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1

Thyroid Histopathology Assessments for the Amphibian Metamorphosis Assay to Detect Thyroid-active Substances  

EPA Science Inventory

In support of an Organization for Economic Cooperation and Development (OECD) Amphibian Metamorphosis Assay (AMA) Test Guideline for the detection of substances that interact with the hypothalamic-pituitary-thyroid axis, a document was developed that provides a standardized appro...

2

Thyroid Hormone-disrupting Effects and the Amphibian Metamorphosis Assay  

PubMed Central

There are continued concerns about endocrine-disrupting chemical effects, and appropriate vertebrate models for assessment of risk are a high priority. Frog tadpoles are very sensitive to environmental substances because of their habitat and the complex processes of metamorphosis regulated by the endocrine system, mainly thyroid hormones. During metamorphosis, marked alteration in hormonal factors occurs, as well as dramatic structural and functional changes in larval tissues. There are a variety of mechanisms determining thyroid hormone balance or disruption directly or indirectly. Direct-acting agents can cause changes in thyroxine synthesis and/or secretion in thyroid through effects on peroxidases, thyroidal iodide uptake, deiodinase, and proteolysis. At the same time, indirect action may result from biochemical processes such as sulfation, deiodination and glucuronidation. Because their potential to disrupt thyroid hormones has been identified as an important consideration for the regulation of chemicals, the OECD and the EPA have each established guidelines that make use of larval African clawed frogs (Xenopus laevis) and frog metamorphosis for screening and testing of potential endocrine disrupters. The guidelines are based on evaluation of alteration in the hypothalamic-pituitary-thyroid axis. One of the primary endpoints is thyroid gland histopathology. Others are mortality, developmental stage, hind limb length, snout-vent length and wet body weight. Regarding histopathological features, the guidelines include core criteria and additional qualitative parameters along with grading. Taking into account the difficulties in evaluating amphibian thyroid glands, which change continuously throughout metamorphosis, histopathological examination has been shown to be a very sensitive approach.

Miyata, Kaori; Ose, Keiko

2012-01-01

3

Challenges and approaches to conducting and interpreting the amphibian metamorphosis assay and the fish short-term reproduction assay.  

PubMed

The amphibian metamorphosis assay (AMA) and the fish short-term reproduction assay (FSTRA) are screening assays designed to detect potential endocrine activity of a test substance. These assays are included in a battery of assays in Tier 1 of U.S. Environmental Protection Agency's Endocrine Disruptor Screening Program. Based on our laboratory's experience with these two assays, we have noted several challenges in the conduct and interpretation of the AMA and FSTRA, including, but not limited to, diseased/parasitized test organisms, failure to meet some guideline performance criteria, and issues selecting and maintaining test concentrations. Various approaches are described for addressing the challenges associated with both the conduct and interpretation of these assays. Historical control data for both the AMA and FSTRA are presented to further understand background occurrences of histopathological phenomena and variability associated with the measured endpoints in these assays. In the historical control database for the AMA, wet weight on day 7 was the most variable endpoint (coefficient of variation = 26%), while developmental stage on day 21 was least variable (coefficient of variation = 0.47%). In the FSTRA, vitellogenin concentrations were the most variable endpoint (coefficient of variation = 47-84%), while fertility was the least variable endpoint (coefficient of variation = 1.5%) among historical controls. PMID:24382780

Coady, Katherine Kemler; Lehman, Christine Marie; Currie, Rebecca J; Marino, Troy Alan

2014-02-01

4

Evaluation of the amphibian metamorphosis assay: exposure to the goitrogen methimazole and the endogenous thyroid hormone L-thyroxine.  

PubMed

The U.S. Environmental Protection Agency (U.S. EPA) has included an amphibian metamorphosis assay (AMA) to detect thyroid active chemicals in Tier 1 testing of their endocrine screening program. To understand the variability, specificity, and reliability of the key endpoints of this assay, two exposure studies with Xenopus laevis tadpoles were conducted with two known thyroid-active compounds, namely, methimazole or L-thyroxine, for a total of 21 d. In addition, various increased-flow-rate treatments were included in the exposures to evaluate the effects of physical stress on metamorphic development. The endpoints examined in the exposures were wet weight, snout-vent length, hind-limb length, developmental stage, and thyroid and gonadal histopathology. As expected, the results indicated that both methimazole and L-thyroxine were thyroid active in the AMA, hind-limb length and thyroid histopathology being the most sensitive endpoints of thyroid activity. Tadpoles that were exposed to the various physical stressors in these experiments showed no signs of altered metamorphic development, and exposure to the thyroid-active compounds had no effect on the developing gonad of X. laevis. Taken together, these results support the use of the AMA as a Tier 1 endocrine screen for detection of potential thyroid pathway activity; however, the lack of a true negative response (no-effect) during the validation process prevents a full evaluation of this assay's specificity at this time. PMID:20821516

Coady, Katherine; Marino, Troy; Thomas, Johnson; Currie, Rebecca; Hancock, Gregg; Crofoot, Jackie; McNalley, Lindsay; McFadden, Lisa; Geter, David; Klecka, Gary

2010-04-01

5

Amphibian Metamorphosis: A Sensitive Life Stage to Chemical and Non-chemical Stressors  

EPA Science Inventory

Amphibian metamorphosis is a dynamic period of post-embryonic development which transforms the larval anuran into the juvenile. The body structure is remodeled through a variety of processes which may be perturbed by exposure to chemicals as well as other environmental stressors....

6

Amphibian lipid levels at metamorphosis correlate to post-metamorphic terrestrial survival  

Microsoft Academic Search

In organisms that have complex life cycles, factors in the larval environment may affect both larval and adult traits. For\\u000a amphibians, the postmetamorphic transition from the aquatic environment to terrestrial habitat may be a period of high juvenile\\u000a mortality. We hypothesized that lipid stores at metamorphosis may affect an animal’s success during this critical transition\\u000a period. We examined variation in

David E. Scott; Erin D. Casey; Michele F. Donovan; Tracy K. Lynch

2007-01-01

7

Metamorphosis  

NSDL National Science Digital Library

This illustrated guide is designed to help students understand and learn the difference between simple and complete metamorphosis. The Web page, which can be easily printed for use at field sites, illustrates: complete metamorphosis for lepidoptera (butterflies and moths), simple metamorphosis for thysanura (silverfish) and simple metamorphosis for heteroptera (true bugs.)

8

DEVELOPMENT OF AN AMPHIBIAN METAMORPHOSIS MODEL FOR DETECTING THYROID AXIS DISRUPTION  

EPA Science Inventory

Metamorphosis in Xenopus laevis represents an elaborate process of post-embryonic development which is thyroid hormone (TH) dependent. The development of a functional thyroid axis and the responses of tissues to different TH concentrations are well defined in this species, provid...

9

The evolution of amphibian metamorphosis: insights based on the transformation of the aortic arches of Pelobates fuscus (Anura)  

PubMed Central

In order to gain insights into how the aortic arches changed during the transition of vertebrates to land, transformations of the aortic arches during the metamorphosis of Pelobates fuscus were investigated and compared with data from the early development of a recent ganoid fish Amia calva and a primitive caudate amphibian Salamandrella keyserlingi. Although in larval Pelobates, as in other non-pipid anurans, the gill arches serve partly as a filter-feeding device, their aortic arches maintain the original piscine-like arrangement, except for the mandibular and hyoid aortic arches which were lost. As important pre-adaptations for breathing of atmospheric oxygen occur in larval Pelobates (which have well-developed, though non-respiratory lungs and pulmonary artery), transformation of aortic arches during metamorphosis is fast. The transformation involves disappearance of the ductus Botalli, which results in a complete shunting of blood into the lungs and skin, disappearance of the ductus caroticus, which results in shunting of blood into the head through the arteria carotis interna, and disappearance of arch V, which results in shunting blood to the body through arch IV (systemic arch). It is supposed that the branching pattern of the aortic arches of permanently water-dwelling piscine ancestors, of intermediate forms which occasionally left the water and of primitive tetrapods capable of spending longer periods of time on land had been the same as in the prematamorphic anuran larvae or in some metamorphosed caudates in which the ductus caroticus and ductus Botalli were not interrupted, and arch V was still complete.

Kolesova, Hana; Lametschwandtner, Alois; Rocek, Zbynek

2007-01-01

10

Metamorphosis Matching  

NSDL National Science Digital Library

This is an activity where learners will compare the different metamorphosis stages of amphibians. By matching different life stages of different species, the learners can compare and contrast key characteristics and stages of the life cycle. Learners will match larval stages to adult stages and notice bodily changes in the growth process. This activity can be modified for a slightly more advanced topic.

Aquariums, Association O.

2009-01-01

11

Amphibians.  

ERIC Educational Resources Information Center

Describes some of the characteristics of amphibians. Contains teaching activities ranging from a "frog sing-along" to lessons on amphibian adaptations, and night hikes to identify frog calls. Includes reproducible handouts to be used with the activities, and a quiz. (TW)

Naturescope, 1987

1987-01-01

12

ERYTHROPOIESIS DURING AMPHIBIAN METAMORPHOSIS : III. Immunochemical Detection of Tadpole and Frog Hemoglobins (Rana catesbeiana) in Single Erythrocytes.  

PubMed

Rabbit antibodies specific for the major tadpole and frog hemoglobin components of R. catesbeiana were used for the detection of the two hemoglobins inside single cells. The antisera, after fractionation by ammonium sulfate precipitation and diethylaminoethyl (DEAE)-cellulose chromatography, were conjugated with fluorescein isothiocyanate for the antifrog hemoglobin serum and tetramethylrhodamine isothiocyanate for the antitadpole hemoglobin serum. The conjugated fractions, refractionated by stepwise elution from a DEAE-cellulose column, were used for the fluorescent staining of blood smears, liver tissue imprints, and smears of liver cell suspensions. Both simultaneous and sequential staining with the two fluorescent preparations indicated that larval and adult hemoglobins were not present within the same erythrocyte during metamorphosis. In other experiments, erythroid cells from animals in metamorphosis were spread on agar containing specific antiserum. Precipitates were formed around the cells which contain the particular hemoglobin. The percentages of cells containing either tadpole or frog hemoglobin were estimated within the experimental error of the method. The data showed that the two hemoglobins are in different cells. It is concluded that the hemoglobin change observed during the metamorphosis of R. catesbeiana is due to the appearance of a new population of erythroid cells containing exclusively frog hemoglobin. PMID:19866767

Maniatis, G M; Ingram, V M

1971-05-01

13

Differential patterns of accumulation and retention of dietary trace elements associated with coal ash during larval development and metamorphosis of an amphibian.  

PubMed

We performed an experiment in which larval gray tree frogs (Hyla chrysoscelis) were raised through metamorphosis on diets increased with a suite of elements associated with coal combustion residues (silver [Ag], arsenic [As], cadmium [Cd], chromium [Cr], copper [Cu], mercury [Hg], lead [Pb], selenium [Se], vanadium [V], and zinc [Zn]) at "low" and "high" concentrations. We quantified accumulation of metals at three life stages (mid-larval development, initiation of metamorphosis, and completion of metamorphosis) as well as effects on survival, metabolic rate, size at metamorphosis, and duration and loss of weight during metamorphosis. Most elements were accumulated in a dose-dependent pattern by some or all life stages, although this was not the case for Hg. For most elements, larval body burdens exceeded those of later life stages in some or all treatments (control, low, or high). However for Se, As, and Hg, body burdens in control and low concentrations were increased in later compared with earlier life stages. A lack of dose-dependent accumulation of Hg suggests that the presence of high concentrations of other elements (possibly Se) either inhibited accumulation or increased depuration of Hg. The duration of metamorphosis (forelimb emergence through tail resorption) was lengthened in individuals exposed to the highest concentrations of elements, but there were no other statistically significant biological effects. This study shows that patterns of accumulation and possibly depuration of metals and trace elements are complex in animals possessing complex life cycles. Further study is required to determine specific interactions affecting these patterns, in particular which elements may be responsible for affecting accumulation or retention of Hg when organisms are exposed to complex mixtures of elements. PMID:24169791

Heyes, Andrew; Rowe, Christopher L; Conrad, Phillip

2014-01-01

14

Effects of tributyltin on metamorphosis and gonadal differentiation of Xenopus laevis at environmentally relevant concentrations.  

PubMed

Tributyltin (TBT), a well known endocrine disruptor, has high teratogenicity to embryos of amphibian (Xenopus tropicalis). An amphibian metamorphosis assay (AMA) and a complete AMA (CAMA) were conducted for TBT. In AMA, the body weight, the snout-to-vent length and the hind limb length of X. laevis tadpoles were decreased in tributyltin chloride (TBTCl; 12.5-200 ng/L) treatment groups after 7 days exposure. TBT greatly retarded the development of tadpoles, decreased the number of follicle and induced thyroid follicle cell hyperplasia after 19 days exposure. In CAMA, 10 and 100 ng/L TBTCl led to various malformations of gonad, including intersex, segmental aplasia and multiple ovary cavities of X. laevis following exposure from stages 46 to stage 66. The sex ratio was male-biased in TBT treatment groups. These results suggest that TBT delayed the metamorphosis, inhibited the growth of tadpoles and disrupted the gonadal differentiation of X. laevis at environmentally relevant concentrations. PMID:22903176

Shi, Huahong; Zhu, Pan; Guo, Suzhen

2014-05-01

15

Effect of thyroid hormone concentration on the transcriptional response underlying induced metamorphosis in the Mexican axolotl (Ambystoma)  

Microsoft Academic Search

BACKGROUND: Thyroid hormones (TH) induce gene expression programs that orchestrate amphibian metamorphosis. In contrast to anurans, many salamanders do not undergo metamorphosis in nature. However, they can be induced to undergo metamorphosis via exposure to thyroxine (T4). We induced metamorphosis in juvenile Mexican axolotls (Ambystoma mexicanum) using 5 and 50 nM T4, collected epidermal tissue from the head at four

Robert B Page; Stephen R Voss; Amy K Samuels; Jeramiah J Smith; Srikrishna Putta; Christopher K Beachy

2008-01-01

16

Evolution of Life Cycles in Early Amphibians  

NASA Astrophysics Data System (ADS)

Many modern amphibians have biphasic life cycles with aquatic larvae and terrestrial adults. The central questions are how and when this complicated ontogeny was established, and what is known about the lives of amphibians in the Paleozoic. Fossil evidence has accumulated that sheds light on the life histories of early amphibians, the origin of metamorphosis, and the transition to a fully terrestrial existence. The majority of early amphibians were aquatic or amphibious and underwent only gradual ontogenetic changes. Developmental plasticity played a major role in some taxa but was restricted to minor modification of ontogeny. In the Permo-Carboniferous dissorophoids, a condensation of crucial ontogenetic steps into a short phase (metamorphosis) is observed. It is likely that the origin of both metamorphosis and neoteny falls within these taxa. Fossil evidence also reveals the sequence of evolutionary changes: apparently, the ontogenetic change in feeding, not the transition to a terrestrial existence per se, made a drastic metamorphosis necessary.

Schoch, Rainer R.

2009-05-01

17

Environmentally relevant concentrations of ammonium perchlorate inhibit development and metamorphosis in Xenopus laevis.  

PubMed

We determined whether environmentally relevant concentrations of ammonium perchlorate alter development and metamorphosis in Xenopus laevis. Eggs and larvae were exposed to varying concentrations of ammonium perchlorate or control medium for 70 d. Most treatment-related mortality was observed within 5 d after exposure and was due in large part to reduced hatching success. The 5- and 70-d median lethal concentrations (LC50s) were 510 +/- 36 mg ammonium perchlorate/L and 223 +/- 13 mg ammonium perchlorate/L, respectively. Ammonium perchlorate did not cause any concentration-related developmental abnormalities at concentrations below the 70-d LC50. Ammonium perchlorate inhibited metamorphosis in a concentration-dependent manner as evident from effects on forelimb emergence, tail resorption, and hindlimb growth. These effects were observed after exposure to ammonium perchlorate concentrations in the parts-per-billion range, at or below concentrations reported in surface waters contaminated with ammonium perchlorate. Ammonium perchlorate significantly inhibited tail resorption after a 14-d exposure in the U.S. Environmental Protection Agency (U.S. EPA) Endocrine Disruptor Screening and Testing Committee (EDSTAC) Tier I frog metamorphosis assay for thyroid disruption in amphibians. We believe that ammonium perchlorate may pose a threat to normal development and growth in natural amphibian populations. PMID:11833812

Goleman, Wanda L; Urquidi, Lina J; Anderson, Todd A; Smith, Ernest E; Kendall, Ronald J; Carr, James A

2002-02-01

18

Are Fish and Standardized FETAX Assays Protective Enough for Amphibians? A Case Study on Xenopus laevis Larvae Assay with Biologically Active Substances Present in Livestock Wastes  

PubMed Central

Biologically active substances could reach the aquatic compartment when livestock wastes are considered for recycling. Recently, the standardized FETAX assay has been questioned, and some researchers have considered that the risk assessment performed on fish could not be protective enough to cover amphibians. In the present study a Xenopus laevis acute assay was developed in order to compare the sensitivity of larvae relative to fish or FETAX assays; veterinary medicines (ivermectin, oxytetracycline, tetracycline, sulfamethoxazole, and trimethoprim) and essential metals (zinc, copper, manganese, and selenium) that may be found in livestock wastes were used for the larvae exposure. Lethal (LC50) and sublethal effects were estimated. Available data in both, fish and FETAX studies, were in general more protective than values found out in the current study, but not in all cases. Moreover, the presence of nonlethal effects, caused by ivermectin, zinc, and copper, suggested that several physiological mechanisms could be affected. Thus, this kind of effects should be deeply investigated. The results obtained in the present study could expand the information about micropollutants from livestock wastes on amphibians.

Martini, Federica; Tarazona, Jose V.; Pablos, M. Victoria

2012-01-01

19

Are fish and standardized FETAX assays protective enough for amphibians? A case study on Xenopus laevis larvae assay with biologically active substances present in livestock wastes.  

PubMed

Biologically active substances could reach the aquatic compartment when livestock wastes are considered for recycling. Recently, the standardized FETAX assay has been questioned, and some researchers have considered that the risk assessment performed on fish could not be protective enough to cover amphibians. In the present study a Xenopus laevis acute assay was developed in order to compare the sensitivity of larvae relative to fish or FETAX assays; veterinary medicines (ivermectin, oxytetracycline, tetracycline, sulfamethoxazole, and trimethoprim) and essential metals (zinc, copper, manganese, and selenium) that may be found in livestock wastes were used for the larvae exposure. Lethal (LC(50)) and sublethal effects were estimated. Available data in both, fish and FETAX studies, were in general more protective than values found out in the current study, but not in all cases. Moreover, the presence of nonlethal effects, caused by ivermectin, zinc, and copper, suggested that several physiological mechanisms could be affected. Thus, this kind of effects should be deeply investigated. The results obtained in the present study could expand the information about micropollutants from livestock wastes on amphibians. PMID:22629159

Martini, Federica; Tarazona, José V; Pablos, M Victoria

2012-01-01

20

Metamorphosis-related changes in leukocyte profiles of larval bullfrogs ( Rana catesbeiana )  

Microsoft Academic Search

Metamorphosis in amphibians is a fascinating phenomenon that offers physiologists a number of opportunities to study aspects\\u000a of tissue growth and lysis in animals. In larval amphibians, tissues are formed early on during larval growth, then are vastly\\u000a reorganized and broken down during metamorphosis, and the effects of this phenomenon on the relative distribution of white\\u000a blood cells in circulation

Andrew K. Davis

2009-01-01

21

Thyroid Hormone Receptor Genes of Neotenic Amphibians  

Microsoft Academic Search

.   Since thyroid hormones play a pivotal role in amphibian metamorphosis we used PCR to amplify DNA fragments corresponding\\u000a to a portion of the ligand-binding domain of the thyroid hormone receptor (TR) genes in several neotenic amphibians: the obligatory\\u000a neotenic members of the family Proteidea the mudpuppy Necturus maculosus and Proteus anguinus as well as two members of the facultative

Rachid Safi; Agnès Begue; Catherine Hänni; Dominique Stehelin; Jamshed R. Tata; Vincent Laudet

1997-01-01

22

THYROID AXIS INHIBITION IN XENOPUS LAEVIS: DEVELOPMENT OF AN AMPHIBIAN-BASED SCREENING ASSAY  

EPA Science Inventory

In response to the initial EDSTAC recommendations, research was conducted on the development of a Xenopus laevis based tail resorption assay for evaluating thyroid axis disruption. These experiments highlighted key limitations associated with relying on tail resorption as a measu...

23

Sodium arsenite induced changes in survival, growth, metamorphosis and genotoxicity in the Indian cricket frog (Rana limnocharis).  

PubMed

Arsenic contamination of the environment is a matter of great concern. Understanding the effects of arsenic on aquatic life will act as biological early warning system to assess how arsenic could shape the biodiversity in the affected areas. Rapid decline in amphibian population in recent decades is a cause of major concern. Over the years, amphibians have been recognized as excellent bio-indicators of environmental related stress. In the present study, we examined the toxic and genotoxic effects of sodium arsenite in the tadpoles of the Indian cricket frog (Rana limnocharis). Sodium arsenite at different concentrations (0, 50, 100, 200 and 400?gL(-1)) neither induced lethality nor significantly altered body weight at metamorphosis. However, it accelerated the rate of metamorphosis at higher concentrations, reduced body size (snout-vent length) and induced developmental deformities such as loss of limbs. Besides, at concentration ranges between 100 and 400?gL(-1), sodium arsenite induced statistically significant genotoxicity at 24, 48, 72 and 96h of the exposure in a concentration-dependent manner. However, it did not show time effects as the highest frequency was found between 48 and 72h which remained steady subsequently. The genotoxicity was confirmed by comet assay in the whole blood cells. These findings suggest that arsenic at environmentally relevant concentrations has significant sub-lethal effects on R.limnocharis, which may have long-term fitness consequence to the species and may have similar implications in other aquatic life too. PMID:25048924

Singha, Utsab; Pandey, Neelam; Boro, Freeman; Giri, Sarbani; Giri, Anirudha; Biswas, Somava

2014-10-01

24

Monitoring Amphibians  

NSDL National Science Digital Library

In this field study, learners discover how to collect data in the field and how their efforts can help certain animals, specifically, amphibians. The field study allows learners to go into the field, collect data, and share it on Omaha's Henry Doorly Zoo Amphibian Database.

Aquarium, Omaha'S H.

2011-01-01

25

Reptiles, Amphibians, and Salmonella  

MedlinePLUS

... this? Submit Button CDC Features Reptiles, Amphibians, and Salmonella Language: English Español (Spanish) Share Compartir Reptiles, Amphibians, ... aquariums where they live. How do people get Salmonella infections from reptiles and amphibians? Reptiles and amphibians ...

26

DETECTING THYROID COMPOUNDS USING AN ANURAN METAMORPHOSIS MODEL  

EPA Science Inventory

The Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) recommended in its final report to EPA that an amphibian tail resorption assay be implemented as a Tier 1 screening assay......

27

Ontogenetic loss of phenotypic plasticity of age at metamorphosis in tadpoles  

SciTech Connect

Amphibian larvae exhibit phenotypic plasticity in size at metamorphosis and duration of the larval period. I used Pseudacris crucifer tadpoles to test two models for predicting tadpole age and size at metamorphosis under changing environmental conditions. The Wilbur-Collins model states that metamorphosis is initiated as a function of a tadpole's size and relative growth rate, and predicts that changes in growth rate throughout the larval period affect age and size at metamorphosis. An alternative model, the fixed-rate model, states that age at metamorphosis is fixed early in larval life, and subsequent changes in growth rate will have no effect on the length of the larval period. My results confirm that food supplies affect both age and size at metamorphosis, but developmental rates became fixed at approximately Gosner (1960) stages 35-37. Neither model completely predicted these results. I suggest that the generally accepted Wilbur-Collins model is improved by incorporating a point of fixed developmental timing. Growth trajectories predicted from this modified model fit the results of this study better than trajectories based on either of the original models. The results of this study suggests a constraint that limits the simultaneous optimization of age and size at metamorphosis. 32 refs., 5 figs., 1 tab.

Hensley, F.R. (Univ. of Florida, Gainesville, FL (United States))

1993-12-01

28

Bubbles of Metamorphosis  

NASA Astrophysics Data System (ADS)

Metamorphosis presents a puzzling challenge where, triggered by a signal, an organism abruptly transforms its entire shape and form. Here I describe the role of physical fluid dynamic processes during pupal metamorphosis in flies. During early stages of pupation of third instar larvae into adult flies, a physical gas bubble nucleates at a precise temporal and spatial location, as part of the normal developmental program in Diptera. Although its existence has been known for the last 100 years, the origin and control of this ``cavitation'' event has remained completely mysterious. Where does the driving negative pressure for bubble nucleation come from? How is the location of the bubble nucleation site encoded in the pupae? How do molecular processes control such a physical event? What is the role of this bubble during development? Via developing in-vivo imaging techniques, direct bio-physical measurements in live insect pupal structures and physical modeling, here I elucidate the physical mechanism for appearance and disappearance of this bubble and predict the site of nucleation and its exact timing. This new physical insight into the process of metamorphosis also allows us to understand the inherent design of pupal shell architectures in various species of insects.

Prakash, Manu

2011-11-01

29

THYROID AXIS INHIBITION IN XENOPUS LAEVIS: DEVELOPMENT OF AN AMPHIBIAN-BASED SCREENING ASSAY FOR THYROID DISRUPTION  

EPA Science Inventory

In response to the initial EDSTAC recommendations, research was conducted on the development of a Xenopus laevis based tail resorption assay for evaluating thyroid axis disruption. These experiments highlighted key limitations associated with reliance on tail resorption as a meas...

30

Zebrafish puma mutant decouples pigment pattern and somatic metamorphosis.  

PubMed

The genetic and developmental bases for trait expression and variation in adults are largely unknown. One system in which genes and cell behaviors underlying adult traits can be elucidated is the larval-to-adult transformation of zebrafish, Danio rerio. Metamorphosis in this and many other teleost fishes resembles amphibian metamorphosis, as a variety of larval traits (e.g., fins, skin, digestive tract, sensory systems) are remodeled in a coordinated manner to generate the adult form. Among these traits is the pigment pattern, which comprises several neural crest-derived pigment cell classes, including black melanophores, yellow xanthophores, and iridescent iridophores. D. rerio embryos and early larvae exhibit a relatively simple pattern of melanophore stripes, but this pattern is transformed during metamorphosis into the more complex pattern of the adult, consisting of alternating dark (melanophore, iridophore) and light (xanthophore, iridophore) horizontal stripes. While it is clear that some pigment cells differentiate de novo during pigment pattern metamorphosis, the extent to which larval and adult pigment patterns are developmentally independent has not been known. In this study, we show that a subset of embryonic/early larval melanophores persists into adult stages in wild-type fish; thus, larval and adult pigment patterns are not completely independent in this species. We also analyze puma mutant zebrafish, derived from a forward genetic screen to isolate mutations affecting postembryonic development. In puma mutants, a wild-type embryonic/early larval pigment pattern forms, but supernumerary early larval melanophores persist in ectopic locations through juvenile and adult stages. We then show that, although puma mutants undergo a somatic metamorphosis at the same time as wild-type fish, metamorphic melanophores that normally appear during these stages are absent. The puma mutation thus decouples metamorphosis of the pigment pattern from the metamorphosis of many other traits. Nevertheless, puma mutants ultimately recover large numbers of melanophores and exhibit extensive pattern regulation during juvenile development, when the wild-type pigment pattern already would be completed. Finally, we demonstrate that the puma mutant is both temperature-sensitive and growth-sensitive: extremely severe pigment pattern defects result at a high temperature, a high growth rate, or both; whereas a wild-type pigment pattern can be rescued at a low temperature and a low growth rate. Taken together, these results provide new insights into zebrafish pigment pattern metamorphosis and the capacity for pattern regulation when normal patterning mechanisms go awry. PMID:12679100

Parichy, David M; Turner, Jessica M

2003-04-15

31

Amphibian Bioacoustics  

NASA Astrophysics Data System (ADS)

Anuran amphibians (frogs and toads) of most of the 3,500 species that exist today are highly vocal animals. In most frogs, males will spend considerable energy on calling and incur sizeable predation risks and the females’ detection and localization of the calls of conspecific males is often a prerequisite for successful mating. Therefore, acoustic communication is evidently evolutionarily important in the anurans, and their auditory system is probably shaped by the selective pressures associated with production, detection and localization of the communication calls.

Christensen-Dalsgaard, Jakob

32

Life history of amphibians and gravity.  

PubMed

Anurans hold a unique position in vertebrate phylogeny, as they made the major transition from water to land. Through evolution they have acquired fundamental mechanisms to adapt to terrestrial gravity. Such mechanisms are now shared among other terrestrial vertebrates derived from ancestral amphibians. Space research, using amphibians as a model animal, is significant based on the following aspects: (1) Anuran amphibians show drastic changes in their living niche during their metamorphosis. Environments for tadpoles and for terrestrial life of frogs are quite different in terms of gravity and its associated factors. (2) Certain tadpoles, such as Rhacophorus viridis amamiensis, have a transparent abdominal wall. Thus visceral organs and their motion can be observed in these animals in non-invasive manner through their transparent abdominal skin. This feature enables biologists to evaluate the physiological state of these amphibians and study the autonomic control of visceral organs. It is also feasible for space biologists to examine how such autonomic regulation could be altered by microgravity and exposure to the space environment. PMID:15858355

Naitoh, Tomio; Yamashita, Masamichi; Wassersug, Richard J

2004-11-01

33

Comparative acute and chronic sensitivity of fish and amphibians: a critical review of data.  

PubMed

The relative sensitivity of amphibians to chemicals in the environment, including plant protection product active substances, is the subject of ongoing scientific debate. The objective of this study was to compare systematically the relative sensitivity of amphibians and fish to chemicals. Acute and chronic toxicity data were obtained from the U.S. Environmental Protection Agency (U.S. EPA) ECOTOX database and were supplemented with data from the scientific and regulatory literature. The overall outcome is that fish and amphibian toxicity data are highly correlated and that fish are more sensitive (both acute and chronic) than amphibians. In terms of acute sensitivity, amphibians were between 10- and 100-fold more sensitive than fish for only four of 55 chemicals and more than 100-fold more sensitive for only two chemicals. However, a detailed inspection of these cases showed a similar acute sensitivity of fish and amphibians. Chronic toxicity data for fish were available for 52 chemicals. Amphibians were between 10- and 100-fold more sensitive than fish for only two substances (carbaryl and dexamethasone) and greater than 100-fold more sensitive for only a single chemical (sodium perchlorate). The comparison for carbaryl was subsequently determined to be unreliable and that for sodium perchlorate is a potential artifact of the exposure medium. Only a substance such as dexamethasone, which interferes with a specific aspect of amphibian metamorphosis, might not be detected using fish tests. However, several other compounds known to influence amphibian metamorphosis were included in the analysis, and these did not affect amphibians disproportionately. These analyses suggest that additional amphibian testing is not necessary during chemical risk assessment. PMID:23381988

Weltje, Lennart; Simpson, Peter; Gross, Melanie; Crane, Mark; Wheeler, James R

2013-04-01

34

Acid tolerance in amphibians  

SciTech Connect

Studies of amphibian acid tolerance provide information about the potential effects of acid deposition on amphibian communities. Amphibians as a group appear to be relatively acid tolerant, with many species suffering increased mortality only below pH 4. However, amphibians exhibit much intraspecific variation in acid tolerance, and some species are sensitive to even low levels of acidity. Furthermore, nonlethal effects, including depression of growth rates and increases in developmental abnormalities, can occur at higher pH.

Pierce, B.A.

1985-04-01

35

Architecture and Metamorphosis  

PubMed Central

When compared to other conserved housekeeping protein families, such as ribosomal proteins, during the evolution of higher eukaryotes, aminoacyl-tRNA synthetases (aaRSs) show an apparent high propensity to add new sequences, and especially, new domains. The stepwise emergence of those new domains is consistent with their involvement in a broad range of biological functions beyond protein synthesis, and correlates with the increasing biological complexity of higher organisms. The new domains have been extensively characterized based on their evolutionary origins and their sequence, structural and functional features. While some of the domains are uniquely found in aaRSs and may have originated from nucleic acid binding motifs, others are common domain modules mediating protein-protein interactions that play a critical role in the assembly of the multi-synthetase complex (MSC). Interestingly, the MSC has emerged from a miniature complex in yeast, to a large, stable complex in insects to humans. The human MSC consists of 9 aaRSs (LysRS, ArgRS, GlnRS, AspRS, MetRS, IleRS, LeuRS and GluProRS) and 3 scaffold proteins (AIMP1/p43, AIMP2/p38 and AIMP3/p18), and has a molecular weight of 1.5 million Da. The MSC has been proposed to have a functional dualism: both facilitating protein synthesis and serving as a reservoir of non-canonical functions associated with its synthetase and non-synthetase components. Importantly, domain additions and functional expansions are not limited to the components of the MSC and are found in almost all aaRS proteins. From a structural perspective, multi-functionalities are represented by multiple conformational states. In fact, alternative conformations of aaRSs have been generated by various mechanisms from proteolysis to alternative splicing and posttranslational modifications, as well as by disease-causing mutations. Therefore, the metamorphosis between different conformational states is connected to the activation and regulation of the novel functions of aaRSs in higher eukaryotes.

2013-01-01

36

Compromised metamorphosis and thyroid hormone changes in wood frogs (Lithobates sylvaticus) raised on reclaimed wetlands on the Athabasca oil sands.  

PubMed

The wet landscape approach to oil sands tailings reclamation in the Athabasca Oil Sands region involves creating wetlands from fluid tailings in mined-out pits. We measured time to metamorphosis, thyroid hormone status, and detoxification enzyme (EROD) induction in Wood frog (Lithobates sylvaticus) tadpoles raised on reclaimed oil sands wetlands of different ages [young (? 7 yr) vs. old (> 7 yr)] and compared data with tadpoles raised on reference (control) wetlands. Metamorphosis was delayed or never occurred in tadpoles raised in young tailings; those exposed to older tailings developed similarly to those in reference wetlands. Thyroid hormone disruption likely played an important role in the metamorphosis delay as the T3:T4 ratio was lowest in tadpoles raised in young, tailings-affected wetlands. Our findings suggest tailings wetlands become less toxic with age, and that these amphibians will be able to complete their life cycle in tailing wetlands that have sufficiently detoxified with age. PMID:21036440

Hersikorn, Blair D; Smits, Judit E G

2011-02-01

37

Sex determination in amphibians  

Microsoft Academic Search

The heterogametic sex is male in all mammals, whereas it is female in almost all birds. By contrast, there are two heterogametic types (XX\\/XY and ZZ\\/ZW) for genetic sex determination in amphibians. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. Indeed, the

Masahisa Nakamura

2009-01-01

38

Is the amphibian X. laevis WEC a good alternative method to rodent WEC teratogenicity assay? The example of the three triazole derivative fungicides Triadimefon, Tebuconazole, Cyproconazole.  

PubMed

The aim of the present work is the assessment of teratogenic effects of three triazole-derived fungicides (Triadimefon, FON, Tebuconazole, TEBU, Cyproconazole, CYPRO) on rat and Xenopus laevis embryos cultured in vitro. Rat embryos, exposed to FON 31.25-250?M, CYPRO 31.25-62.5?M and to TEBU 62.5-250?M, showed specific malformations (fusions) at the level of the first and second branchial arches, with a concentration-dependent increase of severity of malformative pictures. After immunostaining, the ectomesenchyme has been identified as the target tissue. X. laevis larvae showed, at the same concentrations, specific malformations at the level of cartilaginous element derived from the first and second branchial arch ectomesenchyme. This work indicates the three tested triazoles as teratogenic both in rodents and in amphibian, inducing ectomesenchymal abnormalities, and suggests, at least for this class of molecules, the X. laevis method as adequate alternative model for teratogenic screening. PMID:21601633

Di Renzo, Francesca; Bacchetta, Renato; Bizzo, Andrea; Giavini, Erminio; Menegola, Elena

2011-09-01

39

Interactive effects of competition and predator cues on immune responses of leopard frogs at metamorphosis.  

PubMed

Recent hypotheses suggest that immunosuppression, resulting from altered environmental conditions, may contribute to the increased incidence of amphibian disease around the world. Antimicrobial peptides (AMPs) in amphibian skin are an important innate immune defense against fungal, viral and bacterial pathogens. Their release is tightly coupled with release of the stress hormone noradrenaline (norepinephrine). During metamorphosis, AMPs may constitute the primary immune response in the skin of some species because acquired immune functions are temporarily suppressed in order to prevent autoimmunity against new adult antigens. Suppression of AMPs during this transitional stage may impact disease rates. We exposed leopard frog tadpoles (Lithobates pipiens) to a factorial combination of competitor and caged-predator environments and measured their development, growth and production of hydrophobic skin peptides after metamorphosis. In the absence of predator cues, or if the exposure to predator cues was late in ontogeny, competition caused more than a 250% increase in mass-standardized hydrophobic skin peptides. Predator cues caused a decrease in mass-standardized hydrophobic skin peptides when the exposure was late in ontogeny under low competition, but otherwise had no effect. Liquid chromatography tandem mass spectrometry of the skin peptides showed that they include six AMPs in the brevinin and temporin families and at least three of these peptides are previously uncharacterized. Both of these peptide families have previously been shown to inhibit harmful microbes including Batrachochytrium dendrobatidis, the fungal pathogen associated with global amphibian declines. Our study shows that amphibians may be able to adjust their skin peptide defenses in response to stressors that are experienced early in ontogeny and that these effects extend through an important life-history transition. PMID:24115058

Groner, Maya L; Rollins-Smith, Louise A; Reinert, Laura K; Hempel, John; Bier, Mark E; Relyea, Rick A

2014-02-01

40

Understanding of the impact of chemicals on amphibians: a meta-analytic review  

PubMed Central

Many studies have assessed the impact of different pollutants on amphibians across a variety of experimental venues (laboratory, mesocosm, and enclosure conditions). Past reviews, using vote-counting methods, have described pollution as one of the major threats faced by amphibians. However, vote-counting methods lack strong statistical power, do not permit one to determine the magnitudes of effects, and do not compare responses among predefined groups. To address these challenges, we conducted a meta-analysis of experimental studies that measured the effects of different chemical pollutants (nitrogenous and phosphorous compounds, pesticides, road deicers, heavy metals, and other wastewater contaminants) at environmentally relevant concentrations on amphibian survival, mass, time to hatching, time to metamorphosis, and frequency of abnormalities. The overall effect size of pollutant exposure was a medium decrease in amphibian survival and mass and a large increase in abnormality frequency. This translates to a 14.3% decrease in survival, a 7.5% decrease in mass, and a 535% increase in abnormality frequency across all studies. In contrast, we found no overall effect of pollutants on time to hatching and time to metamorphosis. We also found that effect sizes differed among experimental venues and among types of pollutants, but we only detected weak differences among amphibian families. These results suggest that variation in sensitivity to contaminants is generally independent of phylogeny. Some publication bias (i.e., selective reporting) was detected, but only for mass and the interaction effect size among stressors. We conclude that the overall impact of pollution on amphibians is moderately to largely negative. This implies that pollutants at environmentally relevant concentrations pose an important threat to amphibians and may play a role in their present global decline.

Egea-Serrano, Andres; Relyea, Rick A; Tejedo, Miguel; Torralva, Mar

2012-01-01

41

Vikers Viking Amphibian - biplane  

NASA Technical Reports Server (NTRS)

Vikers Viking Amphibian - biplane: Initially procured in 1921 by the U.S. Navy during their studies of foreign designs, the Vickers Viking IV became NACA 17 during its short period of study at Langley.

1924-01-01

42

AMPHIBIAN POPULATION DYNAMICS  

EPA Science Inventory

Agriculture has contributed to loss of vertebrate biodiversity in many regions, including the U.S. Corn Belt. Amphibian populations, in particular, have experienced widespread and often inexplicable declines, range reductions, and extinctions. However, few attempts have been made...

43

Antiviral Immunity in Amphibians  

PubMed Central

Although a variety of virus species can infect amphibians, diseases caused by ranaviruses ([RVs]; Iridoviridae) have become prominent, and are a major concern for biodiversity, agriculture and international trade. The relatively recent and rapid increase in prevalence of RV infections, the wide range of host species infected by RVs, the variability in host resistance among population of the same species and among different developmental stages, all suggest an important involvement of the amphibian immune system. Nevertheless, the roles of the immune system in the etiology of viral diseases in amphibians are still poorly investigated. We review here the current knowledge of antiviral immunity in amphibians, focusing on model species such as the frog Xenopus and the salamander (Ambystoma tigrinum), and on recent progress in generating tools to better understand how host immune defenses control RV infections, pathogenicity, and transmission.

Chen, Guangchun; Robert, Jacques

2011-01-01

44

Shallow End For Amphibians  

NSDL National Science Digital Library

This news brief from Nature magazine summarizes a recent paper discussing the combined effects of climate change on declining amphibian populations. Summer climate (detrimental ultraviolet exposure) appears to be linked to spring disease (lethal fungal infections), placing the future of amphibian populations in jeopardy. Several other interactions may also influence survival, such as predator avoidance (higher in low-water pools), which may in turn lead to increased susceptibility of tadpoles to pesticide poisoning.

2001-01-01

45

Metamorphosis  

ERIC Educational Resources Information Center

One thing history's torrent appears to be sweeping away is, ironically, the study of its most productive wellspring, Western civilization. "The Vanishing West", a report the National Association of Scholars released in May 2011, documents the extent of this vanishing. The traditional Western civilization survey requirement, commonplace only…

Balch, Stephen H.

2012-01-01

46

A conceptual model to facilitate amphibian conservation in the northern Great Plains  

USGS Publications Warehouse

As pressures on agricultural landscapes to meet worldwide resource needs increase, amphibian populations face numerous threats including habitat destruction, chemical contaminants, disease outbreaks, wetland sedimentation, and synergistic effects of these perturbations. To facilitate conservation planning, we developed a conceptual model depicting elements critical for amphibian conservation in the northern Great Plains. First, we linked upland, wetland, and landscape features to specific ecological attributes. Ecological attributes included adult survival; reproduction and survival to metamorphosis; and successful dispersal and recolonization. Second, we linked ecosystem drivers, ecosystem stressors, and ecological effects of the region to each ecological attribute. Lastly, we summarized information on these ecological attributes and the drivers, stressors, and effects that work in concert to influence the maintenance of viable and genetically diverse amphibian populations in the northern Great Plains. While our focus was on the northern Great Plains, our conceptual model can be tailored to other geographic regions and taxa.

Mushnet, David M.; Euliss, Ned H., Jr.; Stockwell, Craig A.

2012-01-01

47

Engineering Design Handbook: Wheeled Amphibians.  

National Technical Information Service (NTIS)

This handbook has been prepared as an aid to engineers designing wheeled amphibians. Fundamental design information not readily attainable elsewhere is presented along with requirements and problem areas that are unique to the wheeled amphibian. Part One ...

1971-01-01

48

Chemosensory Stimulation of Molluscan Settlement and Metamorphosis.  

National Technical Information Service (NTIS)

A Settlement and metamorphosis of invertebrate larvae are key points in establishing and maintaining marine communities (including those on the bottoms of ships and piers). This research employed physiological and molecular methods to clarly (1) the basis...

M. G. Hadfield

1996-01-01

49

Amphibian declines: an immunological perspective  

Microsoft Academic Search

Many, but not all, amphibian populations have been declining on all six continents on which they live. Although habitat destruction, direct application of toxicants, and introduction of predators\\/competitors are obvious causes of amphibian declines, many amphibians are dying of infectious diseases in relatively pristine habitats on several continents. In this paper, we review the patterns of these disease outbreaks and

Cynthia Carey; Nicholas Cohen; Louise Rollins-Smith

1999-01-01

50

DEVELOPMENTAL DIVERSITY OF AMPHIBIANS  

PubMed Central

The current model amphibian, Xenopus laevis, develops rapidly in water to a tadpole which metamorphoses into a frog. Many amphibians deviate from the X. laevis developmental pattern. Among other adaptations, their embryos develop in foam nests on land or in pouches on their mother’s back or on a leaf guarded by a parent. The diversity of developmental patterns includes multinucleated oogenesis, lack of RNA localization, huge non-pigmented eggs, and asynchronous, irregular early cleavages. Variations in patterns of gastrulation highlight the modularity of this critical developmental period. Many species have eliminated the larva or tadpole and directly develop to the adult. The wealth of developmental diversity among amphibians coupled with the wealth of mechanistic information from X. laevis permit comparisons that provide deeper insights into developmental processes.

Elinson, Richard P.; del Pino, Eugenia M.

2011-01-01

51

Amphibian Embryology Tutorial  

NSDL National Science Digital Library

Amphibian Embryology Tutorial, originally created to supplement Jeff Hardin's Introduction to Animal Development course at the University of Wisconsin-Madison, is "part of an ongoing project designed to implement multimedia and computer-based learning materials in the university undergraduate classroom." The tutorial is organized by major stages of development: Oogenesis and fertilization, cleavage, gastrulation, and neurulation. The Web site also includes an explanation of why we use amphibians to study development. The tutorial presents detailed explanations of each developmental stage and makes generous use of diagrams, photographs, and movie clips. This Web site would be a terrific resource for students wishing to review amphibian embryology outside the classroom at their own pace.

52

Using bacterial extract along with differential gene expression in Acropora millepora larvae to decouple the processes of attachment and metamorphosis.  

