater maximum number of females compared to populations with GSD, although this was often associated with a narrower range of persistence. When survival depended on temperature, TSD populations persisted over a greater range of temperatures than GSD populations. This benefit of TSD was greatly reduced by even modest male limitation, indicating very strong importance of this largely unmeasured biologic factor. Finally, when males were not limiting, a steep relationship between sex ratio and temperature favoured population persistence across a wider range of climates compared to the shallower relationships. The opposite was true when males were limiting - shallow relationships between sex ratio and temperature allowed greater persistence. The results highlight that, if we are to predict the response of populations with TSD to climate change, it is imperative to 1) accurately quantify the extent to which male abundance limits female fecundity, and 2) measure how sex ratios and peak survival coincide over climate.

  14. Maternal Lineage of Warmblood Mares Contributes to Variation of Gestation Length and Bias of Foal Sex Ratio

    PubMed Central

    Kuhl, J.; Stock, K. F.; Wulf, M.; Aurich, C.

    2015-01-01

    Maternal lineage influences performance traits in horses. This is probably caused by differences in mitochondrial DNA (mtDNA) transferred to the offspring via the oocyte. In the present study, we investigated if reproductive traits with high variability—gestation length and fetal sex ratio—are influenced by maternal lineage. Data from 142 Warmblood mares from the Brandenburg State Stud at Neustadt (Dosse), Germany, were available for the study. Mares were grouped according to their maternal lineage. Influences on the reproduction parameters gestation length and sex ratio of offspring were analyzed by simple and multiple analyses of variance. A total of 786 cases were included. From the 142 mares, 119 were assigned to six maternal lineages with n≥10 mares per lineage, and 23 mares belonged to smaller maternal lineages. The mean number of live foals produced per mare was 4.6±3.6 (±SD). Live foal rate was 83.5%. Mean gestation length was 338.5±8.9 days (±SD) with a range of 313 to 370 days. Gestation length was affected by maternal lineage (p<0.001). Gestation length was also significantly influenced by the individual mare, age of the mare, year of breeding, month of breeding and sex of the foal (p<0.05). Of the 640 foals born alive at term, 48% were male and 52% female. Mare age group and maternal lineage significantly influenced the sex ratio of the foals (p<0.05). It is concluded that maternal lineage influences reproductive parameters with high variation such as gestation length and foal sex ratio in horses. In young primiparous and aged mares, the percentage of female offspring is higher than the expected 1:1 ratio. PMID:26436555

  15. Can environmental or occupational hazards alter the sex ratio at birth? A systematic review

    PubMed Central

    Terrell, Metrecia L.; Hartnett, Kathleen P.; Marcus, Michele

    2011-01-01

    More than 100 studies have examined whether environmental or occupational exposures of parents affect the sex ratio of their offspring at birth. For this review, we searched Medline and Web of Science using the terms ‘sex ratio at birth’ and ‘sex ratio and exposure’ for all dates, and reviewed bibliographies of relevant studies to find additional articles. This review focuses on exposures that have been the subject of at least four studies including polychlorinated biphenyls (PCBs), dioxins, pesticides, lead and other metals, radiation, boron, and g-forces. For paternal exposures, only dioxins and PCBs were consistently associated with sex ratios higher or lower than the expected 1.06. Dioxins were associated with a decreased proportion of male births, whereas PCBs were associated with an increased proportion of male births. There was limited evidence for a decrease in the proportion of male births after paternal exposure to DBCP, lead, methylmercury, non-ionizing radiation, ionizing radiation treatment for childhood cancer, boron, or g-forces. Few studies have found higher or lower sex ratios associated with maternal exposures. Studies in humans and animals have found a reduction in the number of male births associated with lower male fertility, but the mechanism by which environmental hazards might change the sex ratio has not yet been established. PMID:24149027

  16. Sex ratio of White Stork Ciconia ciconia in different environments of Poland.

    PubMed

    Kamiński, Piotr; Grochowska, Ewa; Mroczkowski, Sławomir; Jerzak, Leszek; Kasprzak, Mariusz; Koim-Puchowska, Beata; Woźniak, Alina; Ciebiera, Olaf; Markulak, Damian

    2015-09-01

    The aim of this study was to analyze the variation in sex ratio of White Stork Ciconia ciconia chicks from differentiated Poland environments. We took under a consideration the impact of Cd and Pb for establish differences among sex ratio in chicks. We also study multiplex PCR employment for establish gender considerations. We collected blood samples via venipuncture of brachial vein of chicks during 2006-2008 breeding seasons at the Odra meadows (SW-Poland; control), which were compared with those from suburbs (SW-Poland), and from copper smelter (S-Poland; polluted) and from swamps near Baltic Sea. We found differences among sex ratio in White Stork chicks from types of environment. Male participation in sex structure is importantly higher in each type of environment excluded suburban areas. Differences in White Stork sex ratio according to the degree of environmental degradation expressed by Cd and Pb and sex-environment-metal interactions testify about the impact of these metals upon sex ratios in storks. Simultaneously, as a result of multiplex PCR, 18S ribosome gene, which served as internal control of PCR, was amplified in male and female storks. It means that it is possible to use primers designed for chicken in order to replicate this fragment of genome in White Stork. Moreover, the use of Oriental White Stork Ciconia boyciana W- chromosome specific primers makes it possible to determine the sex of C. ciconia chicks. Many factors make sex ratio of White Stork changes in subsequent breeding seasons, which depend significantly on specific environmental parameters that shape individual detailed defense mechanisms.

  17. Food item use by coyote sex and age classes

    SciTech Connect

    Cypher, B.L.; Spencer, K.A.; Scrivner, J.H.

    1995-10-01

    Food item use by coyotes was compared between sexes and among age classes at the Naval Petroleum Reserves, California. Item use did not differ significantly between males and females. Although leporid was the item most frequently used by all age classes, item use differed significantly between pups (< 1 year), yearlings (1 year), and adults (> 1 year), probably due to differential use of secondary items. Variation in item use among age classes could potentially bias results of coyote food habit studies.

  18. Age-dependent association between sex and renal cell carcinoma mortality: a population-based analysis.

    PubMed

    Qu, Yuanyuan; Chen, Haitao; Gu, Weijie; Gu, Chengyuan; Zhang, Hailiang; Xu, Jianfeng; Zhu, Yao; Ye, Dingwei

    2015-03-17

    Research on sex differences in renal cancer-specific mortality (RCSM), which considered the sex effect to be constant throughout life, has yielded conflicting results. This study hypothesized the sex effect may be modified by age, which is a proxy for hormonal status. Data from the Surveillance, Epidemiology and End Results database (1988-2010) were used to identify 114,539 patients with renal cell carcinoma (RCC). The study cohort was divided into three age groups using cutoffs of 42 and 58 years, which represent the premenopausal and postmenopausal periods. The cumulative incidence function and competing risks analyses were used to examine the effect of covariates on RCSM and other-cause mortality (OCM). In premenopausal period, male sex was a significant predictor of poor RCSM for both localized (adjusted subdistribution hazard ratio [aSHR] = 1.63, P = 0.002) and advanced (aSHR = 1.20, P = 0.041) disease. In postmenopausal period, the sex disparity diminished (aSHR = 1.05, P = 0.16) and reversed (aSHR = 0.95, P = 0.017) in localized and advanced disease, respectively. On the contrary, similar trend was not found for OCM across all age groups. Our results demonstrated the sex effect on RCSM was strongly modified by age. These findings may aid in clinical practice and need further evaluation of underlying biological mechanisms.

  19. Sex and Age Differences in the Risk Threshold for Delinquency

    PubMed Central

    Loeber, Rolf; Slotboom, Anne-Marie; Bijleveld, Catrien C. J. H.; Hipwell, Alison E.; Stepp, Stephanie D.; Koot, Hans M.

    2015-01-01

    This study examines sex differences in the risk threshold for adolescent delinquency. Analyses were based on longitudinal data from the Pittsburgh Youth Study (n = 503) and the Pittsburgh Girls Study (n = 856). The study identified risk factors, promotive factors, and accumulated levels of risks as predictors of delinquency and nondelinquency, respectively. The risk thresholds for boys and girls were established at two developmental stages (late childhood: ages 10–12 years, and adolescence: ages 13–16 years) and compared between boys and girls. Sex similarities as well as differences existed in risk and promotive factors for delinquency. ROC analyses revealed only small sex differences in delinquency thresholds, that varied by age. Accumulative risk level had a linear relationship with boys’ delinquency and a quadratic relationship with girls’ delinquency, indicating stronger effects for girls at higher levels of risk. PMID:23183920

  20. Geographical Variations in Sex Ratio Trends over Time in Multiple Sclerosis

    PubMed Central

    Trojano, Maria; Lucchese, Guglielmo; Graziano, Giusi; Taylor, Bruce V.; Simpson, Steve; Lepore, Vito; Grand’Maison, Francois; Duquette, Pierre; Izquierdo, Guillermo; Grammond, Pierre; Amato, Maria Pia; Bergamaschi, Roberto; Giuliani, Giorgio; Boz, Cavit; Hupperts, Raymond; Van Pesch, Vincent; Lechner-Scott, Jeannette; Cristiano, Edgardo; Fiol, Marcela; Oreja-Guevara, Celia; Saladino, Maria Laura; Verheul, Freek; Slee, Mark; Paolicelli, Damiano; Tortorella, Carla; D’Onghia, Mariangela; Iaffaldano, Pietro; Direnzo, Vita; Butzkueven, Helmut

    2012-01-01

    Background A female/male (F/M) ratio increase over time in multiple sclerosis (MS) patients was demonstrated in many countries around the world. So far, a direct comparison of sex ratio time-trends among MS populations from different geographical areas was not carried out. Objective In this paper we assessed and compared sex ratio trends, over a 60-year span, in MS populations belonging to different latitudinal areas. Methods Data of a cohort of 15,996 (F = 11,290; M = 4,706) definite MS with birth years ranging from 1930 to 1989 were extracted from the international MSBase registry and the New Zealand MS database. Gender ratios were calculated by six decades based on year of birth and were adjusted for the F/M born-alive ratio derived from the respective national registries of births. Results Adjusted sex ratios showed a significant increase from the first to the last decade in the whole MS sample (from 2.35 to 2.73; p = 0.03) and in the subgroups belonging to the areas between 83° N and 45° N (from 1.93 to 4.55; p<0.0001) and between 45° N to 35° N (from 1.46 to 2.30; p<0.05) latitude, while a sex ratio stability over time was found in the subgroup from areas between 12° S and 55° S latitude. The sex ratio increase mainly affected relapsing-remitting (RR) MS. Conclusions Our results confirm a general sex ratio increase over time in RRMS and also demonstrate a latitudinal gradient of this increase. These findings add useful information for planning case-control studies aimed to explore sex-related factors responsible for MS development. PMID:23133550

  1. Age and sex or gender (sex/gender) and HIV vaccine preparedness.

    PubMed

    Dhalla, Shayesta

    2015-10-29

    An examination of age and sex or gender (sex/gender) in HIV vaccine preparedness studies can contribute to an understanding of these demographic variables in preparation for actual HIV vaccine trials. In this descriptive review, age and sex or gender (sex/gender) were examined in relation to willingness to participate (WTP) and retention in an HIV vaccine trial. Twenty-five articles were retrieved from the Organization for Economic Co-operation and Development (OECD) countries and 28 articles were retrieved from the non-OECD countries. In US studies that involved mainly white MSM, older men were more likely to be WTP in a hypothetical HIV vaccine trial and more likely to be retained than younger men. In most OECD studies, sex/gender was not associated with WTP in a hypothetical HIV vaccine trial, while females were more likely to be retained in most studies. Largely, age was not associated with WTP in the non-OECD countries, but the results on sex/gender were more variable. The relationship between adolescent or adult WTP in hypothetical HIV vaccine trials in South Africa did not appear to be modified by high school student status. In addition, more studies in discordant couples in the context of HIV vaccine preparedness could be conducted to examine gender roles and inequalities in preparation for HIV vaccine trials.

  2. Age, breed, sex and seasonality as risk factors for equine laminitis.

    PubMed

    Polzer, J; Slater, M R

    1997-01-01

    A case-control study was conducted at the Texas Veterinary Medical Center between January 1, 1986 and December 31, 1991. Logistic regression was used to assess age, breed, sex, and seasonality as risk factors for equine laminitis. There were 70 acute cases, 183 chronic cases, and 779 controls. No statistical association was found between age, breed, sex, or seasonality and the diagnosis of acute laminitis. For chronic cases, the estimated odds ratio was statistically significant for age (OR = 1.05, 95% CI (1.02, 1.08)) and for the diagnosis of laminitis in the third quarter of the year (OR = 2.57, 95% CI (1.55, 4.25)) relative to the first quarter. There was no statistical association between breed or sex and chronic laminitis.

  3. Predicted sex ratio of juvenile Kemp's Ridley sea turtles captured near Steinhatchee, Florida

    USGS Publications Warehouse

    Geis, A.A.; Barichivich, W.J.; Wibbels, T.; Coyne, M.; Landry, A.M.; Owens, D.

    2005-01-01

    The Kemp's Ridley (Lepidochelys kempii) is one of the most endangered sea turtles in the world, and it possesses temperature-dependent sex determination (TSD). Sex ratios produced under TSD can vary widely and can affect the reproductive ecology of a population. Therefore, sex ratios produced from TSD are of ecological and conservation interest. The current study validated and utilized a testosterone radioimmunoassay (RIA) to examine the sex ratio of juvenile Kemp's Ridleys inhabiting the waters near Steinhatchee, Florida. Testosterone levels were measured in blood samples collected from juvenile Kemp's Ridleys captured over a three-year period. Results of this study indicate that a significant female bias (approximately 3.7:1) occurs in the aggregation of juvenile Kemp's Ridleys inhabiting the waters near Steinhatchee.

  4. Transgenerational plasticity mitigates the impact of global warming to offspring sex ratios.

    PubMed

    Donelson, Jennifer M; Munday, Philip L

    2015-08-01

    Global warming poses a threat to organisms with temperature-dependent sex determination because it can affect operational sex ratios. Using a multigenerational experiment with a marine fish, we provide the first evidence that parents developing from early life at elevated temperatures can adjust their offspring gender through nongenetic and nonbehavioural means. However, this adjustment was not possible when parents reproduced, but did not develop, at elevated temperatures. Complete restoration of the offspring sex ratio occurred when parents developed at 1.5 °C above the present-day average temperature for one generation. However, only partial improvement in the sex ratio occurred at 3.0 °C above average conditions, even after two generations, suggesting a limitation to transgenerational plasticity when developmental temperature is substantially increased. This study highlights the potential for transgenerational plasticity to ameliorate some impacts of climate change and that development from early life may be essential for expression of transgenerational plasticity in some traits.

  5. Trends in Triathlon Performance: Effects of Sex and Age.

    PubMed

    Lepers, Romuald; Knechtle, Beat; Stapley, Paul J

    2013-09-01

    The influences of sex and age upon endurance performance have previously been documented for both running and swimming. A number of recent studies have investigated how sex and age influence triathlon performance, a sport that combines three disciplines (swimming, cycling and running), with competitions commonly lasting between 2 (short distance: 1.5-km swim, 40-km cycle and 10-km run) and 8 h (Ironman distance: 3.8-km swim,180-km cycle and 42-km run) for elite triathletes. Age and sex influences upon performance have also been investigated for ultra-triathlons, with distances corresponding to several Ironman distances and lasting several days, and for off-road triathlons combining swimming, mountain biking and trail running. Triathlon represents an intriguing alternative model for analysing the effects of age and sex upon endurance and ultra-endurance ([6 h) performance because sex differences and age-related declines in performance can be analysed in the same individuals across the three separate disciplines. The relative participation of both females and masters athletes (age[40 years) in triathlon has increased consistently over the past 25 years. Sex differences in triathlon performance are also known to differ between the modes of locomotion adopted (swimming, cycling or running) for both elite and non-elite triathletes. Generally, time differences between sexes in swimming have been shown to be smaller on average than during cycling and running. Both physiological and morphological factors contribute to explaining these findings. Performance density (i.e. the time difference between the winner and tenth-placed competitor) has progressively improved (time differences have decreased) for international races over the past two decades for both males and females, with performance density now very similar for both sexes. For age-group triathletes, sex differences in total triathlon performance time increases with age. However,the possible difference in age

  6. The role of age-sex interaction in the development of post-herpetic neuralgia.

    PubMed

    Amicizia, Daniela; Domnich, Alexander; Arata, Lucia; Zoli, Daniela; Zotti, Carla Maria; Cacello, Elena; Gualano, Maria Rosaria; Gasparini, Roberto; Panatto, Donatella

    2017-02-01

    Post-herpetic neuralgia is the most frequent complication of herpes zoster and affects up to 30% of patients. Increased age is a well-recognized risk factor, while the role of gender is highly uncertain. Little research has been performed into a possible combined effect of age and sex in post-herpetic neuralgia. The objective of the study was to study the role of age and sex and their combined effect in the development of post-herpetic neuralgia. This retrospective study enrolled adult subjects with at least one episode of herpes zoster in the previous 10 y. A questionnaire on the patient's socio-demographic, anamnestic and clinical characteristics was administered by general practitioners. Multivariable logistic regression was used to detect relationships between post-herpetic neuralgia and age, sex and their interaction. Fifty-nine of 272 patients reported post-herpetic neuralgia: a prevalence of 21.7%. Subjects with post-herpetic neuralgia (mean age 70.9 years) were significantly older (P = .001) than those without (64.2 years), the standardised mean difference being 0.5; no significant between-sex association was revealed (P = .96). A fully adjusted multivariable logistic analysis, however, revealed a highly significant (P = .007) age-sex interaction, with an odds ratio of 0.92; this also showed that older males were more likely to report post-herpetic neuralgia than younger males, while no obvious age-associated pattern was observed among females. We discerned a significant age-by-sex interaction in the development of post-herpetic neuralgia, which suggests that the effect of age on the development of this condition may differ between men and women.

  7. The role of age-sex interaction in the development of post-herpetic neuralgia

    PubMed Central

    Cacello, Elena

    2017-01-01

    ABSTRACT Post-herpetic neuralgia is the most frequent complication of herpes zoster and affects up to 30% of patients. Increased age is a well-recognized risk factor, while the role of gender is highly uncertain. Little research has been performed into a possible combined effect of age and sex in post-herpetic neuralgia. The objective of the study was to study the role of age and sex and their combined effect in the development of post-herpetic neuralgia. This retrospective study enrolled adult subjects with at least one episode of herpes zoster in the previous 10 y. A questionnaire on the patient's socio-demographic, anamnestic and clinical characteristics was administered by general practitioners. Multivariable logistic regression was used to detect relationships between post-herpetic neuralgia and age, sex and their interaction. Fifty-nine of 272 patients reported post-herpetic neuralgia: a prevalence of 21.7%. Subjects with post-herpetic neuralgia (mean age 70.9 years) were significantly older (P = .001) than those without (64.2 years), the standardised mean difference being 0.5; no significant between-sex association was revealed (P = .96). A fully adjusted multivariable logistic analysis, however, revealed a highly significant (P = .007) age-sex interaction, with an odds ratio of 0.92; this also showed that older males were more likely to report post-herpetic neuralgia than younger males, while no obvious age-associated pattern was observed among females. We discerned a significant age-by-sex interaction in the development of post-herpetic neuralgia, which suggests that the effect of age on the development of this condition may differ between men and women. PMID:28215122

  8. Offspring sex ratio is related to paternal train elaboration and yolk corticosterone in peafowl.

    PubMed

    Pike, Thomas W; Petrie, Marion

    2005-06-22

    Several recent experimental studies have provided strong evidence for the ability of birds to manipulate the sex ratio of their offspring prior to laying. Using a captive population of peafowl (Pavo cristatus), we tested experimentally the effects of paternal attractiveness on offspring sex ratio, and related sex ratio deviations to egg-yolk concentrations of testosterone, 17beta-estradiol and corticosterone. When females were mated to males whose attractiveness had been experimentally reduced by removing prominent eyespot feathers from their trains, they produced significantly more female offspring, had significantly higher yolk corticosterone concentrations and tended to have lower levels of yolk testosterone than when mated to the same males with their full complement of feathers. Concentrations of 17beta-estradiol did not vary consistently with sex ratio biases. These findings add to the small number of studies providing experimental evidence that female birds can control the primary sex ratio of their offspring in response to paternal attractiveness, and highlight the possibility that corticosterone and perhaps testosterone are involved in the sex manipulation process in birds.

  9. Sex ratio estimation and survival analysis for Orthetrum coerulescens (Odonata, Libellulidae)

    USGS Publications Warehouse

    Kery, M.; Juillerat, L.

    2004-01-01

    There is controversy over whether uneven sex ratios observed in mature dragonfly populations are a mere artifact resulting from the higher observability of males. Previous studies have at best made indirect inference about sex ratios by analysis of survival or recapture rates. Here, we obtain direct estimates of sex ratio from capture?recapture data based on the Cormack?Jolly?Seber model. We studied Orthetrum coerulescens (Fabricius, 1798) at three sites in the Swiss Jura Mountains over an entire activity period. Recapture rates per 5-day interval were 3.5 times greater for males (0.67, SE 0.02) than for females (0.19, SE 0.02). At two sites, recapture rate increased over the season for males and was constant for females, and at one site it decreased with precipitation for both sexes. In addition, recapture rate was higher with higher temperature for males only. We found no evidence for higher male survival rates in any population. Survival per 5-day interval for both sexes was estimated to be 0.77 (95% CI 0.75?0.79) without significant site or time-specific variation. There were clear effects of temperature (positive) and precipitation (negative) on survival rate at two sites. Direct estimates of sex ratios were not significantly different from 1 for any time interval. Hence, the observed male-biased sex ratio in adult O. coerulescens was an artifact resulting from the better observability of males. The method presented in this paper is applicable to sex ratio estimation in any kind of animal.

  10. Evolutionary implications for the determination of gametocyte sex ratios under fecundity variation for the malaria parasite.

    PubMed

    Teboh-Ewungkem, Miranda I; Yuster, Thomas

    2016-11-07

    We investigate sex ratio determination strategies for the Malaria parasite based on putative changes in its male fecundity over the lifetime of an infection, and how such strategies might have evolved. We model fitness using the incomplete fertilization limit developed in Teboh-Ewungkem and Yuster (2010). We divide the infection lifetime of a strain into two periods, assume each human is infected by two different strains, and assume that there are two different strategies present among the many strains in the general malaria parasite population. A unique parameter dependent ESS exists for all parameter values in both of our main models, with many such strategies unbeatable. These strategies produce both male and female biased population sex ratios with female bias predominating over most of the parameter space. The first model (SKM) suggests that strains without the ability to detect characteristics of other strains present could still have evolved strategies to vary sex ratio over their lifetimes, and the second model (DKM) suggests strains with detection abilities might have evolved after that. Our analysis suggests that once the ability to detect the population sizes and fecundities of other strains has developed, detection of their sex ratio choices confers no additional selective advantage in that a DKM ESS is still an ESS among sex ratio detecting strategies. The sex ratio choices for each DKM ESS are given by the equilibrium values of the parameter equivalent sex ratio detecting strategy described in Teboh-Ewungkem and Wang (2012), in the case where two strains employing that strategy encounter each other.

  11. Sex and Age Effects of Functional Connectivity in Early Adulthood.

    PubMed

    Zhang, Chao; Cahill, Nathan D; Arbabshirani, Mohammad R; White, Tonya; Baum, Stefi A; Michael, Andrew M

    2016-11-01

    Functional connectivity (FC) in resting-state functional magnetic resonance imaging (rs-fMRI) is widely used to find coactivating regions in the human brain. Despite its widespread use, the effects of sex and age on resting FC are not well characterized, especially during early adulthood. Here we apply regression and graph theoretical analyses to explore the effects of sex and age on FC between the 116 AAL atlas parcellations (a total of 6670 FC measures). rs-fMRI data of 494 healthy subjects (203 males and 291 females; age range: 22-36 years) from the Human Connectome Project were analyzed. We report the following findings. (1) Males exhibited greater FC than females in 1352 FC measures (1025 survived Bonferroni correction; [Formula: see text]). In 641 FC measures, females exhibited greater FC than males but none survived Bonferroni correction. Significant FC differences were mainly present in frontal, parietal, and temporal lobes. Although the average FC values for males and females were significantly different, FC values of males and females exhibited large overlap. (2) Age effects were present only in 29 FC measures and all significant age effects showed higher FC in younger subjects. Age and sex differences of FC remained significant after controlling for cognitive measures. (3) Although sex [Formula: see text] age interaction did not survive multiple comparison correction, FC in females exhibited a faster cross-sectional decline with age. (4) Male brains were more locally clustered in all lobes but the cerebellum; female brains had a higher clustering coefficient at the whole-brain level. Our results indicate that although both male and female brains show small-world network characteristics, male brains were more segregated and female brains were more integrated. Findings of this study further our understanding of FC in early adulthood and provide evidence to support that age and sex should be controlled for in FC studies of young adults.

  12. An Extraordinary Host-Specific Sex Ratio in an Avian Louse (Phthiraptera: Insecta)--Chemical Distortion?

    PubMed

    Douglas, H D; Malenke, J R

    2015-08-01

    Distortions of sex ratios and sexual traits from synthetic chemicals have been well documented; however, there is little evidence for such phenomena associated with naturally occurring chemical exposures. We reasoned that chemical secretions of vertebrates could contribute to skewed sex ratios in ectoparasitic insects due to differences in susceptibility among the sexes. For example, among ectoparasitic lice the female is generally the larger sex. Smaller males may be more susceptible to chemical effects. We studied sex ratios of lice on two sympatric species of colonial seabirds. Crested auklets (Aethia cristatella) secrete a strong smelling citrus-like odorant composed of aldehydes while a closely related congener the least auklet (Aethia pusilla) lacks these compounds. Each auklet hosts three species of lice, two of which are shared in common. We found that the sex ratio of one louse species, Quadraceps aethereus (Giebel), was highly skewed on crested auklets 1:69 (males: females), yet close to unity on least auklets (1:0.97). We suggest that a host-specific effect contributes to this difference, such as the crested auklet's chemical odorant.

  13. Inbreeding and Offspring Sex Ratio in the Pygmy Hippopotamus (Cheoropsis liberiensis) Population Kept in Zoological Gardens.

    PubMed

    Graczyk, Magdalena; Cwiertnia, Piotr; Borowska, Alicja; Barczak, Elżbieta; Szwaczkowski, Tomasz

    2015-01-01

    The aim of this study was to estimate the inbreeding level and its impact on offspring sex ratio in the pygmy hippopotamus population kept in zoological gardens. Records of pygmy hippopotamus born between 1873-2013 were extracted from the international studbook. Totally, 1357 individuals originating from 148 breeding units were included (individuals with unknown sex were omitted). The offspring sex ratio is defined as the number of sons to the total number of progeny of each dam and sire. Spearman's rank correlation was employed to examine the relationships between the inbreeding level and offspring sex ratio. Inbreeding coefficients and individual increase in inbreeding coefficients (included as a linear co-variable) were examined as well as the geographic region and birth period using general linear models. The average inbreeding coefficient was 5.39%. The following sex proportion was observed for the inbred population: 57% and 43% for females and males, respectively. A significant relationship between inbreeding level of parents and their offspring sex ratio were estimated for European zoological gardens, whereas in others geographic regions the dependencies were insignificant.

  14. Age and Sex Factors in the Control of Automobiles.

    ERIC Educational Resources Information Center

    Allen, John A., Jr.; Soliday, Stanley M.

    The study investigated age and sex in the control of an automobile under normal driving conditions. Its major purpose was to gather baseline data for a driver license, road testing program. Forty volunteer subjects (10 men and 10 women over 30, 10 men and 10 women under 30) drove a specially instrumented car over an interstate highway course and a…

  15. Fetal Habituation Performance: Gestational Age and Sex Effects

    ERIC Educational Resources Information Center

    McCorry, Noleen K.; Hepper, Peter G.

    2007-01-01

    Habituation is the decrement in response to repeated stimulation. Fetal habituation performance may reflect the functioning of the central nervous system (CNS) prenatally. However, basic characteristics of the prenatal habituation phenomena remain unclear, such as the relationship with gestational age (GA) and fetal sex. The current study…

  16. Increased sex ratio in Russia and Cuba after Chernobyl: a radiological hypothesis

    PubMed Central

    2013-01-01

    Background The ratio of male to female offspring at birth may be a simple and non-invasive way to monitor the reproductive health of a population. Except in societies where selective abortion skews the sex ratio, approximately 105 boys are born for every 100 girls. Generally, the human sex ratio at birth is remarkably constant in large populations. After the Chernobyl nuclear power plant accident in April 1986, a long lasting significant elevation in the sex ratio has been found in Russia, i.e. more boys or fewer girls compared to expectation were born. Recently, also for Cuba an escalated sex ratio from 1987 onward has been documented and discussed in the scientific literature. Presentation of the hypothesis By the end of the eighties of the last century in Cuba as much as about 60% of the food imports were provided by the former Soviet Union. Due to its difficult economic situation, Cuba had neither the necessary insight nor the political strength to circumvent the detrimental genetic effects of imported radioactively contaminated foodstuffs after Chernobyl. We propose that the long term stable sex ratio increase in Cuba is essentially due to ionizing radiation. Testing of the hypothesis A synoptic trend analysis of Russian and Cuban annual sex ratios discloses upward jumps in 1987. The estimated jump height from 1986 to 1987 in Russia measures 0.51% with a 95% confidence interval (0.28, 0.75), p value < 0.0001. In Cuba the estimated jump height measures 2.99% (2.39, 3.60), p value < 0.0001. The hypothesis may be tested by reconstruction of imports from the world markets to Cuba and by radiological analyses of remains in Cuba for Cs-137 and Sr-90. Implications of the hypothesis If the evidence for the hypothesis is strengthened, there is potential to learn about genetic radiation risks and to prevent similar effects in present and future exposure situations. PMID:23947741

  17. Calibrating recruitment estimates for mourning doves from harvest age ratios

    USGS Publications Warehouse

    Miller, David A.; Otis, David L.

    2010-01-01

    We examined results from the first national-scale effort to estimate mourning dove (Zenaida macroura) age ratios and developed a simple, efficient, and generalizable methodology for calibrating estimates. Our method predicted age classes of unknown-age wings based on backward projection of molt distributions from fall harvest collections to preseason banding. We estimated 1) the proportion of late-molt individuals in each age class, and 2) the molt rates of juvenile and adult birds. Monte Carlo simulations demonstrated our estimator was minimally biased. We estimated model parameters using 96,811 wings collected from hunters and 42,189 birds banded during preseason from 68 collection blocks in 22 states during the 2005–2007 hunting seasons. We also used estimates to derive a correction factor, based on latitude and longitude of samples, which can be applied to future surveys. We estimated differential vulnerability of age classes to harvest using data from banded birds and applied that to harvest age ratios to estimate population age ratios. Average, uncorrected age ratio of known-age wings for states that allow hunting was 2.25 (SD 0.85) juveniles:adult, and average, corrected ratio was 1.91 (SD 0.68), as determined from harvest age ratios from an independent sample of 41,084 wings collected from random hunters in 2007 and 2008. We used an independent estimate of differential vulnerability to adjust corrected harvest age ratios and estimated the average population age ratio as 1.45 (SD 0.52), a direct measure of recruitment rates. Average annual recruitment rates were highest east of the Mississippi River and in the northwestern United States, with lower rates between. Our results demonstrate a robust methodology for calibrating recruitment estimates for mourning doves and represent the first large-scale estimates of recruitment for the species. Our methods can be used by managers to correct future harvest survey data to generate recruitment estimates for use in

  18. Impact of prenatal technologies on the sex ratio in India: an overview

    PubMed Central

    Madan, Kamlesh; Breuning, Martijn H.

    2014-01-01

    The fact that techniques of prenatal diagnosis are used in India and China to selectively eliminate females is widely known. It has been extensively reported in the international media and in scientific publications since the 1990s. The publication of the Census of India 2011 shows that the ratio of girls to boys below the age of 6 years continues to decline at an alarming rate. Following that publication, this topic has again received international attention. The aim of this article is to better inform the human genetics community of the magnitude of this practice and its consequences in India. In this overview, we examine the impact of prenatal technology on the sex ratio in India. We present facts and figures from the Census of India and other publications that show that the practice is wide spread throughout India, in urban and rural areas, among the rich and the poor, and among the educated and the illiterate. We also briefly discuss the possible causes, consequences, and solutions. Genet Med 16 6, 425–432. PMID:24177057

  19. Muscularity as a function of species, sex and age in small mammals

    NASA Technical Reports Server (NTRS)

    Pace, N.; Rahlmann, D. F.; Smith, A. H.

    1984-01-01

    Changes in the body skeletal muscle mass SMM (measured as a function of the ratio between the body creatine mass and the fat-free muscle creatine), and in muscularity (expressed as the ratio of SMM to fat-free body mass) were studied as functions of age, sex, and species in mouse, rat, hamster, guinea pig, and rabbit. Six animals of each sex were examined in eight age cohorts ranging from 1 to 24 months. Both species and age factors affect SMM. Strong sexual dimorphism in the SMM changes with age was displayed by mouse, rat, and guinea pig, whereas the hamster and rabbit were statistically monomorphic. The mouse, rat, and hamster attain a maximal SMM at about 1 year of age, whereas in the guinea pig and rabbit the decrease in SMM starts after 2 years. The value of muscularity reached a peak at age of 2-3 months in all animals of both sexes, with a pronounced difference among the species. The mouse emerged as the most muscular, while the guinea pig the least muscular, of all species.

  20. How do climate-linked sex ratios and dispersal limit range boundaries?

    PubMed Central

    2014-01-01

    Background Geographic ranges of ectotherms such as reptiles may be determined strongly by abiotic factors owing to causal links between ambient temperature, juvenile survival and individual sex (male or female). Unfortunately, we know little of how these factors interact with dispersal among populations across a species range. We used a simulation model to examine the effects of dispersal, temperature-dependent juvenile survival and sex determining mechanism (temperature-dependent sex determination (TSD) and genotypic sex determination (GSD)) and their interactions, on range limits in populations extending across a continuous range of air temperatures. In particular, we examined the relative importance of these parameters for population persistence to recommend targets for future empirical research. Results Dispersal influenced the range limits of species with TSD to a greater extent than in GSD species. Whereas male dispersal led to expanded species ranges across warm (female-producing) climates, female dispersal led to expanded ranges across cool (male-producing) climates. Two-sex dispersal eliminated the influence of biased sex ratios on ranges. Conclusion The results highlight the importance of the demographic parameter of sex ratio in determining population persistence and species range limits. PMID:25011492

  1. Age of sex-determining mechanisms in vertebrates.

    PubMed

    WITSCHI, E

    1959-08-14

    Certain characteristic patterns of physiologic sex determination are not causally linked with types of genic and chromosomal constitution (XX-XY or ZW-ZZ). The observed widespread but not universal parallelism in the distribution of genetic and physiologic patterns among vertebrate groups expresses genealogic relationship. On the basis of this interpretation one may estimate the approximate evolutionary age of the mechanism of genetic sex determination. It is concluded that in all tetrapod vertebrates these mechanisms originated during the Jurassic period. Environmental conditions seem to affect the progress of this evolution.

  2. Developmental mortality increases sex-ratio bias of a size-dimorphic bark beetle

    PubMed Central

    Lachowsky, Leanna E; Reid, Mary L

    2014-01-01

    1. Given sexual size dimorphism, differential mortality owing to body size can lead to sex-biased mortality, proximately biasing sex ratios. This mechanism may apply to mountain pine beetles, Dendroctonus ponderosae Hopkins, which typically have female-biased adult populations (2 : 1) with females larger than males. Smaller males could be more susceptible to stresses than larger females as developing beetles overwinter and populations experience high mortality. 2. Survival of naturally-established mountain pine beetles during the juvenile stage and the resulting adult sex ratios and body sizes (volume) were studied. Three treatments were applied to vary survival in logs cut from trees containing broods of mountain pine beetles. Logs were removed from the forest either in early winter, or in spring after overwintering below snow or after overwintering above snow. Upon removal, logs were placed at room temperature to allow beetles to complete development under similar conditions. 3. Compared with beetles from logs removed in early winter, mortality was higher and the sex ratio was more female-biased in overwintering logs. The bias increased with overwinter mortality. However, sex ratios were female-biased even in early winter, so additional mechanisms, other than overwintering mortality, contributed to the sex-ratio bias. Body volume varied little relative to sex-biased mortality, suggesting other size-independent causes of male-biased mortality. 4. Overwintering mortality is considered a major determinant of mountain pine beetle population dynamics. The disproportionate survival of females, who initiate colonisation of live pine trees, may affect population dynamics in ways that have not been previously considered. PMID:25400320

  3. Sex Ratio and Body Mass of Adult Herbivorous Beetles Depend on Time of Occurrence and Light Conditions

    PubMed Central

    Łukowski, Adrian; Mąderek, Ewa; Giertych, Marian J.; Karolewski, Piotr

    2015-01-01

    Body mass and sex ratio (F/M) of folivorous insects are easily measured parameters that are commonly used to assess the effect of food quality, living conditions, and preferences on the selection of favourable sites for offspring. A study was conducted on the polyphagous beetle, Gonioctena quinquepunctata (a pest of the native Prunus padus and alien P. serotina) and on the monophagous beetle, Altica brevicollis coryletorum (a pest of Corylus avellana). Both species have a similar life cycle with emergence of current-year adults in summer, and reproduction of 1-year-old insects in spring. A. brevicollis coryletorum feeds primarily on sunlit shrubs, while G. quinquepunctata prefers shaded leaves. The present study assessed the effect of time of occurrence (insect age) on body mass in both sexes and on the sex ratio F/M, taking into account the influence of light conditions associated with their favoured food source (sunlit vs. shaded leaves). We hypothesized that a change in body mass in current-year insects would be determined by the amount of consumed food, while the sex ratio would be stable, when in 1-year-old insects females would die shortly after oviposition, while males would be active for a prolonged time. Results confirmed the hypothesis that changes in mass of current-year beetles was determined by the amount of food intake. We also found that in spring, unfertilized females coexist with fertilized ones and that the latter females live for some time after oviposition; resulting in fluctuations of the mean mass for females. In both species, 1-year-old beetles were heavier than current-year. The preference of A. brevicollis coryletorum for sunlit leaves results in a higher body weight than in G. quinquepunctata in both seasons. The data are consistent and indicate seasonal fluctuations in body mass and changes in the sex ratio in 1-year-old beetles, due to the entrance into their reproductive period. PMID:26657564

  4. Sex Ratio and Body Mass of Adult Herbivorous Beetles Depend on Time of Occurrence and Light Conditions.

    PubMed

    Łukowski, Adrian; Mąderek, Ewa; Giertych, Marian J; Karolewski, Piotr

    2015-01-01

    Body mass and sex ratio (F/M) of folivorous insects are easily measured parameters that are commonly used to assess the effect of food quality, living conditions, and preferences on the selection of favourable sites for offspring. A study was conducted on the polyphagous beetle, Gonioctenaquinquepunctata (a pest of the native Prunus padus and alien P. serotina) and on the monophagous beetle, Alticabrevicollis coryletorum (a pest of Corylus avellana). Both species have a similar life cycle with emergence of current-year adults in summer, and reproduction of 1-year-old insects in spring. A. brevicollis coryletorum feeds primarily on sunlit shrubs, while G. quinquepunctata prefers shaded leaves. The present study assessed the effect of time of occurrence(insect age) on body mass in both sexes and on the sex ratio F/M, taking into account the influence of light conditions associated with their favoured food source (sunlit vs. shaded leaves). We hypothesized that a change in body mass in current-year insects would be determined by the amount of consumed food, while the sex ratio would be stable, when in 1-year-old insects females would die shortly after oviposition, while males would be active for a prolonged time. Results confirmed the hypothesis that changes in mass of current-year beetles was determined by the amount of food intake. We also found that in spring, unfertilized females coexist with fertilized ones and that the latter females live for some time after oviposition; resulting in fluctuations of the mean mass for females. In both species, 1-year-old beetles were heavier than current-year. The preference of A. brevicollis coryletorum for sunlit leaves results in a higher body weight than in G. quinquepunctata in both seasons. The data are consistent and indicate seasonal fluctuations in body mass and changes in the sex ratio in 1-year-old beetles, due to the entrance into their reproductive period.

  5. Male breast cancer, age and sex chromosome aneuploidy

    PubMed Central

    Jacobs, P A; Maloney, V; Cooke, R; Crolla, J A; Ashworth, A; Swerdlow, A J

    2013-01-01

    Background: In cultured, dividing transformed T lymphocytes and in dividing bone marrow cells from normal men and those with a haematological malignancy, sex chromosome aneuploidy has been found to increase in prevalence and degree with age. This has rarely been investigated in non-dividing uncultured blood samples. The loss and gain of the X chromosome in dividing transformed lymphocytes in women with age is much more frequent than that of the Y chromosome in males. However, paradoxically X chromosome aneuploidy is rarely seen in the dividing cells of bone marrow of females. Methods: In blood samples from 565 men with breast cancer and 54 control men from the England and Wales general population, 80 cell nuclei per sample were scored for presence of X and Y chromosomes using fluorescent centromeric probes. Results: Sex chromosome aneuploidy, largely Y chromosome loss, was present in 63% of cases and 57% of controls, with the prevalence and degree of aneuploidy increasingly sharply and highly significantly with age. At ages 65–80 years, 71% of cases and 85% of controls showed aneuploidy and 15% and 25%, respectively, had ⩾10% of cells aneuploid. Allowing for age, aneuploidy was less prevalent (P=0.03) in cases than controls. Conclusion: Sex chromosome aneuploidy in non-dividing nuclei of peripheral blood cells is frequent in adult men, the prevalence and degree increasing sharply with age. The possible relation of sex chromosome aneuploidy to breast cancer risk in men, and to cancer risk generally, needs further investigation, ideally in cohort studies. PMID:23299533

  6. Superficial white matter: effects of age, sex, and hemisphere.

    PubMed

    Phillips, Owen R; Clark, Kristi A; Luders, Eileen; Azhir, Ramin; Joshi, Shantanu H; Woods, Roger P; Mazziotta, John C; Toga, Arthur W; Narr, Katherine L

    2013-01-01

    Structural and diffusion imaging studies demonstrate effects of age, sex, and asymmetry in many brain structures. However, few studies have addressed how individual differences might influence the structural integrity of the superficial white matter (SWM), comprised of short-range association (U-fibers), and intracortical axons. This study thus applied a sophisticated computational analysis approach to structural and diffusion imaging data obtained from healthy individuals selected from the International Consortium for Brain Mapping (ICBM) database across a wide adult age range (n=65, age: 18-74 years, all Caucasian). Fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) were sampled and compared at thousands of spatially matched SWM locations and within regions-of-interest to examine global and local variations in SWM integrity across age, sex, and hemisphere. Results showed age-related reductions in FA that were more pronounced in the frontal SWM than in the posterior and ventral brain regions, whereas increases in RD and AD were observed across large areas of the SWM. FA was significantly greater in left temporoparietal regions in men and in the posterior callosum in women. Prominent leftward FA and rightward AD and RD asymmetries were observed in the temporal, parietal, and frontal regions. Results extend previous findings restricted to the deep white matter pathways to demonstrate regional changes in the SWM microstructure relating to processes of demyelination and/or to the number, coherence, or integrity of axons with increasing age. SWM fiber organization/coherence appears greater in the left hemisphere regions spanning language and other networks, while more localized sex effects could possibly reflect sex-specific advantages in information strategies.

  7. Superficial White Matter: Effects of Age, Sex, and Hemisphere

    PubMed Central

    Phillips, Owen R.; Clark, Kristi A.; Luders, Eileen; Azhir, Ramin; Joshi, Shantanu H.; Woods, Roger P.; Mazziotta, John C.; Toga, Arthur W.

    2013-01-01

    Abstract Structural and diffusion imaging studies demonstrate effects of age, sex, and asymmetry in many brain structures. However, few studies have addressed how individual differences might influence the structural integrity of the superficial white matter (SWM), comprised of short-range association (U-fibers), and intracortical axons. This study thus applied a sophisticated computational analysis approach to structural and diffusion imaging data obtained from healthy individuals selected from the International Consortium for Brain Mapping (ICBM) database across a wide adult age range (n=65, age: 18–74 years, all Caucasian). Fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) were sampled and compared at thousands of spatially matched SWM locations and within regions-of-interest to examine global and local variations in SWM integrity across age, sex, and hemisphere. Results showed age-related reductions in FA that were more pronounced in the frontal SWM than in the posterior and ventral brain regions, whereas increases in RD and AD were observed across large areas of the SWM. FA was significantly greater in left temporoparietal regions in men and in the posterior callosum in women. Prominent leftward FA and rightward AD and RD asymmetries were observed in the temporal, parietal, and frontal regions. Results extend previous findings restricted to the deep white matter pathways to demonstrate regional changes in the SWM microstructure relating to processes of demyelination and/or to the number, coherence, or integrity of axons with increasing age. SWM fiber organization/coherence appears greater in the left hemisphere regions spanning language and other networks, while more localized sex effects could possibly reflect sex-specific advantages in information strategies. PMID:23461767

  8. Germ-line origins of mutation in families with hemophilia B: the sex ratio varies with the type of mutation.

    PubMed Central

    Ketterling, R P; Vielhaber, E; Bottema, C D; Schaid, D J; Cohen, M P; Sexauer, C L; Sommer, S S

    1993-01-01

    Previous epidemiological and biochemical studies have generated conflicting estimates of the sex ratio of mutation. Direct genomic sequencing in combination with haplotype analysis extends previous analyses by allowing the precise mutation to be determined in a given family. From analysis of the factor IX gene of 260 consecutive families with hemophilia B, we report the germ-line origin of mutation in 25 families. When combined with 14 origins of mutation reported by others and with 4 origins previously reported by us, a total of 25 occur in the female germ line, and 18 occur in the male germ line. The excess of germ-line origins in females does not imply an overall excess mutation rate per base pair in the female germ line. Bayesian analysis of the data indicates that the sex ratio varies with the type of mutation. The aggregate of single-base substitutions shows a male predominance of germ-line mutations (P < .002). The maximum-likelihood estimate of the male predominance is 3.5-fold. Of the single-base substitutions, transitions at the dinucleotide CpG show the largest male predominance (11-fold). In contrast to single-base substitutions, deletions display a sex ratio of unity. Analysis of the parental age at transmission of a new mutation suggests that germ-line mutations are associated with a small increase in parental age in females but little, if any, increase in males. Although direct genomic sequencing offers a general method for defining the origin of mutation in specific families, accurate estimates of the sex ratios of different mutational classes require large sample sizes and careful correction for multiple biases of ascertainment. The biases in the present data result in an underestimate of the enhancement of mutation in males. PMID:8434583

  9. Germ-line origins of mutation in families with hemophilia B: The sex ratio varies with the type of mutation

    SciTech Connect

    Ketterling, R.P.; Vielhaber, E.; Bottema, C.D.K.; Schaid, D.J.; Sommer, S.S. ); Cohen, M.P. ); Sexauer, C.L. )

    1993-01-01

    Previous epidemiological and biochemical studies have generated conflicting estimates of the sex ratio of mutation. Direct genomic sequencing in combination with haplotype analysis extends previous analyses by allowing the precise mutation to be determined in a given family. From analysis of the factor IX gene of 260 consecutive families with hemophilia B, the authors report the germ-line origin of mutation in 25 families. When combined with 14 origins of mutation reported by others and with 4 origins previously reported by them, a total of 25 occur in the female germ line, and 18 occur in the male germ line. The excess of germ-line origins in females does not imply an overall excess mutation rate per base pair in the female germ line. Bayesian analysis of the data indicates that the sex ratio varies with the type of mutation. The aggregate of single-base substitutions shows a male predominance of germ-line mutations (P < .002). The maximum-likelihood estimate of the male predominance is 3.5-fold. Of the single-base substitutions, deletions display a sex ratio of unity. Analysis of the parental age at transmission of a new mutation suggests that germ-line mutations are associated with a small increase in parental age in females but little, if any, increase in males. Although direct genomic sequencing offers a general method for defining the origin of mutation in specific families, accurate estimates of the sex ratios of different mutational classes require large sample sizes and careful correction for multiple biases of ascertainment. The biases in the present data result in an underestimate of the enhancement of mutation in males. 62 refs., 1 fig., 5 tabs.

  10. Breeding durations as estimators of adult sex ratios and population size.

    PubMed

    Payne, Nicholas Leslie; Gillanders, Bronwyn May; Semmens, Jayson

    2011-02-01

    Adult sex ratios (ASRs) and population size are two of the most fundamental parameters in population biology, as they are the main determinants of genetic and demographic viability, and vulnerability of a population to stochastic events. Underpinning the application of population viability analysis for predicting the extinction risk of populations is the need to accurately estimate parameters that determine the viability of populations (i.e. the ASR and population size). Here we demonstrate that a lack of temporal information can confound estimation of both parameters. Using acoustic telemetry, we compared differences in breeding durations of both sexes for a giant Australian cuttlefish Sepia apama breeding aggregation to the strongly male-biased operational sex ratio (4:1), in order to estimate the population ASR. The ratio of breeding durations between sexes was equal to the operational sex ratio, suggesting that the ASR is not strongly male-biased, but balanced. Furthermore, the short residence times of individuals at the breeding aggregation suggests that previous density-based abundance estimates have significantly underestimated population size. With the current wide application of population viability analysis for predicting the extinction risk of populations, tools to improve the accuracy of such predictions are vital. Here we provide a new approach to estimating the fundamental ASR parameter, and call for temporal considerations when estimating population size.

  11. Aggressive behavior of the male parent predicts brood sex ratio in a songbird

    NASA Astrophysics Data System (ADS)

    Szász, Eszter; Garamszegi, László Zsolt; Hegyi, Gergely; Szöllősi, Eszter; Markó, Gábor; Török, János; Rosivall, Balázs

    2014-08-01

    Brood sex ratio is often affected by parental or environmental quality, presumably in an adaptive manner that is the sex that confers higher fitness benefits to the mother is overproduced. So far, studies on the role of parental quality have focused on parental morphology and attractiveness. However, another aspect, the partner's behavioral characteristics, may also be expected to play a role in brood sex ratio adjustment. To test this hypothesis, we investigated whether the proportion of sons in the brood is predicted by the level of territorial aggression displayed by the father, in the collared flycatcher ( Ficedula albicollis). The proportion of sons in the brood was higher in early broods and increased with paternal tarsus length. When controlling for breeding date and body size, we found a higher proportion of sons in the brood of less aggressive fathers. Male nestlings are more sensitive to the rearing environment, and the behavior of courting males may often be used by females to assess their future parental activity. Therefore, adjusting brood sex ratio to the level of male aggression could be adaptive. Our results indicate that the behavior of the partner could indeed be a significant determinant in brood sex ratio adjustment, which should not be overlooked in future studies.

  12. Impaired imprinted X chromosome inactivation is responsible for the skewed sex ratio following in vitro fertilization

    PubMed Central

    Tan, Kun; An, Lei; Miao, Kai; Ren, Likun; Hou, Zhuocheng; Tao, Li; Zhang, Zhenni; Wang, Xiaodong; Xia, Wei; Liu, Jinghao; Wang, Zhuqing; Xi, Guangyin; Gao, Shuai; Sui, Linlin; Zhu, De-Sheng; Wang, Shumin; Wu, Zhonghong; Bach, Ingolf; Chen, Dong-bao; Tian, Jianhui

    2016-01-01

    Dynamic epigenetic reprogramming occurs during normal embryonic development at the preimplantation stage. Erroneous epigenetic modifications due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF) are linked to various short- or long-term consequences. Among these, the skewed sex ratio, an indicator of reproductive hazards, was reported in bovine and porcine embryos and even human IVF newborns. However, since the first case of sex skewing reported in 1991, the underlying mechanisms remain unclear. We reported herein that sex ratio is skewed in mouse IVF offspring, and this was a result of female-biased peri-implantation developmental defects that were originated from impaired imprinted X chromosome inactivation (iXCI) through reduced ring finger protein 12 (Rnf12)/X-inactive specific transcript (Xist) expression. Compensation of impaired iXCI by overexpression of Rnf12 to up-regulate Xist significantly rescued female-biased developmental defects and corrected sex ratio in IVF offspring. Moreover, supplementation of an epigenetic modulator retinoic acid in embryo culture medium up-regulated Rnf12/Xist expression, improved iXCI, and successfully redeemed the skewed sex ratio to nearly 50% in mouse IVF offspring. Thus, our data show that iXCI is one of the major epigenetic barriers for the developmental competence of female embryos during preimplantation stage, and targeting erroneous epigenetic modifications may provide a potential approach for preventing IVF-associated complications. PMID:26951653

  13. Disentangling the effect of genes, the environment and chance on sex ratio variation in a wild bird population

    PubMed Central

    Postma, Erik; Heinrich, Franziska; Koller, Ursina; Sardell, Rebecca J.; Reid, Jane M.; Arcese, Peter; Keller, Lukas F.

    2011-01-01

    Sex ratio theory proposes that the equal sex ratio typically observed in birds and mammals is the result of natural selection. However, in species with chromosomal sex determination, the same 1 : 1 sex ratio is expected under random Mendelian segregation. Here, we present an analysis of 14 years of sex ratio data for a population of song sparrows (Melospiza melodia) on Mandarte Island, at the nestling stage and at independence from parental care. We test for the presence of variance in sex ratio over and above the binomial variance expected under Mendelian segregation, and thereby quantify the potential for selection to shape sex ratio. Furthermore, if sex ratio variation is to be shaped by selection, we expect some of this extra-binomial variation to have a genetic basis. Despite ample statistical power, we find no evidence for the existence of either genetic or environmentally induced variation in sex ratio, in the nest or at independence. Instead, the sex ratio variation observed matches that expected under random Mendelian segregation. Using one of the best datasets of its kind, we conclude that female song sparrows do not, and perhaps cannot, adjust the sex of their offspring. We discuss the implications of this finding and make suggestions for future research. PMID:21345862

  14. Analysis of the sex ratio of reported gonorrhoea incidence in Shenzhen, China

    PubMed Central

    Xiong, Mingzhou; Lan, Lina; Feng, Tiejian; Zhao, Guanglu; Wang, Feng; Hong, Fuchang; Wu, Xiaobing; Zhang, Chunlai; Wen, Lizhang; Liu, Aizhong; Best, John McCulloch; Tang, Weiming

    2016-01-01

    Objective To assess the clinical process of gonorrhoea diagnosis and report in China, and to determine the difference of sex ratio between reported incidence based on reporting data and true diagnosis rate based on reference tests of gonorrhoea. Setting A total of 26 dermatology and sexually transmitted disease (STD) departments, 34 obstetrics-gynaecology clinics and 28 urology outpatient clinics selected from 34 hospitals of Shenzhen regarded as our study sites. Participants A total of 2754 participants were recruited in this study, and 2534 participants completed the questionnaire survey and provided genital tract secretion specimens. There were 1106 male and 1428 female participants. Eligible participants were patients who presented for outpatient STD care at the selected clinics for the first time in October 2012 were at least 18 years old, and were able to give informed consent. Outcome measures Untested rate, true-positive rate, false-negative rate and unreported rate of gonorrhoea, as well as reported gonorrhoea incidence sex ratio and true diagnosis sex ratio were calculated and used to describe the results. Results 2534 participants were enrolled in the study. The untested rate of gonorrhoea among females was significantly higher than that among males (female 88.1%, male 68.3%, p=0.001). The male-to-female sex ratios of untested rate, true-positive rate, false-negative rate and unreported rate were 1:1.3, 1.2:1, 1:1.6 and 1:1.4, respectively. The reported gonorrhoea incidence sex ratio of new diagnosed gonorrhoea was 19.8:1 (male vs female: 87/1106 vs 5/1420), while the true diagnosis sex ratio was 2.5:1 (male vs female: 161/1106 vs 84/1420). These data indicate that the sex ratio of reported gonorrhoea incidence has been overestimated by a factor of 7.9 (19.8/2.5). Conclusions We found the current reported gonorrhoea incidence and sex ratios to be inaccurate due to underestimations of gonorrhoea incidence, especially among women. PMID:26975933

  15. Hematological parameters in relation to age, sex and biochemical values for mute swans (Cygnus olor).

    PubMed

    Dolka, B; Włodarczyk, R; Zbikowski, A; Dolka, I; Szeleszczuk, P; Kluciński, W

    2014-06-01

    The knowledge of the correct morphological and biochemical parameters in mute swans is an important indicator of their health status, body condition, adaptation to habitat and useful diagnostic tools in veterinary practice and ecological research. The aim of the study was to obtain hematological parameters in relation to age, sex and serum biochemistry values in wild-living mute swans. We found the significant differences in the erythrocyte count, hematocrit, hemoglobin concentration and erythrocyte sedimentation rate in relation to age of mute swans. There were no differences in hematological values between males and females. The leukogram and H/L ratio did not vary by age and sex in swans. Among of biochemical parameters the slightly increased AST, ALP, CK, K, urea, decreased CHOL and TG values were recorded. As far as we know, this is the first study in which the morphometric parameters of blood cells in mute swans were presented. We found extremely low concentration of lead in blood (at subthreshold level). No blood parasites were found in blood smears. The analysis of body mass and biometric parameters revealed a significant differences dependent on age and sex. No differences in the scaled mass index were found. Our results represent a normal hematologic and blood chemistry values and age-sex related changes, as reference values for the mute swan.

  16. Age, sex and reproductive status affect boldness in dogs.

    PubMed

    Starling, Melissa J; Branson, Nicholas; Thomson, Peter C; McGreevy, Paul D

    2013-09-01

    Boldness in dogs is believed to be one end of the shy-bold axis, representing a super-trait. Several personality traits fall under the influence of this super-trait. Previous studies have found that boldness is affected by breed and breed groups, influences performance in sporting dogs, and is affected in some cases by the sex of the dogs. This study investigated the effects of dog age, sex and reproductive status on boldness in dogs by way of a dog personality survey circulated amongst Australian dog owners. Age had a significant effect on boldness (F=4.476; DF=16,758; P<0.001), with boldness decreasing with age in years. Males were bolder than females (F=19.219; DF=1,758; P<0.001) and entire dogs were bolder than neutered dogs (F=4.330; DF=1,758; P<0.038). The study indicates how behaviour may change in adult dogs as they age and adds to the literature on how sex and reproductive status may affect personality in dogs.

  17. [The Rheological Properties of Blood Depending on Age and Sex].

    PubMed

    Filatova, O V; Sidorenko, A A; Agarkova, S A

    2015-01-01

    The rheological properties of blood (viscosity, concentration of red blood cells, erythrocyte sedimantation rate, prothrombin index, and fibrinogen and blood lipid concentration) were studied in apparently healthy subjects of both sexes within the age range from 1 to 75 years. We observed an increase in blood viscosity from infancy to adulthood, followed by a decrease in older age in males. A progressive increase in viscosity is observed in females with aging. We determined three age periods during which the viscosity values remain constant: 1) from the period of early infancy to the second childhood (3.6 ± 0.07 mPa s regardless of sex); 2) from adolescence to the second period of adulthood (5.1 ± 0.06 in men; 4.3 ± 0.05 mPa s in women); 3) elderly and senile age (4.7 ± 0.13 in men; 4.4 ± 0.09 mPa s in women). Sex-related differences in the absolute value of blood viscosity (p < 0.001) were discovered in the period of adulthood. Moreover, we observed sex-related differences in the values of determination coefficients of interrelation between viscosity and the level of red blood cells (R(M)2 = 0.41, p < 0.001; R(F)2 = 0.35, p < 0.001), and viscosity and cholesterol level (R(M)2 = 0.47, p < 0.001; R(F)2 = 0.68, p < 0.001) among men and women. The factor analysis showed that blood viscosity correlates with the concentration of red blood cells by 28%; with the level of fibrinogen, by 23%; with the cholesterol concentration, by 20%.

  18. Cancer, Infant Mortality and Birth Sex-Ratio in Fallujah, Iraq 2005–2009

    PubMed Central

    Busby, Chris; Hamdan, Malak; Ariabi, Entesar

    2010-01-01

    There have been anecdotal reports of increases in birth defects and cancer in Fallujah, Iraq blamed on the use of novel weapons (possibly including depleted uranium) in heavy fighting which occurred in that town between US led forces and local elements in 2004. In Jan/Feb 2010 the authors organised a team of researchers who visited 711 houses in Fallujah, Iraq and obtained responses to a questionnaire in Arabic on cancer, birth defects and infant mortality. The total population in the resulting sample was 4,843 persons with and overall response rate was better than 60%. Relative Risks for cancer were age-standardised and compared to rates in the Middle East Cancer Registry (MECC, Garbiah Egypt) for 1999 and rates in Jordan 1996–2001. Between Jan 2005 and the survey end date there were 62 cases of cancer malignancy reported (RR = 4.22; CI: 2.8, 6.6; p < 0.00000001) including 16 cases of childhood cancer 0–14 (RR = 12.6; CI: 4.9, 32; p < 0.00000001). Highest risks were found in all-leukaemia in the age groups 0–34 (20 cases RR = 38.5; CI: 19.2, 77; p < 0.00000001), all lymphoma 0–34 (8 cases, RR = 9.24;CI: 4.12, 20.8; p < 0.00000001), female breast cancer 0–44 (12 cases RR = 9.7;CI: 3.6, 25.6; p < 0.00000001) and brain tumours all ages (4 cases, RR = 7.4;CI: 2.4, 23.1; P < 0.004). Infant mortality was based on the mean birth rate over the 4 year period 2006–2009 with 1/6th added for cases reported in January and February 2010. There were 34 deaths in the age group 0–1 in this period giving a rate of 80 deaths per 1,000 births. This may be compared with a rate of 19.8 in Egypt (RR = 4.2 p < 0.00001) 17 in Jordan in 2008 and 9.7 in Kuwait in 2008. The mean birth sex-ratio in the recent 5-year cohort was anomalous. Normally the sex ratio in human populations is a constant with 1,050 boys born to 1,000 girls. This is disturbed if there is a genetic damage stress. The ratio of boys to 1,000 girls in the 0–4, 5–9, 10–14 and 15–19 age cohorts in the

  19. Sex Ratio Bias and Extinction Risk in an Isolated Population of Tuatara (Sphenodon punctatus)

    PubMed Central

    Grayson, Kristine L.; Mitchell, Nicola J.; Monks, Joanne M.; Keall, Susan N.; Wilson, Joanna N.; Nelson, Nicola J.

    2014-01-01

    Understanding the mechanisms underlying population declines is critical for preventing the extinction of endangered populations. Positive feedbacks can hasten the process of collapse and create an ‘extinction vortex,’ particularly in small, isolated populations. We provide a case study of a male-biased sex ratio creating the conditions for extinction in a natural population of tuatara (Sphenodon punctatus) on North Brother Island in the Cook Strait of New Zealand. We combine data from long term mark-recapture surveys, updated model estimates of hatchling sex ratio, and population viability modeling to measure the impacts of sex ratio skew. Results from the mark-recapture surveys show an increasing decline in the percentage of females in the adult tuatara population. Our monitoring reveals compounding impacts on female fitness through reductions in female body condition, fecundity, and survival as the male-bias in the population has increased. Additionally, we find that current nest temperatures are likely to result in more male than female hatchlings, owing to the pattern of temperature-dependent sex determination in tuatara where males hatch at warmer temperatures. Anthropogenic climate change worsens the situation for this isolated population, as projected temperature increases for New Zealand are expected to further skew the hatchling sex ratio towards males. Population viability models predict that without management intervention or an evolutionary response, the population will ultimately become entirely comprised of males and functionally extinct. Our study demonstrates that sex ratio bias can be an underappreciated threat to population viability, particularly in populations of long-lived organisms that appear numerically stable. PMID:24714691

  20. Teeth, Sex, and Testosterone: Aging in the World's Smallest Primate

    PubMed Central

    Zohdy, Sarah; Gerber, Brian D.; Tecot, Stacey; Blanco, Marina B.; Winchester, Julia M.; Wright, Patricia C.; Jernvall, Jukka

    2014-01-01

    Mouse lemurs (Microcebus spp.) are an exciting new primate model for understanding human aging and disease. In captivity, Microcebus murinus develops human-like ailments of old age after five years (e.g., neurodegeneration analogous to Alzheimer's disease) but can live beyond 12 years. It is believed that wild Microcebus follow a similar pattern of senescence observed in captive animals, but that predation limits their lifespan to four years, thus preventing observance of these diseases in the wild. Testing whether this assumption is true is informative about both Microcebus natural history and environmental influences on senescence, leading to interpretation of findings for models of human aging. Additionally, the study of Microcebus longevity provides an opportunity to better understand mechanisms of sex-biased longevity. Longevity is often shorter in males of species with high male-male competition, such as Microcebus, but mouse lemurs are sexually monomorphic, suggesting similar lifespans. We collected individual-based observations of wild brown mouse lemurs (Microcebus rufus) from 2003–2010 to investigate sex-differences in survival and longevity. Fecal testosterone was measured as a potential mechanism of sex-based differences in survival. We used a combination of high-resolution tooth wear techniques, mark-recapture, and hormone enzyme immunoassays. We found no dental or physical signs of senescence in M. rufus as old as eight years (N = 189, ages 1–8, mean = 2.59±1.63 SE), three years older than captive, senescent congeners (M. murinus). Unlike other polygynandrous vertebrates, we found no sex difference in age-dependent survival, nor sex or age differences in testosterone levels. While elevated male testosterone levels have been implicated in shorter lifespans in several species, this is one of the first studies to show equivalent testosterone levels accompanying equivalent lifespans. Future research on captive aged individuals can determine

  1. Integrated modelling of age and sex patterns of European migration.

    PubMed

    Wiśniowski, Arkadiusz; Forster, Jonathan J; Smith, Peter W F; Bijak, Jakub; Raymer, James

    2016-10-01

    Age and sex patterns of migration are essential for understanding drivers of population change and heterogeneity of migrant groups. We develop a hierarchical Bayesian model to estimate such patterns for international migration in the European Union and European Free Trade Association from 2002 to 2008, which was a period of time when the number of members expanded from 19 to 31 countries. Our model corrects for the inadequacies and inconsistencies in the available data and estimates the missing patterns. The posterior distributions of the age and sex profiles are then combined with a matrix of origin-destination flows, resulting in a synthetic database with measures of uncertainty for migration flows and other model parameters.

  2. Determination of Sperm Sex Ratio in Bovine Semen Using Multiplex Real-time Polymerase Chain Reaction.

    PubMed

    Khamlor, Trisadee; Pongpiachan, Petai; Sangsritavong, Siwat; Chokesajjawatee, Nipa

    2014-10-01

    Gender selection is important in livestock industries; for example, female calves are required in the dairy industry. Sex-sorted semen is commonly used for the production of calves of the desired gender. However, assessment of the sex ratio of the sorted semen is tedious and expensive. In this study, a rapid, cost effective and reliable method for determining the sex ratio was developed using a multiplex real-time polymerase chain reaction (PCR) assay. In this assay, the X and Y chromosome-specific markers, i.e., bovine proteolipid protein (PLP) gene and sex-determining region Y (SRY) were simultaneously quantified in a single tube. The multiplex real-time PCR assay was shown to have high amplification efficiencies (97% to 99%) comparable to the separated-tube simplex real-time PCR assay. The results obtained from both assays were not significantly different (p>0.05). The multiplex assay was validated using reference DNA of known X ratio (10%, 50%, and 90%) as templates. The measured %X in semen samples were the same within 95% confidence intervals as the expected values, i.e., >90% in X-sorted semen, <10% in Y-sorted semen and close to 50% in the unsorted semen. The multiplex real-time PCR assay as shown in this study can thus be used to assess purity of sex-sorted semen.

  3. Sex differences, sexual selection, and ageing: an experimental evolution approach.

    PubMed

    Maklakov, Alexei A; Bonduriansky, Russell; Brooks, Robert C

    2009-10-01

    Life-history (LH) theory predicts that selection will optimize the trade-off between reproduction and somatic maintenance. Reproductive ageing and finite life span are direct consequences of such optimization. Sexual selection and conflict profoundly affect the reproductive strategies of the sexes and thus can play an important role in the evolution of life span and ageing. In theory, sexual selection can favor the evolution of either faster or slower ageing, but the evidence is equivocal. We used a novel selection experiment to investigate the potential of sexual selection to influence the adaptive evolution of age-specific LH traits. We selected replicate populations of the seed beetle Callosobruchus maculatus for age at reproduction ("Young" and "Old") either with or without sexual selection. We found that LH selection resulted in the evolution of age-specific reproduction and mortality but these changes were largely unaffected by sexual selection. Sexual selection depressed net reproductive performance and failed to promote adaptation. Nonetheless, the evolution of several traits differed between males and females. These data challenge the importance of current sexual selection in promoting rapid adaptation to environmental change but support the hypothesis that sex differences in LH-a historical signature of sexual selection-are key in shaping trait responses to novel selection.

  4. Autonomic receptors in urinary tract: Sex and age differences

    SciTech Connect

    Latifpour, J.; Kondo, S.; O'Hollaren, B.; Morita, T.; Weiss, R.M. )

    1990-05-01

    As age and sex affect the function of the lower urinary tract, we studied the characteristics of adrenergic and cholinergic receptors in various parts of lower urinary tract smooth muscle of young (6 months) and old (4 1/2-5 years) male and female rabbits. Saturation experiments performed with (3H)prazosin, (3H)yohimbine, (3H)dihydroalprenolol and (3H)quinuclidinyl benzylate in rabbit bladder base, bladder dome and urethra indicate the presence of regional, sex- and age-related differences in the density of alpha-1, alpha-2, and beta adrenergic and muscarinic cholinergic receptors. Alpha-2 adrenergic receptor density is considerably higher in the female than in the male urethra of both age groups, whereas the higher density of beta adrenergic receptors in the female than in the male bladder base is observed only in the younger animals. The density of muscarinic receptors is higher in bladder dome than in bladder base or urethra in young rabbits of both sexes. In the old animals, the density of muscarinic receptors in bladder base increases to the level observed in bladder dome. Inhibition experiments with selective adrenergic agonists and antagonists indicate that the pharmacological profiles of alpha-2 adrenergic receptors in the urethra and beta adrenergic receptors in the bladder dome and bladder base are similar in both sexes and at both ages. Beta-2 adrenergic receptors are shown to be predominant in bladder base and bladder dome of rabbits. Parallel studies in rabbit urethra, adult rat cortex and neonatal rat lung show that the urethral alpha-2 adrenergic receptors are of the alpha-2A subtype.

  5. Sex and Age Effects of Functional Connectivity in Early Adulthood

    PubMed Central

    Zhang, Chao; Cahill, Nathan D.; Arbabshirani, Mohammad R.; White, Tonya; Baum, Stefi A.

    2016-01-01

    Abstract Functional connectivity (FC) in resting-state functional magnetic resonance imaging (rs-fMRI) is widely used to find coactivating regions in the human brain. Despite its widespread use, the effects of sex and age on resting FC are not well characterized, especially during early adulthood. Here we apply regression and graph theoretical analyses to explore the effects of sex and age on FC between the 116 AAL atlas parcellations (a total of 6670 FC measures). rs-fMRI data of 494 healthy subjects (203 males and 291 females; age range: 22–36 years) from the Human Connectome Project were analyzed. We report the following findings. (1) Males exhibited greater FC than females in 1352 FC measures (1025 survived Bonferroni correction; \\documentclass{aastex}\\usepackage{amsbsy}\\usepackage{amsfonts}\\usepackage{amssymb}\\usepackage{bm}\\usepackage{mathrsfs}\\usepackage{pifont}\\usepackage{stmaryrd}\\usepackage{textcomp}\\usepackage{portland, xspace}\\usepackage{amsmath, amsxtra}\\pagestyle{empty}\\DeclareMathSizes{10}{9}{7}{6}\\begin{document} $$p < 7.49{ \\rm{E}} - 6$$ \\end{document}). In 641 FC measures, females exhibited greater FC than males but none survived Bonferroni correction. Significant FC differences were mainly present in frontal, parietal, and temporal lobes. Although the average FC values for males and females were significantly different, FC values of males and females exhibited large overlap. (2) Age effects were present only in 29 FC measures and all significant age effects showed higher FC in younger subjects. Age and sex differences of FC remained significant after controlling for cognitive measures. (3) Although sex \\documentclass{aastex}\\usepackage{amsbsy}\\usepackage{amsfonts}\\usepackage{amssymb}\\usepackage{bm}\\usepackage{mathrsfs}\\usepackage{pifont}\\usepackage{stmaryrd}\\usepackage{textcomp}\\usepackage{portland, xspace}\\usepackage{amsmath, amsxtra}\\pagestyle{empty}\\DeclareMathSizes{10}{9}{7}{6}\\begin{document} $$\\times

  6. Cognitive sex differences are not magnified as a function of age, sex hormones, or puberty development during early adolescence.

    PubMed

    Herlitz, Agneta; Reuterskiöld, Lena; Lovén, Johanna; Thilers, Petra P; Rehnman, Jenny

    2013-01-01

    Are cognitive sex differences magnified by individual differences in age, sex hormones, or puberty development? Cross-sectional samples of 12- to 14-year-old boys (n = 85) and girls (n = 102) completed tasks assessing episodic memory, face recognition, verbal fluency, and mental rotations. Blood estradiol, free testosterone, and self-rated puberty scores were obtained. Sex differences were found on all cognitive measures. However, the magnitude was not larger for older children, hormones and cognitive performance were not associated, and early maturers did not perform better than late maturers. Thus, cognitive sex differences were not associated with age, levels of sex hormones, or puberty development.

  7. Sex-ratio evolution in nuclear-cytoplasmic gynodioecy when restoration is a threshold trait.

    PubMed

    Bailey, Maia F; Delph, Lynda F

    2007-08-01

    Gynodioecious plant species, which have populations consisting of female and hermaphrodite individuals, usually have complex sex determination involving cytoplasmic male sterility (CMS) alleles interacting with nuclear restorers of fertility. In response to recent evidence, we present a model of sex-ratio evolution in which restoration of male fertility is a threshold trait. We find that females are maintained at low frequencies for all biologically relevant parameter values. Furthermore, this model predicts periodically high female frequencies (>50%) under conditions of lower female seed fecundity advantages (compensation, x = 5%) and pleiotropic fitness effects associated with restorers of fertility (costs of restoration, y = 20%) than in other models. This model explains the maintenance of females in species that have previously experienced invasions of CMS alleles and the evolution of multiple restorers. Sensitivity of the model to small changes in cost and compensation values and to initial conditions may explain why populations of the same species vary widely for sex ratio.

  8. Cognitive ability correlates positively with son birth and predicts cross-cultural variation of the offspring sex ratio

    NASA Astrophysics Data System (ADS)

    Dama, Madhukar Shivajirao

    2013-06-01

    Human populations show remarkable variation in the sex ratio at birth which is believed to be related to the parental condition. In the present study, the global variation of sex ratio at birth (SRB, proportion of male offspring born) was analyzed with respect to indirect measure of condition, the intelligence quotient (IQ). IQ correlates strongly with lifespan across nations, which makes it a good indicator of health of the large populations. Relation between three standard measures of average national IQ and SRB was studied using multiple linear regression models. Average national IQ was positively correlated with SRB ( r = 0.54 to 0.57, p < 0.001). Further, IQ emerged as a powerful predictor of SRB after controlling for the effects of all the known covariates like fertility, maternal age, polygyny prevalence, wealth, son preference, latitude, low birth weight, and neonatal mortality in the regression models. These results suggest that the striking variation of offspring sex ratio across nations could be caused in part by the difference in general condition of populations.

  9. Sex ratios in field populations of two parasitoids (Hymenoptera: Chalcidoidea) of Coccus hesperidum L. (Homoptera: Coccidae).

    PubMed

    Bernal, Julio S; Luck, Robert F; Morse, J G

    1998-10-01

    We tested several assumptions and predictions of host-quality-dependent sex allocation theory (Charnov et al. 1981) with data obtained for the parasitoid Metaphycus stanleyi Compere on its host, brown soft scale (Coccus hesperidum L.), in a California citrus grove and in the laboratory. Scales ceased growing after parasitization by M. stanleyi. Thus, M. stanleyi may gauge host quality (=size) at oviposition. Host size positively influenced adult parasitoid size, and parasitoid size in turn influenced adult longevity of M. stanleyi. However, parasitoid fitness gains with host size and adult size were similar in males versus females. Sex allocation to individual hosts by M. stanleyi depended on host size; females consistently emerged from larger hosts than males. Host size was important in a relative sense; the mean host sizes of females versus males, and of solitary versus gregarious parasitoids varied with the available host size distribution. The offspring sex ratio of M. stanleyi reflected the available host size distribution; the sex ratio of emerging parasitoids varied with the available host size distribution. We did not detect a "critical host size" below which males emerged, and above which females emerged; rather, only females emerged from hosts in the upper size range, and a variable ratio of males and females emerged from hosts in the lower size range. We conclude that the sex ratio of field populations of M. stanleyi is driven largely by the available size distribution of C. hesperidum. In addition, we tested predictions resulting from theoretical analyses of sex allocation in autoparasitoids with data obtained on Coccophagus semicircularis (Förster) parasitizing brown soft scale in the field. The sex ratio of C. semicircularis was consistently and strongly female biased (ca. 90% females). Based on available theoretical analyses, we suggest that this sex ratio pattern may have resulted from a very low encounter rate of secondary hosts coupled with a

  10. Artificial selection on ant female caste ratio uncovers a link between female-biased sex ratios and infection by Wolbachia endosymbionts.

    PubMed

    Pontieri, L; Schmidt, A M; Singh, R; Pedersen, J S; Linksvayer, T A

    2017-02-01

    Social insect sex and caste ratios are well-studied targets of evolutionary conflicts, but the heritable factors affecting these traits remain unknown. To elucidate these factors, we carried out a short-term artificial selection study on female caste ratio in the ant Monomorium pharaonis. Across three generations of bidirectional selection, we observed no response for caste ratio, but sex ratios rapidly became more female-biased in the two replicate high selection lines and less female-biased in the two replicate low selection lines. We hypothesized that this rapid divergence for sex ratio was caused by changes in the frequency of infection by the heritable bacterial endosymbiont Wolbachia, because the initial breeding stock varied for Wolbachia infection, and Wolbachia is known to cause female-biased sex ratios in other insects. Consistent with this hypothesis, the proportions of Wolbachia-infected colonies in the selection lines changed rapidly, mirroring the sex ratio changes. Moreover, the estimated effect of Wolbachia on sex ratio (~13% female bias) was similar in colonies before and during artificial selection, indicating that this Wolbachia effect is likely independent of the effects of artificial selection on other heritable factors. Our study provides evidence for the first case of endosymbiont sex ratio manipulation in a social insect.

  11. Raised mortality from lung cancer and high sex ratios of births associated with industrial pollution.

    PubMed Central

    Lloyd, O L; Smith, G; Lloyd, M M; Holland, Y; Gailey, F

    1985-01-01

    Geographical and temporal associations were shown between high mortality from lung cancer and a high sex ratio of births both in the town of Bathgate (Scotland) and in the area of that town which was most exposed to polluted air from a local steel foundry. These findings constituted a replication of a similar association in an adjacent town. PMID:4015995

  12. Did the 1991-1995 wars in the former Yugoslavia affect sex ratio at birth?

    PubMed

    Polasek, Ozren

    2006-01-01

    Proportion of males at birth (commonly referred to as the sex ratio) has been investigated for countries of former Yugoslavia that were affected by the 1991-1995 wars. Number of live births for Slovenia, Croatia, Bosnia and Herzegovina with Serbian Republic, and Serbia and Montenegro were obtained from the official vital statistics data and analysed with the Chi-square test. Results yielded no difference in the sex ratio associated with the war for the entire data set. However, country level data analysis revealed a significant increase in Bosnia and Herzegovina with the Serbian Republic, where proportion of male births during the wartime reached as high as 0.523 (compared to 0.516 in the pre-war and 0.515 in the post-war period). Countries that were involved in either mild or intermediate level of warfare did not exhibit a significant increase in the sex ratio (e.g. Slovenia and Croatia). Although war in Croatia lasted a year longer than in Bosnia and Herzegovina, analysis of the most intensive wartime periods in Croatia did not yield significant change. It seems that a hypothetical threshold of the warfare intensity combined with duration has to be reached (e.g. as in case of Bosnia and Herzegovina), in order for war to influence the sex ratio.

  13. Female starlings adjust primary sex ratio in response to aromatic plants in the nest.

    PubMed Central

    Polo, Vicente; Veiga, José P.; Cordero, Pedro J.; Viñuela, Javier; Monaghan, Pat

    2004-01-01

    Adjustment of offspring sex ratios should be favoured by natural selection when parents are capable of facultatively altering brood sex ratios and of recognizing the circumstances that predict the probable fitness benefit of producing sons and daughters. Although experimental studies have shown that female birds may adjust offspring sex ratios in response to changes in their own condition and in the external appearance of their mate, and male attributes other than his external morphology are also thought to act as signals of male quality, it is not known whether females will respond to changes in such signals, in the absence of any change in the appearance of the male himself. Here, we experimentally manipulated a male courtship display, the green plants carried to the nest by male spotless starlings (Sturnus unicolor), without changing any physical attributes of the male himself, and examined whether this influenced female decisions on offspring sex ratio. We found that in an environment in which female starlings were producing more daughters than sons, experimental enhancement of the green nesting material caused females to significantly increase the number of male eggs produced and thereby removed the female bias. This effect was consistent in 2 years and at two localities. This demonstrates that the green material, whose function has long puzzled biologists, conveys important information to the female and that she facultatively adjusts offspring production accordingly. PMID:15347516

  14. Non-quantitative adjustment of offspring sex ratios in pollinating fig wasps

    PubMed Central

    Wang, Rui-Wu; Sun, Bao-Fa; He, Jun-Zhou; Dunn, Derek W.