PubMed

Biofilms of the bacterium Pseudoalteromonas induce metamorphosis of acroporid coral larvae. The bacterial metabolite tetrabromopyrrole (TBP), isolated from an extract of Pseudoalteromonas sp. associated with the crustose coralline alga (CCA) Neogoniolithon fosliei, induced coral larval metamorphosis (100%) with little or no attachment (0-2%). To better understand the molecular events and mechanisms underpinning the induction of Acropora millepora larval metamorphosis, including cell proliferation, apoptosis, differentiation, migration, adhesion and biomineralisation, two novel coral gene expression assays were implemented. These involved the use of reverse-transcriptase quantitative PCR (RT-qPCR) and employed 47 genes of interest (GOI), selected based on putative roles in the processes of settlement and metamorphosis. Substantial differences in transcriptomic responses of GOI were detected following incubation of A. millepora larvae with a threshold concentration and 10-fold elevated concentration of TBP-containing extracts of Pseudoalteromonas sp. The notable and relatively abrupt changes of the larval body structure during metamorphosis correlated, at the molecular level, with significant differences (p<0.05) in gene expression profiles of 24 GOI, 12 hours post exposure. Fourteen of those GOI also presented differences in expression (p<0.05) following exposure to the threshold concentration of bacterial TBP-containing extract. The specificity of the bacterial TBP-containing extract to induce the metamorphic stage in A. millepora larvae without attachment, using a robust, low cost, accurate, ecologically relevant and highly reproducible RT-qPCR assay, allowed partially decoupling of the transcriptomic processes of attachment and metamorphosis. The bacterial TBP-containing extract provided a unique opportunity to monitor the regulation of genes exclusively involved in the process of metamorphosis, contrasting previous gene expression studies that utilized cues, such as crustose coralline algae, biofilms or with GLW-amide neuropeptides that stimulate the entire onset of larval metamorphosis and attachment. PMID:22655067

Siboni, Nachshon; Abrego, David; Seneca, Francois; Motti, Cherie A; Andreakis, Nikos; Tebben, Jan; Blackall, Linda L; Harder, Tilmann

2012-01-01

53

Using Bacterial Extract along with Differential Gene Expression in Acropora millepora Larvae to Decouple the Processes of Attachment and Metamorphosis  

PubMed Central

Biofilms of the bacterium Pseudoalteromonas induce metamorphosis of acroporid coral larvae. The bacterial metabolite tetrabromopyrrole (TBP), isolated from an extract of Pseudoalteromonas sp. associated with the crustose coralline alga (CCA) Neogoniolithon fosliei, induced coral larval metamorphosis (100%) with little or no attachment (0–2%). To better understand the molecular events and mechanisms underpinning the induction of Acropora millepora larval metamorphosis, including cell proliferation, apoptosis, differentiation, migration, adhesion and biomineralisation, two novel coral gene expression assays were implemented. These involved the use of reverse-transcriptase quantitative PCR (RT-qPCR) and employed 47 genes of interest (GOI), selected based on putative roles in the processes of settlement and metamorphosis. Substantial differences in transcriptomic responses of GOI were detected following incubation of A. millepora larvae with a threshold concentration and 10-fold elevated concentration of TBP-containing extracts of Pseudoalteromonas sp. The notable and relatively abrupt changes of the larval body structure during metamorphosis correlated, at the molecular level, with significant differences (p<0.05) in gene expression profiles of 24 GOI, 12 hours post exposure. Fourteen of those GOI also presented differences in expression (p<0.05) following exposure to the threshold concentration of bacterial TBP-containing extract. The specificity of the bacterial TBP-containing extract to induce the metamorphic stage in A. millepora larvae without attachment, using a robust, low cost, accurate, ecologically relevant and highly reproducible RT-qPCR assay, allowed partially decoupling of the transcriptomic processes of attachment and metamorphosis. The bacterial TBP-containing extract provided a unique opportunity to monitor the regulation of genes exclusively involved in the process of metamorphosis, contrasting previous gene expression studies that utilized cues, such as crustose coralline algae, biofilms or with GLW-amide neuropeptides that stimulate the entire onset of larval metamorphosis and attachment.

Siboni, Nachshon; Abrego, David; Seneca, Francois; Motti, Cherie A.; Andreakis, Nikos; Tebben, Jan; Blackall, Linda L.; Harder, Tilmann

2012-01-01

54

Amphibians of Olympic National Park  

USGS Publications Warehouse

Amphibians evolved from fishes about 360 million years ago and were the first vertebrates adapted to life on land. The word amphibian means "double life." It refers to the life history of many amphibians, which spend part of their life in water and part on land. There are three major groups of amphibians: salamanders, frogs, and toads, and caecilians. Salamanders, frogs, and toads can be found in Olympic National Park (ONP), but caecilians live only in tropical regions. Many amphibians are generalist predators, eating almost any prey they can fit into their mouths.

U.S. Geological Survey

2000-01-01

55

Effects of hydroperiod duration on survival, developmental rate, and size at metamorphosis in boreal chorus frog tadpoles (Pseudacris maculata)  

USGS Publications Warehouse

Understanding the relationship between climate-driven habitat conditions and survival is key to preserving biodiversity in the face of rapid climate change. Hydroperiod—the length of time water is in a wetland—is a critical limiting habitat variable for amphibians as larvae must metamorphose before ponds dry. Changes in precipitation and temperature patterns are affecting hydroperiod globally, but the impact of these changes on amphibian persistence is poorly understood. We studied the responses of Boreal Chorus Frog (Pseudacris maculata) tadpoles to simulated hydroperiods (i.e., water level reductions) in the laboratory using individuals collected from ponds spanning a range of natural hydroperiods (Colorado Front Range, USA). To assess the effects of experimental hydroperiod reduction, we measured mortality, time to metamorphosis, and size at metamorphosis. We found that tadpoles grew at rates reflecting the hydroperiods of their native ponds, regardless of experimental treatment. Tadpoles from permanent ponds metamorphosed faster than those from ephemeral ponds across all experimental treatments, a pattern which may represent a predation selection gradient or countergradient variation in developmental rates. Size at metamorphosis did not vary across experimental treatments. Mortality was low overall but varied with pond of origin. Our results suggest that adaptation to local hydroperiod and/or predation and temperature conditions is important in P. maculata. Moreover, the lack of a plastic response to reduced hydroperiods suggests that P. maculata may not be able to metamorphose quickly enough to escape drying ponds. These results have important implications for amphibian persistence in ponds predicted to dry more quickly due to rapid climate change.

Amburgey, Staci; Funk, W. Chris; Murphy, Melanie; Muths, Erin

2012-01-01

56

Larval Metamorphosis of Individual Pacific Lampreys Reared in Captivity  

Microsoft Academic Search

This study is one of the first to follow individual Pacific lampreys Lampetra tridentata through the process of metamorphosis. Readily observable external changes were described for 13 individual Pacific lampreys undergoing metamorphosis. Changes occurred to the mouth, eyes, and branchial region from July to at least November. During metamorphosis, Pacific lampreys also exhibited asymmetric growth, including an increase in snout

Michelle McGree; Timothy A. Whitesel; Jen Stone

2008-01-01

57

Amphibian development in microgravity  

NASA Technical Reports Server (NTRS)

The results of experiments performed by the U.S. Biosatellites 1 and 2 and the Gemini VIII and XII missions and by the Soviet Salyut and Soyuz missions on the effect of gravity on the development of prefertilized amphibian egg and, in particular, of the vestibular system of amphibian embryo are described. In these experiments, the condition of microgravity was reached only after the prefertilized eggs were in the early stages of first cell division or in the blastula stage. No significant changes were observed in the morphology of the embryos or in the vestibular system of embyos developed, respectively, for 2-5 days or 20 days under conditions of microgravity. Experiments planned for future spaceflights are discussed.

Souza, K. A.

1987-01-01

58

Field Surveys of Amphibian Populations.  

ERIC Educational Resources Information Center

Describes a course on amphibian research for environmental science majors. Involves students in field studies and introduces them to investigative research. Evaluates the course. (Contains 19 references.) (YDS)

Brodman, Robert

2000-01-01

59

Adult amphibian epidermal proteins: biochemical characterization and developmental appearance.  

PubMed

The keratin-like proteins (KLPs) from the epidermis of adult frogs of the species Xenopus laevis have been isolated and biochemically characterized by means of polyacrylamide gel electrophoresis, amino acid analysis, tryptic peptide mapping, amino-terminal end-group analysis and isoelectric focusing. One particular protein fraction of rather unusual amino acid composition found only in epidermal tissue was isolated in quantity by preparative gel electrophoresis and monospecific antibodies prepared against it. Using this anti-KLP antibody preparation it was possible to show that at least one kine of keratin-like protein characteristic of the adult epidermis first appears within the larval epidermis during metamorphosis. This is the first reported biochemical characterization of a tissue-specific protien from adult amphibian skin. PMID:810539

Reeves, O R

1975-08-01

60

Microcosm investigations of stormwater pond sediment toxicity to embryonic and larval amphibians: variation in sensitivity among species.  

PubMed

Stormwater ponds have become common features of modern development and often represent significant amounts of open space in urbanized areas. Although stormwater ponds may provide habitat for wildlife, factors responsible for producing variation in wildlife use of ponds have received limited attention. To investigate the role of variation in species tolerances of pollutants in structuring pond-breeding amphibian assemblages, we exposed species tolerant (Bufo americanus) and not tolerant (Rana sylvatica) of urbanization to pond sediments in laboratory microcosms. Pond microcosms had elevated sediment metal levels and chloride water concentrations. Among R. sylvatica embryos, exposure to pond sediments resulted in 100% mortality. In contrast, B. americanus embryos and larvae experienced only sublethal effects (i.e., reduced size at metamorphosis) due to pond sediment exposure. Our results suggest variation in pollutant tolerance among early developmental stages of amphibians may act in concert with terrestrial habitat availability to structure amphibian assemblages associated with stormwater ponds. PMID:18023947

Snodgrass, Joel W; Casey, Ryan E; Joseph, Debra; Simon, Judith A

2008-07-01

61

Organizational Metamorphosis in Space Research and Development.  

ERIC Educational Resources Information Center

The communicative, and therefore organizational and managerial, aspects of the Marshall Space Flight Center's (MSFC) metamorphosis from Saturn V to Skylab are analyzed. MSFC's consistent successes are attributed to the organization's commitment to communication systems, its technical integrity, and its single-minded purpose. (JMF)

Tompkins, Phillip K.

1978-01-01

62

Metamorphosis: Play, Spirituality and the Animal  

ERIC Educational Resources Information Center

Animal- and bird-becoming is an aspect of play as metamorphosis connected to spirituality in early childhood settings. The reconceptualisation of play presented here is supported by research that explored the spiritual experiences of young children in different early childhood contexts. Qualitative case study research carried out in Aotearoa New…

Bone, Jane

2010-01-01

63

Making Metamorphosis Meaningful for Young Children  

Microsoft Academic Search

Although butterflies are a common topic of study in many early childhood classrooms, integrating art production broadens the scope of the study and allows children to deepen their knowledge and understanding through creative self-expression. This article presents a set of integrated activities that focus on helping children fully grasp the process of metamorphosis by making observations, asking questions, and using

Rebecca M. Giles; Paige V. Baggett; Edward L. Shaw

2009-01-01

64

Sex determination in amphibians.  

PubMed

The heterogametic sex is male in all mammals, whereas it is female in almost all birds. By contrast, there are two heterogametic types (XX/XY and ZZ/ZW) for genetic sex determination in amphibians. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. Indeed, the frog Rana rugosa has the XX/XY and ZZ/ZW sex-determining systems within a single species, depending on the local population in Japan. The XY and ZW geographic forms with differentiated sex chromosomes probably have a common origin as undifferentiated sex chromosomes resulted from the hybridization between the primary populations of West Japan and Kanto forms. It is clear that the sex chromosomes are still undergoing evolution in this species group. Regardless of the presence of a sex-determining gene in amphibians, the gonadal sex of some species can be changed by sex steroids. Namely, sex steroids can induce the sex reversal, with estrogens inducing the male-to-female sex reversal, whereas androgens have the opposite effect. In R. rugosa, gonadal activity of CYP19 (P450 aromatase) is correlated with the feminization of gonads. Of particular interest is that high levels of CYP19 expression are observed in indifferent gonads at time before sex determination. Increases in the expression of CYP19 in female gonads and CYP17 (P450 17alpha-hydroxylase/C17-20 lyase) in male gonads suggest that the former plays an important role in phenotypic female determination, whereas the latter is needed for male determination. Thus, steroids could be the key factor for sex determination in R. rugosa. In addition to the role of sex steroids in gonadal sex determination in this species, Foxl2 and Sox3 are capable of promoting CYP19 expression. Since both the genes are autosomal, another factor up-regulating CYP19 expression must be recruited. The factor, which may be located on the X or W chromosome, intervenes directly or indirectly, in the transcriptional regulation of the CYP19 gene for feminization in amphibians. A factor up-regulating CYP17 expression remains to be identified. PMID:18996493

Nakamura, Masahisa

2009-05-01

65

Reduced effects of thyroid hormone on gene expression and metamorphosis in a paedomorphic plethodontid salamander.  

PubMed

It has been over a century since Gudernatsch (1912, Wilhelm Roux Arch Entwickl Mech Org 35:457-483) demonstrated that mammalian thyroid gland extracts can stimulate tadpole metamorphosis. Despite the tremendous developmental diversity of amphibians, mechanisms of metamorphosis have mostly been studied in a few model systems. This limits our understanding of the processes that influence the evolution of developmental aberrations. Here we isolated thyroid hormone receptors alpha (TR?) and beta (TR?) from Oklahoma salamanders (Eurycea tynerensis), which exhibit permanently aquatic (paedomorphic) or biphasic (metamorphic) developmental modes in different populations. We found that TR? and TR? were upregulated by thyroid hormone (T3 ) in tail tissues of larvae from metamorphic populations, but basal levels of TR expression and T3 responsiveness were reduced in larvae from paedomorphic populations. Likewise, we found that T3 treatment resulted in complete loss of larval epibranchials in larvae from metamorphic populations, but little to no epibranchial remodeling occurred in larvae from paedomorphic populations over the same duration. This is the first study to directly demonstrate reduced gene expression and metamorphic responses to T3 in a paedomorphic plethodontid compared to metamorphic conspecifics, and the first salamander system to show differential expression of thyroid hormone receptors associated with alternative developmental patterns. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 294-303, 2014. © 2014 Wiley Periodicals, Inc. PMID:24890624

Aran, Robert P; Steffen, Michael A; Martin, Samuel D; Lopez, Olivia I; Bonett, Ronald M

2014-07-01

66

Responses of Mammalian Insectivores, Amphibians, and Reptiles to Broad-Scale Manipulation of Coarse Woody Debris  

SciTech Connect

Sampled shrews at 9.3 ha plots from logs manually removed and control plots in loblolly pine forests of the Southeastern Coastal Plain. Capture rates of Cryptotis parva were lower at plots from which deadwood was removed whereas capture rates of Blarina cavolinensis and Sorex longirostris did not differ between control and removal plots. Cryptotis may have been most sensitive to removal plots due to low population density, hence poor ability to move into areas of low reproduction. (Second Abstract, p. 37)Presentation of evidence that juvenile amphibians including Ambystomatid salamanders may disperse hundreds of meter from their natal wetlands within the weeks to months following metamorphosis. Data indicates Ambystoma trigrinum metamorphs can take at least six months to disperse and en route use non-polar lipid reserves garnished as larvae. Report suggests a land management regime that allows for both juvenile amphibian dispersal and also the consumptive use of the surrounding landscape.

McCay, T.S.; Forschler, B.T.; Komoroski, M.J.; Ford, W.M.

2002-03-10

67

Molecular mechanisms of corticosteroid synergy with thyroid hormone during tadpole metamorphosis  

PubMed Central

Corticosteroids (CS) act synergistically with thyroid hormone (TH) to accelerate amphibian metamorphosis. Earlier studies showed that CS increase nuclear 3,5,3?-triiodothyronine (T3) binding capacity in tadpole tail, and 5? deiodinase activity in tadpole tissues, increasing the generation of T3 from thyroxine (T4). In the present study we investigated CS synergy with TH by analyzing expression of key genes involved in TH and CS signaling using tadpole tail explant cultures, prometamorphic tadpoles, and frog tissue culture cells (XTC-2 and XLT-15). Treatment of tail explants with T3 at 100 nM, but not at 10 nM caused tail regression. Corticosterone (CORT) at three doses (100, 500, 3400 nM) had no effect or increased tail size. T3 at 10 nM plus CORT caused tails to regress similar to 100 nM T3. Thyroid hormone receptor beta (TR?) mRNA was synergistically upregulated by T3 plus CORT in tail explants, tail and brain in vivo, and tissue culture cells. The activating 5? deiodinase type 2 (D2) mRNA was induced by T3 and CORT in tail explants and tail in vivo. Thyroid hormone increased expression of glucocorticoid (GR) and mineralocorticoid receptor (MR) mRNAs. Our findings support that the synergistic actions of TH and CS in metamorphosis occur at the level of expression of genes for TR? and D2, enhancing tissue sensitivity to TH. Concurrently, TH enhances tissue sensitivity to CS by upregulating GR and MR. Environmental stressors can modulate the timing of tadpole metamorphosis in part by CS enhancing the response of tadpole tissues to the actions of TH.

Bonett, Ronald M.; Hoopfer, Eric D.; Denver, Robert J.

2010-01-01

68

Effects of depleted uranium on survival, growth, and metamorphosis in the african clawed frog (Xenopus laevis)  

USGS Publications Warehouse

Embryos (stage 8-47, Nieuwkoop and Faber) of the African clawed frog (Xenopus laevis) were subjected to water-borne depleted uranium (DU) concentrations that ranged from 4.8 to 77.7 mg/Lusing an acute 96-h frog embryo teratogenesis assay-Xenopus (FETAX). In a chronic 64-d assay, X. laevis (from embryo through metamorphosis; stages 8-66) were subjected to concentrations of DU that ranged from 6.2 to 54.3 mg/L Our results indicate DU is a non teratogenic metal. No effects on mortality, malformations, or growth were observed in the 96-h FETAX with concentrations of DU that ranged from 4.8 to 77.7 mg/L From stage 8 to stage 47, X. laevis tadpoles do not actively feed and the gills are not well developed. Thus, uptake of DU was reduced despite exposure to elevated concentrations. The 64-d assay resulted in no concentration response for either mortality or malformations; however, a delay in metamorphosis was observed in tadpoles subjected to elevated DU concentrations (from 13.1 to 54.3 mg/L) compared to tadpoles in both the well-water control and reference. The delay in metamorphosis was likely due to increasing body burden of DU that ranged from 0.98 to 2.82 mg/kg. Copyright?? Taylor & Francis Inc.

Mitchell, S. E.; Caldwell, C. A.; Gonzales, G.; Gould, W. R.; Arimoto, R.

2005-01-01

69

Metamorphosis in the Cirripede Crustacean Balanus amphitrite  

PubMed Central

Stalked and acorn barnacles (Cirripedia Thoracica) have a complex life cycle that includes a free-swimming nauplius larva, a cypris larva and a permanently attached sessile juvenile and adult barnacle. The barnacle cyprid is among the most highly specialized of marine invertebrate larvae and its settlement biology has been intensively studied. By contrast, surprisingly few papers have dealt with the critical series of metamorphic events from cementation of the cyprid to the substratum until the appearance of a suspension feeding juvenile. This metamorphosis is both ontogenetically complex and critical to the survival of the barnacle. Here we use video microscopy to present a timeline and description of morphological events from settled cyprid to juvenile barnacle in the model species Balanus amphitrite, representing an important step towards both a broader understanding of the settlement ecology of this species and a platform for studying the factors that control its metamorphosis. Metamorphosis in B. amphitrite involves a complex sequence of events: cementation, epidermis separation from the cypris cuticle, degeneration of cypris musculature, rotation of the thorax inside the mantle cavity, building of the juvenile musculature, contraction of antennular muscles, raising of the body, shedding of the cypris cuticle, shell plate and basis formation and, possibly, a further moult to become a suspension feeding barnacle. We compare these events with developmental information from other barnacle species and discuss them in the framework of barnacle settlement ecology.

Maruzzo, Diego; Aldred, Nick; Clare, Anthony S.; H?eg, Jens T.

2012-01-01

70

Metapopulation Dynamics and Amphibian Conservation  

Microsoft Academic Search

In many respects, amphibian spatial dynamics resemble classical metapopulation models, in which subpopulations in breeding ponds blink in and out of existence and extinction and colonization rates are functions of pond spatial arrangement. This \\

David M. Marsh; Peter C. Trenham

2001-01-01

71

Field Surveys of Amphibian Populations  

NSDL National Science Digital Library

Amphibian Research, a course offered at Saint Joseph's College in Rensselaer, Indiana, introduces freshmen- and sophomore-level biology and environmental science majors to investigative field research. Students learn to identify species and use standard f

Brodman, Robert

2000-10-01

72

Metamorphosis of a Scleractinian Coral in Response to Microbial Biofilms  

PubMed Central

Microorganisms have been reported to induce settlement and metamorphosis in a wide range of marine invertebrate species. However, the primary cue reported for metamorphosis of coral larvae is calcareous coralline algae (CCA). Herein we report the community structure of developing coral reef biofilms and the potential role they play in triggering the metamorphosis of a scleractinian coral. Two-week-old biofilms induced metamorphosis in less than 10% of larvae, whereas metamorphosis increased significantly on older biofilms, with a maximum of 41% occurring on 8-week-old microbial films. There was a significant influence of depth in 4- and 8-week biofilms, with greater levels of metamorphosis occurring in response to shallow-water communities. Importantly, larvae were found to settle and metamorphose in response to microbial biofilms lacking CCA from both shallow and deep treatments, indicating that microorganisms not associated with CCA may play a significant role in coral metamorphosis. A polyphasic approach consisting of scanning electron microscopy, fluorescence in situ hybridization (FISH), and denaturing gradient gel electrophoresis (DGGE) revealed that coral reef biofilms were comprised of complex bacterial and microalgal communities which were distinct at each depth and time. Principal-component analysis of FISH data showed that the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Cytophaga-Flavobacterium of Bacteroidetes had the largest influence on overall community composition. A low abundance of Archaea was detected in almost all biofilms, providing the first report of Archaea associated with coral reef biofilms. No differences in the relative densities of each subdivision of Proteobacteria were observed between slides that induced larval metamorphosis and those that did not. Comparative cluster analysis of bacterial DGGE patterns also revealed that there were clear age and depth distinctions in biofilm community structure; however, no difference was detected in banding profiles between biofilms which induced larval metamorphosis and those where no metamorphosis occurred. This investigation demonstrates that complex microbial communities can induce coral metamorphosis in the absence of CCA.

Webster, Nicole S.; Smith, Luke D.; Heyward, Andrew J.; Watts, Joy E. M.; Webb, Richard I.; Blackall, Linda L.; Negri, Andrew P.

2004-01-01

73

Variation in the hormonal stress response among larvae of three amphibian species.  

PubMed

In a series of studies, we examined how larval corticosterone treatment for several species of amphibians can impact fitness parameters both during exposure and after metamorphosis. We completed confinement stress series on larvae of three species in natural/semi-natural conditions: wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and Eastern spadefoot toads (Scaphiopus holbrooki). Two of the species had a typical vertebrate response of increasing corticosterone with confinement. However, Eastern spadefoot toads, which have a very short developmental period before metamorphosis, did not show any increase in corticosterone in response to confinement. In a second study, we treated the three species with a low and a high concentration of corticosterone (0.001 and 0.01?µM dissolved in tank water) in the laboratory and examined effects on growth. Although we were successful in raising baseline corticosterone levels with our high corticosterone concentrations, this did not translate into changes in mean larval growth for any of the three species. The larval treatments also did not appear to translate into differences in the juvenile response to confinement stress after metamorphosis. Although juvenile wood frogs did respond to confinement with increasing corticosterone, there was no variation based on larval treatment. As with the larval responses, the juvenile Eastern spadefoot toads did not have a hormonal response to confinement. In summary, while our larval corticosterone exposures did elevate baseline corticosterone levels, we did not see effects of exposure on growth or any latent effects of larval exposure on juvenile responses to confinement. PMID:20878751

Belden, Lisa K; Wingfield, John C; Kiesecker, Joseph M

2010-10-01

74

The Molecular and Endocrine Basis of Flatfish Metamorphosis  

Microsoft Academic Search

A significant component of aquaculture is the production of good quality larvae, and, in the case of flatfish, this is tied up with the change from a symmetric larva to an asymmetric juvenile. Despite the pioneering work carried out on the metamorphosis of the Japanese flounder (Paralichthys olivaceus) and summer flounder (Paralichthys dentatus), the underlying molecular basis of flatfish metamorphosis

Deborah M. Power; Ingibjörg E. Einarsdóttir; Karin Pittman; Glen E. Sweeney; Jon Hildahl; Marco A. Campinho; Nadia Silva; Øystein Sæle; Malyka Galay-Burgos; Heiddís Smáradóttir; Björn Thrandur Björnsson

2008-01-01

75

A First Look at the Second Metamorphosis of Science  

Microsoft Academic Search

During the period of approximately 1570--1790 the first metamorphosis of science transformed the operational foundations of science, that were largely the heritage from the time of Aristotle, into its modern form. These new foundations consisted of the use of (1) Physical Experiments and the use of (2) Mathematical Models, involving differential equations. This metamorphosis was largely due to Brahe, Kepler,

E. Atlee Jackson; Santa Fe

1995-01-01

76

Channel metamorphosis, floodplain disturbance, and vegetation development: Ain River, France  

Microsoft Academic Search

The purpose of this paper is to describe and explain channel metamorphosis of the Ain River in east-central France and the effects of this metamorphosis on floodplain disturbance and vegetation development. The Ain River is a 195 km long stream originating in the Jura Mountains which flows into the Rhône River between Lyon, France, and Geneva, Switzerland. The lower 40

Richard A. Marston; Jacky Girel; Guy Pautou; Herve Piegay; Jean-Paul Bravard; Chris Arneson

1995-01-01

77

Why Does Amphibian Chytrid (Batrachochytrium dendrobatidis) Not Occur Everywhere? An Exploratory Study in Missouri Ponds  

PubMed Central

The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), is a globally emerging pathogen that has caused widespread amphibian population declines, extirpations, and extinctions. However, Bd does not occur in all apparently suitable amphibian populations, even within regions where it is widespread, and it is often unclear why Bd occurs in some habitats but not others. In this study, we rigorously surveyed the amphibian and invertebrate biodiversity of 29 ponds in Missouri, screened resident amphibian larvae (Rana (Lithobates) sp.) for Bd infection, and characterized the aquatic physiochemical environment of each pond (temperature pH, conductivity, nitrogen, phosphorus, and chlorophyll-a). Our goal was to generate hypotheses toward answering the question, “Why does Bd not occur in all apparently suitable habitats?” Bd occurred in assayed amphibians in 11 of the 29 ponds in our study area (38% of ponds). We found no significant relationship between any single biotic or abiotic variable and presence of Bd. However, multivariate analyses (nonmetric multidimensional scaling and permutational tests of dispersion) revealed that ponds in which Bd occurred were a restricted subset of all ponds in terms of amphibian community structure, macroinvertebrate community structure, and pond physiochemistry. In other words, Bd ponds from 6 different conservation areas were more similar to each other than would be expected based on chance. The results of a structural equation model suggest that patterns in the occurrence of Bd among ponds are primarily attributable to variation in macroinvertebrate community structure. When combined with recent results showing that Bd can infect invertebrates as well as amphibians, we suggest that additional research should focus on the role played by non-amphibian biota in determining the presence, prevalence, and pathogenicity of Bd in amphibian populations.

Strauss, Alex; Smith, Kevin G.

2013-01-01

78

Response of larval Xenopus laevis to atrazine: assessment of growth, metamorphosis, and gonadal and laryngeal morphology.  

PubMed

Larval Xenopus laevis were exposed to one of four concentrations of atrazine (0, 1, 10, or 25 microg/L, 11 replicate tanks per treatment, 60-65 larvae per replicate) dissolved in an artificial pond water (frog embryo teratogenesis assay- Xenopus [FETAX]) medium beginning 48 h after hatching until the completion of metamorphosis. Separate groups of larvae (six replicate tanks per treatment, 60-65 larvae per replicate) were exposed to estradiol (100 microg/L), dihydrotestosterone (100 microg/L), or ethanol vehicle control dissolved in FETAX medium. None of the treatments affected posthatch mortality, larval growth, or metamorphosis. There were no treatment effects on sex ratios except for estradiol, which produced a greater percentage of female offspring. Exposure to either estradiol or 25 microg atrazine/L increased the incidence of intersex animals based on assessment of gonadal morphology. Atrazine did not reduce the size of the laryngeal dilator muscle, a sexually dimorphic muscle in this species. We conclude that environmentally relevant concentrations of atrazine do not influence metamorphosis or sex ratios and do not inhibit sexually dimorphic larynx growth in X. laevis. The incidence of atrazine-induced intersex animals was small (<5%) and occurred only at the greatest concentration of atrazine tested, a concentration that is rarely observed in surface waters in the United States. PMID:12558173

Carr, James A; Gentles, Angie; Smith, Ernest E; Goleman, Wanda L; Urquidi, Lina J; Thuett, Kerry; Kendall, Ronald J; Giesy, John P; Gross, Tim S; Solomon, Keith R; Van Der Kraak, Glen

2003-02-01

79

Why Do We Need an Amphibian Ark?  

NSDL National Science Digital Library

The issue focused, peer reviewed article describes a response to the crisis of amphibian declines. The Amphibian Ark (AArk) would coordinate conservation activities, assess amphibian species that may go extinct, keep endangered species in captivity in suitable locations, such as zoos, and release animals into the wild when their survival can be assured.

Kevin Zippel (Amphibian Ark;)

2007-05-01

80

Global amphibian declines: sorting the hypotheses  

Microsoft Academic Search

Reports of malformed amphibians and global amphibian declines have led to public concern, particularly because amphibians are thought to be indicator species of overall envi- ronmental health. The topic also draws scientific attention because there is no obvious, simple answer to the question of what is causing amphi- bian declines? Complex interactions of several anthropogenic factors are probably at work,

James P. Collins; Andrew Storfer

2003-01-01

81

BIOTIC FACTORS IN AMPHIBIAN POPULATION DECLINES  

EPA Science Inventory

Amphibians evolved in, and continue to exist in, habitats that are replete with many other organisms. Some of these organisms serve as prey for amphibians and others interact with amphibians as predators, competitors, pathogens, or symbionts. Still other organisms in their enviro...

82

Tennessee Amphibian Monitoring Program (TAMP)  

NSDL National Science Digital Library

The Tennessee Wildlife Resources Agency (TWRA) and the Tennessee Department of Environment and Conservation co-sponsor the Tennessee Amphibian Monitoring Program (TAMP). A volunteer-based, multi-agency effort "to assess the current status of amphibians (frogs, toads, and salamanders)" across the state, TAMP is open to all interested participants. The homepage introduces and describes the need for TAMP, and provides a brief list of related sites. Also at the TAMP site are detailed survey protocols (with accompanying color photographs of frogs and toads) and a list of selected references.

83

The genetic covariance between life cycle stages separated by metamorphosis.  

PubMed

Metamorphosis is common in animals, yet the genetic associations between life cycle stages are poorly understood. Given the radical changes that occur at metamorphosis, selection may differ before and after metamorphosis, and the extent that genetic associations between pre- and post-metamorphic traits constrain evolutionary change is a subject of considerable interest. In some instances, metamorphosis may allow the genetic decoupling of life cycle stages, whereas in others, metamorphosis could allow complementary responses to selection across the life cycle. Using a diallel breeding design, we measured viability at four ontogenetic stages (embryo, larval, juvenile and adult viability), in the ascidian Ciona intestinalis and examined the orientation of additive genetic variation with respect to the metamorphic boundary. We found support for one eigenvector of G: (gobsmax ), which contrasted larval viability against embryo viability and juvenile viability. Target matrix rotation confirmed that while gobsmax shows genetic associations can extend beyond metamorphosis, there is still considerable scope for decoupled phenotypic evolution. Therefore, although genetic associations across metamorphosis could limit that range of phenotypes that are attainable, traits on either side of the metamorphic boundary are capable of some independent evolutionary change in response to the divergent conditions encountered during each life cycle stage. PMID:24966319

Aguirre, J David; Blows, Mark W; Marshall, Dustin J

2014-08-01

84

North American Endangered Amphibians Card Game  

NSDL National Science Digital Library

In this activity, learners can play two card games related to endangered species, specifically North American amphibians. In version one, "Guess My Amphibian," a learner secretly selects a card and players take turns asking yes-or-no questions to identify the mystery amphibian. In version two, "Guess My Rule," a learner selects a secret rule about amphibians and players try to identify the rule. For an extra challenge, use string circles to form a Venn Diagram that players can use to sort the amphibians and play a more challenging version of "Guess My Rule."

Terc; Zoo, Omaha'S H.; Services, Institute O.

2012-12-20

85

Exposure to coal combustion residues during metamorphosis elevates corticosterone content and adversely affects oral morphology, growth, and development in Rana sphenocephala  

SciTech Connect

Coal combustion residues (CCRs) are documented to negatively impact oral morphology, growth, and development in larval amphibians. It is currently unclear what physiological mechanisms may mediate these effects. Corticosterone, a glucocorticoid hormone, is a likely mediator because when administered exogenously it, like CCRs, also negatively influences oral morphology, growth, and development in larval amphibians. In an attempt to identify if corticosterone mediates these effects, we raised larval Southern Leopard Frogs, Rana sphenocephala, on either sand or CCR substrate and documented effects of sediment type on whole body corticosterone, oral morphology, and time to and mass at key metamorphic stages. Coal combustion residue treated tadpoles contained significantly more corticosterone than controls throughout metamorphosis. However, significantly more oral abnormalities occurred early in metamorphosis when differences in corticosterone levels between treatments were minimal. Overall, CCR-treated tadpoles took significantly more time to transition between key stages and gained less mass between stages than controls, but these differences between treatments decreased during later stages when corticosterone differences between treatments were greatest. Our results suggest endogenous increase in corticosterone content and its influence on oral morphology, growth and development is more complex than previously thought.

Peterson, J.D.; Peterson, V.A.; Mendonca, M.T. [Auburn University, Auburn, AL (USA). Dept. of Biological Science

2009-01-15

86

Multiple overseas dispersal in amphibians  

Microsoft Academic Search

Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicari- ance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This

Miguel Vences; D. Rodriguez Vieites; Frank Glaw; Henner Brinkmann; Joachim Kosuch; Michael Veith; Axel Meyer

2003-01-01

87

METAPOPULATION DYNAMICS AND AMPHIBIAN CONSERVATION  

EPA Science Inventory

In many respects, amphibian spatial dynamics resemble classical metapopulation models, where subpopulations in breeding ponds blink in and out of existance and where extinction and colonization rates are functions of pond spatial arrangement. This "ponds-as-patches" view of amphi...

88

Ecopathology of Ranaviruses Infecting Amphibians  

PubMed Central

Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in organ necrosis and massive hemorrhaging. Subclinical infections have been documented, although their role in ranavirus persistence and emergence remains unclear. Water is an effective transmission medium for ranaviruses, and survival outside the host may be for significant duration. In aquatic communities, amphibians, reptiles and fish may serve as reservoirs. Controlled studies have shown that susceptibility to ranavirus infection and disease varies among amphibian species and developmental stages, and likely is impacted by host-pathogen coevolution, as well as, exogenous environmental factors. Field studies have demonstrated that the likelihood of epizootics is increased in areas of cattle grazing, where aquatic vegetation is sparse and water quality is poor. Translocation of infected amphibians through commercial trade (e.g., food, fish bait, pet industry) contributes to the spread of ranaviruses. Such introductions may be of particular concern, as several studies report that ranaviruses isolated from ranaculture, aquaculture, and bait facilities have greater virulence (i.e., ability to cause disease) than wild-type isolates. Future investigations should focus on the genetic basis for pathogen virulence and host susceptibility, ecological and anthropogenic mechanisms contributing to emergence, and vaccine development for use in captive populations and species reintroduction programs.

Miller, Debra; Gray, Matthew; Storfer, Andrew

2011-01-01

89

Amphibian Resources on the Internet  

Microsoft Academic Search

The use of amphibians in classrooms and research labora- tories has increased, along with a corresponding increase in the amount of information about these animals on the In- ternet. This review is intended to aid both novices and ex- perts in the search of such information. The bibliography of Internet resources is organized by discipline and includes general and selected

Michael W. Nolan; Stephen A. Smith

90

Multiple overseas dispersal in amphibians.  

PubMed Central

Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicariance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This island belongs to the Comoro archipelago, which is entirely volcanic and surrounded by sea depths of more than 3500 m. This constitutes the first observation of endemic amphibians on oceanic islands that did not have any past physical contact to other land masses. The two species of frogs had previously been thought to be nonendemic and introduced from Madagascar, but clearly represent new species based on their morphological and genetic differentiation. They belong to the genera Mantidactylus and Boophis in the family Mantellidae that is otherwise restricted to Madagascar, and are distinguished by morphology and mitochondrial and nuclear DNA sequences from mantellid species occurring in Madagascar. This discovery permits us to update and test molecular clocks for frogs distributed in this region. The new calibrations are in agreement with previous rate estimates and indicate two further Cenozoic transmarine dispersal events that had previously been interpreted as vicariance: hyperoliid frogs from Africa to Madagascar (Heterixalus) and from Madagascar to the Seychelles islands (Tachycnemis). Our results provide the strongest evidence so far that overseas dispersal of amphibians exists and is no rare exception, although vicariance certainly retains much of its importance in explaining amphibian biogeography.

Vences, Miguel; Vieites, David R; Glaw, Frank; Brinkmann, Henner; Kosuch, Joachim; Veith, Michael; Meyer, Axel

2003-01-01

91

Toxicity to amphibians of environmental extracts from natural waters in National Parks and Fish and Wildlife Refuges  

USGS Publications Warehouse

Amphibian population declines are not limited to overtly degraded habitats, but often occur in relatively pristine environments such as national parks or wildlife refuges, thus forcing biologists to examine less obvious causes for declines such as the presence of contaminants. The objective of our study was to extract naturally-occurring compounds from amphibian habitats (using semipermeable membrane devices) in three national parks or wildlife refuges (two sites within Sequoia Kings Canyon National Park, Big Bend National Park, and Kenai National Wildlife Refuge), and assess their toxicity to developing larvae using bioassays. Extracts did not cause mortality, so all effects observed were sublethal, influencing life history characteristics. In all three areas studied, amphibians reared in extracts from at least one of the two sites exhibited either a lengthened larval period or reduced mass at metamorphosis. Extracts from both the air and water at one site in Sequoia Kings Canyon National Park lengthened the larval period, which is in agreement with studies showing elevated levels of aerially transported contaminants at sites such as this within the park. Ultraviolet radiation, which is also suspected of having caused amphibian declines and was included as a factor in our study, did not act alone or alter the toxicity of the extracts. ?? ISSCA 2005.

Bridges, C. M.; Little, E. E.

2005-01-01

92

THE METAMORPHOSIS OF HEMOGLOBIN IN THE BULLFROG  

PubMed Central

1. Tadpole and adult hemoglobin do not differ significantly in molecular weight. The molecular weight of both is in the neighborhood of 68,000. 2. Heme-heme interaction as measured by the value of n in Hill's equation is virtually the same—about 2.8—in both tadpole and adult. 3. There appears to be no significant effect of pH upon the oxygen equilibrium of tadpole hemoglobin, in contrast to large Bohr and reverse Bohr effects in the adult. This is taken to mean that during metamorphosis acid groups of globin become sensitive to the oxygenation of heme by some change in the mode of linkage between heme and globin. 4. The oxygen affinity of tadpole hemoglobin is about seven times as great as that of the adult at pH 6 and twice as great at pH 9.

Riggs, Austen

1951-01-01

93

Aedes aegypti midgut remodeling during metamorphosis.  

PubMed

The Aedes aegypti midgut is restructured during metamorphosis; its epithelium is renewed by replacing the digestive and endocrine cells through stem or regenerative cell differentiation. Shortly after pupation (white pupae) begins, the larval digestive cells are histolized and show signs of degeneration, such as autophagic vacuoles and disintegrating microvilli. Simultaneously, differentiating cells derived from larval stem cells form an electron-dense layer that is visible 24h after pupation begins. Forty-eight hours after pupation onset, the differentiating cells yield an electron-lucent cytoplasm rich in microvilli and organelles. Dividing stem cells were observed in the fourth instar larvae and during the first 24h of pupation, which suggests that stem cells proliferate at the end of the larval period and during pupation. This study discusses various aspects of the changes during midgut remodeling for pupating A. aegypti. PMID:24472855

Fernandes, Kenner Morais; Neves, Clóvis Andrade; Serrão, José Eduardo; Martins, Gustavo Ferreira

2014-06-01

94

Radar image analysis utilizing junctive image metamorphosis  

NASA Astrophysics Data System (ADS)

A feasibility study was initiated to investigate the ability of algorithms developed for medical sonogram image analysis, to be trained for extraction of cartographic information from synthetic aperture radar imagery. BioComputer Research Inc. has applied proprietary `junctive image metamorphosis' algorithms to cancer cell recognition and identification in ultrasound prostate images. These algorithms have been shown to support automatic radar image feature detection and identification. Training set images were used to develop determinants for representative point, line and area features, which were used on test images to identify and localize the features of interest. The software is computationally conservative; operating on a PC platform in real time. The algorithms are robust; having applicability to be trained for feature recognition on any digital imagery, not just those formed from reflected energy, such as sonograms and radar images. Applications include land mass characterization, feature identification, target recognition, and change detection.

Krueger, Peter G.; Gouge, Sally B.; Gouge, Jim O.

1998-09-01

95

The Next Decade in Career Counseling: Cocoon Maintenance or Metamorphosis?  

ERIC Educational Resources Information Center

Articulates the strengths, weaknesses, opportunities, threats, and future vision for career counseling using a cocoon maintenance or metamorphosis metaphor. Concludes with a vision for the future for the discipline and profession of career counseling. (Contains 40 references.) (GCP)

Parmer, Twinet; Rush, Lee Covington

2003-01-01

96

Timing is everything: the effects of putative dopamine antagonists on metamorphosis vary with larval age and experimental duration in the prosobranch gastropod Crepidula fornicata.  

PubMed

The signal transduction pathway through which excess potassium ion stimulates the larvae of many marine invertebrates to metamorphose is incompletely understood. Recent evidence suggests that dopamine plays important roles in the metamorphic pathway of Crepidula fornicata. Therefore, we asked whether blocking dopamine receptors might prevent excess potassium ion from stimulating metamorphosis in this species. Surprisingly, the effects of the three putative dopamine antagonists tested (all at 10 microM) varied with exposure duration and the age of competent larvae. Chlorpromazine, a nonspecific dopamine antagonist known to have a number of other pharmacological effects, blocked the inductive action of excess potassium ion during the initial 5-8-h exposure periods in most assays, particularly for younger or smaller competent larvae. However, chlorpromazine in the absence of excess potassium ion also stimulated metamorphosis, particularly over the next 18 h, and worked faster on older competent larvae than on younger competent larvae. The specific D(1) antagonist R(+)-Sch-23309 had similar effects, blocking potassium-stimulated metamorphosis in short-term exposures and stimulating metamorphosis in longer exposures, particularly for older competent larvae. Although the specific D(2) antagonist spiperone (SPIP) blocked the inductive effects of excess potassium ion in only 1 of 6 assays during the first 6 h of exposure, it blocked metamorphosis in 2 of the assays during 24-h exposures. Our results indicate that dopamine receptors are involved in the pathway through which excess potassium ion stimulates metamorphosis in C. fornicata. In addition, the largely latent inductive effects of chlorpromazine, an inhibitor of nitric oxide synthase, suggest that endogenous nitric oxide may play a natural role in inhibiting metamorphosis in this species. Overall, our results would then suggest that exposing larvae of C. fornicata to excess K(+) leads to a shutdown of nitric oxide synthesis via a dopaminergic pathway, a pathway that can be blocked by some dopamine antagonists. Alternatively, chlorpromazine might eventually be stimulating metamorphosis by elevating endogenous cyclic nucleotide (e.g., cAMP) concentrations, again acting downstream from the steps acted on directly by excess K(+). PMID:11971809

Pechenik, Jan A; Li, Wei; Cochrane, David E

2002-04-01

97

Stress and chytridiomycosis: Exogenous exposure to corticosterone does not alter amphibian susceptibility to a fungal pathogen.  

PubMed

Recent emergence and spread of the amphibian fungal pathogen, Batrachochytrium dendrobatidis (Bd) has been attributed to a number of factors, including environmental stressors that increase host susceptibility to Bd. Physiological stress can increase circulating levels of the hormone, corticosterone, which can alter a host's physiology and affect its susceptibility to pathogens. We experimentally elevated whole-body levels of corticosterone in both larval and post-metamorphic amphibians, and subsequently tested their susceptibility to Bd. Larvae of three species were tested (Anaxyrus boreas, Rana cascadae, and Lithobates catesbeianus) and one species was tested after metamorphosis (R. cascadae). After exposure to Bd, we measured whole-body corticosterone, infection, mortality, growth, and development. We found that exposure to exogenous corticosterone had no effect on Bd infection in any species or at either life stage. Species varied in whole-body corticosterone levels and exposure to corticosterone reduced mass in A. boreas and R. cascadae larvae. Exposure to Bd did not affect mortality, but had a number of sublethal effects. Across species, larvae exposed to Bd had higher corticosterone levels than unexposed larvae, but the opposite pattern was found in post-metamorphic R. cascadae. Bd exposure also increased larval length in all species and increased mass in R. cascadae larvae. Our results indicate that caution is warranted in assuming a strong link between elevated levels of corticosterone and disease susceptibility in amphibians. The role of physiological stress in altering Bd prevalence in amphibian populations is likely much more complicated than can be explained by examining a single "stress" endpoint. J. Exp. Zool. 321A:243-253, 2014. © 2014 Wiley Periodicals, Inc. PMID:24610865

Searle, Catherine L; Belden, Lisa K; Du, Pang; Blaustein, Andrew R

2014-06-01

98

Pesticide Mixtures, Endocrine Disruption, and Amphibian Declines: Are We Underestimating the Impact?  

PubMed Central

Amphibian populations are declining globally at an alarming rate. Pesticides are among a number of proposed causes for these declines. Although a sizable database examining effects of pesticides on amphibians exists, the vast majority of these studies focus on toxicological effects (lethality, external malformations, etc.) at relatively high doses (parts per million). Very few studies focus on effects such as endocrine disruption at low concentrations. Further, most studies examine exposures to single chemicals only. The present study examined nine pesticides (four herbicides, two fungicides, and three insecticides) used on cornfields in the midwestern United States. Effects of each pesticide alone (0.1 ppb) or in combination were examined. In addition, we also examined atrazine and S-metolachlor combined (0.1 or 10 ppb each) and the commercial formulation Bicep II Magnum, which contains both of these herbicides. These two pesticides were examined in combination because they are persistent throughout the year in the wild. We examined larval growth and development, sex differentiation, and immune function in leopard frogs (Rana pipiens). In a follow-up study, we also examined the effects of the nine-compound mixture on plasma corticosterone levels in male African clawed frogs (Xenopus laevis). Although some of the pesticides individually inhibited larval growth and development, the pesticide mixtures had much greater effects. Larval growth and development were retarded, but most significantly, pesticide mixtures negated or reversed the typically positive correlation between time to metamorphosis and size at metamorphosis observed in controls: exposed larvae that took longer to metamorphose were smaller than their counterparts that metamorphosed earlier. The nine-pesticide mixture also induced damage to the thymus, resulting in immunosuppression and contraction of flavobacterial meningitis. The study in X. laevis revealed that these adverse effects may be due to an increase in plasma levels of the stress hormone corticosterone. Although it cannot be determined whether all the pesticides in the mixture contribute to these adverse effects or whether some pesticides are effectors, some are enhancers, and some are neutral, the present study revealed that estimating ecological risk and the impact of pesticides on amphibians using studies that examine only single pesticides at high concentrations may lead to gross underestimations of the role of pesticides in amphibian declines.

Hayes, Tyrone B.; Case, Paola; Chui, Sarah; Chung, Duc; Haeffele, Cathryn; Haston, Kelly; Lee, Melissa; Mai, Vien Phoung; Marjuoa, Youssra; Parker, John; Tsui, Mable

2006-01-01

99

Bioaccumulation of trace elements in omnivorous amphibian larvae: Implications for amphibian health and contaminant transport  

Microsoft Academic Search

Despite the influence that amphibians have on the flow of energy and nutrients in ecological systems, the role that amphibians play in transporting contaminants through food webs has received very little attention. This study was undertaken to investigate bioaccumulation of trace elements in amphibians relative to other small aquatic organisms in a contaminated wetland. We collected bullfrog larvae (Rana catesbeiana)

Jason M. Unrine; William A. Hopkins; Christopher S. Romanek; Brian P. Jackson

2007-01-01

100

Myofiber turnover is used to retrofit frog jaw muscles during metamorphosis.  

PubMed

Metamorphic reorganization of the head in anuran amphibians entails abrupt restructuring of the jaw complex as larval feeding structures are transformed into their adult configurations. In this morphometric study, light microscopy wa used to analyze the larval maturation and metamorphic transfiguration of the adductor jaw muscles in the leopard frog (Rana pipiens). Larval jaw muscles, first established during embryogenesis, continue to grow by fiber addition until prometamorphosis, stage XII. Thereafter, fiber number remains stable but additional muscle growth continues by hypertrophy of the individual fibers until metamorphic climax. During metamorphic stages XIX-XXIII, a complete involution of all larval myofibers occurs. Simultaneously, within the same muscle beds, a second wave of myogenesis produces myoblasts which are the precursors of adult jaw myofibers. New muscle fibers continue to be added to these muscles well after the completion of metamorphosis; however, the total duration of the postmetamorphic myogenic period has not been defined. These observations provide clear evidence that the entir population of primary myofibers used in larval oral activity disappears from the adductor muscle beds and is replaced by a second wave of myogenesis commencing during climax. These findings indicate that the adductor jaw muscles are prepared for adult feeding by a complicated cellular process that retrofits existing muscle beds with a completely new complement of myofibers. PMID:2783829

Alley, K E

1989-01-01

101

Effects of acute and chronic acidification on three larval amphibians that breed in temporary ponds  

SciTech Connect

This study explored the effects of acute (7 days) and chronic (4 months) exposure to pH 4.2 on three species of larval amphibians, Ambystoma jeffersonianum, Ambystoma maculatum, and Rana sylvatica. Acute tests were conducted in 24 impermeable enclosures in three temporary ponds. Total dissolved aluminum was higher in acidified enclosures in comparison with controls (pH 4.2, [Al] approximately 10-30 microM and pH greater than 4.7, [Al] approximately 5-15 microM, respectively). Greater mortality of A. jeffersonianum occurred at pH 4.2 than at pH greater than 4.7, whereas survival of A. maculatum and R. sylvatica were unaffected by pH. Mean wet masses of R. sylvatica were significantly lower at pH 4.2 than at pH greater than 4.7, but mean wet masses of surviving A. jeffersonianum and A. maculatum were not influenced by pH. There were no pH-related differences in body sodium concentration in larval R. sylvatica. Chronic acidification of mesocosms to pH 4.2 ([Al] approximately 16 microM) (controls = pH greater than 6, [Al] approximately 0.1 microM) resulted in total mortality of A. jeffersonianum. Survival of A. maculatum and R. sylvatica were not associated with pH, but survival of A. maculatum was low at both pH levels. Time to metamorphosis was longer for R. sylvatica maintained at pH 4.2, but not for A. maculatum. No differences in wet masses at metamorphosis were observed for R. sylvatica or A. maculatum. These results indicate that short and long term acidification of temporary wetlands could dramatically affect amphibians which rely upon them as breeding sites, either by causing mortality or by decreasing growth rates.

Rowe, C.L.; Sadinski, W.J.; Dunson, W.A. (Pennsylvania State Univ., University Park (United States))

1992-10-01

102

Amphibians at risk? Susceptibility of terrestrial amphibian life stages to pesticides.  

PubMed

Current pesticide risk assessment does not specifically consider amphibians. Amphibians in the aquatic environment (aquatic life stages or postmetamorphic aquatic amphibians) and terrestrial living juvenile or adult amphibians are assumed to be covered by the risk assessment for aquatic invertebrates and fish, or mammals and birds, respectively. This procedure has been evaluated as being sufficiently protective regarding the acute risk posed by a number of pesticides to aquatic amphibian life stages (eggs, larvae). However, it is unknown whether the exposure and sensitivity of terrestrial living amphibians are comparable to mammalian and avian exposure and sensitivity. We reviewed the literature on dermal pesticide absorption and toxicity studies for terrestrial life stages of amphibians, focusing on the dermal exposure pathway, that is, through treated soil or direct overspray. In vitro studies demonstrated that cutaneous absorption of chemicals is significant and that chemical percutaneous passage, P (cm/h), is higher in amphibians than in mammals. In vivo, the rapid and substantial uptake of the herbicide atrazine from treated soil by toads (Bufo americanus) has been described. Severe toxic effects on various amphibian species have been reported for field-relevant application rates of different pesticides. In general, exposure and toxicity studies for terrestrial amphibian life stages are scarce, and the reported data indicate the need for further research, especially in light of the global amphibian decline. PMID:21898550

Brühl, Carsten A; Pieper, Silvia; Weber, Brigitte

2011-11-01

103

The complexity of amphibian population declines: understanding the role of cofactors in driving amphibian losses.  

PubMed

Population losses and extinctions of species are occurring at unprecedented rates, as exemplified by declines and extinctions of amphibians worldwide. However, studies of amphibian population declines generally do not address the complexity of the phenomenon or its implications for ecological communities, focusing instead on single factors affecting particular amphibian species. We argue that the causes for amphibian population declines are complex; may differ among species, populations, and life stages within a population; and are context dependent with multiple stressors interacting to drive declines. Because amphibians are key components of communities, we emphasize the importance of investigating amphibian declines at the community level. Selection pressures over evolutionary time have molded amphibian life history characteristics, such that they may remain static even in the face of strong, recent human-induced selection pressures. PMID:21449968

Blaustein, Andrew R; Han, Barbara A; Relyea, Rick A; Johnson, Pieter T J; Buck, Julia C; Gervasi, Stephanie S; Kats, Lee B

2011-03-01

104

ITRAQ MASS SPECTROMETRIC PROTEOMIC APPLICATIONS FOR IN VIVO TOXICOLOGY STUDIES OF AMPHIBIAN SPECIES: DATA HANDLING AND INTERPRETATION USING PEPTIDE-TAGGING SOFTWARE  

EPA Science Inventory

This addresses the USEPA's need for a cost effective, non-mammalian screening assay for thyroid axis disrupting chemicals; a multi-endpoint strategy combining molecular and in vivo protocols in an amphibian model is being applied at MED Duluth....

105

Estrogens Can Disrupt Amphibian Mating Behavior  

Microsoft Academic Search

The main component of classical contraceptives, 17?-ethinylestradiol (EE2), has high estrogenic activity even at environmentally relevant concentrations. Although estrogenic endocrine disrupting compounds are assumed to contribute to the worldwide decline of amphibian populations by adverse effects on sexual differentiation, evidence for EE2 affecting amphibian mating behaviour is lacking. In this study, we demonstrate that EE2 exposure at five different concentrations

Frauke Hoffmann; Werner Kloas

2012-01-01

106

Transdermal delivery of corticosterone in terrestrial amphibians  

Microsoft Academic Search

Stressors elicit allostatic responses that allow animals to cope with changing and challenging environments and also cause release of glucocorticoid hormones (GCs). Compared to other vertebrate classes, relatively little is known about amphibian behavioral and physiological responses to GCs. To understand the effects of elevated plasma GCs in amphibians, exogenous application of GCs is necessary, but traditional methods to elevate

Corina L. Wack; Matthew B. Lovern; Sarah K. Woodley

2010-01-01

107

DEVELOPMENT OF AMPHIBIAN-BASED MODELS OF THYROID-AXIS DISRUPTION  

EPA Science Inventory

The research presented here describes the development of in vivo and in vitro assay systems to test chemicals for their ability to alter the HPT-axis. This data derived from this research will be used to support development of diagnostic indicators for use with amphibian whole o...

108

Mesoderm Induction in Amphibians: The Role of TGF-beta 2Like Factors  

Microsoft Academic Search

Mesoderm induction in the amphibian embryo can be studied by exposing animal region explants (destined to become ectoderm) to appropriate stimuli and assaying the appearance of mesodermal products like alpha -actin messenger RNA. Transforming growth factor beta 2 (TGF-beta 2), but not TGF-beta 1, was active in alpha -actin induction, while addition of fibroblast growth factor had a small synergistic

Frederic Rosa; Anita B. Roberts; David Danielpour; Linda L. Dart; Michael B. Sporn; Igor B. Dawid

1988-01-01

109

First evidence of amphibian chytrid fungus (Batrachochytrium dendrobatidis) and ranavirus in Hong Kong amphibian trade.  

PubMed

The emerging infectious amphibian diseases caused by amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) and ranaviruses are responsible for global amphibian population declines and extinctions. Although likely to have been spread by a variety of activities, transcontinental dispersal appears closely associated with the international trade in live amphibians. The territory of Hong Kong reports frequent, high volume trade in amphibians, and yet the presence of Bd and ranavirus have not previously been detected in either traded or free-ranging amphibians. In 2012, a prospective surveillance project was conducted to investigate the presence of these pathogens in commercial shipments of live amphibians exported from Hong Kong International Airport. Analysis of skin (Bd) and cloacal (ranavirus) swabs by quantitative PCR detected pathogen presence in 31/265 (11.7%) and in 105/185 (56.8%) of amphibians, respectively. In addition, the water in which animals were transported tested positive for Bd, demonstrating the risk of pathogen pollution by the disposal of untreated wastewater. It is uncertain whether Bd and ranavirus remain contained within Hong Kong's trade sector, or if native amphibians have already been exposed. Rapid response efforts are now urgently needed to determine current pathogen distribution in Hong Kong, evaluate potential trade-associated exposure to free-ranging amphibians, and identify opportunities to prevent disease establishment. PMID:24599268

Kolby, Jonathan E; Smith, Kristine M; Berger, Lee; Karesh, William B; Preston, Asa; Pessier, Allan P; Skerratt, Lee F

2014-01-01

110

The phylogenetic odyssey of the erythrocyte. IV. The amphibians.  

PubMed

Amphibians manifest permanently nucleated, oval, flattened, biconvex erythrocytes. These cells demonstrate a cytoskeleton which is responsible for their morphogenetic conversion from a sphere to an ellipse and imparts to their cellular mass reversibility of traumatic deformation. The class Amphibia has the largest of all erythrocytes attaining volumes greater than 10,000 femtoliters in the Amphiuma. The large dimensions reflect evolutionary processes, genomic size, ploidy and the relative size of other somatic cells. Conversely, the erythrocyte count and hemoglobin concentration of these species are low. Occasional denucleated red cells can be seen in the peripheral blood but may attain levels of 90-95% of the total circulating population in certain members of the tribe Bolitoglossini (e.g. Batrachoseps attenuatus). These erythroplastids retain the marginal band thus remaining different from mammalian erythrocytes. Embryologically, erythropoiesis initiates in the yolk sac and then progresses to the kidney, liver, and possibly spleen. The yolk sac cohort is transitory and is successively replaced by the larval and definitive populations of erythrocytes. Red cell production (along with thrombocytopoiesis) in adult urodeles is conducted intravascularly in the spleen. In anurans this organ is usually the major site although the liver also serves as a secondary locus for this activity. Medullary (bone marrow) erythropoiesis makes its phylogenetic debut in anurans and typically occurs during heightened hemopoiesis following metamorphosis or hibernation. Maturation of the erythrocyte in the circulation is commonplace (especially in urodeles) while proliferation at this site is inducible by splenectomy and/or hemolysins. Erythrocyte-related values demonstrate variable differences associated with age, weight, season, gender, and environment. PMID:9046052

Glomski, C A; Tamburlin, J; Hard, R; Chainani, M

1997-01-01

111

Chytridiomycosis: a global threat to amphibians.  

PubMed

Chytridiomycosis, which is caused by Batrachochytrium dendrobatidis, is an emerging infectious disease of amphibians. The disease is one of the main causes of the global decline in amphibians. The aetiological agent is ubiquitous, with worldwide distribution, and affects a large number of amphibian species in several biomes. In the last decade, scientific research has substantially increased knowledge of the aetiological agent and the associated infection. However, important epidemiological aspects of the environment-mediated interactions between the aetiological agent and the host are not yet clear. The objective of the present review is to describe chytridiomycosis with regard to the major features of the aetiological agent, the host and the environment. PMID:24761737

Pereira, P L L; Torres, A M C; Soares, D F M; Hijosa-Valsero, M; Bécares, E

2013-12-01

112

ARMI National Atlas for Amphibian Distributions  

NSDL National Science Digital Library

This site, from The Amphibian Research and Monitoring Initiative (ARMI), is a compilation of current and historic records of amphibian occurrences. The atlas is organized taxonomically. There are separate sections for frogs and toads, and salamanders and newts. The location of each species is mapped separately. The ARMI Atlas is meant to be an educational tool for people wanting to learn or teach others about amphibians. It can also serve as a reference for habitat managers and researchers, identifying areas where more research is needed, as well as providing information about research that has previously been done.

113

Dynamic mechanical oscillations during metamorphosis of the monarch butterfly  

PubMed Central

The mechanical oscillation of the heart is fundamental during insect metamorphosis, but it is unclear how morphological changes affect its mechanical dynamics. Here, the micromechanical heartbeat with the monarch chrysalis (Danaus plexippus) during metamorphosis is compared with the structural changes observed through in vivo magnetic resonance imaging (MRI). We employ a novel ultra-sensitive detection approach, optical beam deflection, in order to measure the microscale motions of the pupae during the course of metamorphosis. We observed very distinct mechanical contractions occurring at regular intervals, which we ascribe to the mechanical function of the heart organ. Motion was observed to occur in approximately 15?min bursts of activity with frequencies in the 0.4–1.0?Hz range separated by periods of quiescence during the first 83 per cent of development. In the final stages, the beating was found to be uninterrupted until the adult monarch butterfly emerged. Distinct stages of development were characterized by changes in frequency, amplitude, mechanical quality factor and de/repolarization times of the mechanical pulsing. The MRI revealed that the heart organ remains functionally intact throughout metamorphosis but undergoes morphological changes that are reflected in the mechanical oscillation.

Pelling, Andrew E; Wilkinson, Paul R; Stringer, Richard; Gimzewski, James K

2008-01-01

114

Presynaptic Function during Muscle Remodeling in Insect Metamorphosis  

Microsoft Academic Search

During metamorphosis the leg neuromuscular system of the moth Manduca sexta undergoes an extensive remodeling as the larval muscles degenerate and are replaced by new mus- cles in the adult. The terminal processes of persistent leg motoneurons undergo severe regression followed by regrowth (Consoulas et al., 1996), accompanied, as shown here, by the loss and re-establishment of functional presynaptic specializa-

Christos Consoulas; Richard B. Levine

1998-01-01

115

Functional role of aspartic proteinase cathepsin D in insect metamorphosis  

PubMed Central

Background Metamorphosis is a complex, highly conserved and strictly regulated development process that involves the programmed cell death of obsolete larval organs. Here we show a novel functional role for the aspartic proteinase cathepsin D during insect metamorphosis. Results Cathepsin D of the silkworm Bombyx mori (BmCatD) was ecdysone-induced, differentially and spatially expressed in the larval fat body of the final instar and in the larval gut of pupal stage, and its expression led to programmed cell death. Furthermore, BmCatD was highly induced in the fat body of baculovirus-infected B. mori larvae, suggesting that this gene is involved in the induction of metamorphosis of host insects infected with baculovirus. RNA interference (RNAi)-mediated BmCatD knock-down inhibited programmed cell death of the larval fat body, resulting in the arrest of larval-pupal transformation. BmCatD RNAi also inhibited the programmed cell death of larval gut during pupal stage. Conclusion Based on these results, we concluded that BmCatD is critically involved in the programmed cell death of the larval fat body and larval gut in silkworm metamorphosis.

Gui, Zhong Zheng; Lee, Kwang Sik; Kim, Bo Yeon; Choi, Yong Soo; Wei, Ya Dong; Choo, Young Moo; Kang, Pil Don; Yoon, Hyung Joo; Kim, Iksoo; Je, Yeon Ho; Seo, Sook Jae; Lee, Sang Mong; Guo, Xijie; Sohn, Hung Dae; Jin, Byung Rae

2006-01-01

116

Report of Amphibian Development Group  

NASA Technical Reports Server (NTRS)

Amphibian and fish embryos are extremely well suited for studies on pattern specification, whereas other systems (e.g., avian or mammalian) might be just as well suited for studies on differentiation or growth. Those distinctions are important for at least two reasons: (1) More precise focus regarding underlying mechanisms is called for when those distinctions are made. That facilitates the formulation of specific models or hypotheses; and (2) stress effects (i.e., the effects of weightlessness on structures (e.g., bones) which normally bear a load) are distinguished as being indirect, in contrast to direct effects of microgravity, which would be expected to act on pattern specification. That is, direct gravity effects are distinguished from indirect stress effects.

Malacinski, G.

1985-01-01

117

Amphibian resources on the internet.  

PubMed

The use of amphibians in classrooms and research laboratories has increased, along with a corresponding increase in the amount of information about these animals on the Internet. This review is intended to aid both novices and experts in the search of such information. The bibliography of Internet resources is organized by discipline and includes general and selected species information, taxonomy, natural history, anatomy and histology, physiology, ontogeny, genetics, conservation, toxicology, medicine and surgery, sources (for animals, housing, and research tools), listservs, databases, associations, educational sources, and husbandry. For each web site, descriptive titles, web addresses, and a brief review are provided. Note that the authors of this review cannot assure the accuracy of content in these web resources. PMID:17592191

Nolan, Michael W; Smith, Stephen A

2007-01-01

118

Agents from amphibians with anticancer properties.  

PubMed

Amphibians have been found to be a source of agents with anticancer properties. Bufalin, for example, is an anticancer agent that may induce apoptosis by its interaction with other genes and cellular components. Certain peptides with anticancer activities have been found in amphibian skin; they include magainins, aureins, citropin 1.1 and gaegurins. These peptides may exert a cytotoxic effect on human cancer cells through various mechanisms. Onconase, amphinase, cSBL (sialic acid-binding lectin purified from Rana catesbeiana eggs) and jSBL (sialic acid-binding lectin purified from Rana japonica eggs), which belong to the RNase A family, were purified from the oocyte cells and eggs of three amphibians, and they induce cytotoxicity by degrading cellular RNA. This paper discusses the medical and pharmaceutical significance of products derived from amphibians. PMID:18827558

Lu, Chuang-Xin; Nan, Ke-Jun; Lei, Yan

2008-11-01

119

Effects of Organic Compounds on Amphibian Reproduction.  

National Technical Information Service (NTIS)

Aquatic toxicity tests were conducted with atrazine, carbon tetrachloride, chloroform, methylene chloride, trisodium nitrilotriacetic acid (NTA), and phenol. Each compound was administered to developmental stages of three to five amphibian species. Exposu...

W. J. Birge J. A. Black R. A. Kuehne

1980-01-01

120

Native Reptiles and Amphibians of South Florida.  

National Technical Information Service (NTIS)

The 74 native species of reptiles and amphibians of South Florida (Lake Okeechobee southward) are listed. Their distributions among six major habitats, xeric, mesic, alternohygric, hygric, halohygric, and edificarian-ruderal are noted, with reference to t...

J. P. Crowder

1974-01-01

121

Chironomidae bloodworms larvae as aquatic amphibian food.  

PubMed

Different species of chironomids larvae (Diptera: Chironomidae) so-called bloodworms are widely distributed in the sediments of all types of freshwater habitats and considered as an important food source for amphibians. In our study, three species of Chironomidae (Baeotendipes noctivagus, Benthalia dissidens, and Chironomus riparius) were identified in 23 samples of larvae from Belgium, Poland, Russia, and Ukraine provided by a distributor in Belgium. We evaluated the suitability of these samples as amphibian food based on four different aspects: the likelihood of amphibian pathogens spreading, risk of heavy metal accumulation in amphibians, nutritive value, and risk of spreading of zoonotic bacteria (Salmonella, Campylobacter, and ESBL producing Enterobacteriaceae). We found neither zoonotic bacteria nor the amphibian pathogens Ranavirus and Batrachochytrium dendrobatidis in these samples. Our data showed that among the five heavy metals tested (Hg, Cu, Cd, Pb, and Zn), the excess level of Pb in two samples and low content of Zn in four samples implicated potential risk of Pb accumulation and Zn inadequacy. Proximate nutritional analysis revealed that, chironomidae larvae are consistently high in protein but more variable in lipid content. Accordingly, variations in the lipid: protein ratio can affect the amount and pathway of energy supply to the amphibians. Our study indicated although environmentally-collected chironomids larvae may not be vectors of specific pathogens, they can be associated with nutritional imbalances and may also result in Pb bioaccumulation and Zn inadequacy in amphibians. Chironomidae larvae may thus not be recommended as single diet item for amphibians. Zoo Biol. 33:221-227, 2014. © 2014 Wiley Periodicals, Inc. PMID:24535989

Sharifian Fard, Mojdeh; Pasmans, Frank; Adriaensen, Connie; Laing, Gijs Du; Janssens, Geert Paul Jules; Martel, An

2014-05-01

122

Surveys of calling amphibians in North Dakota  

USGS Publications Warehouse

Amphibians have received increased attention in recent years from the scientific community and general public alike. Many populations throughout the world have declined, or have been extirpated, often without an apparent cause. Concern about the status of amphibians has translated into a growing interest in systematic and statistically sound monitoring programs. Several extensive efforts to monitor populations of calling amphibians are in place, and more are under development. Necessary for the design of appropriate surveys is an understanding of the behavior, especially vocalization, of the various species, and how it varies by geographic location and environmental conditions. In 1995 we conducted roadside surveys of calling amphibians along 44 routes in North Dakota. We describe results of that survey, with special attention given to variables that influence detectability of calling amphibians. Unlike similar studies, we accounted for the amount of time observers spent listening for amphibians under different conditions. We found that the optimal conditions for a single survey for North Dakota in that year would be in early June, between the hours of 2300 and 0130, with ambient temperatures above 13 deg. C, and with no rain and little or no wind or moonlight. Multiple surveys in a year would yield better results, of course, especially for the wood frog (Rana sylvatica), which is most active earlier in the season. Studies such as ours should be replicated in space and time to ensure a well-designed survey.

Johnson, D. H.; Batie, R. D.

2001-01-01

123

Transdermal delivery of corticosterone in terrestrial amphibians.  

PubMed

Stressors elicit allostatic responses that allow animals to cope with changing and challenging environments and also cause release of glucocorticoid hormones (GCs). Compared to other vertebrate classes, relatively little is known about amphibian behavioral and physiological responses to GCs. To understand the effects of elevated plasma GCs in amphibians, exogenous application of GCs is necessary, but traditional methods to elevate GCs require handling and/or anesthesia which themselves are stressors. A less invasive alternative successfully used in birds and reptiles utilizes transdermal delivery by applying GCs via a dermal patch. We asked whether dermal patches containing corticosterone (CORT, the main GC in amphibians) would elevate plasma CORT in terrestrial salamanders and frogs. We explored the use of the dermal patch to deliver CORT in an acute, sustained, and repeated manner. Patches adhered well to the amphibians' moist skin and were easily removed to regulate the time course of CORT delivery. Application of CORT treated patches elevated plasma CORT concentrations compared to vehicle patches in all species. Patches delivered physiological levels of plasma CORT in ecologically relevant time frames. Repeated application and removal of CORT patches were used to simulate exposure to repeated stressors. Application of patches did not represent a stressor because plasma CORT concentrations were similar between animals that received vehicle patches and untreated animals. Thus, transdermal delivery of GCs represents a potentially useful tool to better understand amphibian allostatic responses to stressors, and perhaps amphibian population declines. PMID:20850442

Wack, Corina L; Lovern, Matthew B; Woodley, Sarah K

2010-12-01

124

Ligand binding pocket function of Drosophila USP is necessary for metamorphosis.  

PubMed

The widely accepted paradigm that epoxidized methyl farnesoates ("juvenile hormones," JHs) are the principal sesquiterpenoid hormones regulating insect metamorphosis was assessed in Drosophila melanogaster. GC-MS analysis of circulating methyl farnesoids during the mid to late 3rd instar showed that methyl farnesoate is predominant over methyl epoxyfarnesoate (=JH III). The circulating concentration of methyl farnesoate (reaching nearly 500 nM), was easily high enough on a kinetic basis to load the Drosophila ortholog of the nuclear hormone receptor RXR (also known as "ultraspiracle," USP), whereas the circulating concentrations of JH III and methyl bisepoxyfarnesoate (bisepoxyJH III) were not. The hypothesis that the ligand pocket of USP necessarily binds an endogenous ligand for differentiation of the immature to the adult was tested with USP mutated at residue that normally extends a side chain into the ligand binding pocket. An equilibrium binding assay confirmed that the mutation (Q288A) strongly altered methyl farnesoate interaction with USP, while a heterologous cell-line transfection assay confirmed that the mutation did not allosterically alter the transcriptional response of the ultraspiracle/ecdysone receptor heterodimer to ecdysteroid signaling. Transgenic wildtype USP driven by the cognate natural promoter rescued null animals to develop to the adult inside a normally formed puparium, while in contrast animals transgenically expressing instead the ligand pocket mutant exhibited developmental derangement at the larval to pupal transition, including failure to form a properly shaped or sclerotized puparium. Other point mutations to the pocket strongly reducing affinity for methyl farnesoate similarly disrupted the larval to pupal metamorphosis. These results suggest that normal larval to pupal maturation in this mecopteran model insect requires the involvement of a distinct endocrine axis of USP binding to its own endogenous terpenoid ligand. PMID:23211750

Jones, Grace; Teal, Peter; Henrich, Vincent C; Krzywonos, Anna; Sapa, Agnes; Wozniak, Mietek; Smolka, John; Jones, Davy

2013-02-01

125

Hemps, a novel EGF-like protein, plays a central role in ascidian metamorphosis.  

PubMed

All chordates share several characteristic features including a dorsal hollow neural tube, a notochord, a pharynx and an endostyle. Unlike other chordate taxa, ascidians have a biphasic life-history with two distinct body plans. During metamorphosis, the larval nerve cord and notochord degenerate and the pharyngeal gill slits and endostyle form. While ascidians, like other marine invertebrates, metamorphose in response to specific environmental cues, it remains unclear how these cues trigger metamorphosis. We have identified a novel gene (Hemps) which encodes a protein with a putative secretion signal sequence and four epidermal growth factor (EGF)-like repeats which is a key regulator of metamorphosis in the ascidian Herdmania curvata. Expression of Hemps increases markedly when the swimming tadpole larva becomes competent to undergo metamorphosis and then during the first 24 hours of metamorphosis. The Hemps protein is localised to the larval papillae and anterior epidermis of the larva in the region known to be required for metamorphosis. When the larva contacts an inductive cue the protein is released, spreading posteriorly and into the tunic as metamorphosis progresses. Metamorphosis is blocked by incubating larvae in anti-Hemps antibodies prior to the addition of the cue. Addition of recombinant Hemps protein to competent larvae induces metamorphosis in a concentration-dependent manner. A subgroup of genes are specifically induced during this process. These results demonstrate that the Hemps protein is a key regulator of ascidian metamorphosis and is distinct from previously described inducers of this process in terrestrial arthropods and aquatic vertebrates. PMID:10572055

Eri, R; Arnold, J M; Hinman, V F; Green, K M; Jones, M K; Degnan, B M; Lavin, M F

1999-12-01

126

An examination of amphibian sensitivity to environmental contaminants: are amphibians poor canaries?  

PubMed

Nearly two decades ago, the global biodiversity crisis was catapulted to the front pages of newspapers with the recognition of worldwide amphibian declines. Amphibians earned their appellation, 'canaries in a coal mine', because of apparent high sensitivity to human-mediated environmental change. The most frequently cited causes for high susceptibility include permeable skin, a dual aquatic-terrestrial life cycle and a relatively rudimentary immune system. While some researchers have questioned the basis for the canary assertion, there has been no systematic evaluation of amphibian sensitivity to environmental challenges relative to other taxa. Here, we apply a database representing thousands of toxicity tests to compare the responses of amphibians relative to that of other taxonomic groups. The use of standardized methods combined with large numbers of identical challenges enables a particularly powerful test of relative effect size. Overall, we found that amphibians only exhibit moderate relative responses to water-borne toxins. Our findings imply that, as far as chemical contaminants are concerned, amphibians are not particularly sensitive and might more aptly be described as 'miners in a coal mine'. To the extent that amphibian declines have been mediated by chemical contaminants, our findings suggest that population losses and extinctions may have already occurred in a variety of taxa much more sensitive than amphibians. PMID:19845728

Kerby, Jacob L; Richards-Hrdlicka, Kathryn L; Storfer, Andrew; Skelly, David K

2010-01-01

127

ADENOSINE TRIPHOSPHATASE LOCALIZATION IN AMPHIBIAN EPIDERMIS  

PubMed Central

The localization of ATPase1 activity has been studied by light and electron microscopy in the epidermis of Rana pipiens, Rana catesbiana, and Bufo marinus. The reaction was carried out on skin (glutaraldehyde-fixed or fresh) sectioned with or without freezing. Best results were obtained with nonfrozen sections of fixed tissue. The incubation mixture was either a Wachstein-Meisel medium, or a modification which approximates assay systems used in biochemical studies of transport ATPases. The reaction product was found localized in contact with the outer leaflet of all cell membranes facing the labyrinth of intercellular spaces of the epidermis. It was absent from: (a) membrane areas involved in cell junctions (desmosomes, zonulae and maculae occludentes); (b) cell membranes facing the external medium (i.e., those on the distal aspect of the ultimate cell layer in s. corneum); (c) cell membranes facing the dermis (those on the proximal aspect of cells in s. germinativum). In the presence of (Na+ + K+) the localization did not change, but the reaction was not appreciably activated. A similar though less intense reaction was obtained with ITP, but not with ADP, AMP, and GP as substrates. The results are discussed in relation to available data on transport ATPases in general, and on the morphology and physiology of amphibian skin in particular. Assuming that the ATPase studied is related to transport ATPase, the findings suggest a series of modifications to the frog skin model proposed by Koefoed-Johnsen and Ussing. The salient feature of this modified model is the localization of the Na+ pump along all cell membranes facing the intercellular spaces of the epidermis.

Farquhar, Marilyn G.; Palade, George E.

1966-01-01

128

On natural metamorphosis inducers of the cnidarians Hydractinia echinata (Hydrozoa) and Aurelia aurita (Scyphozoa)  

NASA Astrophysics Data System (ADS)

Hydractinia echinata and Aurelia aurita produce motile larvae which undergo metamorphosis to sessile polyps when induced by external cues. The polyps are found at restricted sites, A. aurita predominantly on rocks close to the shore, H. echinata on shells inhabited by hermit crabs. It has been argued that the differential distribution of the polyps in their natural environment largely reflects the distribution of the natural metamorphosis-inducing cues. In the case of H. echinata, bacteria of the genus Alteromonas were argued to meet these conditions. We found that almost all substrates collected in the littoral to induce metamorphosis in H. echinata, and several bacterial strains isolated from the sea, including the common E. coli, induce metamorphosis efficiently. In A. aurita metamorphosis may be induced by the water-air interface, whereby metamorphosis precedes (final) settlement.

Kroiher, M.; Berking, S.

129

Countryside biogeography of Neotropical reptiles and amphibians.  

PubMed

The future of biodiversity and ecosystem services depends largely on the capacity of human-dominated ecosystems to support them, yet this capacity remains largely unknown. Using the framework of countryside biogeography, and working in the Las Cruces system of Coto Brus, Costa Rica, we assessed reptile and amphibian assemblages within four habitats that typify much of the Neotropics: sun coffee plantations (12 sites), pasture (12 sites), remnant forest elements (12 sites), and a larger, contiguous protected forest (3 sites in one forest). Through analysis of 1678 captures of 67 species, we draw four primary conclusions. First, we found that the majority of reptile (60%) and amphibian (70%) species in this study used an array of habitat types, including coffee plantations and actively grazed pastures. Second, we found that coffee plantations and pastures hosted rich, albeit different and less dense, reptile and amphibian biodiversity relative to the 326-ha Las Cruces Forest Reserve and neighboring forest elements. Third, we found that the small ribbons of "countryside forest elements" weaving through farmland collectively increased the effective size of a 326-ha local forest reserve 16-fold for reptiles and 14-fold for amphibians within our 236-km2 study area. Therefore, countryside forest elements, often too small for most remote sensing techniques to identify, are contributing -95% of the available habitat for forest-dependent reptiles and amphibians in our largely human-dominated study region. Fourth, we found large and pond-reproducing amphibians to prefer human-made habitats, whereas small, stream-reproducing, and directly developing species are more dependent on forest elements. Our investigation demonstrates that tropical farming landscapes can support substantial reptile and amphibian biodiversity. Our approach provides a framework for estimating the conservation value of the complex working landscapes that constitute roughly half of the global land surface, and which are experiencing intensification pressure worldwide. PMID:24933806

Mendenhall, Chase D; Frishkoff, Luke O; Santos-Barrera, Georgina; Pacheco, Jesús; Mesfun, Eyobed; Mendoza Quijano, Fernando; Ehrlich, Paul R; Ceballos, Gerardo; Daily, Gretchen C; Pringle, Robert M

2014-04-01

130

Nitric Oxide Inhibits Metamorphosis in Larvae of Crepidula fornicata, the Slippershell Snail  

Microsoft Academic Search

This paper concerns the role of nitric oxide (NO) in controlling metamorphosis in the marine gastropod Crepidula fornicata. Metamorphosis was stimulated by the nitric oxide synthase (NOS) inhibitors AGH (aminoguani- dine hemisulfate) and SMIS (S-methylisothiourea sulfate) at concentrations of about 100 -1000 mol l1 and 50 -200 mol l1, respectively. Metamorphosis was not, however, induced by the NOS inhibitor L-NAME

JAN A. PECHENIK; DAVID E. COCHRANE; WEI LI; EMILY T. WEST; ANTHONY PIRES; MAIA LEPPO

2007-01-01

131

Photoperiodic modulation of metamorphosis in Atlantic halibut ( Hippoglossus hippoglossus L.)  

Microsoft Academic Search

The effect of abrupt changes in photoperiod on induction of metamorphosis in Atlantic halibut was investigated. Larvae were reared in a 3.7-m3 tank on enriched brine shrimp (Artemia) from first feeding at 265 day degrees (d°C) (44 days post hatch, DPH) until 66 days (DPH) under continuous illumination or to a standard length of 17 mm corresponding to the beginning

J. S. Solbakken; K. Pittman

2004-01-01

132

Dicapryloylglycerol and ammonium ions induce metamorphosis of ascidian larvae  

Microsoft Academic Search

Larvae of the tunicate Ciona start metamorphosis between some hours and a few days after hatching. Several substances were found to reduce this time span, such as vital dyes [Cloney (1961) Am Zool 1:67–87; Hirani (1961) Bull Mar Biol Stn Asamushi 11:121–125], heavy-metal ions including copper [see review by Lynch (1961) Am Zool 1:59–66] and the hormone thyroxine [Patricolo et

Stefan Berking; Klaus Herrmann

1990-01-01

133

Subtype-specific neuronal remodeling during Drosophila metamorphosis  

PubMed Central

During metamorphosis in holometabolous insects, the nervous system undergoes dramatic remodeling as it transitions from its larval to its adult form. Many neurons are generated through post-embryonic neurogenesis to have adult-specific roles, but perhaps more striking is the dramatic remodeling that occurs to transition neurons from functioning in the larval to the adult nervous system. These neurons exhibit a remarkable degree of plasticity during this transition; many subsets undergo programmed cell death, others remodel their axonal and dendritic arbors extensively, whereas others undergo trans-differentiation to alter their terminal differentiation gene expression profiles. Yet other neurons appear to be developmentally frozen in an immature state throughout larval life, to be awakened at metamorphosis by a process we term temporally-tuned differentiation. These multiple forms of remodeling arise from subtype-specific responses to a single metamorphic trigger, ecdysone. Here, we discuss recent progress in Drosophila melanogaster that is shedding light on how subtype-specific programs of neuronal remodeling are generated during metamorphosis.

Veverytsa, Lyubov; Allan, Douglas W.

2013-01-01

134

Cartilage on the move: cartilage lineage tracing during tadpole metamorphosis.  

PubMed

The reorganization of cranial cartilages during tadpole metamorphosis is a set of complex processes. The fates of larval cartilage-forming cells (chondrocytes) and sources of adult chondrocytes are largely unknown. Individual larval cranial cartilages may either degenerate or remodel, while many adult cartilages appear to form de novo during metamorphosis. Determining the extent to which adult chondrocytes/cartilages are derived from larval chondrocytes during metamorphosis requires new techniques in chondrocyte lineage tracing. We have developed two transgenic systems to label cartilage cells throughout the body with fluorescent proteins. One system strongly labels early tadpole cartilages only. The other system inducibly labels forming cartilages at any developmental stage. We examined cartilages of the skull (viscero- and neurocranium), and identified larval cartilages that either resorb or remodel into adult cartilages. Our data show that the adult otic capsules, tecti anterius and posterius, hyale, and portions of Meckel's cartilage are derived from larval chondrocytes. Our data also suggest that most adult cartilages form de novo, though we cannot rule out the potential for extreme larval chondrocyte proliferation or de- and re-differentiation, which could dilute our fluorescent protein signal. The transgenic lineage tracing strategies developed here are the first examples of inducible, skeleton-specific, lineage tracing in Xenopus. PMID:23036161

Kerney, Ryan R; Brittain, Alison L; Hall, Brian K; Buchholz, Daniel R

2012-10-01

135

Cartilage on the Move: Cartilage Lineage Tracing During Tadpole Metamorphosis  

PubMed Central

The reorganization of cranial cartilages during tadpole metamorphosis is a set of complex processes. The fates of larval cartilage-forming cells (chondrocytes) and sources of adult chondrocytes are largely unknown. Individual larval cranial cartilages may either degenerate or remodel, while many adult cartilages appear to form de novo during metamorphosis. Determining the extent to which adult chondrocytes/cartilages are derived from larval chondrocytes during metamorphosis requires new techniques in chondrocyte lineage tracing. We have developed two transgenic systems to label cartilage cells throughout the body with fluorescent proteins. One system strongly labels early tadpole cartilages only. The other system inducibly labels forming cartilages at any developmental stage. We examined cartilages of the skull (viscero- and neurocranium), and identified larval cartilages that either resorb or remodel into adult cartilages. Our data show that the adult otic capsules, tecti anterius and posterius, hyale, and portions of Meckel’s cartilage are derived from larval chondrocytes. Our data also suggest that most adult cartilages form de novo, though we cannot rule out the potential for extreme larval chondrocyte proliferation or de- and re-differentiation, which could dilute our fluorescent protein signal. The transgenic lineage tracing strategies developed here are the first examples of inducible, skeleton-specific, lineage tracing in Xenopus.

Kerney, Ryan R.; Brittain, Alison L.; Hall, Brian K.; Buchholz, Daniel R.

2012-01-01

136

Amphibians, Reptiles and Turtles of the Cimarron National Grassland, Kansas.  

National Technical Information Service (NTIS)

Since the appearance of of Reptiles and amphibians of the Cimarron National Grassland, Mortoll County, Kansas (Collins and Collins, 1991), new information has accumulated on the diversity, distribution and biology of amphibians, reptiles, and turtles nati...

J. T. Collins S. L. Collins T. W. Taggart

2011-01-01

137

The Decline of Amphibians in California's Great Central Valley  

Microsoft Academic Search

Declines in amphibian populations are rarely reported on the community or ecosystem level. We combined broad-scale field sampling with historical analyses of museum records to quantify amphibian de- clines in California's Great Central Valley. Overall, amphibians showed an unambiguous pattern of decline, although the intensity of decline varied both geographically and taxonomically. The greatest geographical de- cline was detected in

Robert N. Fisher; H. Bradley Shaffer

1996-01-01

138

THE LETHAL IMPACT OF ROUNDUP ON AQUATIC AND TERRESTRIAL AMPHIBIANS  

Microsoft Academic Search

The global decline in amphibian diversity has become an international en- vironmental problem with a multitude of possible causes. There is evidence that pesticides may play a role, yet few pesticides have been tested on amphibians. For example, Roundup is a globally common herbicide that is conventionally thought to be nonlethal to amphibians. However, Roundup has been tested on few

Rick A. Relyea

2005-01-01

139

Amphibian monitoring in the Atchafalaya Basin  

USGS Publications Warehouse

Amphibians are a diverse group of animals that includes frogs, toads, and salamanders. They are adapted to living in a variety of habitats, but most require water for at least one life stage. Amphibians have recently become a worldwide conservation concern because of declines and extinctions even in remote protected areas previously thought to be safe from the pressures of habitat loss and degradation. Amphibians are an important part of ecosystem dynamics because they can be quite abundant and serve both as a predator of smaller organisms and as prey to a suite of vertebrate predators. Their permeable skin and aquatic life history also make them useful as indicators of ecosystem health. Since 2002, the U.S. Geological Survey has been studying the frog and toad species inhabiting the Atchafalaya Basin to monitor for population declines and to better understand how the species are potentially affected by disease, environmental contaminants, and climate change.

Waddle, Hardin

2011-01-01

140

North American Reporting Center for Amphibian Malformations  

NSDL National Science Digital Library

Created in June, 1997 and funded by the US Geological Survey and Environmental Protection Agency, this site is a response to the discovery of numerous deformed amphibians (mostly frogs) in areas as widespread as Minnesota, California, and Florida. Malformations include extra or missing limbs, missing eyes, and split limbs. The site is intended to serve as a central repository for data on the type and relative frequency of such malformations throughout the US. Researchers hope to use the site to help discover the cause(s) of these deformities. The site contains a map of where malformations have been reported, background on the occurrence and possible causes of defects, numerous images of malformed amphibians, a searchable bibliography, instructions on how to report the discovery of a malformed amphibian, and links to eight related web sites. NARCAM's site also contains a toll-free number for citizen reports.

Center., Northern P.

1997-01-01

141

Diversity and distribution of amphibians in Romania  

PubMed Central

Abstract Nineteen species of amphibians inhabit Romania, 9 of which reach their range limit on this territory. Based on published occurrence reports, museum collections and our own data we compiled a national database of amphibian occurrences. We georeferenced 26779 amphibian species occurrences, and performed an analysis of their spatial patterns, checking for hotspots and patterns of species richness. The results of spatial statistic analyses supported the idea of a biased sampling for Romania, with clear hotspots of increased sampling efforts. The sampling effort is biased towards species with high detectability, protected areas, and large cities. Future sampling efforts should be focused mostly on species with a high rarity score in order to accurately map their range. Our results are an important step in achieving the long-term goals of increasing the efficiency of conservation efforts and evaluating the species range shifts under climate change scenarios.

Cogalniceanu, Dan; Szekely, Paul; Samoila, Ciprian; Ruben, Iosif; Tudor, Marian; Plaiasu, Rodica; Stanescu, Florina; Rozylowicz, Laurentiu

2013-01-01

142

Emesis and Space Motion Sickness in Amphibians  

NASA Astrophysics Data System (ADS)

Amphibians possess the ability to vomit in response to a variety of stimuli that provoke emesis in mammals. Pharmacological studies have establish that the ejection of gastric contents and the basic mechanism for vomiting have been phylogenetically conserved among these tetrapods. As part of on-going comparative studies on emesis in vertebrates, we previously documented that some postmetamorphic anurans and salamander larvae experience motion-induced emesis when exposed to the provocative stimulus of parabolic aircraft flight. However, more recent experiments suggest that there are strict conditions for inducing emesis in amphibians exposed to parabolic flight and that amphibians are not as sensitive to this stimulus as mammals. Further studies on emesis in lower vertebrates may help us understand the processes that cause emesis in abnormal gravitational regimes

Naitoh, T.; Yamashita, M.; Izumi-Kurotani, A.; Takabatake, I.; Wassersug, R. J.

143

Repair of ultraviolet irradiation damage to a cytoplasmic component required for neural induction in the amphibian egg.  

PubMed Central

Localized ultraviolet irradiation of the amphibian egg destroys a cytoplasmic component that is required for neural induction. Destruction of that component severely diminishes the inducing capacity of the dorsal lip at gastrulation, as determined by embryological assays. Repair of the ultraviolet lesion can be achieved by replacing the dorsal lip of the irradiated embyro with a lip from an unirradiated embryo. Images

Chung, H M; Malacinski, G M

1975-01-01

144

USGS: Amphibian Research and Monitoring Initiative  

NSDL National Science Digital Library

The Amphibian Research and Monitoring Initiative (ARMI) was formed by the U.S. Geological Survey as a national program for amphibian conservation, research, and monitoring. The website provides background information about ARMI as well as sections on Monitoring, Research & Development, Regions & People, and Products. The Research & Development section includes information about ongoing efforts at national, regional, and local levels. The Products section links to an extensive list of publications (some of which are hyperlinked) including Journal Articles, Circulars, Reports, and more. The site also links to great resources like The ARMI Web Tool, and The ARMI National Atlas (reported on in NSDL Scout Report for the Life Sciences, May 30, 2003).

145

USGS: Amphibian Research and Monitoring Initiative  

NSDL National Science Digital Library

The Amphibian Research and Monitoring Initiative (ARMI) was formed by the U.S. Geological Survey as a national program for amphibian conservation, research, and monitoring. The website provides background information about ARMI as well as sections on Monitoring, Research & Development, Regions & People, and Products. The Research & Development section includes information about ongoing efforts at national, regional, and local levels. The Products section links to an extensive list of publications (some of which are hyperlinked) including Journal Articles, Circulars, Reports, and more. The site also links to great resources like The ARMI Web Tool, and The ARMI National Atlas (reported on in NSDL Scout Report for the Life Sciences, May 30, 2003).

2008-04-14

146

Helping Your Local Amphibians (HYLA): An Internet-based Amphibian Course for Educators.  