    2015-01-01

    Fig wasp is one of the most well known model systems in examining whether or not the parents could adjust their offspring sex ratio to maximize their gene frequency transmission in next generations. Our manipulative experiments showed that, in all of the five pollinator wasps of figs (Agaonidae) that have different averages of foundress numbers per syconium, almost the same proportions of male offspring are produced in the experiment that foundresses deposit one hour then are killed with ether (66.1%–70.1%) and over the lifespan of each foundress (14.0%–21.0%). The foundresses tend to deposit their male eggs prior to female eggs. The observed increase in the proportion of male offspring as a function of foundress number results from density-dependent interference competition among the foundresses. These results showed that the selection of gene frequency transmission through the behavioral adjustment in the evolution of sex ratio does not exist in these five fig wasps. The results here implied that genetic adjustment mechanisms of the sex ratio of fig wasps can only be triggered to be on or off and that the foundresses can not quantitatively adjust their sex ratio according to increased environmental selection pressure. PMID:26293349

  15. Non-quantitative adjustment of offspring sex ratios in pollinating fig wasps.

    PubMed

    Wang, Rui-Wu; Sun, Bao-Fa; He, Jun-Zhou; Dunn, Derek W

    2015-08-21

    Fig wasp is one of the most well known model systems in examining whether or not the parents could adjust their offspring sex ratio to maximize their gene frequency transmission in next generations. Our manipulative experiments showed that, in all of the five pollinator wasps of figs (Agaonidae) that have different averages of foundress numbers per syconium, almost the same proportions of male offspring are produced in the experiment that foundresses deposit one hour then are killed with ether (66.1%-70.1%) and over the lifespan of each foundress (14.0%-21.0%). The foundresses tend to deposit their male eggs prior to female eggs. The observed increase in the proportion of male offspring as a function of foundress number results from density-dependent interference competition among the foundresses. These results showed that the selection of gene frequency transmission through the behavioral adjustment in the evolution of sex ratio does not exist in these five fig wasps. The results here implied that genetic adjustment mechanisms of the sex ratio of fig wasps can only be triggered to be on or off and that the foundresses can not quantitatively adjust their sex ratio according to increased environmental selection pressure.

  16. The changing sex ratios at birth during the civil war in Tajikistan: 1992-1997.

    PubMed

    Hohmann, Sophie; Roche, Sophie; Garenne, Michel

    2010-11-01

    Sex ratios at birth are known to change during wars or shortly after. This study investigated changes in sex ratios during the civil war that occurred in Tajikistan after the dismantling of the Soviet Union. This civil war was particularly bloody and long lasting, and had many demographic consequences. According to vital registration data, some 27,000 persons died in excess of previous trends during the civil war period (1992-1997), and total mortality was sometimes estimated to be three times higher by independent observers. Birth rates dropped markedly during the war, and sex ratios at birth increased significantly from 104.6 before the war to 106.9 during the war, to return to baseline values afterwards. The change in sex ratio is investigated according to demographic evidence (migration, delayed marriage, spouse separation), substantiated with qualitative evidence (difficulties with food supply), and compared with patterns found in Europe during World War II, as well as with recent wars in the Middle East.

  17. Sex Ratio at Birth and Infant Mortality Rate in China: An Empirical Study

    ERIC Educational Resources Information Center

    Lai, Denjian

    2005-01-01

    In this article, we used the data from the last three population censuses of China in 1982, 1990 and 2000, to study the dynamics of the sex ratio at birth and the infant mortality rate in China. In the late 1970s, China started its economic reform and implemented many family planning programs. Since then there has been great economic development…

  18. Too Many Men? Sex Ratios and Women's Partnering Behavior in China

    ERIC Educational Resources Information Center

    Trent, Katherine; South, Scott J.

    2011-01-01

    The relative numbers of women and men are changing dramatically in China, but the consequences of these imbalanced sex ratios have received little empirical attention. We merge data from the Chinese Health and Family Life Survey with community-level data from Chinese censuses to examine the relationship between cohort- and community-specific sex…

  19. Lunar cycles at mating do not influence sex ratio at birth in horses.

    PubMed

    Aguilar, J J; Cuervo-Arango, J; Santa Juliana, L

    2015-02-01

    It is scientifically demonstrated that lunar cycles have important effects on several biological events. Controversy exists about the lunar influence on human and animal parturition. In addition, in the horse industry, especially in Polo Horse breeders of Argentina and around the world there is a higher demand for female offspring than for males. The objective of this study was to determine whether there is a significant association between the lunar phase at the time of mating and the sex ratio at birth in horses. The Argentinean Stud Book provided information related to all matings registered for Thoroughbred and Arab horses between 2003 and 2011. Statistical associations were tested between dates of matings at different lunar phases or days and sex ratio at birth. A total of 65.535 gestations were studied. Overall, sex ratio at birth resulted in 33.396 fillies (50.96%) and 32.139 colts (49.04%). The percentages of males and females at birth were not statistically different amongst the different lunar phases or days. We can strongly conclude that managing the breeding dates in relation to lunar cycles in order to manipulate the sex ratio of the offspring is not a viable option in horses.

  20. Age-Specific Sex-Related Differences in Infections: A Statistical Analysis of National Surveillance Data in Japan

    PubMed Central

    Eshima, Nobuoki; Tokumaru, Osamu; Hara, Shohei; Bacal, Kira; Korematsu, Seigo; Karukaya, Shigeru; Uruma, Kiyo; Okabe, Nobuhiko; Matsuishi, Toyojiro

    2012-01-01

    Background To prevent and control infectious diseases, it is important to understand how sex and age influence morbidity rates, but consistent clear descriptions of differences in the reported incidence of infectious diseases in terms of sex and age are sparse. Methods and Findings Data from the Japanese surveillance system for infectious diseases from 2000 to 2009 were used in the analysis of seven viral and four bacterial infectious diseases with relatively large impact on the Japanese community. The male-to-female morbidity (MFM) ratios in different age groups were estimated to compare incidence rates of symptomatic reported infection between the sexes at different ages. MFM ratios were >1 for five viral infections out of seven in childhood, i.e. male children were more frequently reported as infected than females with pharyngoconjunctival fever, herpangina, hand-foot-and-mouth disease, mumps, and varicella. More males were also reported to be infected with erythema infectiosum and exanthema subitum, but only in children 1 year of age. By contrast, in adulthood the MFM ratios decreased to <1 for all of the viral infections above except varicella, i.e. adult women were more frequently reported to be infected than men. Sex- and age-related differences in reported morbidity were also documented for bacterial infections. Reported morbidity for enterohemorrhagic Escherichia coli infection was higher in adult females and females were reportedly more infected with mycoplasma pneumonia than males in all age groups up to 70 years. Conclusions Sex-related differences in reported morbidity for viral and bacterial infections were documented among different age groups. Changes in MFM ratios with age may reflect differences between the sexes in underlying development processes, including those affecting the immune, endocrine, and reproductive systems, or differences in reporting rates. PMID:22848753

  1. [Methodological note on subnational population projections by age and sex (author's transl)].

    PubMed

    Itoh, T

    1980-07-01

    The purposes of this paper were to discuss the methods and assumptions on subnational population projections by age and sex, and to present 2 models on population projection for 47 Prefectures in Japan by age and sex up to 2000. Data are obtained from the results of the 1970 and 1975 population censuses of Japan for population by age and sex, and interprefectural migration streams by age and sex based on the 1970 population census. The 2 models are a sort of cohort-component method: 1 is the (NMR) net-migration model and the other is the (MTX) migration matrix model. The essential difference between the 2 is the separate consideration of out- and inmigration models. The formulas for estimating numbers of net migration in the NMR model are (4) and (5) in the text, where P is the number of the population, S is the life table survival ratios, and m is the rate of net migration. The formulas for estimating numbers of outmigration, migration streams from region i to region j, and inmigration, in the MTX model are (17)-(21), where E is the numbers of outmigration, e is the rate of outmigration, m (i,j) is the proportion of the number of migrants from i to j to total numbers of outmigrants from region i, and I is the numbers of inmigration for each region. Under constant conditions, for all rates, the projected population for 47 prefectures by age and sex up to 2000 using models NMR and MTX was obtained. The projected number of population in 2000 are shown in figures on pages 66 and 67. As the results of these projections, the increase in aged population between 1975-200 in the metropolitan areas, especially Tokyo (1), are greater than that in other areas, since the concentration of the young in the 3 metropolitan areas has rapidly dropped since 1950. (Author's modified)

  2. Temporal variability of local abundance, sex ratio and activity in the Sardinian chalk hill blue butterfly

    USGS Publications Warehouse

    Casula, P.; Nichols, J.D.

    2003-01-01

    When capturing and marking of individuals is possible, the application of newly developed capture-recapture models can remove several sources of bias in the estimation of population parameters such as local abundance and sex ratio. For example, observation of distorted sex ratios in counts or captures can reflect either different abundances of the sexes or different sex-specific capture probabilities, and capture-recapture models can help distinguish between these two possibilities. Robust design models and a model selection procedure based on information-theoretic methods were applied to study the local population structure of the endemic Sardinian chalk hill blue butterfly, Polyommatus coridon gennargenti. Seasonal variations of abundance, plus daily and weather-related variations of active populations of males and females were investigated. Evidence was found of protandry and male pioneering of the breeding space. Temporary emigration probability, which describes the proportion of the population not exposed to capture (e.g. absent from the study area) during the sampling process, was estimated, differed between sexes, and was related to temperature, a factor known to influence animal activity. The correlation between temporary emigration and average daily temperature suggested interpreting temporary emigration as inactivity of animals. Robust design models were used successfully to provide a detailed description of the population structure and activity in this butterfly and are recommended for studies of local abundance and animal activity in the field.

  3. A CRISPR-Cas9 sex-ratio distortion system for genetic control

    PubMed Central

    Galizi, Roberto; Hammond, Andrew; Kyrou, Kyros; Taxiarchi, Chrysanthi; Bernardini, Federica; O’Loughlin, Samantha M.; Papathanos, Philippos-Aris; Nolan, Tony; Windbichler, Nikolai; Crisanti, Andrea

    2016-01-01

    Genetic control aims to reduce the ability of insect pest populations to cause harm via the release of modified insects. One strategy is to bias the reproductive sex ratio towards males so that a population decreases in size or is eliminated altogether due to a lack of females. We have shown previously that sex ratio distortion can be generated synthetically in the main human malaria vector Anopheles gambiae, by selectively destroying the X-chromosome during spermatogenesis, through the activity of a naturally-occurring endonuclease that targets a repetitive rDNA sequence highly-conserved in a wide range of organisms. Here we describe a CRISPR-Cas9 sex distortion system that targets ribosomal sequences restricted to the member species of the Anopheles gambiae complex. Expression of Cas9 during spermatogenesis resulted in RNA-guided shredding of the X-chromosome during male meiosis and produced extreme male bias among progeny in the absence of any significant reduction in fertility. The flexibility of CRISPR-Cas9 combined with the availability of genomic data for a range of insects renders this strategy broadly applicable for the species-specific control of any pest or vector species with an XY sex-determination system by targeting sequences exclusive to the female sex chromosome. PMID:27484623

  4. Female-Bias in a Long-Term Study of a Species with Temperature-Dependent Sex Determination: Monitoring Sex Ratios for Climate Change Research

    PubMed Central

    Braun McNeill, Joanne; Avens, Larisa; Goodman Hall, April; Goshe, Lisa R.; Harms, Craig A.; Owens, David W.

    2016-01-01

    Alterations have occurred and continue to manifest in the Earth’s biota as a result of climate change. Animals exhibiting temperature dependent sex determination (TSD), including sea turtles, are perhaps most vulnerable to a warming of the Earth as highly skewed sex ratios can result, potentially leading to population extinction resulting from decreased male recruitment. Recent studies have begun to quantify climate change impacts to sea turtle populations, especially in terms of predicting effects on hatchling sex ratios. However, given the inherent difficulty in studying sex ratios at this life stage, a more accurate assessment of changes in population sex ratios might be derived by evaluating the juvenile portion of foraging aggregations. We investigated the long-term trend in sex ratio of a juvenile loggerhead (Caretta caretta) sea turtle population inhabiting Pamlico and Core Sounds, North Carolina, USA. We used plasma testosterone reference ranges measured using radioimmunoassay (RIA) to assign sex for 959 turtles and confirmed sex assignment of a subset (N = 58) of the sampled turtles through laparoscopic examination of their gonads. Our results demonstrate that for this particular population of loggerheads, sex ratios (3Females:1Male) had not significantly changed over a 10 year period (1998–2007), nor showed any significant difference among 5-cm straight carapace length (SCL) size classes. Ultimately, these findings provide a basis for comparison with future sex ratios, and highlight the importance of establishing similar long-term studies monitoring secondary, rather than primary, sex ratios, so that needed mitigation measures to climate change impacts can be implemented. PMID:27579608

  5. Female-Bias in a Long-Term Study of a Species with Temperature-Dependent Sex Determination: Monitoring Sex Ratios for Climate Change Research.

    PubMed

    Braun McNeill, Joanne; Avens, Larisa; Goodman Hall, April; Goshe, Lisa R; Harms, Craig A; Owens, David W

    2016-01-01

    Alterations have occurred and continue to manifest in the Earth's biota as a result of climate change. Animals exhibiting temperature dependent sex determination (TSD), including sea turtles, are perhaps most vulnerable to a warming of the Earth as highly skewed sex ratios can result, potentially leading to population extinction resulting from decreased male recruitment. Recent studies have begun to quantify climate change impacts to sea turtle populations, especially in terms of predicting effects on hatchling sex ratios. However, given the inherent difficulty in studying sex ratios at this life stage, a more accurate assessment of changes in population sex ratios might be derived by evaluating the juvenile portion of foraging aggregations. We investigated the long-term trend in sex ratio of a juvenile loggerhead (Caretta caretta) sea turtle population inhabiting Pamlico and Core Sounds, North Carolina, USA. We used plasma testosterone reference ranges measured using radioimmunoassay (RIA) to assign sex for 959 turtles and confirmed sex assignment of a subset (N = 58) of the sampled turtles through laparoscopic examination of their gonads. Our results demonstrate that for this particular population of loggerheads, sex ratios (3Females:1Male) had not significantly changed over a 10 year period (1998-2007), nor showed any significant difference among 5-cm straight carapace length (SCL) size classes. Ultimately, these findings provide a basis for comparison with future sex ratios, and highlight the importance of establishing similar long-term studies monitoring secondary, rather than primary, sex ratios, so that needed mitigation measures to climate change impacts can be implemented.

  6. Quantifying the relative risk of sex offenders: risk ratios for static-99R.

    PubMed

    Hanson, R Karl; Babchishin, Kelly M; Helmus, Leslie; Thornton, David

    2013-10-01

    Given the widespread use of empirical actuarial risk tools in corrections and forensic mental health, it is important that evaluators and decision makers understand how scores relate to recidivism risk. In the current study, we found strong evidence for a relative risk interpretation of Static-99R scores using 8 samples from Canada, United Kingdom, and Western Europe (N = 4,037 sex offenders). Each increase in Static-99R score was associated with a stable and consistent increase in relative risk (as measured by an odds ratio or hazard ratio of approximately 1.4). Hazard ratios from Cox regression were used to calculate risk ratios that can be reported for Static-99R. We recommend that evaluators consider risk ratios as a useful, nonarbitrary metric for quantifying and communicating risk information. To avoid misinterpretation, however, risk ratios should be presented with recidivism base rates.

  7. Logging affects fledgling sex ratios and baseline corticosterone in a forest songbird.

    PubMed

    Leshyk, Rhiannon; Nol, Erica; Burke, Dawn M; Burness, Gary

    2012-01-01

    Silviculture (logging) creates a disturbance to forested environments. The degree to which forests are modified depends on the logging prescription and forest stand characteristics. In this study we compared the effects of two methods of group-selection ("moderate" and "heavy") silviculture (GSS) and undisturbed reference stands on stress and offspring sex ratios of a forest interior species, the Ovenbird (Seiurus aurocapilla), in Algonquin Provincial Park, Canada. Blood samples were taken from nestlings for corticosterone and molecular sexing. We found that logging creates a disturbance that is stressful for nestling Ovenbirds, as illustrated by elevated baseline corticosterone in cut sites. Ovenbirds nesting in undisturbed reference forest produce fewer male offspring per brood (proportion male = 30%) while logging with progressively greater forest disturbance, shifted the offspring sex ratio towards males (proportion male: moderate = 50%, heavy = 70%). If Ovenbirds in undisturbed forests usually produce female-biased broods, then the production of males as a result of logging may disrupt population viability. We recommend a broad examination of nestling sex ratios in response to anthropogenic disturbance to determine the generality of our findings.

  8. Logging Affects Fledgling Sex Ratios and Baseline Corticosterone in a Forest Songbird

    PubMed Central

    Leshyk, Rhiannon; Nol, Erica; Burke, Dawn M.; Burness, Gary

    2012-01-01

    Silviculture (logging) creates a disturbance to forested environments. The degree to which forests are modified depends on the logging prescription and forest stand characteristics. In this study we compared the effects of two methods of group-selection (“moderate” and “heavy”) silviculture (GSS) and undisturbed reference stands on stress and offspring sex ratios of a forest interior species, the Ovenbird (Seiurus aurocapilla), in Algonquin Provincial Park, Canada. Blood samples were taken from nestlings for corticosterone and molecular sexing. We found that logging creates a disturbance that is stressful for nestling Ovenbirds, as illustrated by elevated baseline corticosterone in cut sites. Ovenbirds nesting in undisturbed reference forest produce fewer male offspring per brood (proportion male = 30%) while logging with progressively greater forest disturbance, shifted the offspring sex ratio towards males (proportion male: moderate = 50%, heavy = 70%). If Ovenbirds in undisturbed forests usually produce female-biased broods, then the production of males as a result of logging may disrupt population viability. We recommend a broad examination of nestling sex ratios in response to anthropogenic disturbance to determine the generality of our findings. PMID:22432000

  9. The human operational sex ratio: effects of marriage, concealed ovulation, and menopause on mate competition.

    PubMed

    Marlowe, Frank W; Berbesque, J Colette

    2012-12-01

    Among mammals, male-male competition for sexual access to females frequently involves fighting. Larger body size gives males an advantage in fighting, which explains why males tend to be larger than females in many species, including anthropoid primates. Mitani et al. derived a formula to measure the operational sex ratio (OSR) to reflect the degree of male-male competition using the number of reproductively available males to females who are cycling and capable of conceiving. The OSR should predict the degree of sexual dimorphism in body mass-at least if male-male competition involves much fighting or threatening. Here, we use hunter-gatherer demographic data and the Mitani et al. formula to calculate the human OSR. We show that humans have a much lower degree of body mass sexual dimorphism than is predicted by our OSR. We suggest this is because human competition rarely involves fighting. In human hunter-gatherer societies, differences in the ages of marriage have an impact on competition in that the age of males at first marriage is younger when there is a lower percentage of married men with two or more wives, and older when there is a higher percentage of married men with two or more wives. We discuss the implications of this for females, along with the effects of two key life history traits that influence the OSR, concealed ovulation and menopause. While menopause decreases the number of reproductively available females to males and thus increases male-male competition, concealed ovulation decreases male-male competition. Finally, we discuss the importance of mostly monogamous mate bonds in human evolution.

  10. Effects of diets supplemented by fish oil on sex ratio of pups in bitch

    PubMed Central

    Gharagozlou, Faramarz; Youssefi, Reza; Akbarinejad, Vahid

    2016-01-01

    The present study was conducted to evaluate the effect of fish oil supplementation prior to mating on secondary sex ratio of pups (the proportion of males at birth) in bitches. Sixty five bitches (German Shepherd, n = 35; Husky, n = 30) were enrolled in the study. Bitches (140-150 days post-estrus) were given 2% per dry matter intake palm oil and fish oil in the control (n = 33) and treatment (n = 32) groups, respectively. To induce estrus, bitches were received equine chorionic gonadotropin (eCG) administration (50 IU kg-1) 30 days after nutritional supplementation followed by human chorionic gonadotropin (hCG) administration (500 IU per dog) seven days later. Bitches were introduced to dogs of the same breed after hCG administration. The weight of bitches was increased over time (p < 0.05), but their weight change was not different between two groups (p > 0.05). The mating rate, pregnancy rate and litter size were not influenced by treatment and breed. Secondary sex ratio was higher in the treatment (105/164; 64.00%) than in the control (68/147; 46.30%) group (p < 0.05; adjusted odds ratio = 2.068). Moreover, secondary sex ratio was higher in Husky bitches (88/141; 62.40%) compared to German Shepherd (85/170; 50.00%; p < 0.05; adjusted odds ratio = 1.661). In conclusion, the present study showed that inclusion of fish oil in the diet of bitches prior to mating could increase the proportion of male pups at birth. In addition, it appears that there might be variation among dog breeds with regard to the sex ratio of offspring. PMID:27482354

  11. Effects of diets supplemented by fish oil on sex ratio of pups in bitch.

    PubMed

    Gharagozlou, Faramarz; Youssefi, Reza; Akbarinejad, Vahid

    2016-01-01

    The present study was conducted to evaluate the effect of fish oil supplementation prior to mating on secondary sex ratio of pups (the proportion of males at birth) in bitches. Sixty five bitches (German Shepherd, n = 35; Husky, n = 30) were enrolled in the study. Bitches (140-150 days post-estrus) were given 2% per dry matter intake palm oil and fish oil in the control (n = 33) and treatment (n = 32) groups, respectively. To induce estrus, bitches were received equine chorionic gonadotropin (eCG) administration (50 IU kg(-1)) 30 days after nutritional supplementation followed by human chorionic gonadotropin (hCG) administration (500 IU per dog) seven days later. Bitches were introduced to dogs of the same breed after hCG administration. The weight of bitches was increased over time (p < 0.05), but their weight change was not different between two groups (p > 0.05). The mating rate, pregnancy rate and litter size were not influenced by treatment and breed. Secondary sex ratio was higher in the treatment (105/164; 64.00%) than in the control (68/147; 46.30%) group (p < 0.05; adjusted odds ratio = 2.068). Moreover, secondary sex ratio was higher in Husky bitches (88/141; 62.40%) compared to German Shepherd (85/170; 50.00%; p < 0.05; adjusted odds ratio = 1.661). In conclusion, the present study showed that inclusion of fish oil in the diet of bitches prior to mating could increase the proportion of male pups at birth. In addition, it appears that there might be variation among dog breeds with regard to the sex ratio of offspring.

  12. Otter scent signals age, sex, and reproductive status.

    PubMed

    Kean, Eleanor F; Müller, Carsten T; Chadwick, Elizabeth A

    2011-07-01

    Scent is used across taxa to communicate information about signaler identity. Eurasian otters Lutra lutra are mainly solitary and thought to use scent as their primary means of communication. Little is known, however, about what information otters communicate through scent or what social function this performs. Headspace solid-phase microextraction and gas chromatography-mass spectrometry were used to sample and analyze volatile organic compounds from anal scent gland secretion from 158 otters of differing sex, age, and female reproductive status. Univariate and multivariate differences were clear between adult and juvenile otters. Complex sex differences were apparent in adult otters but not in younger individuals, suggesting the use of this scent secretion in mate attraction. The scent of pregnant and lactating females was highly differentiated from male and juvenile scent, but anecdotal reports suggest females avoid communication during these times.

  13. Ploidy, sex and crossing over in an evolutionary aging model

    NASA Astrophysics Data System (ADS)

    Lobo, Matheus P.; Onody, Roberto N.

    2006-02-01

    Nowadays, many forms of reproduction coexist in nature: Asexual, sexual, apomictic and meiotic parthenogenesis, hermaphroditism and parasex. The mechanisms of their evolution and what made them successful reproductive alternatives are very challenging and debated questions. Here, using a simple evolutionary aging model, we give a possible scenario. By studying the performance of populations where individuals may have diverse characteristics-different ploidies, sex with or without crossing over, as well as the absence of sex-we find an evolution sequence that may explain why there are actually two major or leading groups: Sexual and asexual. We also investigate the dependence of these characteristics on different conditions of fertility and deleterious mutations. Finally, if the primeval organisms on Earth were, in fact, asexual individuals we conjecture that the sexual form of reproduction could have more easily been set and found its niche during a period of low-intensity mutations.

  14. Population sex-ratio affecting behavior and physiology of overwintering bank voles (Myodes glareolus).

    PubMed

    Sipari, Saana; Haapakoski, Marko; Klemme, Ines; Palme, Rupert; Sundell, Janne; Ylönen, Hannu

    2016-05-15

    Many boreal rodents are territorial during the breeding season but during winter become social and aggregate for more energy efficient thermoregulation. Communal winter nesting and social interactions are considered to play an important role for the winter survival of these species, yet the topic is relatively little explored. Females are suggested to be the initiators of winter aggregations and sometimes reported to survive better than males. This could be due to the higher social tolerance observed in overwintering females than males. Hormonal status could also affect winter behavior and survival. For instance, chronic stress can have a negative effect on survival, whereas high gonadal hormone levels, such as testosterone, often induce aggressive behavior. To test if the winter survival of females in a boreal rodent is better than that of males, and to assess the role of females in the winter aggregations, we generated bank vole (Myodes glareolus) populations of three different sex ratios (male-biased, female-biased and even density) under semi-natural conditions. We monitored survival, spatial behavior and hormonal status (stress and testosterone) during two winter months. We observed no significant differences in survival between the sexes or among populations with differing sex-ratios. The degree of movement area overlap was used as an indicator of social tolerance and potential communal nesting. Individuals in male biased populations showed a tendency to be solitary, whereas in female biased populations there was an indication of winter aggregation. Females living in male-biased populations had higher stress levels than the females from the other populations. The female-biased sex-ratio induced winter breeding and elevated testosterone levels in males. Thus, our results suggest that the sex-ratio of the overwintering population can lead to divergent overwintering strategies in bank voles.

  15. Age and sex determination of juvenile band-tailed pigeons

    USGS Publications Warehouse

    White, J.A.; Braun, C.E.

    1978-01-01

    Captive band-tailed pigeons (Columbafasciata) were studied to document progression of molts and plumages from juvenal to adult age. Immature pigeons began the post-juvenal molt at 35 days which continued up to 340 days. The only 3 plumage characters useful for identification and estimation of age were presence of juvenal lesser, middle, and greater secondary coverts, juvenal secondaries, and juvenal primaries. While juvenal primaries were still present, hatching dates could be estimated up to 252 days (N = 84). Secondary feather presence and molt stage could be used to identify juvenile pigeons for more than 340 days (N = 24). Using coloration of the crown and breast feathers, 96 percent of the immature pigeons examined (106 of 110) at 80 days of age were classified accurately as to sex.

  16. Androgen receptor blockade using flutamide skewed sex ratio of litters in mice

    PubMed Central

    Gharagozlou, Faramarz; Youssefi, Reza; Vojgani, Mehdi; Akbarinejad, Vahid; Rafiee, Ghazaleh

    2016-01-01

    Maternal testosterone has been indicated to affect sex ratio of offspring. The present study was conducted to elucidate the role of androgen receptor in this regard by blockade of androgen receptor using flutamide in female mice. Mice were randomly assigned to two experimental groups. Mice in the control (n = 20) and treatment (n = 20) groups received 8 IU equine chorionic gonadotropin (eCG) followed by human chorionic gonadotropin (hCG) injection (8 IU) 47 hr later. In addition, mice in the control and treatment groups received four injections of ethanol-saline vehicle and flutamide solution (2.50 mg), respectively, started from 1 hr before eCG injection until hCG injection at 12-hr intervals. Conception rate was not different between the treatment (18/20: 90.00%) and control (19/20: 95.00%) groups (p > 0.05). Litter size was higher in the treatment (8.22 ± 0.26) than control (7.21 ± 0.28) group (p < 0.05). Male sex ratio was lower in the flutamide-treated mice (67/148: 45.30%) as compared with the untreated ones (80/137: 58.40%; odds ratio = 1.69; p < 0.05). In conclusion, the results showed that androgen receptor blockade could skew sex ratio of offspring toward females implying that the effect of testosterone on sex ratio might be through binding to androgen receptor. In addition, the blockade of androgen receptor using flutamide appeared to enhance litter size. PMID:27482363

  17. Predicted sex ratio of juvenile Hawksbill Seaturtles inhabiting Buck Island Reef national monument, U.S. Virgin Islands

    USGS Publications Warehouse

    Geis, A.; Wibbels, T.; Phillips, B.; Hillis-Starr, Z.; Meylan, A.; Meylan, P.; Diez, C.; Van Dam, R.

    2003-01-01

    Hawksbill Seaturtles have temperature-dependent sex determination. As such, the resulting sex ratios are of conservational and ecological significance. Buck Island Reef is an interesting location for sex ratio studies since it represents a natural and unexploited foraging ground for hawksbills in the Caribbean. To examine sex ratios, blood samples were obtained from juvenile Hawksbill Seaturtles captured on Buck Island Reef over a four-year period. We used a radioimmunoassay to determine testosterone levels in those samples and compared those values to testosterone levels of juvenile hawksbills from the Caribbean whose sex has been verified by laparoscopy. The results of this study reveal a significantly female-biased sex ratio (approximately 80% female) occurs in this juvenile aggregation inhabiting Buck Island Reef.

  18. Sex ratio following preconception low-dose aspirin in women with prior pregnancy loss

    PubMed Central

    Radin, Rose G.; Mumford, Sunni L.; Silver, Robert M.; Lesher, Laurie L.; Galai, Noya; Faraggi, David; Wactawski-Wende, Jean; Townsend, Janet M.; Lynch, Anne M.; Simhan, Hyagriv N.; Sjaarda, Lindsey A.; Perkins, Neil J.; Zarek, Shvetha M.; Schliep, Karen C.; Schisterman, Enrique F.

    2015-01-01

    BACKGROUND. Several lines of evidence suggest that male embryos may have greater vulnerability than female embryos to disordered inflammation; therefore, antiinflammatory drugs, such as low-dose aspirin (LDA), may alter the sex ratio. Here, we assessed the effect of LDA on male live birth and male offspring, incorporating pregnancy losses (n = 56) via genetic assessment, as part of a parallel-design, block-randomized, placebo-controlled trial of preconception LDA. METHODS. Participants (615 treated with LDA, 613 treated with placebo) ranged in age from 18 to 40 years of age, with 1 to 2 prior pregnancy losses. We estimated the intention-to-treat (ITT) risk ratio (RR) and 95% CI and assessed interaction with baseline high-sensitivity C-reactive protein (hsCRP) serum concentration — a marker of systemic inflammation. RESULTS. Among the 1,078 women who completed follow-up (535 treated with LDA, 543 treated with placebo), the male live birth ITT RR equaled 1.31 (95% CI: 1.07–1.59). With increasing tertile of hsCRP, the proportion of males at birth decreased in the placebo group, and the effect of LDA on male live birth increased (first tertile: 48% male in LDA vs. 52% in placebo, ITT RR = 0.97, 95% CI: 0.70–1.35; second tertile: 57% male in LDA vs. 43% in placebo, ITT RR = 1.36, 95% CI: 0.98–1.90; third tertile: 53% male in LDA vs. 35% in placebo, ITT RR = 1.70, 95% CI: 1.13–2.57; P interaction = 0.03). Analysis of pregnancy with male offspring yielded similar results. CONCLUSION. Initiation of LDA prior to conception restored numbers of male live births and pregnancy with male offspring among women with 1 to 2 prior pregnancy losses. Moreover, our data suggest that LDA modulates inflammation that would otherwise reduce the conception or survival of male embryos. TRIAL REGISTRATION. ClinicalTrials.gov NCT00467363. FUNDING. Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of

  19. Thermal fluctuation within nests and predicted sex ratio of Morelet's Crocodile.

    PubMed

    Escobedo-Galván, Armando H; López-Luna, Marco A; Cupul-Magaña, Fabio G

    2016-05-01

    Understanding the interplay between thermal variations and sex ratio in reptiles with temperature-dependent sex determination is the first step for developing long-term conservation strategies. In case of crocodilians, the information is fragmentary and insufficient for establishing a general framework to consider how thermal fluctuation influence sex determination under natural conditions. The main goal of this study was to analyze thermal variation in nests of Crocodylus moreletii and to discuss the potential implications for predicting offspring sex ratio. The study was carried out at the Centro de Estudios Tecnológicos del Mar N° 2 and at the Sistemas Productivos Cocodrilo, Campeche, Mexico. Data was collected in the nesting season of Morelet's Crocodiles during three consecutive seasons (2007-2009). Thermal fluctuations for multiple areas of the nest chamber were registered by data loggers. We calculate the constant temperature equivalent based on thermal profiles among nests to assess whether there are differences between the nest temperature and its equivalent to constant temperature. We observed that mean nest temperature was only different among nests, while daily thermal fluctuations vary depending on the depth position within the nest chamber, years and nests. The constant temperature equivalent was different among and within nests, but not among survey years. We observed differences between constant temperature equivalent and mean nest temperature both at the top and in the middle of the nest cavities, but were not significantly different at the bottom of nest cavities. Our results enable examine and discuss the relevance of daily thermal fluctuations to predict sex ratio of the Morelet's Crocodile.

  20. The sex ratio of full and half siblings of people diagnosed with an autism spectrum disorder: a Danish Nationwide Register Study.

    PubMed

    Mouridsen, Svend Erik; Rich, Bente; Isager, Torben

    2014-10-01

    In the extreme male brain theory of autism sex steroid hormones are hypothesized to influence brain development and to mediate sex differences in developmental psychopathology. Within this scope we examined the sex ratio (proportion of males) in siblings of individuals diagnosed with autism spectrum disorders (ASD). We did a nationwide, register based cohort study of the sex ratio in 17,380 siblings of the 10,297 patients diagnosed with ASD at age 17 years and younger and registered in the nationwide Danish Psychiatric Central Register between 1994 and 2012. Among the 17,380 siblings 8,828 were males and 8,552 females. This yields a sex ratio of 0.508, which is not different from the Danish live birth sex ratio of 0.513 during the relevant years (P = 0.18). Overall, our findings provide no support for the hypothesis that there are relatively more males among the siblings of people with ASD. Accordingly, our results do not give support to the extreme male brain theory of autism.

  1. Parental thermal environment alters offspring sex ratio and fitness in an oviparous lizard.

    PubMed

    Schwanz, Lisa E

    2016-08-01

    The environment experienced by parents can impact the phenotype of their offspring (parental effects), a critical component of organismal ecology and evolution in variable or changing environments. Although temperature is a central feature of the environment for ectotherms, its role in parental effects has been little explored until recently. Here, parental basking opportunity was manipulated in an oviparous lizard with temperature-dependent sex determination, the jacky dragon (Amphibolurus muricatus). Eggs were incubated at a temperature that typically produces a 50:50 sex ratio, and hatchlings were reared in a standard thermal environment. Offspring of parents in short bask conditions appeared to have better fitness outcomes in captive conditions than those of parents in long bask conditions - they had greater growth and survival as a function of their mass. In addition, the sex of offspring (male or female) depended on the interaction between parental treatment and egg mass, and treatment impacted whether sons or daughters grew larger in their first season. The interactive effects of treatment on offspring sex and growth are consistent with adaptive explanations for the existence of temperature-dependent sex determination in this species. Moreover, the greater performance recorded in short bask offspring may represent an anticipatory parental effect to aid offspring in predicted conditions of restricted thermal opportunity. Together, these responses constitute a crucial component of the population response to spatial or temporal variation in temperature.

  2. Effects of sex and age on auditory spatial scene analysis.

    PubMed

    Lewald, Jörg; Hausmann, Markus

    2013-05-01

    Recently, it has been demonstrated that men outperform women in spatial analysis of complex auditory scenes (Zündorf et al., 2011). The present study investigated the relation between the effects of ageing and sex on the spatial segregation of concurrent sounds in younger and middle-aged adults. The experimental design allowed simultaneous presentation of target and distractor sound sources at different locations. The resulting spatial "pulling" effect (that is, the bias of target localization toward that of the distractor) was used as a measure of performance. The pulling effect was stronger in middle-aged than younger subjects, and female than male subjects. This indicates lower performance of the middle-aged women in the sensory and attentional mechanisms extracting spatial information about the acoustic event of interest from the auditory scene than both younger and male subjects. Moreover, age-specific differences were most prominent for conditions with targets in right hemispace and distractors in left hemispace, suggesting bilateral asymmetries underlying the effect of ageing.

  3. Effects of thyroid endocrine manipulation on sex-related gene expression and population sex ratios in Zebrafish

    USGS Publications Warehouse

    Sharma, Prakash; Tang, Song; Mayer, Gregory D.; Patino, Reynaldo

    2016-01-01

    Thyroid hormone reportedly induces masculinization of genetic females and goitrogen treatment delays testicular differentiation (ovary-to-testis transformation) in genetic males of Zebrafish. This study explored potential molecular mechanisms of these phenomena. Zebrafish were treated with thyroxine (T4, 2 nM), goitrogen [methimazole (MZ), 0.15 mM], MZ (0.15 mM) and T4 (2 nM) (rescue treatment), or reconstituted water (control) from 3 to 33 days postfertilization (dpf) and maintained in control water until 45 dpf. Whole fish were collected during early (25 dpf) and late (45 dpf) testicular differentiation for transcript abundance analysis of selected male (dmrt1, amh, ar) and female (cyp19a1a, esr1, esr2a, esr2b) sex-related genes by quantitative RT-PCR, and fold-changes relative to control values were determined. Additional fish were sampled at 45 dpf for histological assessment of gonadal sex. The T4 and rescue treatments caused male-biased populations, and T4 alone induced precocious puberty in ∼50% of males. Male-biased sex ratios were accompanied by increased expression of amh and ar and reduced expression of cyp19a1a, esr1, esr2a, and esr2b at 25 and 45 dpf and, unexpectedly, reduced expression of dmrt1 at 45 dpf. Goitrogen exposure increased the proportion of individuals with ovaries (per previous studies interpreted as delay in testicular differentiation of genetic males), and at 25 and 45 dpf reduced the expression of amh and ar and increased the expression of esr1 (only at 25 dpf), esr2a, and esr2b. Notably, cyp19a1a transcript was reduced but via non-thyroidal pathways (not restored by rescue treatment). In conclusion, the masculinizing activity of T4 at the population level may be due to its ability to inhibit female and stimulate male sex-related genes in larvae, while the inability of MZ to induce cyp19a1a, which is necessary for ovarian differentiation, may explain why its “feminizing” activity on gonadal

  4. An evaluation of sex-age-kill (SAK) model performance

    USGS Publications Warehouse

    Millspaugh, Joshua J.; Skalski, John R.; Townsend, Richard L.; Diefenbach, Duane R.; Boyce, Mark S.; Hansen, Lonnie P.; Kammermeyer, Kent

    2009-01-01

    The sex-age-kill (SAK) model is widely used to estimate abundance of harvested large mammals, including white-tailed deer (Odocoileus virginianus). Despite a long history of use, few formal evaluations of SAK performance exist. We investigated how violations of the stable age distribution and stationary population assumption, changes to male or female harvest, stochastic effects (i.e., random fluctuations in recruitment and survival), and sampling efforts influenced SAK estimation. When the simulated population had a stable age distribution and λ > 1, the SAK model underestimated abundance. Conversely, when λ < 1, the SAK overestimated abundance. When changes to male harvest were introduced, SAK estimates were opposite the true population trend. In contrast, SAK estimates were robust to changes in female harvest rates. Stochastic effects caused SAK estimates to fluctuate about their equilibrium abundance, but the effect dampened as the size of the surveyed population increased. When we considered both stochastic effects and sampling error at a deer management unit scale the resultant abundance estimates were within ±121.9% of the true population level 95% of the time. These combined results demonstrate extreme sensitivity to model violations and scale of analysis. Without changes to model formulation, the SAK model will be biased when λ ≠ 1. Furthermore, any factor that alters the male harvest rate, such as changes to regulations or changes in hunter attitudes, will bias population estimates. Sex-age-kill estimates may be precise at large spatial scales, such as the state level, but less so at the individual management unit level. Alternative models, such as statistical age-at-harvest models, which require similar data types, might allow for more robust, broad-scale demographic assessments.

  5. Contrasting brood-sex ratio flexibility in two opiine (Hymenoptera: Braconidae) parasitoids of tephritid (Diptera) fruit files

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mass-rearing of fruit fly parasitoids for augmentative release would be more economical if production could be biased towards females. If sex ratios are ever to be manipulated under rearing conditions it is important to determine if, then understand why, sex ratio flexibility exists. Unequal brood-s...

  6. Sex ratio of mirid populations shifts in response to hostplant co-infestation or altered cytokinin signaling .

    PubMed

    Adam, Nora; Erler, Theresa; Kallenbach, Mario; Kaltenpoth, Martin; Kunert, Grit; Baldwin, Ian T; Schuman, Meredith C

    2017-01-01

    Herbivore species sharing a host plant often compete. In this study, we show that host plant-mediated interaction between two insect herbivores - a generalist and a specialist - results in a sex ratio shift of the specialist's offspring. We studied demographic parameters of the specialist Tupiocoris notatus (Hemiptera: Miridae) when co-infesting the host plant Nicotiana attenuata (Solanaceae) with the generalist leafhopper Empoasca sp. (Hemiptera: Cicadellidae). We show that the usually female-biased sex ratio of T. notatus shifts toward a higher male proportion in the offspring on plants co-infested by Empoasca sp. This sex ratio change did not occur after oviposition, nor is it due differential mortality of female and male nymphs. Based on pyrosequencing and PCR of bacterial 16S rRNA amplicons, we concluded that sex ratio shifts were unlikely to be due to infection with Wolbachia or other known sex ratio-distorting endosymbionts. Finally, we used transgenic lines of N. attenuata to evaluate if the sex ratio shift could be mediated by changes in general or specialized host plant metabolites. We found that the sex ratio shift occurred on plants deficient in two cytokinin receptors (irCHK2/3). Thus, cytokinin-regulated traits can alter the offspring sex ratio of the specialist T. notatus.