ERIC Educational Resources Information Center

Introduces an online zoology course that was offered primarily to upper elementary and middle school teachers in which teachers were expected to take action to help the local amphibian population. (Author/YDS)

Murphy, Tony P.

2001-01-01

147

The formation of synapses in amphibian striated muscle during development.  

PubMed Central

1. A study has been made of the formation of synapses in developing reinnervated and cross-reinnervated amphibian twitch muscles which receive either a focal (iliofibularis) or a distributed (sartorius) innervation from 'en plaque' nerve terminals using histological, ultrastructural and electrophysiological techniques. 2. During the development of the tadpole through metamorphosis to the adult frog, the sartorius myofibres increased in length at about twice the rate of the iliofibularis myofibres, due to a fast rate of growth at their insertions on to the pelvic tendon. 3. The short iliofibularis and sartorius myofibres of young tadpoles (800 mum long) possessed only a single synapse and the iliofibularis myofibres did not receive any further innervation during development. However the sartorius myofibres received further transient innervation on the new muscle laid down during development at the fast growing pelvic insertion, until the distance between the original synapse formed on the myofibres and the synapse at the pelvic end of the muscle was about 12 mm. 4. During development synapses possessed either skewed, multimodal, or unimodal m.e.p.p. amplitude-frequency distributions; the intervals between m.e.p.p.s. were not distributed randomly according to a Poisson process, as m.e.p.p.s. of similar amplitudes tended to be separated by very short intervals; the unit-size e.p.p. had a similar amplitude-frequency distribution as the m.e.p.p.s. if these had a unimodal distribution. 5. Reinnervation or cross-reinnervation of the sartorius and the iliofibularis muscles in adults or at a late stage of development simply reconstituted the normal focal and distributed innervation patterns of the muscles, as found in the control muscles of the contralateral and unoperated legs. 6. These observations on synapse formation in amphibia are consistent with the hypothesis that during development the axon making the initial synaptic contact on the muscle cells induces a property over a length of muscle membrane adjacent to this site which makes it refractory to synapse formation; thus during reinnervation or cross-reinnervation of adult muscles this refractory property constrains synapse formation to these sites. Images A B C Plate 2

Bennett, M R; Pettigrew, A G

1975-01-01

148

Physiological, behavioral and maternal factors that contribute to size variation in larval amphibian populations.  

PubMed

Size variance among similarly aged individuals within populations is a pattern common to many organisms that is a result of interactions between intrinsic and extrinsic traits of individuals. While genetic and maternal effects, as well as physiological and behavioral traits have been shown to contribute to size variation in animal populations, teasing apart the influence of such factors on individual growth rates remain a challenge. Furthermore, tracing the effects of these interactions across life stages and in shaping adult phenotypes also requires further exploration. In this study we investigated the relationship between genetics, hatching patterns, behaviors, neuroendocrine stress axis activity and variance in growth and metamorphosis among same-aged larval amphibians. Through parallel experiments we found that in the absence of conspecific interactions, hatch time and to a lesser extent egg clutch identity (i.e. genetics and maternal effects) influenced the propensity for growth and development in individual tadpoles and determined metamorphic traits. Within experimental groups we found that variance in growth rates was associated with size-dependent foraging behaviors and responses to food restriction. We also found an inverse relationship between glucocorticoid (GC) hormone levels and body mass and developmental stage among group-reared tadpoles, which suggests that GC expression plays a role in regulating differing within-population growth trajectories in response to density-dependent conditions. Taken together these findings suggest that factors that influence hatching conditions can have long-term effects on growth and development. These results also raise compelling questions regarding the extent to which maternal and genetic factors influence physiological and behavioral profiles in amphibians. PMID:24143188

Warne, Robin W; Kardon, Adam; Crespi, Erica J

2013-01-01

149

EVIDENCE FOR FIRST YEAR METAMORPHOSIS OF BULLFROGS IN AN EPHEMERAL POND  

EPA Science Inventory

It is widely accepted that bullfrog ( R catesbeiana) tadpoles in the Pacific Northwest require more than one year for metamorphosis. Often time to metamorphosis increases along a latitudinal gradient. During our pond surveys at the EE Wilson Reserve, we found evidence of first ...

150

Growth and Partial Metamorphosis of Imaginal Disks of the Greater Wax Moth, Galleria mellonella, in vitro  

Microsoft Academic Search

THE most important of the problems of insect metamorphosis is the nature of the action of ecdysone. There is a particular lack of knowledge of the stages between the initiation of metamorphosis by ecdysone and the final differentiation into the adult. Experiments on the action of pure ecdysone in vitro have been conducted with systems which respond in a limited

H. Oberlander; L. Fulco

1967-01-01

151

Soak It Up: Understanding Amphibian Permeability  

NSDL National Science Digital Library

In this activity, learners will discover how the thin layers of amphibians' skin allow water and other chemicals to pass through it. Learners will also discover how different body coverings affect permeability. Learn why and how this affects their body, and what you can do to protect them in the wild. Thin skin is in, dirty environments are not!

Aquariums, Association O.

2009-01-01

152

Reproduction and Larval Rearing of Amphibians  

Microsoft Academic Search

Reproduction technologies for amphibians are increasingly used for the in vitro treatment of ovulation, spermiation, oocytes, eggs, sperm, and larvae. Recent advances in these reproduction technologies have been driven by (1) difficul- ties with achieving reliable reproduction of threatened spe- cies in captive breeding programs, (2) the need for the efficient reproduction of laboratory model species, and (3) the cost

Robert K. Browne; Kevin Zippel

153

Migration and orientation in anuran amphibians  

Microsoft Academic Search

In anuran amphibians migratory behaviour is constrained by the demands of water balance and thermoregulation. Therefore, the migratory range of anurans amounts to 15 km at most. Adult anurans perform migrations, if important habitat resources (e.g. sites for reproduction, nutrition and hibernation) are spatially separated. Site fidelity to these spatial units is a common feature of most anurans. These general

Ulrich Sinsch

1990-01-01

154

Decline of a Tropical Montane Amphibian Fauna  

Microsoft Academic Search

On the basis of surveys conducted between 1991 and 1996, I report a decline of the amphibian fauna at Las Tablas, Puntarenas Province, Costa Rica. I propose that the reduction in the abundance of Atelo- pus chiriquiensis and Hyla calypsa , the presence of dead and dying individuals of six species of frogs and sala- manders, and changes in population

Karen R. Lips

1998-01-01

155

POTENTIAL DEVELOPMENTAL EFFECTS OF ATRAZINE ON AMPHIBIANS  

EPA Science Inventory

Recent research has generated conflicting results on the effects of atrazine on gonadal developmental (e.g., male hermaphroditism) in amphibians and how these effects influence secondary sexual characteristics (e.g., laryngeal muscle mass). The SAP is being asked to consider the...

156

Emerging Infectious Diseases and Amphibian Population Declines  

Microsoft Academic Search

We review recent research on the pathology, ecology, and biogeography of two emerging infectious wildlife diseases, chytridiomycosis and ranaviral disease, in the context of host-parasite population biology. We examine the role of these diseases in the global decline of amphibian populations and propose hypotheses for the origins and impact of these panzootics. Finally, we discuss emerging infectious diseases as a

Peter Daszak; Lee Berger; Andrew A. Cunningham; Alex D. Hyatt; D. Earl Green; Rick Speare

1999-01-01

157

Otoacoustic Emissions in Amphibians, Lepidosaurs, and Archosaurs  

Microsoft Academic Search

1. General Introduction Some of the earliest work on otoacoustic emissions (OAEs) was carried out on amphibians (Palmer and Wilson 1982), establishing right at the beginning of studies of this phenomenon that it is not exclusively the province of mammals. During the 1980s and 1990s, a good deal of work on frogs, lizards, and birds established the almost ubiquitous presence

Geoffrey A. Manley; Pim van Dijk

158

Culture of Cells from Amphibian Embryos.  

ERIC Educational Resources Information Center

Describes a method for in vitro culturing of cells from amphibian early embryos. Such cells can be used to demonstrate such properties of eukaryote cells as cell motility, adhesion, differentiation, and cell sorting into tissues. The technique may be extended to investigate other factors. (Author/JN)

Stanisstreet, Martin

1983-01-01

159

The First Fossil Record of Caecilian Amphibians  

Microsoft Academic Search

THREE groups of amphibians are living today-frogs, salamanders and caecilians. The fossil record of frogs and salamanders is relatively poor1,2, but representatives of most groups have been discovered. For the caecilians, however, no authentic fossils have been recognized, until now. We describe here a single diagnostic vertebra from the Palaeocene of Brazil.

Richard Estes; MARVALEE H. WAKE

1972-01-01

160

Metabolomic insights into system-wide coordination of vertebrate metamorphosis  

PubMed Central

Background After completion of embryogenesis, many organisms experience an additional obligatory developmental transition to attain a substantially different juvenile or adult form. During anuran metamorphosis, the aquatic tadpole undergoes drastic morphological changes and remodelling of tissues and organs to become a froglet. Thyroid hormones are required to initiate the process, but the mechanism whereby the many requisite changes are coordinated between organs and tissues is poorly understood. Metabolites are often highly conserved biomolecules between species and are the closest reflection of phenotype. Due to the extensive distribution of blood throughout the organism, examination of the metabolites contained therein provides a system-wide overview of the coordinated changes experienced during metamorphosis. We performed an untargeted metabolomic analysis on serum samples from naturally-metamorphosing Rana catesbeiana from tadpoles to froglets using ultraperformance liquid chromatography coupled to a mass spectrometer. Total and aqueous metabolite extracts were obtained from each serum sample to select for nonpolar and polar metabolites, respectively, and selected metabolites were validated by running authentic compounds. Results The majority of the detected metabolites (74%) showed statistically significant abundance changes (padj?metamorphosis identifying fundamental pathways involved in the coordination of this important developmental process and paves the way for metabolomic studies on other metamorphic systems including fish and insects.

2014-01-01

161

Diseases of amphibian eggs and embryos  

USGS Publications Warehouse

Amphibians generally are prolific egg producers. In tropical and semi-tropical regions, deposition of eggs may occur year-round or may coincide with rainy seasons, while in temperate regions, deposition of eggs usually occurs immediately after emergence from hibernation. Numbers of eggs produced by each species may vary from a few dozen to thousands. Accordingly, some eggs may be infertile and wastage of embryos is to be expected. Fertility, viability and decomposition of eggs and embryos must be considered before it is assumed that diseases are present. An important consideration in the evaluation of egg masses is the fact that some will contain infertile and non-viable eggs. These infertile and nonviable eggs will undergo decomposition and they may appear similar to eggs that are infected by a pathogen. Evaluation of egg masses and embryos for the presence of disease may require repeated observations in a given breeding season as well as continued monitoring of egg masses during their growth and development and over successive breeding seasons. Amphibian eggs rarely are subjected to a comprehensive health (diagnostic) examination; hence, there is scant literature on the diseases of this life stage. Indeed, the eggs of some North American amphibians have yet to be described. Much basic physiology and normal biomedical baseline data on amphibian eggs is lacking. For example, it is known that the aquatic eggs of some species of shrimp quickly are coated by a protective and commensal bacterium that effectively impedes invasion of the eggs by other environmental organisms and potential pathogens. In the absence of this bacterium, shrimp eggs are rapidly killed by other bacteria and fungi (Green, 2001). The possibility that amphibian eggs also have important symbiotic or commensal bacteria needs to be investigated. Furthermore, the quantity and types of chemicals in the normal gelatinous capsules of amphibian eggs have scarcely been examined. Abnormalities of the female oviduct, either due to infectious disease, nutritional status, hormonal imbalances, or sublethal intoxications, could affect the quality of secreted gelatinous capsules on eggs, thus rendering an egg mass susceptible to other stressors. Diseases of amphibian eggs and embryos presented in this chapter are Lucke frog herpesvirus Ranavirus (iridovirus) infection Bacteria Watermold infection (saprolegniasis) Algae Microsporidia

Green, D. E.; Converse, K. A.

2005-01-01

162

Fibrodysplasia ossificans progressiva: mechanisms and models of skeletal metamorphosis  

PubMed Central

Fibrodysplasia ossificans progressiva (FOP; MIM #135100) is a debilitating genetic disorder of connective tissue metamorphosis. It is characterized by malformation of the great (big) toes during embryonic skeletal development and by progressive heterotopic endochondral ossification (HEO) postnatally, which leads to the formation of a second skeleton of heterotopic bone. Individuals with these classic clinical features of FOP have the identical heterozygous activating mutation (c.617G>A; R206H) in the gene encoding ACVR1 (also known as ALK2), a bone morphogenetic protein (BMP) type I receptor. Disease activity caused by this ACVR1 mutation also depends on altered cell and tissue physiology that can be best understood in the context of a high-fidelity animal model. Recently, we developed such a knock-in mouse model for FOP (Acvr1R206H/+) that recapitulates the human disease, and provides a valuable new tool for testing and developing effective therapies. The FOP knock-in mouse and other models in Drosophila, zebrafish, chickens and mice provide an arsenal of tools for understanding BMP signaling and addressing outstanding questions of disease mechanisms that are relevant not only to FOP but also to a wide variety of disorders associated with regenerative medicine and tissue metamorphosis.

Kaplan, Frederick S.; Chakkalakal, Salin A.; Shore, Eileen M.

2012-01-01

163

Fibrodysplasia ossificans progressiva: mechanisms and models of skeletal metamorphosis.  

PubMed

Fibrodysplasia ossificans progressiva (FOP; MIM #135100) is a debilitating genetic disorder of connective tissue metamorphosis. It is characterized by malformation of the great (big) toes during embryonic skeletal development and by progressive heterotopic endochondral ossification (HEO) postnatally, which leads to the formation of a second skeleton of heterotopic bone. Individuals with these classic clinical features of FOP have the identical heterozygous activating mutation (c.617G>A; R206H) in the gene encoding ACVR1 (also known as ALK2), a bone morphogenetic protein (BMP) type I receptor. Disease activity caused by this ACVR1 mutation also depends on altered cell and tissue physiology that can be best understood in the context of a high-fidelity animal model. Recently, we developed such a knock-in mouse model for FOP (Acvr1(R206H/+)) that recapitulates the human disease, and provides a valuable new tool for testing and developing effective therapies. The FOP knock-in mouse and other models in Drosophila, zebrafish, chickens and mice provide an arsenal of tools for understanding BMP signaling and addressing outstanding questions of disease mechanisms that are relevant not only to FOP but also to a wide variety of disorders associated with regenerative medicine and tissue metamorphosis. PMID:23115204

Kaplan, Frederick S; Chakkalakal, Salin A; Shore, Eileen M

2012-11-01

164

Embryonic multipotent progenitors remodel the Drosophila airways during metamorphosis  

PubMed Central

Adult structures in holometabolous insects such as Drosophila are generated by groups of imaginal cells dedicated to the formation of different organs. Imaginal cells are specified in the embryo and remain quiescent until the larval stages, when they proliferate and differentiate to form organs. The Drosophila tracheal system is extensively remodeled during metamorphosis by a small number of airway progenitors. Among these, the spiracular branch tracheoblasts are responsible for the generation of the pupal and adult abdominal airways. To understand the coordination of proliferation and differentiation during organogenesis of tubular organs, we analyzed the remodeling of Drosophila airways during metamorphosis. We show that the embryonic spiracular branch tracheoblasts are multipotent cells that express the homeobox transcription factor Cut, which is necessary for their survival and normal development. They give rise to three distinct cell populations at the end of larval development, which generate the adult tracheal tubes, the spiracle and the epidermis surrounding the spiracle. Our study establishes the series of events that lead to the formation of an adult tubular structure in Drosophila.

Pitsouli, Chrysoula; Perrimon, Norbert

2010-01-01

165

Detection of antibodies against iridoviruses in the serum of the amphibian Bufo marinus.  

PubMed

Sera from the amphibian Bufo marinus (cane or marine toad) were investigated using a newly-developed enzyme-linked immunosorbent assay for the detection of antibodies to ranaviruses (Family Iridoviridae). Epizootic haematopoietic necrosis virus (EHNV) or Bohle iridovirus (BIV) was affinity purified from cell culture supernatants and simultaneously bound to the solid phase using specific linker antibodies. After binding to antigen, antibodies in Bufo marinus serum were then detected with a specific anti-immunoglobulin reagent. Of 21 Bufo marinus sera, 3 contained antibodies against EHNV, BIV or related viruses in the ranavirus group, at titres greater than 3200. Reactivity of cane toad antibodies against BIV, an amphibian virus, was greater than that against similar concentrations of EHNV, a piscine virus. PMID:9395145

Whittington, R J; Kearns, C; Speare, R

1997-10-01

166

Changes in the role of the thyroid axis during metamorphosis of the Japanese eel, Anguilla japonica.  

PubMed

To clarify the role of thyroid function during metamorphosis from leptocephalus to glass eel in the Japanese eel, we examined the histology of the thyroid gland and measured whole-body concentrations of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), and thyroid stimulating hormone ?-subunit TSH (TSH?) mRNA expression levels in five stages of artificially hatched eels (leptocephalus, early-metamorphosis, late-metamorphosis, glass eel, and elver). During metamorphosis, the inner colloid of thyroid follicles showed positive immunoreactivity for T4, and both T4 and T3 levels were significantly increased, whereas a small peak of TSH? mRNA level was observed at the early-metamorphosis stage. Similarly, TSH? mRNA levels were highest in the glass eel stage, and then decreased markedly in the elver stage. In contrast to TSH? mRNA expression, thyroid hormones (both T4 and T3) increased further from the glass eel to elver stages. These results indicated that thyroid function in the Japanese eel was active both during and after metamorphosis. Therefore, the thyrotropic axis may play important roles not only in metamorphosis but also in subsequent inshore or upstream migrations. J. Exp. Zool. 321A: 357-364, 2014. © 2014 Wiley Periodicals, Inc. PMID:24692334

Sudo, Ryusuke; Okamura, Akihiro; Kuroki, Mari; Tsukamoto, Katsumi

2014-08-01

167

Effects of Delayed Metamorphosis on Larval Survival, Metamorphosis, and Juvenile Performance of Four Closely Related Species of Tropical Sea Urchins (Genus Echinometra)  

PubMed Central

We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22–24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10?rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis.

Rahman, M. Aminur; Yusoff, Fatimah Md.; Arshad, A.; Uehara, Tsuyoshi

2014-01-01

168

Effects of delayed metamorphosis on larval survival, metamorphosis, and juvenile performance of four closely related species of tropical sea urchins (genus Echinometra).  

PubMed

We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22-24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10 rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis. PMID:24624048

Rahman, M Aminur; Yusoff, Fatimah Md; Arshad, A; Uehara, Tsuyoshi

2014-01-01

169

North American Amphibian Monitoring Program (NAAMP)  

NSDL National Science Digital Library

The US Geological Survey's Patuxent Wildlife Research Center hosts this nice page on the North American Amphibian Monitoring Program. At the site, users will find an overview and history of the program, as well as regional program updates, educational information, and links to related sites. The heart of the site is the Monitoring Programs section, however, as it provides in-depth content on the surveys, including Calling Surveys, Terrestrial Salamander Monitoring, Aquatic Surveys, Atlassing, and Western Surveys. This easy-to-navigate site has much to offer, whether for volunteers interested in participating in surveys, researchers searching for in-depth sampling methodology, or anyone interested in learning more about the distribution and abundance of amphibians in North America.

170

Neurosteroid Biosynthesis in the Brain of Amphibians  

PubMed Central

Amphibians have been widely used to investigate the synthesis of biologically active steroids in the brain and the regulation of neurosteroid production by neurotransmitters and neuropeptides. The aim of the present review is to summarize the current knowledge regarding the neuroanatomical distribution and biochemical activity of steroidogenic enzymes in the brain of anurans and urodeles. The data accumulated over the past two decades demonstrate that discrete populations of neurons and/or glial cells in the frog and newt brains express the major steroidogenic enzymes and are able to synthesize de novo a number of neurosteroids from cholesterol/pregnenolone. Since neurosteroidogenesis has been conserved during evolution from amphibians to mammals, it appears that neurosteroids must play important physiological functions in the central nervous system of vertebrates.

Vaudry, Hubert; Do Rego, Jean-Luc; Burel, Delphine; Luu-The, Van; Pelletier, Georges; Vaudry, David; Tsutsui, Kazuyoshi

2011-01-01

171

Cooperative Amphibian Monitoring Protocol for the Greater Yellowstone Network Narrative, Version 1.0 Natural Resource.  

National Technical Information Service (NTIS)

This document describes a protocol for monitoring amphibians and amphibian breeding sites within John D. Rockefeller, Jr. Memorial Parkway (JORO), Grand Teton National Park (GRTE), and Yellowstone National Park (YELL). Amphibians were identified as a vita...

A. Ray C. Jean C. R. Peterson D. A. Patla R. Bennetts R. Daley S. Corn W. R. Gould

2013-01-01

172

Emerging infectious diseases and amphibian population declines.  

PubMed Central

We review recent research on the pathology, ecology, and biogeography of two emerging infectious wildlife diseases, chytridiomycosis and ranaviral disease, in the context of host-parasite population biology. We examine the role of these diseases in the global decline of amphibian populations and propose hypotheses for the origins and impact of these panzootics. Finally, we discuss emerging infectious diseases as a global threat to wildlife populations.

Daszak, P.; Berger, L.; Cunningham, A. A.; Hyatt, A. D.; Green, D. E.; Speare, R.

1999-01-01

173

Bent's Old Fort: Amphibians and Reptiles  

USGS Publications Warehouse

Bent's Old Fort National Historic Site sits along the Arkansas River in the semi-desert prairie of southeastern Colorado. The USGS provided assistance in designing surveys to assess the variety of herpetofauna (amphibians and reptiles) resident at this site. This brochure is the results of those efforts and provides visitors with information on what frogs, toads, snakes and salamanders might be seen and heard at Bent's Old Fort.

Muths, E.

2008-01-01

174

Amphibians as research models for regenerative medicine  

PubMed Central

The ability to regenerate bone across a critical size defect would be a marked clinical advance over current methods for dealing with such structural gaps. Here, we briefly review the development of limb bones and the mandible, the regeneration of urodele limbs after amputation, and present evidence that urodele and anuran amphibians represent a valuable research model for the study of segment defect regeneration in both limb bones and mandible.

Song, Fengyu; Li, Bingbing

2010-01-01

175

Amphibians as research models for regenerative medicine.  

PubMed

The ability to regenerate bone across a critical size defect would be a marked clinical advance over current methods for dealing with such structural gaps. Here, we briefly review the development of limb bones and the mandible, the regeneration of urodele limbs after amputation, and present evidence that urodele and anuran amphibians represent a valuable research model for the study of segment defect regeneration in both limb bones and mandible. PMID:21197215

Song, Fengyu; Li, Bingbing; Stocum, David L

2010-01-01

176

Luminaolide, a novel metamorphosis-enhancing macrodiolide for scleractinian coral larvae from crustose coralline algae  

PubMed Central

A new metamorphosis-enhancing macrodiolide, luminaolide (1), was isolated from the crustose coralline algae (CCA) Hydrolithon reinboldii. Its structure was determined by spectroscopic analysis. A fraction (1.30 ?g/mL) eluted with 80% aqueous MeOH by ODS gel column chromatography of the same CCA extract induced larval metamorphosis (25.9 ± 7.4%) against Leptastrea purpurea, and its metamorphosis-inducing activity was further enhanced to 92.6 ± 2.9% with the addition of 1 (25.6 ng/mL).

Kitamura, Makoto; Schupp, Peter J.; Nakano, Yoshikatsu; Uemura, Daisuke

2010-01-01

177

Reframing menstruation in India: metamorphosis of the menstrual taboo with the changing media coverage.  

PubMed

In this study I hypothesize metamorphosis of the menstrual taboo by examining the image and perception shifts of two social taboos-HIV/AIDS and homosexuality-from estranged taboos to embraced social issues. Trends identified in their media framing and respective image shifts were applied to menstruation in India. Based on my understanding of theory, topic, and geographical location, I construct a metamorphosis. I contribute the hypothesized final stage of metamorphosis, and explain how framing is likely instrumental in bringing about these changes. PMID:24180612

Yagnik, Arpan Shailesh

2014-06-01

178

Evolution of Ideas about Causes of Amphibian Deformities  

NSDL National Science Digital Library

This Issue focuses on a research article by Blaustein and Johnson (2003) that was published in Frontiers in Ecology and the Environment. The article discusses amphibian deformities, which may be related to a global decline in amphibians. By working with this paper and additional figures, students come to appreciate the complexity of biodiversity loss. Specifically, they gain an understanding of why scientists disagree about causes of amphibian limb deformities and why the search for a single factor is likely too simple.

D'Avanzo, Charlene

2010-02-16

179

Amphibian Decline: An Integrated Analysis of Multiple Stressor Effects  

USGS Publications Warehouse

Although the effects of contaminants on amphibians have been studied for decades, relatively little is known about these effects compared to the more intensively studied mammals. and birds. Science has advanced its understanding of the complexities linked to declining amphibian populations; however, there are many remaining questions whose answers would directly benefit amphibians and adaptive management plans ministering to them. In an effort to answer those questions and focus on ecological risk assessment of amphibians, scientists, researchers, and resource management professionals from diverse fields participated in a Society of Environmental Toxicology and Chemistry (SETAC)-Johnson Foundation Wingspread conference with three goals: characterize a process that would bring a range of interdisciplinary technical and management tools to the tasks of causal analysis; demonstrate the current state of available technical tools to assess amphibian populations exposed to various environmental stressors; and focus on identifying research that would likely benefit sustainable populations through adaptive management programs. A result of the Wingspread conference, Amphibian Decline examines the ecotoxicology and stressors of amphibians in an attempt to address issues related to declining amphibian populations and the role that various stressors might have in those losses. It identifies gaps in current data, interprets information into an existing framework, and points toward critical areas for future research. Through the combined efforts of research and resource management communities, recommendations can be developed to change current policies and management actions to address the problem of amphibian decline.

2003-01-01

180

Salamander Blue-sensitive Cones Lost During Metamorphosis  

PubMed Central

The tiger salamander lives in shallow water with bright light in the aquatic phase, and in dim tunnels or caves in the terrestrial phase. In the aquatic phase, there are five types of photoreceptors—two types of rods and three types of cones. Our previous studies showed that the green rods and blue-sensitive cones contain the same visual pigment and have the same absorbance spectra; however, the green rods have a larger photon-catch area and thus have higher light sensitivity than the blue-sensitive cones. Here we show that after metamorphosis, the terrestrial salamander looses the blue-sensitive cones, while the density of the green rods increases. Moreover, the size of the green rod outer segments is increased in the terrestrial phase, compared to that in the aquatic phase. This switch from the blue-sensitive cones to the green rods may represent an adaptation to the dim light environment of the terrestrial phase.

Chen, Ying; Znoiko, Sergey; DeGrip, Willem J.; Crouch, Rosalie K.; Ma, Jian-xing

2009-01-01

181

Centralspindlin is required for thorax development during Drosophila metamorphosis.  

PubMed

Epithelial morphogenesis is an essential process in all metazoans during both normal development and pathological processes such as wound healing. The coordinated regulation of cell shape, cell size, and cell adhesion during the migration of epithelial sheets ultimately gives rise to the diversity of body plans among different organisms as well as the diversity of cellular structures and tissues within an organism. Metamorphosis of the Drosophila pupa is an excellent system to study these transformative events. During pupal development, the cells of the wing imaginal discs migrate dorsally and fuse to form the adult thorax. Here I show centralspindlin, a protein complex well known for its role in cytokinesis, is essential for migration of wing disc cells and proper thorax closure. I show the subcellular localization of centralspindlin is important for its function in thorax development. This study demonstrates the emerging role of centralspindlin in regulating cell migration and cell adhesion in addition to its previously known function during cytokinesis. PMID:24700509

Sfregola, Michael

2014-05-01

182

Factors Affecting Larval Sea Lamprey Growth and Length at Metamorphosis in Lampricide-Treated Streams  

Microsoft Academic Search

Larval sea lampreys Petromyzon marinus in seven lampricide-treated streams were studied to assess the effects of density and abiotic factors on growth, length at metamorphosis, and age at metamorphosis. Support for density-dependent growth was not found in these streams. A linear relationship between total length and age was found for all populations. The daily growth of larvae in lampricide-treated streams

Ronald W. Griffiths; F. W. H. Beamish; B. J. Morrison; L. A. Barker

2001-01-01

183

Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut  

Microsoft Academic Search

Fish larval development, not least the spectacular process of flatfish metamorphosis, appears to be under complex endocrine\\u000a control, many aspects of which are still not fully elucidated. In order to obtain data on the functional development of two\\u000a major endocrine glands, the pituitary and the thyroid, during flatfish metamorphosis, histology, immunohistochemistry and\\u000a in situ hybridization techniques were applied on larvae

Ingibjörg Eir Einarsdóttir; Nadia Silva; Deborah M. Power; Heiddis Smáradóttir; Björn Thrandur Björnsson

2006-01-01

184

Nitric oxide acts as a positive regulator to induce metamorphosis of the ascidian Herdmania momus.  

PubMed

Marine invertebrates commonly have a biphasic life cycle in which the metamorphic transition from a pelagic larva to a benthic post-larva is mediated by the nitric oxide signalling pathway. Nitric oxide (NO) is synthesised by nitric oxide synthase (NOS), which is a client protein of the molecular chaperon heat shock protein 90 (HSP90). It is notable, then, that both NO and HSP90 have been implicated in regulating metamorphosis in marine invertebrates as diverse as urochordates, echinoderms, molluscs, annelids, and crustaceans. Specifically, the suppression of NOS activity by the application of either NOS- or HSP90-inhibiting pharmacological agents has been shown consistently to induce the initiation of metamorphosis, leading to the hypothesis that a negative regulatory role of NO is widely conserved in biphasic life cycles. Further, the induction of metamorphosis by heat-shock has been demonstrated for multiple species. Here, we investigate the regulatory role of NO in induction of metamorphosis of the solitary tropical ascidian, Herdmania momus. By coupling pharmacological treatments with analysis of HmNOS and HmHSP90 gene expression, we present compelling evidence of a positive regulatory role for NO in metamorphosis of this species, in contrast to all existing ascidian data that supports the hypothesis of NO as a conserved negative regulator of metamorphosis. The exposure of competent H. momus larvae to a NOS inhibitor or an NO donor results in an up-regulation of NOS and HSP90 genes. Heat shock of competent larvae induces metamorphosis in a temperature dependent manner, up to a thermal tolerance that approaches 35°C. Both larval/post-larval survival and the appearance of abnormal morphologies in H. momus post-larvae reflect the magnitude of up-regulation of the HSP90 gene in response to heat-shock. The demonstrated role of NO as a positive metamorphic regulator in H. momus suggests the existence of inter-specific adaptations of NO regulation in ascidian metamorphosis. PMID:24019877

Ueda, Nobuo; Degnan, Sandie M

2013-01-01

185

Species Review of Amphibian Extinction Risks in Madagascar: Conclusions from the Global Amphibian Assessment  

Microsoft Academic Search

We assessed the extinction risks of Malagasy amphibians by evaluating their distribution, occur- rence in protected areas, population trends, habitat quality, and prevalence in commercial trade. We estimated and mapped the distribution of each of the 220 described Malagasy species and applied, for the first time, the IUCN Red List categories and criteria to all species described at the time

FRANCO ANDREONE; JOHN E. CADLE; NEIL COX; FRANK GLAW; RONALD A. NUSSBAUM; CHRISTOPHER J. RAXWORTHY; SIMON N. STUART; DENIS VALLAN; MIGUEL VENCES

2005-01-01

186

Population Declines and Priorities for Amphibian Conservation in Latin America  

Microsoft Academic Search

Although dramatic amphibian population declines have been reported worldwide, our under- standing of the extent of the declines in Latin America, where amphibian diversity is high, is limited to a few well-documented studies. To better understand the geographic extent of declines, their possible causes, and the measures needed to improve Latin American scientists' ability to research the phenomenon and make

Bruce E. Young; Karen R. Lips; Jamie K. Reaser; Roberto Ibanez; Antonio W. Salas; J. Rogelio Cedeno; Luis A. Coloma; Santiago Ron; Enrique La Marca; John R. Meyer; Antonio Munoz; Federico Bolanos; Gerardo Chaves; David Romo

2001-01-01

187

Distribution of woodland amphibians along a forest fragmentation gradient  

Microsoft Academic Search

Understanding how changes in land-use affect the distribution and abundance of organisms is an increasingly important question in landscape ecology. Amphibians may be especially prone to local extinction resulting from human-caused transformation and fragmentation of their habitats owing to the spatially and temporally dynamic nature of their populations. In this study, distributions of five species of woodland amphibians with differing

James P. Gibbs

1998-01-01

188

Ultraviolet radiation, toxic chemicals and amphibian population declines  

Microsoft Academic Search

As part of an overall 'biodiversity crisis', many amphibian populations are in decline throughout the world. Numerous factors have contributed to these declines, including habitat destruction, pathogens, increasing ultraviolet (UV) radiation, introduced non-native species and contaminants. In this paper we review the contribution of increasing UV radiation and environmental contamination to the global decline of amphibian populations. Both UV radiation

Andrew R. Blaustein; John M. Romansic; Joseph M. Kiesecker; Audrey C. Hatch

2003-01-01

189

MOJAVE DESERT SPRING: THE AMPHIBIAN POINT OF VIEW  

EPA Science Inventory

Numerous springs are scattered throughout the eastern Mojave Desert, most of which are concentrated near the bases of mountain ranges. Spring-fed wetlands in this region comprise nearly all the available habitat for amphibians. We surveyed 128 springs for amphibians and habitat t...

190

Amphibian Declines and Environmental Change in the Eastern Mojave Desert  

Microsoft Academic Search

Eight amphibian taxa historically inhabited sparsely distributed wetlands in the Mojave Desert of western North America, habitats that have been dramatically altered or eliminated as a result of human activities. Changes in the distributions of these and two introduced amphibians, and associated environmental changes, are evaluated herein for an approximately 20,000 km2 area in the eastern Mojave Desert. Striking changes

David F. Bradford

191

Amphibian Oasis: Designing and Building a Schoolyard Pond.  

ERIC Educational Resources Information Center

Building a pond in a schoolyard is a rewarding way to help boost local populations of amphibians, to increase the natural value of school grounds, and to serve as a locale for observing the life cycles of plants, invertebrates, and amphibians. This article outlines important considerations in designing and building a pond from siting through…

Gosselin, Heather; Johnson, Bob

1996-01-01

192

Amphibians and Reptiles of the Lower West River  

Microsoft Academic Search

We surveyed West River Memorial Park in New Haven, Connecticut to determine which amphibian and reptile species are present within the park's available habitats and to assess the potential effects of salt marsh restoration on the herpeto- fauna. A variety of aquatic and terrestrial census methods were used. We recorded seven species of amphibians and reptiles, all of which are

W. Jay West; David K. Skelly

193

Population differentiation of temperate amphibians in unpredictable environments  

Microsoft Academic Search

Amphibians are a globally distributed and diverse lineage, but much of our current understanding of their population genetic structure comes from studies in mesic temperate habitats. We characterize the population genetic structure of two sympatric explosive breeding amphibians in the southwestern deserts of the United States: the Great Plains toad (Anaxyrus cognatus) and Couch's spadefoot toad (Scaphiopus couchii). For both

LAUREN M. CHAN; KELLY R. ZAMUDIO

2009-01-01

194

All about Amphibians. Animal Life for Children. [Videotape].  

ERIC Educational Resources Information Center

This videotape teaches children about their favorite amphibious creatures, as well as amphibians' nearest cousins--toads, newts, and salamanders. Young students discover how these amazing creatures can live both in and out of water, learn about the amphibious life cycle, and compare the differences between amphibians and reptiles. This videotape…

2000

195

AMPHIBIAN DECLINES AND ENVIRONMENTAL CHANGE IN THE EASTERN "MOJAVE DESERT"  

EPA Science Inventory

A number of amphibian species historically inhabited sparsely distributed wetlands in the Mojave Desert, USA, habitats that have been dramatically altered or eliminated as a result of human activities. The population status and distribution of amphibians were investigated in a 20...

196

Interacting symbionts and immunity in the amphibian skin mucosome predict disease risk and probiotic effectiveness.  

PubMed

Pathogenesis is strongly dependent on microbial context, but development of probiotic therapies has neglected the impact of ecological interactions. Dynamics among microbial communities, host immune responses, and environmental conditions may alter the effect of probiotics in human and veterinary medicine, agriculture and aquaculture, and the proposed treatment of emerging wildlife and zoonotic diseases such as those occurring on amphibians or vectored by mosquitoes. Here we use a holistic measure of amphibian mucosal defenses to test the effects of probiotic treatments and to assess disease risk under different ecological contexts. We developed a non-invasive assay for antifungal function of the skin mucosal ecosystem (mucosome function) integrating host immune factors and the microbial community as an alternative to pathogen exposure experiments. From approximately 8500 amphibians sampled across Europe, we compared field infection prevalence with mucosome function against the emerging fungal pathogen Batrachochytrium dendrobatidis. Four species were tested with laboratory exposure experiments, and a highly susceptible species, Alytes obstetricans, was treated with a variety of temperature and microbial conditions to test the effects of probiotic therapies and environmental conditions on mucosome function. We found that antifungal function of the amphibian skin mucosome predicts the prevalence of infection with the fungal pathogen in natural populations, and is linked to survival in laboratory exposure experiments. When altered by probiotic therapy, the mucosome increased antifungal capacity, while previous exposure to the pathogen was suppressive. In culture, antifungal properties of probiotics depended strongly on immunological and environmental context including temperature, competition, and pathogen presence. Functional changes in microbiota with shifts in temperature provide an alternative mechanistic explanation for patterns of disease susceptibility related to climate beyond direct impact on host or pathogen. This nonlethal management tool can be used to optimize and quickly assess the relative benefits of probiotic therapies under different climatic, microbial, or host conditions. PMID:24789229

Woodhams, Douglas C; Brandt, Hannelore; Baumgartner, Simone; Kielgast, Jos; Küpfer, Eliane; Tobler, Ursina; Davis, Leyla R; Schmidt, Benedikt R; Bel, Christian; Hodel, Sandro; Knight, Rob; McKenzie, Valerie

2014-01-01

197

Interacting Symbionts and Immunity in the Amphibian Skin Mucosome Predict Disease Risk and Probiotic Effectiveness  

PubMed Central

Pathogenesis is strongly dependent on microbial context, but development of probiotic therapies has neglected the impact of ecological interactions. Dynamics among microbial communities, host immune responses, and environmental conditions may alter the effect of probiotics in human and veterinary medicine, agriculture and aquaculture, and the proposed treatment of emerging wildlife and zoonotic diseases such as those occurring on amphibians or vectored by mosquitoes. Here we use a holistic measure of amphibian mucosal defenses to test the effects of probiotic treatments and to assess disease risk under different ecological contexts. We developed a non-invasive assay for antifungal function of the skin mucosal ecosystem (mucosome function) integrating host immune factors and the microbial community as an alternative to pathogen exposure experiments. From approximately 8500 amphibians sampled across Europe, we compared field infection prevalence with mucosome function against the emerging fungal pathogen Batrachochytrium dendrobatidis. Four species were tested with laboratory exposure experiments, and a highly susceptible species, Alytes obstetricans, was treated with a variety of temperature and microbial conditions to test the effects of probiotic therapies and environmental conditions on mucosome function. We found that antifungal function of the amphibian skin mucosome predicts the prevalence of infection with the fungal pathogen in natural populations, and is linked to survival in laboratory exposure experiments. When altered by probiotic therapy, the mucosome increased antifungal capacity, while previous exposure to the pathogen was suppressive. In culture, antifungal properties of probiotics depended strongly on immunological and environmental context including temperature, competition, and pathogen presence. Functional changes in microbiota with shifts in temperature provide an alternative mechanistic explanation for patterns of disease susceptibility related to climate beyond direct impact on host or pathogen. This nonlethal management tool can be used to optimize and quickly assess the relative benefits of probiotic therapies under different climatic, microbial, or host conditions.

Woodhams, Douglas C.; Brandt, Hannelore; Baumgartner, Simone; Kielgast, Jos; Kupfer, Eliane; Tobler, Ursina; Davis, Leyla R.; Schmidt, Benedikt R.; Bel, Christian; Hodel, Sandro; Knight, Rob; McKenzie, Valerie

2014-01-01

198

Late Cretaceous Vicariance in Gondwanan Amphibians  

PubMed Central

Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions.

Bocxlaer, Ines Van; Roelants, Kim; Biju, S.D.; Nagaraju, J.; Bossuyt, Franky

2006-01-01

199

The First Gene-encoded Amphibian Neurotoxin*  

PubMed Central

Many gene-encoded neurotoxins with various functions have been discovered in fish, reptiles, and mammals. A novel 60-residue neurotoxin peptide (anntoxin) that inhibited tetrodotoxin-sensitive (TTX-S) voltage-gated sodium channel (VGSC) was purified and characterized from the skin secretions of the tree frog Hyla annectans (Jerdon). This is the first gene-encoded neurotoxin found in amphibians. The IC50 of anntoxin for the TTX-S channel was about 3.4 ?m. Anntoxin shares sequence homology with Kunitz-type toxins but contains only two of three highly conserved cysteine bridges, which are typically found in these small, basic neurotoxin modules, i.e. snake dendrotoxins. Anntoxin showed an inhibitory ability against trypsin with an inhibitory constant (Ki) of 0.025 ?m. Anntoxin was distributed in skin, brain, stomach, and liver with a concentration of 25, 7, 3, and 2 ?g/g wet tissue, respectively. H. annectans lives on trees or other plants for its entire life cycle, and its skin contains the largest amount of anntoxin, which possibly helps defend against various aggressors or predators. A low dose of anntoxin was found to induce lethal toxicity for several potential predators, including the insect, snake, bird, and mouse. The tissue distribution and functional properties of the current toxin may provide insights into the ecological adaptation of tree-living amphibians.

You, Dewen; Hong, Jing; Rong, Mingqiang; Yu, Haining; Liang, Songping; Ma, Yufang; Yang, Hailong; Wu, Jing; Lin, Donghai; Lai, Ren

2009-01-01

200

Vestibular lesion-induced developmental plasticity in spinal locomotor networks during Xenopus laevis metamorphosis.  

PubMed

During frog metamorphosis, the vestibular sensory system remains unchanged, while spinal motor networks undergo a massive restructuring associated with the transition from the larval to adult biomechanical system. We investigated in Xenopus laevis the impact of a pre- (tadpole stage) or post-metamorphosis (juvenile stage) unilateral labyrinthectomy (UL) on young adult swimming performance and underlying spinal locomotor circuitry. The acute disruptive effects on locomotion were similar in both tadpoles and juvenile frogs. However, animals that had metamorphosed with a preceding UL expressed restored swimming behavior at the juvenile stage, whereas animals lesioned after metamorphosis never recovered. Whilst kinematic and electrophysiological analyses of the propulsive system showed no significant differences in either juvenile group, a 3D biomechanical simulation suggested that an asymmetry in the dynamic control of posture during swimming could account for the behavioral restoration observed in animals that had been labyrinthectomized before metamorphosis. This hypothesis was subsequently supported by in vivo electromyography during free swimming and in vitro recordings from isolated brainstem/spinal cord preparations. Specifically, animals lesioned prior to metamorphosis at the larval stage exhibited an asymmetrical propulsion/posture coupling as a post-metamorphic young adult. This developmental alteration was accompanied by an ipsilesional decrease in propriospinal coordination that is normally established in strict left-right symmetry during metamorphosis in order to synchronize dorsal trunk muscle contractions with bilateral hindlimb extensions in the swimming adult. Our data thus suggest that a disequilibrium in descending vestibulospinal information during Xenopus metamorphosis leads to an altered assembly of adult spinal locomotor circuitry. This in turn enables an adaptive compensation for the dynamic postural asymmetry induced by the vestibular imbalance and the restoration of functionally-effective behavior. PMID:23951071

Beyeler, Anna; Rao, Guillaume; Ladepeche, Laurent; Jacques, André; Simmers, John; Le Ray, Didier

2013-01-01

201

Nitric oxide inhibits metamorphosis in larvae of Crepidula fornicata, the slippershell snail.  

PubMed

This paper concerns the role of nitric oxide (NO) in controlling metamorphosis in the marine gastropod Crepidula fornicata. Metamorphosis was stimulated by the nitric oxide synthase (NOS) inhibitors AGH (aminoguanidine hemisulfate) and SMIS (S-methylisothiourea sulfate) at concentrations of about 100-1000 micromol l(-1) and 50-200 micromol l(-1), respectively. Metamorphosis was not, however, induced by the NOS inhibitor l-NAME (l-N(G)-nitroarginine methyl ester) at even the highest concentration tested, 500 micromol l(-1). Moreover, pre-incubation with l-NAME at 20 and 80 micromol l(-1) did not increase the sensitivity of competent larvae to excess K(+), a potent inducer of metamorphosis in this species; we suggest that either l-NAME is ineffective in suppressing NO production in larvae of C. fornicata, or that it works only on the constitutive isoform of the enzyme. In contrast, metamorphosis was potentiated by the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3, -a]quinoxalin-1-one) in response to a natural metamorphic inducer derived from conspecific adults. Because NO typically stimulates cGMP production through the activation of soluble guanylate cyclase, this result supports the hypothesis that NO acts as an endogenous inhibitor of metamorphosis in C. fornicata. The expression of NOS, shown by immunohistochemical techniques, was detected in the apical ganglion of young larvae but not in older larvae, further supporting the hypothesis that metamorphosis in C. fornicata is made possible by declines in the endogenous concentration of NO during development. PMID:17928523

Pechenik, Jan A; Cochrane, David E; Li, Wei; West, Emily T; Pires, Anthony; Leppo, Maia

2007-10-01

202

The effect of larval age on morphology and gene expression during ascidian metamorphosis.  

PubMed

Metamorphosis is both an ecological and a developmental genetic transition that an organism undergoes as a normal part of ontogeny. Many organisms have the ability to delay metamorphosis when conditions are unsuitable. This strategy carries obvious benefits, but may also result in severe consequences for older larvae that run low on energy. In the marine environment, some lecithotrophic larvae that have prolonged periods in the plankton may begin forming postlarval and juvenile structures that normally do not appear until after settlement and the initiation of metamorphosis. This precocious activation of the postlarval developmental program may reflect an adaptation to increase the survival of older, energy-depleted larvae by allowing them to metamorphose more quickly. In the present study, we investigate morphological and genetic consequences of delay of metamorphosis in larvae of Herdmania momus (a solitary stolidobranch ascidian). We observe significant morphological and genetic changes during prolonged larval life, with older larvae displaying significant changes in RNA levels, precocious migration of mesenchyme cells, and changes in larval shape including shortening of the tail. While these observations suggest that the older H. momus larvae are functionally different from younger larvae and possibly becoming more predisposed to undergo metamorphosis, we did not find any significant differences in gene expression levels between postlarvae arising from larvae that metamorphosed as soon as they were competent and postlarvae developing from larvae that postponed metamorphosis. This recalibration, or convergence, of transcript levels in the early postlarva suggests that changes that occur during prolonged larval life of H. momus are not necessarily associated with early activation of adult organ differentiation. Instead, it suggests that an autonomous developmental program is activated in H. momus upon the induction of metamorphosis regardless of the history of the larva. PMID:21672783

Jacobs, Molly W; Degnan, Sandie M; Woods, Rick; Williams, Elizabeth; Roper, Kathrein E; Green, Kathryn; Degnan, Bernard M

2006-12-01

203

Nitrogen pollution: an assessment of its threat to amphibian survival.  