  7. Mutually beneficial host exploitation and ultra-biased sex ratios in quasisocial parasitoids

    PubMed Central

    Tang, Xiuyun; Meng, Ling; Kapranas, Apostolos; Xu, Fuyuan; Hardy, Ian C.W.; Li, Baoping

    2014-01-01

    Selfish interests usually preclude resource sharing, but under some conditions collective actions enhance per capita gains. Such Allee effects underlay early explanations of social evolution but current understanding focusses on kin selection (inclusive fitness). We find an Allee effect that explains unusual quasisociality (cooperative brood care) among parasitoid wasps without invoking or precluding kin selection effects. In Sclerodermus harmandi, individual females produce most offspring when exploiting small hosts alone. However, larger hosts are more successfully exploited by larger groups of females, with the per-female benefits outweighing the costs of host sharing. Further, the extremely biased sex ratios (97% female) are better explained by mutually beneficial female–female interactions that increase the reproductive value of daughters (local resource enhancement), rather than by the usually invoked local mate competition between males. Thus, atypical quasisocial behaviour in a parasitoid wasp directly enhances reproductive success and selects for very extremely female-biased sex ratios. PMID:25216091

  8. Temporal and regional trends in the secondary sex ratio: The Nordic experience.

    PubMed

    Fellman, Johan

    2015-12-01

    The sex ratio (SR) at birth, also known as the secondary sex ratio, is defined as the number of males per 100 females and approximates 106. According to the literature, the SR shows notable heterogeneity and attempts have been made to identify factors influencing it, but comparisons demand large data sets. Attempts to identify associations between SRs and stillbirth rates (SBRs) have yielded inconsistent results. A common pattern observed in different countries is that during the first half of the twentieth century, the SR showed increasing trends, but during the second half, the trend decreased. Secular increases are thought to be caused by improved socio-economic conditions. The recent downward trends have been attributed to new reproductive hazards. Similar findings have been made in the Nordic countries. Factors affecting the SR within families remain poorly understood. Although these factors have an effect on family data, they have not been identified in large.

  9. Driving a hard bargain: sex ratio and male marriage success in a historical US population.

    PubMed

    Pollet, Thomas V; Nettle, Daniel

    2008-02-23

    Evolutionary psychologists have documented a widespread female preference for men of high status and resources, and evidence from several populations suggests that this preference has real effects on marriage success. Here, we show that in the US population of 1910, socioeconomic status (SES) had a positive effect on men's chances of marrying. We also test a further prediction from the biological markets theory, namely that where the local sex ratio produces an oversupply of men, women will be able to drive a harder bargain. As the sex ratio of the states increases, the effect of SES on marriage success becomes stronger, indicating increased competition between men and an increased ability to choose on the part of women.

  10. Male phenotypic quality influences offspring sex ratio in a polygynous ungulate

    PubMed Central

    Røed, Knut H; Holand, Øystein; Mysterud, Atle; Tverdal, Aage; Kumpula, Jouko; Nieminen, Mauri

    2006-01-01

    Evolutionary models of sex ratio adjustment applied to mammals have ignored that females may gain indirect genetic benefits from their mates. The differential allocation hypothesis (DAH) predicts that females bias the sex ratio of their offspring towards (more costly) males when breeding with an attractive male. We manipulated the number of available males during rut in a polygynous ungulate species, the reindeer (Rangifer tarandus), and found that a doubling of average male mass (and thus male attractiveness) in the breeding herd increased the proportion of male offspring from approximately 40 to 60%. Paternity analysis revealed indeed that males of high phenotypic quality sired more males, consistent with the DAH. This insight has consequences for proper management of large mammal populations. Our study suggests that harvesting, by generating a high proportion of young, small and unattractive mates, affects the secondary sex ratio due to differential allocation effects in females. Sustainable management needs to consider not only the direct demographic changes due to harvest mortality and selection, but also the components related to behavioural ecology and opportunities for female choice. PMID:17254998

  11. Parrotfish sex ratios recover rapidly in Bermuda following a fishing ban

    NASA Astrophysics Data System (ADS)

    O'Farrell, Shay; Luckhurst, Brian E.; Box, Stephen J.; Mumby, Peter J.

    2016-06-01

    Parrotfishes are an ecologically and commercially important teleost group whose grazing contributes to maintaining coral-dominated states on hermatypic reefs. However, overfishing has skewed sex ratios of Atlantic parrotfishes because fishing has disproportionate impacts on larger individuals, and males are generally larger than females. Whether protection from fishing may allow sex ratios to return to equilibrium is unknown, as fishing can induce irreversible ecological and/or evolutionary shifts. Bermuda banned trap fishing in 1990, creating a unique opportunity to analyse long-term responses of Atlantic parrotfishes to release from fishing. We found that sex ratios of four common parrotfishes were initially skewed, with male proportions ranging from 0.04 to 0.18. However, male proportions rebounded within 3-4 yr, equilibrating at values ranging from 0.36 to 0.54, similar to those reported at unfished sites in the region. Our results are encouraging for regional efforts to recover lost grazing function by restoring overfished herbivore populations.

  12. Population Sex Ratios: Another Consideration in the Reintroduction – Reinforcement Debate?

    PubMed Central

    Lambertucci, Sergio A.; Carrete, Martina; Speziale, Karina L.; Hiraldo, Fernando; Donázar, José Antonio

    2013-01-01

    Reintroduction or reinforcement (RorR) of wild populations is a common conservation strategy. Many conservation projects involve the release of individuals of poorly studied species. This may lead to inefficient results or negative impacts on the conservation efforts. Here, we provide new insights into the conservation implications and potential consequences of a skew in the sex ratio of released birds and of the number of birds supplemented for the demography of a long-lived dimorphic bird species, the Andean condor (Vulturgryphus). We demonstrate that a RorR conservation program may be less effective in conserving a species if the sex ratios of the releases and the recipient populations are not considered. We also show that releases can reduce population declines but only if carried out over long periods (i.e., several decades). This can mean high costs for release programs and the added challenge of maintaining programs over time. If RorR programs are to be implemented, bearing in mind the importance of properly assessing their effectiveness, we urge conservation researchers and managers to consider the implications of sex ratio biases for wild populations, and particularly for dimorphic species with sexually despotic behaviour. PMID:24086641

  13. Even more extreme fertility insurance and the sex ratios of protozoan blood parasites.

    PubMed

    Gardner, A; Reece, S E; West, S A

    2003-08-21

    Theory developed for malaria and other protozoan parasites predicts that the evolutionarily stable gametocyte sex ratio (z*; proportion of gametocytes that are male) should be related to the inbreeding rate (f) by the equation z*=(1-f)/2. Although this equation has been applied with some success, it has been suggested that in some cases a less female biased sex ratio can be favoured to ensure female gametes are fertilized. Such fertility insurance can arise in response to two factors: (i) low numbers of gametes produced per gametocyte and (ii) the gametes of only a limited number of gametocytes being able to interact. However, previous theoretical studies have considered the influence of these two forms of fertility insurance separately. We use a stochastic analytical model to address this problem, and examine the consequences of when these two types of fertility insurance are allowed to occur simultaneously. Our results show that interactions between the two types of fertility insurance reduce the extent of female bias predicted in the sex ratio, suggesting that fertility insurance may be more important than has previously been assumed.

  14. [Sex ratio adjustment of a non-pollinating fig wasp species on Ficus semicordata in Xishuangbanna].

    PubMed

    Song, Bo; Peng, Yan-Qiong; Guan, Jun-Ming; Yang, Pei; Yang, Da-Rong

    2008-03-01

    Through controlling the number of ovipositing foundresses inside a fig, and combining with the observation of ovipositing behavior and mating behavior, this paper studied the sex ratio of Apocryptophagus sp., a species of non-pollinating fig wasps hosted on Ficus semicordata in Xishuangbanna. The results showed that female Apocryptophagus sp. started to visit the fig on the 3rd day after pollinator Ceratosolen gravelyi oviposited. Apocryptaphagus sp. oviposited on the outside of the fig, and the ovipositing lasted for 2 days. Male Apocryptophagus sp. emerged at the same time with pollinators. The males opened a small hole on the wall of gall where the females developed, and mated with the females. Mated females emerged from their development fig, and left for a new receptive fig. The sex ratio of Apocryptaphagus sp. was in agreement with local mate competition theory, i. e., it was female-biased. Meanwhile, the total number of offspring increased with increasing foundress number. In contrast, the average number of offspring per foundress decreased. At individual level, when a female laid eggs inside a fig, the sex ratio of offspring correlated negatively with the number of offspring.

  15. Sex Ratio Meiotic Drive as a Plausible Evolutionary Mechanism for Hybrid Male Sterility

    PubMed Central

    Zhang, Linbin; Xiao, Hailian; Tao, Yun

    2015-01-01

    Biological diversity on Earth depends on the multiplication of species or speciation, which is the evolution of reproductive isolation such as hybrid sterility between two new species. An unsolved puzzle is the exact mechanism(s) that causes two genomes to diverge from their common ancestor so that some divergent genes no longer function properly in the hybrids. Here we report genetic analyses of divergent genes controlling male fertility and sex ratio in two very young fruitfly species, Drosophila albomicans and D. nasuta. A majority of the genetic divergence for both traits is mapped to the same regions by quantitative trait loci mappings. With introgressions, six major loci are found to contribute to both traits. This genetic colocalization implicates that genes for hybrid male sterility have evolved primarily for controlling sex ratio. We propose that genetic conflicts over sex ratio may operate as a perpetual dynamo for genome divergence. This particular evolutionary mechanism may largely contribute to the rapid evolution of hybrid male sterility and the disproportionate enrichment of its underlying genes on the X chromosome – two patterns widely observed across animals. PMID:25822261

  16. Age, sex and other factors in radiation carcinogenesis

    SciTech Connect

    Fry, R.J.M.; Carnes, B.A.

    1988-01-01

    It has been held for a long time that the young are more susceptible than adults to the induction of cancer by radiation. The data in support of that contention are accumulating especially from human studies. In an exposed population a significant fraction of the total population risk may be attributed to the risk associated with those who were young at the time of exposure. Since cancer may not appear for decades after exposure estimates of risk may require models for projecting the lifetime risk. Two such models, additive or absolute risk and multiplicative or relative risk have been used. The appropriateness of the latter model is supported by the finding in mice of a positive relationship between natural incidence and the susceptibility for induction by radiation of solid cancer. The choice of model for leukemias is not clear cut. The incidence of cancer increases with age, but the susceptibility for induction decreases. The incidence of cancers increases to a peak and then begins to decline at different ages, dependent on the type of cancer. Sex-dependent differences in both the natural incidence and the susceptibility for induction of cancer are not restricted to sex organs. For example, the susceptibility for the induction by radiation for myeloid leukemia is greater in males than females, whereas in the case of thymic lymphoma it is vice versa. 25 refs., 5 figs., 3 tabs.

  17. Arachidonic acid enhances reproduction in Daphnia magna and mitigates changes in sex ratios induced by pyriproxyfen.

    PubMed

    Ginjupalli, Gautam K; Gerard, Patrick D; Baldwin, William S

    2015-03-01

    Arachidonic acid is 1 of only 2 unsaturated fatty acids retained in the ovaries of crustaceans and an inhibitor of HR97g, a nuclear receptor expressed in adult ovaries. The authors hypothesized that, as a key fatty acid, arachidonic acid may be associated with reproduction and potentially environmental sex determination in Daphnia. Reproduction assays with arachidonic acid indicate that it alters female:male sex ratios by increasing female production. This reproductive effect only occurred during a restricted Pseudokirchneriella subcapitata diet. Next, the authors tested whether enriching a poorer algal diet (Chlorella vulgaris) with arachidonic acid enhances overall reproduction and sex ratios. Arachidonic acid enrichment of a C. vulgaris diet also enhances fecundity at 1.0 µM and 4.0 µM by 30% to 40% in the presence and absence of pyriproxyfen. This indicates that arachidonic acid is crucial in reproduction regardless of environmental sex determination. Furthermore, the data indicate that P. subcapitata may provide a threshold concentration of arachidonic acid needed for reproduction. Diet-switch experiments from P. subcapitata to C. vulgaris mitigate some, but not all, of arachidonic acid's effects when compared with a C. vulgaris-only diet, suggesting that some arachidonic acid provided by P. subcapitata is retained. In summary, arachidonic acid supplementation increases reproduction and represses pyriproxyfen-induced environmental sex determination in D. magna in restricted diets. A diet rich in arachidonic acid may provide protection from some reproductive toxicants such as the juvenile hormone agonist pyriproxyfen. Environ Toxicol Chem 2015;34:527-535. © 2014 SETAC.

  18. Apolipoprotein E and Alzheimer disease: genotype-specific risks by age and sex.

    PubMed Central

    Bickeböller, H; Campion, D; Brice, A; Amouyel, P; Hannequin, D; Didierjean, O; Penet, C; Martin, C; Pérez-Tur, J; Michon, A; Dubois, B; Ledoze, F; Thomas-Anterion, C; Pasquier, F; Puel, M; Demonet, J F; Moreaud, O; Babron, M C; Meulien, D; Guez, D; Chartier-Harlin, M C; Frebourg, T; Agid, Y; Martinez, M; Clerget-Darpoux, F

    1997-01-01

    The distribution of apolipoprotein E (APOE) genotypes as a function of age and sex has been examined in a French population of 417 Alzheimer disease (AD) patients and 1,030 control subjects. When compared to the APOE epsilon3 allele, an increased risk associated with the APOE epsilon4 allele (odds ratio [OR] [epsilon4] = 2.7 with 95% confidence interval [CI] = 2.0-3.6; P < .001) and a protective effect of the APOE epsilon2 allele (OR[epsilon2] = 0.5 with 95% CI = 0.3-0.98; P = .012) were retrieved. An effect of the epsilon4 allele dosage on susceptibility was confirmed (OR[epsilon4/epsilon4] vs. the epsilon3/epsilon3 genotype = 11.2 [95% CI = 4.0-31.6]; OR[epsilon3/epsilon4] vs. the epsilon3/epsilon3 genotype = 2.2 [95% CI = 1.5-3.5]). The frequency of the epsilon4 allele was lower in male cases than in female cases, but, since a similar difference was found in controls, this does not lead to a difference in OR between sex. ORs for the epsilon4 allele versus the epsilon3 allele, OR(epsilon4), were not equal in all age classes: OR(epsilon4) in the extreme groups with onset at < 60 years or > 79 years were significantly lower than those from the age groups 60-79 years. In epsilon3/epsilon4 individuals, sex-specific lifetime risk estimates by age 85 years (i.e., sex-specific penetrances by age 85 years) were 0.14 (95% CI 0.04-0.30) for men and 0.17 (95% CI 0.09-0.28) for women. PMID:9012418

  19. Apolipoprotein E and Alzheimer disease: Genotype-specific risks by age and sex

    SciTech Connect

    Bickeboeller, H. |; Babron, M.C.; Clerget-Darpoux, F.

    1997-02-01

    The distribution of apolipoprotein E (APOE) genotypes as a function of age and sex has been examined in a French population of 417 Alzheimer disease (AD) patients and 1,030 control subjects. When compared to the APOE {epsilon}3 allele, an increased risk associated with the APOE {epsilon}4 allele (odds ratio [OR] [{epsilon}4] = 2.7 with 95% confidence interval [CI] = 2.0-3.6; P < .001) and a protective effect of the APOE {epsilon}2 allele (OR[{epsilon}2] = 0.5 with 95% CI = 0.3-0.98; P = .012) were retrieved. An effect of the {epsilon}4 allele dosage on susceptibility was confirmed (OR[{epsilon}4/{epsilon}4] vs. the {epsilon}3/{epsilon}3 genotype = 11.2 [95% CI = 4.0-31.6]; OR[{epsilon}3/{epsilon}4] vs. the {epsilon}3/{epsilon}3 genotype = 2.2 [95% Cl = 1.5-3.5]). The frequency of the {epsilon}4 allele was lower in male cases than in female cases, but, since a similar difference was found in controls, this does not lead to a difference in OR between sex. ORs for the {epsilon}4 allele versus the {epsilon}3 allele, OR({epsilon}4), were not equal in all age classes: OR({epsilon}4) in the extreme groups with onset at < 60 years or > 79 years were significantly lower than those from the age groups 60-79 years. In {epsilon}3/{epsilon}4 individuals, sex-specific lifetime risk estimates by age 85 years (i.e., sex-specific penetrances by age 85 years) were 0.14 (95% CI 0.04-0.30) for men and 0.17 (95% CI 0.09-0.28) for women. 53 refs., 1 fig., 3 tabs.

  20. Sibling sex ratio and birth order in early-onset gender dysphoric adolescents.

    PubMed

    Schagen, Sebastian E E; Delemarre-van de Waal, Henriette A; Blanchard, Ray; Cohen-Kettenis, Peggy T

    2012-06-01

    Several sibship-related variables have been studied extensively in sexual orientation research, especially in men. Sibling sex ratio refers to the ratio of brothers to sisters in the aggregate sibships of a group of probands. Birth order refers to the probands' position (e.g., first-born, middle-born, last-born) within their sibships. Fraternal birth order refers to their position among male siblings only. Such research was extended in this study to a large group of early-onset gender dysphoric adolescents. The probands comprised 94 male-to-female and 95 female-to-male gender dysphoric adolescents. The overwhelming majority of these were homosexual or probably prehomosexual. The control group consisted of 875 boys and 914 girls from the TRAILS study. The sibling sex ratio of the gender dysphoric boys was very high (241 brothers per 100 sisters) compared with the expected ratio (106:100). The excess of brothers was more extreme among the probands' older siblings (300:100) than among their younger siblings (195:100). Between-groups comparisons showed that the gender dysphoric boys had significantly more older brothers, and significantly fewer older sisters and younger sisters, than did the control boys. In contrast, the only notable finding for the female groups was that the gender dysphoric girls had significantly fewer total siblings than did the control girls. The results for the male probands were consistent with prior speculations that a high fraternal birth order (i.e., an excess of older brothers) is found in all homosexual male groups, but an elevated sibling sex ratio (usually caused by an additional, smaller excess of younger brothers) is characteristic of gender dysphoric homosexual males. The mechanisms underlying these phenomena remain unknown.

  1. A comparison of methods used to obtain age ratios of snow and Canada geese

    USGS Publications Warehouse

    Higgins, K.F.; Linder, R.L.; Springer, P.F.

    1969-01-01

    The validity of group counts, cannon-net catches, and hunter-bag checks for estimating productivity of lesser snow geese (Anser caerulescens caerulescens) and small Canada geese (Branta canadensis hutchinsii-parvipes complex) was studied at Sand Lake National Wildlife Refuge during the falls of 1965 and 1966. Age ratios of snow geese obtained from net-trapped samples were significantly higher (P < 0.01) than from group counts at the same site. Immature snow geese were shot in a significantly greater (P < 0.01) proportion than they existed in the population as determined by group counts. Cannon-net catches and hunter-bag checks of snow and Canada geese yielded age ratios which were biased because of behavioral characteristics of the geese. Immatures of both species were less wary of trap equipment and immature snow geese were more vulnerable to the gun than adults. It was believed that age ratios from group counts of snow geese were more representative of the population than those from net catches and hunter-bag checks. Sex ratios of net-trapped geese showed a preponderance of males for adult Canada and adult and immature snow geese, whereas females were predominant in the immature segment of Canada geese. Hunter selectivity of blue- or white-phase snow geese was not observed at Sand Lake Refuge. Differential vulnerability to hunting between snow and Canada geese resulted from differences m feeding-flight behavior.

  2. Sex ratio and women's career choice: does a scarcity of men lead women to choose briefcase over baby?

    PubMed

    Durante, Kristina M; Griskevicius, Vladas; Simpson, Jeffry A; Cantú, Stephanie M; Tybur, Joshua M

    2012-07-01

    Although the ratio of males to females in a population is known to influence behavior in nonhuman animals, little is known about how sex ratio influences human behavior. We propose that sex ratio affects women's family planning and career choices. Using both historical data and experiments, we examined how sex ratio influences women's career aspirations. Findings showed that a scarcity of men led women to seek high-paying careers and to delay starting a family. This effect was driven by how sex ratio altered the mating market, not just the job market. Sex ratios involving a scarcity of men led women to seek lucrative careers because of the difficulty women have in finding an investing, long-term mate under such circumstances. Accordingly, this low-male sex ratio produced the strongest desire for lucrative careers in women who are least able to secure a mate. These findings demonstrate that sex ratio has far-reaching effects in humans, including whether women choose briefcase over baby.

  3. Where have all the females gone? Male biased sex-ratio in Arctodiaptomus alpinus (Imhof, 1885) in alpine lakes

    NASA Astrophysics Data System (ADS)

    Žibrat, U.; Brancelj, A.

    2009-04-01

    In populations with both males and females sex-ratio is one of the driving forces of population dynamics. It influences fecundity, inbreeding and social interactions. Sex-ratio is affected by several biotic and abiotic factors, either by selective killing of one sex or by inducing migrations. In alpine lakes of Triglav National Park, Slovenia, an extremely male biased sex-ratio in Arctodiaptomus alpinus (Imhof, 1885) was regularly observed since 1992. We analysed population dynamics and sex-ratio of A. alpinus in three alpine lakes (Jezero v Ledvicah, Rjavo jezero and Zgornje Kriško jezero) from Triglav National Park in Slovenia. In addition to seasonal dynamics we also researched long-term changes in sex-ratio (in a period of 11 years from autumn samples) as a result of increased air-temperature, and zooplankton diurnal vertical migrations. Adults of both sexes were found to appear at the same time in the water collumn with males prevailing throughout the season. A similar trend was found in copepodites CV. The percent of adult females began increasing in late summer, when there were no more copepodites and recrutation from copepodites CV to adults stopped, while male mortality increased. All cohorts of A. alpinus were found to perform diurnal vertical migrations. Both adult and CV females remained close to the bottom during the day and migrated vertically during the night. Results of the long-term study show no changes in sex-ratio in autumn.

  4. Adult sex ratio, sexual dimorphism and sexual selection in a Mesozoic reptile.

    PubMed

    Motani, Ryosuke; Jiang, Da-yong; Rieppel, Olivier; Xue, Yi-fan; Tintori, Andrea

    2015-09-22

    The evolutionary history of sexual selection in the geologic past is poorly documented based on quantification, largely because of difficulty in sexing fossil specimens. Even such essential ecological parameters as adult sex ratio (ASR) and sexual size dimorphism (SSD) are rarely quantified, despite their implications for sexual selection. To enable their estimation, we propose a method for unbiased sex identification based on sexual shape dimorphism, using size-independent principal components of phenotypic data. We applied the method to test sexual selection in Keichousaurus hui, a Middle Triassic (about 237 Ma) sauropterygian with an unusually large sample size for a fossil reptile. Keichousaurus hui exhibited SSD biased towards males, as in the majority of extant reptiles, to a minor degree (sexual dimorphism index -0.087). The ASR is about 60% females, suggesting higher mortality of males over females. Both values support sexual selection of males in this species. The method may be applied to other fossil species. We also used the Gompertz allometric equation to study the sexual shape dimorphism of K. hui and found that two sexes had largely homogeneous phenotypes at birth except in the humeral width, contrary to previous suggestions derived from the standard allometric equation.

  5. Emergence success and sex ratio of commercial alfalfa leafcutting bees from the United States and Canada.

    PubMed

    Pitts-Singer, Theresa L; James, Rosalind R

    2005-12-01

    Samples of overwintering alfalfa leafcutting bee, Megachile rotundata (F.) (Hymenoptera: Megachilidae), cells were sent to the laboratory as loose cells or in nesting boards from bee managers in the United States and in Canada. X-radiographs of cells were used for determining cell contents. Cells containing live prepupae were incubated, and the sex of emerging adults was recorded daily. Cells from which no adult emerged were dissected to determine the developmental stage of dead bees and sex of dead pupae or adults. Bee cells incubated in commercial settings and placed in alfalfa fields by the same bee managers described above also were evaluated to determine adult emergence success. The proportion of live bees in wood nesting boards from the United States was much lower than the live proportion in polystyrene nesting boards from Canada and loose cells overwintered in the United States. For laboratory-incubated loose cells, survival and sex ratios of bees from Canadian sources were statistically higher than those of U.S. bees, but the onset and duration of emergence times were similar. Fewer bees survived in the commercial setting than in the laboratory. Prepupal mortality was significantly higher than pupal or adult mortality, but there was no significant difference between the sexes in the likelihood of survival during incubation. This study supports the commonly held belief that alfalfa leafcutting bees raised in Canada and then sold to the United States represent a more viable source of bees than most bees produced in the United States.

  6. The impact of the stopping rule on sex ratio of last births in Vietnam.

    PubMed

    Pham, Bang Nguyen; Adair, Timothy; Hill, Peter S; Rao, Chalapati

    2012-03-01

    This study examines the hypothesis that the stopping rule - a traditional postnatal sex selection method where couples decide to cease childbearing once they bear a son - plays a role in high sex ratio of last births (SRLB). The study develops a theoretical framework to demonstrate the operation of the stopping rule in a context of son preference. This framework was used to demonstrate the impact of the stopping rule on the SRLB in Vietnam, using data from the Population Change Survey 2006. The SRLB of Vietnam was high at the level of 130 in the period 1970-2006, and particularly in the period 1986-1995, when sex-selective abortion was not available. Women were 21% more likely to stop childbearing after a male birth compared with a female birth. The SRLB was highest at parity 2 (138.7), particularly in rural areas (153.5), and extremely high (181.9) when the previous birth was female. Given the declining fertility, the stopping rule has a potential synergistic effect with sex-selective abortion to accentuate a trend of one-son families in the population.

  7. Sex ratio estimations of loggerhead sea turtle hatchlings by histological examination and nest temperatures at Fethiye beach, Turkey

    NASA Astrophysics Data System (ADS)

    Kaska, Yakup; Ilgaz, Çetin; Özdemir, Adem; Başkale, Eyüp; Türkozan, Oğuz; Baran, Ibrahim; Stachowitsch, Michael

    2006-07-01

    Hatchling sex ratios in the loggerhead turtle ( Caretta caretta) were estimated by placing electronic temperature recorders in 21 nests at Fethiye beach during 2000 2002. Over the seasons, the mean temperature in the middle third of the incubation period ranged from 26.7 to 32.1°C, and incubation periods ranged from 49 to 67 days. Based on the mean temperatures during the middle third of the incubation period, and on histologically sexed dead hatchlings, the sex ratios of hatchlings at Fethiye beach were roughly equal, i.e. 60 65% of the hatchlings were females. This contrasts with the highly female-skewed sex ratios in loggerhead turtles elsewhere; Fethiye has a relatively high proportion of male hatchlings. For endangered sea turtles, the knowledge of hatchling sex ratios at different beaches, coupled with appropriate conservation measures, can make an important contribution to their survival.

  8. The number of illegal migrants of Mexican origin in the United States: sex ratio-based estimates for 1980.

    PubMed

    Bean, F D; King, A G; Passel, J S

    1983-02-01

    This article reports the results of applying a sex ratio-based method to estimate the number of undocumented Mexicans residing in the United States in 1980. The approach centers on a comparison between the hypothetical sex ratio one would expect to find in Mexico in the absence of emigration to the United States and the sex ratio that is in fact reported in preliminary results from the 1980 Mexican Census. The procedure involves, inter alia, assuming a range of values for the sex ratio at birth and for census coverage differentials by sex in Mexico. Even the combinations of these values most likely to result in large estimates suggest that no more than 4 million illegal migrants of Mexican origin were residing in the United States in 1980.

  9. Sex ratio estimations of loggerhead sea turtle hatchlings by histological examination and nest temperatures at Fethiye beach, Turkey.

    PubMed

    Kaska, Yakup; Ilgaz, Cetin; Ozdemir, Adem; Başkale, Eyüp; Türkozan, Oğuz; Baran, Ibrahim; Stachowitsch, Michael

    2006-07-01

    Hatchling sex ratios in the loggerhead turtle (Caretta caretta) were estimated by placing electronic temperature recorders in 21 nests at Fethiye beach during 2000-2002. Over the seasons, the mean temperature in the middle third of the incubation period ranged from 26.7 to 32.1 degrees C, and incubation periods ranged from 49 to 67 days. Based on the mean temperatures during the middle third of the incubation period, and on histologically sexed dead hatchlings, the sex ratios of hatchlings at Fethiye beach were roughly equal, i.e. 60-65% of the hatchlings were females. This contrasts with the highly female-skewed sex ratios in loggerhead turtles elsewhere; Fethiye has a relatively high proportion of male hatchlings. For endangered sea turtles, the knowledge of hatchling sex ratios at different beaches, coupled with appropriate conservation measures, can make an important contribution to their survival.

  10. Second to fourth digit ratio (2D:4D) and concentrations of circulating sex hormones in adulthood

    PubMed Central

    2011-01-01

    Background The second to fourth digit ratio (2D:4D) is used as a marker of prenatal sex hormone exposure. The objective of this study was to examine whether circulating concentrations of sex hormones and SHBG measured in adulthood was associated with 2D:4D. Methods This analysis was based on a random sample from the Melbourne Collaborative Cohort Study. The sample consisted of of 1036 men and 620 post-menopausal women aged between 39 and 70 at the time of blood draw. Concentrations of circulating sex hormones were measured from plasma collected at baseline (1990-1994), while digit length was measured from hand photocopies taken during a recent follow-up (2003-2009). The outcome measures were circulating concentrations of testosterone, oestradiol, dehydroepiandrosterone sulphate, androstenedione, Sex Hormone Binding Globulin, androstenediol glucoronide for men only and oestrone sulphate for women only. Free testosterone and oestradiol were estimated using standard formulae derived empirically. Predicted geometric mean hormone concentrations (for tertiles of 2D:4D) and conditional correlation coefficients (for continuous 2D:4D) were obtained using mixed effects linear regression models. Results No strong associations were observed between 2D:4D measures and circulating concentrations of hormones for men or women. For males, right 2D:4D was weakly inversely associated with circulating testosterone (predicted geometric mean testosterone was 15.9 and 15.0 nmol/L for the lowest and highest tertiles of male right 2D:4D respectively (P-trend = 0.04). There was a similar weak association between male right 2D:4D and the ratio of testosterone to oestradiol. These associations were not evident in analyses of continuous 2D:4D. Conclusions There were no strong associations between any adult circulating concentration of sex hormone or SHGB and 2D:4D. These results contribute to the growing body of evidence indicating that 2D:4D is unrelated to adult sex hormone concentrations

  11. Sex pheromone component ratios and mating isolation among three Lygus plant bug species of North America

    NASA Astrophysics Data System (ADS)

    Byers, John A.; Fefer, Daniela; Levi-Zada, Anat

    2013-12-01

    The plant bugs Lygus hesperus, Lygus lineolaris, and Lygus elisus (Hemiptera: Miridae) are major pests of many agricultural crops in North America. Previous studies suggested that females release a sex pheromone attractive to males. Other studies showed that males and females contain microgram amounts of ( E)-4-oxo-2-hexenal, hexyl butyrate, and ( E)-2-hexenyl butyrate that are emitted as a defense against predators. Using gas chromatography-mass spectrometry, we found that female L. lineolaris and L. elisus have a 4:10 ratio of hexyl butyrate to ( E)-2-hexenyl butyrate that is reversed from the 10:1 ratio in female L. hesperus (males of the three species have ~10:1 ratio). These reversed ratios among females of the species suggest a behavioral role. Because both sexes have nearly equal amounts of the major volatiles, females should release more to attract males. This expectation was supported because L. hesperus females released more hexyl butyrate (mean of 86 ng/h) during the night (1800-0700 hours) than did males (<1 ng/h). We used slow-rotating pairs of traps to test the attraction of species to blends of the volatiles with a subtractive method to detect synergism. Each species' major butyrate ester was released at 3 μg/h, the minor butyrate according to its ratio, and ( E)-4-oxo-2-hexenal at 2 μg/h. The resulting catches of only Lygus males suggest that ( E)-4-oxo-2-hexenal is an essential sex pheromone component for all three species, ( E)-2-hexenyl butyrate is essential for L. elisus and L. lineolaris, and hexyl butyrate is essential for L. hesperus. However, all three components are recognized by each species since ratios of the butyrate esters are critical for conspecific attraction and heterospecific avoidance by males and thus play a role in reproductive isolation among the three species. Because L. hesperus males and females are known to emit these major volatiles for repelling ant predators, our study links defensive allomones in Lygus bugs with an

  12. Study on mating ecology and sex ratio of three internally ovipositing fig wasps of Ficus curtipes.

    PubMed

    Zhang, F P; Yang, D R

    2010-04-01

    Studies on mating ecology and sex allocation in fig-parasitizing wasps ovipositing from outside the fig have given valuable insights into known factors that are responsible for the theory of sex ratio. Similarly, internally ovipositing fig-parasitizing wasps and fig-pollinating wasps provide interesting models for comparative analysis. In addition to the fig-pollinating wasp Eupristina sp., we found that Ficus curtipes hosts two species of internally ovipositing fig-parasitizing wasps: D. yangi and Lipothymus sp. Eupristina sp. males showed less aggression. Eupristina sp. has wingless males that mate only within the natal patch, providing excellent examples of full local-mate competition. D. yangi males showed high levels of aggression and lethal combat. D. yangi has winged males but mate mostly within the natal patch. Only a few matings occur after male dispersal. Its sex ratio was lower than the prediction of partial local mate competition theory. Wingless male Lipothymus sp., which mate partly after dispersal, did not present fatal fight. Therefore, the mating behaviour of D. yangi and Lipothymus sp. did not follow predicted patterns, based on wing morph. The mating pattern of D. yangi and Lipothymus sp. should follow the partial local mate competition theory. Furthermore, there was not a significant correlation between the proportion of males and the proportion of fruit parasitized in both winged D. yangi males and wingless Lipothymus sp. males.

  13. The AKR gene family and modifying sex ratios in palms through abiotic stress responsiveness.

    PubMed

    Somyong, Suthasinee; Poopear, Supannee; Jomchai, Nukoon; Uthaipaisanwong, Pichahpuk; Ruang-Areerate, Panthita; Sangsrakru, Duangjai; Sonthirod, Chutima; Ukoskit, Kittipat; Tragoonrung, Somvong; Tangphatsornruang, Sithichoke

    2015-05-01

    Sex ratio (SR), the ratio of female inflorescences to total inflorescences, is one of the main yield components of oil palm (Elaeis guineensis Jacq). The SR quantitative trait locus (QTL) was recently identified on linkage (LG) 8 with a phenotype variance explained (PVE) of 11.3 %. The use of both genetic and physical mapping is one strategy for uncovering the genetic basis of the traits. Here, we report the construction of bacterial artificial chromosome (BAC) and fosmid libraries, and their use for physical mapping in oil palm. Combined, the libraries consist of more than 200,000 clones, representing 6.35 genome equivalents. Physical mapping at the SR locus was implemented by incorporating the published oil palm genome sequence and positive BAC/fosmid clones as identified by colony PCR screening. Based on the previously published sequences, the interval (about 184 kb) was comprised of 19 contigs of the known sequences (~117 kb, 64 %). After, combining the 454 pyrosequences of 15 positive clones and the previously published sequences, the known sequences were revealed to cover about 82 % of the interval (~150 kb), and were used for identifying the new markers by designing 35 gene-based and 23 simple sequence repeat (SSR)-amplified primers. As a result, a putative aldo-keto reductase gene (named EgAKR1) was revealed to be a promising candidate for sex ratio determination, via controlling female inflorescence number (11 % of PVE). This was predicted from the two newly identified polymorphic marker loci (mEgSSRsr8-21LB and mEgAKR1-9) designing from EgAKR1. The functions of AKR gene families in other plant species and our promoter analysis suggested that EgAKR1 may contribute to the sex ratio through abiotic stress responsiveness.

  14. Differences in Movement Pattern and Detectability between Males and Females Influence How Common Sampling Methods Estimate Sex Ratio

    PubMed Central

    Rodrigues, João Fabrício Mota; Coelho, Marco Túlio Pacheco

    2016-01-01

    Sampling the biodiversity is an essential step for conservation, and understanding the efficiency of sampling methods allows us to estimate the quality of our biodiversity data. Sex ratio is an important population characteristic, but until now, no study has evaluated how efficient are the sampling methods commonly used in biodiversity surveys in estimating the sex ratio of populations. We used a virtual ecologist approach to investigate whether active and passive capture methods are able to accurately sample a population’s sex ratio and whether differences in movement pattern and detectability between males and females produce biased estimates of sex-ratios when using these methods. Our simulation allowed the recognition of individuals, similar to mark-recapture studies. We found that differences in both movement patterns and detectability between males and females produce biased estimates of sex ratios. However, increasing the sampling effort or the number of sampling days improves the ability of passive or active capture methods to properly sample sex ratio. Thus, prior knowledge regarding movement patterns and detectability for species is important information to guide field studies aiming to understand sex ratio related patterns. PMID:27441554

  15. Mothers under stress? Hatching sex ratio in relation to maternal baseline corticosterone in the common tern (Sterna hirundo).

    PubMed

    Riechert, Juliane; Chastel, Olivier; Becker, Peter H

    2013-09-01

    Sex ratio of progeny should be balanced if costs and benefits of rearing sons and daughters are equal. However, shifts in sex ratio have been demonstrated across bird species and it was suggested that females are able to adjust the primary sex ratio. One possible mechanism is the glucocorticoid corticosterone which rises under stressful conditions and can be deposited into egg yolk by mothers. We analysed primary sex ratio of common terns Sterna hirundo from 2006 to 2008 and related it to maternal baseline corticosterone level, laying date and year. Therefore, we took 101 blood samples of 71 breeding females via blood sucking bugs, a method with negligible stress for the birds. Sex ratio did not differ from parity in any of the analysed years, which were characterized by poor food availability and breeding success. Only within 1 year there was a tendency for more females in the last hatched chick. Neither corticosterone level nor laying date or year showed an influence on hatching sex ratio. The negative result concerning primary sex ratio and maternal baseline corticosterone level might suggest conditions to be good enough for mothers to prevent them from depositing high levels of corticosterone into eggs.

  16. Identifying sex and age of apapane and iiwi on Hawaii

    USGS Publications Warehouse

    Fancy, S.G.; Pratt, T.K.; Lindsey, G.D.; Harada, C.K.; Parent, A.H.; Jacobi, J.D.

    1993-01-01

    Methods to determine the sex and age of Apapane (Himatione sanguinea) and Iiwi (Vestiaria coccinea) were developed on the basis of 189 museum specimens and 91 live birds captured in mist nets on the Island of Hawaii (USA). Both species retain all juvenal primaries and some juvenal secondaries and body feathers after the first prebasic molt and attain full adult plumage after the second prebasic molt. Apapane in their first basic plumage retain some buff-edged juvenal secondaries (particularly secondaries five and six) and sometimes retain a few gray-brown feathers on the head. The first basic plumage of Iiwi is characterized by secondaries 6-9 being longer and darker than secondaries 1-4 and the presence of a few yellowish juvenal body feathers with black spots at the tips. Adult male Apapane and Iiwi have longer wing, tail, exposed culmen, culmen and tarso-metatarsus lengths than females. Linear discriminant functions are presented to sex adult Apapane and Iiwi from lengths of their wing chord and exposed culmen.

  17. Digit ratio varies with sex, egg order and strength of mate preference in zebra finches.

    PubMed Central

    Burley, Nancy Tyler; Foster, Valerie Suzanne

    2004-01-01

    The steroid environment encountered by developing vertebrates has important organizational effects on physiology and behaviour that persist throughout an organism's lifetime. Optimal allocation of maternal steroids to zygotes may be difficult to achieve because of the sexually antagonistic effects of steroids; thus, for example, a hormone environment beneficial to a developing male may be much less beneficial to a developing female. Research into the important topic of how mothers might adaptively adjust steroid titres experienced by particular young has been constrained by the difficulty of measuring the steroid environment experienced by the embryo at critical times in development. A potential approach to this problem has been suggested by research on variation in digit ratios in humans, where the ratio of the length of the second and fourth digits reflects the steroid environment experienced by the foetus; notably, digit 4 lengthens in response to androgens. In light of the conservative nature of homeobox genes regulating early development in tetrapods, we questioned whether a sex difference in digit ratio exists in a passerine bird, the zebra finch, Taeniopygia guttata castanotis, and whether observed variation in the ratio is consistent with the previously reported pattern that androgen allocation to zebra finch egg yolk declines across laying order. We established an aviary population of outbred, wild-type zebra finches, and allowed them to breed freely. Hatchlings were marked to correspond to their egg order, and their digit ratios were measured after birds reached adulthood. We found that digit ratio increased across egg order, which is consistent with a pattern of decreasing androgen allocation. Moreover, digit ratios differed between the sexes. We also investigated whether variation in digit ratio among adult females predicted variation in their performance in mate-choice tests. Digit ratio accounted for almost 50% of the variance in strength of female

  18. Hamstrings to quadriceps peak torque ratios diverge between sexes with increasing isokinetic angular velocity.

    PubMed

    Hewett, Timothy E; Myer, Gregory D; Zazulak, Bohdanna T

    2008-09-01

    Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velocity increased. Studies that analysed the H/Q ratio with gravity corrected isokinetic strength testing reported between 1967 and 2004 were included in our review and analysis. Keywords were hamstrings/quadriceps, isokinetics, peak torque and gravity corrected. Medline and Smart databases were searched combined with cross-checked bibliographic reference lists of the publications to determine studies to be included. Twenty-two studies were included with a total of 1568 subjects (1145 male, 423 female). Males demonstrated a significant correlation between H/Q ratio and isokinetic velocity (R=0.634, p<0.0001), and a significant difference in the isokinetic H/Q ratio at the lowest angular velocity (47.8+/-2.2% at 30 degrees /s) compared to the highest velocity (81.4+/-1.1% at 360 degrees /s, p<0.001). In contrast, females did not demonstrate a significant relationship between H/Q ratio and isokinetic velocity (R=0.065, p=0.77) or a change in relative hamstrings strength as the speed increased (49.5+/-8.8% at 30 degrees /s; 51.0+/-5.7% at 360 degrees /s, p=0.84). Gender differences in isokinetic H/Q ratios were not observed at slower angular velocities. However, at high knee flexion/extension angular velocities, approaching those that occur during sports activities, significant gender differences were observed in the H/Q ratio. Females, unlike males, do not increase hamstrings to quadriceps torque ratios at velocities that approach those of functional activities.

  19. Sex ratios provide evidence for monozygotic twinning in the ring-tailed lemur, Lemur catta.

    PubMed

    St Clair, John; Campbell-Palmer, Roisin; Lathe, Richard

    2014-02-01

    Monozygotic (MZ) twinning is generally considered to be rare in species other than human. We inspected sex ratios in European zoo-bred ring-tailed lemurs (Lemur catta), revealing a significant excess of same-sex twins. Of 94 pairs, 60 (64%) were either both males or both females (p = .004). Application of the Weinberg differential rule argues that 27% of all twins in this species are MZ pairs. In this protected species, where twinning is commonplace (~50% of newborns are twins), the probable existence of frequent MZ twinning has ramifications for breeding programs aimed to maximize genetic diversity, and suggests that twin studies in a species other than human could have potential as a medical research tool.

  20. Winning the Genetic Lottery: Biasing Birth Sex Ratio Results in More Grandchildren

    PubMed Central

    Thogerson, Collette M.; Brady, Colleen M.; Howard, Richard D.; Mason, Georgia J.; Pajor, Edmond A.; Vicino, Greg A.; Garner, Joseph P.

    2013-01-01

    Population dynamics predicts that on average parents should invest equally in male and female offspring; similarly, the physiology of mammalian sex determination is supposedly stochastic, producing equal numbers of sons and daughters. However, a high quality parent can maximize fitness by biasing their birth sex ratio (SR) to the sex with the greatest potential to disproportionately outperform peers. All SR manipulation theories share a fundamental prediction: grandparents who bias birth SR should produce more grandoffspring via the favored sex. The celebrated examples of biased birth SRs in nature consistent with SR manipulation theories provide compelling circumstantial evidence. However, this prediction has never been directly tested in mammals, primarily because the complete three-generation pedigrees needed to test whether individual favored offspring produce more grandoffspring for the biasing grandparent are essentially impossible to obtain in nature. Three-generation pedigrees were constructed using 90 years of captive breeding records from 198 mammalian species. Male and female grandparents consistently biased their birth SR toward the sex that maximized second-generation success. The most strongly male-biased granddams and grandsires produced respectively 29% and 25% more grandoffspring than non-skewing conspecifics. The sons of the most male-biasing granddams were 2.7 times as fecund as those of granddams with a 50∶50 bias (similar results are seen in grandsires). Daughters of the strongest female-biasing granddams were 1.2 times as fecund as those of non-biasing females (this effect is not seen in grandsires). To our knowledge, these results are the first formal test of the hypothesis that birth SR manipulation is adaptive in mammals in terms of grandchildren produced, showing that SR manipulation can explain biased birth SR in general across mammalian species. These findings also have practical implications: parental control of birth SR has the

  1. Cancer of the colon and rectum: Potential effects of sex-age interactions on incidence and outcome

    PubMed Central

    Purim, Ofer; Gordon, Noa; Brenner, Baruch

    2013-01-01

    Background Sex differences in epidemiological, clinical and pathological characteristics of colorectal cancer have been under intensive investigation for the last three decades. Given that most of the sex-related differences reported were also age-related, this study sought to determine the potential effect of a sex-age interaction on colorectal cancer development and progression. Material/Methods Statistical data on sex- and age-specific colon or rectal cancer incidence, disease stage and survival for white persons were derived from the United States Surveillance, Epidemiology and End Results (SEER) Program. Age-specific incidence rates in 2002–2006 were analyzed by 5-year age groups (45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75–79, 80–84 years) in men and women. Sex differences were measured by calculating rate differences (RD) and rate ratios (RR). Equivalent analyses for a similar time period were performed for stage distribution and 5-year relative survival. Results Age-specific incidence rates were higher for men, for all life-time periods. However, the magnitude of the male predominance was age-dependent. The RR and RD did not remain constant over time: they increased gradually with age, peaked at 70–74 years, and declined thereafter. The distribution of stage at diagnosis was similar between men and women, but women seemed to have better survival, until the age of 64 years for colon cancer and 74 years for rectal cancer. Conclusions There seem to be significant age-related sex differences in the incidence of colorectal cancer, and maybe also in its prognosis. PMID:23511310

  2. The role of insulin in age-related sex differences of cardiovascular risk profile and morbidity.

    PubMed

    Willeit, J; Kiechl, S; Egger, G; Oberhollenzer, M; Oberhollenzer, F; Muggeo, M; Poewe, W; Bonora, E

    1997-04-01

    Metabolic changes and shifts in vascular risk profiles during and after menopause may partly explain the loss of premenopausal protection against cardiovascular disease (CVD). The current population-based survey addresses changes in risk factors and insulin levels across an age range of 40-79 years in men and women. Population recruitment was performed as part of the Bruneck Study from July to November 1990. In brief, of 1000 subjects randomly selected for inclusion 936 participated, with insulin measurements available in a random subgroup of 880 men and women, 60 of whom were excluded due to manifest diabetes mellitus. Insulin concentrations were assessed according to Hales and Randle and by a human insulin-specific radioimmunoassay. A rise in insulin concentrations with advancing age in women (5th-8th decade, 10.5-14.4 mU/l or +1.2%/year) contrasts with a marked gradual decline in insulin levels in men (5th-8th decade, 12.5-5.9 mU/l or -2.4%/year). Age trends of insulin concentrations in sexes emerged as independent of age-related changes in body weight, type of fat distribution, alcohol consumption, cigarette smoking, social status, fasting glucose, and physical activity (P < 0.001 for sex-specific difference in the regression slopes). Insulin levels in pre- and postmenopausal women of equal age differed significantly (10.1 vs. 13.9 mU/l, P = 0.003), thus advocating that variations of insulin observed may in part be related to shifts in sex hormone status. Levels of virtually all vascular risk attributes were lower in premenopausal women than in men of equal age, but the opposite was true for the elderly. The switch in the sex preponderance of vascular risk factors may be crucially involved in closing the CVD incidence gap between genders after menopause. The analysis suggests that variations in insulin levels are a common metabolic basis for sex/age trends in fasting glucose, apolipoprotein B, total cholesterol, total cholesterol/HDL cholesterol ratio, LDL

  3. Does the timing of attainment of maturity influence sexual size dimorphism and adult sex ratio in turtles?

    USGS Publications Warehouse

    Lovich, Jeffrey E.; Gibbons, J. Whitfield; Agha, Mickey

    2014-01-01

    The attainment of sexual maturity has been shown to affect measures of sexual size dimorphism (SSD) and adult sex ratios in several groups of vertebrates. Using data for turtles, we tested the model that sex ratios are expected to be male-biased when females are larger than males and female-biased when males are larger than females because of the relationship of each with the attainment of maturity. Our model is based on the premise that the earlier-maturing sex remains smaller, on average throughout life, and predominates numerically unless the sexes are strongly affected by differential mortality, differential emigration, and immigration, or biased primary sex ratios. Based on data for 24 species in seven families, SSD and sex ratios were significantly negatively correlated for most analyses, even after the effect of phylogenetic bias was removed. The analyses provide support for the model that SSD and adult sex ratios are correlated in turtles as a result of simultaneous correlation of each with sexual differences in attainment of maturity (bimaturism). Environmental sex determination provides a possible mechanism for the phenomenon in turtles and some other organisms.

  4. Sex, age, and sex hormones affect recall of words in a directed forgetting paradigm.

    PubMed

    Kerschbaum, Hubert H; Hofbauer, Ildiko; Gföllner, Anna; Ebner, Birgit; Bresgen, Nikolaus; Bäuml, Karl-Heinz T

    2017-01-02

    During the course of serious discussion, an unexpected interruption may induce forgetting of the original topic of a conversation. Sex, age, and sex hormone levels may affect frequency and extension of forgetting. In a list-method directed forgetting paradigm, subjects have to learn two word lists. After learning list 1, subjects receive either a forget or a remember list 1 cue. When the participants had learned list 2 and completed a distraction task, they were asked to write down as many recalled items as possible, starting either with list 1 or list 2 items. In the present study, 96 naturally cycling women, 60 oral contraceptive users, 56 postmenopausal women, and 41 young men were assigned to one of these different experimental conditions. Forget-cued young subjects recall fewer list 1 items (list 1 forgetting) but more list 2 items (list 2 enhancement) compared with remember-cued subjects. However, forget-cued postmenopausal women showed reduced list 1 forgetting but enhanced list 2 retention. Remember-cued naturally cycling women recalled more list 1 items than oral contraceptive users, young men, and postmenopausal women. In forget-cued follicular women, salivary progesterone correlated positively with recalled list 2 items. Salivary 17β-estradiol did not correlate with recalled list 1 or list 2 items in either remember- or forget-cued young women. However, salivary 17β-estradiol correlated with item recall in remember-cued postmenopausal women. Our findings suggest that sex hormones do not globally modulate verbal memory or forgetting, but selectively affect cue-specific processing. © 2016 Wiley Periodicals, Inc.

  5. [Iris heterochromia: variations in form, age changes, sex dimorphism].

    PubMed

    Stelzer, O

    1979-06-01

    On a sample of n = 25,346 individuals from Vienna (10,855 males, 14,491 females) the iris pigmentation has been typed by the author. In this sample 65 cases of different types of heterochromia were found. The frequency of the occurrence of the different types of this anomaly could be calculated for the first time. Neglecting age, sex, and type of heterochromia the total frequency amounts to 0.256 (males: 0.157; females: 0.37) %. The variants of heterochromia very from cases of total heterochromia to those of various size; in addition to it a number of special types could be observed. The localization of the heterochrome parts of the iris shows certain variations; mostly, however, it is seen in the lower half of the iris. The nasal part is concerned in only one case; the temporal region never. Thus, the partial heterochromia is characteristic by a marked dependency of its localization. The colour of heterochromia varies from 2 a-14 according to the Martin-Schultz standard set of coloured eyes. However, No. 9 (ca. 50%) and No. 7 (ca. 20%) were the most frequent colours. The age variations are considerable. 5/6 of all heterochromias were found between the age from 2-19 years. Finally, a marked sexual dimorphism was observed, as in females heterochromia is much more frequent than in males.

  6. Age, sex, and nitrazepam kinetics: relation to antipyrine disposition.

    PubMed

    Greenblatt, D J; Abernethy, D R; Locniskar, A; Ochs, H R; Harmatz, J S; Shader, R I

    1985-12-01

    Forty healthy men and women 19 to 80 years old received a single 10 mg oral dose of the 7-nitro benzodiazepine nitrazepam. Nitrazepam plasma concentrations were measured during the next 72 hours. Among men, the elderly had a larger volume of distribution (Varea) than did younger subjects (1.96 vs. 1.63 L/kg; P less than 0.05); because clearance did not change with age (0.84 vs. 0.95 ml/min/kg), the prolonged t1/2 in elderly men (28 vs. 20 hours; P less than 0.01) was a result of the larger Varea. Elderly and young women did not differ in nitrazepam Varea (2.58 vs. 2.55 L/kg), t1/2 (26 vs. 27 hours), or total clearance (1.19 vs. 1.09 ml/min/kg). The nitrazepam free fraction in plasma (18% to 19% unbound) was not related to age or sex. Among 18 subjects who also received antipyrine, the clearance of nitrazepam and antipyrine were not correlated (r = 0.23). Thus age minimally influences nitrazepam clearance (accomplished mainly by nitroreduction), which in turn is not significantly related to antipyrine oxidizing capacity.

  7. Age, sex and personality in early cannabis use.

    PubMed

    Muro I Rodríguez, A

    2015-06-01

    Previous studies analysing personality and cannabis use in adult samples suggest that cannabis users show significant higher levels of impulsivity, sensation seeking and schizotypy. However, there are few studies exploring this relationship in adolescence using psychobiological models of personality. Given the relevance of identifying individual differences that lead adolescents to early cannabis use to prevent future health problems, the present study aimed to explore the relationship between age, sex, personality and early cannabis use using a psychobiological model of personality in a sample of 415 students (51.8% boys) from 12 to 18 years. Chi(2) tests showed significant higher prevalence of cannabis use in boys and in the group aged 15-18 years. Multiple analysis of variance showed significant higher scores in psychoticism, sensation seeking and in all its subscales in cannabis users group, while an interaction with age was found for extraversion and neuroticism: cannabis users scored higher than non-users in the youngest group (12-14 years) but lower in the oldest group in both dimensions. Finally, regression analysis showed that narrower traits of sensation seeking (experience seeking and disinhibition) were the most associated to early cannabis use. Results are discussed in terms of early cannabis users' personality profiles and in terms of the self-medication theory.

  8. Oviposition and Sex Ratio of the Redbanded Stink Bug, Piezodorous guildinii, in Soybean

    PubMed Central

    Temple, Joshua H.; Davis, Jeffrey A.; Hardke, Jarrod T.; Price, Paul P.; Leonard, B. Rogers

    2016-01-01

    Redbanded stink bug, Piezodorus guildinii (Westwood), is a significant soybean pest across the mid-south region of the United States. The objectives of these studies were to characterize: (1) redbanded stink bug oviposition in relationship to soybean maturity group (MG), plant structure, crop phenology, and vertical distribution within the plant canopy; and (2) redbanded stink bug adult sex ratios in relationship to soybean phenology. A total of 5645 redbanded stink bug eggs in 421 egg masses (clusters) were field collected from naturally-occurring populations in MG IV and V soybean over a three year period (2009 to 2011). The mean number of eggs within a cluster was 16.6 ± 0.3. Plant structures by MG interactions were highly significant with more egg masses oviposited on leaves in MG IV (79.4%) and more on pods in MG V (72.7%). The ratio of females to males was similar in all soybean growth stages except R5, where the sex ratio increased to 1.4:1, coinciding with peak oviposition. Only 29.9% of egg clusters in MG IV and 18.3% of egg clusters in MG V were oviposited in the upper 35 cm of the soybean canopy. Based on these results, sampling strategies and insecticide application placement for stink bugs may require modification. PMID:27322333

  9. Economics, cultural transmission, and the dynamics of the sex ratio at birth in China

    PubMed Central

    Lipatov, Mikhail; Li, Shuzhuo; Feldman, Marcus W.

    2008-01-01

    In rural China, the ratio of newborn boys to newborn girls [sex ratio at birth (SRB)] has been rising for several decades, to values significantly above its biological norm. This trend has a number of alarming societal consequences, and has attracted the attention of scholars and politicians. The root of the problem lies in a 2,500-year-old culture of son preference. This culture is intricately linked with the economic reality of each couple's life, so that there are financial and psychological repercussions to parents who have no sons. To bring greater clarity and understanding to this issue, we present a quantitative framework that describes the interaction between economics and cultural transmission. We start with an explicit mechanism by which economic incentives can change cultural beliefs of a given individual, and go on to include a mechanism of cultural inheritance from generation to generation. We then show how economic conditions can affect the dynamics of cultural change in an entire society, and may lead to a decrease in the country's sex ratio at birth. PMID:19047641

  10. Adjustment of offspring sex ratios in relation to the availability of resources for philopatric offspring in the common brushtail possum.

    PubMed Central

    Johnson, C. N.; Clinchy, M.; Taylor, A. C.; Krebs, C. J.; Jarman, P. J.; Payne, A.; Ritchie, E. G.

    2001-01-01

    The local-resource-competition hypothesis predicts that where philopatric offspring compete for resources with their mothers, offspring sex ratios will be biased in favour of the dispersing sex. This should produce variation in sex ratios between populations in relation to differences in the availability of resources for philopatric offspring. However, previous tests of local resource competition in mammals have used indirect measures of resource availability and have focused on sex-ratio variation between species or individuals rather than between local populations. Here, we show that the availability of den sites predicts the offspring sex ratio in populations of the common brushtail possum. Female possums defend access to dens, and daughters, but not sons, occupy dens within their mother's range. However, the abundances of possums in our study areas were determined principally by food availability. Consequently, in food-rich areas with a high population density, the per-capita availability of dens was low, and the cost of having a daughter should have been high. This cost was positively correlated with male bias in the sex ratio at birth. Low per capita availability of dens was correlated with male bias in the sex ratio at birth. PMID:11571046

  11. Female-biased sex ratio, polygyny, and persistence in the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus)

    USGS Publications Warehouse

    Kus, Barbara E.; Howell, Scarlett; Wood, Dustin A.

    2017-01-01

    Demographic changes in populations, such as skewed sex ratios, are of concern to conservationists, especially in small populations in which stochastic and other events can produce declines leading to extirpation. We documented a decline in one of the few remaining populations of Southwestern Willow Flycatcher (Empidonax traillii extimus) in southern California, USA, which dropped from 40 to 5 adults between 2000 and 2015. Declines were unequal between sexes (94% for males, 82% for females). Adult sex ratios were female-biased in 10 of 16 yr. The proportion of paired males that were polygynous ranged from 0% to 100%, depending on the ratio of females to males in the adult population. Some males paired with up to 5 females simultaneously. We investigated the role of nestling sex ratio in the female-biased adult sex ratio by using genetic techniques to determine sex from blood samples collected from 162 nestlings in 72 nests from 2002 to 2009. Both population-level and within-brood nestling sex ratios were female-biased, and were not influenced by nest order (first or subsequent), parental mating type (monogamous or polygynous), or year. Disproportionately more females than males were recruited into the breeding population, mirroring nestling and fledgling sex ratios. It thus appears that a skewed nestling sex ratio has contributed to a female-biased adult population, which in turn has influenced mating behavior. We propose that the capacity for polygyny, which generally occurs at low levels in Southwestern Willow Flycatchers, has allowed this population to persist through a decline that might otherwise have resulted in extinction.

  12. Effect of corticosterone and hen body mass on primary sex ratio in laying hen (Gallus gallus), using unincubated eggs.

    PubMed

    Aslam, Muhammad Aamir; Groothuis, Ton G G; Smits, Mari A; Woelders, Henri

    2014-04-01

    In various studies, chronic elevation of corticosterone levels in female birds under natural or experimental conditions resulted in female biased offspring sex ratios. In chicken, one study with injected corticosterone resulted in a male sex ratio bias. In the current study, we chronically elevated blood plasma corticosterone levels through corticosterone feeding (20 mg/kg feed) for 14 days using 30 chicken hens in each of treatment and control groups and studied the primary offspring sex ratio (here defined as the proportion of male fertile eggs determined in freshly laid eggs, i.e., without egg incubation). Mean plasma corticosterone concentrations were significantly higher in the treatment group but were not associated with sex ratio, laying rate, and fertility rate. Corticosterone treatment by itself did not affect egg sex but affected sex ratio as well as laying rate and fertility rate in interaction with hen body mass. Body mass had a negative association with sex ratio, laying rate, and fertility rate per hen in the corticosterone group, but a positive association with sex ratio in untreated hens. These interactions were already seen when taking the body mass at the beginning of the experiment, indicating intrinsic differences between light and heavy hens with regard to their reaction to corticosterone treatment. The effects on laying rate, fertility rate, and sex ratio suggest that some factor related to body mass act together with corticosterone to modulate ovarian functions. We propose that corticosterone treatment in conjunction with hen body mass can interfere with meiosis, which can lead to meiotic drive and to chromosomal aberrations resulting in postponed ovulation or infertile ova.

  13. Evolution of social parasitism in ants: size of sexuals, sex ratio and mechanisms of caste determination

    PubMed Central

    Aron, S.; Passera, L.; Keller, L.

    1999-01-01

    Social parasitism, one of the most intriguing phenomena in ants, has evolved to various levels, the most extreme form being parasites that have lost the worker caste and rely completely on the host's worker force to raise their brood. A remarkable feature of workerless social parasites is the small size of sexuals. It has been suggested that reduced size evolved as a means to take advantage of the host's caste-determination system, so that parasite larvae develop into sexuals with less food than is required to produce host workers. An important consequence of size reduction is that it might restrict the host workers' ability to discriminate between the brood of the social parasite and their own brood and might protect parasite sexuals from elimination. We found that sexuals of the workerless inquiline ant Plagiolepis xene were significantly smaller than the sexuals of their host Plagiolepis pygmaea, but remarkably similar to the host workers. The size variance of parasite sexuals was much lower than that of their host; this result possibly suggests that there is very stabilizing selection acting on size of the parasite sexuals. Comparison of the primary (egg) and secondary (adult) sex ratios of the parasite and host showed that miniaturization of P. xene sexuals has been accompanied by their ability to develop into sexuals even when the host P. pygmaea actively prevents production of its own sexuals. These results suggest that the inquiline's size and caste threshold have been reduced such that all individuals in a parasite brood will develop into sexuals. We also found that the adult sex ratio of P. xene was heavily female-biased. This bias probably stems from local mate competition that arises from sexuals mating within the nest. There was no significant difference between the proportion of haploid eggs and adult males produced; this observation indicates that a female-biased sex ratio is achieved by queens producing a higher proportion of diploid eggs rather

  14. Behavior problems of clinic children: relation to parental marital status, age and sex of child.

    PubMed

    Brady, C P; Bray, J H; Zeeb, L

    1986-07-01

    Behavior problems of 703 children seen in a clinical setting were examined for interactions between and effects of family type (i.e., parental marital status) and age and sex of child. Significant differences were found based on family type, with children of separated, divorced, and remarried parents having more problems. Expected interactions between marital status and age and sex of child were not obtained, although results support prior research with regard to the effects of age and sex.

  15. Sex-Based Differences in Asthma among Preschool and School-Aged Children in Korea.

    PubMed

    Jang, Yeonsoo; Shin, Anna

    2015-01-01

    The purpose of this study was to explore risk factors related to asthma prevalence among preschool and school-aged children using a representative national dataset from the Korea National Health and Nutrition Examination Survey (KNHANES) conducted from 2009-2011. We evaluated the demographic information, health status, household environment, socioeconomic status, and parents' health status of 3,542 children aged 4-12 years. A sex-stratified multivariate logistic regression was used to obtain adjusted prevalence odds ratios (ORs) and 95% confidence intervals after accounting for primary sample units, stratification, and sample weights. The sex-specific asthma prevalence in the 4- to 12-year-old children was 7.39% in boys and 6.27% in girls. Boys and girls with comorbid atopic dermatitis were more likely to have asthma than those without atopic dermatitis (boys: OR = 2.20, p = 0.0071; girls: OR = 2.33, p = 0.0031). Boys and girls with ≥1 asthmatic parent were more likely to have asthma than those without asthmatic parents (boys: OR = 3.90, p = 0.0006; girls: OR = 3.65, p = 0.0138). As girls got older, the prevalence of asthma decreased (OR = 0.90, p = 0.0408). Girls residing in rural areas were 60% less likely to have asthma than those residing in urban areas (p = 0.0309). Boys with ≥5 family members were more likely to have asthma than those with ≤3 family members (OR = 2.45, p = 0.0323). The factors related to asthma prevalence may differ depending on sex in preschool and school-aged children. By understanding the characteristics of sex-based differences in asthma, individualized asthma management plans may be established clinically.

  16. Change of patellar height with age and sex.

    PubMed

    Kar, Maitreyee Nandi; Bhakta, Abhijit; Mondal, Gopal Chandra; Bandyopadhyay, Maitreyi; Kar, Chinmaya; Nandi, Sujit Narayan

    2012-12-01

    Patellar height is one of the important parameter in patellar stability. Growth spurt or excessive physical strain can lead to high-riding patella or patella alta. But this is not yet proved. This study was mainly targeted at eliciting the influence of age on Insall-Salvati index, one of the important index to measure patellar height. As the present study is meant for measuring the patellar height separately in male and female, it is also to find out the effect of gender on patellar height if any. The study was been conducted in North Bengal Medical College and Hospital among 93 subjects covering both adult and adolescent age groups. Patellar height of respective subjects was measured radiologically using Insall-Salvati Index; results were extrapolated for statistical analysis. It revealed that value of Insall-Salvati index was higher in adult compared to adolescent group but the difference was not statistically significant. Statistical tests shows no significant difference in Insall-Salvati index according to sex. While screening the athletes patella alta must be kept in mind as this can be associated with patellofemoral pain syndrome, chondromalacia patellae, knees with apophysitis of tibial tubercle (Osgood-Schiatter disease). Not only that, significant cause of recurrent patellar dislocation can be associated with patella alta

  17. Age and sex determination of the Maui Parrotbill

    USGS Publications Warehouse

    Berlin, Kim E.; Simon, John C.; Pratt, Thane K.; Baker, Paul E.; Kowalsky, James R.

    2001-01-01

    We determined the best plumage and morphometric variables for ageing and sexing the Maui Parrotbill (Pseudonestor xanthophrys), an endangered Hawaiian honeycreeper found only on east Maui, Hawaii, by examining and measuring 30 museum specimens and 71 live birds captured in mist nets. Juvenal plumage was identified by the presence of pale-tipped wing bars on the middle and greater coverts, grayish olive dorsal plumage, and dingy white underparts and superciliaries. Birds undergoing first prebasic molt retained the juvenal remiges, rectrices, and wing coverts. Birds in first basic plumage possessed juvenal wing bars and a dull juvenal-like plumage. Subsequent molts were complete, and adults lacked wing bars. Adult males had bright yellow plumage on the cheeks, throat, and superciliaries, as did 27% of adult females. All other adult females had less yellow in the underparts. The dorsal plumage of adult females was more variable than adult males and was either yellow-olive like the males or grayish olive. Adult males had longer wing, bill, tail, and tarsometatarsus and greater mass than adult females. Virtually all males and females could be distinguished by wing length. Morphometrics of immature birds were significantly smaller than for adult males. Only immature male wing chord was significantly larger than that of adult females. Although it was difficult to distinguish between immatures and some adult females based on plumage coloration or measurements, a cut-off point of 70.4 mm for wing chord separated 91% of females from 93% of males, regardless of age.

  18. Sex-of-offspring-specific transmission ratio distortion on mouse chromosome X.

    PubMed Central

    de la Casa-Esperon, E; Pardo-Manuel de Villena, F; Verner, A E; Briscoe, T L; Malette, J M; Rosa, M; Jin, W H; Sapienza, C

    2000-01-01

    During our study of the DDK syndrome, we observed sex ratio distortion in favor of males among the offspring of F(1) backcrosses between the C57BL/6 and DDK strains. We also observed significant and reproducible transmission ratio distortion in favor of the inheritance of DDK alleles at loci on chromosome X among female offspring but not among male offspring in (C57BL/6 x DDK)F(1) x C57BL/6 and (C57BL/6-Pgk1(a) x DDK)F(1) x C57BL/6 backcrosses. The observed transmission ratio distortion is maximum at DXMit210 in the central region of chromosome X and decreases progressively at proximal and distal loci, in a manner consistent with the predictions of a single distorted locus model. DXMit210 is closely linked to two distortion-controlling loci (Dcsx1 and Dcsx2) described previously in interspecific backcrosses. Our analysis suggests that the female-offspring-specific transmission ratio distortion we observe is likely to be the result of the death of embryos of particular genotypic combinations. In addition, we confirm the previous suggestion that the transmission ratio distortion observed on chromosome X in interspecific backcrosses is also the result of loss of embryos. PMID:10628993

  19. Declined sex ratio at birth in Fallujah (Iraq) during Iraq war with Iran.

    PubMed

    Saadat, Mostafa

    2011-01-01

    The main objective of this study was to investigate whether the sex ratio at birth (SRB, male proportion) alter in Iraq during its war against Iran (1980-1988). Here we compared 785 births (348 males, 437 females) during 1980-1989 with 1144 births (655 males, 489 females) before 1980 and 2914 births (1496 males, 1418 females) after 1989 in Fallujah, Iraq. The SRB significantly decreased during 1980-1989 in comparison with the ratios before 1980 (OR=0.595, 95 % CI: 0.495-0.714, P<0.001) and after 1989 (OR=0.755, 95 % CI: 0.644-0.884, P=0.001). Considering that the Iran-Iraq war began at 1980 and ended in 1988, therefore it seems that the SRB decreased in Fallujah (Iraq) during the war.

  20. Sex ratio determination in bovine semen: a new approach by quantitative real time PCR.

    PubMed

    Parati, K; Bongioni, G; Aleandri, R; Galli, A

    2006-12-01

    Sex preselection of livestock offspring in cattle represents, nowadays, a big potential for genetic improvement and market demand satisfaction. Sperm sorting by flow cytometer provides a powerful tool for artificial insemination and production of predefined sexed embryos but, an accurate verification of the yield of sperm separation remains essential for a field application of this technique or for improvement and validation of other related semen sexing technologies. In this work a new method for the determination of the proportion of X- and Y-bearing spermatozoa in bovine semen sample was developed by real time PCR. Two sets of primers and internal TaqMan probes were designed on specific X- and Y-chromosome genes. To allow a direct quantification, a standard reference was established using two plasmid cDNA clones (ratio 1:1) for the specific gene targets. The method was validated by a series of accuracy, repeatability and reproducibility assays and by testing two sets of sorted and unsorted semen samples. A high degree of accuracy (98.9%), repeatability (CV=2.58%) and reproducibility (CV=2.57%) was shown. The results of X- and Y-sorted semen samples analysed by real time PCR and by flow cytometric reanalysis showed no significant difference (P>0.05). The evaluation of X-chromosome bearing sperms content in unsorted samples showed an average of 51.11+/-0.56% for ejaculates and 50.17+/-0.58% for the commercial semen. This new method for quantification of the sexual chromosome content in spermatozoa demonstrated to be rapid and reliable, providing a valid support to the sperm sexing technologies.

  1. Effects of age, sex and smoking on ankle-brachial index in a Finnish population at risk for cardiovascular disease

    PubMed Central

    Syvänen, Kari; Aarnio, Pertti; Jaatinen, Pekka; Korhonen, Päivi

    2007-01-01

    BACKGROUND Smoking is a well-known risk factor for peripheral arterial disease (PAD). Data regarding differences in the prevalence of PAD between sexes are somewhat controversial. In addition, most studies indicate that the prevalence of PAD increases with age in both sexes. In the present study, the effects of sex, age and smoking on the ankle-brachial index (ABI) in a Finnish cardiovascular risk population were investigated. OBJECTIVES To investigate the relationship between the ankle-brachial index, and age, sex and smoking in a Finnish population at risk for cardiovascular disease. METHODS All men and women between 45 and 70 years of age living in a rural town (Harjavalta, Finland; total population 7700) were invited to participate in a population survey (Harmonica study). Patients with previously diagnosed diabetes or vascular disease were excluded. In total, 2856 patients were invited to participate in the study. From these subjects, a cardiovascular risk population was screened. Complete data were available from 1028 persons. ABI (the ratio between the posterior tibial or dorsalis pedis artery and brachial artery pressures) was measured, and questionnaires were used to detect smoking status and relevant medical history. Only current smoking status was taken into account. RESULTS The mean ABI for the entire study population was 1.10 (range 0.56 to 1.64). Current smokers had a lower mean ABI (1.06; P<0.001). There was no statistically significant difference in ABI values among age groups, although the majority of patients with ABI values below 0.9 were older than 60 years of age. There was no statistically significant difference in ABI between sexes. CONCLUSION As previously reported, the present study shows the significant effect of smoking in the development of PAD. No statistically significant difference was found among age groups, but the tendency was toward lower ABIs in the oldest age groups. Sex had a minimal effect on the ABI. PMID:22477327

  2. Local mate competition and transmission bottlenecks: a new model for understanding malaria parasite and other sex ratios.

    PubMed

    Neal, Allison T; Taylor, Peter D

    2014-12-21

    The local mate competition model from sex ratio theory predicts female-biased sex ratios in populations that are highly subdivided during mating, and is thought to accord well with the population structure of malaria parasites. However, the selective advantage of female-biased sex ratios comes from the resulting increase in total reproductive output, an advantage the transmission biology of malaria parasite likely reduces. We develop a mathematical model to determine how bottlenecks in transmission that cause diminishing fitness returns from female production affect sex ratio evolution. We develop four variations of this model that incorporate whether or not parasite clones have the ability to detect others that occupy the same host and whether or not the number of clones affects the total mating population size. Our model indicates that transmission bottlenecks favor less female-biased sex ratios than those predicted under LMC. This effect is particularly pronounced if clones have no information about the presence of coexisting clones and the number of mating individuals per patch is fixed. The model could extend our understanding of malaria parasite sex ratios in three main ways. First, it identifies inconsistencies between the theoretical predictions and the data presented in a previous study, and proposes revised predictions that are more consistent with underlying biology of the parasite. Second, it may account for the positive association between parasite density and sex ratio observed within and between some species. Third, it predicts a relationship between mortality rates in the vector and sex ratios, which appears to be supported by the little existing data we have. While the inspiration for this model came from malaria parasites, it should apply to any system in which per capita dispersal success diminishes with increasing numbers of females in a patch.

  3. A novel negative-stranded RNA virus mediates sex ratio in its parasitoid host

    PubMed Central

    Wang, Beibei; Yan, Zhichao; Hong, Jian; Werren, John H.; Song, Qisheng

    2017-01-01

    Parasitoid wasps are important natural enemies of arthropod hosts in natural and agricultural ecosystems and are often associated with viruses or virion-like particles. Here, we report a novel negative-stranded RNA virus from a parasitoid wasp (Pteromalus puparum). The complete viral genome is 12,230 nucleotides in length, containing five non-overlapping, linearly arranged open reading frames. Phylogenetically, the virus clusters with and is a novel member of the mononegaviral family Nyamiviridae, here designated as Pteromalus puparum negative-strand RNA virus 1 (PpNSRV-1). PpNSRV-1 is present in various tissues and life stages of the parasitoid wasp, and is transmitted vertically through infected females and males. Virus infections in field populations of P. puparum wasps ranged from 16.7 to 37.5%, without linearly correlating with temperature. PpNSRV-1 increased adult longevity and impaired several fitness parameters of the wasp, but had no influence on successful parasitism. Strikingly, PpNSRV-1 mediated the offspring sex ratio by decreasing female offspring numbers. RNA interference knockdown of virus open reading frame I eliminated these PpNSRV-1-induced effects. Thus, we infer that PpNSRV-1 has complex effects on its insect host including sex ratio distortion towards males, as well as possible mutualistic benefits through increasing wasp longevity. PMID:28278298

  4. SEX RATIO AT BIRTH AND THE IDEAL FAMILY IN CHI LINH DISTRICT, VIETNAM

    PubMed Central

    Thuy Duong, Doan Thi

    2016-01-01

    Chi Linh district, which locates in the Red Delta River region, has been recognized as the “hot pot” of high sex ratio at birth in Vietnam. This paper used community-based periodic Demographic-Epidemiologic Surveillance System (CHILILAB) to describe sex ratio at birth (SRB) and identify social - economic factors that related to the SRB. A total 5,940 births born from August 1, 2004 to August 31, 2011 was included in analysis. The SRB of 116.6 boys/100 girls (CI: 110.7 – 122.5) was significantly higher than normal. SRB were found high among second child having only older sister(s), among third child and higher birth order, among mothers who were 35 years and older, running small business or homemakers. Interestingly, a SRB of 91.4 boys/100 girls (CI: 81.8 – 102) was found among second children having an older brother, this is significantly lower than the normal level. Further research should be done to assert if abortion is practiced both to have a son and to have a daughter. PMID:27499813

  5. A novel negative-stranded RNA virus mediates sex ratio in its parasitoid host.

    PubMed

    Wang, Fei; Fang, Qi; Wang, Beibei; Yan, Zhichao; Hong, Jian; Bao, Yiming; Kuhn, Jens H; Werren, John H; Song, Qisheng; Ye, Gongyin

    2017-03-01

    Parasitoid wasps are important natural enemies of arthropod hosts in natural and agricultural ecosystems and are often associated with viruses or virion-like particles. Here, we report a novel negative-stranded RNA virus from a parasitoid wasp (Pteromalus puparum). The complete viral genome is 12,230 nucleotides in length, containing five non-overlapping, linearly arranged open reading frames. Phylogenetically, the virus clusters with and is a novel member of the mononegaviral family Nyamiviridae, here designated as Pteromalus puparum negative-strand RNA virus 1 (PpNSRV-1). PpNSRV-1 is present in various tissues and life stages of the parasitoid wasp, and is transmitted vertically through infected females and males. Virus infections in field populations of P. puparum wasps ranged from 16.7 to 37.5%, without linearly correlating with temperature. PpNSRV-1 increased adult longevity and impaired several fitness parameters of the wasp, but had no influence on successful parasitism. Strikingly, PpNSRV-1 mediated the offspring sex ratio by decreasing female offspring numbers. RNA interference knockdown of virus open reading frame I eliminated these PpNSRV-1-induced effects. Thus, we infer that PpNSRV-1 has complex effects on its insect host including sex ratio distortion towards males, as well as possible mutualistic benefits through increasing wasp longevity.

  6. The mechanism of sex ratio adjustment in a pollinating fig wasp.

    PubMed

    Raja, Shazia; Suleman, Nazia; Compton, Stephen G; Moore, Jamie C

    2008-07-22

    Sex ratio strategies in species subject to local mate competition (LMC), and in particular their fit to quantitative theoretical predictions, provide insight into constraints upon adaptation. Pollinating fig wasps are widely used in such studies because their ecology resembles theory assumptions, but the cues used by foundresses to assess potential LMC have not previously been determined. We show that Liporrhopalum tentacularis females (foundresses) use their clutch size as a cue. First, we make use of species ecology (foundresses lay multiple clutches, with second clutches smaller than first) to show that increases in sex ratio in multi-foundress figs occur only when foundresses are oviposition site limited, i.e. that there is no direct response to foundress density. Second, we introduce a novel technique to quantify foundress oviposition sequences and show, consistent with the theoretical predictions concerning clutch size-only strategies, that they produce mainly male offspring at the start of bouts, followed by mostly females interspersed by a few males. We then discuss the implications of our findings for our understanding of the limits of the ability of natural selection to produce 'perfect' organisms, and for our understanding of when different cue use patterns evolve.

  7. The mechanism of sex ratio adjustment in a pollinating fig wasp

    PubMed Central

    Raja, Shazia; Suleman, Nazia; Compton, Stephen G; Moore, Jamie C

    2008-01-01

    Sex ratio strategies in species subject to local mate competition (LMC), and in particular their fit to quantitative theoretical predictions, provide insight into constraints upon adaptation. Pollinating fig wasps are widely used in such studies because their ecology resembles theory assumptions, but the cues used by foundresses to assess potential LMC have not previously been determined. We show that Liporrhopalum tentacularis females (foundresses) use their clutch size as a cue. First, we make use of species ecology (foundresses lay multiple clutches, with second clutches smaller than first) to show that increases in sex ratio in multi-foundress figs occur only when foundresses are oviposition site limited, i.e. that there is no direct response to foundress density. Second, we introduce a novel technique to quantify foundress oviposition sequences and show, consistent with the theoretical predictions concerning clutch size-only strategies, that they produce mainly male offspring at the start of bouts, followed by mostly females interspersed by a few males. We then discuss the implications of our findings for our understanding of the limits of the ability of natural selection to produce ‘perfect’ organisms, and for our understanding of when different cue use patterns evolve. PMID:18430647

  8. SEX RATIO AT BIRTH AND THE IDEAL FAMILY IN CHI LINH DISTRICT, VIETNAM.

    PubMed

    Thuy Duong, Doan Thi

    2015-12-01

    Chi Linh district, which locates in the Red Delta River region, has been recognized as the "hot pot" of high sex ratio at birth in Vietnam. This paper used community-based periodic Demographic-Epidemiologic Surveillance System (CHILILAB) to describe sex ratio at birth (SRB) and identify social - economic factors that related to the SRB. A total 5,940 births born from August 1, 2004 to August 31, 2011 was included in analysis. The SRB of 116.6 boys/100 girls (CI: 110.7 - 122.5) was significantly higher than normal. SRB were found high among second child having only older sister(s), among third child and higher birth order, among mothers who were 35 years and older, running small business or homemakers. Interestingly, a SRB of 91.4 boys/100 girls (CI: 81.8 - 102) was found among second children having an older brother, this is significantly lower than the normal level. Further research should be done to assert if abortion is practiced both to have a son and to have a daughter.