PubMed Central

The potential for nitrate to affect amphibian survival was evaluated by examining the areas in North America where concentrations of nitrate in water occur above amphibian toxicity thresholds. Nitrogen pollution from anthropogenic sources enters bodies of water through agricultural runoff or percolation associated with nitrogen fertilization, livestock, precipitation, and effluents from industrial and human wastes. Environmental concentrations of nitrate in watersheds throughout North America range from < 1 to > 100 mg/L. Of the 8,545 water quality samples collected from states and provinces bordering the Great Lakes, 19.8% contained nitrate concentrations exceeding those which can cause sublethal effects in amphibians. In the laboratory lethal and sublethal effects in amphibians are detected at nitrate concentrations between 2.5 and 100 mg/L. Furthermore, amphibian prey such as insects and predators of amphibians such as fish are also sensitive to these elevated levels of nitrate. From this we conclude that nitrate concentrations in some watersheds in North America are high enough to cause death and developmental anomalies in amphibians and impact other animals in aquatic ecosystems. In some situations, the use of vegetated buffer strips adjacent to water courses can reduce nitrogen contamination of surface waters. Ultimately, there is a need to reduce runoff, sewage effluent discharge, and the use of fertilizers, and to establish and enforce water quality guidelines for nitrate for the protection of aquatic organisms. Images Figure 1 Figure 2

Rouse, J D; Bishop, C A; Struger, J

1999-01-01

204

Shedding Light on Ultraviolet Radiation and Amphibian Embryos  

NSDL National Science Digital Library

This peer-reviewed article from BioScience journal is about the effects of UV radiation on amphibian population. The hypothesis that increasing ultraviolet-B (UVB) radiation is a causal factor in the decline of amphibian populations has received considerable attention in the scientific and public media. To evaluate the validity of this hypothesis, it is necessary to examine the natural environmental factors and biological traits of amphibians that protect them from UVB radiation. A careful reading of the literature reveals that most published studies on the effects of ambient UVB radiation on amphibian embryos have found no increased mortality. Those few reports that show harmful effects employ experimental methods that do not place enough importance on the natural abiotic and biotic factors that provide UVB protection. In the laboratory, amphibian embryos are resistant to doses of UVB radiation far higher than those they would normally receive from ambient sunlight. The jelly surrounding amphibian eggs absorbs UVB radiation, as revealed by spectral measurements of absorbance; after UVB exposure, embryos with their jelly capsules removed show significantly higher mortality than those with the jelly intact. In light of this and other factors mitigating UVB absorption, the hypothesis that ambient UVB radiation causes amphibian mortality and population declines is without support.

LAWRENCE E. LICHT (;)

2003-06-01

205

Metamorphosis of a butterfly-associated bacterial community.  

PubMed

Butterflies are charismatic insects that have long been a focus of biological research. They are also habitats for microorganisms, yet these microbial symbionts are little-studied, despite their likely importance to butterfly ecology and evolution. In particular, the diversity and composition of the microbial communities inhabiting adult butterflies remain uncharacterized, and it is unknown how the larval (caterpillar) and adult microbiota compare. To address these knowledge gaps, we used Illumina sequencing of 16S rRNA genes from internal bacterial communities associated with multiple life stages of the neotropical butterfly Heliconius erato. We found that the leaf-chewing larvae and nectar- and pollen-feeding adults of H. erato contain markedly distinct bacterial communities, a pattern presumably rooted in their distinct diets. Larvae and adult butterflies host relatively small and similar numbers of bacterial phylotypes, but few are common to both stages. The larval microbiota clearly simplifies and reorganizes during metamorphosis; thus, structural changes in a butterfly's bacterial community parallel those in its own morphology. We furthermore identify specific bacterial taxa that may mediate larval and adult feeding biology in Heliconius and other butterflies. Although male and female Heliconius adults differ in reproductive physiology and degree of pollen feeding, bacterial communities associated with H. erato are not sexually dimorphic. Lastly, we show that captive and wild individuals host different microbiota, a finding that may have important implications for the relevance of experimental studies using captive butterflies. PMID:24466308

Hammer, Tobin J; McMillan, W Owen; Fierer, Noah

2014-01-01

206

Cool Temperatures Reduce Antifungal Activity of Symbiotic Bacteria of Threatened Amphibians - Implications for Disease Management and Patterns of Decline  

PubMed Central

Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a widespread disease of amphibians responsible for population declines and extinctions. Some bacteria from amphibians’ skins produce antimicrobial substances active against Bd. Supplementing populations of these cutaneous antifungal bacteria might help manage chytridiomycosis in wild amphibians. However, the activity of protective bacteria may depend upon environmental conditions. Biocontrol of Bd in nature thus requires knowledge of how environmental conditions affect their anti-Bd activity. For example, Bd-driven amphibian declines have often occurred at temperatures below Bd’s optimum range. It is possible these declines occurred due to reduced anti-Bd activity of bacterial symbionts at cool temperatures. Better understanding of the effects of temperature on chytridiomycosis development could also improve risk evaluation for amphibian populations yet to encounter Bd. We characterized, at a range of temperatures approximating natural seasonal variation, the anti-Bd activity of bacterial symbionts from the skins of three species of rainforest tree frogs (Litoria nannotis, Litoria rheocola, and Litoria serrata). All three species declined during chytridiomycosis outbreaks in the late 1980s and early 1990s and have subsequently recovered to differing extents. We collected anti-Bd bacterial symbionts from frogs and cultured the bacteria at constant temperatures from 8°C to 33°C. Using a spectrophotometric assay, we monitored Bd growth in cell-free supernatants (CFSs) from each temperature treatment. CFSs from 11 of 24 bacteria showed reduced anti-Bd activity in vitro when they were produced at cool temperatures similar to those encountered by the host species during population declines. Reduced anti-Bd activity of metabolites produced at low temperatures may, therefore, partially explain the association between Bd-driven declines and cool temperatures. We show that to avoid inconsistent antifungal activity, bacteria evaluated for use in chytridiomycosis biocontrol should be tested over a range of environmental temperatures spanning those likely to be encountered in the field.

Daskin, Joshua H.; Bell, Sara C.; Schwarzkopf, Lin; Alford, Ross A.

2014-01-01

207

ASSESSMENT OF THE RISK OF SOLAR ULTRAVIOLET RADIATION TO AMPHIBIANS. II: IN SITU CHARACTERIZATION OF SOLAR ULTRAVIOLET RADIATION IN AMPHIBIAN HABITATS  

EPA Science Inventory

Ultraviolet B (UVB) radiation has been hypothesized as a potential cause of amphibian population declines and increased incidences of malformations. Realistic studies documenting UV irradiance or dose have rarely been conducted in wetlands used by amphibians. We demonstrate that ...

208

Amphibian fertilization and development in microgravity  

NASA Technical Reports Server (NTRS)

An experiment investigating the effects of gravity on embryonic development in amphibians is proposed. The planned procedures for the preparation of the frog eggs for launching in the Space Shuttle, for the injection of the eggs with gonadotropin, for the insertion of the eggs into egg chambers, for the storage of one of the chambers in a microgravity area and the second into a centrifuge, and for the fertilization of the eggs are described. The later organogenesis, swimming behavior, cytoplasmic components, cellular formation, neural plate and archenteron expansion, and allometry and expansion of the organ systems will be examined. Normal morphology for embryos and tadpoles developing at microgravity and the formation of the neural plate opposite the sperm entry point meridian are predicted.

Souza, K. A.; Black, S. D.

1985-01-01

209

Experimental induction of larval metamorphosis by a naturally-produced halogenated compound (dibromomethane) in the invasive mollusc Crepidula fornicata (L.)  

Microsoft Academic Search

In many marine benthic invertebrates, the larval stage is the main vector of dispersal. Selective metamorphosis of larvae into an appropriate habitat is then essential to the survival of the benthic adult, with profound implications for population dynamics. Within this context, the identification of causal external factors triggering larval metamorphosis is of primary interest. In the widely invasive marine species

Nicolas Taris; Thierry Comtet; Robin Stolba; Régis Lasbleiz; Jan A. Pechenik; Frédérique Viard

2010-01-01

210

Inhibitory function of nitric oxide on the onset of metamorphosis in competent larvae of Crepidula fornicata: A transcriptional perspective  

Microsoft Academic Search

In diverse invertebrate species characterized by a biphasic life cycle, metamorphosis represents a fundamental biological transition which determines the fate of benthic population dynamics through settlement and recruitment. Within this context, nitric oxide (NO) is thought to act as an endogenous inhibitor of metamorphosis. While attention has been focused on the mechanisms of this inhibitory pathway with pharmacological agents and

Nicolas Taris; Thierry Comtet; Frédérique Viard

2009-01-01

211

Wnt signaling promotes oral but suppresses aboral structures in Hydractinia metamorphosis and regeneration.  

PubMed

We studied the role of Wnt signaling in axis formation during metamorphosis and regeneration in the cnidarian Hydractinia. Activation of Wnt downstream events during metamorphosis resulted in a complete oralization of the animals and repression of aboral structures (i.e. stolons). The expression of Wnt3, Tcf and Brachyury was upregulated and became ubiquitous. Rescue experiments using Tcf RNAi resulted in normal metamorphosis and quantitatively normal Wnt3 and Brachyury expression. Isolated, decapitated polyps regenerated only heads but no stolons. Activation of Wnt downstream targets in regenerating animals resulted in oralization of the polyps. Knocking down Tcf or Wnt3 by RNAi inhibited head regeneration and resulted in complex phenotypes that included ectopic aboral structures. Multiple heads then grew when the RNAi effect had dissipated. Our results provide functional evidence that Wnt promotes head formation but represses the formation of stolons, whereas downregulation of Wnt promotes stolons and represses head formation. PMID:20685735

Duffy, David J; Plickert, Günter; Kuenzel, Timo; Tilmann, Wido; Frank, Uri

2010-09-01

212

Terrestrial Amphibians and Mollusks: Evaluation of an Integrated Survey Method.  

National Technical Information Service (NTIS)

We developed and evaluated an integrated sampling method to determine presence of terrestrial amphibian and mollusk species. Our goal was to be more efficient at locating both taxa during the same field surveys. Our protocol employed standardized Time (TC...

D. J. Major R. B. Bury

2004-01-01

213

Trends in amphibian occupancy in the United States.  

PubMed

Though a third of amphibian species worldwide are thought to be imperiled, existing assessments simply categorize extinction risk, providing little information on the rate of population losses. We conducted the first analysis of the rate of change in the probability that amphibians occupy ponds and other comparable habitat features across the United States. We found that overall occupancy by amphibians declined 3.7% annually from 2002 to 2011. Species that are Red-listed by the International Union for Conservation of Nature (IUCN) declined an average of 11.6% annually. All subsets of data examined had a declining trend including species in the IUCN Least Concern category. This analysis suggests that amphibian declines may be more widespread and severe than previously realized. PMID:23717602

Adams, Michael J; Miller, David A W; Muths, Erin; Corn, Paul Stephen; Grant, Evan H Campbell; Bailey, Larissa L; Fellers, Gary M; Fisher, Robert N; Sadinski, Walter J; Waddle, Hardin; Walls, Susan C

2013-01-01

214

Trends in Amphibian Occupancy in the United States  

PubMed Central

Though a third of amphibian species worldwide are thought to be imperiled, existing assessments simply categorize extinction risk, providing little information on the rate of population losses. We conducted the first analysis of the rate of change in the probability that amphibians occupy ponds and other comparable habitat features across the United States. We found that overall occupancy by amphibians declined 3.7% annually from 2002 to 2011. Species that are Red-listed by the International Union for Conservation of Nature (IUCN) declined an average of 11.6% annually. All subsets of data examined had a declining trend including species in the IUCN Least Concern category. This analysis suggests that amphibian declines may be more widespread and severe than previously realized.

Adams, Michael J.; Miller, David A. W.; Muths, Erin; Corn, Paul Stephen; Grant, Evan H. Campbell; Bailey, Larissa L.; Fellers, Gary M.; Fisher, Robert N.; Sadinski, Walter J.; Waddle, Hardin; Walls, Susan C.

2013-01-01

215

ALIEN SPECIES: THEIR ROLE IN AMPHIBIAN POPULATION DECLINES AND RESTORATION  

EPA Science Inventory

Alien species (also referred to as exotic, invasive, introduced, or normative species) have been implicated as causal agents in population declines of many amphibian species. Herein, we evaluate the relative contributions of alien species and other factors in adversely affecting ...

216

Reptiles and Amphibians of Fairchild Air Force Base, WA.  

National Technical Information Service (NTIS)

Many reptile and amphibian (collectively termed 'herpetofauna') populations are declining at a precipitous rate. Globally, nearly 30% of herpetofauna are considered endangered or at risk of extinction. Department of Defense (DoD) installations likely serv...

J. H. Sperry

2013-01-01

217

Regulation of Drosophila metamorphosis by xenobiotic response regulators.  

PubMed

Mammalian Nrf2-Keap1 and the homologous Drosophila CncC-dKeap1 protein complexes regulate both transcriptional responses to xenobiotic compounds as well as native cellular and developmental processes. The relationships between the functions of these proteins in xenobiotic responses and in development were unknown. We investigated the genes regulated by CncC and dKeap1 during development and the signal transduction pathways that modulate their functions. CncC and dKeap1 were enriched within the nuclei in many tissues, in contrast to the reported cytoplasmic localization of Keap1 and Nrf2 in cultured mammalian cells. CncC and dKeap1 occupied ecdysone-regulated early puffs on polytene chromosomes. Depletion of either CncC or dKeap1 in salivary glands selectively reduced early puff gene transcription. CncC and dKeap1 depletion in the prothoracic gland as well as cncC(K6/K6) and dKeap1(EY5/EY5) loss of function mutations in embryos reduced ecdysone-biosynthetic gene transcription. In contrast, dKeap1 depletion and the dKeap1(EY5/EY5) loss of function mutation enhanced xenobiotic response gene transcription in larvae and embryos, respectively. Depletion of CncC or dKeap1 in the prothoracic gland delayed pupation by decreasing larval ecdysteroid levels. CncC depletion suppressed the premature pupation and developmental arrest caused by constitutive Ras signaling in the prothoracic gland; conversely, constitutive Ras signaling altered the loci occupied by CncC on polytene chromosomes and activated transcription of genes at these loci. The effects of CncC and dKeap1 on both ecdysone-biosynthetic and ecdysone-regulated gene transcription, and the roles of CncC in Ras signaling in the prothoracic gland, establish the functions of these proteins in the neuroendocrine axis that coordinates insect metamorphosis. PMID:23408904

Deng, Huai; Kerppola, Tom K

2013-01-01

218

The effect of pinealectomy, continuous light, and continuous darkness on metamorphosis of anadromous sea lampreys, Petromyzon marinus L  

SciTech Connect

The role of the pineal complex in lamprey metamorphosis was investigated by examining the influence of pinealectomy and continuous light and darkness on the initiation of this event in anadromous sea lampreys, Petromyzon marinus L. Larval lampreys, which on the basis of a condition factor were considered likely to enter metamorphosis in July, were separated in May of 1979 and 1980 into the following groups: (1) intact controls, (2) sham-operated controls, (3) pinealectomized individuals, (4) those exposed to continuous light, and (5) those exposed to continuous light or dark. The importance of the pineal complex to metamorphosis was supported by morphological evidence that, in all presumably pinealectomized individuals that entered metamorphosis, the complex had apparently not been removed during the surgical procedure. The ways in which the pineal complex may be involved in lamprey metamorphosis are discussed.

Cole, W.C.; Youson, J.H.

1981-12-01

219

Phosphoproteome analysis during larval development and metamorphosis in the spionid polychaete Pseudopolydora vexillosa  

PubMed Central

Background The metamorphosis of the spionid polychaete Pseudopolydora vexillosa includes spontaneous settlement onto soft-bottom habitats and morphogenesis that can be completed in a very short time. A previous study on the total changes to the proteome during the various developmental stages of P. vexillosa suggested that little or no de novo protein synthesis occurs during metamorphosis. In this study, we used multicolor fluorescence detection of proteins in 2-D gels for differential analysis of proteins and phosphoproteins to reveal the dynamics of post-translational modification proteins in this species. A combination of affinity chromatography, 2D-PAGE, and mass spectrometry was used to identify the phosphoproteins in pre-competent larvae, competent larvae, and newly metamorphosed juveniles. Results We reproducibly detected 210, 492, and 172 phosphoproteins in pre-competent larvae, competent larvae, and newly metamorphosed juveniles, respectively. The highest percentage of phosphorylation was observed during the competent larval stage. About 64 stage-specific phosphoprotein spots were detected in the competent stage, and 32 phosphoproteins were found to be significantly differentially expressed in the three stages. We identified 38 phosphoproteins, 10 of which were differentially expressed during metamorphosis. These phosphoproteins belonged to six categories of biological processes: (1) development, (2) cell differentiation and integrity, (3) transcription and translation, (4) metabolism, (5) protein-protein interaction and proteolysis, and (6) receptors and enzymes. Conclusion This is the first study to report changes in phosphoprotein expression patterns during the metamorphosis of the marine polychaete P. vexillosa. The higher degree of phosphorylation during the process of attaining competence to settle and metamorphose may be due to fast morphological transitions regulated by various mechanisms. Our data are consistent with previous studies showing a high percentage of phosphorylation during competency in the barnacle Balanus amphitrite and the bryozoan Bugula neritina. The identified phosphoproteins may play an important role during metamorphosis, and further studies on the location and functions of important proteins during metamorphosis are warranted.

2011-01-01

220

Precocious Metamorphosis in the Juvenile Hormone-Deficient Mutant of the Silkworm, Bombyx mori  

PubMed Central

Insect molting and metamorphosis are intricately governed by two hormones, ecdysteroids and juvenile hormones (JHs). JHs prevent precocious metamorphosis and allow the larva to undergo multiple rounds of molting until it attains the proper size for metamorphosis. In the silkworm, Bombyx mori, several “moltinism” mutations have been identified that exhibit variations in the number of larval molts; however, none of them have been characterized molecularly. Here we report the identification and characterization of the gene responsible for the dimolting (mod) mutant that undergoes precocious metamorphosis with fewer larval–larval molts. We show that the mod mutation results in complete loss of JHs in the larval hemolymph and that the mutant phenotype can be rescued by topical application of a JH analog. We performed positional cloning of mod and found a null mutation in the cytochrome P450 gene CYP15C1 in the mod allele. We also demonstrated that CYP15C1 is specifically expressed in the corpus allatum, an endocrine organ that synthesizes and secretes JHs. Furthermore, a biochemical experiment showed that CYP15C1 epoxidizes farnesoic acid to JH acid in a highly stereospecific manner. Precocious metamorphosis of mod larvae was rescued when the wild-type allele of CYP15C1 was expressed in transgenic mod larvae using the GAL4/UAS system. Our data therefore reveal that CYP15C1 is the gene responsible for the mod mutation and is essential for JH biosynthesis. Remarkably, precocious larval–pupal transition in mod larvae does not occur in the first or second instar, suggesting that authentic epoxidized JHs are not essential in very young larvae of B. mori. Our identification of a JH–deficient mutant in this model insect will lead to a greater understanding of the molecular basis of the hormonal control of development and metamorphosis.

Daimon, Takaaki; Kozaki, Toshinori; Niwa, Ryusuke; Kobayashi, Isao; Furuta, Kenjiro; Namiki, Toshiki; Uchino, Keiro; Banno, Yutaka; Katsuma, Susumu; Tamura, Toshiki; Mita, Kazuei; Sezutsu, Hideki; Nakayama, Masayoshi; Itoyama, Kyo; Shimada, Toru; Shinoda, Tetsuro

2012-01-01

221

Somatic, germline and sex hierarchy regulated gene expression during Drosophila metamorphosis  

PubMed Central

Background Drosophila melanogaster undergoes a complete metamorphosis, during which time the larval male and female forms transition into sexually dimorphic, reproductive adult forms. To understand this complex morphogenetic process at a molecular-genetic level, whole genome microarray analyses were performed. Results The temporal gene expression patterns during metamorphosis were determined for all predicted genes, in both somatic and germline tissues of males and females separately. Temporal changes in transcript abundance for genes of known functions were found to correlate with known developmental processes that occur during metamorphosis. We find that large numbers of genes are sex-differentially expressed in both male and female germline tissues, and relatively few are sex-differentially expressed in somatic tissues. The majority of genes with somatic, sex-differential expression were found to be expressed in a stage-specific manner, suggesting that they mediate discrete developmental events. The Sex-lethal paralog, CG3056, displays somatic, male-biased expression at several time points in metamorphosis. Gene expression downstream of the somatic, sex determination genes transformer and doublesex (dsx) was examined in two-day old pupae, which allowed for the identification of genes regulated as a consequence of the sex determination hierarchy. These include the homeotic gene abdominal A, which is more highly expressed in females as compared to males, as a consequence of dsx. For most genes regulated downstream of dsx during pupal development, the mode of regulation is distinct from that observed for the well-studied direct targets of DSX, Yolk protein 1 and 2. Conclusion The data and analyses presented here provide a comprehensive assessment of gene expression during metamorphosis in each sex, in both somatic and germline tissues. Many of the genes that underlie critical developmental processes during metamorphosis, including sex-specific processes, have been identified. These results provide a framework for further functional studies on the regulation of sex-specific development.

Lebo, Matthew S; Sanders, Laura E; Sun, Fengzhu; Arbeitman, Michelle N

2009-01-01

222

Amphibian and reptile biogeographic regions of Northern Eurasia, mapped separately  

Microsoft Academic Search

Distributions of amphibian and reptile faunas were separately delimited on a 1:20 000 000 vegetation map of Northern Eurasia\\u000a divided into 245 10-degree-longitudinal segments of native subzone within the USSR borders as of 1990. All reptile and amphibian\\u000a species recorded in every segment were listed, and the Jaccard indices were calculated, and the similarity matrix was studied\\u000a with cluster analysis.

Yu. S. Ravkin; I. N. Bogomolova; S. V. Chesnokova

2010-01-01

223

Current status of the threatened amphibians and reptiles of Japan  

Microsoft Academic Search

This article compares amphibian and reptile components of the original and revised versions of the Red List of Japan, and\\u000a analyzes geographic patterns of, and major threats to, species and subspecies now assigned to the threatened categories. The\\u000a numbers of both amphibians and reptiles categorized as threatened in the Red List of Japan have increased greatly through\\u000a its revision as

H. Ota

2000-01-01

224

Why amphibians are more sensitive than mammals to xenobiotics.  

PubMed

Dramatic declines in amphibian populations have been described all over the world since the 1980s. The evidence that the sensitivity to environmental threats is greater in amphibians than in mammals has been generally linked to the observation that amphibians are characterized by a rather permeable skin. Nevertheless, a numerical comparison of data of percutaneous (through the skin) passage between amphibians and mammals is lacking. Therefore, in this investigation we have measured the percutaneous passage of two test molecules (mannitol and antipyrine) and three heavily used herbicides (atrazine, paraquat and glyphosate) in the skin of the frog Rana esculenta (amphibians) and of the pig ear (mammals), by using the same experimental protocol and a simple apparatus which minimizes the edge effect, occurring when the tissue is clamped in the usually used experimental device.The percutaneous passage (P) of each substance is much greater in frog than in pig. LogP is linearly related to logKow (logarithm of the octanol-water partition coefficient). The measured P value of atrazine was about 134 times larger than that of glyphosate in frog skin, but only 12 times in pig ear skin. The FoD value (Pfrog/Ppig) was 302 for atrazine, 120 for antipyrine, 66 for mannitol, 29 for paraquat, and 26 for glyphosate.The differences in structure and composition of the skin between amphibians and mammals are discussed. PMID:19888346

Quaranta, Angelo; Bellantuono, Vito; Cassano, Giuseppe; Lippe, Claudio

2009-01-01

225

Why Amphibians Are More Sensitive than Mammals to Xenobiotics  

PubMed Central

Dramatic declines in amphibian populations have been described all over the world since the 1980s. The evidence that the sensitivity to environmental threats is greater in amphibians than in mammals has been generally linked to the observation that amphibians are characterized by a rather permeable skin. Nevertheless, a numerical comparison of data of percutaneous (through the skin) passage between amphibians and mammals is lacking. Therefore, in this investigation we have measured the percutaneous passage of two test molecules (mannitol and antipyrine) and three heavily used herbicides (atrazine, paraquat and glyphosate) in the skin of the frog Rana esculenta (amphibians) and of the pig ear (mammals), by using the same experimental protocol and a simple apparatus which minimizes the edge effect, occurring when the tissue is clamped in the usually used experimental device. The percutaneous passage (P) of each substance is much greater in frog than in pig. LogP is linearly related to logKow (logarithm of the octanol-water partition coefficient). The measured P value of atrazine was about 134 times larger than that of glyphosate in frog skin, but only 12 times in pig ear skin. The FoD value (Pfrog/Ppig) was 302 for atrazine, 120 for antipyrine, 66 for mannitol, 29 for paraquat, and 26 for glyphosate. The differences in structure and composition of the skin between amphibians and mammals are discussed.

Quaranta, Angelo; Bellantuono, Vito; Cassano, Giuseppe; Lippe, Claudio

2009-01-01

226

Global patterns of diversification in the history of modern amphibians  

PubMed Central

The fossil record of modern amphibians (frogs, salamanders, and caecilians) provides no evidence for major extinction or radiation episodes throughout most of the Mesozoic and early Tertiary. However, long-term gradual diversification is difficult to reconcile with the sensitivity of present-day amphibian faunas to rapid ecological changes and the incidence of similar environmental perturbations in the past that have been associated with high turnover rates in other land vertebrates. To provide a comprehensive overview of the history of amphibian diversification, we constructed a phylogenetic timetree based on a multigene data set of 3.75 kb for 171 species. Our analyses reveal several episodes of accelerated amphibian diversification, which do not fit models of gradual lineage accumulation. Global turning points in the phylogenetic and ecological diversification occurred after the end-Permian mass extinction and in the late Cretaceous. Fluctuations in amphibian diversification show strong temporal correlation with turnover rates in amniotes and the rise of angiosperm-dominated forests. Approximately 86% of modern frog species and >81% of salamander species descended from only five ancestral lineages that produced major radiations in the late Cretaceous and early Tertiary. This proportionally late accumulation of extant lineage diversity contrasts with the long evolutionary history of amphibians but is in line with the Tertiary increase in fossil abundance toward the present.

Roelants, Kim; Gower, David J.; Wilkinson, Mark; Loader, Simon P.; Biju, S. D.; Guillaume, Karen; Moriau, Linde; Bossuyt, Franky

2007-01-01

227

Coupling constant metamorphosis and Nth-order symmetries in classical and quantum mechanics  

Microsoft Academic Search

We review the fundamentals of coupling constant metamorphosis (CCM) and the Stäckel transform, and apply them to map integrable and superintegrable systems of all orders into other such systems on different manifolds. In general, CCM does not preserve the order of constants of the motion or even take polynomials in the momenta to polynomials in the momenta. We study specializations

E. G. Kalnins; W. Miller Jr.; S. Post

2010-01-01

228

Juvenile hormone resistance gene Methoprene-tolerant controls entry into metamorphosis in the beetle Tribolium castaneum  

PubMed Central

Besides being a spectacular developmental process, metamorphosis is key to insect success. Entry into metamorphosis is controlled by juvenile hormone (JH). In larvae, JH prevents pupal and adult morphogenesis, thus keeping the insect in its immature state. How JH signals to preclude metamorphosis is poorly understood, and a JH receptor remains unknown. One candidate for the JH receptor role is the Methoprene-tolerant (Met) Per-Arnt-Sim (PAS) domain protein [also called Resistance to JH, Rst (1)JH], whose loss confers tolerance to JH and its mimic methoprene in the fruit fly Drosophila melanogaster. However, Met deficiency does not affect the larval–pupal transition, possibly because this process does not require JH absence in Drosophila. By contrast, the red flour beetle Tribolium castaneum is sensitive to developmental regulation by JH, thus making an ideal system to examine the role of Met in the antimetamorphic JH action. Here we show that impaired function of the Met ortholog TcMet renders Tribolium resistant to the effects of ectopic JH and, in a striking contrast to Drosophila, causes early-stage beetle larvae to undergo precocious metamorphosis. This is evident as TcMet-deficient larvae pupate prematurely or develop specific heterochronic phenotypes such as pupal-like cuticular structures, appendages, and compound eyes. Our results demonstrate that TcMet functions in JH response and provide the critical evidence that the putative JH receptor Met mediates the antimetamorphic effect of JH.

Konopova, Barbora; Jindra, Marek

2007-01-01

229

The history and metamorphosis of the National Registry of Health Care Providers in Clinical Social Work  

Microsoft Academic Search

This paper traces the history and metamorphosis of the National Registry of Health Care Providers in Clinical social Work. It was created in 1975 to credential qualified clinical social workers, and to identify them through a published directory. In 1987 it became the National Institute for Clinical Social Work Advancement. Its objectives and purposes moved from credentialling to advancing the

Ann F. Farwell

1988-01-01

230

The Treatment of Terminal Metamorphosis of Chronic Granulocytic Leukaemia with Corticosteroids and Vincristine  

Microsoft Academic Search

A combination of corticosteroids and vincristine achieved complete remission in 9 out of 15 cases of ‘agranular’ blastic crisis supervening in chronic granulocytic leukaemia, but failed to do so in other 9 cases in which the metamorphosis was of more progressive character and with a ‘granular’ cytomorphology. In the first group, although remissions were generally short, the completeness of their

A. M. Marmont; E. E. Damasio

1973-01-01

231

Effect of epinephrine on the settlement and metamorphosis of Manila clam larvae  

NASA Astrophysics Data System (ADS)

Chemical inducement and DDRT-PCR (differential display reverse transcription PCR) are adopted to investigate the effect of epinephrine (EPI) on the settlement and metamorphosis of Manila clam larvae. Chemical inducement shows that EPI has an effect to some extent on the metamorphosis of Manila clam larvae at all concentrations and in all treatments designed. The most significant result of inducement is obtained at the concentration of 10-6 mol L-1 and for 4h. DDRT-PCR using six primer pairs shows that the gene expression pattern is quite different between EPI treatment and the control. Three hundred and forty-three amplification bands are obtained in total, among which, 67 (19.53%) are differentially appeared. Therefore, EPI has an effect on the gene expression of the eye spot larval Manila clam. It can be hypothesized that EPI is a settlement and metamorphosis inducer for Manila clam. EPI may lead to larvae settlement and metamorphosis by binding to the receptors on the membrane and then changing the gene expression of larvae cells.

Lu, Sumin; Bao, Zhenmin; Liu, Hui; Fang, Jianguang

2006-04-01

232

Engulfing Action of Glial Cells Is Required for Programmed Axon Pruning during Drosophila Metamorphosis  

Microsoft Academic Search

Background: Axon pruning is involved in establishment and maintenance of functional neural circuits. During metamorphosis of Drosophila, selective pruning of larval axons is developmentally regulated by ecdysone and caused by local axon degeneration. Previous studies have revealed intrinsic molecular and cellular mechanisms that trigger this pruning process, but how pruning is accomplished remains essentially unknown.Results: Detailed analysis of morphological changes

Takeshi Awasaki; Kei Ito

2004-01-01

233

Control of Pituitary Thyroid-stimulating Hormone Synthesis and Secretion by Thyroid Hormones during Xenopus Metamorphosis  

EPA Science Inventory

Serum thyroid hormone (TH) concentrations in anuran larvae rise rapidly during metamorphosis. Such a rise in an adult anuran would inevitably trigger a negative feedback response resulting in decreased synthesis and secretion of thyroid-stimulating hormone (TSH) by the pituitary....

234

On nitric oxide signaling, metamorphosis, and the evolution of biphasic life cycles  

Microsoft Academic Search

SUMMARY Complex life cycles are ancient and widely distributed, particularly so in the marine environment. Generally, the marine biphasic life cycle consists of pre- reproductive stages that exist in the plankton for various periods of time before settling and transforming into a benthic reproductive stage. Pre-reproductive stages are frequently phenotypically distinct from the reproductive stage, and thelife cycle transition (metamorphosis)

Cory D. Bishop; Bruce P. Brandhorst

2003-01-01

235

Heat shock induces metamorphosis in the larvae of the prosobranch gastropod Crepidula fornicata  

Microsoft Academic Search

The mechanism through which external cues trigger the metamorphosis of marine invertebrate larvae is incompletely understood. Much of what we currently understand about signal transduction pathways in larval marine invertebrates is based on larval responses to neuroactive compounds, pharmacological agents, and elevated ion concentrations. This paper shows that the larvae of Crepidula fornicata can also be induced to metamorphose through

Michelle F Gaudette; Janet L Lowther; Jan A Pechenik

2001-01-01

236

Metamorphosis in summer flounder: manipulation of thyroid status to synchronize settling behavior, growth, and development  

Microsoft Academic Search

In the aquaculture of summer flounder (Paralichthys dentatus), the inherent variation in growth and settling behavior during metamorphosis may lead to cannibalism and necessitate increased labor due to grading. Our goal was to use thyroid hormone manipulation to synchronize settling behavior and produce a uniformly sized cohort of juvenile summer flounder. Premetamorphic flounder were treated with exogenous thiourea (TU, 30

Steven Gavlik; Melissa Albino; Jennifer L Specker

2002-01-01

237

Effects of fluoride on metamorphosis, thyroid and skeletal development in Bufo gargarizans tadpoles.  

PubMed

This study examined the effects of chronic fluoride exposure on metamorphosis, thyroid and skeletal development in tadpoles of Chinese Toad, Bufo gargarizans. The tadpoles were exposed to fluoride concentrations either at 0, 1, 5, 10, or at 50 mg L(-1) from Gosner stage 26 to Gosner stage 42. Body weight, total length and percentage of tadpoles reaching metamorphosis climax were recorded, and thyroid histological examinations were employed. In addition, mRNA expression of both deiodinase type 2 (D2) and deiodinase type 3 (D3) was analyzed by using RT-PCR and skeletal systems were investigated by using double-staining methodology at stage 42. Results showed that total length and body weight were unaffected by fluoride exposure at all concentrations while metamorphosis was strongly inhibited only by 50 mg L(-1) fluoride. Histomorphological measurements showed the percentage of colloid depletion in thyroid gland increased significantly, while the average diameter of follicles was significantly shorter at 50 mg L(-1) concentration. In addition, fluoride at 5 mg L(-1) can stimulate bone mineralization, while fluoride at 50 mg L(-1) can retard deposition of calcium. In conclusion, our study suggests that 50 mg L(-1) fluoride could damage follicular cells in thyroid gland and induce a sharp reduction in thyroid hormone probably through the up-regulation of D3 mRNA expression, and these influences on thyroid system may delay metamorphosis as well as ossification in bone tissue by inhibiting calcium deposition. PMID:23934448

Zhao, Hongfeng; Chai, Lihong; Wang, Hongyuan

2013-09-01

238

Experimental metamorphosis of Halisarca dujardini larvae (Demospongiae, Halisarcida): evidence of flagellated cell totipotentiality.  

PubMed

The potency of flagellated cells of Halisarca dujardini (Halisarcida, Demospongiae) larvae from the White Sea (Arctic) was investigated experimentally during metamorphosis. Two types of experiments were conducted. First, larvae were maintained in Ca2+ free seawater (CFSW) until the internal cells were released outside through the opening of the posterior pole. These larvae that only composed of flagellated cells (epithelial larvae) were then returned to sea water (SW) to observe their metamorphosis. The posterior aperture closed before they settled on a substratum and started a metamorphosis similar to intact larvae. Secondly, epithelial larvae were, first, further treated in CFSW and then mechanically dissociated. Separated cells or groups of cells were returned to SW, where they constituted large friable conglomerates. After 12-17 h in SW, flagellated cells showed the first steps of dedifferentiation, and regional differentiation was noticeable within conglomerates after approximately 24-36 h. External cells differentiated into pinacocytes while internal cells kept their flagella and became united in a layer. Within 48-72 h, internal cells of the conglomerates formed spherical or ovoid clusters with an internal cavity bearing flagella. These clusters further fused together in a rhagon containing one or two large choanocyte chambers. The sequence of cellular processes in epithelial larvae and in flagellated cell conglomerates was similar. Previous observations indicating the totipotentiality of larval flagellated cells during normal metamorphosis of H. dujardini are thus confirmed. PMID:17427973

Ereskovsky, Alexander V; Konjukov, Paul; Willenz, Philippe

2007-06-01

239

Neotropical Amphibian Declines Affect Stream Ecosystem Properties  

NASA Astrophysics Data System (ADS)

Global declines of amphibians are well documented, yet effects of these dramatic losses on ecosystem structure and function are poorly understood. As part of a larger collaborative project, we compared two upland Panamanian streams. Both streams are biologically and geologically similar; however, one stream (Fortuna) has recently experienced almost complete extirpation of stream-dwelling frogs, while the other (Cope) still has intact populations. We experimentally excluded tadpoles from localized areas in each stream. We then compared chlorophyll a, algal community composition, ash-free dry mass (AFDM), inorganic matter, and insect assemblages in control and exclusion areas. Additionally, we sampled the natural substrate of both streams monthly for chlorophyll a, algal community composition, AFDM, and inorganic matter. At Cope, chlorophyll a, AFDM, and inorganic matter were greater in areas where tadpoles were excluded than in their presence. Numbers of dominant algal species (e.g., Nupela praecipua and Eunotia siolii) were greater in the exclusion versus control treatments. Monthly sampling of natural substrate indicated higher chlorophyll a and AFDM at Cope compared to Fortuna. Our data suggest that stream-dwelling anuran larvae have significant impacts on algal communities. These results also have implications for predicting the relevance of short-term experimental manipulations to long-term, whole-stream processes.

Connelly, S.; Pringle, C. M.; Bixby, R. J.; Whiles, M. R.; Lips, K. R.; Brenes, R.; Colon-Gaud, J. C.; Kilham, S.; Hunte-Brown, M.

2005-05-01

240

Positional information in the amphibian limb.  

PubMed

(1) The concept of positional information is applied to a large amount of data obtained previously in experiments on developing and regenerating amphibian limbs. Only the proximo-distal axis of the limb is considered. It is shown that the concept provides a simple, unitary hypothesis which satisfactorily accounts for the experimental data, and may moreover suggest meaningful new approaches. (2) It is suggested that the boundaries of the bipolar limb system lie in the girdle skeleton and at the distal end of the limb, respectively, and that it is the apical epidermis of the growing or regenerating limb which defines the distal boundary conditions. A relatively stable gradient of positional information is assumed to be set up in the mesoderm (or mesenchyme). It is further shown that the differentiated limb retains its positional information and upon amputation imparts it to the base of the blastema. (3) To explain an apparent discrepancy between the developing and the regenerating limb, it is proposed that dedifferentiation of mesodermal limb tissues upon amputation entails a change os positional value in the mesenchyme. Consequently, the amputation level does not once and for all specify the positional value at the proximal end of a mass of blastemal mesenchyme, particularly when the mesenchyme is transplanted in such a way that its linear size decreases (regression) or increases (furion of several blastemas). PMID:820145

Faber, J

1976-01-01

241

Comparative studies of piscine and amphibian iridoviruses.  

PubMed

A total of 30 iridoviruses collected from Australia, South-East Asia, North America, South America and Europe were characterised. With the exception of the South-East Asian iridoviruses all viruses were found to belong to the genus Ranavirus. All viruses, except those originating from South-East Asia, cross-reacted with antisera against epizootic haematopoietic necrosis virus (EHNV). Viruses or virus-infected cells were examined using electron microscopy, SDS PAGE, restriction endonuclease (RE) digestion, DNA hybridisation, and DNA sequencing. Data from RE digestion of genomic DNA, and from the sequencing of PCR products indicated that the viruses generally grouped according to their geographic and taxonomic (i.e. amphibian or fish) origin. The one exception to this was the viruses from the United Kingdom that grouped with the North American ranaviruses. The differences between specified genomic regions were small. To assess the validity of the differences in sequence homology, similar studies were performed with different isolates from two viruses (EHNV and Guatopo virus (GV), collected from different animals at different locations and time). The sequence data showed complete homology for the isolates for any one virus over the 200 and 586 bp regions examined. Collectively, the data showed that the coding region for the major coat protein (MCP) is stable for any one species (e.g. EHNV). PMID:10752555

Hyatt, A D; Gould, A R; Zupanovic, Z; Cunningham, A A; Hengstberger, S; Whittington, R J; Kattenbelt, J; Coupar, B E

2000-01-01

242

Energy and water in aestivating amphibians.  

PubMed

The physiological mechanisms, behavioral adjustments, and ecological associations that allow animal species to live in extreme environments have evoked the attention of many zoologists. Often, extreme environments are defined as those believed to be limiting to life in terms of water, energetic availability, and temperature. These three elements seem extreme in a number of arid and semi-arid settings that even so have been colonized by amphibians. Because this taxon is usually seen as the quintessential water-dependent ectotherm tetrapods, their presence in a number of semi-arid environments poses a number of intriguing questions regarding microhabitat choice and physiological plasticity, particularly regarding the ecological and physiological correlates of behaviors granting avoidance of the harshest conditions of semi-arid environments. Such avoidance states, generally associated to the concept of aestivation, are currently seen as a diverse and complex phenomena varying from species to species and involving numerous behavioral and metabolic adjustments that enhance survival during the drought. This chapter reviews the physiological ecology of anuran aestivation, mainly from the perspective of water and energy balance. PMID:20069408

Carvalho, José E; Navas, Carlos A; Pereira, Isabel C

2010-01-01

243

Radioecological Studies of Amphibians. Final Report, September 15, 1968--July 21, 1977.  

National Technical Information Service (NTIS)

The radioecological role of amphibians in freshwater environments was studied. Three distinct aspects were studied: (1) the metabolism of radioecologically important radionuclides in amphibians; (2) the effect of acute doses of radiation on adult amphibia...

D. L. Willis

1977-01-01

244

Science Findings, Issue 156, November 2013. Sleuthing Out a Silent Scourge for Amphibians.  

National Technical Information Service (NTIS)

The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), causes the infectious disease chytridiomycosis, which has triggered massive die-offs and extinctions of amphibians around the world. The disease, identified in 1998, is a significant contr...

D. Olson

2013-01-01

245

14 CFR 29.519 - Hull type rotorcraft: Water-based and amphibian.  

Code of Federal Regulations, 2012 CFR

...2014-01-01 false Hull type rotorcraft: Water-based and amphibian. 29.519 Section...CATEGORY ROTORCRAFT Strength Requirements Water Loads § 29.519 Hull type rotorcraft: Water-based and amphibian. (a)...

2014-01-01

246

Distribution, Relative Abundance, and Habitat Associations of Amphibians and Reptiles on Craig Mountain, Idaho.  

National Technical Information Service (NTIS)

The primary goal of this project was to determine the distribution, abundance and habitat associations of the amphibian and reptile species on Craig Mountain (CM), Idaho. This study is important because little was known about the amphibian and reptile spe...

R. L. Llewellyn C. R. Peterson

1998-01-01

247

Demonstration and Certification of Amphibian Ecological Risk Assessment Protocol. Cost and Performance Report (Version 2).  

National Technical Information Service (NTIS)

This ESTCP project, Demonstration and Certification of Amphibian Ecological Risk Assessment Protocol, CU-0514, was designed to demonstrate and validate an innovative technique for the evaluation of potential risks to amphibians in palustrine wetland envir...

C. Archer D. Pillar J. Bleiler M. Bazar M. Johnson

2009-01-01

248

Advective and diffusive dermal processes for estimating terrestrial amphibian pesticide exposure  

EPA Science Inventory

Background/Question/Methods Dermal exposure presents a potentially significant but understudied route for pesticide uptake in terrestrial amphibians. Historically, evaluation of pesticide risk to both amphibians and reptiles has been achieved by comparing ingestion and inhalat...

249

Frog virus 3-like infections in aquatic amphibian communities.  

PubMed

Frog virus 3 (FV3) and FV3-like viruses, are members of the genus Ranavirus (family Iridoviridae), and they have been associated with infectious diseases that may be contributing to amphibian population declines. We examined the mode of transmission of an FV3-like virus, and potential hosts and reservoirs of the virus in a local amphibian community. Using the polymerase chain reaction to detect infected animals, we found an FV3-like virus in south-central Ontario, Canada, amphibian communities, where it infects sympatric amphibian species, including ranid and hylid tadpoles (Rana sylvatica, Hyla versicolor, and Pseudacris spp.), larval salamanders (Ambystoma spp.), and adult eastern-spotted newts (Notophthalmus viridescens). The high prevalence of FV3-like infections in caudate larvae suggests that salamanders are likely to be both hosts and reservoirs. In laboratory FV3 challenges of R. sylvatica, the rate of infection was dependent on the amount of virus to which the animals were exposed. In addition, although vertical transmission was suspected, horizontal transmission through exposure to infected pond water is the most likely route of infection in tadpoles. Based on our observations, a simple model of FV3/FV3-like virus transmission postulates that, in aquatic amphibian communities, transmission of the virus occurs between anuran and urodele species, with ambystomatid salamanders the most likely reservoir for the ranavirus in our study. PMID:18263826

Duffus, A L J; Pauli, B D; Wozney, K; Brunetti, C R; Berrill, M

2008-01-01

250

The cause of global amphibian declines: a developmental endocrinologist's perspective  

PubMed Central

Greater than 70% of the world's amphibian species are in decline. We propose that there is probably not a single cause for global amphibian declines and present a three-tiered hierarchical approach that addresses interactions among and between ultimate and proximate factors that contribute to amphibian declines. There are two immediate (proximate) causes of amphibian declines: death and decreased recruitment (reproductive failure). Although much attention has focused on death, few studies have addressed factors that contribute to declines as a result of failed recruitment. Further, a great deal of attention has focused on the role of pathogens in inducing diseases that cause death, but we suggest that pathogen success is profoundly affected by four other ultimate factors: atmospheric change, environmental pollutants, habitat modification and invasive species. Environmental pollutants arise as likely important factors in amphibian declines because they have realized potential to affect recruitment. Further, many studies have documented immunosuppressive effects of pesticides, suggesting a role for environmental contaminants in increased pathogen virulence and disease rates. Increased attention to recruitment and ultimate factors that interact with pathogens is important in addressing this global crisis.