  9. Mitochondrial DNA polymorphism, sex ratio distorters and population genetics in the isopod Armadillidium vulgare.

    PubMed Central

    Rigaud, T; Bouchon, D; Souty-Grosset, C; Raimond, R

    1999-01-01

    Two maternally inherited sex ratio distorters (SRD) impose female-biased sex ratios on the wood louse Armadillidium vulgare by feminizing putative males. These SRD are (i) an intracytoplasmic bacterium of the genus Wolbachia, and (ii) another non-Mendelian element of unknown nature: the f element. Mitochondrial DNA variation was investigated in A. vulgare field populations to trace the evolution of host-SRD relationships and to investigate the effect of SRD on host cytoplasmic polymorphism. The Wolbachia endosymbionts showed no polymorphism in their ITS2 sequence and were associated with two closely related mitochondrial types. This situation probably reflects a single infection event followed by a slight differentiation of mitochondria. There was no association between the f element and a given mitochondrial type, which may confirm the fact that this element can be partially paternally transmitted. The spreading of a maternally inherited SRD in a population should reduce the mitochondrial diversity by a hitchhiking process. In A. vulgare, however, a within-population mtDNA polymorphism was often found, because of the deficient spread of Wolbachia and the partial paternal inheritance of the f element. The analysis of molecular variance indicated that A. vulgare populations are genetically structured, but without isolation by distance. PMID:10430591

  10. A framework for analyzing sex-selective abortion: the example of changing sex ratios in Southern Caucasus

    PubMed Central

    Hohmann, Sophie A; Lefèvre, Cécile A; Garenne, Michel L

    2014-01-01

    The paper proposes a socioeconomic framework of supply, demand, and regulation to explain the development of sex-selective abortion in several parts of the world. The framework is then applied to three countries of southern Caucasus (Armenia, Azerbaijan, and Georgia) where sex-selective abortion has developed since the collapse of the Soviet Union. The authors argue that sex-selective abortion cannot be explained simply by patriarchal social systems, sex discrimination, or son preference. The emphasis is put on the long-term acceptability of abortion in the region, on acceptability of sex-screening by both the medical establishment and by the population, on newly imported techniques of sex-screening, and on the changing demand for children associated with the major economic and social changes that followed the dismantlement of the Soviet Union. PMID:25349481

  11. Male-biased sex ratios of fish embryos near a pulp mill: temporary recovery after a short-term shutdown.

    PubMed Central

    Larsson, D G Joakim; Förlin, Lars

    2002-01-01

    In a previous study we showed that broods from the viviparous eelpout Zoarces viviparus were significantly male biased in 1998 in the vicinity of a large kraft pulp mill on the Swedish Baltic coast. One suggested hypothesis was that masculinizing compounds in the effluent were affecting gonadal differentiation of the embryos, resulting in skewed sex ratios. In this article, we present further evidence for a causal relationship between the exposure to the effluent and the male-biased sex ratios. Analyses of historical samples showed that the eelpout produced male-biased broods close to the mill in 1997 in addition to 1998. During 1999, the mill was shut down for 17 days, coinciding with the period when the gonads of the eelpout embryos differentiate. Subsequently, in the fall of 1999, the sex ratios were no longer male biased; however, the following year (2000), a significant male bias reappeared. Investigations at 13 sites for up to 4 years showed a relatively stable sex ratio around 50/50, with the exceptions by the mill and with few observations of deviating ratios at other sites. Several reports document endocrine disturbances in fish near pulp and paper mills, including the expression of male secondary sex characters in female fish. The repeatedly identified male bias at the investigated mill, the normalization after mill shutdown, and the reappearance the following year indicate that pulp mill effluents also can affect sex ratios of nearby fish. PMID:12153752

  12. Sex and age as determinants of rat T-cell phenotypic characteristics: influence of peripubertal gonadectomy.

    PubMed

    Arsenović-Ranin, Nevena; Kosec, Duško; Pilipović, Ivan; Nacka-Aleksić, Mirjana; Bufan, Biljana; Stojić-Vukanić, Zorica; Leposavić, Gordana

    2017-03-09

    The study examined the influence of age, sex and peripubertal gonadectomy on a set of T-cell phenotypic parameters. Rats of both sexes were gonadectomised at the age of 1 month and peripheral blood and spleen T lymphocytes from non-gonadectomised and gonadectomised 3- and 11-month-old rats were examined for the expression of differentiation/activation (CD90/CD45RC) and immunoregulatory markers. Peripheral blood T lymphocytes from non-gonadectomised rats showed age-dependent sexual dimorphisms in (1) total count (lower in female than male 11-month-old rats); (2) CD4+:CD8 + cell ratio (higher in female than male rats of both ages); (3) the proportion of recent thymic emigrants in CD8 + T cells (lower in female than male 3-month-old rats) and (4) the proportions of mature naïve and memory/activated cells (irrespective of age, the proportion of naïve cells was higher, whereas that of memory/activated cells was lower in females). Gonadectomy influenced magnitudes or direction of these sex differences. Additionally, sex differences in peripheral blood T-lymphocyte parameters did not fully correspond to those observed in T-splenocyte parameters, suggesting the compartment-specific regulation of the major T-cell subpopulations' and their subsets' composition. Furthermore, there was no sexual dimorphism in the proportion of either CD25 + Foxp3 + cells among CD4 + or CD161+ (NKT) cells within CD8 + T lymphocytes. However, there was gonadal hormone-independent age-associated sexual dimorphism in the proportion of CD161 + cells (NKT cells) in CD8 + T splenocytes. Overall, the study revealed age-dependent variations in sexual dimorphisms in T-cell parameters relevant for immune response efficacy and showed that they are T-cell compartment-specific and partly gonadal hormone-related.

  13. Sex and Age Aspects in Patients Suffering From Out-Of-Hospital Cardiac Arrest

    PubMed Central

    Piegeler, Tobias; Thoeni, Nils; Kaserer, Alexander; Brueesch, Martin; Sulser, Simon; Mueller, Stefan M.; Seifert, Burkhardt; Spahn, Donat R.; Ruetzler, Kurt

    2016-01-01

    Abstract Cardiopulmonary resuscitation (CPR) is indicated in patients suffering from out-of-hospital cardiac arrest. Several studies suggest a sex- and age-based bias in the treatment of these patients. This particular bias may have a significant impact on the patient's outcome. However, the reasons for these findings are still unclear and discussed controversially. Therefore, the aim of this study was to retrospectively analyze treatment and out-of-hospital survival rates for potential sex- and age-based differences in patients requiring out-of-hospital CPR provided by an emergency physician in the city of Zurich, Switzerland. A total of 3961 consecutive patients (2003–2009) were included in this retrospective analysis to determine the frequency of out-of-hospital CPR and prehospital survival rate, and to identify potential sex- and age-based differences regarding survival and treatment of the patients. Seven hundred fifty-seven patients required CPR during the study period. Seventeen patients had to be excluded because of incomplete or inconclusive documentation, resulting in 743 patients (511 males, 229 females) undergoing further statistical analysis. Female patients were significantly older, compared with male patients (68 ± 18 [mean ± SD] vs 64 ± 18 years, P = .012). Men were resuscitated slightly more often than women (86.4% vs 82.1%). Overall out-of-hospital mortality rate was found to be 81.2% (492/632 patients) with no differences between sexes (82.1% for males vs 79% for females, odds ratio 1.039, 95% confidence interval 0.961–1.123). No sex differences were detected in out-of-hospital treatment, as assessed by the different medications administered, initial prehospital Glasgow Coma Scale, and prehospital suspected leading diagnosis. The data of our study demonstrate that there was no sex-based bias in treating patients requiring CPR in the prehospital setting in our physician-led emergency ambulance service. PMID:27149475

  14. Sex difference in strength and size ratios between reciprocal muscle groups in the lower leg.

    PubMed

    Akagi, R; Tohdoh, Y; Takahashi, H

    2013-05-01

    This study compared strength and size of reciprocal muscle groups in the lower leg between sexes. 20 young men and 14 young women volunteered as subjects. Joint torques developed during isometric maximal voluntary plantar flexion (TQPF) and dorsiflexion (TQDF) were measured using a dynamometer. Muscle volumes of plantar flexors (MVPF) and dorsiflexors (MVDF) were determined by magnetic resonance imaging. In each of the muscle groups, joint torque was significantly correlated with muscle volume in young men and women (r=0.610-0.848) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength ratio on muscle size ratio between the plantar flexors and dorsiflexors were investigated using joint torque and muscle volume. The correlations between the MVPF per MVDF and the TQPF per TQDF were significant both in young men (r=0.608) and women (r=0.773), suggesting that strength ratio is strongly affected by size ratio between the plantar flexors and dorsiflexors in young men and women.

  15. Sex ratio of the offspring of Sprague-Dawley rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in utero and lactationally in a three-generation study

    SciTech Connect

    Rowlands, J.C.; Budinsky, R.A. . E-mail: RABudinsky@dow.com; Aylward, L.L.; Faqi, A.S.; Carney, E.W.

    2006-10-01

    Reports of a decreased male/female sex ratio in children born to males exposed to TCDD in Seveso, Italy, at a young age have sparked examinations of this endpoint in other populations exposed to TCDD or related compounds. Overall, the male/female sex ratio results reported in these studies, with slightly different age-exposed male populations, have shown mixed results. Experimental studies of the effects of in utero exposure to TCDD in laboratory animals have reported no effect on the f{sub 1} sex ratio and mixed results for the sex ratio of the f{sub 2} generation. In order to better understand the potential effects of TCDD on second generation sex ratio, we retrieved archived data from a comprehensive three-generation feeding study of TCDD in rats that was conducted and published in the 1970s, but which did not publish data on sex ratio of the offspring [Murray, F.J., Smith, F.A., Nitschke, K.D., Humiston, C.G., Kociba, R.J., Schwetz, B.A., 1979. Three-generation reproduction study of rats given 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the diet. Toxicol. Appl. Pharmacol. 50, 241-252]. A re-examination of the original Murray et al. data found no statistically significant treatment-related changes in postnatal day 1 sex ratio in any generation of treated animals, consistent with one other relatively large study reporting on this endpoint. We discuss mechanistic data underlying a potential effect of TCDD on this endpoint. We conclude that the inconsistency in findings on sex ratio of the offspring of male rats exposed to TCDD in utero is likely due to random variation associated with a relatively small sample size, although differences between studies in strain of rat, dose regimen, and day of ascertainment of sex ratio cannot be ruled out.

  16. Age and sex differences in object control skills by children ages 5 to 14.

    PubMed

    Butterfield, Stephen A; Angell, Rose M; Mason, Craig A

    2012-02-01

    Object control skills provide children the tools to be physically active-a major societal priority. At the fundamental movement level, object control skills form the foundation of further sports skill development. The purpose of this study was to examine children's (ages 5 to 14 years, Grades K-8) development of four key object control skills: catching, throwing, kicking, and striking. 186 children were tested on selected items from the Object Control Subtest of the Test of Gross Motor Development-2, using a cross-sectional and correlational design. As anticipated, significant differences were found for age on all four skills. These improvements were characterized by early, rapid gains at ages 9 to 10, beyond which development occurred at a slower rate for catching, throwing, and kicking; striking development continued at a steady rate to age 14 years. Contrary to previous findings, no overall sex differences were found for catching or kicking. Overall sex differences favoring boys were observed for throwing and striking. Implications for evolutionary contributions to throwing and striking were discussed.

  17. Cerebral cortex: an MRI-based study of volume and variance with age and sex.

    PubMed

    Carne, Ross P; Vogrin, Simon; Litewka, Lucas; Cook, Mark J

    2006-01-01

    The aim of the present study was to examine quantitative differences in lobar cerebral cortical volumes in a healthy adult population. Quantitative volumetric MRI of whole brain, cerebral and cerebellar volumes was performed in a cross-sectional analysis of 97 normal volunteers, with segmented frontal, temporal, parietal and occipital cortical volumes measured in a subgroup of 60 subjects, 30 male and 30 female, matched for age and sex. The right cerebral hemisphere was larger than the left across the study group with a small (<1%) but significant difference in symmetry (P<0.001). No difference was found between volumes of right and left cerebellar hemispheres. Rightward cerebral cortical asymmetry (right larger than left) was found to be significant across all lobes except parietal. Males had greater cerebral, cerebellar and cerebral cortical lobar volumes than females. Larger male cerebral cortical volumes were seen in all lobes except for left parietal. Females had greater left parietal to left cerebral hemisphere and smaller left temporal to left cerebral hemisphere ratios. There was a mild reduction in cerebral volumes with age, more marked in males. This study confirms and augments past work indicating underlying structural asymmetries in the human brain, and provides further evidence that brain structures in humans are differentially sensitive to the effects of both age and sex.

  18. Total body nitrogen in health and disease: effects of age, weight, height, and sex

    SciTech Connect

    Ellis, K.J.; Yasumura, S.; Vartsky, D.; Vaswani, A.N.; Cohn, S.H.

    1982-06-01

    Total body levels of nitrogen were measured by prompt-gamma neutron activation analysis in 136 healthy adults in the general population (age 20 to 80 years), in 55 cancer patients, and in 20 obese subjects. In order to evaluate the TBN values for the patients, it was necessary to normalize the data for possible differences due to body habitus. This normalization was defined as the ratio of the measured nitrogen level to a predicted nitrogen level derived from the normal population. The parameters of sex, age, height, weight, and fat were used to calculate expected normal values of nitrogen. For the cancer patients, an average TBN deficit of less than 10% was observed. Individual patients, however, showed deviations from the TBN/sub p/ value as large as 28%. For obese patients, the TBN values were normal to slightly high. When adjusted for body size, the deficit of TBN in the cancer patients was approximately half that observd for TBK.

  19. Sex-ratio meiotic drive in Drosophila simulans is related to equational nondisjunction of the Y chromosome.

    PubMed Central

    Cazemajor, M; Joly, D; Montchamp-Moreau, C

    2000-01-01

    The sex-ratio trait, an example of naturally occurring X-linked meiotic drive, has been reported in a dozen Drosophila species. Males carrying a sex-ratio X chromosome produce an excess of female offspring caused by a deficiency of Y-bearing sperm. In Drosophila simulans, such males produce approximately 70-90% female offspring, and 15-30% of the male offspring are sterile. Here, we investigate the cytological basis of the drive in this species. We show that the sex-ratio trait is associated with nondisjunction of Y chromatids in meiosis II. Fluorescence in situ hybridization (FISH) using sex-chromosome-specific probes provides direct evidence that the drive is caused by the failure of the resulting spermatids to develop into functional sperm. XYY progeny were not observed, indicating that few or no YY spermatids escape failure. The recovery of XO males among the progeny of sex-ratio males shows that some nullo-XY spermatids become functional sperm and likely explains the male sterility. A review of the cytological data in other species shows that aberrant behavior of the Y chromosome may be a common basis of sex-ratio meiotic drive in Drosophila and the signal that triggers differential spermiogenesis failure. PMID:10628983

  20. Exposure to persistent organic pollutants and sperm sex chromosome ratio in men from the Faroe Islands

    PubMed Central

    Kvist, L.; Giwercman, A.; Weihe, P.; Jensen, T. Kold; Grandjean, P.; Halling, J.; Petersen, M. Skaalum; Giwercman, Y. Lundberg

    2015-01-01

    People in the Arctic as well as fishermen on the polluted Swedish east coast are highly exposed to persistent organic pollutants (POPs). These compounds have been shown to affect the sperm Y:X chromosome ratio. In present study, the aim was to investigate whether polychlorinated biphenyl (PCB) congeners and 1,1,-dichloro-2,2,-bis(p-chlorophenyl)ethane (p,p′-DDE) influence sperm sex chromosome ratio in Faroese men, and whether these men differ regarding Y:X ratio compared to Greenland Inuit and Swedish fishermen. The study population (n = 449) consisted of young men from the general population (n = 276) as well as proven fertile men (n = 173). The Y:X ratio was assessed by fluorescent in situ hybridization. Serum concentrations of POPs were measured using gas chromatography. Associations between POP concentrations and Y:X ratio were calculated using linear and non-linear regression models as well as trend analysis and pairwise comparison of exposure data categorized into quartiles. The selected POPs were associated with Y:X ratio in fertile Faroese men, but not in the total population; p,p′-DDE (95% CI for B = −0.005 to −0.001, p = 0.005) and ΣPCB (95% CI for B = −0.005 to −0.001, p = 0.012). Since p, p′-DDE and ΣPCB correlated significantly (r = 0.927, p < 0.001), the results involving the exposure variables can be regarded as a single finding. The Y:X ratio for the total Faroese population was 0.500 ± 0.018, which was statistically significantly lower than in both Inuit and Swedish fishermen (0.512 for both). In conclusion, Faroese men presented with lower Y:X ratio than Greenland Inuit and Swedish fishermen. Although no direct health effects are expected due to the lower Faroese Y:X ratio, it could be indicative of adverse effects on the reproductive system. PMID:25222300

  1. Aging and memory: corrections for age, sex and education for three widely used memory tests.

    PubMed

    Zappalà, G; Measso, G; Cavarzeran, F; Grigoletto, F; Lebowitz, B; Pirozzolo, F; Amaducci, L; Massari, D; Crook, T

    1995-04-01

    The associate learning subtest from the Wechsler Memory Scale; Benton's Visual Retention test and a Controlled Word Association Task (FAS) were administered to a random sample of normal, healthy individuals whose age ranged from 20 to 79 years, recruited within the Italian peninsula. The neuropsychological examination took place on a mobile unit and the tests were given by the same team of neuropsychologists to reduce variability among examiners. The Research Project was known as Progetto Memoria. Corrections to the scores of these tests were calculated for age, sex, and education. These corrected values will allow clinicians to screen for memory impairment with greater precision among normally aging individuals, thus improving differential diagnosis between physiologic and pathologic deterioration of cognitive functions.

  2. Surprising Lack of Sex Differences in Normal Cognitive Aging in Twins

    ERIC Educational Resources Information Center

    Finkel, Deborah; Reynolds, Chandra A.; Berg, Stig; Pedersen, Nancy L.

    2006-01-01

    Sex differences in the etiology of normal cognitive functioning in aging remain largely unexplored. We conducted an investigation of genetic and environmental contributions to sex differences in level of cognitive performance and rate of decline in the Swedish Adoption/Twin Study of Aging (SATSA) (Finkel & Pedersen, 2004) data set. Behavioral…

  3. Methods of Suicide by Age: Sex and Race Differences among the Young and Old.

    ERIC Educational Resources Information Center

    McIntosh, John L.; Santos, John F.

    1986-01-01

    Annual official statistics for specific methods of suicide (firearms, hanging, poisons) by age for different sex and racial groups (Whites, Blacks, non-Whites excluding Black) were examined from 1960 to 1978. Comparisons among the age-sex-race groups, along with trends over time and differences in the methods employed, were noted. (Author/ABL)

  4. Evaluation of Age, Sex, and Race Bias in the Personality Inventory for Children (PIC).

    ERIC Educational Resources Information Center

    Kline, Rex B.; Lachar, David

    1992-01-01

    Whether the external validity of the Personality Inventory for Children (PIC) was moderated by age, sex, or race was studied using 1,333 children and adolescents referred for mental health services. Race and sex generally did not moderate the relation of PIC scales to symptom checklists. Some relationships were age modified. (SLD)

  5. Association between obesity and femoral neck strength according to age, sex, and fat distribution.

    PubMed

    Kim, H; Lee, S H; Kim, B J; Koh, J M

    2017-03-29

    Indicators of total and abdominal obesity were negatively associated with femoral neck strength indices. There are age-, sex-, and fat distribution-specific differences in the magnitude of these associations. These suggested that indicators of obesity with different magnitude according to age, sex, and fat distribution associated with poor bone health.

  6. Age of Sexual Debut and Physical Dating Violence Victimization: Sex Differences among US High School Students

    ERIC Educational Resources Information Center

    Ihongbe, Timothy O.; Cha, Susan; Masho, Saba W.

    2017-01-01

    Background: Research has shown that early age of sexual debut is associated with physical dating violence (PDV), but sex-specific associations are sparse. We estimated the prevalence of PDV victimization in high school students who have initiated sexual intercourse and examined sex-specific association between age of sexual debut and PDV…

  7. Evidence for sex differences in cardiovascular aging and adaptive responses to physical activity.

    PubMed

    Parker, Beth A; Kalasky, Martha J; Proctor, David N

    2010-09-01

    There are considerable data addressing sex-related differences in cardiovascular system aging and disease risk/progression. Sex differences in cardiovascular aging are evident during resting conditions, exercise, and other acute physiological challenges (e.g., orthostasis). In conjunction with these sex-related differences-or perhaps even as an underlying cause-the impact of cardiorespiratory fitness and/or physical activity on the aging cardiovascular system also appears to be sex-specific. Potential mechanisms contributing to sex-related differences in cardiovascular aging and adaptability include changes in sex hormones with age as well as sex differences in baseline fitness and the dose of activity needed to elicit cardiovascular adaptations. The purpose of the present paper is thus to review the primary research regarding sex-specific plasticity of the cardiovascular system to fitness and physical activity in older adults. Specifically, the paper will (1) briefly review known sex differences in cardiovascular aging, (2) detail emerging evidence regarding observed cardiovascular outcomes in investigations of exercise and physical activity in older men versus women, (3) explore mechanisms underlying the differing adaptations to exercise and habitual activity in men versus women, and (4) discuss implications of these findings with respect to chronic disease risk and exercise prescription.

  8. Evidence for sex ratio distortion by a new microsporidian parasite of a Corophiid amphipod.

    PubMed

    Mautner, S I; Cook, K A; Forbes, M R; McCurdy, D G; Dunn, A M

    2007-10-01

    In this paper, we describe the occurrence of a microsporidian parasite in female-biased populations of an intertidal amphipod, Corophium volutator (Pallas), at mudflat sites in the Bay of Fundy, Canada. Sequence data for the parasite's 16S rDNA indicate that it is a novel microsporidian species. This parasite was found principally in female host gonads, indicating that it might be a vertically transmitted, sex-distorting microparasite. At 4 sites each sampled in early and mid-summer, parasite prevalence varied from 0 to 21%. In the lab, infected mothers gave rise to more female-biased broods, than did uninfected mothers. Infection was not associated with size of females or with lowered survivorship of their young. Surprisingly, infected mothers actually had higher fertility controlling for body length than did uninfected mothers. Taken together, our results suggest that this novel microsporidian is likely a feminizing microparasite and is a contributing factor to local and widespread sex ratio distortion in C. volutator.

  9. Epigenetic regulation of sex ratios may explain natural variation in self-fertilization rates

    PubMed Central

    Ellison, Amy; Rodríguez López, Carlos Marcelino; Moran, Paloma; Breen, James; Swain, Martin; Megias, Manuel; Hegarty, Matthew; Wilkinson, Mike; Pawluk, Rebecca; Consuegra, Sofia

    2015-01-01

    Self-fertilization (selfing) favours reproductive success when mate availability is low, but renders populations more vulnerable to environmental change by reducing genetic variability. A mixed-breeding strategy (alternating selfing and outcrossing) may allow species to balance these needs, but requires a system for regulating sexual identity. We explored the role of DNA methylation as a regulatory system for sex-ratio modulation in the mixed-mating fish Kryptolebias marmoratus. We found a significant interaction between sexual identity (male or hermaphrodite), temperature and methylation patterns when two selfing lines were exposed to different temperatures during development. We also identified several genes differentially methylated in males and hermaphrodites that represent candidates for the temperature-mediated sex regulation in K. marmoratus. We conclude that an epigenetic mechanism regulated by temperature modulates sexual identity in this selfing species, providing a potentially widespread mechanism by which environmental change may influence selfing rates. We also suggest that K. marmoratus, with naturally inbred populations, represents a good vertebrate model for epigenetic studies. PMID:26559950

  10. In Search of Emerging Same-Sex Sexuality: Romantic Attractions at Age 13 Years.

    PubMed

    Li, Gu; Hines, Melissa

    2016-10-01

    Sex-typed behavior in childhood is significantly related to sexual orientation in adulthood. In addition, same-sex attractions in early adolescence are more non-exclusive than in adulthood and can differ from later same-sex orientations. However, little research has focused on romantic attractions as they emerge during early adolescence. Drawing a sample from the Avon Longitudinal Study of Parents and Children (197 girls, 204 boys), the current study examined whether same-sex romantic attractions at age 13 years were exclusive, and whether they were predicted by sex-typed behavior at age 3.5 years. No young adolescents in this sample reported exclusive same-sex attractions, and increased same-sex attractions were not significantly related to reduced other-sex sexualities. Childhood sex-typed behavior did not significantly predict early same-sex attractions, suggesting that early same-sex attractions differ from later same-sex orientations. The current study highlights the importance of studying the development of sexuality beginning prior to adulthood.

  11. Breeding periodicity and sex ratios in epifaunal marine amphipoda in Lough Hyne, Ireland

    NASA Astrophysics Data System (ADS)

    Costello, Mark J.; Myers, Alan A.

    1989-11-01

    Thirteen species of amphipod were recorded from sponges and associated biota, notably algae and tunicates, in Lough Hyne (Ine), south-west Ireland. The sex ratio rarely approached unity in any species. No male Corophium bonnellii were collected. Mature male Lysianassa ceratina were not collected between late July and early September. Ovigerous females occurred throughout the year in five species. Lysianassa ceratina had the most restricted breeding period (May to September). Breeding activity, based on this criterion of reproduction, was generally greatest between April and July, but this period was extended in some species. A secondary autumn peak in breeding activity was recorded in four species. A comparison between the data from the present study and those from a similar study in Scotland suggests that in the case of two of the species, Corophium bonnellii and Lembos websteri, egg production throughout the year may be related to differing summer maximum temperatures.

  12. Carl Düsing (1884) on the regulation of the sex-ratio.

    PubMed

    Edwards, A W

    2000-11-01

    In three publications in 1883 and 1884 Carl Düsing of Jena gave a mathematical account of the influence of natural selection on the sex ratio based on the same argument that Darwin had advanced in The Descent of Man (1871). The argument thus became quite well known, being included in the principal books on the subject around the turn of the century, as well as in the Encyclopaedia Britannica, references to Düsing being given. By 1930, when Fisher gave a verbal account of the argument in The Genetical Theory of Natural Selection, he saw no need to give references, and no other book of the period treated the subject, as a result of which Düsing's contribution became lost to view. We here give the important paragraphs of Düsing's mathematical account, translated into English.

  13. Education and gender bias in the sex ratio at birth: evidence from India.

    PubMed

    Echávarri, Rebeca A; Ezcurra, Roberto

    2010-02-01

    This article investigates the possible existence of a nonlinear link between female disadvantage in natality and education. To this end, we devise a theoretical model based on the key role of social interaction in explaining people's acquisition of preferences, which justifies the existence of a nonmonotonic relationship between female disadvantage in natality and education. The empirical validity of the proposed model is examined for the case of India, using district-level data. In this context, our econometric analysis pays particular attention to the role of spatial dependence to avoid any potential problems of misspecification. The results confirm that the relationship between the sex ratio at birth and education in India follows an inverted U-shape. This finding is robust to the inclusion of additional explanatory variables in the analysis, and to the choice of the spatial weight matrix used to quantify the spatial interdependence between the sample districts.

  14. Digit ratio (2D:4D), sex differences, allometry, and finger length of 12-30-year olds: evidence from the British Broadcasting Corporation (BBC) Internet study.

    PubMed

    Manning, John T

    2010-01-01

    Many studies have reported digit ratio (2D:4D) to be sexually dimorphic, (males lower 2D:4D than females). However, Kratochvíl and Flegr ([2009]: Biol Lett 5:643-646) have suggested that 2D regressed on 4D has an allometric regression line with nonzero Y-intercept that is shared by males and females. Thus, 2D is shorter than expected when 4D is long, and males have lower 2D:4D than females because they have longer fingers. In this study, it is shown that this suggestion may be incorrect because sex differences in slope were not considered. Participants were recruited in an Internet study and had an age range of 12-30 years. The expected sex difference in 2D:4D was found, and the regression of 2D on 4D showed a significant sex difference in slope (males lower than females). A comparison of 10 age groups (12 years, 13 years..., 21-30 years) showed that sexual dimorphism for fingers was age dependent, varying from monomorphic to very dimorphic. Changes in sexual dimorphism of 2D:4D were much less marked, but there was a significant reduction in mean 2D:4D with age. The tendency for slopes of 2D regressed on 4D to be lower in males compared with females was significant in eight age groups. Sex difference in 2D:4D varied across the age groups and was positively related to the magnitude of the difference in female and male slopes. In contrast to the report of Kratochvíl and Flegr, it was found that the regression of 2D on 4D showed sex differences in slope, and such differences gave rise to the sexual dimorphism in 2D:4D.

  15. The impact of psychiatric illness on suicide: differences by diagnosis of disorders and by sex and age of subjects.

    PubMed

    Qin, Ping

    2011-11-01

    People with a psychiatric illness are at high risk for suicide; however, variation of the risk by patients' sex and age and by specific diagnosis needs to be explored in a more detail. This large population study systematically assesses suicide incidence rate ratio (IRR) and population attributable risk (PAR) associated with various psychiatric disorders by comparing 21,169 suicides in Denmark over a 17-year period with sex-age-time-matched population controls. The study shows that suicide risk is significantly increased for persons with a hospitalized psychiatric disorder and the associated risk varies significantly by diagnosis and by sex and age of subjects. Further adjustment for personal socioeconomic differences eliminates the IRRs associated with various disorders only to a limited extend. Recurrent depression and borderline personality disorder increase suicide risk the strongest while dementia increases the risk the least for both males and females. The influence of various disorders generally weakens with increasing age; however, there are important exceptions. Schizophrenia affects people aged ≤35 years the strongest in terms of both IRR and PAR. Recurrent depression increases suicide risk particularly strong in all age groups and the associated PAR increases steadily with age. Borderline personality disorder has a strong effect in young people, especially those ≤35 years. Alcohol use disorder accounts the highest PAR of suicides in males of 36-60 years old. For the elderly above 60 years old, reaction to stress and adjustment disorder increases the risk for suicide the most in both sexes. These findings suggest that approaches to psychiatric suicide prevention should be varied according to diagnosis and sex and age of subjects.

  16. The contrasting effects of ad libitum and restricted feeding of a diet very high in saturated fats on sex ratio and metabolic hormones in mice.

    PubMed

    Alexenko, Andrei P; Mao, Jiude; Ellersieck, Mark R; Davis, Angela M; Whyte, Jeffrey J; Rosenfeld, Cheryl S; Roberts, R Michael

    2007-10-01

    Skewing of the sex ratio towards males occurs among pups born to mice fed a very high saturated fat (VHF) diet. In the present study, we tested whether the fat content of the VHF diet rather than the number of calories consumed is responsible for this effect. Eight-week-old NIH Swiss mice were placed on the VHF diet either ad libitum (VHF) or in a restricted manner (VHF-R). The VHF-R mice gained weight at a similar rate to controls fed a standard chow diet. Mice were bred at 15 wk and subsequently at 26 wk and 35 wk of age. Overall, the VHF, VHF-R, and control groups delivered 244, 242, and 274 pups, respectively, with male proportions of 0.60, 0.43, and 0.48, respectively. The pup sex ratios of the VHF group (favoring males) and VHF-R group (favoring females) each differed from 0.5 (P < 0.01). The sex ratios also differed (P < 0.0001) between the VHF and control groups, and between the VHF and VHF-R groups. Within the diet groups, maternal body weight had no effect on sex ratio. Serum leptin concentrations among the dams were similar in the VHF and VHF-R groups but higher than in the control group, while the IGF1 and corticosterone levels were comparable in all three groups. Therefore, the atypical sex ratios of offspring born to dams on the VHF diet seem to be influenced by the amount of fat consumed. Since males fed the VHF diet had neither more Y-sperm nor sired more sons than daughters, the dietary effects are manifested exclusively through the female.

  17. Couples' urinary bisphenol A and phthalate metabolite concentrations and the secondary sex ratio.

    PubMed

    Bae, Jisuk; Kim, Sungduk; Kannan, Kurunthachalam; Buck Louis, Germaine M

    2015-02-01

    With limited research focusing on non-persistent chemicals as exogenous factors affecting human sex selection, this study aimed to evaluate the association of urinary bisphenol A (BPA) and phthalate metabolite concentrations with the secondary sex ratio (SSR), defined as the ratio of male to female live births. The current analysis is limited to singleton live births (n=220, 43.9%) from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study, in which couples discontinuing contraception with the intention of becoming pregnant were enrolled and followed while trying for pregnancy and through delivery for those achieving pregnancy. Using modified Poisson regression models accounting for potential confounders, we estimated the relative risks (RRs) of a male birth per standard deviation change in the log-transformed maternal, paternal, and couple urinary BPA and 14 phthalate metabolite concentrations (ng/mL) measured upon enrollment. When maternal and paternal chemical concentrations were modeled jointly, paternal BPA (RR, 0.77; 95% confidence interval [CI], 0.62-0.95) and mono-isobutyl phthalate (RR, 0.82; 95% CI, 0.67-1.00) were significantly associated with a female excess. Contrarily, maternal BPA (RR, 1.16; 95% CI, 1.03-1.31), mono-isobutyl phthalate (RR, 1.28; 95% CI, 1.06-1.54), mono-benzyl phthalate (RR, 1.31; 95% CI, 1.08-1.58), and mono-n-butyl phthalate (RR, 1.24; 95% CI, 1.01-1.51) were significantly associated with a male excess. These findings underscore varying patterns for the SSR in relation to parental exposures. Given the absence of previous investigation, these partner-specific associations of non-persistent chemicals with the SSR need future corroboration.

  18. Couples’ Urinary Bisphenol A and Phthalate Metabolite Concentrations and the Secondary Sex Ratio

    PubMed Central

    Bae, Jisuk; Kim, Sungduk; Kannan, Kurunthachalam; Buck Louis, Germaine M.

    2015-01-01

    With limited research focusing on non-persistent chemicals as exogenous factors affecting human sex selection, this study aimed to evaluate the association of urinary bisphenol A (BPA) and phthalate metabolite concentrations with the secondary sex ratio (SSR), defined as the ratio of male to female live births. The current analysis is limited to singleton live births (n=220, 43.9%) from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study, which enrolled couples upon discontinuing contraception and followed while trying for pregnancy and through delivery those achieving pregnancy. Using modified Poisson regression models accounting for potential confounders, we estimated the relative risks (RRs) of a male birth per standard deviation change in the log-transformed maternal, paternal, and couple urinary BPA and 14 phthalate metabolite concentrations (ng/mL) measured upon enrollment. When maternal and paternal chemical concentrations were modeled jointly, paternal BPA (RR, 0.77; 95% confidence interval [CI], 0.62–0.95) and mono-isobutyl phthalate (RR, 0.82; 95% CI, 0.67–1.00) were significantly associated with a female excess. Contrarily, maternal BPA (RR, 1.16; 95% CI, 1.03–1.31), mono-isobutyl phthalate (RR, 1.28; 95% CI, 1.06–1.54), mono-benzyl phthalate (RR, 1.31; 95% CI, 1.08–1.58), and mono-n-butyl phthalate (RR, 1.24; 95% CI, 1.01–1.51) were significantly associated with a male excess. These findings underscore varying patterns for the SSR in relation to parental exposures. Given the absence of previous investigation, these partner-specific associations of non-persistent chemicals with the SSR need future corroboration. PMID:25677702

  19. Effect of separating bull semen into X and Y chromosome-bearing fractions on the sex ratio of resulting embryos.

    PubMed Central

    Hagele, W C; Hare, W C; Singh, E L; Grylls, J L; Abt, D A

    1984-01-01

    Seventy-six, day 12 to day 15 bovine embryos, collected from 14 donors which had been inseminated with either X or Y chromosome-bearing spermatozoa fractions of semen separated by a thermal convection counterstreaming sedimentation and forced convection galvanization process, were processed for sexing by chromosomal analysis. Fifty-seven embryos were sexed; 20 from Y chromosome-bearing and 37 from X chromosome-bearing fractions of semen. Statistical analysis of the sexing data indicated that there was no significant difference in the male: female ratio for donors receiving male fractions compared to those receiving female fractions. The Y chromosome-bearing fractions produced a male: female ratio that was indistinguishable from the expected 1:1 ratio. However, the X chromosome-bearing fractions of semen produced a highly significant deviation from the expected 1:1 ratio towards the male. PMID:6478299

  20. Sexual shape and size dimorphism in carabid beetles of the genus Ceroglossus: is geometric body size similar between sexes due to sex ratio?

    PubMed

    Benítez, Hugo A; Sanzana, Maria-José; Jerez, Viviane; Parra, Luis E; Hernández, Cristián E; Canales-Aguirre, Cristian B

    2013-04-01

    Insects in many species vary greatly in the expression of secondary sexual traits, resulting in sexual dimorphism, which has been proposed to be a consequence of differences in sexual selection. In this study, we analyze the occurrence of sexual shape dimorphism and the correlation between geometric body size in males and females and sex ratio in the genus Ceroglossus (Coleoptera: Carabidae) using geometric morphometrics and randomization analysis. Our results show a positive relationship between the centroid size of males and females and sex ratio. However, we also observed a trend to maintain a "similar" body shape between sexes and species due to characteristics associated with sexual selection of the group in which the scarcity of outstanding morphological characters does not restrict reproduction capacity. The trend in sexual proportions was found to be near 1:1 for the eight species. We propose that the observed differences between sexes associated with the sex ratio are due to an energy cost caused by sexual selection; nevertheless, since proportions are similar for all the species, it is really not relevant to generate more conspicuous structures for a stronger male-male competence.

  1. Homomorphic plant sex chromosomes are coming of age.

    PubMed

    Filatov, Dmitry A

    2015-07-01

    Sex chromosomes are a very peculiar part of the genome that have evolved independently in many groups of animals and plants (Bull ). Major research efforts have so far been focused on large heteromorphic sex chromosomes in a few animal and plant species (Chibalina & Filatov ; Zhou & Bachtrog ; Bellott et al. ; Hough et al. ; Zhou et al. ), while homomorphic (cytologically indistinguishable) sex chromosomes have largely been neglected. However, this situation is starting to change. In this issue, Geraldes et al. () describe a small (~100 kb long) sex-determining region on the homomorphic sex chromosomes of poplars (Populus trichocarpa and related species, Fig. ). All species in Populus and its sister genus Salix are dioecious, suggesting that dioecy and the sex chromosomes, if any, should be relatively old. Contrary to this expectation, Geraldes et al. () demonstrate that the sex-determining region in poplars is of very recent origin and probably evolved within the genus Populus only a few million years ago.

  2. Do mothers prefer helpers or smaller litters? Birth sex ratio and litter size adjustment in cotton-top tamarins (Saguinus oedipus)

    PubMed Central

    Boulton, Rebecca A; Fletcher, Alison W

    2015-01-01

    Sex allocation theory has been a remarkably productive field in behavioral ecology with empirical evidence regularly supporting quantitative theoretical predictions. Across mammals in general and primates in particular, however, support for the various hypotheses has been more equivocal. Population-level sex ratio biases have often been interpreted as supportive, but evidence for small-scale facultative adjustment has rarely been found. The helper repayment (HR) also named the local resource enhancement (LRE) hypothesis predicts that, in cooperatively breeding species, mothers invest more in the sex which assists with rearing future offspring and that this bias will be more pronounced in mothers who require extra assistance (i.e., due to inexperience or a lack of available alloparents). We tested these hypotheses in captive cotton-top tamarins (Saguinus oedipus) utilizing the international studbook and birth records obtained through a questionnaire from ISIS-registered institutions. Infant sex, litter size, mother's age, parity, and group composition (presence of nonreproductive subordinate males and females) were determined from these records. The HR hypothesis was supported over the entire population, which was significantly biased toward males (the “helpful” sex). We found little support for helper repayment at the individual level, as primiparous females and those in groups without alloparents did not exhibit more extreme tendencies to produce male infants. Primiparous females were, however, more likely to produce singleton litters. Singleton births were more likely to be male, which suggests that there may be an interaction between litter size adjustment and sex allocation. This may be interpreted as supportive of the HR hypothesis, but alternative explanations at both the proximate and ultimate levels are possible. These possibilities warrant further consideration when attempting to understand the ambiguous results of primate sex ratio studies so far

  3. Do mothers prefer helpers or smaller litters? Birth sex ratio and litter size adjustment in cotton-top tamarins (Saguinus oedipus).

    PubMed

    Boulton, Rebecca A; Fletcher, Alison W

    2015-02-01

    Sex allocation theory has been a remarkably productive field in behavioral ecology with empirical evidence regularly supporting quantitative theoretical predictions. Across mammals in general and primates in particular, however, support for the various hypotheses has been more equivocal. Population-level sex ratio biases have often been interpreted as supportive, but evidence for small-scale facultative adjustment has rarely been found. The helper repayment (HR) also named the local resource enhancement (LRE) hypothesis predicts that, in cooperatively breeding species, mothers invest more in the sex which assists with rearing future offspring and that this bias will be more pronounced in mothers who require extra assistance (i.e., due to inexperience or a lack of available alloparents). We tested these hypotheses in captive cotton-top tamarins (Saguinus oedipus) utilizing the international studbook and birth records obtained through a questionnaire from ISIS-registered institutions. Infant sex, litter size, mother's age, parity, and group composition (presence of nonreproductive subordinate males and females) were determined from these records. The HR hypothesis was supported over the entire population, which was significantly biased toward males (the "helpful" sex). We found little support for helper repayment at the individual level, as primiparous females and those in groups without alloparents did not exhibit more extreme tendencies to produce male infants. Primiparous females were, however, more likely to produce singleton litters. Singleton births were more likely to be male, which suggests that there may be an interaction between litter size adjustment and sex allocation. This may be interpreted as supportive of the HR hypothesis, but alternative explanations at both the proximate and ultimate levels are possible. These possibilities warrant further consideration when attempting to understand the ambiguous results of primate sex ratio studies so far.

  4. The effect of size and sex ratio experiences on reproductive competition in Nicrophorus vespilloides burying beetles in the wild.

    PubMed

    Hopwood, P E; Moore, A J; Tregenza, T; Royle, N J

    2016-03-01

    Male parents face a choice: should they invest more in caring for offspring or in attempting to mate with other females? The most profitable course depends on the intensity of competition for mates, which is likely to vary with the population sex ratio. However, the balance of pay-offs may vary among individual males depending on their competitive prowess or attractiveness. We tested the prediction that sex ratio and size of the resource holding male provide cues regarding the level of mating competition prior to breeding and therefore influence the duration of a male's biparental caring in association with a female. Male burying beetles, Nicrophorus vespilloides were reared, post-eclosion, in groups that differed in sex ratio. Experimental males were subsequently translocated to the wild, provided with a breeding resource (carcass) and filmed. We found no evidence that sex ratio cues prior to breeding affected future parental care behaviour but males that experienced male-biased sex ratios took longer to attract wild mating partners. Smaller males attracted a higher proportion of females than did larger males, securing significantly more monogamous breeding associations as a result. Smaller males thus avoided competitive male-male encounters more often than larger males. This has potential benefits for their female partners who avoid both intrasexual competition and direct costs of higher mating frequency associated with competing males.

  5. Immune function, sex ratios, and gonadal histopathology in double-crested cormorant chicks

    SciTech Connect

    Burull, E.J.; Goldberg, D.R.; Sileo, L.; Dale, T.; Allen, P.D.; Stromborg, K.L.; Larson, J.X.; Fry, D.M.

    1994-12-31

    There is evidence that environmental contaminants may be associated with endocrine and reproductive system abnormalities in colonial water birds. Little information is available on immune system response in chicks. Two double-crested cormorant (Phalocrocrozax auritus) colonies were monitored in 1993 for a comparative immune function study. Higher concentrations of organochlorines occurred in one colony. Parameters measured included: CBC, T and B-cell function, heterophil phagocytosis, lymphoid organ size and histopathology, and selected serum hormone analysis. Significant differences at the contaminated site included marked dysplasia and hypertrophy of thyroid gland, higher T3, lower cortisol, lower eosinophil counts, and increase phagocytosis at the contaminated site. Gonads of 101 deformed (cross-bill) chicks, siblings, and normal control chicks collected in 1992 and 1993 were examined microscopically because a sex-ration skewed towards females had been noted. Cross-billed chicks aged 12 to 15 days had disorganized or delayed follicular development which normalized by 20 days of age. Cross-billed or otherwise abnormal chicks aged 18 to 23 days had hypertrophic seminiferous tubules, a decreased interstitium, and decreased evidence of active Leydig cells.

  6. Sex differences in cognition are stable over a 10-year period in adulthood and old age.

    PubMed

    de Frias, Cindy M; Nilsson, Lars-Göran; Herlitz, Agneta

    2006-01-01

    Sex differences in declarative memory and visuospatial ability are robust in cross-sectional studies. The present longitudinal study examined whether sex differences in cognition were present over a 10-year period, and whether age modified the magnitude of sex differences. Tests assessing episodic and semantic memory, and visuospatial ability were administered to 625 nondemented adults (initially aged 35-80 years), participating in the population-based Betula study at two follow-up occasions. There was stability of sex differences across five age groups and over a 10-year period. Women performed at a higher level than men on episodic recall, face and verbal recognition, and semantic fluency, whereas men performed better than women on a task-assessing, visuospatial ability. Sex differences in cognitive functions are stable over a 10-year period and from 35 to 90 years of age.

  7. Community psychological stressor-induced secondary sex ratio decline after a seismic sequence in the Greek island of Zakynthos.

    PubMed

    Tourikis, John D; Beratis, Ion N

    2013-03-01

    The secondary sex ratio (the ratio of boys to girls at birth) may demonstrate a decline following community stress-inducing major destructive events. This study aims to investigate whether or not moderate adverse life events, in conjunction with endogenous psychological characteristics, can induce sufficient community stress to affect the sex ratio. From April 3rd to May 8th 2006 a moderate sized earthquake sequence occurred offshore the Greek island of Zakynthos, which had been hit by a destructive earthquake half a century earlier. The monthly sex ratio after the earthquake sequence was estimated and compared with that of previous and following years. Eleven months after the onset of the earthquakes the sex ratio fell to 1.000, and during the next two months (March and April) it declined further to 0.612. The sex ratio one year before its decline was 1.158 and over a total 6-year period, 3 years before and 3 years after the sequence, it was 1.063; the March-April decline in male births is significant (OR=0.53, 95% CI=0.32-0.86, p=0.013, and OR=0.57, 95% CI=0.36-0.91, p=0.023, respectively). Also, the number of boys relative to girls in March-April 2007 was significantly lower than during the same months 3 years before and after the sequence (OR=0.50, 95% CI=0.31-0.82, p=0.007). The findings suggest that basic biological characteristics, such as the sex ratio, can be affected by psychological stressors interwoven with the pertaining psychology of the population.

  8. Genotype by Sex and Genotype by Age Interactions with Sedentary Behavior: The Portuguese Healthy Family Study

    PubMed Central

    Santos, Daniel M. V.; Katzmarzyk, Peter T.; Diego, Vincent P.; Blangero, John; Souza, Michele C.; Freitas, Duarte L.; Chaves, Raquel N.; Gomes, Thayse N.; Santos, Fernanda K.; Maia, José A. R.

    2014-01-01

    Sedentary behavior (SB) expression and its underlying causal factors have been progressively studied, as it is a major determinant of decreased health quality. In the present study we applied Genotype x Age (GxAge) and Genotype x Sex (GxSex) interaction methods to determine if the phenotypic expression of different SB traits is influenced by an interaction between genetic architecture and both age and sex. A total of 1345 subjects, comprising 249 fathers, 327 mothers, 334 sons and 325 daughters, from 339 families of The Portuguese Healthy Family Study were included in the analysis. SB traits were assessed by means of a 3-d physical activity recall, the Baecke and IPAQ questionnaires. GxAge and GxSex interactions were analyzed using SOLAR 4.0 software. Sedentary behaviour heritability estimates were not always statistically significant (p>0.05) and ranged from 3% to 27%. The GxSex and GxAge interaction models were significantly better than the single polygenic models for TV (min/day), EEsed (kcal/day), personal computer (PC) usage and physical activty (PA) tertiles. The GxAge model is also significantly better than the polygenic model for Sed (min/day). For EEsed, PA tertiles, PC and Sed, the GxAge interaction was significant because the genetic correlation between SB environments was significantly different from 1. Further, PC and Sed variance heterogeneity among distinct ages were observed. The GxSex interaction was significant for EEsed due to genetic variance heterogeneity between genders and for PC due to a genetic correlation less than 1 across both sexes. Our results suggest that SB expression may be influenced by the interactions between genotype with both sex and age. Further, different sedentary behaviors seem to have distinct genetic architectures and are differentially affected by age and sex. PMID:25302714

  9. The Influence of the Size, Age and Sex on the Computed Tomographic Measured Size of the Pituitary Gland in Normal Horses.

    PubMed

    Crijns, C P; Van Bree, H J; Broeckx, B J G; Schauvliege, S; Van Loon, G; Martens, A; Vanderperren, K; Dingemanse, W B; Gielen, I M

    2017-02-27

    The objective of this study was to examine the influence of the size, age and sex of the horse on the size of the pituitary gland and determine the possibility of using the pituitary gland height-to-brain area ratio (P:B ratio) to allow comparison of different sized and aged horses. Thirty-two horses without pituitary pars inter-media dysfunction that underwent a contrast-enhanced computed tomographic (CT) examination were included in a cross-sectional study. On the CT images, the pituitary gland height was measured and the P:B ratio was calculated. These measurements were correlated to the size, age and sex of the horses. The pituitary gland height was significantly associated with the size (P < 0.001) and the age (P < 0.001), but not with the sex (P = 0.40), of the horses. No significant association was found between the P:B ratio and the size (P = 0.25), the age (P = 0.06) or the sex (P = 0.25) of the horses. In conclusion, the pituitary gland size varies between different sized and aged horses. The use of the P:B ratio is a valuable metric for making comparisons between the pituitary glands of these horses.

  10. Sex-specific effects of altered competition on nestling growth and survival: an experimental manipulation of brood size and sex ratio.

    PubMed

    Nicolaus, Marion; Michler, Stephanie P M; Ubels, Richard; van der Velde, Marco; Komdeur, Jan; Both, Christiaan; Tinbergen, Joost M

    2009-03-01

    1. An increase of competition among adults or nestlings usually negatively affects breeding output. Yet little is known about the differential effects that competition has on the offspring sexes. This could be important because it may influence parental reproductive decisions. 2. In sexual size dimorphic species, two main contradictory mechanisms are proposed regarding sex-specific effects of competition on nestling performance assuming that parents do not feed their chicks differentially: (i) the larger sex requires more resources to grow and is more sensitive to a deterioration of the rearing conditions ('costly sex hypothesis'); (ii) the larger sex has a competitive advantage in intra-brood competition and performs better under adverse conditions ('competitive advantage hypothesis'). 3. In the present study, we manipulated the level of sex-specific sibling competition in a great tit population (Parus major) by altering simultaneously the brood size and the brood sex ratio on two levels: the nest (competition for food among nestlings) and the woodlot where the parents breed (competition for food among adults). We investigated whether altered competition during the nestling phase affected nestling growth traits and survival in the nest and whether the effects differed between males, the larger sex, and females. 4. We found a strong negative and sex-specific effect of experimental brood size on all the nestling traits. In enlarged broods, sexual size dimorphism was smaller which may have resulted from biased mortality towards the less competitive individuals i.e. females of low condition. No effect of brood sex ratio on nestling growth traits was found. 5. Negative brood size effects on nestling traits were stronger in natural high-density areas but we could not confirm this experimentally. 6. Our results did not support the 'costly sex hypothesis' because males did not suffer from higher mortality under harsh conditions. The 'competitive advantage hypothesis' was

  11. A large population parental care game: polymorphisms and feedback between patterns of care and the operational sex ratio.

    PubMed

    Ramsey, David M

    2010-10-21

    This article presents a game theoretic model of parental care which models the feedback between patterns of care and the operational sex ratio. It is assumed here that males can be in one of two states: searching for a mate or breeding (including caring for their offspring). Females can be in one of three states: receptive (searching), non-receptive or breeding. However, these sets of states can be adapted to the physiology of a particular species. The length of time that an individual remains in the breeding state depends on the level of care an individual gives. When in the searching state, individuals find partners at a rate dependent on the proportion of members of the opposite sex searching. These rates are defined to satisfy the Fisher condition that the total number of offspring of males equals the total number of offspring of females. The operational sex ratio is not defined exogenously, but can be derived from the adult sex ratio and the pattern of parental care. Pure strategy profiles and so-called single sex stable polymorphisms, in which behaviour is varied within one sex, are derived analytically. The difference between mixed evolutionarily stable strategies and stable polymorphisms within this framework is highlighted. The effects of various physiological and demographic parameters on patterns of care are considered.

  12. High Calcium-Magnesium Ratio in Hair Is Associated with Coronary Artery Calcification in Middle-Aged and Elderly Individuals.

    PubMed

    Park, Byoungjin; Kim, Mi-Hyun; Cha, Choong Keun; Lee, Yong-Jae; Kim, Kyong-Chol

    2017-02-06

    The interaction between calcium and magnesium as a risk modifier for cardiovascular disease (CVD) has been largely overlooked in previous studies, for the strict regulatory system in blood has been thought to keep such homeostatic interactions under tight control. This study aimed to investigate the association between calcium-magnesium ratio in hair and subclinical coronary artery calcification. Using multiple linear regression analysis, we examined the associations between calcium-magnesium ratio in hair and the coronary calcium score (CCS) in 216 Koreans aged 40 years and above (122 men and 94 women). We found that the calcium-to-magnesium ratio in hair was independently and positively associated with CCS after adjusting for age and sex (regression coefficient 6.051 ± 2.329, P = 0.010). When we assessed the association between the calcium-magnesium ratio and CCS after adjusting for potential cardiovascular risk factors and vascular function modifying drugs, we found that the strength of association with CCS was comparable to before (regression coefficient 5.434 ± 2.523, P = 0.032). Our findings suggest that among middle-aged and elderly Koreans without clinical CVD, the association between coronary artery calcification and hair calcium-magnesium ratio is stronger in those with a higher calcium-magnesium ratio in hair than in those with a lower ratio.

  13. Does famine influence sex ratio at birth? Evidence from the 1959-1961 Great Leap Forward Famine in China.

    PubMed

    Song, Shige

    2012-07-22

    The current study examined the long-term trend in sex ratio at birth between 1929 and 1982 using retrospective birth histories of 310 101 Chinese women collected in a large, nationally representative sample survey in 1982. The study identified an abrupt decline in sex ratio at birth between April 1960, over a year after the Great Leap Forward Famine began, and October 1963, approximately 2 years after the famine ended, followed by a compensatory rise between October 1963 and July 1965. These findings support the adaptive sex ratio adjustment hypothesis that mothers in good condition are more likely to give birth to sons, whereas mothers in poor condition are more likely to give birth to daughters. In addition, these findings help explain the lack of consistent evidence reported by earlier studies based on the 1944-1945 Dutch Hunger Winter or the 1942 Leningrad Siege.

  14. Effects of gamma radiation on development, sterility, fecundity, and sex ratio of Dermanyssus gallinae (DeGeer) (Acari: Dermanyssidae)

    SciTech Connect

    Entrekin, D.L.; Oliver, J.H. Jr.; Pound, J.M.

    1987-06-01

    Protonymphal Dermanyssus gallinae were irradiated with 0.50, 0.75, 1.0, 3.0, and 6.0 krad of gamma radiation and subsequently monitored regarding their developmental, feeding, and mating success. Also, sex ratios of adults treated as protonymphs were recorded as were sex ratios of embryos and F1 adults produced by these adults. Doses up to 1.0 krad did not prevent development of treated protonymphs to the adult stage or stop mating. Three krad reduced the number of treated protonymphs attaining adulthood and 6.0-krad treatment prevented all mites from developing to the adult stage. Egg (embryo) production was normal for mites treated with 0.50 krad, but significantly curtailed by doses of 0.75 krad and greater. Radiation doses used in this study did not appear to affect the normal variable sex ratios observed in untreated mites.

  15. Female Fertilization: Effects of Sex-Specific Density and Sex Ratio Determined Experimentally for Colorado Potato Beetles and Drosophila Fruit Flies

    PubMed Central

    Vahl, Wouter K.; Boiteau, Gilles; de Heij, Maaike E.; MacKinley, Pamela D.; Kokko, Hanna

    2013-01-01

    If males and females affect reproduction differentially, understanding and predicting sexual reproduction requires specification of response surfaces, that is, two-dimensional functions that relate reproduction to the (numeric) densities of both sexes. Aiming at rigorous measurement of female per capita fertilization response surfaces, we conducted a multifactorial experiment and reanalyzed an extensive data set. In our experiment, we varied the density of male and female Leptinotarsa decemlineata (Colorado potato beetles) by placing different numbers of the two sexes on enclosed Solanum tuberosum (potato plants) to determine the proportion of females fertilized after 3 or 22 hours. In the reanalysis, we investigated how the short-term fertilization probability of three Drosophila strains (melanogaster ebony, m. sepia, and simulans) depended on adult sex ratio (proportion of males) and total density. The fertilization probability of female Leptinotarsa decemlineata increased logistically with male density, but not with female density. These effects were robust to trial duration. The fertilization probability of female Drosophila increased logistically with both sex ratio and total density. Treatment effects interacted in m. sepia, and simulans. These findings highlight the importance of well-designed, multifactorial experiments and strengthen previous experimental evidence for the relevance of sex-specific densities to understanding and prediction of female fertilization probability. PMID:23593206

  16. Female fertilization: effects of sex-specific density and sex ratio determined experimentally for Colorado potato beetles and Drosophila fruit flies.

    PubMed

    Vahl, Wouter K; Boiteau, Gilles; de Heij, Maaike E; MacKinley, Pamela D; Kokko, Hanna

    2013-01-01

    If males and females affect reproduction differentially, understanding and predicting sexual reproduction requires specification of response surfaces, that is, two-dimensional functions that relate reproduction to the (numeric) densities of both sexes. Aiming at rigorous measurement of female per capita fertilization response surfaces, we conducted a multifactorial experiment and reanalyzed an extensive data set. In our experiment, we varied the density of male and female Leptinotarsa decemlineata (Colorado potato beetles) by placing different numbers of the two sexes on enclosed Solanum tuberosum (potato plants) to determine the proportion of females fertilized after 3 or 22 hours. In the reanalysis, we investigated how the short-term fertilization probability of three Drosophila strains (melanogaster ebony, m. sepia, and simulans) depended on adult sex ratio (proportion of males) and total density. The fertilization probability of female Leptinotarsa decemlineata increased logistically with male density, but not with female density. These effects were robust to trial duration. The fertilization probability of female Drosophila increased logistically with both sex ratio and total density. Treatment effects interacted in m. sepia, and simulans. These findings highlight the importance of well-designed, multifactorial experiments and strengthen previous experimental evidence for the relevance of sex-specific densities to understanding and prediction of female fertilization probability.

  17. Plexogenic arteriopathy in broiler lungs: Evaluation of line, age, and sex influences1

    PubMed Central

    Wideman, R. F.; Mason, J. G.; Anthony, N. B.; Cross, D.

    2015-01-01

    Plexiform lesions form in the terminal pulmonary arterioles of human patients suffering from prolonged pulmonary arterial hypertension. Plexiform lesions also develop in broiler lungs, but lesion incidences are not strongly correlated with sustained pulmonary hypertension as reflected by right to total ventricular weight (RVTV) ratios. The present study was conducted to assess plexiform lesion incidences in broiler lines that have been divergently selected for susceptibility or resistance to pulmonary hypertension. Broilers from susceptible (SUS) and resistant (RES) lines were reared together and only clinically healthy (nonascitic, noncyanotic) individuals were evaluated to minimize potential line differences in cardiopulmonary hemodynamics. The objective was to determine if an innate genetic predisposition for plexogenic arteriopathy would be exposed in SUS broilers when compared with RES broilers in the absence of extreme differences in cardiopulmonary hemodynamics. Broilers up to 12 wk age from the SUS and RES lines had essentially equivalent BW, indices of cardiopulmonary function (left ventricle + septum weight, total ventricle weight, and RVTV ratios), and lung volumes within a sex. Average RVTV ratios for broilers from both lines were indicative of normal pulmonary arterial pressures at all ages sampled. Nevertheless, plexiform lesions were detected in SUS and RES broiler lungs immediately posthatch and thereafter at all ages sampled. Lesion incidences were consistently low and did not differ between the lines within any of the sampling ages. This evidence demonstrates that plexiform lesions develop extremely rapidly in broiler chicks, apparently without the prerequisite for vascular stress caused by severe, prolonged pulmonary arterial hypertension. No innate genetic predisposition for complex vascular lesion development appeared to exist in the SUS line when compared with the RES line. PMID:25681478

  18. Associations between AUDIT-C and mortality vary by age and sex.

    PubMed

    Harris, Alex H S; Bradley, Katharine A; Bowe, Thomas; Henderson, Patricia; Moos, Rudolf

    2010-10-01

    We sought to determine the sex- and age-specific risk of mortality associated with scores on the 3-item Alcohol Use Disorder Identification Test-Consumption (AUDIT-C) questionnaire using data from a national sample of Veterans Health Administration (VHA) patients. Men (N = 215,924) and women (N = 9168) who completed the AUDIT-C in a patient survey were followed for 24 months. AUDIT-C categories (0, 1-4, 5-8, 9-12) were evaluated as predictors of mortality in logistic regression models, adjusted for age, race, education, marital status, smoking, depression, and comorbidities. For women, AUDIT-C scores of 9-12 were associated with a significantly increased risk of death compared to the AUDIT-C 1-4 group (odds ratio [OR] 7.09; 95% confidence interval [CI] = 2.67, 18.82). For men overall, AUDIT-C scores of 5-8 and 9-12 were associated with increased risk of death compared to the AUDIT-C 1-4 group (OR 1.13, 95% CI = 1.05, 1.21, and OR 1.63, 95% CI = 1.45, 1.84, respectively) but these associations varied by age. These results provide sex- and age-tailored risk information that clinicians can use in evidence-based conversations with patients about the health-related risks of their alcohol consumption. This study adds to the growing literature establishing the AUDIT-C as a scaled marker of alcohol-related risk or "vital sign" that might facilitate the detection and management of alcohol-related risks and problems.

  19. Sex disparities in colorectal cancer incidence by anatomic subsite, race and age.

    PubMed

    Murphy, Gwen; Devesa, Susan S; Cross, Amanda J; Inskip, Peter D; McGlynn, Katherine A; Cook, Michael B

    2011-04-01

    Although incidence of colorectal cancer (CRC) in the United States has declined in recent years, rates remain higher in men than in women and the male-to-female incidence rate ratio (MF IRR) increases progressively across the colon from the cecum to the rectum. Rates among races/ethnicities other than Whites or Blacks have not been frequently reported. To examine CRC rates by sex across anatomic subsite, age and racial/ethnic groups, we used the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program for cases diagnosed among residents of 13 registries during 1992-2006. Incidence rates were expressed per 100,000 person-years and age-adjusted to the 2000 US Standard Population; MF IRR and 95% confidence intervals were also calculated. Among each racial/ethnic group, the MF IRR increased fairly monotonically from close to unity for cecal cancers to 1.81 (Hispanics) for rectal cancers. MF IRRs increased with age most rapidly for distal colon cancers from <1.0 at ages <50 years to 1.4-1.9 at older ages. The MF IRR for rectal cancers also rose with age from about 1.0 to 2.0. For proximal cancer, the MF IRR was consistently <1.5; among American Indian/Alaska Natives, it was <1.0 across all ages. The MF IRRs for CRC vary markedly according to subsite and age but less by racial/ethnic group. These findings may partially reflect differences in screening experiences and access to medical care but also suggest that etiologic factors may be playing a role.

  20. Collateral Consequences: Implications of male incarceration rates, imbalanced sex ratios and partner availability for heterosexual Black women

    PubMed Central

    Dauria, Emily F.; Oakley, Lisa; Jacob Arriola, Kimberly; Elifson, Kirk; Wingood, Gina; Cooper, Hannah L. F.

    2015-01-01

    While studies have found correlations between rates of incarceration and STIs, few have explored the mechanisms linking these phenomena. This qualitative study examines how male incarceration rates and sex ratios influence perceived partner availability and sexual partnerships for heterosexual Black women. Semi-structured interviews were conducted with 33 Black women living in two US neighbourhoods: one with a high male incarceration rate and an imbalanced sex ratio (referred to as “Allentown”) and one with a low male incarceration rate and an equitable sex ratio (referred to as “Blackrock”). Data were analysed using grounded theory. In Allentown, male incarceration reduced the number of available men; participants largely viewed men available for partnerships as being of an undesirable quality. The number and desirability of men impacted on the nature of partnerships such that they were shorter, focused on sexual activity, and may be with higher risk sexual partners (e.g. transactional sex partners). In Blackrock, marriage rates contributed to the shortage of desirable male partners. By highlighting the role that the quantity and quality of male partners has on shaping sexual partnerships, this study advances current understandings of how incarceration and sex ratios shape HIV- and STI-related risk. PMID:26056724

  1. Collateral consequences: implications of male incarceration rates, imbalanced sex ratios and partner availability for heterosexual Black women.

    PubMed

    Dauria, Emily F; Oakley, Lisa; Arriola, Kimberly Jacob; Elifson, Kirk; Wingood, Gina; Cooper, Hannah L F

    2015-01-01

    While studies have found correlations between rates of incarceration and sexually transmitted infections (STIs), few studies have explored the mechanisms linking these phenomena. This qualitative study examines how male incarceration rates and sex ratios influence perceived partner availability and sexual partnerships for heterosexual Black women. Semi-structured interviews were conducted with 33 Black women living in two US neighbourhoods, one with a high male incarceration rate and an imbalanced sex ratio (referred to as 'Allentown') and one with a low male incarceration rate and an equitable sex ratio (referred to as 'Blackrock'). Data were analysed using grounded theory. In Allentown, male incarceration reduced the number of available men, and participants largely viewed men available for partnerships as being of an undesirable quality. The number and desirability of men impacted on the nature of partnerships such that they were shorter, focused on sexual activity and may be with higher-risk sexual partners (e.g. transactional sex partners). In Blackrock, marriage rates contributed to the shortage of desirable male partners. By highlighting the role that the quantity and quality of male partners has on shaping sexual partnerships, this study advances current understandings of how incarceration and sex ratios shape HIV- and STI-related risk.

  2. Sexual system, sex ratio, and group living in the shrimp Thor amboinensis (De Man): relevance to resource-monopolization and sex-allocation theories.

    PubMed

    Baeza, J A; Piantoni, C

    2010-10-01

    The sexual system of the symbiotic shrimp Thor amboinensis is described, along with observations on sex ratio and host-use pattern of different populations. We used a comprehensive approach to elucidate the previously unknown sexual system of this shrimp. Dissections, scanning electron microscopy, size-frequency distribution analysis, and laboratory observations demonstrated that T. amboinensis is a protandric hermaphrodite: shrimp first mature as males and change into females later in life. Thor amboinensis inhabited the large and structurally heterogeneous sea anemone Stichodactyla helianthus in large groups (up to 11 individuals) more frequently than expected by chance alone. Groups exhibited no particularly complex social structure and showed male-biased sex ratios more frequently than expected by chance alone. The adult sex ratio was male-biased in the four separate populations studied, one of them being thousands of kilometers apart from the others. This study supports predictions central to theories of resource monopolization and sex allocation. Dissections demonstrated that unusually large males were parasitized by an undescribed species of isopod (family Entoniscidae). Infestation rates were similarly low in both sexes (≈11%-12%). The available information suggests that T. amboinensis uses pure search promiscuity as a mating system. This hypothesis needs to be formally tested with mating behavior observations and field measurements on the movement pattern of both sexes of the species. Further detailed studies on the lifestyle and sexual system of all the species within this genus and the development of a molecular phylogeny are necessary to elucidate the evolutionary history of gender expression in the genus Thor.

  3. Past primary sex-ratio estimates of 4 populations of Loggerhead sea turtle based on TSP durations.

    NASA Astrophysics Data System (ADS)

    Monsinjon, Jonathan; Kaska, Yakup; Tucker, Tony; LeBlanc, Anne Marie; Williams, Kristina; Rostal, David; Girondot, Marc

    2016-04-01

    Ectothermic species are supposed to be strongly affected by climate change and particularly those that exhibit temperature-dependent sex-determination (TSD). Actually, predicting the embryonic response of such organism to incubation-temperature variations in natural conditions remains challenging. In order to assess the vulnerability of sea turtles, primary sex-ratio estimates should be produced at pertinent ecological time and spatial scales. Although information on this important demographic parameter is one of the priorities for conservation purpose, accurate methodology to produce such an estimate is still lacking. The most commonly used method invocates incubation duration as a proxy for sex-ratio. This method is inappropriate because temperature influences incubation duration during all development whereas sex is influenced by temperature during only part of development. The thermosensitive period of development for sex determination (TSP) lies in the middle third of development. A model of embryonic growth must be used to define precisely the position of the TSP at non-constant incubation temperatures. The thermal reaction norm for embryonic growth rate have been estimated for 4 distinct populations of the globally distributed and threatened marine turtle Caretta caretta. A thermal reaction norm describes the pattern of phenotypic expression of a single genotype across a range of temperatures. Moreover, incubation temperatures have been reconstructed for the last 35 years using a multi-correlative model with climate temperature. After development of embryos have been modelled, we estimated the primary sex-ratio based on the duration of the TSP. Our results suggests that Loggerhead sea turtles nesting phenology is linked with the period within which both sexes can be produced in variable proportions. Several hypotheses will be discussed to explain why Caretta caretta could be more resilient to climate change than generally thought for sex determination.

  4. The association between male-biased sex ratio and indicators of stress in red-spotted newts.

    PubMed

    Aspbury, Andrea S; Grayson, Kristine L; Fantaye, Selamawit; Nichols, Ian; Myers-Burton, Miranda; Ortiz-Mangual, Xavier; Gabor, Caitlin R

    2017-05-01

    In populations with a male-biased operational sex ratio, coercive mating by males can have fitness consequences for females. One component of reduced fitness for females in populations with a male-biased OSR may be greater activation of the stress response, resulting in higher corticosterone release rates (CORT; a glucocorticoid stress hormone in amphibians). We test the hypothesis that a male-biased sex ratio affects female activity and release rates of CORT and testosterone (T) in male and female red-spotted newts (Notophthalmus viridescens). First, we evaluated if chemical cues from a male-biased sex ratio affect activity and CORT release rates in females. We predicted that females exposed to chemical cues of three males would be less active and have higher CORT release rates than those exposed to chemical cues of one male. Second, we measured CORT release rates of red-spotted newts in field enclosures with either a male-biased or a female-biased sex ratio. We predicted that females in the male-biased treatment would have higher CORT and T release rates than those in a female-biased treatment, owing to higher levels of male harassment. We also predicted that males would have higher CORT and T release rates in male-biased treatments due to higher levels of male-male competition. Females were not less active in response to chemical cues from more males over fewer males, but there was a positive relationship between female activity and CORT when they were exposed to the cues of three males. We also found that females, but not males, in the male-biased sex ratio treatment had higher CORT and T release rates than those in the female-biased treatment. Our results support the hypothesis that a male-biased sex ratio leads to a higher stress response, which may underlie the observed decrease in immune function and body condition in previous work exposing female red-spotted newts to a male-biased sex ratio. This study furthers our understanding of the mechanistic basis

  5. Couples' urinary concentrations of benzophenone-type ultraviolet filters and the secondary sex ratio.

    PubMed

    Bae, Jisuk; Kim, Sungduk; Kannan, Kurunthachalam; Buck Louis, Germaine M

    2016-02-01

    The secondary sex ratio (SSR), defined as the ratio of males to females at birth, has been investigated in relation to endocrine disruptors to search for environmental toxicants perturbing human sex selection. Benzophenone (BP)-type ultraviolet (UV) filters, which are used in sunscreens and personal care products, have been reported to exert estrogenic and anti-androgenic activities. This study aimed to evaluate the association between maternal, paternal, and couple urinary concentrations of BP-type UV filters and the SSR, given the absence of previous investigation. The study cohort comprised 220 couples who were enrolled in the Longitudinal Investigation of Fertility and the Environment (LIFE) Study between 2005 and 2009 prior to conception and who had a singleton birth during the follow-up period. Couples' urinary concentrations of five BP-type UV filters (ng/mL) were measured using triple-quadrupole tandem mass spectrometry: 2,4-dihydroxybenzophenone (BP-1), 2,2',4,4'-tetrahydroxybenzophenone (BP-2), 2-hydroxy-4-methoxybenzophenone (BP-3), 2,2'-dihydroxy-4-methoxybenzophenone (BP-8), and 4-hydroxybenzophenone (4-OH-BP). Modified Poisson regression models were used to estimate the relative risks (RRs) of a male birth for each BP-type UV filter, after adjusting for potential confounders. When maternal and paternal urinary BP-type UV filter concentrations were modeled jointly, both maternal BP-2 (2nd vs 1st tertile, RR, 0.62, 95% confidence interval [CI], 0.43-0.91) and paternal BP-2 (3rd vs 1st tertile, RR, 0.67, 95% CI, 0.45-0.99; p-trend, 0.04) were significantly associated with an excess of female births. Contrarily, maternal 4-OH-BP was significantly associated with an excess of male births (2nd vs 1st tertile, RR, 1.87, 95% CI, 1.27-2.74; 3rd vs 1st tertile, RR, 1.80, 95% CI, 1.13-2.87; p-trend, 0.02). Our findings provide the first evidence suggesting that BP-type UV filters may affect the SSR. However, future corroboration is needed, given the exploratory

  6. Estimating age ratios and size of Pacific walrus herds on coastal haulouts using video imaging

    USGS Publications Warehouse

    Monson, Daniel H.; Udevitz, Mark S.; Jay, Chadwick V.

    2013-01-01

    During Arctic summers, sea ice provides resting habitat for Pacific walruses as it drifts over foraging areas in the eastern Chukchi Sea. Climate-driven reductions in sea ice have recently created ice-free conditions in the Chukchi Sea by late summer causing walruses to rest at coastal haulouts along the Chukotka and Alaska coasts, which provides an opportunity to study walruses at relatively accessible locations. Walrus age can be determined from the ratio of tusk length to snout dimensions. We evaluated use of images obtained from a gyro-stabilized video system mounted on a helicopter flying at high altitudes (to avoid disturbance) to classify the sex and age of walruses hauled out on Alaska beaches in 2010–2011. We were able to classify 95% of randomly selected individuals to either an 8- or 3-category age class, and we found measurement-based age classifications were more repeatable than visual classifications when using images presenting the correct head profile. Herd density at coastal haulouts averaged 0.88 walruses/m2 (std. err. = 0.02), herd size ranged from 8,300 to 19,400 (CV 0.03–0.06) and we documented ~30,000 animals along ~1 km of beach in 2011. Within the herds, dependent walruses (0–2 yr-olds) tended to be located closer to water, and this tendency became more pronounced as the herd spent more time on the beach. Therefore, unbiased estimation of herd age-ratios will require a sampling design that allows for spatial and temporal structuring. In addition, randomly sampling walruses available at the edge of the herd for other purposes (e.g., tagging, biopsying) will not sample walruses with an age structure representative of the herd. Sea ice losses are projected to continue, and population age structure data collected with aerial videography at coastal haulouts may provide demographic information vital to ongoing efforts to understand effects of climate change on this species.

  7. Estimating age ratios and size of pacific walrus herds on coastal haulouts using video imaging.

    PubMed

    Monson, Daniel H; Udevitz, Mark S; Jay, Chadwick V

    2013-01-01

    During Arctic summers, sea ice provides resting habitat for Pacific walruses as it drifts over foraging areas in the eastern Chukchi Sea. Climate-driven reductions in sea ice have recently created ice-free conditions in the Chukchi Sea by late summer causing walruses to rest at coastal haulouts along the Chukotka and Alaska coasts, which provides an opportunity to study walruses at relatively accessible locations. Walrus age can be determined from the ratio of tusk length to snout dimensions. We evaluated use of images obtained from a gyro-stabilized video system mounted on a helicopter flying at high altitudes (to avoid disturbance) to classify the sex and age of walruses hauled out on Alaska beaches in 2010-2011. We were able to classify 95% of randomly selected individuals to either an 8- or 3-category age class, and we found measurement-based age classifications were more repeatable than visual classifications when using images presenting the correct head profile. Herd density at coastal haulouts averaged 0.88 walruses/m(2) (std. err. = 0.02), herd size ranged from 8,300 to 19,400 (CV 0.03-0.06) and we documented ∼30,000 animals along ∼1 km of beach in 2011. Within the herds, dependent walruses (0-2 yr-olds) tended to be located closer to water, and this tendency became more pronounced as the herd spent more time on the beach. Therefore, unbiased estimation of herd age-ratios will require a sampling design that allows for spatial and temporal structuring. In addition, randomly sampling walruses available at the edge of the herd for other purposes (e.g., tagging, biopsying) will not sample walruses with an age structure representative of the herd. Sea ice losses are projected to continue, and population age structure data collected with aerial videography at coastal haulouts may provide demographic information vital to ongoing efforts to understand effects of climate change on this species.

  8. Estimating Age Ratios and Size of Pacific Walrus Herds on Coastal Haulouts using Video Imaging

    PubMed Central

    Monson, Daniel H.; Udevitz, Mark S.; Jay, Chadwick V.

    2013-01-01

    During Arctic summers, sea ice provides resting habitat for Pacific walruses as it drifts over foraging areas in the eastern Chukchi Sea. Climate-driven reductions in sea ice have recently created ice-free conditions in the Chukchi Sea by late summer causing walruses to rest at coastal haulouts along the Chukotka and Alaska coasts, which provides an opportunity to study walruses at relatively accessible locations. Walrus age can be determined from the ratio of tusk length to snout dimensions. We evaluated use of images obtained from a gyro-stabilized video system mounted on a helicopter flying at high altitudes (to avoid disturbance) to classify the sex and age of walruses hauled out on Alaska beaches in 2010–2011. We were able to classify 95% of randomly selected individuals to either an 8- or 3-category age class, and we found measurement-based age classifications were more repeatable than visual classifications when using images presenting the correct head profile. Herd density at coastal haulouts averaged 0.88 walruses/m2 (std. err. = 0.02), herd size ranged from 8,300 to 19,400 (CV 0.03–0.06) and we documented ∼30,000 animals along ∼1 km of beach in 2011. Within the herds, dependent walruses (0–2 yr-olds) tended to be located closer to water, and this tendency became more pronounced as the herd spent more time on the beach. Therefore, unbiased estimation of herd age-ratios will require a sampling design that allows for spatial and temporal structuring. In addition, randomly sampling walruses available at the edge of the herd for other purposes (e.g., tagging, biopsying) will not sample walruses with an age structure representative of the herd. Sea ice losses are projected to continue, and population age structure data collected with aerial videography at coastal haulouts may provide demographic information vital to ongoing efforts to understand effects of climate change on this species. PMID:23936106

  9. Effects of larval-juvenile treatment with perchlorate and co-treatment with thyroxine on zebrafish sex ratios

    USGS Publications Warehouse

    Mukhi, S.; Torres, L.; Patino, R.

    2007-01-01

    The objective of this study was to determine the effect of larval-juvenile exposure to perchlorate, a thyroid hormone synthesis inhibitor, on the establishment of gonadal sex ratios in zebrafish. Zebrafish were exposed to untreated water or water containing perchlorate at 100 or 250 ppm for a period of 30 days starting at 3 days postfertilization (dpf). Recovery treatments consisted of a combination of perchlorate and exogenous thyroxine (T4; 10 nM). Thyroid histology was assessed at the end of the treatment period (33 dpf), and gonadal histology and sex ratios were determined in fish that were allowed an additional 10-day period of growth in untreated water. As expected, exposure to perchlorate caused changes in thyroid histology consistent with hypothyroidism and these effects were reversed by co-treatment with exogenous T4. Perchlorate did not affect fish survival but co-treatment with T4 induced higher mortality. However, relative to the corresponding perchlorate concentration, co-treatment with T4 caused increased mortality only at a perchlorate concentration of 100 ppm. Perchlorate alone or in the presence of T4 suppressed body length at 43 dpf relative to control values. Perchlorate exposure skewed the sex ratio toward female in a concentration-dependent manner, and co-treatment with T4 not only blocked the feminizing effect of perchlorate but also overcompensated by skewing the sex ratio towards male. Moreover, co-treatment with T4 advanced the onset of spermatogenesis in males. There was no clear association between sex ratios and larval survival or growth. We conclude that endogenous thyroid hormone plays a role in the establishment of gonadal sex phenotype during early development in zebrafish. ?? 2006 Elsevier Inc. All rights reserved.

  10. An Investigation into the Effect of Respondent Gender, Victim Age, and Perpetrator Treatment on Public Attitudes towards Sex Offenders, Sex Offender Treatment, and Sex Offender Rehabilitation

    ERIC Educational Resources Information Center

    Rogers, Paul; Hirst, Lindsay; Davies, Michelle

    2011-01-01

    In this study the authors examine the effect respondent gender, victim age, and offender treatment programs have upon public attitudes towards sex offenders. A community sample of 235 participants were asked to read a hypothetical vignette involving the sexual assault of a 10-, 15-, or 20-year-old female by a 35-year-old male who subsequently…

  11. The sex ratio of older siblings in non-right-handed homosexual men.

    PubMed

    Blanchard, Ray; Lippa, Richard A

    2008-12-01

    This study tested the prediction, based on prior research, that non-right-handed homosexual men will report fewer than expected older brothers. Participants were 2486 heterosexual and homosexual, right-handed and non-right-handed, male and female adults, representing five samples collected for various projects by the second author. Data on sibship composition, sexual orientation, and hand-preference were gathered in the original research using on-line (Internet) or self-administered paper-and-pencil questionnaires. The non-right-handed homosexual men reported 83 older brothers per 100 older sisters, which was significantly lower than the human sex ratio of 106 live-born males per 100 live-born females. In contrast, the right-handed homosexual men reported 125 older brothers per 100 older sisters, which was significantly higher than the expected ratio. One possible explanation of these results is that older brothers increase the odds of homosexuality in right-handed males but decrease the odds of homosexuality in non-right-handed males. A second possibility is that older brothers decrease the probability that non-right-handed homosexual males will be represented in survey research. The latter scenario could arise if the combination of some biological factor associated with older brothers and some biological factor associated with non-right-handedness is so toxic that it kills the fetus or predisposes the individual to a condition (e.g., mental retardation, major mental illness) that makes him less likely to be available for research recruitment at Gay Pride parades (etc.) than other members of the gay community.

  12. Impact of economic conditions on the secondary sex ratio in a post-communist economy.

    PubMed

    Ządzińska, E; Rosset, I; Mikulec, A; Domański, C; Pawłowski, B

    2011-06-01

    According to the Trivers-Willard hypothesis the secondary sex ratio (SSR, the ratio of male to female newborns [M/F]) should be positively related to the parents' living conditions. This also means that if in some population parents experience environmental (e.g. economic) stress, the SSR should be relatively low. If this holds true, the fluctuations in the SSR of offspring could be one of the ways the human population reacts to environmental (and also socio-economic) changes. Although confirmed for many human populations, such a relationship was not observed in the populations living in the communist-era planned-economy countries until recently. We test the hypothesis that economic stress in Poland after the communist era is also related to the SSR decrease. Using quarterly data from the years 1995-2007 about the total number of live male (M) and female (F) newborns born in central Poland (sample size=310,532), we calculated the time series of the SSR. The quarterly economic conditions of the studied population within the period under consideration constituted the time series of the percentage change in private consumption at constant prices of the year 2000. The relationship between the SSR and the economic conditions in the analyzed 47 quarters of the year was tested with the use of the ARMA models. We have found that four quarters (one year) after the occurrence of economic stress there was a decline in the SSR. This result is consistent with the Trivers-Willard hypothesis at the population level in a modern free-trade economy of a post-communist country.