Hayes, T. B.; Falso, P.; Gallipeau, S.; Stice, M.

2010-01-01

251

Variation in pesticide tolerance of tadpoles among and within species of ranidae and patterns of amphibian decline  

USGS Publications Warehouse

There is significant variation among and within amphibian species with respect to reports of population decline; declining species are often found in environments that are physiograpically similar to environments where the same species is thriving. Because variability exists among organisms in their sensitivity to environmental stressors, it is important to determine the degree of this variation when undertaking conservation efforts. We conducted both lethal (time-to-death) and sublethal (activity change) assays to determine the degree of variation in the sensitivity of tadpoles to a pesticide, carbaryl, at three hierarchical levels: among ranid species, among several populations of a single ranid species (Rana sphenocephala), and within populations of R. sphenocephala. We observed significant variation in time to death among the nine ranid species and among the 10 R. sphenocephala populations we tested. Four out of eight R. sphenocephala populations exhibited significantly different times to death among families. The magnitude of the activity change in response to exposure to sublethal carbaryl levels was significantly different among species and within R. sphenocephala populations. Chemical contamination, at lethal or sublethal levels, can alter natural regulatory processes such as juvenile recruitment in amphibian populations and should be considered a contributing cause of declines in amphibian populations.

Bridges, C. M.; Semlitsch, R. D.

2000-01-01

252

The amphibian chytrid fungus along an altitudinal transect before the first reported declines in Costa Rica  

Microsoft Academic Search

Amphibian populations have declined and disappeared in protected and apparently undisturbed areas around the world, especially in montane areas of the tropics. The amphibian chytrid fungus, Batrachochytrium dendrobatidis has been implicated in many of these declines. In Costa Rica most declines occurred in the highlands. We examined an amphibian collection made in Braulio Carrillo National Park in 1986 for the

Robert Puschendorf; Federico Bolaños; Gerardo Chaves

2006-01-01

253

Patterns of amphibian and reptile diversity at Berara Forest (Sahamalaza Peninsula), NW Madagascar  

Microsoft Academic Search

Amphibians and reptiles were surveyed at Berara, a forest on the Sahamalaza Peninsula, NW Madagascar. Visual methods and pitfalls were used, leading to the discovery of 12 amphibian and 30 reptile species. The herpetofaunal community appeared as a mosaic of dry forest species and species from the more humid Sambirano Domain. The comparatively low amphibian diversity may be correlated with

Franco Andreone; Miguel Vences; Jasmin Emile Randrianirina

2001-01-01

254

50 CFR 16.14 - Importation of live amphibians or their eggs.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Importation of live amphibians or their eggs. 16.14 Section...Wildlife § 16.14 Importation of live amphibians or their eggs. Upon the filing...under § 14.61, all species of live amphibians or their eggs may be imported,...

2010-10-01

255

50 CFR 16.14 - Importation of live amphibians or their eggs.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Importation of live amphibians or their eggs. 16.14 Section...Wildlife § 16.14 Importation of live amphibians or their eggs. Upon the filing...under § 14.61, all species of live amphibians or their eggs may be imported,...

2009-10-01

256

Influence of agricultural landscape structure on a Southern High Plains, USA, amphibian assemblage  

Microsoft Academic Search

Landscape structure can influence demographics of spatially structured populations, particularly less vagile organisms such as amphibians. We examined the influence of agricultural landscape structure on community composition and relative abundance of the 4 most common amphibians in the Southern High Plains of central USA. Amphibian populations were monitored using pitfall traps and drift fence at 16 playa wetlands (8 playas\\/year)

Matthew J. Gray; Loren M. Smith; Raquel I. Leyva

2004-01-01

257

The invasive chytrid fungus of amphibians paralyzes lymphocyte responses  

PubMed Central

The chytrid fungus, Batrachochytrium dendrobatidis, causes chytridiomycosis and is a major contributor to global amphibian declines. Although amphibians have robust immune defenses, clearance of this pathogen is impaired. Because inhibition of host immunity is a common survival strategy of pathogenic fungi, we hypothesized that B. dendrobatidis evades clearance by inhibiting immune functions. We found that B. dendrobatidis cells and supernantants impaired lymphocyte proliferation and induced apoptosis; however, fungal recognition and phagocytosis by macrophages and neutrophils was not impaired. Fungal inhibitory factors were resistant to heat, acid, and protease. Their production was absent in zoospores and reduced by nikkomycin Z, suggesting that they may be components of the cell wall. Evasion of host immunity may explain why this pathogen has devastated amphibian populations worldwide.

Fites, J. Scott; Ramsey, Jeremy P.; Holden, Whitney M.; Collier, Sarah P.; Sutherland, Danica M.; Reinert, Laura K.; Gayek, A. Sophia; Dermody, Terence S.; Aune, Thomas M.; Oswald-Richter, Kyra; Rollins-Smith, Louise A.

2013-01-01

258

Spatial network structure and amphibian persistence in stochastic environments  

PubMed Central

In the past few years, the framework of complex networks has provided new insight into the organization and function of biological systems. However, in spite of its potential, spatial ecology has not yet fully incorporated tools and concepts from network theory. In the present study, we identify a large spatial network of temporary ponds, which are used as breeding sites by several amphibian species. We investigate how the structural properties of the spatial network change as a function of the amphibian dispersal distance and the hydric conditions. Our measures of network topology suggest that the observed spatial structure of ponds is robust to drought (compared with similar random structures), allowing the movement of amphibians to and between flooded ponds, and hence, increasing the probability of reproduction even in dry seasons.

Fortuna, Miguel A; Gomez-Rodriguez, Carola; Bascompte, Jordi

2006-01-01

259

Competency of Reptiles and Amphibians for Eastern Equine Encephalitis Virus  

PubMed Central

Eastern equine encephalitis virus (EEEV) is endemic throughout most of the eastern United States. Although it is transmitted year round in Florida, transmission elsewhere is seasonal. The mechanism that enables EEEV to overwinter in seasonal foci remains obscure. In previous field studies, early season EEEV activity was detected in mosquito species that feed primarily upon ectothermic hosts, suggesting that reptiles and amphibians might represent overwintering reservoir hosts for EEEV. To determine if this might be possible, two commonly fed upon amphibian and reptile species were evaluated as hosts for the North American subtype I strain of EEEV. Neither amphibian species was a competent host. However, circulating viremias were detected in both reptile species examined. Hibernating infected garter snakes remained viremic after exiting hibernation. These data suggest that snakes may represent an overwintering host for North American EEEV.

White, Gregory; Ottendorfer, Christy; Graham, Sean; Unnasch, Thomas R.

2011-01-01

260

Amphibian research and monitoring initiative: concepts and implementation  

USGS Publications Warehouse

This report provides the basis for discussion and subsequent articulation of a national plan for the Amphibian Research and Monitoring Initiative (ARMI). The authors were members of a task force formed from within the U.S. Geological Survey (USGS) that included scientists with expertise in biology, cartography, hydrology, and statistics. The assignment of the task force was to extend work begun by the National Amphibian Leadership Group. This group, composed of senior USGS scientists, managers, and external authorities, met in Gainesville, Florida, in February 20001. The product of this meeting was a document outlining the framework for a national program to monitor amphibian populations and to conduct research into the causes of declines.

Corn, P.S.;Adams, M.J.;Battaglin, W.A.;Gallant, A.L.;James, D.L.;Knutson, M.;Langtimm, C.A.;Sauer, J.R.

2005-01-01

261

The current status of amphibian and reptile ecotoxicological research  

USGS Publications Warehouse

The extent of research conducted on the effects of contaminants on reptiles and amphibians has been scant compared to that of other vertebrate classes including fishes, birds and mammals. In a review of literature from 1972 until 1998 we found that only about 2.7% of the papers published on ecotoxicology in vertebrates concerned amphibians and 1.4% for reptiles. Most studies on amphibian ecotoxicology were on metals, pesticides, and acid deposition. For reptiles the greatest frequency of papers included metals, organochlorines, and others. In proportion to the taxonomic importance, far more papers were written on turtles than on other reptile orders. Most of the papers dealt with residues and very few dealt with effects of contaminant exposure.

Sparling, D.W.; Bishop, C.A.; Linder, G.

2000-01-01

262

Granular gland transcriptomes in stimulated amphibian skin secretions.  

PubMed Central

Amphibian defensive skin secretions are complex, species-specific cocktails of biologically active molecules, including many uncharacterized peptides. The study of such secretions for novel peptide discovery is time-limited, as amphibians are in rapid global decline. While secretion proteome analysis is non-lethal, transcriptome analysis has until now required killing of specimens prior to skin dissection for cDNA library construction. Here we present the discovery that polyadenylated mRNAs encoding dermal granular gland peptides are present in defensive skin secretions, stabilized by endogenous nucleic acid-binding amphipathic peptides. Thus parallel secretory proteome and transcriptome analyses can be performed without killing the specimen in this model amphibian system--a finding that has important implications in conservation of biodiversity within this threatened vertebrate taxon and whose mechanistics may have broader implications in biomolecular science.

Chen, Tianbao; Farragher, Susan; Bjourson, Anthony J; Orr, David F; Rao, Pingfan; Shaw, Chris

2003-01-01

263

Pathogenesis of chytridiomycosis, a cause of catastrophic amphibian declines.  

PubMed

The pathogen Batrachochytrium dendrobatidis (Bd), which causes the skin disease chytridiomycosis, is one of the few highly virulent fungi in vertebrates and has been implicated in worldwide amphibian declines. However, the mechanism by which Bd causes death has not been determined. We show that Bd infection is associated with pathophysiological changes that lead to mortality in green tree frogs (Litoria caerulea). In diseased individuals, electrolyte transport across the epidermis was inhibited by >50%, plasma sodium and potassium concentrations were respectively reduced by approximately 20% and approximately 50%, and asystolic cardiac arrest resulted in death. Because the skin is critical in maintaining amphibian homeostasis, disruption to cutaneous function may be the mechanism by which Bd produces morbidity and mortality across a wide range of phylogenetically distant amphibian taxa. PMID:19900897

Voyles, Jamie; Young, Sam; Berger, Lee; Campbell, Craig; Voyles, Wyatt F; Dinudom, Anuwat; Cook, David; Webb, Rebecca; Alford, Ross A; Skerratt, Lee F; Speare, Rick

2009-10-23

264

The amphibian diversity of bukit jana, taiping, perak.  

PubMed

The study on the amphibian fauna of Bukit Jana, Taiping, Perak was carried out from January 2009 until December 2010 with a total of 12 nights of observation. Twenty four species of frogs from 14 genera and 6 families were recorded to inhabit the Bukit Jana areas. Seven commensal species were found around human habitations near the foothill whereas the others are typical forest frogs found mostly near the rivers, streams and forest floor. This is the first amphibian checklist of Bukit Jana, Perak and it contributed 22% out of 107 species of frogs that are recorded to inhabit Peninsular Malaysia. PMID:24575233

Shahrudin, Shahriza; Jaafar, Ibrahim

2012-12-01

265

The Amphibian Diversity of Bukit Jana, Taiping, Perak  

PubMed Central

The study on the amphibian fauna of Bukit Jana, Taiping, Perak was carried out from January 2009 until December 2010 with a total of 12 nights of observation. Twenty four species of frogs from 14 genera and 6 families were recorded to inhabit the Bukit Jana areas. Seven commensal species were found around human habitations near the foothill whereas the others are typical forest frogs found mostly near the rivers, streams and forest floor. This is the first amphibian checklist of Bukit Jana, Perak and it contributed 22% out of 107 species of frogs that are recorded to inhabit Peninsular Malaysia.

Shahrudin, Shahriza; Jaafar, Ibrahim

2012-01-01

266

Bacteria on the surface of crustose coralline algae induce metamorphosis of the crown-of-thorns starfish Acanthaster planci  

Microsoft Academic Search

The crustose coralline alga Lithothamnium pseudosorum induces high rates of settlement and metamorphosis of larvae of the coral-eating crown-of-thorns starfish (Acanthaster planci). In cases where crustose coralline algae (CCA) induce metamorphosis of marine invertebrate larvae it is normally assumed that the inductive molecules are produced by the alga, but an alternative is that they originate from bacteria on the plant

C. R. Johnson; D. C. Sutton

1994-01-01

267

Dependency on de novo protein synthesis and proteomic changes during metamorphosis of the marine bryozoan Bugula neritina  

PubMed Central

Background Metamorphosis in the bryozoan Bugula neritina (Linne) includes an initial phase of rapid morphological rearrangement followed by a gradual phase of morphogenesis. We hypothesized that the first phase may be independent of de novo synthesis of proteins and, instead, involves post-translational modifications of existing proteins, providing a simple mechanism to quickly initiate metamorphosis. To test our hypothesis, we challenged B. neritina larvae with transcription and translation inhibitors. Furthermore, we employed 2D gel electrophoresis to characterize changes in the phosphoproteome and proteome during early metamorphosis. Differentially expressed proteins were identified by liquid chromatography tandem mass spectrometry and their gene expression patterns were profiled using semi-quantitative real time PCR. Results When larvae were incubated with transcription and translation inhibitors, metamorphosis initiated through the first phase but did not complete. We found a significant down-regulation of 60 protein spots and the percentage of phosphoprotein spots decreased from 15% in the larval stage to12% during early metamorphosis. Two proteins--the mitochondrial processing peptidase beta subunit and severin--were abundantly expressed and phosphorylated in the larval stage, but down-regulated during metamorphosis. MPPbeta and severin were also down-regulated on the gene expression level. Conclusions The initial morphogenetic changes that led to attachment of B. neritina did not depend on de novo protein synthesis, but the subsequent gradual morphogenesis did. This is the first time that the mitochondrial processing peptidase beta subunit or severin have been shown to be down-regulated on both gene and protein expression levels during the metamorphosis of B. neritina. Future studies employing immunohistochemistry to reveal the expression locality of these two proteins during metamorphosis should provide further evidence of the involvement of these two proteins in the morphogenetic rearrangement of B. neritina.

2010-01-01

268

Metamorphosis of bulk waves to Lamb waves in anisotropic piezoelectric crystals  

NASA Astrophysics Data System (ADS)

Acoustic bulk waves were excited by local electric field probe in an anisotropic piezo-electric crystal Lithium Niobate (X-cut). A narrow pulse with a width of 25 ns was used for excitation to obtain wide frequency content in the Fourier domain. A wide spectrum ensures metamorphosis of bulk waves into Lamb waves for scan lengths comparable to the involved wavelengths. The low frequency content experiences multiple reflections from the two surfaces of the plate and disperses along the propagation direction. Acoustic bulk wave's evolution and transformation to Lamb waves are illustrated and explained with the aid of the Lamb wave dispersion phenomenon. The holographic images in the Fourier domain exemplify the metamorphosis of waves during propagation following the excitation at an approximate point source.

Shelke, A.; Habib, A.; Amjad, U.; Pluta, M.; Kundu, T.; Pietsch, U.; Grill, W.

2011-03-01

269

[On some features of embryonic development and metamorphosis of Aurelia aurita (Cindaria, Scyphozoa)].  

PubMed

Aurelia aurita is a cosmopolite species of scyphomedusae. Its major structural patterns and life cycle are well investigated. This work provides a detailed study on development and structure of the planula in A. aurita until it completes its metamorphosis. Lifetime observations and histological study performed during the settlement and metamorphosis of the planulae demonstrated that the inner manibrium linen of primary polyp (gastroderm) develops from the ectoderm of the planula posterior end. The spatial and temporal dynamics of serotonergic cells from the early embryonic stages until the formation of the primary polyp were studied for the first time. In addition, the distribution oftyrosinated tubulin and neuropeptide RFamide at different stages ofA. aurita development were studied. PMID:23101407

Ma?orova, T D; Kosevich, I A; Melekhova, O P

2012-01-01

270

Differentiating Migration and Dispersal Processes for Pond-Breeding Amphibians  

Microsoft Academic Search

Understanding the movement of animals is critical to many aspects of conservation such as spread of emerging disease, proliferation of invasive species, changes in land-use patterns, and responses to global climate change. Movement processes are especially important for amphibian management and conservation as species declines and extinctions worldwide become ever more apparent. To better integrate behavioral and ecological data on

Raymond D. Semlitsch

2008-01-01

271

RISK ASSESSMENT FOR THE EFFECTS OF SOLAR RADIATION ON AMPHIBIANS  

EPA Science Inventory

Recent studies have demonstrated that exposure to solar ultraviolet radiation (UVR) can cause mortality and increase the occurrence of eye and limb malformation in some species of amphibians. Based on these reports and various field observations, it has been hypothesized that UV...

272

Molecular Evidence for the Early History of Living Amphibians  

Microsoft Academic Search

The evolutionary relationships of the three orders of living amphibians (lissamphibians) has been difficult to resolve, partly because of their specialized morphologies. Traditionally, frogs and salamanders are considered to be closest relatives, and all three orders are thought to have arisen in the Paleozoic (>250 myr). Here, we present evidence from the DNA sequences of four mitochondrial genes (2.7 kilobases)

Andrea E. Feller; S. Blair Hedges

1998-01-01

273

UPDATE ON COORDINATED STUDIES OF AMPHIBIAN DISTRIBUTIONS AND UV RADIATION  

EPA Science Inventory

In February of 2000 researchers from the EPA, the National Park Service, other governmental agencies, and academia formulated a plan for coordinated studies of amphibian distributions and aquatic ultraviolet radiation exposure risks in several national parks. At this point we hav...

274

Toxicity of Bog Water to Embryonic and Larval Anuran Amphibians.  

National Technical Information Service (NTIS)

A survey of the amphibians of a north temperate zone bog revealed that a number of species common in suitable locations nearby were absent from the bog. Several species of anuran larvae and embryos suffered high mortality when placed in the naturally acid...

P. A. Saber

1977-01-01

275

The Amphibians and Reptiles of Erie County, Pennsylvania  

Microsoft Academic Search

Forty - five amphibian and reptile species are documented from Erie County. Current status, natural history, dates of observation, and geographic distribution of these species are discussed. Salamander diversity and snake diversity were highest in Millcreek Township, with eleven and ten species, respectively. Frog diversity was highest in Girard and Millcreek Townships and Presque Isle, all with nine species each.

Brian S. Gray; Mark Lethaby

276

Pholiderpeton scutigerum Huxley, an Amphibian from the Yorkshire Coal Measures  

Microsoft Academic Search

Pholiderpeton scutigerum is an eogyrinid amphibian from the Coal Measures of Yorkshire (Westphalian A). The holotype has been prepared by airbrasive and dental-mallet techniques to reveal the most completely preserved of British embolomeres. The skull and braincase morphology of Pholiderpeton is closely similar to that of Eogyrinus but has provided new information about many of the skull roofing bones and

J. A. Clack

1987-01-01

277

LAGOON WATER FROM CONFINED ANIMAL FEED OPERATIONS AND AMPHIBIAN DEVELOPMENT  

EPA Science Inventory

Lagoon Water from Confined Animal Feed Operations and Amphibian Development. Dumont, J. N.* and Slagle, S., Oklahoma State University, Stillwater, OK, and Hutchins, S. R., U.S. Environmental Protection Agency (NRMRL/SPRD), Ada, OK. There is some evidence that confined anima...

278

Stress, reproduction, and adrenocortical modulation in amphibians and reptiles  

Microsoft Academic Search

While the hypothalamo–pituitary–adrenocortical (HPA) response to stress appears to be conserved in vertebrates, the manner in which it is activated and its actions vary. We examine two trends in the stress biology literature that have been addressed in amphibian and reptilian species: (1) variable interactions among stress, corticosterone, and reproduction and (2) adrenocortical modulation. In the first topic we examine

Ignacio T. Moore; Tim S. Jessop

2003-01-01

279

Preliminary checklist of amphibians and reptiles from Baramita, Guyana  

USGS Publications Warehouse

We provide an initial checklist of the herpetofauna of Baramita, a lowland rainforest site in the Northwest Region of Guyana. Twenty-five amphibian and 28 reptile species were collected during two separate dry-season visits. New country records for two species of snakes are documented, contributing to the knowledge on the incompletely known herpetofauna of Guyana.

Reynolds, R. P.; MacCulloch, R. D.

2012-01-01

280

Can Myxosporean parasites compromise fish and amphibian reproduction?  

PubMed Central

Research into fish and amphibian reproduction has increased exponentially in recent years owing to the expansion of the aquaculture industry, the need to recover fishery populations, the impact of endocrine disruptors on the aquatic environment and the global decline of amphibian populations. This review focuses on a group of parasites, the Myxozoa, that affect fish and amphibian reproduction. Lists of the myxosporeans that specifically infect gonads are provided. Most of these are parasitic of freshwater hosts, and most amphibian cases are reported from testes. Sex specificity and sex reversal are discussed in relation to gonadal parasitism. The immune response of the fish to the infection is described, and the contribution of the immunoprivilege of gonads to host invasion is emphasized. The pathological effect of these parasites can be significant, especially in aquacultured broodstocks, on some occasions, leading to parasitic castration. Although myxosporean parasites are currently not very frequent in gonads, their impact could increase in the future owing to the transactions in the global market. Their easy release into the aquatic environment with spawning could make their spreading even more feasible. In the absence of commercial drugs or vaccines to treat and prevent these infections, there is an urgent need to develop specific, rapid and reliable diagnostic tools to control and manage animal movements. In addition, much effort is still to be made on deciphering the life cycle of these organisms, their invasion strategies and their immune evasion mechanisms.

Sitja-Bobadilla, Ariadna

2009-01-01

281

Can myxosporean parasites compromise fish and amphibian reproduction?  

PubMed

Research into fish and amphibian reproduction has increased exponentially in recent years owing to the expansion of the aquaculture industry, the need to recover fishery populations, the impact of endocrine disruptors on the aquatic environment and the global decline of amphibian populations. This review focuses on a group of parasites, the Myxozoa, that affect fish and amphibian reproduction. Lists of the myxosporeans that specifically infect gonads are provided. Most of these are parasitic of freshwater hosts, and most amphibian cases are reported from testes. Sex specificity and sex reversal are discussed in relation to gonadal parasitism. The immune response of the fish to the infection is described, and the contribution of the immunoprivilege of gonads to host invasion is emphasized. The pathological effect of these parasites can be significant, especially in aquacultured broodstocks, on some occasions, leading to parasitic castration. Although myxosporean parasites are currently not very frequent in gonads, their impact could increase in the future owing to the transactions in the global market. Their easy release into the aquatic environment with spawning could make their spreading even more feasible. In the absence of commercial drugs or vaccines to treat and prevent these infections, there is an urgent need to develop specific, rapid and reliable diagnostic tools to control and manage animal movements. In addition, much effort is still to be made on deciphering the life cycle of these organisms, their invasion strategies and their immune evasion mechanisms. PMID:19474043

Sitjà-Bobadilla, Ariadna

2009-08-22

282

Batrachochytrium salamandrivorans sp. nov. causes lethal chytridiomycosis in amphibians.  

PubMed

The current biodiversity crisis encompasses a sixth mass extinction event affecting the entire class of amphibians. The infectious disease chytridiomycosis is considered one of the major drivers of global amphibian population decline and extinction and is thought to be caused by a single species of aquatic fungus, Batrachochytrium dendrobatidis. However, several amphibian population declines remain unexplained, among them a steep decrease in fire salamander populations (Salamandra salamandra) that has brought this species to the edge of local extinction. Here we isolated and characterized a unique chytrid fungus, Batrachochytrium salamandrivorans sp. nov., from this salamander population. This chytrid causes erosive skin disease and rapid mortality in experimentally infected fire salamanders and was present in skin lesions of salamanders found dead during the decline event. Together with the closely related B. dendrobatidis, this taxon forms a well-supported chytridiomycete clade, adapted to vertebrate hosts and highly pathogenic to amphibians. However, the lower thermal growth preference of B. salamandrivorans, compared with B. dendrobatidis, and resistance of midwife toads (Alytes obstetricans) to experimental infection with B. salamandrivorans suggest differential niche occupation of the two chytrid fungi. PMID:24003137

Martel, An; Spitzen-van der Sluijs, Annemarieke; Blooi, Mark; Bert, Wim; Ducatelle, Richard; Fisher, Matthew C; Woeltjes, Antonius; Bosman, Wilbert; Chiers, Koen; Bossuyt, Franky; Pasmans, Frank

2013-09-17

283

The North American Reporting Center for Amphibian Malformations  

NSDL National Science Digital Library

The Northern Prairie Wildlife Research Center (NPWRC) has posted several more resources online. This article introduces readers to The North American Reporting Center for Amphibian Malformations and discusses availability and uses of the Center's databases and resources. The resource may be browsed online or downloaded as a .zip file.

Fowle, Suzanne C.; Johnson, Douglas H.; Jundt, Jeffrey A.

2000-01-01

284

Using Amphibians and Reptiles To Learn the Process of Science.  

ERIC Educational Resources Information Center

Discusses using amphibians and reptiles as an excellent resource for students to observe and gain an understanding of the process of science. These animals are easy to maintain in the classroom and play important roles in ecosystems as the prey for many birds and mammals and as the predators of various organisms. (SAH)

Greene, Janice Schnake; Greene, Brian D.

2001-01-01

285

Plasticity and reprogramming of differentiated cells in amphibian regeneration  

Microsoft Academic Search

Adult urodele amphibians, such as the newt, can regenerate their limbs and various other structures. This is the result of the plasticity and reprogramming of residual differentiated cells, rather than the existence of a 'reserve-cell' mechanism. The recent demonstrations of plasticity in mouse myotubes should facilitate comparative studies of the pathways that underlie the regenerative response, as well as proposing

Anoop Kumar; Jeremy P. Brockes

2002-01-01

286

ESTIMATION OF UV-B EXPOSURE IN AMPHIBIAN AQUATIC ENVIRONMENTS  

EPA Science Inventory

Estimation of ultraviolet radiation B (UV-B; 280 to 320 nm wavelenghts) dose is essential for determining whether UV-B contributes to amphibian population declines and malformations. UV-B dose in wetlands is effected by location, time of day and year, atmospheric levels of ozone,...

287

Effects of pollution on freshwater fish and amphibians  

SciTech Connect

A literature review is presented dealing with studies on the effects of pollution on freshwater fish and amphibians. The pollutants studied included acid mine drainage, PCBs, cadmium, lead, naphthalene, plutonium, in addition to several studies dealing with pH effects. (JMT)

Pickering, Q.H.; Hunt, E.P.; Phipps, G.L.; Roush, T.H.; Smith, W.E.; Spehar, D.L.; Stephan, C.E.; Tanner, D.K.

1983-06-01

288

Using Reptile and Amphibian Activities in the Classroom  

ERIC Educational Resources Information Center

Reptiles and amphibians are a diverse and interesting group of organisms. The four activities described in this article take students' curiosity into the realm of scientific understanding. The activities involve the concepts of species identification; animal adaptations, communication, and habitat; and conservation. (Contains 1 table and 2…

Tomasek, Terry; Matthews, Catherine E.

2008-01-01

289

Utricular otoconia of some amphibians have calcitic morphology  

NASA Technical Reports Server (NTRS)

This report concerns the morphological features of otoconia removed from the inner ear of four amphibian species. Results from scanning electron microscopic examination are compared based on the site of origin. These results show that utricular otoconia have a mineral structure that mimics calcite, rather than the widely accepted idea that they are mineralized by calcium carbonate of the aragonite polymorph.

Pote, K. G.; Ross, M. D.

1993-01-01

290

Environmental determinants of amphibian and reptile species richness in China  

Microsoft Academic Search

Understanding the factors that regulate geographical variation in species richness has been one of the fundamental questions in ecology for decades, but our knowledge of the cause of geographical variation in species richness remains poor. This is particularly true for herpetofaunas (including amphibians and reptiles). Here, using correlation and regression analyses, we examine the relationship of herpetofaunal species richness in

Hong Qian; Xihua Wang; Silong Wang; Yuanliang Li

2007-01-01

291

Amphibian Research and Monitoring Initiative: Concepts and Implementation.  

National Technical Information Service (NTIS)

This report provides the basis for discussion and subsequent articulation of a national plan for the Amphibian Research and Monitoring Initiative (ARMI). The authors were members of a task force formed from within the U.S. Geological Survey (USGS) that in...

P. S. Corn M. J. Adams W. A. Battaglin A. L. Gallant D. L. James

2005-01-01

292

Effects of size at metamorphosis on stonefly fecundity, longevity, and reproductive success  

Microsoft Academic Search

Many organisms with complex life cycles show considerable variation in size and timing at metamorphosis. Adult males of Megarcyssignata (Plecoptera: Perlodidae) are significantly smaller than females and emerge before females (protandry) from two western Colorado\\u000a streams. During summer 1992 stoneflies from a trout stream emerged earlier in the season and at larger sizes than those from\\u000a a colder fishless stream,

Brad W. Taylor; Chester R. Anderson; Barbara L. Peckarsky

1998-01-01

293

Baculovirus infection blocks the progression of fat body degradation during metamorphosis in Bombyx mori  

Microsoft Academic Search

Summary.  ?The effect of baculovirus infection into silkworm pupa particularly on programmed fat body degradation during metamorphosis\\u000a was investigated. Pupal fat body degradation did not occur following infection with Bombyx mori nucleo-polyhedrovirus (BmNPV). There were no histolytic differences between the fat body tissues of mock and BmNPV infected\\u000a papae until 48?h postinfection (p.i.). Between 48 and 72?h p.i., significant differences were

M. Iwanaga; W. K. Kang; M. Kobayashi; S. Maeda

2000-01-01

294

Dendritic Remodeling and Growth of Motoneurons during Metamorphosis of Drosophila melanogaster  

Microsoft Academic Search

Insect motoneurons display dramatic dendritic plasticity during metamorphosis. Many larval motoneurons survive to adulthood but undergo dendritic regression and outgrowth as they are incorporated into developing circuits. This study explores the dendritic remodeling and development of Drosophila motoneu- rons MN1-MN5, which innervate indirect flight muscles of the adult. MN1-MN5 are persistent larval neurons exhibiting two distinct metamorphic histories. MN1-MN4 are

Christos Consoulas; Linda L. Restifo; Richard B. Levine

2002-01-01

295

Larval settlement and metamorphosis of the mussel Mytilus galloprovincialis in response to biofilms  

Microsoft Academic Search

Biofilms were allowed to develop on glass slips immersed 1.0–1.5 m below the sea surface in Tachibana Bay, Nagasaki, Japan,\\u000a for different periods of time from November 2003 to January 2005. The effects of age, immersion month, dry weight, bacterial\\u000a and diatom densities of these biofilms on the settlement and metamorphosis of pediveliger larvae of the mussel Mytilus galloprovincialis were investigated

Wei-Yang Bao; Cyril Glenn Satuito; Jin-Long Yang; Hitoshi Kitamura

2007-01-01

296

The hormonal pathway controlling cell death during metamorphosis in a hemimetabolous insect.  

PubMed

Metamorphosis in holometabolous insects is mainly based on the destruction of larval tissues. Intensive research in Drosophila melanogaster, a model of holometabolan metamorphosis, has shown that the steroid hormone 20-hydroxyecdysone (20E) signals cell death of larval tissues during metamorphosis. However, D. melanogaster shows a highly derived type of development and the mechanisms regulating apoptosis may not be representative in the insect class context. Unfortunately, no functional studies have been carried out to address whether the mechanisms controlling cell death are present in more basal hemimetabolous species. To address this, we have analyzed the apoptosis of the prothoracic gland of the cockroach Blattella germanica, which undergoes stage-specific degeneration just after the imaginal molt. Here, we first show that B. germanica has two inhibitor of apoptosis (IAP) proteins and that one of them, BgIAP1, is continuously required to ensure tissue viability, including that of the prothoracic gland, during nymphal development. Moreover, we demonstrate that the degeneration of the prothoracic gland is controlled by a complex 20E-triggered hierarchy of nuclear receptors converging in the strong activation of the death-inducer Fushi tarazu-factor 1 (BgFTZ-F1) during the nymphal-adult transition. Finally, we have also shown that prothoracic gland degeneration is effectively prevented by the presence of juvenile hormone (JH). Given the relevance of cell death in the metamorphic process, the characterization of the molecular mechanisms regulating apoptosis in hemimetabolous insects would allow to help elucidate how metamorphosis has evolved from less to more derived insect species. PMID:20638378

Mané-Padrós, Daniel; Cruz, Josefa; Vilaplana, Lluisa; Nieva, Claudia; Ureña, Enric; Bellés, Xavier; Martín, David

2010-10-01

297

Changes in the Gut Microbiome of the Sea Lamprey during Metamorphosis  

PubMed Central

Vertebrate metamorphosis is often marked by dramatic morphological and physiological changes of the alimentary tract, along with major shifts in diet following development from larva to adult. Little is known about how these developmental changes impact the gut microbiome of the host organism. The metamorphosis of the sea lamprey (Petromyzon marinus) from a sedentary filter-feeding larva to a free-swimming sanguivorous parasite is characterized by major physiological and morphological changes to all organ systems. The transformation of the alimentary canal includes closure of the larval esophagus and the physical isolation of the pharynx from the remainder of the gut, which results in a nonfeeding period that can last up to 8 months. To determine how the gut microbiome is affected by metamorphosis, the microbial communities of feeding and nonfeeding larval and parasitic sea lamprey were surveyed using both culture-dependent and -independent methods. Our results show that the gut of the filter-feeding larva contains a greater diversity of bacteria than that of the blood-feeding parasite, with the parasite gut being dominated by Aeromonas and, to a lesser extent, Citrobacter and Shewanella. Phylogenetic analysis of the culturable Aeromonas from both the larval and parasitic gut revealed that at least five distinct species were represented. Phenotypic characterization of these isolates revealed that over half were capable of sheep red blood cell hemolysis, but all were capable of trout red blood cell hemolysis. This suggests that the enrichment of Aeromonas that accompanies metamorphosis is likely related to the sanguivorous lifestyle of the parasitic sea lamprey.

Tetlock, Amanda; Yost, Christopher K.; Stavrinides, John

2012-01-01

298

Structural aspects of leg-to-gonopod metamorphosis in male helminthomorph millipedes (Diplopoda)  

PubMed Central

Background In the adult males of helminthomorph millipedes, one or two pairs of legs in the anterior part of the trunk are strongly modified into sexual appendages (gonopods) used for sperm transfer during the copula. Gonopods differentiate in an advanced phase of post-embryonic development, in most cases as replacement for the walking legs of the seventh trunk ring, as these first regress to tiny primordia, to eventually develop into gonopods at a subsequent stadium. These extremely localized but dramatic changes have been described as a non-systemic metamorphosis. In the present study we describe morphological and anatomical changes of trunk ring VII associated with non-systemic metamorphosis in four helminthomorph species. Results As documented here for the first time by means of traditional histology methods and new techniques based on confocal laser scanning microscopy, the external modifications caused by non-systemic metamorphosis are associated to a huge rearrangement of internal anatomy, mostly due to the development of gonopod apodemes and extrinsic muscles. Conclusions Internal changes in the seventh trunk ring, locally leading to the dorsal displacement of the ventral nerve cord and the digestive tract, are modulated in a taxon-specific manner, and are very conspicuous in the blaniulids Nopoiulus kochii and Blaniulus guttulatus, with likely major functional consequences.

2011-01-01

299

Differential expression of proteins and phosphoproteins during larval metamorphosis of the polychaete Capitella sp. I  

PubMed Central

Background The spontaneous metamorphosis of the polychaete Capitella sp. I larvae into juveniles requires minor morphological changes, including segment formation, body elongation, and loss of cilia. In this study, we investigated changes in the expression patterns of both proteins and phosphoproteins during the transition from larvae to juveniles in this species. We used two-dimensional gel electrophoresis (2-DE) followed by multiplex fluorescent staining and MALDI-TOF mass spectrometry analysis to identify the differentially expressed proteins as well as the protein and phosphoprotein profiles of both competent larvae and juveniles. Results Twenty-three differentially expressed proteins were identified in the two developmental stages. Expression patterns of two of those proteins were examined at the protein level by Western blot analysis while seven were further studied at the mRNA level by real-time PCR. Results showed that proteins related to cell division, cell migration, energy storage and oxidative stress were plentifully expressed in the competent larvae; in contrast, proteins involved in oxidative metabolism and transcriptional regulation were abundantly expressed in the juveniles. Conclusion It is likely that these differentially expressed proteins are involved in regulating the larval metamorphosis process and can be used as protein markers for studying molecular mechanisms associated with larval metamorphosis in polychaetes.

2011-01-01

300

Larger Body Size at Metamorphosis Enhances Survival, Growth and Performance of Young Cane Toads (Rhinella marina)  

PubMed Central

Body size at metamorphosis is a key trait in species (such as many anurans) with biphasic life-histories. Experimental studies have shown that metamorph size is highly plastic, depending upon larval density and environmental conditions (e.g. temperature, food supply, water quality, chemical cues from conspecifics, predators and competitors). To test the hypothesis that this developmental plasticity is adaptive, or to determine if inducing plasticity can be used to control an invasive species, we need to know whether or not a metamorphosing anuran’s body size influences its subsequent viability. For logistical reasons, there are few data on this topic under field conditions. We studied cane toads (Rhinella marina) within their invasive Australian range. Metamorph body size is highly plastic in this species, and our laboratory studies showed that larger metamorphs had better locomotor performance (both on land and in the water), and were more adept at catching and consuming prey. In mark-recapture trials in outdoor enclosures, larger body size enhanced metamorph survival and growth rate under some seasonal conditions. Larger metamorphs maintained their size advantage over smaller siblings for at least a month. Our data support the critical but rarely-tested assumption that all else being equal, larger body size at metamorphosis is likely to enhance an individual’s long term viability. Thus, manipulations to reduce body size at metamorphosis in cane toads may help to reduce the ecological impact of this invasive species.

Cabrera-Guzman, Elisa; Crossland, Michael R.; Brown, Gregory P.; Shine, Richard

2013-01-01

301

Scenarios for acceleration in fish development and the role of metamorphosis  

NASA Astrophysics Data System (ADS)

We compare various alternative explanations of why embryo development is sometimes slow relative to juvenile and adult development on the basis of the standard Dynamic Energy Budget (DEB) model and make the comparison with avian altricial versus precocial development. We discuss the role of the energy investment ratio, which combines four different aspects of DEBs: allocation, assimilation, mobilisation and costs for structure. We show how this ratio affects the morphology of growth curves: the ratio of the slopes at start and birth during embryonic growth, as well as the von Bertalanffy time as function of ultimate length during post-embryonic growth. We propose an extension of the standard DEB model that combines a Gompertz (i.e. exponential) start with a von Bertalanffy 'tail' with a smooth transition; a combination that has been applied frequently in fisheries research and here given a mechanistic significance. Implications are that a slow embryonic development is combined with a fast post-metamorphic one and that parameters at metamorphosis depend on feeding history prior to metamorphosis. Identical individuals, in terms of parameter values and amounts of reserve and structure, will become permanently different when they experience different (local) environments, even if they experience identical environments after metamorphosis. This might explain part of the parameter variation amongst individuals.

Kooijman, S. A. L. M.; Pecquerie, L.; Augustine, S.; Jusup, M.

2011-11-01

302

Involvement of Wnt Signaling Pathways in the Metamorphosis of the Bryozoan Bugula neritina  

PubMed Central

In this study, we analyzed the metamorphosis of the marine bryozoan Bugula neritina. We observed the morphogenesis of the ancestrula. We defined three distinct pre-ancestrula stages based on the anatomy of the developing polypide and the overall morphology of pre-ancestrula. We then used an annotation based enrichment analysis tool to analyze the B. neritina transcriptome and identified over-representation of genes related to Wnt signaling pathways, suggesting its involvement in metamorphosis. Finally, we studied the temporal-spatial gene expression studies of several Wnt pathway genes. We found that one of the Wnt ligand, BnWnt10, was expressed spatially opposite to the Wnt antagonist BnsFRP within the blastemas, which is the presumptive polypide. Down-stream components of the canonical Wnt signaling pathway were exclusively expressed in the blastemas. Bn?catenin and BnFz5/8 were exclusively expressed in the blastemas throughout the metamorphosis. Based on the genes expression patterns, we propose that BnWnt10 and BnsFRP may relate to the patterning of the polypide, in which the two genes served as positional signals and contributed to the polarization of the blastemas. Another Wnt ligand, BnWnt6, was expressed in the apical part of the pre-ancestrula epidermis. Overall, our findings suggest that the Wnt signaling pathway may be important to the pattern formation of polypide and the development of epidermis.

Wong, Yue Him; Wang, Hao; Ravasi, Timothy; Qian, Pei-Yuan

2012-01-01

303

Metamorphosis and acquisition of symbiotic algae in planula larvae and primary polyps of Acropora spp.  

NASA Astrophysics Data System (ADS)

Coral planulae settle, then metamorphose and form polyps. This study examined the morphological process of metamorphosis from planulae into primary polyps in the scleractinian corals Acropora nobilis and Acropora microphthalma, using the cnidarian neuropeptide Hym-248 . These two species release eggs that do not contain Symbiodinium. The mode of acquisition of freshly isolated Symbiodinium (zooxanthellae) (FIZ) by the non-symbiotic polyp was also examined. Non-Hym-248 treated swimming Acropora planulae did not develop blastopore, mesenteries or coelenteron until the induction of metamorphosis 16 days after fertilization. The oral pore was formed by invagination of the epidermal layer after formation of the coelenteron in metamorphosing polyps. At 3 days after settlement and metamorphosis, primary polyps exposed to FIZ established symbioses with the Symbiodinium. Two-four days after exposure to FIZ, the distribution of Symbiodinium was limited to the gastrodermis of the pharynx and basal part of the polyps. Eight-ten days after exposure to FIZ, Symbiodinium were present in gastrodermal cells throughout the polyps.

Hirose, M.; Yamamoto, H.; Nonaka, M.

2008-06-01

304

A cathepsin L-like proteinase is involved in moulting and metamorphosis in Helicoverpa armigera.  

PubMed

Holometabolous insects undergo larval moulting and metamorphosis within their life cycle. A cDNA encoding the cathepsin L-like proteinase Ha-cathL has been cloned from Helicoverpa armigera. It has a sequence of 1826 bp and encodes a 550-residue protein with a molecular mass of 63 kDa. Northern blot analysis indicated that Ha-cathL is specifically expressed in haemocytes, with increased expression during larval moulting and metamorphosis. In vivo experimentation revealed that Ha-cathL is up-regulated by 20-hydroxyecdysone. Meanwhile, in situ hybridization and immunocytochemistry revealed that Ha-cathL mRNA is mainly expressed in granulocytes and plasmatocytes. Knock down of cathepsin L by RNA interference results in larvae death before pupation or the formation of a chimeric pupa containing a larval head and thorax, abnormal wings and the pupal abdomen. The reason for this is that the affected haemocytes cannot become granulated, and therefore cannot participate in fat body remodelling and wing development. These facts suggest that Ha-cathL is involved in larval moulting and metamorphosis by participating in the functioning of haemocytes. PMID:20002797

Wang, L-F; Chai, L-Q; He, H-J; Wang, Q; Wang, J-X; Zhao, X-F

2010-02-01

305

Inventory of amphibians and reptiles at Death Valley National Park  

USGS Publications Warehouse

As part of the National Park Service Inventory and Monitoring Program in the Mojave Network, we conducted an inventory of amphibians and reptiles at Death Valley National Park in 2002-04. Objectives for this inventory were to: 1) Inventory and document the occurrence of reptile and amphibian species occurring at DEVA, primarily within priority sampling areas, with the goal of documenting at least 90% of the species present; 2) document (through collection or museum specimen and literature review) one voucher specimen for each species identified; 3) provide a GIS-referenced list of sensitive species that are federally or state listed, rare, or worthy of special consideration that occur within priority sampling locations; 4) describe park-wide distribution of federally- or state-listed, rare, or special concern species; 5) enter all species data into the National Park Service NPSpecies database; and 6) provide all deliverables as outlined in the Mojave Network Biological Inventory Study Plan. Methods included daytime and nighttime visual encounter surveys, road driving, and pitfall trapping. Survey effort was concentrated in predetermined priority sampling areas, as well as in areas with a high potential for detecting undocumented species. We recorded 37 species during our surveys, including two species new to the park. During literature review and museum specimen database searches, we recorded three additional species from DEVA, elevating the documented species list to 40 (four amphibians and 36 reptiles). Based on our surveys, as well as literature and museum specimen review, we estimate an overall inventory completeness of 92% for Death Valley and an inventory completeness of 73% for amphibians and 95% for reptiles. Key Words: Amphibians, reptiles, Death Valley National Park, Inyo County, San Bernardino County, Esmeralda County, Nye County, California, Nevada, Mojave Desert, Great Basin Desert, inventory, NPSpecies.

Persons, Trevor B.; Nowak, Erika M.

2006-01-01

306

Projected climate impacts for the amphibians of the Western hemisphere.  

PubMed

Given their physiological requirements, limited dispersal abilities, and hydrologically sensitive habitats, amphibians are likely to be highly sensitive to future climatic changes. We used three approaches to map areas in the western hemisphere where amphibians are particularly likely to be affected by climate change. First, we used bioclimatic models to project potential climate-driven shifts in the distribution of 413 amphibian species based on 20 climate simulations for 2071-2100. We summarized these projections to produce estimates of species turnover. Second, we mapped the distribution of 1099 species with restricted geographic ranges. Finally, using the 20 future climate-change simulations, we mapped areas that were consistently projected to receive less seasonal precipitation in the coming century and thus were likely to have altered microclimates and local hydrologies. Species turnover was projected to be highest in the Andes Mountains and parts of Central America and Mexico, where, on average, turnover rates exceeded 60% under the lower of two emissions scenarios. Many of the restricted-range species not included in our range-shift analyses were concentrated in parts of the Andes and Central America and in Brazil's Atlantic Forest. Much of Central America, southwestern North America, and parts of South America were consistently projected to experience decreased precipitation by the end of the century. Combining the results of the three analyses highlighted several areas in which amphibians are likely to be significantly affected by climate change for multiple reasons. Portions of southern Central America were simultaneously projected to experience high species turnover, have many additional restricted-range species, and were consistently projected to receive less precipitation. Together, our three analyses form one potential assessment of the geographic vulnerability of amphibians to climate change and as such provide broad-scale guidance for directing conservation efforts. PMID:20121840

Lawler, Joshua J; Shafer, Sarah L; Bancroft, Betsy A; Blaustein, Andrew R

2010-02-01

307

Development of a mobile application for amphibian species recognition  

NASA Astrophysics Data System (ADS)

The smartphones mobility and its pervasiveness are beginning to transform practices in biodiversity conservation. The integrated functionalities of a smartphone have created for the public and biodiversity specialists means to identify, gather and record biodiversity data while simultaneously creating knowledge portability in the digital forms of mobile guides. Smartphones enable beginners to recreate the delight of species identification usually reserved for specialist with years of experience. Currently, the advent of Android platform has enabled stakeholders in biodiversity to harness the ubiquity of this platform and create various types of mobile application or "apps" for use in biodiversity research and conservation. However, there is an apparent lack of application devoted to the identification in herpetofauna or amphibian science. Amphibians are a large class of animals with many different species still unidentified under this category. Here we describe the development of an app called Amphibian Recognition Android Application (ARAA) to identify frog amphibian species as well as an accompanying field guide. The app has the amphibian taxonomic key which assists the users in easy and rapid species identification, thus facilitating the process of identification and recording of species occurrences in conservation work. We will also present an overview of the application work flow and how it is designed to meet the needs a conservationist. As this application is still in its beta phase, further research is required to improve the application to include tools such automatic geolocation and geotagging, participative sensing via crowdsourcing and automated identification via image capture. We believe that the introduction of this app will create an impetus to the awareness of nature via species identification.

Parveen, B.; H, Chew T.; Shamsir, M. S.; Ahmad, N.

2014-02-01

308

Society for the Study of Amphibians and Reptiles  

NSDL National Science Digital Library

Established in 1958, the Society for the Study of Amphibians and Reptiles (SSAR) "is the largest international herpetological society, and is recognized worldwide for having the most diverse program of publications, meetings, and other activities." The SSAR website contains resources for professional and amateur herpetologists alike. The site provides information about SSAR officers and editors, committees, membership, annual meetings, publications, grants, and awards. The site also contains guidelines for submitting to the _Journal of Herpetology_ and the _Herpetological Review_. Notably, members of the SSAR community provide a free (pre-submission) Manuscript Review Service for herpetologists "whose first language is not English, but who are striving to publish their findings in peer reviewed English language journals." Site visitors interested in reptile and amphibian conservation should be sure to check out the SSAE Conservation Committee page.

309

Toxicity of road salt to Nova Scotia amphibians.  

PubMed

The deposition of chemical pollutants into roadside wetlands from runoff is a current environmental concern. In northern latitudes, a major pollutant in runoff water is salt (NaCl), used as de-icing agents. In this study, 26 roadside ponds were surveyed for amphibian species richness and chloride concentration. Acute toxicity tests (LC(50)) were performed on five locally common amphibian species using a range of environmentally significant NaCl concentrations. Field surveys indicated that spotted salamanders (Ambystoma maculatum) and wood frogs (Rana sylvatica) did not occupy high chloride ponds. American toads (Bufo americanus) showed no pond preference based on chloride concentration. Acute toxicity tests showed spotted salamanders and wood frogs were most sensitive to chloride, and American toads were the least. Spring peepers (Pseudacris crucifer) and green frogs (Rana clamitans) showed intermediate sensitivities. We concluded that chloride concentrations in ponds due to application of de-icing salts, influenced community structure by excluding salt intolerant species. PMID:18684543

Collins, Sara J; Russell, Ronald W

2009-01-01

310

Amphibian Development in the Virtual Absence of Gravity  

NASA Technical Reports Server (NTRS)

To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate that a vertebrate can ovulate in the virtual absence of gravity and that the eggs can develop to a free-living stage.

Souza, Kenneth A.; Black, Steven D.; Wassersug, Richard J.

1995-01-01

311

Evaluating the links between climate, disease spread, and amphibian declines.  

PubMed

Human alteration of the environment has arguably propelled the Earth into its sixth mass extinction event and amphibians, the most threatened of all vertebrate taxa, are at the forefront. Many of the worldwide amphibian declines have been caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd), and two contrasting hypotheses have been proposed to explain these declines. Positive correlations between global warming and Bd-related declines sparked the chytrid-thermal-optimum hypothesis, which proposes that global warming increased cloud cover in warm years that drove the convergence of daytime and nighttime temperatures toward the thermal optimum for Bd growth. In contrast, the spatiotemporal-spread hypothesis states that Bd-related declines are caused by the introduction and spread of Bd, independent of climate change. We provide a rigorous test of these hypotheses by evaluating (i) whether cloud cover, temperature convergence, and predicted temperature-dependent Bd growth are significant positive predictors of amphibian extinctions in the genus Atelopus and (ii) whether spatial structure in the timing of these extinctions can be detected without making assumptions about the location, timing, or number of Bd emergences. We show that there is spatial structure to the timing of Atelopus spp. extinctions but that the cause of this structure remains equivocal, emphasizing the need for further molecular characterization of Bd. We also show that the reported positive multi-decade correlation between Atelopus spp. extinctions and mean tropical air temperature in the previous year is indeed robust, but the evidence that it is causal is weak because numerous other variables, including regional banana and beer production, were better predictors of these extinctions. Finally, almost all of our findings were opposite to the predictions of the chytrid-thermal-optimum hypothesis. Although climate change is likely to play an important role in worldwide amphibian declines, more convincing evidence is needed of a causal link. PMID:18987318

Rohr, Jason R; Raffel, Thomas R; Romansic, John M; McCallum, Hamish; Hudson, Peter J

2008-11-11

312

Effect of bismuth subcitrate on amphibian gastroduodenal bicarbonate secretion  

Microsoft Academic Search

The ulcer healing and cytoprotective properties of colloidal bismuth (De-Nol) are well established although its mode of action is unclear. We have examined the action of bismuth subcitrate, the active ingredient of De-Nol, on gastroduodenal bicarbonate secretion by isolated amphibian mucosa. Addition of bismuth subcitrate (10(-6) to 10(-4) M) to the luminal solution produced a dose dependent increase in bicarbonate

C J Shorrock; J R Crampton; L C Gibbons; W D Rees

1989-01-01

313

Landscape-stream interactions and habitat conservation for amphibians.  

PubMed

Semiaquatic organisms depend on the features of both water bodies and landscapes; the interplay between terrestrial and aquatic systems might influence the semiaquatic communities, determining the scale at which management would be more effective. However, the consequences of such interplay are not frequently quantified, particularly at the community level. We analyzed the distribution of amphibians to evaluate whether the influence of landscape features on freshwater ecosystems can have indirect consequences at both the species and community level. We surveyed 74 streams in northern Italy to obtain data on breeding amphibians, water, and microhabitat features; we also measured features of surrounding landscapes. We used an information-theoretic approach and structural equation models to compare hypotheses on causal relationships between species distribution and variables measured at multiple levels. We also used a constrained redundancy analyses to evaluate causal relationships between multivariate descriptors of habitat features and community composition. Distribution of Salamandra salamandra was related to landscape, hydrological, and water characteristics: salamanders were more frequent in permanent streams with low phosphate concentration within natural landscapes. Water characteristics were dependent on landscape: streams in natural landscapes had less phosphates. Landscape influenced the salamander both directly and indirectly through its influence on phosphates. Community structure was determined by both landscape and water characteristics. Several species were associated with natural landscapes, and with particular water characteristics. Landscape explained a significant proportion of variability of water characteristics; therefore it probably had indirect effects on community. Upland environments play key roles for amphibians, for example, as the habitat of adults, but upland environments also have indirect effects on the aquatic life stages, mediated through their influence on water characteristics. Synergistic effects can magnify the negative consequences of landscape alteration on amphibians; landscape management can be particularly effective, as it can also improve wetland features. PMID:21774429

Ficetola, Gentile Francesco; Marziali, Laura; Rossaro, Bruno; De Bernardi, Fiorenza; Padoa-Schioppa, Emilio

2011-06-01

314

Influences of Design and Landscape Placement Parameters on Amphibian Abundance in Constructed Wetlands  

Microsoft Academic Search

As natural wetlands disappear, constructed wetlands may play vital roles in amphibian conservation. However, previous investigations\\u000a have concluded that artificial wetlands do not adequately replace lost wildlife habitat. Nevertheless, constructed wetlands\\u000a serve as breeding habitat for amphibians where extensive natural wetland loss has occurred. To investigate the roles of engineered\\u000a wetland features on amphibian abundance, we surveyed 49 constructed wetlands

Christopher D. Shulse; Raymond D. Semlitsch; Kathleen M. Trauth; Arnold D. Williams

2010-01-01

315

Global stressors and the global decline of amphibians: tipping the stress immunocompetency axis  

Microsoft Academic Search

There is a widespread consensus that the earth is experiencing a mass extinction event and at the forefront are amphibians,\\u000a the most threatened of all vertebrate taxa. A recent assessment found that nearly one-third (32%, 1,856 species) of the world’s\\u000a amphibian species are threatened. Amphibians have existed on the earth for over 300 million years, yet in just the last

Joseph M. Kiesecker

316

Impacts of climate change on the amphibians and reptiles of Southeast Asia  

Microsoft Academic Search

Amphibians and reptiles will be adversely affected by projected rapid changes in climate in the next decades. Here, we review\\u000a the known and potential impacts of climate change on the Southeast Asian amphibians and reptiles and make mitigation recommendations\\u000a for both research and policy. Current amphibian and reptile distributions and ecologies mirror climate patterns, and we expect\\u000a that adaptation to

David Bickford; Sam D. Howard; Daniel J. J. Ng; Jennifer A. Sheridan

2010-01-01

317

Where the Tadpole Meets the World—Observations and Speculations on Biomechanical and Biochemical Factors that Influence Metamorphosis in Anurans 1  

Microsoft Academic Search

SYNOPSIS. A diversity of issues related to metamorphosis are discussed in this paper, ranging from biomechanical constraints on behavior in premeta- morphic anurans, to environmental factors that regulate metamorphosis. I begin by reviewing key behavioral features of tadpoles that have implications to their form and locomotion. Tadpoles lack all visceral behaviors, such as emesis, coughing, and egg-laying, that require major

RICHARD JOEL WASSERSUG

2010-01-01

318

Pentastomiasis and other parasitic zoonoses from reptiles and amphibians.  

PubMed

Reptiles are growing in popularity as pets.The colonization of reptiles and amphibians by parasites and the resulting disease conditions are the most common problems seen in captive animals.This review focuses on pentastomiasis and sparganosis, important parasitic zoonoses of reptiles and amphibians, respectively, and free living-amoebae. Humans are suitable accidental hosts for some pentastomid species (particularly Armillifer and Porocephalus). In geographical areas with special ethnics, such as in West and Central Africa, and East Asia, 8-45% of the human population can be affected. Usually the larvae are coincidentally found during abdominal surgeries. However, fatalities have been described. Extreme caution is necessary when handling infected reptiles. Ocular or cerebral sparganosis is not uncommonly found in humans in East Asia. This disease is caused by spargana, tapeworm larvae (plerocercoids) of Spirometra sp. The infection occurs when uncooked meat from reptiles or amphibians is applied to wounds or eyes and the parasites migrate directly to human tissue, or by consumption of contaminated food or water. As a consequence of the reptile's predatory behaviour, the full spectrum of endo- and ectoparasites from potential prey animals can be found as transiting parasites in the intestinal tract, e. g. Hymenolepis nana, Cryptosporidium (C.) muris, C parvum or Capillaria hepatica. Occasionally, free-living amoebae are also found in reptile faeces (Acanthamoeba, Naegleria, Hartmanella, Vahlkampfia or Echinamoeba sp.). PMID:22191176

Pantchev, Nikola; Tappe, Dennis

2011-01-01

319

Minimising exposure of amphibians to pathogens during field studies.  

PubMed

Many of the recent global amphibian mass mortalities, declines and extinctions have been attributed to the emerging infectious disease chytridiomycosis. There have been mass mortalities due to ranaviral disease but no major declines or extinctions. Controlling the transmission and spread of disease is of utmost importance, especially where there is the potential for human involvement. We have reviewed current hygiene guidelines for working with wild frogs, identified potential flaws and recommended those most suitable and effective for the field environment. Our within-site hygiene measures aim to reduce the risk of transmission among individuals. These measures encompass the capture, handling and holding of amphibians, skin disinfection before and after invasive procedures, marking frogs, sealing open wounds and treatment of accessory equipment. Our between-site hygiene measures aim to mitigate the risk of pathogen spread among populations. We have designed a risk calculator to help simplify and standardise the decision-making process for determining the level of risk and appropriate risk mitigation strategies to reduce the risk of increasing pathogen spread above background levels. Calculation of an overall risk score for pathogen spread takes into account the prior activity of field workers, the proposed activity, remoteness of the site, presence of known pathogens and the consequences of increased pathogen spread for amphibians in a given area. PMID:21268979

Phillott, A D; Speare, R; Hines, H B; Skerratt, L F; Meyer, E; McDonald, K R; Cashins, S D; Mendez, D; Berger, L

2010-11-01

320

Molecular characterization of iridoviruses isolated from sympatric amphibians and fish  

USGS Publications Warehouse

Iridoviruses infect invertebrates (primarily insects and crustaceans) and ectothermic vertebrates (fish, amphibians, and reptiles). Identical, or nearly identical viruses, have been isolated from different animals within the same taxonomic class, indicating that infection by a given virus is not limited to a single species. Although inter-class infections have been documented following experimental infection with vertebrate iridoviruses, it is not clear whether such infections occur in nature. Here we report the isolation of apparently identical iridoviruses from wild sympatric fish (the threespine stickleback, Gasterostelus aculeatus) and amphibians (the red-legged frog, Rana aurora). Viruses isolated from sticklebacks (stickleback virus, SBV) and from a red-legged frog tadpole (tadpole virus 2, TV2) replicated in fathead minnow (FHM) cells and synthesized proteins which co-migrated with those of frog virus 3 (FV3). Following restriction endonuclease digestion of viral DNA with Hind III and Xba I, gel analysis showed that the profiles of SBV and TV2 were identical to each other and distinct from FV3. Using oligonucleotide primers specific for a highly conserved region of the iridovirus major capsid protein, an not, vert, ~500 nucleotide DNA fragment was amplified from SBV and TV2. Sequence analysis showed that within this 500 nucleotide region SBV and TV2 were identical to each other and to FV3. Taken together these results provide the first evidence that iridoviruses naturally infect animals belonging to different taxonomic classes, and strengthen the suggestion that fish may serve as a reservoir for amphibian viruses or vice versa.

Mao, J.; Green, D. E.; Fellers, G.; Chinchar, V. G.

1999-01-01

321

Optimizing protection efforts for amphibian conservation in Mediterranean landscapes  

NASA Astrophysics Data System (ADS)

Amphibians epitomize the modern biodiversity crisis, and attract great attention from the scientific community since a complex puzzle of factors has influence on their disappearance. However, these factors are multiple and spatially variable, and declining in each locality is due to a particular combination of causes. This study shows a suitable statistical procedure to determine threats to amphibian species in medium size administrative areas. For our study case, ten biological and ecological variables feasible to affect the survival of 15 amphibian species were categorized and reduced through Principal Component Analysis. The principal components extracted were related to ecological plasticity, reproductive potential, and specificity of breeding habitats. Finally, the factor scores of species were joined in a presence-absence matrix that gives us information to identify where and why conservation management are requires. In summary, this methodology provides the necessary information to maximize benefits of conservation measures in small areas by identifying which ecological factors need management efforts and where should we focus them on.

García-Muñoz, Enrique; Ceacero, Francisco; Carretero, Miguel A.; Pedrajas-Pulido, Luis; Parra, Gema; Guerrero, Francisco

2013-05-01

322

High prevalence of the amphibian chytrid pathogen in Gabon.  

PubMed

Amphibian chytridiomycosis is an infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd) that is implicated in the worldwide decline and extinction of amphibians. Africa has been proposed as a potential source for the global expansion of Bd, yet the distribution of Bd across the continent remains largely unexplored. Using quantitative polymerase chain reaction (qPCR), we screened for the presence of Bd in 166 adult anurans from two national parks in Gabon (Monts de Cristal and Ivindo). Bd was detected in 20 of the 42 species and was present at all three sites surveyed (two in Monts de Cristal, and one in Ivindo) with high prevalence (19.6%-36.0%). Both national parks were Bd-positive at all elevations and across habitat types, though no dead or dying frogs were encountered. To our knowledge, this study presents the first evidence of Bd in Gabon and the first record of infection for 19 of the 20 species that were Bd-positive. Documenting the distribution and virulence of Bd across Africa will be essential for understanding the dynamics of amphibian chytridiomycosis across the globe. PMID:21210295

Bell, Rayna C; Gata Garcia, Adriana V; Stuart, Bryan L; Zamudio, Kelly R

2011-03-01

323

Applying amphibian limb regeneration to human wound healing: a review.  

PubMed

In contrast to the limited regenerative ability found in human wound healing, which often results in unsatisfying and deficient scar formation, urodele amphibians, with the Mexican axolotl as a prime example, expose an extraordinary regenerative capacity. This regeneration leads to a perfect restoration of tissue architecture, function, and aesthetics with the axolotl being actually able to reclaim complete limbs. Evolutionary considerations suggest that regeneration might be a biologic principle which also underlies human wound healing. Experimental findings, such as comparative studies on transforming growth factor-? and fibroblast growth factor accentuate this assumption. Regeneration, as recent data indicate, might be a question of adaptive immunity. The loss of regenerative potency correlates with the decrease of regeneration in most species, whereas the Mexican axolotl lacks adaptive immunity throughout its life. The characterization of molecular pathways as a prerequisite for any control of regenerative processes sets an increasing indication toward the transfer into human beings. Some regenerative techniques, eg, recombinant transforming growth factor-? have already emerged. Molecular findings suggest that there is an intrinsic regenerative capacity in humans which might be initiated under appropriate circumstances. The Mexican axolotl is liable to diverse surgical and molecular approaches. Though well-known among developmental biologists, its exploitation for experimental Plastic Surgery still has to be established. We therefore intend to give an introduction to amphibian regeneration and the common evolutionary roots of regeneration and human wound healing, as we believe that Plastic Surgery takes a unique advantage of performing basic research on amphibian regeneration. PMID:20948421

Menger, Bjoern; Vogt, Peter M; Kuhbier, Joern W; Reimers, Kerstin

2010-11-01

324

Invasive hybrid tiger salamander genotypes impact native amphibians.  

PubMed

Although the ecological consequences of species invasions are well studied, the ecological impacts of genetic introgression through hybridization are less understood. This is particularly true of the impacts of hybridization on "third party" community members not genetically involved in hybridization. We also know little about how direct interactions between hybrid and parental individuals influence fitness. Here, we examined the ecological effects of hybridization between the native, threatened California Tiger Salamander (Ambystoma californiense) and the introduced Barred Tiger Salamander (Ambystoma tigrinum mavortium). Native x introduced hybrids are widespread in California, where they are top predators in seasonal ponds. We examined the impacts of early generation hybrids (first 2 generations of parental crosses) and contemporary hybrids derived from ponds where hybrids have been under selection in the wild for 20 generations. We found that most classes of hybrid tiger salamander larvae dramatically reduced survival of 2 native community members, the Pacific Chorus Frog (Pseudacris regilla) and the California Newt (Taricha torosa). We also found that native A. californiense larvae were negatively impacted by the presence of hybrid larvae: Native survival and size at metamorphosis were reduced and time to metamorphosis was extended. We also observed a large influence of Mendelian dominance on size, metamorphic timing and predation rate of hybrid tiger salamanders. These results suggest that both genetic and ecological factors are likely to influence the dynamics of admixture, and that tiger salamander hybridization might constitute a threat to additional pond-breeding species of concern in the region. PMID:19564601

Ryan, Maureen E; Johnson, Jarrett R; Fitzpatrick, Benjamin M

2009-07-01

325

Amphibian and reptile declines over 35 years at La Selva, Costa Rica.  

PubMed

Amphibians stand at the forefront of a global biodiversity crisis. More than one-third of amphibian species are globally threatened, and over 120 species have likely suffered global extinction since 1980. Most alarmingly, many rapid declines and extinctions are occurring in pristine sites lacking obvious adverse effects of human activities. The causes of these "enigmatic" declines remain highly contested. Still, lack of long-term data on amphibian populations severely limits our understanding of the distribution of amphibian declines, and therefore the ultimate causes of these declines. Here, we identify a systematic community-wide decline in populations of terrestrial amphibians at La Selva Biological Station, a protected old-growth lowland rainforest in lower Central America. We use data collected over 35 years to show that population density of all species of terrestrial amphibians has declined by approximately 75% since 1970, and we show identical trends for all species of common reptiles. The trends we identify are neither consistent with recent emergence of chytridiomycosis nor the climate-linked epidemic hypothesis, two leading putative causes of enigmatic amphibian declines. Instead, our data suggest that declines are due to climate-driven reductions in the quantity of standing leaf litter, a critical microhabitat for amphibians and reptiles in this assemblage. Our results raise further concerns about the global persistence of amphibian populations by identifying widespread declines in species and habitats that are not currently recognized as susceptible to such risks. PMID:17449638

Whitfield, Steven M; Bell, Kristen E; Philippi, Thomas; Sasa, Mahmood; Bolaños, Federico; Chaves, Gerardo; Savage, Jay M; Donnelly, Maureen A

2007-05-15

326

Synergism between UV-B radiation and pathogen magnifies amphibian embryo mortality in nature  

SciTech Connect

Previous research has shown that amphibians have differential sensitivity to ultraviolet-B (UV-B) radiation. In some species, ambient levels of UV-B radiation cause embryonic mortality in nature. The detrimental effects of UV-B alone or with other agents may ultimately affect amphibians at the population level. Here, we experimentally demonstrate a synergistic effect between UV-B radiation and a pathogenic fungus in the field that increases the mortality of amphibian embryos compared with either factor alone. Studies investigating single factors for causes of amphibian egg mortality or population declines may not reveal the complex factors involved in declines.

Kiesecker, J.M.; Blaustein, R. [Oregon State Univ., Corvallis, OR (United States)

1995-11-21

327

Common and Distinct Roles of Juvenile Hormone Signaling Genes in Metamorphosis of Holometabolous and Hemimetabolous Insects  

PubMed Central

Insect larvae metamorphose to winged and reproductive adults either directly (hemimetaboly) or through an intermediary pupal stage (holometaboly). In either case juvenile hormone (JH) prevents metamorphosis until a larva has attained an appropriate phase of development. In holometabolous insects, JH acts through its putative receptor Methoprene-tolerant (Met) to regulate Krüppel-homolog 1 (Kr-h1) and Broad-Complex (BR-C) genes. While Met and Kr-h1 prevent precocious metamorphosis in pre-final larval instars, BR-C specifies the pupal stage. How JH signaling operates in hemimetabolous insects is poorly understood. Here, we compare the function of Met, Kr-h1 and BR-C genes in the two types of insects. Using systemic RNAi in the hemimetabolous true bug, Pyrrhocoris apterus, we show that Met conveys the JH signal to prevent premature metamorphosis by maintaining high expression of Kr-h1. Knockdown of either Met or Kr-h1 (but not of BR-C) in penultimate-instar Pyrrhocoris larvae causes precocious development of adult color pattern, wings and genitalia. A natural fall of Kr-h1 expression in the last larval instar normally permits adult development, and treatment with an exogenous JH mimic methoprene at this time requires both Met and Kr-h1 to block the adult program and induce an extra larval instar. Met and Kr-h1 therefore serve as JH-dependent repressors of deleterious precocious metamorphic changes in both hemimetabolous and holometabolous juveniles, whereas BR-C has been recruited for a new role in specifying the holometabolous pupa. These results show that despite considerable evolutionary distance, insects with diverse developmental strategies employ a common-core JH signaling pathway to commit to adult morphogenesis.

Jindra, Marek

2011-01-01

328

Turbine Sound May Influence the Metamorphosis Behaviour of Estuarine Crab Megalopae  

PubMed Central

It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM) for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21–31% compared to silent control treatments, 38–47% compared to tidal turbine sound treatments, and 46–60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment.

Pine, Matthew K.; Jeffs, Andrew G.; Radford, Craig A.

2012-01-01

329

Post-Embryonic Transcriptomes of the Prawn Macrobrachium rosenbergii: Multigenic Succession through Metamorphosis  

PubMed Central

Like many metazoans, the freshwater prawn Macrobrachium rosenbergii begins its post-embryonic life with a set of morphologically distinct planktonic larval stages, followed by a benthic post-larval stage during which the maturing organism differs from the larvae both ecologically and physiologically. Understanding of the molecular basis underlying morphogenesis in crustaceans is limited to the observation that methyl farnesoate, the non-epoxidated form of the insect juvenile hormone, acts as the active crustacean juvenoid. Molt steroids were also linked to morphogenesis and several other molecular pathways, such as Hedgehog and Wnt, are known to underlie morphogenesis in all metazoans examined and, as such, are thought to do the same in crustaceans. Using next generation sequencing, we deep-sequenced the transcriptomes of several larval and post-larval stages. De novo assembly, followed by bioinformatics analysis, revealed that many novel transcripts are over-expressed in either larvae- or post-larvae-stage prawn, shedding light on the molecular basis underlying M. rosenbergii metamorphosis. Fast larval molting rates and periodic morphological changes were reflected in over-expression of transcripts annotated to the cell cycle, DNA replication and morphogenic pathways (i.e., Hedgehog and Wnt). Further characterization of transcripts assigned to morphogenic pathways by real-time RT-PCR reconfirmed their over-expression in larvae, albeit with a more complex expression pattern when examined in the individual developmental stages. The expression level of an orthologue of cytochrome P450, 15A1, known to epoxidize methyl farnesoate in insects, was increased in the late larval and early post-larval stages, in accordance with the role of methyl farnesoate in crustacean metamorphosis. This study exemplifies the applicability of a high-throughput sequencing approach for studying complex traits, including metamorphosis, providing new insight into this unexplored area of crustacean research.

Ventura, Tomer; Manor, Rivka; Aflalo, Eliahu D.; Chalifa-Caspi, Vered; Weil, Simy; Sharabi, Omri; Sagi, Amir

2013-01-01

330

Turbine sound may influence the metamorphosis behaviour of estuarine crab megalopae.  

PubMed

It is now widely accepted that a shift towards renewable energy production is needed in order to avoid further anthropogenically induced climate change. The ocean provides a largely untapped source of renewable energy. As a result, harvesting electrical power from the wind and tides has sparked immense government and commercial interest but with relatively little detailed understanding of the potential environmental impacts. This study investigated how the sound emitted from an underwater tidal turbine and an offshore wind turbine would influence the settlement and metamorphosis of the pelagic larvae of estuarine brachyuran crabs which are ubiquitous in most coastal habitats. In a laboratory experiment the median time to metamorphosis (TTM) for the megalopae of the crabs Austrohelice crassa and Hemigrapsus crenulatus was significantly increased by at least 18 h when exposed to either tidal turbine or sea-based wind turbine sound, compared to silent control treatments. Contrastingly, when either species were subjected to natural habitat sound, observed median TTM decreased by approximately 21-31% compared to silent control treatments, 38-47% compared to tidal turbine sound treatments, and 46-60% compared to wind turbine sound treatments. A lack of difference in median TTM in A. crassa between two different source levels of tidal turbine sound suggests the frequency composition of turbine sound is more relevant in explaining such responses rather than sound intensity. These results show that estuarine mudflat sound mediates natural metamorphosis behaviour in two common species of estuarine crabs, and that exposure to continuous turbine sound interferes with this natural process. These results raise concerns about the potential ecological impacts of sound generated by renewable energy generation systems placed in the nearshore environment. PMID:23240063

Pine, Matthew K; Jeffs, Andrew G; Radford, Craig A

2012-01-01

331

AMPHIBIAN OCCURRENCE AND AQUATIC INVADERS IN A CHANGING LANDSCAPE: IMPLICATIONS FOR WETLAND MITIGATION IN THE WILLAMETTE VALLEY, OREGON, USA  

EPA Science Inventory

Despite concern about the conservation status of amphibians in western North America, few field studies have documented occurrence patterns of amphibians relative to potential stressors. We surveyed wetland fauna in Oregon Willamette Valley and used an information theoretic appro...

332

Larval rearing, metamorphosis, growth and reproduction of the eolid nudibranch hermissenda crassicornis (eschscholtz, 1831) (gastropoda: opisthobranchia).  

PubMed

1. Hermissenda crassicornis is a subannual nudibranch species that reproduces year-round. 2. There is a significant positive relationship between adult weight, diameter of the egg mass, estimated number of eggs per egg mass, and average number of eggs per capsule. 3. There is a planktonic veliger stage of 34 days minimum at 13 degrees -15 degrees C. 4. Larvae metamorphose on at least three species of hydroids. 5. To develop in reasonable numbers to a state competent to metamorphose veligers require a diet that includes phytoplankton of larger cell size (10-11 microm) than the commonly used Isochrysis and Monochrysis (5 microm). 6. Although Hermissenda feeds on a wide variety of sessile invertebrate species in the ocean, a diet of tunicate alone (Ciona intestinalis) promotes good growth and survival in the laboratory. 7. Egg mass deposition is initiated only after first copulation, except in the last month of life, and continues from about one-month post-metamorphosis to death, at about four months post-metamorphosis. Generation time (egg-to-egg) may be as short as 2.5 months. 8. A laboratory strain of Hermissenda is being established to provide animals of known history for research on the neural correlates of behavior. Animals, at least initially, are being selected for fast growth rate. PMID:20693369

Harrigan, J F; Alkon, D L

1978-06-01

333

A New Clarification Method to Visualize Biliary Degeneration During Liver Metamorphosis in Sea Lamprey (Petromyzon marinus).  

PubMed

Biliary atresia is a rare disease of infancy, with an estimated 1 in 15,000 frequency in the southeast United States, but more common in East Asian countries, with a reported frequency of 1 in 5,000 in Taiwan. Although much is known about the management of biliary atresia, its pathogenesis is still elusive. The sea lamprey (Petromyzon marinus) provides a unique opportunity to examine the mechanism and progression of biliary degeneration. Sea lamprey develop through three distinct life stages: larval, parasitic, and adult. During the transition from larvae to parasitic juvenile, sea lamprey undergo metamorphosis with dramatic reorganization and remodeling in external morphology and internal organs. In the liver, the entire biliary system is lost, including the gall bladder and the biliary tree. A newly-developed method called "CLARITY" was modified to clarify the entire liver and the junction with the intestine in metamorphic sea lamprey. The process of biliary degeneration was visualized and discerned during sea lamprey metamorphosis by using laser scanning confocal microscopy. This method provides a powerful tool to study biliary atresia in a unique animal model. PMID:24962075

Chung-Davidson, Yu-Wen; Davidson, Peter J; Scott, Anne M; Walaszczyk, Erin J; Brant, Cory O; Buchinger, Tyler; Johnson, Nicholas S; Li, Weiming

2014-01-01

334

Rho-LIM kinase signaling regulates ecdysone-induced gene expression and morphogenesis during Drosophila metamorphosis.  

PubMed

The steroid hormone 20-hydroxyecdysone (ecdysone) is the key regulator of postembryonic developmental transitions in insects and controls metamorphosis by triggering the morphogenesis of adult tissues from larvae. The Rho GTPase, which mediates cell shape change and migration, is also an essential regulator of tissue morphogenesis during development. Rho activity can modulate gene expression, in part, by activating LIM kinase (LIMK) and consequently affecting actin-induced SRF transcriptional activity. We have established a link between Rho-LIMK-SRF signaling and the ecdysone-induced transcriptional response during Drosophila development. Specifically, we determined that the Rho GTPase, via LIMK, regulates the expression of several ecdysone-responsive genes, including those encoding the ecdysone receptor itself, a downstream transcription factor (Br-C), and Stubble, a transmembrane protease required for proper leg formation. Stubble and Br-C mutants exhibit strong genetic interactions with several Rho pathway components in the formation of adult structures, but not with Rac or Cdc42. In cultured SL2 cells, inhibition of Rho, F-actin assembly, or SRF blocks the transcriptional response to ecdysone. Together, these findings indicate a link between Rho-LIMK signaling and steroid hormone-induced gene expression in the context of metamorphosis and thereby establish a novel role for the Rho GTPase in development. PMID:14972681

Chen, Guang-Chao; Gajowniczek, Patrycja; Settleman, Jeffrey

2004-02-17

335

Proteomic response of marine invertebrate larvae to ocean acidification and hypoxia during metamorphosis and calcification.  

PubMed

Calcifying marine invertebrates with complex life cycles are particularly at risk to climate changes as they undergo an abrupt ontogenetic shift during larval metamorphosis. Although our understanding of the larval response to climate changes is rapidly advancing, the proteome plasticity involved in a compensatory response to climate change is still unknown. In this study, we investigated the proteomic response of metamorphosing larvae of the tubeworm Hydroides elegans, challenged with two climate change stressors, ocean acidification (OA; pH 7.6) and hypoxia (HYP; 2.8 mg O2 l(-1)), and with both combined. Using a two-dimensional gel electrophoresis (2-DE)-based approach coupled with mass spectrometry, we found that climate change stressors did not affect metamorphosis except under OA, but altered the larval proteome and phosphorylation status. Metabolism and various stress and calcification-related proteins were downregulated in response to OA. In OA and HYP combined, HYP restored the expression of the calcification-related proteins to the control levels. We speculate that mild HYP stress could compensate for the negative effects of OA. This study also discusses the potential functions of selected proteins that might play important roles in larval acclimation and adaption to climate change. PMID:24307710

Mukherjee, Joy; Wong, Kelvin K W; Chandramouli, Kondethimmanahalli H; Qian, Pei-Yuan; Leung, Priscilla T Y; Wu, Rudolf S S; Thiyagarajan, Vengatesen

2013-12-15

336

Molecular metamorphosis in polcalcin allergens by EF-hand rearrangements and domain swapping.  

PubMed

Polcalcins such as Bet v 4 and Phl p 7 are pollen allergens that are constructed from EF-hand motifs, which are very common and well characterized helix-loop-helix motifs with calcium-binding functions, as elementary building blocks. Being members of an exceptionally well-characterized protein superfamily, these allergens highlight the fundamental challenge in explaining what features distinguish allergens from nonallergenic proteins. We found that Bet v 4 and Phl p 7 undergo oligomerization transitions with characteristics that are markedly different from those typically found in proteins: transitions from monomers to dimers and to distinct higher oligomers can be induced by increasing temperature; similarly, low concentrations of destabilizing agents, e.g. SDS, induce oligomerization transitions of Bet v 4. The changes in the quaternary structure, termed molecular metamorphosis, are induced and controlled by a combination of EF-hand rearrangements and domain swapping rather than by the classical law of mass action. Using an EF-hand-pairing model, we provide a two-step model that consistently explains and substantiates the observed metamorphosis. Moreover, the unusual oligomerization behavior suggests a straightforward explanation of how allergens can accomplish the crosslinking of IgE on mast cells, a hallmark of allergens. PMID:20553495

Magler, Iris; Nüss, Dorota; Hauser, Michael; Ferreira, Fatima; Brandstetter, Hans

2010-06-01

337

The Effect of Trematode Infection on Amphibian Limb Development and Survivorship  

Microsoft Academic Search

The causes of amphibian deformities and their role in widespread amphibian declines remain conjectural. Severe limb abnormalities were induced at high frequencies in Pacific treefrogs (Hyla regilla) exposed to cercariae of a trem- atode parasite (Ribeiroia sp.). The abnormalities closely matched those ob- served at field sites, and an increase in parasite density caused an increase in abnormality frequency and

Pieter T. J. Johnson; Kevin B. Lunde; Euan G. Ritchie; Alan E. Launer

1999-01-01

338

Coordinated Studies of Ultraviolet Radiation and Amphibians in Lentic Wetland Habitats  

EPA Science Inventory

Ultraviolet radiation (UVR) has been suggested as a potential cause of population declines and increases in malformations in amphibians. This study indicates that the present distributions of amphibians in four western U.S. National Parks are not related to UVR exposure, and sugg...

339

Effects of Silvicultural Edges on the Distribution and Abundance of Amphibians in Maine  

Microsoft Academic Search

Amphibians share several biological characteristics that may cause them to be sensitive to abrupt transitions in microhabitat and microclimate that occur across forest edges. To better understand the impor- tance of edge effects on amphibians in a forested landscape, we sampled the distribution of populations along drift fences placed perpendicular to silvicultural edges of varying contrast in central Maine. Within

Phillip G. Demaynadier; Malcolm L. Hunter

1998-01-01

340

Complexity in conservation: lessons from the global decline of amphibian populations  

Microsoft Academic Search

As part of an overall ''biodiversity crisis'' many amphibian populations are in decline throughout the world. Numerous causes have been invoked to explain these declines. These include habitat destruction, climate change, increasing levels of ultraviolet radiation, environmental contamination, disease, and the introduction of non-native species. In this paper, we argue that amphibian population declines are caused by different abiotic and

Andrew R. Blaustein; Joseph M. Kiesecker

2002-01-01

341

Impacts from PCB Accumulation on Amphibians Inhabiting Streams Flowing from the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

Contamination at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky, has been under evaluation for many years. We studied amphibians in selected outfalls (drainage ditches) flowing from the PGDP to determine if PCBs were accumulating in their tissues and how this might affect local populations. We determined relative amphibian species richness and abundance among seven outfalls and three reference streams

C. J. DeGarady; R. S. Halbrook

2003-01-01

342

Presence of an emerging pathogen of amphibians in introduced bullfrogs Rana catesbeiana in Venezuela  

Microsoft Academic Search

Chytridiomycosis is an emerging fungal disease of amphibians responsible for mass mortalities and population declines globally. One hypothesis for its recent emergence is anthropogenic introduction of the causative agent Batrachochytrium dendrobatidis through trade in amphibians for pets, food and biocontrol. In this study, we examined histological samples from apparently healthy American bullfrogs Rana catesbeiana that have been introduced into the

Rhea Hanselmann; Argelia Rodr??guez; Margarita Lampo; Laurie Fajardo-Ramos; A. Alonso Aguirre; A. Marm Kilpatrick; Jon Paul Rodr??guez; Peter Daszak

2004-01-01

343

CATAWBA RIVER CORRIDOR COVERBOARD PROGRAM: A CITIZEN SCIENCE APPROACH TO AMPHIBIAN AND REPTILE INVENTORY  

Microsoft Academic Search

Coverboards are a useful inventory tool for many species of amphibians and reptiles, and provide a simple and effective method to involve the public in scientific research. The Davidson College Catawba River Corridor Coverboard Program (CRCCP) was initiated in 2003 to help coordinate the efforts of public and private sectors in surveying amphibians and reptiles. Fourteen sites were established within

SHANNON E. PITTMAN; MICHAEL E. DORCAS

344

Evidence for a plagiosauroid amphibian in the upper triassic Huai Hin Lat formation of Thailand  

NASA Astrophysics Data System (ADS)

A dermal bone fragment bearing a peculiar pustulate superficial ornamentation is recorded from the Upper Triassic (Norian) Huai Hin Lat Formation of northeastern Thailand. The specimen is tentatively referred to the temnospondyl amphibian superfamily Plagiosauroidea. Its ornamentation resembles most closely that of Plagiosaurus and Gerrothorax from the Upper Triassic of Europe. This find is the first evidence for a plagiosauroid amphibian in Asia.

Suteethorn, Varavudh; Janvier, Philippe; Morales, Michael

345

Discover Reptiles and Amphibians at the American Museum of Natural History  

NSDL National Science Digital Library

This activity sheet for young children is designed to be completed during a visit to the Museum's Reptiles and Amphibians Hall. The printable two-page handout includes notes about the distinguishing characteristics of reptile and amphibian eggs and a hall map that directs students to 10 numbered display cases, with at least one observation activity to be completed at each.

Simpson, Sharon

346

Influence of forest fragmentation on amphibian diversity in the nature reserve of Ambohitantely, highland Madagascar  

Microsoft Academic Search

In Ambohitantely the rainforest is divided distinctly by pseudosteppe into more than 500 fragments. The amphibian faunas of seven such fragments varying in size from 0.16 to 1250 ha were examined. Twenty-eight amphibian species of two families (Ranidae and Microhylidae) were recorded in the rainforest fragments. The species numbers in the fragments were positively correlated with fragment area and form

Denis Vallan

2000-01-01

347

The Creatures beneath Our Feet: Amphibian Monitors Take to the Road.  

ERIC Educational Resources Information Center

The Nature Conservancy's Berkshire Program involves community volunteers in monitoring migration routes of amphibians that rely on vernal pools for breeding success. Vernal-pool workshops provide basic knowledge of amphibian lifecycles and detailed monitoring instructions. Nighttime field trips for adults and children and monitoring experiences…

Daigle, Cheryl Perusse

1999-01-01

348

Cognitive and Emotional Evaluation of an Amphibian Conservation Program for Elementary School Students  

ERIC Educational Resources Information Center

The authors describe a study aimed at enhancing knowledge about amphibian species. Two classes of 3rd and 4th graders aged 9-11 years participated in the study. In addition, approximately one half of the students participated in an environmental conservation action designated to preserve migrating amphibians. During this action, students…

Randler, Christoph; Ilg, Angelika; Kern, Janina

2005-01-01

349

14 CFR 29.519 - Hull type rotorcraft: Water-based and amphibian.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Hull type rotorcraft: Water-based and amphibian. 29.519 Section 29.519 Aeronautics and Space ...Loads § 29.519 Hull type rotorcraft: Water-based and amphibian. (a) General. For hull type...

2010-01-01

350

14 CFR 29.519 - Hull type rotorcraft: Water-based and amphibian.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Hull type rotorcraft: Water-based and amphibian. 29.519 Section 29.519 Aeronautics and Space ...Loads § 29.519 Hull type rotorcraft: Water-based and amphibian. (a) General. For hull type...

2009-01-01

351

Effects of Agricultural Cultivation on Demographics of Southern High Plains Amphibians  

Microsoft Academic Search

Anthropogenic disturbance of landscapes surrounding wetlands is considered a factor in local and global amphibian declines. Few data exist on the effects of agricultural cultivation of wetland watersheds on amphibians, and results from previous studies are contradictory. Our objective was to test the effects of general anthropogenic land use (cultivation vs. grassland) on the demographics of seven species and three

MATTHEW J. GRAY; LOREN M. SMITH; ROBERTO BRENES

2004-01-01

352

Short Communication What type of amphibian tunnel could reduce road kills?  

Microsoft Academic Search

Increased traffic volumes worldwide are con- tributing to amphibian declines, and measures to reduce the occurrence of road kills are needed. One possible measure is the construction of underpasses through which animals can pass under roads, but little is known about whether amphibians will choose tunnels if given a choice or about their preferences for different tunnel types. We tested

David Lesbarrères; Thierry Lodé; Juha Merilä

2004-01-01

353

The behavioral responses of amphibians and reptiles to microgravity on parabolic flights  

Microsoft Academic Search

In the present study, we exposed 53 animals from 23 different species of amphibians and reptiles to microgravity (?g). This nearly doubles the number of amphibians and reptiles observed so far in ?g. The animals were flown on a parabolic flight, which provided 20–25s of ?g, to better characterize behavioral reactions to abrupt exposure to ?g. Highly fossorial limbless caecilians

Richard J. Wassersug; Lesley Roberts; Jenny Gimian; Elizabeth Hughes; Ryan Saunders; Darren Devison; Jonathan Woodbury; James C. O’Reilly

2005-01-01

354

Amphibian and reptile community response to coarse woody debris manipulations in upland loblolly pine ( Pinus taeda) forests  

Microsoft Academic Search

Coarse woody debris (CWD) has been identified as a key microhabitat component for groups that are moisture and temperature sensitive such as amphibians and reptiles. However, few experimental manipulations have quantitatively assessed amphibian and reptile response to varying CWD volumes within forested environments. We assessed amphibian and reptile response to large-scale, CWD manipulation within managed loblolly pine stands in the

Audrey K. Owens; Kurtis R. Moseley; Timothy S. McCay; Steven B. Castleberry; John C. Kilgo; W. Mark Ford; Castleberry; Steven

2008-01-01

355

THE LARVAL DEVELOPMENT OF CARIDINA PSEUDODENTICULATA (CRUSTACEA: DECAPODA: ATYIDAE) REARED IN THE LABORATORY, WITH A DISCUSSION OF LARVAL METAMORPHOSIS TYPES  

Microsoft Academic Search

The moult and metamorphosis types of Caridina pseudodenticulata were described and compared with the other atyid shrimps in this study. C. pseudodenticulata inhabits lakes or lentic waters of western Taiwan. The eggs of C. pseudodenticulata are larger and fewer than most of atyid shrimps. The newly hatched larvae were benthic and no planktonic behavior was observed. With water temperature of

Hong-Thih Lai

356

Control of body size by oxygen supply reveals size-dependent and size-independent mechanisms of molting and metamorphosis  

PubMed Central

Body size profoundly affects many aspects of animal biology, including metamorphosis, allometry, size-dependent alternative pathways of gene expression, and the social and ecological roles of individuals. However, regulation of body size is one of the fundamental unsolved problems in developmental biology. The control of body size requires a mechanism that assesses size and stops growth within a characteristic range of sizes. Under normal growth conditions in Manduca sexta, the endocrine cascade that causes the brain to initiate metamorphosis starts when the larva reaches a critical weight. Metamorphosis is initiated by a size-sensing mechanism, but the nature of this mechanism has remained elusive. Here we show that this size-sensing mechanism depends on the limited ability of a fixed tracheal system to sustain the oxygen supply to a growing individual. As body mass increases, the demand for oxygen also increases, but the fixed tracheal system does not allow a corresponding increase in oxygen supply. We show that interinstar molting has the same size-related oxygen-dependent mechanism of regulation as metamorphosis. We show that low oxygen tension induces molting at smaller body size, consistent with the hypothesis that under normal growth conditions, body size is regulated by a mechanism that senses oxygen limitation. We also found that under poor growth conditions, larvae may never attain the critical weight but eventually molt regardless. We show that under these conditions, larvae do not use the critical weight mechanism, but instead use a size-independent mechanism that is independent of the brain.

Callier, Viviane; Nijhout, H. Frederik

2011-01-01

357

Metamorphosis and collagen-IV-fragments stimulate innate immune response in the greater wax moth, Galleria mellonella  

Microsoft Academic Search

A novel link between development and immunity in insects is introduced. Transiently enhanced expression of lysozyme, gallerimycin and the insect metalloproteinase inhibitor was discovered at the onset of metamorphosis of the greater wax moth, Galleria mellonella. Relative quantification of mRNAs encoding for these antimicrobial peptides using real-time PCR documents their induced expression during transformation of last instar larvae into prepupae

Boran Altincicek; Andreas Vilcinskas

2006-01-01

358

Compromised metamorphosis and thyroid hormone changes in wood frogs ( Lithobates sylvaticus) raised on reclaimed wetlands on the Athabasca oil sands  

Microsoft Academic Search

The wet landscape approach to oil sands tailings reclamation in the Athabasca Oil Sands region involves creating wetlands from fluid tailings in mined-out pits. We measured time to metamorphosis, thyroid hormone status, and detoxification enzyme (EROD) induction in Wood frog (Lithobates sylvaticus) tadpoles raised on reclaimed oil sands wetlands of different ages [young (?7 yr) vs. old (>7 yr)] and compared data

Blair D. Hersikorn; Judit E. G. Smits

2011-01-01

359

Indomethacin induction of metamorphosis from the asexual stage to sexual stage in the moon jellyfish, Aurelia aurita.  