  13. A review of the established and suspected causes of variations in human sex ratio at birth.

    PubMed

    James, William H; Grech, Victor

    2017-03-24

    The human sex ratio (proportion male) at birth (SRB) varies with many variables. Some of this variation has an established proximate cause. For instance, low SRB (more females) at birth are associated with various forms of stressful events or circumstances during or prior to pregnancy. These low SRB are almost certainly mainly caused by maternal-stress-induced male foetal loss. Other types of SRB variation are thought to be caused by hormonal variation in either or both parents around the time of conception. One or other of these two types of proximate cause seems to be responsible for most of the established variation of SRB. This will be illustrated here in respect of some selected forms of SRB variation. It seems likely that a clarification of the hormonal causes of SRB variation will also help explain the striking (apparent) inconsistencies in the results of reported tests of the influential Trivers-Willard hypothesis. It is further proposed that an appreciation of the evidence that parental hormones influence SRB may enhance understanding of several important pathologies (hepatitis B, toxoplasmosis, testicular cancer, prostate cancer and autism).

  14. Evidence of Hermaphroditism and Sex Ratio Distortion in the Fungal Feeding Nematode Bursaphelenchus okinawaensis

    PubMed Central

    Shinya, Ryoji; Hasegawa, Koichi; Chen, Anthony; Kanzaki, Natsumi; Sternberg, Paul W.

    2014-01-01

    Nematodes have many different reproductive strategies along with their divergent life histories; the ability of hermaphrodite to self- and cross-fertilize is useful for genetic manipulation. Here, we demonstrate the hermaphroditism of the fungal feeding nematode Bursaphelenchus okinawaensis, which was formerly described as a parthenogenetic nematode, and we show its other unique sexual characteristics. To determine that it is hermaphroditic, we performed the following experiments: observation of the pronuclear and chromosome behavior during oogenesis and early embryogenesis; observation of spermatogenesis during the fourth larval stage; investigation of sperm utilization; and investigation of phenotypic segregation after cross-mating using a chemically induced visible mutant. We then investigated the mating preferences and spermatid size difference between males and hermaphrodites. B. okinawaensis males successfully mated only with sperm-depleted old hermaphrodites, and the spermatid sizes of males were almost the same as those of hermaphrodites. Moreover, the sex ratio of cross-fertilized progeny was highly skewed toward hermaphrodites. B. okinawaensis is phylogenetically distant from established model nematodes such as C. elegans and is more closely related to some economically relevant parasitic nematodes. This newly discovered hermaphroditic nematode has great potential for evolutionary and parasitological research. PMID:25122669

  15. Changes in Income at Macro Level Predict Sex Ratio at Birth in OECD Countries.

    PubMed

    Kanninen, Ohto; Karhula, Aleksi

    2016-01-01

    The human sex ratio at birth (SRB) is approximately 107 boys for every 100 girls. SRB was rising until the World War II and has been declining slightly after the 1950s in several industrial countries. Recent studies have shown that SRB varies according to exposure to disasters and socioeconomic conditions. However, it remains unknown whether changes in SRB can be explained by observable macro-level socioeconomic variables across multiple years and countries. Here we show that changes in disposable income at the macro level positively predict SRB in OECD countries. A one standard deviation increase in the change of disposable income is associated with an increase of 1.03 male births per 1000 female births. The relationship is possibly nonlinear and driven by extreme changes. The association varies from country to country being particular strong in Estonia. This is the first evidence to show that economic and social conditions are connected to SRB across countries at the macro level. This calls for further research on the effects of societal conditions on general characteristics at birth.

  16. Evidence of the genetic trend for secondary sex ratio in Iranian Holsteins.

    PubMed

    Ghavi Hossein-Zadeh, Navid

    2012-01-01

    Calving records from the Animal Breeding Center of Iran collected from January 2000 to December 2007 and comprising 520964 Holstein calving events from 2135 herds were analysed using animal and sire models to estimate variance components, heritabilities and genetic trends for secondary sex ratio (SSR) in the first, second and third parities. Direct heritabilities for SSR ranged from 0.00004 to 0.001 over the parities. The linear sire model estimate of heritabilities for SSR in the present study was from 0.0002 to 0.0008 over the parities. There were positive phenotypic and genetic trends for female rate in Iranian Holsteins over the years. Exploitable genetic variation in SSR can take advantage of sexual dimorphism for economically important traits, which may facilitate greater selection intensity and thus greater response to selection, as well as reducing the replacement costs. On the other hand, increasing genetic and phenotypic trends for female rate in the population under study could be partly assigned to increased use of new reproductive technologies in dairy herds; therefore, dairy farmers have the option to select from among their herd's potential dams and produce dairy replacement heifers from only the genetically superior animals, thus promoting enhanced rates of genetic gain.

  17. Changes in Income at Macro Level Predict Sex Ratio at Birth in OECD Countries

    PubMed Central

    2016-01-01

    The human sex ratio at birth (SRB) is approximately 107 boys for every 100 girls. SRB was rising until the World War II and has been declining slightly after the 1950s in several industrial countries. Recent studies have shown that SRB varies according to exposure to disasters and socioeconomic conditions. However, it remains unknown whether changes in SRB can be explained by observable macro-level socioeconomic variables across multiple years and countries. Here we show that changes in disposable income at the macro level positively predict SRB in OECD countries. A one standard deviation increase in the change of disposable income is associated with an increase of 1.03 male births per 1000 female births. The relationship is possibly nonlinear and driven by extreme changes. The association varies from country to country being particular strong in Estonia. This is the first evidence to show that economic and social conditions are connected to SRB across countries at the macro level. This calls for further research on the effects of societal conditions on general characteristics at birth. PMID:27437701

  18. Reducing the noise in behavioral assays: sex and age in adult zebrafish locomotion.

    PubMed

    Philpott, Catelyn; Donack, Corey J; Cousin, Margot A; Pierret, Chris

    2012-12-01

    Many assays are used in animal model systems to measure specific human disease-related behaviors. The use of both adult and larval zebrafish as a behavioral model is gaining popularity. As this work progresses and potentially translates into new treatments, we must do our best to improve the sensitivity of these assays by reducing confounding factors. Scientists who use the mouse model system have demonstrated that sex and age can influence a number of behaviors. As a community, they have moved to report the age and sex of all animals used in their studies. Zebrafish work does not yet carry the same mandate. In this study, we evaluated sex and age differences in locomotion behavior. We found that age was a significant factor in locomotion, as was sex within a given age group. In short, as zebrafish age, they appear to show less base level locomotion. With regard to sex, younger (10 months) zebrafish showed more locomotion in males, while older zebrafish (22 months) showed more movement in females. These findings have led us to suggest that those using the zebrafish for behavioral studies control for age and sex within their experimental design and report these descriptors in their methods.

  19. Avian sex, sex chromosomes, and dosage compensation in the age of genomics.

    PubMed

    Graves, Jennifer A Marshall

    2014-04-01

    Comparisons of the sex chromosome systems in birds and mammals are widening our view and deepening our understanding of vertebrate sex chromosome organization, function, and evolution. Birds have a very conserved ZW system of sex determination in which males have two copies of a large, gene-rich Z chromosome, and females have a single Z and a female-specific W chromosome. The avian ZW system is quite the reverse of the well-studied mammalian XY chromosome system, and evolved independently from different autosomal blocs. Despite the different gene content of mammal and bird sex chromosomes, there are many parallels. Genes on the bird Z and the mammal X have both undergone selection for male-advantage functions, and there has been amplification of male-advantage genes and accumulation of LINEs. The bird W and mammal Y have both undergone extensive degradation, but some birds retain early stages and some mammals terminal stages of the process, suggesting that the process is more advanced in mammals. Different sex-determining genes, DMRT1 and SRY, define the ZW and XY systems, but DMRT1 is involved in downstream events in mammals. Birds show strong cell autonomous specification of somatic sex differences in ZZ and ZW tissue, but there is growing evidence for direct X chromosome effects on sexual phenotype in mammals. Dosage compensation in birds appears to be phenotypically and molecularly quite different from X inactivation, being partial and gene-specific, but both systems use tools from the same molecular toolbox and there are some signs that galliform birds represent an early stage in the evolution of a coordinated system.

  20. Empathy Mediates the Effects of Age and Sex on Altruistic Moral Decision Making.

    PubMed

    Rosen, Jan B; Brand, Matthias; Kalbe, Elke

    2016-01-01

    Moral decision making involves affective and cognitive functions like emotional empathy, reasoning and cognitive empathy/theory of mind (ToM), which are discussed to be subject to age-related alterations. Additionally, sex differences in moral decision making have been reported. However, age-related changes in moral decision making from early to late adulthood and their relation to sex and neuropsychological functions have not been studied yet. One hundred ninety seven participants (122 female), aged 19-86 years, were tested with a moral decision making task comprising forced choice "everyday life" situations in which an altruistic option that favors a socially accepted alternative had to be considered against an egoistic option that favors personal benefit over social interests. The percentage of altruistic decisions was analyzed. A structural equation model (SEM) was calculated to test the hypothesis whether age and sex predict altruistic moral decision, and whether relevant neuropsychological domains mediate these hypothesized relationships. A significant relationship between age and moral decision making was found indicating more frequent altruistic decisions with increasing age. Furthermore, women decided more altruistically than men. The SEM showed that both age and sex are significant predictors of altruistic moral decision making, mediated by emotional empathy but not by reasoning. No cognitive empathy and ToM scores were correlated to age and moral decision making at the same time and thus were not included in the SEM. Our data suggest that increasing age and female sex have an effect on altruistic moral decisions, but that this effect is fully mediated by emotional empathy. The fact that changes of moral decision making with age are mediated by emotional empathy can be interpreted in the light of the so-called "positivity effect" and increasing avoidance of negative affect in aging. The mediated sex effect might represent both biological aspects and

  1. Empathy Mediates the Effects of Age and Sex on Altruistic Moral Decision Making

    PubMed Central

    Rosen, Jan B.; Brand, Matthias; Kalbe, Elke

    2016-01-01

    Moral decision making involves affective and cognitive functions like emotional empathy, reasoning and cognitive empathy/theory of mind (ToM), which are discussed to be subject to age-related alterations. Additionally, sex differences in moral decision making have been reported. However, age-related changes in moral decision making from early to late adulthood and their relation to sex and neuropsychological functions have not been studied yet. One hundred ninety seven participants (122 female), aged 19–86 years, were tested with a moral decision making task comprising forced choice “everyday life” situations in which an altruistic option that favors a socially accepted alternative had to be considered against an egoistic option that favors personal benefit over social interests. The percentage of altruistic decisions was analyzed. A structural equation model (SEM) was calculated to test the hypothesis whether age and sex predict altruistic moral decision, and whether relevant neuropsychological domains mediate these hypothesized relationships. A significant relationship between age and moral decision making was found indicating more frequent altruistic decisions with increasing age. Furthermore, women decided more altruistically than men. The SEM showed that both age and sex are significant predictors of altruistic moral decision making, mediated by emotional empathy but not by reasoning. No cognitive empathy and ToM scores were correlated to age and moral decision making at the same time and thus were not included in the SEM. Our data suggest that increasing age and female sex have an effect on altruistic moral decisions, but that this effect is fully mediated by emotional empathy. The fact that changes of moral decision making with age are mediated by emotional empathy can be interpreted in the light of the so-called “positivity effect” and increasing avoidance of negative affect in aging. The mediated sex effect might represent both biological aspects

  2. Sex and age distribution in transport-related injuries in Tehran.

    PubMed

    Roudsari, Bahman Sayyar; Sharzei, Kaveh; Zargar, Moosa

    2004-05-01

    Intercountry or regional differences in patterns of injury by the road user type have significant implication for prevention policies. In order to have an estimate from the existing conditions of transport-related injuries (TRIs) and especially to evaluate sex and age distribution of traffic accident victims, we analyzed information of 8426 hospitalized trauma patients during 13 months of data gathering process. Forty-five percent of the injuries were related to car accidents and men/women ratio in these patients was 4.2/1. The highest men/women ratio was (16/1) for motorcyclists, while the lowest ratio (1/1), was for rear seat car passengers. Mean (+/-S.D.) age of the patients was 31 (+/-18), and men were nearly 2 years younger than women (33 versus 31). Sixty-seven percent of the females' and 44% of the males' injuries were related to pedestrian crashes. Motorcycle-related injuries in men and car passenger related injuries in women were the second most common type of crash (42 and 22%, respectively). The use of protective devices in our population was worrisome. In only 6% of the male motorcyclists helmet use was reported, and 3% of the male car occupants had used seatbelts at the time of the accident. The condition in the female population was much worse and no use of the protective devices was reported in this group of the patients. Crude mortality rate in men was nearly two times that of women (6.2% versus 3.8%). After adjustment for age, injury severity score (ISS) and category of the road users, men and women had similar mortality rate.

  3. Variation in body condition indices of crimson finches by sex, breeding stage, age, time of day, and year

    PubMed Central

    Milenkaya, Olga; Weinstein, Nicole; Legge, Sarah; Walters, Jeffrey R.

    2013-01-01

    Body condition indices are increasingly applied in conservation to assess habitat quality, identify stressed populations before they decline, determine effects of disturbances, and understand mechanisms of declines. To employ condition indices in this manner, we need first to understand their baseline variability and sources of variation. Here, we used crimson finches (Neochmia phaeton), a tropical passerine, to describe the variation in seven commonly used condition indices by sex, age, breeding stage, time of day, and year. We found that packed cell volume, haemoglobin, total plasma protein, and scaled mass were all significantly affected by an interaction between sex and breeding stage. Furcular fat varied by sex and breeding stage and also trended by year, scaled mass showed a positive trend with age and varied by time of day, and haemoglobin additionally varied by year. Pectoral muscle scores varied and heterophil to lymphocyte ratio trended only by year. Year effects might reflect a response to annual variation in environmental conditions; therefore, those indices showing year effects may be especially worthy of further investigation of their potential for conservation applications. Pectoral muscle scores and heterophil to lymphocyte ratio may be particularly useful due to the lack of influence of other variables on them. For the other indices, the large variation that can be attributed to individual covariates, such as sex and breeding stage, suggests that one should not interpret the physiological condition of an individual as measured by these indices from their absolute value. Instead, the condition of an individual should be interpreted relative to conspecifics by sex, breeding stage, and possibly age. PMID:27293604

  4. Effect of sex, age, and breed on genetic recombination features in cattle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Meiotic recombination is a fundamental biological process which generates genetic diversity, affects fertility, and influences evolvability. Here we investigate the roles of sex, age, and breed in cattle recombination features, including recombination rate, location and crossover interference. Usin...

  5. The role of city income inequality, sex ratio and youth mortality rates in the effect of violent victimization on health-risk behaviors in Brazilian adolescents.

    PubMed

    Ramos, Dandara de Oliveira; Daly, Martin; Seidl-de-Moura, Maria Lucia; Nadanovsky, Paulo

    2017-03-27

    This study integrates insights from evolutionary psychology and social epidemiology to present a novel approach to contextual effects on health-risk behaviors (unprotected sex, drunkenness episodes, drugs and tobacco experimentation) among adolescents. Using data from the 2012 Brazilian National Survey of Adolescent Health (PeNSE), we first analyzed the effects of self-reported violent victimization on health-risk behaviors of 47,371 adolescents aged 10-19 nested in the 26 Brazilian state capitals and the Federal District. We then explored whether the magnitude of these associations was correlated with cues of environmental harshness and unpredictability (youth external mortality and income inequality) and mating competition (sex ratio) from the city level. Results indicated that self-reported violent victimization is associated with an increased chance of engagement in health-risk behaviors in all Brazilian state capitals, for both males and females, but the magnitude of these associations varies in relation to broader environmental factors, such as the cities' age-specific mortality rates, and specifically for females, income inequality and sex ratio. In addition to introducing a novel theoretical and empirical approach to contextual effects on adolescent health-risk behaviors, our findings reinforce the need to consider synergies between people's life experiences and the conditions where they live, when studying health-risk behaviors in adolescence.

  6. Sex differences in pulse pressure trends with age are cross-cultural.

    PubMed

    Skurnick, Joan H; Aladjem, Mordechay; Aviv, Abraham

    2010-01-01

    Sex differences in systolic and diastolic blood pressure levels and trends with age have been consistently observed in both industrialized and unindustrialized populations. However, the impact of sex on pulse pressure, an index of vascular aging, in unindustrialized populations has not been addressed. The objective of this report was to characterize sex differences in aging trends of pulse pressure within unindustrialized populations. Using PubMed and Medline, we identified 60 articles with blood pressure data from unacculturated or partially acculturated populations. Data on 27 populations from 22 articles were included for analysis, on the basis of adequate description of study design and blood pressure measurement. Blood pressure means of adult age groups were modeled by linear and polynomial regression. The pulse pressure levels of women were lower than those of men in early adulthood and higher in older ages. Women had a steeper, steady increase in pulse pressure with age than men (P<0.001), whereas men had a stronger curvilinear upswing in pulse pressure with age (P=0.006). Partially acculturated populations had higher pulse pressures than unacculturated populations. Sex had a stronger effect on pulse pressure than acculturation. Pulse pressure trajectories of unindustrialized populations were slightly attenuated compared with those seen in National Health and Nutritional Examination Surveys III and IV of the US population. A sex effect on pulse pressure trends with age prevails across unacculturated and acculturated populations. Accordingly, the biological principles of arterial aging, as expressed in pulse pressure, are the same in all humans, regardless of demography.

  7. Age and sex differences in paranormal beliefs: a response to Vitulli, Tipton, and Rowe (1999)

    PubMed

    Irwin, H J

    2000-04-01

    Vitulli, Tipton, and Rowe (1999) report evidence of age and sex differences in the strength of paranormal beliefs. An alternative interpretation of their data is offered in terms of differential item functioning. It is suggested that respondents' interpretation of paranormal belief test items may vary with age and sex, and that such differences in the strength with which such beliefs are endorsed has not been conclusively established by Vitulli, et al.

  8. [Antibodies to endogenous bioregulators and their association with age and sex in chronic pain syndrome].

    PubMed

    Myagkova, M A; Petrochenko, S N; Morozova, V S; Moseikin, I A; Shypitsin, V V; Polyvyanaya, O Yu

    2013-01-01

    Authors studied changes in the levels of antibodies to endogenous bioregulators (Ab) to Β-endorphin, orphanin, serotonin, dopamine and angiotensin in 36 healthy people and 109 patients with dorsopathy with chronic pain syndrome. The association of these immunological indicators with age and sex was found. It has been concluded that the levels of Ab to endogenous bioregulators may be considered as a marker of algic system pathology that does not depend on age and is sex-related.

  9. Experimental manipulation of queen number affects colony sex ratio investment in the highly polygynous ant Formica exsecta

    PubMed Central

    Kümmerli, Rolf; Helms, Ken R; Keller, Laurent

    2005-01-01

    In polygynous (multiple queens per nest) ants, queen dispersal is often limited with young queens being recruited within the parental colony. This mode of dispersal leads to local resource competition between nestmate queens and is frequently associated with extremely male-biased sex ratios at the population level. The queen-replenishment hypothesis has been recently proposed to explain colony sex ratio investment under such conditions. It predicts that colonies containing many queens (subject to high local resource competition) should only produce males, whereas colonies hosting few queens (reduced or no local resource competition) should produce new queens in addition to males. We experimentally tested this hypothesis in the ant Formica exsecta by manipulating queen number over three consecutive years in 120 colonies of a highly polygynous population. Queens were transferred from 40 colonies into another 40 colonies while queen number was not manipulated in 40 control colonies. Genetic analyses of worker offspring revealed that our treatment significantly changed the number of reproductive queens. The sex ratio of colonies was significantly different between treatments in the third breeding season following the experiment initiation. We found that, as predicted by the queen-replenishment hypothesis, queen removal resulted in a significant increase in the proportion of colonies that produced new queens. These results provide the first experimental evidence for the queen-replenishment hypothesis, which might account for sex ratio specialization in many highly polygynous ant species. PMID:16096090

  10. Similar estimates of population genetic composition and sex ratio derived from carcasses and faeces of Eurasian otter Lutra lutra.

    PubMed

    Dallas, John F; Coxon, Karen E; Sykes, Tim; Chanin, Paul R F; Marshall, Freda; Carss, David N; Bacon, Philip J; Piertney, Stuart B; Racey, Paul A

    2003-01-01

    Collecting faeces is viewed as a potentially efficient way to sample elusive animals. Nonetheless, any biases in estimates of population composition associated with such sampling remain uncharacterized. The goal of this study was to compare estimates of genetic composition and sex ratio derived from Eurasian otter Lutra lutra spraints (faeces) with estimates derived from carcasses. Twenty per cent of 426 wild-collected spraints from SW England yielded composite genotypes for 7-9 microsatellites and the SRY gene. The expected number of incorrect spraint genotypes was negligible, given the proportions of allele dropout and false allele detection estimated using paired blood and spraint samples of three captive otters. Fifty-two different spraint genotypes were detected and compared with genotypes of 70 otter carcasses from the same area. Carcass and spraint genotypes did not differ significantly in mean number of alleles, mean unbiased heterozygosity or sex ratio, although statistical power to detect all but large differences in sex ratio was low. The genetic compositions of carcass and spraint genotypes were very similar according to confidence intervals of theta and two methods for assigning composite genotypes to groups. A distinct group of approximately 11 carcass and spraint genotypes was detected using the latter methods. The results suggest that spraints can yield unbiased estimates of population genetic composition and sex ratio.

  11. Polymorphism for Y-Linked Suppressors of Sex-Ratio in Two Natural Populations of Drosophila Mediopunctata

    PubMed Central

    Carvalho, A. B.; Vaz, S. C.; Klaczko, L. B.

    1997-01-01

    In several Drosophila species there is a trait known as ``sex-ratio'': males carrying certain X chromosomes (called ``SR'') produce female biased progenies due to X-Y meiotic drive. In Drosophila mediopunctata this trait has a variable expression due to Y-linked suppressors of sex-ratio expression, among other factors. There are two types of Y chromosomes (suppressor and nonsuppressor) and two types of SR chromosomes (suppressible and unsuppressible). Sex-ratio expression is suppressed in males with the SR(suppressible)/Y(suppressor) genotype, whereas the remaining three genotypes produce female biased progenies. Now we have found that ~10-20% of the Y chromosomes from two natural populations 1500 km apart are suppressors of sex-ratio expression. Preliminary estimates indicate that Y(suppressor) has a meiotic drive advantage of 6% over Y(nonsuppressor). This Y polymorphism for a nonneutral trait is unexpected under current population genetics theory. We propose that this polymorphism is stabilized by an equilibrium between meiotic drive and natural selection, resulting from interactions in the population dynamics of X and Y alleles. Numerical simulations showed that this mechanism may stabilize nonneutral Y polymorphisms such as we have found in D. mediopunctata. PMID:9215895

  12. Male-biased sex ratio does not promote increased sperm competitiveness in the seed beetle, Callosobruchus maculatus

    PubMed Central

    McNamara, Kathryn B.; Robinson, Stephen P.; Rosa, Márta E.; Sloan, Nadia S.; van Lieshout, Emile; Simmons, Leigh W.

    2016-01-01

    Sperm competition risk and intensity can select for adaptations that increase male fertilisation success. Evolutionary responses are examined typically by generating increased strength of sexual selection via direct manipulation of female mating rates (by enforcing monandry or polyandry) or by alteration of adult sex ratios. Despite being a model species for sexual selection research, the effect of sexual selection intensity via adult sex-ratio manipulation on male investment strategies has not been investigated in the seed beetle, Callosobruchus maculatus. We imposed 32 generations of experimental evolution on 10 populations of beetles by manipulating adult sex ratio. Contrary to predictions, males evolving in male-biased populations did not increase their testes and accessory gland size. This absence of divergence in ejaculate investment was also reflected in the fact that males from male-biased populations were not more successful in either preventing females from remating, or in competing directly for fertilisations. These populations already demonstrate divergence in mating behaviour and immunity, suggesting sufficient generations have passed to allow divergence in physiological and behavioural traits. We propose several explanations for the absence of divergence in sperm competitiveness among our populations and the pitfalls of using sex ratio manipulation to assess evolutionary responses to sexual selection intensity. PMID:27306351

  13. Male-biased sex ratio does not promote increased sperm competitiveness in the seed beetle, Callosobruchus maculatus.

    PubMed

    McNamara, Kathryn B; Robinson, Stephen P; Rosa, Márta E; Sloan, Nadia S; van Lieshout, Emile; Simmons, Leigh W

    2016-06-16

    Sperm competition risk and intensity can select for adaptations that increase male fertilisation success. Evolutionary responses are examined typically by generating increased strength of sexual selection via direct manipulation of female mating rates (by enforcing monandry or polyandry) or by alteration of adult sex ratios. Despite being a model species for sexual selection research, the effect of sexual selection intensity via adult sex-ratio manipulation on male investment strategies has not been investigated in the seed beetle, Callosobruchus maculatus. We imposed 32 generations of experimental evolution on 10 populations of beetles by manipulating adult sex ratio. Contrary to predictions, males evolving in male-biased populations did not increase their testes and accessory gland size. This absence of divergence in ejaculate investment was also reflected in the fact that males from male-biased populations were not more successful in either preventing females from remating, or in competing directly for fertilisations. These populations already demonstrate divergence in mating behaviour and immunity, suggesting sufficient generations have passed to allow divergence in physiological and behavioural traits. We propose several explanations for the absence of divergence in sperm competitiveness among our populations and the pitfalls of using sex ratio manipulation to assess evolutionary responses to sexual selection intensity.

  14. Long-term trends of bloater (Coregonus hoyi) recruitment in Lake Michigan: evidence for the effect of sex ratio

    USGS Publications Warehouse

    Bunnell, David B.; Madenjian, Charles P.; Croley, Thomas E.

    2006-01-01

    Long-term population trends are generally explained by factors extrinsic (e.g., climate, predation) rather than intrinsic (e.g., genetics, maternal effects) to the population. We sought to understand the long-term population dynamics of an important native Lake Michigan prey fish, the bloaterCoregonus hoyi. Over a 38-year time series, three 10- to 15-year phases occurred (poor, excellent, and then poor recruitment) without high interannual variability within a particular phase. We used dynamic linear models to determine whether extrinsic (winter and spring temperature, alewife predator densities) or intrinsic factors (population egg production, adult condition, adult sex ratio) explained variation in recruitment. Models that included population egg production, sex ratio, winter and spring temperature, and adult bloater condition explained the most variation. Of these variables, sex ratio, which ranged from 47% to 97% female across the time series, consistently had the greatest effect: recruitment declined with female predominance. Including biomass of adult alewife predators in the models did not explain additional variation. Overall our results indicated that bloater recruitment is linked to its sex ratio, but understanding the underlying mechanisms will require additional efforts.

  15. Marriage season, promptness of successful pregnancy and first-born sex ratio in a historical natural fertility population - evidence for sex-dependent early pregnancy loss?

    NASA Astrophysics Data System (ADS)

    Nonaka, K.; Desjardins, Bertrand; Charbonneau, Hubert; Légaré, Jacques; Miura, Teiji

    We investigated population-based vital records of the seventeenth and eighteenth century French Canadian population to assess the effects of marriage season on the outcome of the first births under natural fertility conditions (n=21,698 marriages). Promptness of the first successful conception after marriage differed according to marriage season; the proportion of marriages with a marriage-first birth interval of 8.0-10.0 months was lowest (34%) for marriages in August-October (P=0.001). Although the male/female sex ratio of the babies born with an interval of 8.0-10.0 months was generally higher (1.10) than those with an interval of 10.0-24.0 months (1.05), the marriages in August-October resulted in a significantly reduced sex ratio (0.96) among only the prompt conceptions (P=0.026). We discuss whether this seasonal reduction of the sex ratio could be partly explained by a clustered pregnancy loss of male zygotes in early pregnancy.

  16. Sex differences in elite swimming with advanced age are less than marathon running.

    PubMed

    Senefeld, J; Joyner, M J; Stevens, A; Hunter, S K

    2016-01-01

    The sex difference in marathon performance increases with finishing place and age of the runner but whether this occurs among swimmers is unknown. The purpose was to compare sex differences in swimming velocity across world record place (1st-10th), age group (25-89 years), and event distance. We also compared sex differences between freestyle swimming and marathon running. The world's top 10 swimming times of both sexes for World Championship freestyle stroke, backstroke, breaststroke, and butterfly events and the world's top 10 marathon times in 5-year age groups were obtained. Men were faster than women for freestyle (12.4 ± 4.2%), backstroke (12.8 ± 3.0%), and breaststroke (14.5 ± 3.2%), with the greatest sex differences for butterfly (16.7 ± 5.5%). The sex difference in swimming velocity increased across world record place for freestyle (P < 0.001), breaststroke, and butterfly for all age groups and distances (P < 0.001) because of a greater relative drop-off between first and 10th place for women. The sex difference in marathon running increased with the world record place and the sex difference for marathon running was greater than for swimming (P < 0.001). The sex difference in swimming increased with world record place and age, but was less than for marathon running. Collectively, these results suggest more depth in women's swimming than marathon running.

  17. Sex and age differences in mercury distribution and excretion in methylmercury-administered mice

    SciTech Connect

    Hirayama, K.; Yasutake, A.

    1986-01-01

    Sex differences in mercury distribution and excretion after single administration of methylmercury chloride (MMC, 5 mg/kg were studied in mice. A sex difference in urinary mercury excretion was found in sexually mature mice (age of 7 wk) of C57BL/6N and BALB/cA strains. Males showed higher mercury levels in urine than females, though no significant difference was found in fecal mercury levels 24 h post exposure to MMC. The higher urinary excretion rates in males accounted for significant lowering of mercury levels in the brain, liver, and blood, but not in the kidney, which showed higher values. At 5 min, however, the sex difference was found only in the kidney, showing higher levels in males. Changes in mercury distribution with time were studied in C57BL/6N mice. The brain mercury increased in both sexes up to 3 d, and decreased only in males on d 5. Liver and blood mercury decreased with time in both sexes, and these were constantly higher in females than in males. Renal mercury in males decreased to similar levels to females on d 3. The sex differences at various ages were studied with C57BL/6N mice 24 h after dosing. Two-week-old mice did not show significant sex differences in the mercury distribution and excretion, and their urinary mercury levels were much lower as compared to the older mice. Urinary mercury excretion in both sexes increased at 4 wk of age and then decreased at 45 wk of age. At 4, 7, 10, and 45 wk of age, males showed higher urinary mercury levels than females. From these findings, it has been suggested that urinary mercury excretion may be related to sex hormones, especially androgens.

  18. Age and sex differences in hospitalisation of nursing home residents: a systematic review

    PubMed Central

    Hoffmann, Falk; Allers, Katharina

    2016-01-01

    Objectives Nursing home residents (NHRs) are frequently suffering from multimorbidity, functional and cognitive impairment, often leading to hospital admissions. Studies have found that male NHRs are more often hospitalised. The influence of age is inconclusive. We aimed to investigate the epidemiology of hospitalisations in NHRs, particularly focusing on age-specific and sex-specific differences. Design A systematic review was performed in PubMed, CINAHL and Scopus. Quality of studies was assessed. Setting Studies conducted in nursing homes were included. Participants Nursing home residents. Primary and secondary outcomes Outcome measures were the prevalence, incidence or duration of all-cause hospitalisation by age or sex. Results We identified 21 studies, 13 were conducted in the USA. The proportion of residents being hospitalised ranged across studies from 6.8% to 45.7% for various time periods of follow-up. A total of 20 studies assessed the influence of sex and found that hospitalisations are more often in male NHRs. A total of 16 studies conducted multivariate analyses and the OR of hospitalisation for males was between 1.22 and 1.67. Overall, 18 studies assessed the influence of age. Some studies showed an increasing proportion of admissions with increasing age, but several studies also found decreasing hospitalisations above the age of about 80–85 years. 8 of 13 studies conducting multivariate analyses included age as a continuous variable. Only 1 study reported stratified analyses by age and sex. 2 studies investigating primary causes of hospitalisation stratified by sex found some differences in main diagnoses. Discussion Male NHRs are more often hospitalised than females, but reasons for that are not well investigated. The influence of age is less clear, but there seems to be no clear linear relationship between age and the proportion being hospitalised. Further studies should investigate age and sex differences in frequencies and reasons for

  19. Sex- and age-related variations of the somatotype in a Chuvasha population.

    PubMed

    Kalichman, L; Kobyliansky, E

    2006-01-01

    The aim of this large, cross-sectional study was to describe the age- and sex-related variations of the somatotype, employing Heath and Carter's method, in a Chuvasha population residing in a rural region in central Russia. The investigated sample included 802 males aged 18-89 years (mean 46.9) and 738 females aged 18-90 years (mean 48.6). We evaluated the age and sex differences by one-way ANOVA with somatotype components as dependent variables and sex or age groups as grouping variables. Sex differences of somatotypes appear to be the strongest for endomorphy, with generally higher values in women. Endomorphy in males remained virtually unchanged after 30 years of age, but endomorphy in females kept increasing up to the 6th decade, and then subsequently decreased. Virtually no differences were noted in mesomorphy and a very small difference in ectomorphy between males and females aged 18-30 years. A reduction of sexual dimorphism in all somatotype components after age 70 was also observed. The largest difference of all somatotype components appeared between age groups 18-30 and 31-40 years. Thereafter, somatotypes remained practically unchanged. Mesomorphy continued to increase until the 5th decade in both sexes, while in females, endomorphy continuously increased until their 6th decade. In the 7th and 8th decades, a decrease in mean values was observed. Mesomorphy and ectomorphy showed opposite age-related trends. Results of our study clearly suggest that in physique investigations, the somatotypes need to be studied in each sex separately, and in studies of young people, they need also to be adjusted to age.

  20. Reproduction regulates Drosophila nutrient intake through independent effects of egg production and sex peptide: Implications for aging

    PubMed Central

    Bowman, Elizabeth; Tatar, Marc

    2016-01-01

    BACKGROUND: The ratio of protein to carbohydrate (P:C) consumed influences reproduction and lifespan, outcomes that are often maximized by different P:C intake. OBJECTIVE: Determine if reproduction in female Drosophila drives elevated P:C intake. Distinguish whether such a preference is driven by egg production or from male-derived sex peptides in seminal fluid. METHODS: Intake of protein and carbohydrate was measured in a diet-choice assay. Macronutrient intake was calculated for mated and unmated fertile females, mated and unmated sterile females, and both types of female when mated to wildtype males and to males lacking sex peptide. RESULTS: Mated females have high P:C intake relative to unmated females and mated, sterile females. Fertile females mated to wildtype males and to males lacking sex peptide have high P:C intake, but sterile females have similar, low P:C intake when unmated and when mated to males lacking sex peptide. CONCLUSIONS: The metabolic demands of egg production and sex peptides are individually sufficient to drive elevated P:C intake in adult female Drosophila. Reproductive state can thus modulate how animals consume macronutrients, which in turn can impact their health and aging. PMID:28035342

  1. Differences in the prognosis of early gastric cancer according to sex and age

    PubMed Central

    Suh, Do Dam; Oh, Seong Tae; Yook, Jeong Hwan; Kim, Byung-Sik; Kim, Beom Su

    2016-01-01

    Background: Few studies have compared early gastric cancer (EGC) outcomes according to sex and age. Methods: We retrospectively reviewed 2085 patients who underwent curative gastrectomy for EGC between 1989 and 2000. Prognosis and risk factors for nodal involvement were evaluated according to sex and age. Results: Male sex and age were independent prognostic factors for overall survival (OS) but not relapse-free survival (RFS). In young (⩽55 years) patients, there were no significant differences in RFS and OS between men and women. However, older (>55 years) men had a poorer OS and older women had a poorer RFS. Young female patients had a higher proportion of gastric cancer-related death than young male patients. Female sex was an independent risk factor for nodal involvement in younger patients. Conclusions: Young women with EGC should be more intensively treated and monitored than other patient groups and should not be treated by endoscopic resection. PMID:28203280

  2. Superparasitism Drives Heritable Symbiont Epidemiology and Host Sex Ratio in a Wasp

    PubMed Central

    Parratt, Steven R.; Frost, Crystal L.; Schenkel, Martijn A.; Rice, Annabel

    2016-01-01

    Heritable microbial symbionts have profound impacts upon the biology of their arthropod hosts. Whilst our current understanding of the dynamics of these symbionts is typically cast within a framework of vertical transmission only, horizontal transmission has been observed in a number of cases. For instance, several symbionts can transmit horizontally when their parasitoid hosts share oviposition patches with uninfected conspecifics, a phenomenon called superparasitism. Despite this, horizontal transmission, and the host contact structures that facilitates it, have not been considered in heritable symbiont epidemiology. Here, we tested for the importance of host contact, and resulting horizontal transmission, for the epidemiology of a male-killing heritable symbiont (Arsenophonus nasoniae) in parasitoid wasp hosts. We observed that host contact through superparasitism is necessary for this symbiont’s spread in populations of its primary host Nasonia vitripennis, such that when superparasitism rates are high, A. nasoniae almost reaches fixation, causes highly female biased population sex ratios and consequently causes local host extinction. We further tested if natural interspecific variation in superparasitism behaviours predicted symbiont dynamics among parasitoid species. We found that A. nasoniae was maintained in laboratory populations of a closely related set of Nasonia species, but declined in other, more distantly related pteromalid hosts. The natural proclivity of a species to superparasitise was the primary factor determining symbiont persistence. Our results thus indicate that host contact behaviour is a key factor for heritable microbe dynamics when horizontal transmission is possible, and that ‘reproductive parasite’ phenotypes, such as male-killing, may be of secondary importance in the dynamics of such symbiont infections. PMID:27322651

  3. CHANGES IN SEX RATIO AT BIRTH IN CHINA: A DECOMPOSITION BY BIRTH ORDER.

    PubMed

    Jiang, Quanbao; Yu, Qun; Yang, Shucai; Sánchez-Barricarte, Jesús J

    2016-11-11

    The long-term high sex ratio at birth (SRB) is a serious issue in China. In this study, changes in SRB were decomposed into variations in SRB by birth order and compositional changes in female births by birth order. With SRB data from China's surveys and censuses, and SRB data from South Korea's vital registration and censuses from 1980-2015, the trend and decomposition results in SRB were compared between China and South Korea, and the decomposition results for urban and rural SRBs, and for provinces, are presented. In both China and South Korea the rise in the SRB was driven by a rise in the SRB at all birth orders, which was only partly counteracted by the change in the distribution of births by order. The overall rise in the SRB ended when there was a decline in the SRB at second birth or above in South Korea. In China the total effect of variations in SRB of all birth orders increased more for the rural population than for the urban population before 2000, resulting in a higher total SRB for rural than urban population. After 2000, the total effect of variations in SRB of all birth orders lowered the total SRB for the rural population, whereas the effect of compositional change increased the total SRB, leading to a very slight rise in the total SRB for the rural population. At the province level, there was no spatial autocorrelation for the changes in total SRB by province, the total effect of variations in SRB of all birth orders or the effect of compositional change. The effect of variations in SRB by birth order accounted for the majority of changes in total SRB in most provinces.

  4. Behavioral tactics of male sockeye salmon (Oncorhynchus nerka) under varying operating sex ratios

    USGS Publications Warehouse

    Quinn, Thomas P; Adkison, Milo D.; Ward, Michael B.

    1996-01-01

    Previous studies have demonstrated several reproductive-behavior patterns in male salmon, including competitive and sneaking tactics, the formation of hierarchies, and non-hierarchical aggregations around ripe females. Through behavioral observations at varying spatial and temporal scales, we examined the hypothesis that operational sex ratio (OSR) determines male sockeye salmon (Oncorhynchus nerka) distribution and breeding tactics. Patterns of male distribution and behavior varied over both coarse and fine scales, associated with apparent shifts in reproductive opportunities, the physical characteristics of the breeding sites, and the deterioration of the fish as they approached death. Females spawned completely within a few days of arriving on the spawning grounds, whereas males courted the available ripe females from the date of their arrival on the spawning ground until their death. This difference in reproductive lifespans tended to elevate late-season OSRs but was partially counterbalanced by male departures and the arrival of other ripe females. The proportion of males able to dominate access to ripe females decreased and the number of large courting groups increased over the course of the season, apparently related to both increasing OSR and the deteriorating physical condition of males. However, great variation in OSR was observed within the spawning sites on a given day. OSRs were generally higher in shallow than in deep water, perhaps because larger females or more desirable breeding sites were concentrated in shallow water. The aggregations of males courting females were not stable (i.e. many arrivals and departures took place) and male aggression varied with group size. Aggression was most frequent at low OSRs and in groups of intermediate size (2–4 males per female), and much less frequent in larger groups, consistent with the needs of maximizing reproductive opportunities while minimizing unproductive energy expenditure. These results indicate

  5. Effects of the Great East Japan Earthquake on Secondary Sex Ratio and Perinatal Outcomes

    PubMed Central

    Suzuki, Kohta; Yamagata, Zentaro; Kawado, Miyuki; Hashimoto, Shuji

    2016-01-01

    Background The effect of natural disasters on secondary sex ratio (SSR) and perinatal outcomes has been suggested. This study aimed to examine effects of the Great East Japan Earthquake on perinatal outcomes using vital statistics of J