PubMed

We found while screening a chemical library that indomethacin, an inhibitor of prostaglandin biosynthesis, induced strobilation (metamorphosis from the asexual to sexual stage) in the moon jellyfish, Aurelia aurita. Indomethacin initiated strobilation in a dose-dependent manner, but was not involved in the progression of strobilation. Pharmacological experiments suggested that indomethacin could induce strobilation independently of prostaglandin biosynthesis. PMID:22785488

Kuniyoshi, Hisato; Okumura, Izumi; Kuroda, Rie; Tsujita, Natsumi; Arakawa, Kenji; Shoji, Jun; Saito, Tamio; Osada, Hiroyuki

2012-01-01

360

Amphibian chytrid fungus and ranaviruses in the Northwest Territories, Canada.  

PubMed

Pathogens can cause serious declines in host species, and knowing where pathogens associated with host declines occur facilitates understanding host-pathogen ecology. Suspected drivers of global amphibian declines include infectious diseases, with 2 pathogens in particular, Batrachochytrium dendrobatidis (Bd) and ranaviruses, causing concern. We explored the host range and geographic distribution of Bd and ranaviruses in the Taiga Plains ecoregion of the Northwest Territories, Canada, in 2007 and 2008. Both pathogens were detected, greatly extending their known geographic distributions. Ranaviruses were widespread geographically, but found only in wood frogs. In contrast, Bd was found at a single site, but was detected in all 3 species of amphibians in the survey area (wood frogs, boreal chorus frogs, western toads). The presence of Bd in the Northwest Territories is not congruent with predicted distributions based on niche models, even though findings from other studies at northern latitudes are consistent with those same models. Unexpectedly, we also found evidence that swabs routinely used to collect samples for Bd screening detected fewer infections than toe clips. Our use and handling of the swabs was consistent with other studies, and the cause of the apparent lack of integrity of swabs is unknown. The ranaviruses detected in our study were confirmed to be Frog Virus 3 by sequence analysis of a diagnostic 500 bp region of the major capsid protein gene. It is unknown whether Bd or ranaviruses are recent arrivals to the Canadian north. However, the genetic analyses required to answer that question can inform larger debates about the origin of Bd in North America as well as the potential effects of climate change and industrial development on the distributions of these important amphibian pathogens. PMID:21268986

Schock, Danna M; Ruthig, Gregory R; Collins, James P; Kutz, Susan J; Carrière, Suzanne; Gau, Robert J; Veitch, Alasdair M; Larter, Nicholas C; Tate, Douglas P; Guthrie, Glen; Allaire, Daniel G; Popko, Richard A

2010-11-01

361

The role of multiple stressor causes in declining amphibian populations: A wingspread workshop summary  

USGS Publications Warehouse

Numerous studies have documented the decline of amphibian populations over the past decade and no single factor has been the linked to these widespread declines. Determining the causes of declining amphibian populations worldwide has proven difficult because of the variety of anthropogenic and natural suspect agents. A Wingspread workshop, convened by The Society of Environmental Toxicology and Chemistry (SETAC), brought together individuals with expertise in the areas of amphibian biology, ecotoxicology, natural resource management, and environmental policy. This workshop had three objectives: 1) create a network for future discussions on multiple Stressor causes of declines; 2) characterize and prioritize technical issues critical to the analysis of the decline problem; and 3) identify and develop resource management approaches to promote sustainable and healthy amphibian populations. The workshop proceedings will be summarized in a book entitled, "Multiple Stressors and Declining Amphibian Populations: Evaluating Cause and Effect." This paper summarizes the results of the workshop.

Krest, S. K.; Linder, G.; Sparling, D. W.

2003-01-01

362

The role of multiple stressor causes in declining amphibian populations: a wingspread workshop summary  

USGS Publications Warehouse

Numerous studies have documented the decline of amphibian populations over the past decade and no single factor has been the linked to these widespread declines. Determining the causes of declining amphibian populations worldwide has proven difficult because of the variety of anthropogenic and natural suspect agents. A Wingspread workshop, convened by The Society of Environmental Toxicology and Chemistry (SETAC), brought together individuals with expertise in the areas of amphibian biology, ecotoxicology, natural resource management, and environmental policy. This workshop had three objectives: 1) create a network for future discussions on multiple stressor causes of declines; 2) characterize and prioritize technical issues critical to the analysis of the decline problem; and 3) identify and develop resource management approaches to promote sustainable and healthy amphibian populations. The workshop proceedings will be summarized in a book entitled, 'Multiple Stressors and Declining Amphibian Populations: Evaluating Cause and Effect.' This paper summarizes the results of the workshop.

Krest, S.K.; Linder, G.; Sparling, D. W.

2003-01-01

363

A critical review of freshwater crayfish as amphibian predators: capable consumers of toxic prey?  

PubMed

Consumption of amphibian eggs and larvae by crayfish has been widely reported despite many amphibians being unpalatable and/or toxic to other predators. The aim of this review was to gather information regarding the consumption and/or avoidance of toxic amphibians by these omnivores. We then appraised the extent of toxin consumptive ability in terms of crayfish phylogenetic history so as to speculate as to the evolutionary history of this trait. Reports indicating an ability to tolerate amphibian toxins were collected and reviewed for 12 freshwater crayfish species. In reviewing these, we have established that freshwater crayfish appear to be tolerant of a range of toxic amphibians, often consuming large numbers of eggs and larvae without lethal or apparent sublethal effects. Toxin tolerance was evident within both superfamilies (Astacoidea and Parastacoidea) suggesting that tolerance may be a primitive trait in freshwater crayfish. PMID:24556015

Wilson, Natasha J; Williams, Craig R

2014-05-01

364

Turtle isochore structure is intermediate between amphibians and other amniotes.  

PubMed

Vertebrate genomes are comprised of isochores that are relatively long (>100 kb) regions with a relatively homogenous (either GC-rich or AT-rich) base composition and with rather sharp boundaries with neighboring isochores. Mammals and living archosaurs (birds and crocodilians) have heterogeneous genomes that include very GC-rich isochores. In sharp contrast, the genomes of amphibians and fishes are more homogeneous and they have a lower overall GC content. Because DNA with higher GC content is more thermostable, the elevated GC content of mammalian and archosaurian DNA has been hypothesized to be an adaptation to higher body temperatures. This hypothesis can be tested by examining structure of isochores across the reptilian clade, which includes the archosaurs, testudines (turtles), and lepidosaurs (lizards and snakes), because reptiles exhibit diverse body sizes, metabolic rates, and patterns of thermoregulation. This study focuses on a comparative analysis of a new set of expressed genes of the red-eared slider turtle and orthologs of the turtle genes in mammalian (human, mouse, dog, and opossum), archosaurian (chicken and alligator), and amphibian (western clawed frog) genomes. EST (expressed sequence tag) data from a turtle cDNA library enriched for genes that have specialized functions (developmental genes) revealed using the GC content of the third-codon-position to examine isochore structure requires careful consideration of the types of genes examined. The more highly expressed genes (e.g., housekeeping genes) are more likely to be GC-rich than are genes with specialized functions. However, the set of highly expressed turtle genes demonstrated that the turtle genome has a GC content that is intermediate between the GC-poor amphibians and the GC-rich mammals and archosaurs. There was a strong correlation between the GC content of all turtle genes and the GC content of other vertebrate genes, with the slope of the line describing this relationship also indicating that the isochore structure of turtles is intermediate between that of amphibians and other amniotes. These data are consistent with some thermal hypotheses of isochore evolution, but we believe that the credible set of models for isochore evolution still includes a variety of models. These data expand the amount of genomic data available from reptiles upon which future studies of reptilian genomics can build. PMID:21669806

Chojnowski, Jena L; Braun, Edward L

2008-10-01

365

Incorporating Amphibian Malformation into Inquiry-Based Learning  

NSDL National Science Digital Library

Since the first discovery of malformed frogs by an adventurous middle school teacher and her after-school science club in 1995, outreach programs like A Thousand Friends of Frogs (see Resources) have been created to connect students and teachers with scientists so that they can better understand frogs and their habitats. Many of the amphibian-malformation activities published in education-practitioner journals approach this subject through internet investigations (Webster 2002), hypothetical case studies (Murphy and Fortner 2001), or reading with discussion (Davidson, Matthews, and Patrick 2001). These activities can be supplemented with inquiry-based labs designed to instruct and engage students about conservation biology, as described in this article.

Talley, Brooke L.

2007-01-01

366

Parallels in Amphibian and Bat Declines from Pathogenic Fungi  

PubMed Central

Pathogenic fungi have substantial effects on global biodiversity, and 2 emerging pathogenic species—the chytridiomycete Batrachochytrium dendrobatidis, which causes chytridiomycosis in amphibians, and the ascomycete Geomyces destructans, which causes white-nose syndrome in hibernating bats—are implicated in the widespread decline of their vertebrate hosts. We synthesized current knowledge for chytridiomycosis and white-nose syndrome regarding disease emergence, environmental reservoirs, life history characteristics of the host, and host–pathogen interactions. We found striking similarities between these aspects of chytridiomycosis and white-nose syndrome, and the research that we review and propose should help guide management of future emerging fungal diseases.

Eskew, Evan A.

2013-01-01

367

Reptiles and amphibians as targets for nature management  

Microsoft Academic Search

This thesis deals with the nature conservation of reptiles and amphibians in the<\\/span>Netherlands<\\/span><\\/st1:country-region><\\/st1:place>, the present practices and what should be done to improve them. Most of the species of the herpetofauna, as these groups together are known, are in a state of continuing decline. Obviously something is wrong; apart from the role played in this decline

A. H. P. Stumpel

2004-01-01

368

Behavioral, molecular and integrative mechanisms of amphibian osmoregulation.  

PubMed

Amphibian water balance has been studied at many levels of biological order. Terrestrial species must react to environmental cues that relate to water availability while some arboreal species have cutaneous skin secretions that can reduce evaporative water loss. The Indian tree frog. Polypedates maculatus, uses cutaneous secretions and wiping behavior to lower evaporation but also relies on moist microclimates to endure prolonged survival away from water. The related species, P. leucomystax, inhabits wetter forest habitats. Preliminary studies with this species are unable to demonstrate the expression of wiping behavior, indicating that arid habitats may be a powerful selective force for this behavior. Laboratory experiments on rehydrating toads in the genus Bufo indicate that animals are able to detect changes in barometric pressure and humidity that might result in the availability of water under field situations. Experiments with Bufonid species and with spadefoot toads, Scaphiopus couchi, show that the peptide hormone, angiotensin II, stimulates cutaneous drinking in a similar manner seen for oral drinking by other vertebrate classes. Amphibian tissues have long been used as a model for the study of basic physiological principles of epithelial ion and water transport. Recent progress with tissue cultures has provided information on the molecular structure of ion and water channels that can be applied to obtain a better understanding, at the molecular level, of ion and water balance strategies used by the wide variety of amphibian species. Terrestrial amphibians are more tolerant of dehydration than are other vertebrates and are able to store dilute urine in their urinary bladder. Toads appear to be able to detect the presence of water in their bladders in addition to the availability of water in their environment. Dehydrated toads are able to rehydrate very rapidly by the coordination of behavioral and physiological mechanisms to enhance cutaneous water absorption. The integration of behavior with cutaneous water gain, renal handling of ions and water and the role of the lymphatic system in overall water balance involves complex interactions between neural and hormonal factors. Experiments are summarized that describe the contribution of individual factors however much more information is needed before the nature of these interactions are fully understood. PMID:10222590

Hillyard, S D

1999-06-01

369

Metamorphosis in Balanomorphan, Pedunculated, and Parasitic Barnacles: A Video-Based Analysis  

PubMed Central

Cypris metamorphosis was followed using video microscopy in four species of cirripeds representing the suspension-feeding pedunculated and sessile Thoracica and the parasitic Rhizocephala. Cirripede metamorphosis involves one or more highly complex molts that mark the change from a free cypris larva to an attached suspension feeder (Thoracica) or an endoparasite (Rhizocephala). The cyprids and juveniles are so different in morphology that they are functionally incompatible. The drastic reorganization of the body implicated in the process can therefore only commence after the cyprid has irreversibly cemented itself to a substratum. In both Megabalanus rosa and Lepas, the settled cyprid first passes through a quiescent period of tissue reorganization, in which the body is raised into a position vertical to the substratum. In Lepas, this is followed by extension of the peduncle. In both Lepas and M. rosa, the juvenile must free itself from the cypris cuticle by an active process before it can extend the cirri for suspension feeding. In M. rosa, the juvenile performs intensely pulsating movements that result in shedding of the cypris carapace ?8?h after settlement. Lepas sp. sheds the cypris cuticle ?2 days after settlement due to contractile movements of the peduncle. In Lepas anserifera, the juvenile actively breaks through the cypris carapace, which can thereafter remain for several days without impeding cirral feeding. Formation of the shell plates begins after 1-2 days under the cyprid carapace in Lepas. In M. rosa, the free juvenile retains its very thin cuticle and flexible shape for some time, and shell plates do not appear until sometime after shedding of the cypris cuticles. In Sacculina carcini, the cypris settles at the base of a seta on the host crab and remains quiescent and aligned at an angle of ?60° to the crab’s cuticle. The metamorphosis involves two molts, resulting in the formation of an elongated kentrogon stage with a hollow injection stylet. Due to the orientation of the cyprid, the stylet points directly towards the base of the crab’s seta. Approximately 60?h after settlement the stylet penetrates down one of the cyprid antennules and into the crab. Almost immediately afterwards the unsegmented vermigon stage, preformed in the kentrogon, passes down through the hollow stylet and into the crab’s hemocoel in a process lasting only 30?s. In S. carcini, the carapace can remain around the metamorphosing individual without impeding the process.

H?eg, Jens T.; Maruzzo, Diego; Okano, Keiju; Glenner, Henrik; Chan, Benny K.K.

2012-01-01

370

Midlife Metamorphosis  

ERIC Educational Resources Information Center

The study was conducted in response to the need for an increased understanding of the aging experiences of women transitioning midlife. The purpose of the research was to explore the personal understanding of the changes that occur during the midlife period. A qualitative case study was implemented to ascertain how women of the Latter-day Saint…

Evans, Patricia

2008-01-01

371

Transcriptional regulation of juvenile hormone-mediated induction of Kr?ppel homolog 1, a repressor of insect metamorphosis  

PubMed Central

The Krüppel homolog 1 gene (Kr-h1) has been proposed to play a key role in the repression of insect metamorphosis. Kr-h1 is assumed to be induced by juvenile hormone (JH) via a JH receptor, methoprene-tolerant (Met), but the mechanism of induction is unclear. To elucidate the molecular mechanism of Kr-h1 induction, we first cloned cDNAs encoding Kr-h1 (BmKr-h1) and Met (BmMet1 and BmMet2) homologs from Bombyx mori. In a B. mori cell line, BmKr-h1 was rapidly induced by subnanomolar levels of natural JHs. Reporter assays identified a JH response element (kJHRE), comprising 141 nucleotides, located ?2 kb upstream from the BmKr-h1 transcription start site. The core region of kJHRE (GGCCTCCACGTG) contains a canonical E-box sequence to which Met, a basic helix–loop–helix Per-ARNT-Sim (bHLH–PAS) transcription factor, is likely to bind. In mammalian HEK293 cells, which lack an intrinsic JH receptor, ectopic expression of BmMet2 fused with Gal4DBD induced JH-dependent activity of an upstream activation sequence reporter. Meanwhile, the kJHRE reporter was activated JH-dependently in HEK293 cells only when cotransfected with BmMet2 and BmSRC, another bHLH–PAS family member, suggesting that BmMet2 and BmSRC jointly interact with kJHRE. We also found that the interaction between BmMet2 and BmSRC is dependent on JH. Therefore, we propose the following hypothesis for the mechanism of JH-mediated induction of BmKr-h1: BmMet2 accepts JH as a ligand, JH-liganded BmMet2 interacts with BmSRC, and the JH/BmMet2/BmSRC complex activates BmKr-h1 by interacting with kJHRE.

Kayukawa, Takumi; Minakuchi, Chieka; Namiki, Toshiki; Togawa, Toru; Yoshiyama, Michiyo; Kamimura, Manabu; Mita, Kazuei; Imanishi, Shigeo; Kiuchi, Makoto; Ishikawa, Yukio; Shinoda, Tetsuro

2012-01-01

372

UV-B Radiation Contributes to Amphibian Population Declines  

NASA Astrophysics Data System (ADS)

UV-B (280-315 nm) radiation is the most significant biologically damaging radiation at the terrestrial surface. At the organismal level, UV-B radiation can slow growth rates, cause immune dysfunction and result in sublethal damage. UV-B radiation can lead to mutations and cell death. Over evolutionary time, UV radiation has been an important stressor on living organisms. Natural events, including impacts from comets and asteroids, volcanic activity, supernova explosions and solar flares, can cause large-scale ozone depletion with accompanying increases in UV radiation. However, these natural events are transient. Moreover, the amount of ozone damage due to natural events depends upon a number of variables, including the magnitude of the event. This is different from modern-day human-induced production of chlorofluorocarbons (CFCs) and other chemicals that deplete stratospheric ozone continuously, resulting in long-term increases in UV-B radiation at the surface of the earth. We will briefly review the effects of UV-B exposure in one group of aquatic organisms_amphibians. UV-B has been implicated as a possible factor contributing to global declines and range reductions in amphibian populations.

Blaustein, Andrew

2007-05-01

373

Origin and functional diversification of an amphibian defense peptide arsenal.  

PubMed

The skin secretion of many amphibians contains an arsenal of bioactive molecules, including hormone-like peptides (HLPs) acting as defense toxins against predators, and antimicrobial peptides (AMPs) providing protection against infectious microorganisms. Several amphibian taxa seem to have independently acquired the genes to produce skin-secreted peptide arsenals, but it remains unknown how these originated from a non-defensive ancestral gene and evolved diverse defense functions against predators and pathogens. We conducted transcriptome, genome, peptidome and phylogenetic analyses to chart the full gene repertoire underlying the defense peptide arsenal of the frog Silurana tropicalis and reconstruct its evolutionary history. Our study uncovers a cluster of 13 transcriptionally active genes, together encoding up to 19 peptides, including diverse HLP homologues and AMPs. This gene cluster arose from a duplicated gastrointestinal hormone gene that attained a HLP-like defense function after major remodeling of its promoter region. Instead, new defense functions, including antimicrobial activity, arose by mutation of the precursor proteins, resulting in the proteolytic processing of secondary peptides alongside the original ones. Although gene duplication did not trigger functional innovation, it may have subsequently facilitated the convergent loss of the original function in multiple gene lineages (subfunctionalization), completing their transformation from HLP gene to AMP gene. The processing of multiple peptides from a single precursor entails a mechanism through which peptide-encoding genes may establish new functions without the need for gene duplication to avoid adaptive conflicts with older ones. PMID:23935531

Roelants, Kim; Fry, Bryan G; Ye, Lumeng; Stijlemans, Benoit; Brys, Lea; Kok, Philippe; Clynen, Elke; Schoofs, Liliane; Cornelis, Pierre; Bossuyt, Franky

2013-01-01

374

Proximity to Pollution Sources and Risk of Amphibian Limb Malformation  

PubMed Central

The cause of limb deformities in wild amphibian populations remains unclear, even though the apparent increase in prevalence of this condition may have implications for human health. Few studies have simultaneously assessed the effect of multiple exposures on the risk of limb deformities. In a cross-sectional survey of 5,264 hylid and ranid metamorphs in 42 Vermont wetlands, we assessed independent risk factors for nontraumatic limb malformation. The rate of nontraumatic limb malformation varied by location from 0 to 10.2%. Analysis of a subsample did not demonstrate any evidence of infection with the parasite Ribeiroia. We used geographic information system (GIS) land-use/land-cover data to validate field observations of land use in the proximity of study wetlands. In a multiple logistic regression model that included land use as well as developmental stage, genus, and water-quality measures, proximity to agricultural land use was associated with an increased risk of limb malformation (odds ratio = 2.26; 95% confidence interval, 1.42–3.58; p < 0.001). The overall discriminant power of the statistical model was high (C = 0.79). These findings from one of the largest systematic surveys to date provide support for the role of chemical toxicants in the development of amphibian limb malformation and demonstrate the value of an epidemiologic approach to this problem.

Taylor, Brynn; Skelly, David; Demarchis, Livia K.; Slade, Martin D.; Galusha, Deron; Rabinowitz, Peter M.

2005-01-01

375

Origin and Functional Diversification of an Amphibian Defense Peptide Arsenal  

PubMed Central

The skin secretion of many amphibians contains an arsenal of bioactive molecules, including hormone-like peptides (HLPs) acting as defense toxins against predators, and antimicrobial peptides (AMPs) providing protection against infectious microorganisms. Several amphibian taxa seem to have independently acquired the genes to produce skin-secreted peptide arsenals, but it remains unknown how these originated from a non-defensive ancestral gene and evolved diverse defense functions against predators and pathogens. We conducted transcriptome, genome, peptidome and phylogenetic analyses to chart the full gene repertoire underlying the defense peptide arsenal of the frog Silurana tropicalis and reconstruct its evolutionary history. Our study uncovers a cluster of 13 transcriptionally active genes, together encoding up to 19 peptides, including diverse HLP homologues and AMPs. This gene cluster arose from a duplicated gastrointestinal hormone gene that attained a HLP-like defense function after major remodeling of its promoter region. Instead, new defense functions, including antimicrobial activity, arose by mutation of the precursor proteins, resulting in the proteolytic processing of secondary peptides alongside the original ones. Although gene duplication did not trigger functional innovation, it may have subsequently facilitated the convergent loss of the original function in multiple gene lineages (subfunctionalization), completing their transformation from HLP gene to AMP gene. The processing of multiple peptides from a single precursor entails a mechanism through which peptide-encoding genes may establish new functions without the need for gene duplication to avoid adaptive conflicts with older ones.

Roelants, Kim; Fry, Bryan G.; Ye, Lumeng; Stijlemans, Benoit; Brys, Lea; Kok, Philippe; Clynen, Elke; Schoofs, Liliane; Cornelis, Pierre; Bossuyt, Franky

2013-01-01

376

A dilution effect in the emerging amphibian pathogen Batrachochytrium dendrobatidis  

PubMed Central

Global declines in biodiversity are altering disease dynamics in complex and multifaceted ways. Changes in biodiversity can have several outcomes on disease risk, including dilution and amplification effects, both of which can have a profound influence on the effects of disease in a community. The dilution effect occurs when biodiversity and disease risk are inversely related, whereas the amplification effect is a positive relationship between biodiversity and disease risk. We tested these effects with an emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis (Bd), which is responsible for catastrophic amphibian population declines and extinctions worldwide. Despite the rapid and continued spread of Bd, the influence of host diversity on Bd dynamics remains unknown. We experimentally manipulated host diversity and density in the presence of Bd and found a dilution effect where increased species richness reduced disease risk, even when accounting for changes in density. These results demonstrate the general importance of incorporating community structure into studies of disease dynamics and have implications for the effects of Bd in ecosystems that differ in biodiversity.

Searle, Catherine L.; Biga, Lindsay M.; Spatafora, Joseph W.; Blaustein, Andrew R.

2011-01-01

377

Radioautographic investigation of retinal growth in mature amphibians  

SciTech Connect

Growth of the retina was studied in mature intact amphibians, tritons, axolotls, ambystomas and clawed frogs, for six months using multiple injection of /sup 3/H-thymidine. It was established that the source of replenishment of the retina by new cells is its terminal zone in all animals investigated. This is attested to by the gradual migration of labeled cells from the growth zone into differentiated layers of the retina. The most intensely labeled cells occupy a distal position relative to other labeled cells, therefore marking the boundary between the initial part of the retina, not containing labeled nuclei, and the part being augmented. For each species studied, a level of proliferative activity is characteristic for cells of the terminal zone, which decreases in the order axolotl-clawed frog-triton -ambystoma. In the axolotl and additional growth zone is noted in the retina, in addition to the terminal, which is located in the area of the unclosed section of the embryonic fissure. Results obtained serve as a basis for the regenerative potentials of eye tissues revealed previously in these amphibian species.

Svistunov, S.A.; Mitashov, V.I.

1986-07-01

378

Interactions of Amphibians, Fish, and Macroinvertebrates in a Southeastern Wetland  

NASA Astrophysics Data System (ADS)

In fishless habitats, amphibians often compete with and are predators of macroinvertebrates. Unlike fish, the effects these interactions have on macroinvertebrate communities have been largely unexplored. We conducted an experiment in a semi-permanent oxbow wetland in the Piedmont region of Georgia to explore interactions between amphibians and macroinvertebrates. The predator community was dominated by Ambystoma opacum (Marbled Salamander) and Notophthalmus viridescens (Eastern Newt). Salamanders and newts were excluded from areas of wetland habitat using wire mesh cages (1.5M x 1.5M, 3mm mesh). The macroinvertebrate communities within the cages were then compared to the ambient habitat outside the cages. Fish, mostly Lepomis macrochirus (Bluegill) and Gambusia affinis (Mosquito Fish), colonized the wetland late in the first year of the study, and became common by year two. Also in year two, Rana catesbeiana (Bullfrog) became established. Thus, we were able to explore the variable effects on the macroinvertebrate community of a changing predator complex over a two year period.

Schultheis, R. D.; Batzer, D. P.

2005-05-01

379

Variations in lethal and sublethal effects of cypermethrin among aquatic stages and species of anuran amphibians.  

PubMed

Despite the use of model species to predict the effects of chemicals in the environment, unpredicted variation in levels of risk to organisms from xenobiotics can be observed. Physiological and morphological differences between species and life stages may lead to differences in sensitivity, while seasonal and spatial variation in pesticide concentrations may affect the level of risk faced by organisms in the environment. Because anurans breed in aquatic habitats subject to contamination by runoff and spraying, they are particularly vulnerable to pesticides. In the present study, embryos, newly hatched larvae, and larvae with limb buds of 3 anuran amphibian species--Pseudacris regilla, Rana cascadae, and Rana aurora--were exposed for 48?h to either 0.5?µg/L or 5.0?µg/L cypermethrin under laboratory conditions. The authors monitored hatching success, larval survival, and measured growth. Additionally, they assayed avoidance behavior 2 wk after exposure or 2 wk after hatching for individuals exposed as embryos. Hatching and survival were not affected in animals of any species exposed as embryos. After exposure as embryos and as newly hatched larvae, however, P. regilla displayed behavioral abnormalities in response to prodding. Cypermethrin increased mortality in P. regilla exposed in both larval stages. Cypermethrin also increased mortality in larval R. cascadae when exposed at the early stage. These results indicate variation in sensitivity to environmentally relevant concentrations of cypermethrin among anuran species and life stages. PMID:23999991

Biga, Lindsay M; Blaustein, Andrew R

2013-12-01

380

Broad relays hormone signals to regulate stem cell differentiation in Drosophila midgut during metamorphosis  

PubMed Central

Like the mammalian intestine, the Drosophila adult midgut is constantly replenished by multipotent intestinal stem cells (ISCs). Although it is well known that adult ISCs arise from adult midgut progenitors (AMPs), relatively little is known about the mechanisms that regulate AMP specification. Here, we demonstrate that Broad (Br)-mediated hormone signaling regulates AMP specification. Br is highly expressed in AMPs temporally during the larva-pupa transition stage, and br loss of function blocks AMP differentiation. Furthermore, Br is required for AMPs to develop into functional ISCs. Conversely, br overexpression drives AMPs toward premature differentiation. In addition, we found that Br and Notch (N) signaling function in parallel pathways to regulate AMP differentiation. Our results reveal a molecular mechanism whereby Br-mediated hormone signaling directly regulates stem cells to generate adult cells during metamorphosis.

Zeng, Xiankun; Hou, Steven X.

2012-01-01

381

Groups travel further: pelagic metamorphosis and polyp clustering allow higher dispersal potential in sun coral propagules  

NASA Astrophysics Data System (ADS)

We report that planulae produced by Tubastraea coccinea can metamorphose and aggregate in groups of up to eight polyps in the water column, without previous settlement on benthic substrate. We also evaluated the survival of propagules to test whether different levels of aggregation allowed for longer planktonic life and, therefore, higher dispersal potential. Our results show that pelagic polyps live longer than planulae, probably because they can feed and meet the presumably high-energy demands of swimming. Clusters of two or more individuals lived longer than solitary polyps. However, mortality did not differ between small (2-3 polyps) and large (4-8 polyps) clusters, suggesting the existence of an upper limit to cluster size. Most swimming clusters (80 %) remained alive after 6 months, suggesting that pelagic metamorphosis and cluster formation can be a key life-history feature increasing dispersal potential, population connectivity, and the colonization of new habitats in this invasive species.

Mizrahi, Damián; Navarrete, Sergio A.; Flores, Augusto A. V.

2014-06-01

382

Group-Advantaged Training of Research (GATOR): A Metamorphosis of Mentorship  

NSDL National Science Digital Library

We describe Group-Advantaged Training of Research (GATOR), a yearlong structured program at the University of Florida that guided graduate student mentors and their undergraduate mentees through the mentored research process. Using the national Survey of Undergraduate Research Experiences for an academic year, we found that outcomes for our mentees were similar to those for other programs. We also used an internal survey, combined with qualitative observations, to develop a road map of the mentoring process, which we call the "Metamorphosis of Mentorship." This model provides tangible steps on the road to becoming a scientist, incorporates reasons mentees stall in research, and suggests ways to overcome mentoring challenges and prevent attrition. The structure and outcomes of this program will be useful to researchers and administrators working to engage undergraduates in scientific research, particularly at large universities where undergraduates are often mentored by graduate students.

Thea Edwards (Louisiana Tech University;)

2011-04-01

383

Expressions and localizations of Bax/Bcl-2 proteins during metamorphosis of Pelophylax ridibundus.  

PubMed

Bcl-2 and Bax proteins are expressed in cells of the tails of Pelophylax ridibundus larvae. We investigated the levels of these proteins in tails undergoing apoptosis. Apoptotic cells were observed in the epidermis, muscle and notochord of tails of different lengths. The apoptotic cells in epidermis exhibited the typical features of apoptosis. Amorphous masses and irregularities in striated muscle tissue undergoing apoptosis and apoptotic remnants in the notochord also were observed. In general, Bax staining in the epidermis, subepidermal fibroblast layer, muscle and notochord cells increased, while Bcl-2 staining decreased as the tail regressed. Our results suggest that during tail regression due to metamorphosis, Bcl-2 and Bax proteins play key roles in the apoptosis of tail epidermis, subepidermal fibroblast layer, muscle and notochord cells. PMID:23957704

Ba??mo?lu Koca, Y; Koca, S

2014-01-01

384

Metamorphosis in drosophila and other insects: the fate of neurons throughout the stages.  

PubMed

The nervous system of insects is profoundly reorganised during metamorphosis, affecting the fate of different types of neuron in different ways. Almost all adult motor neurons derive from larval motor neurons that are respecified for adult functions. A subset of larval motor neurons, those which mediate larval- or ecdysis-specific behaviours, die before and immediately after eclosion, respectively. Many adult interneurons develop from larval interneurons, whereas those related to complex adult sense organs originate during larval life from persisting embryonic neuroblasts. Sensory neurons of larvae and adults derive from essentially two distinct sources. Larval sensory neurons are formed in the embryonic integument and - with few exceptions - die during metamorphosis. Their adult counterparts, on the other hand, arise from imaginal discs. Special emphasis is given in this review to the metamorphic remodelling of persisting neurons, both at the input and output levels, and to the associated behavioural changes. Other sections deal with the programmed death of motor neurons and its causes, as well as with the metamorphic interactions between motor neurons and their target muscles. Remodelling and apoptosis of these two elements appear to be under independent ecdysteroid control. This review focusses on the two most thoroughly studied holometabolous species, the fruitfly Drosophila melanogaster and the tobacco hornworm moth Manduca sexta. While Manduca has a long tradition in neurodevelopmental studies due to the identification of many of its neurons, Drosophila has been increasingly used to investigate neural reorganisation thanks to neurogenetic tools and molecular approaches. The wealth of information available emphasises the strength of the insect model system used in developmental studies, rendering it clearly the most important system for studies at the cellular level. PMID:10821983

Tissot, M; Stocker, R F

2000-09-01

385

Immune responses during the larval stages of Mytilus galloprovincialis: metamorphosis alters immunocompetence, body shape and behavior.  

PubMed

We investigated the development of the immune system during the larval stages of the mussel Mytilus galloprovincialis. The ability of trochophore and veliger larvae to phagocytose foreign particles (Escherichia coli and zymosan) was measured. Phagocytosis was detected as early as 24 h post-fertilization (hpf) using flow cytometry and fluorescence microscopy. However, although there was a high basal production of reactive oxygen and nitrogen species (ROS and NRS), the phagocytosis of zymosan did not trigger an associated increase in radical production. In addition, a panel of immune-related mussel genes (Myticin B, Myticin C, Mytilin B, Mytimycin precursor 1, Macrophage migration inhibition factor, lysozyme, C1q, membrane attack complex protein and fibrinogen-related protein) was selected for expression profile analysis throughout the different developmental stages (trochophore, veliger, metamorphosis, post-settlement and spat). The expression of these genes increased during the transition from trochophore to spat, and the level of expression was higher in oocytes than in trochophores, suggesting that gene expression during the first larval stages might be maternal in origin. Metamorphosis was identified as a crucial stage when larvae increased the expression of immune-related genes and responded to environmental signals. Whole-mount in situ hybridization studies showed the mantle edge as an important area in the development of immunocompetence in bivalve larvae. Larvae responded to both live and heat-inactivated bacteria by modulating expression of immune-related genes. Altogether, our results support that during the early stages of M. galloprovincialis development, immune mechanisms emerge to aid larvae in managing infections. PMID:23684811

Balseiro, Pablo; Moreira, Rebeca; Chamorro, Rubén; Figueras, Antonio; Novoa, Beatriz

2013-08-01

386

Glial remodeling during metamorphosis influences the stabilization of motor neuron branches in Drosophila.  

PubMed

Motor neurons that innervate the dorsal longitudinal (flight) muscles, DLMs, make multiple points of contact along the length of fibers. The stereotypy of the innervation lies in the number of contact points (CPs) made by each motor neuron and is established as a consequence of pruning that occurs during metamorphosis. Coincident with the onset of pruning is the arrival of glial processes that eventually ensheath persistent branches. To test a possible role for glia during pruning, the development of adult-specific glial ensheathment was disrupted using a targeted expression of dominant negative shibire. Such a manipulation resulted in fewer contact points at the DLM fibers. The development of innervation was examined during metamorphosis, specifically to test if the reduction was a consequence of increased pruning. We quantified the number of branches displaying discontinuities in their membrane, an indicator of the level of pruning. Disrupting the formation of glial ensheathment resulted in a two-fold increase in the discontinuities, indicating that pruning is enhanced. Thus glial-neuronal interactions, specifically during pruning are important for the patterning of adult innervation. Our studies also suggest that FasII plays a role in mediating this communication. At the end of the pruning phase, FasII localizes to glia, which envelops each of the stabilized contact points. When glial FasII levels are increased using the Gal4/UAS system of targeted expression, pruning of secondary branches is enhanced. Our results indicate that glia regulate pruning of secondary branches by influencing the balance between stabilization and pruning. This was confirmed by an observed rescue of the innervation phenotype of FasII hypomorphs by over expressing FasII in glia. PMID:20079727

Hebbar, Sarita; Fernandes, Joyce J

2010-04-15

387

Ionoregulatory changes during metamorphosis and salinity exposure of juvenile sea lamprey (Petromyzon marinus L.)  

USGS Publications Warehouse

Ammocoetes of the anadromous sea lamprey Petromyzon marinus L. spend many years in freshwater before metamorphosing and migrating to sea. Metamorphosis involves the radical transformation from a substrate-dwelling, filter feeder into a free-swimming, parasitic feeder. In the present work we examined osmoregulatory differences between ammocoetes and transformers (metamorphic juveniles), and the effects of salinity acclimation. We measured the expression of key ion-transporting proteins [Na+/K+-ATPase, vacuolar (V)-type H+-ATPase and carbonic anhydrase (CA)] as well as a number of relevant blood parameters (hematocrit, [Na+] and [Cl -]). In addition, immunofluorescence microscopy was used to identify and characterize the distributions of Na+/K+-ATPase, V-type H+-ATPase and CA immunoreactive cells in the gill. Ammocoetes did not survive in the experiments with salinities greater than 10???, whereas survival in high salinity (???25-35???) increased with increased degree of metamorphosis in transformers. Plasma [Na+] and [Cl -] of ammocoetes in freshwater was lower than transformers and increased markedly at 10???. In transformers, plasma ions increased only at high salinity (>25???). Branchial Na+/K+-ATPase levels were ??? tenfold higher in transformers compared to ammocoetes and salinity did not affect expression in either group. However, branchial H +-ATPase expression showed a negative correlation with salinity in both groups. Na+/K+-ATPase immunoreactivity was strongest in transformers and associated with clusters of cells in the interlamellar spaces. H+-ATPase (B subunit) immunoreactivity was localized to epithelial cells not expressing high Na+/K+-ATPase immunoreactivity and having a similar tissue distribution as carbonic anhydrase. The results indicate that branchial Na+/K+-ATPase and salinity tolerance increase in metamorphosing lampreys, and that branchial H+-ATPase is downregulated by salinity.

Reis-Santos, P.; McCormick, S. D.; Wilson, J. M.

2008-01-01

388

Differential Gene Expression at Coral Settlement and Metamorphosis - A Subtractive Hybridization Study  

PubMed Central

Background A successful metamorphosis from a planktonic larva to a settled polyp, which under favorable conditions will establish a future colony, is critical for the survival of corals. However, in contrast to the situation in other animals, e.g., frogs and insects, little is known about the molecular basis of coral metamorphosis. We have begun to redress this situation with previous microarray studies, but there is still a great deal to learn. In the present paper we have utilized a different technology, subtractive hybridization, to characterize genes differentially expressed across this developmental transition and to compare the success of this method to microarray. Methodology/Principal Findings Suppressive subtractive hybridization (SSH) was used to identify two pools of transcripts from the coral, Acropora millepora. One is enriched for transcripts expressed at higher levels at the pre-settlement stage, and the other for transcripts expressed at higher levels at the post-settlement stage. Virtual northern blots were used to demonstrate the efficacy of the subtractive hybridization technique. Both pools contain transcripts coding for proteins in various functional classes but transcriptional regulatory proteins were represented more frequently in the post-settlement pool. Approximately 18% of the transcripts showed no significant similarity to any other sequence on the public databases. Transcripts of particular interest were further characterized by in situ hybridization, which showed that many are regulated spatially as well as temporally. Notably, many transcripts exhibit axially restricted expression patterns that correlate with the pool from which they were isolated. Several transcripts are expressed in patterns consistent with a role in calcification. Conclusions We have characterized over 200 transcripts that are differentially expressed between the planula larva and post-settlement polyp of the coral, Acropora millepora. Sequence, putative function, and in some cases temporal and spatial expression are reported.

Hayward, David C.; Hetherington, Suzannah; Behm, Carolyn A.; Grasso, Lauretta C.; Foret, Sylvain; Miller, David J.; Ball, Eldon E.

2011-01-01

389

DNA barcoding applied to ex situ tropical amphibian conservation programme reveals cryptic diversity in captive populations.  

PubMed

Amphibians constitute a diverse yet still incompletely characterized clade of vertebrates, in which new species are still being discovered and described at a high rate. Amphibians are also increasingly endangered, due in part to disease-driven threats of extinctions. As an emergency response, conservationists have begun ex situ assurance colonies for priority species. The abundance of cryptic amphibian diversity, however, may cause problems for ex situ conservation. In this study we used a DNA barcoding approach to survey mitochondrial DNA (mtDNA) variation in captive populations of 10 species of Neotropical amphibians maintained in an ex situ assurance programme at El Valle Amphibian Conservation Center (EVACC) in the Republic of Panama. We combined these mtDNA sequences with genetic data from presumably conspecific wild populations sampled from across Panama, and applied genetic distance-based and character-based analyses to identify cryptic lineages. We found that three of ten species harboured substantial cryptic genetic diversity within EVACC, and an additional three species harboured cryptic diversity among wild populations, but not in captivity. Ex situ conservation efforts focused on amphibians are therefore vulnerable to an incomplete taxonomy leading to misidentification among cryptic species. DNA barcoding may therefore provide a simple, standardized protocol to identify cryptic diversity readily applicable to any amphibian community. PMID:23280343

Crawford, Andrew J; Cruz, Catalina; Griffith, Edgardo; Ross, Heidi; Ibáñez, Roberto; Lips, Karen R; Driskell, Amy C; Bermingham, Eldredge; Crump, Paul

2013-11-01

390

Drought, Deluge and Declines: The Impact of Precipitation Extremes on Amphibians in a Changing Climate  

PubMed Central

The Class Amphibia is one of the most severely impacted taxa in an on-going global biodiversity crisis. Because amphibian reproduction is tightly associated with the presence of water, climatic changes that affect water availability pose a particularly menacing threat to both aquatic and terrestrial-breeding amphibians. We explore the impacts that one facet of climate change—that of extreme variation in precipitation—may have on amphibians. This variation is manifested principally as increases in the incidence and severity of both drought and major storm events. We stress the need to consider not only total precipitation amounts but also the pattern and timing of rainfall events. Such rainfall “pulses” are likely to become increasingly more influential on amphibians, especially in relation to seasonal reproduction. Changes in reproductive phenology can strongly influence the outcome of competitive and predatory interactions, thus potentially altering community dynamics in assemblages of co-existing species. We present a conceptual model to illustrate possible landscape and metapopulation consequences of alternative climate change scenarios for pond-breeding amphibians, using the Mole Salamander, Ambystoma talpoideum, as an example. Although amphibians have evolved a variety of life history strategies that enable them to cope with environmental uncertainty, it is unclear whether adaptations can keep pace with the escalating rate of climate change. Climate change, especially in combination with other stressors, is a daunting challenge for the persistence of amphibians and, thus, the conservation of global biodiversity.

Walls, Susan C.; Barichivich, William J.; Brown, Mary E.

2013-01-01

391

Drought, deluge and declines: the impact of precipitation extremes on amphibians in a changing climate.  

PubMed

The Class Amphibia is one of the most severely impacted taxa in an on-going global biodiversity crisis. Because amphibian reproduction is tightly associated with the presence of water, climatic changes that affect water availability pose a particularly menacing threat to both aquatic and terrestrial-breeding amphibians. We explore the impacts that one facet of climate change-that of extreme variation in precipitation-may have on amphibians. This variation is manifested principally as increases in the incidence and severity of both drought and major storm events. We stress the need to consider not only total precipitation amounts but also the pattern and timing of rainfall events. Such rainfall "pulses" are likely to become increasingly more influential on amphibians, especially in relation to seasonal reproduction. Changes in reproductive phenology can strongly influence the outcome of competitive and predatory interactions, thus potentially altering community dynamics in assemblages of co-existing species. We present a conceptual model to illustrate possible landscape and metapopulation consequences of alternative climate change scenarios for pond-breeding amphibians, using the Mole Salamander, Ambystoma talpoideum, as an example. Although amphibians have evolved a variety of life history strategies that enable them to cope with environmental uncertainty, it is unclear whether adaptations can keep pace with the escalating rate of climate change. Climate change, especially in combination with other stressors, is a daunting challenge for the persistence of amphibians and, thus, the conservation of global biodiversity. PMID:24832668

Walls, Susan C; Barichivich, William J; Brown, Mary E

2013-01-01

392

Testing wetland features to increase amphibian reproductive success and species richness for mitigation and restoration.  

PubMed

Aquatic habitat features can directly influence the abundance, species richness, and quality of juvenile amphibians recruited into adult populations. We examined the influences of within-wetland slope, vegetation, and stocked mosquito fish (Gambusia affinis) on amphibian metamorph production and species richness during the first two years post-construction at 18 experimental wetlands in northeast Missouri (U.S.A.) grasslands. We used an information theoretic approach (AICc) to rank regression models representing total amphibian metamorph production, individual amphibian species metamorph production, and larval amphibian species richness. Total amphibian metamorph production was greatest at shallow-sloped, fish-free wetlands during the first year, but shallow-sloped wetlands with high vegetation cover were best the second year. Species richness was negatively associated with fish and positively associated with vegetation in both survey years. Leopard frog (Rana blairi/sphenocephala complex) metamorph quality, based on average metamorph size, was influenced by slope and the number of cohorts in the wetland. However, the tested variables had little influence on the size of American toads (Bufo americanus) or boreal chorus frogs (Pseudacris maculata). Our results indicate that wetlands designed to act as functional reproductive habitat for amphibians should incorporate shallows, high amounts of planted or naturally established vegetation cover, and should be fish-free. PMID:22908722

Shulse, Christopher D; Semlitsch, Raymond D; Trauth, Kathleen M; Gardner, James E

2012-07-01

393

Mine spoil prairies expand critical habitat for endangered and threatened amphibian and reptile species  

USGS Publications Warehouse

Coal extraction has been occurring in the Midwestern United States for over a century. Despite the pre-mining history of the landscape as woodlands, spent surface coalfields are often reclaimed to grasslands. We assessed amphibian and reptile species on a large tract of coal spoil prairie and found 13 species of amphibians (nine frog and four salamander species) and 19 species of reptiles (one lizard, five turtle, and 13 snake species). Two state-endangered and three state species of special concern were documented. The amphibian diversity at our study site was comparable to the diversity found at a large restored prairie situated 175 km north, within the historic prairie peninsula.

Lannoo, Michael J.; Kinney, Vanessa C.; Heemeyer, Jennifer L.; Engbrecht, Nathan J.; Gallant, Alisa L.; Klaver, Robert W.

2009-01-01

394

Environmentally-relevant concentrations of atrazine induce non-monotonic acceleration of developmental rate and increased size at metamorphosis in Rhinella arenarum tadpoles.  

PubMed

Despite of the various studies reporting on the subject, anticipating the impacts of the widely-used herbicide atrazine on anuran tadpoles metamorphosis remains complex as increases or decreases of larval period duration are almost as frequently reported as an absence of effect. The aim of the present study was to examine the effects of environmentally-relevant concentrations of atrazine (0.1, 1, 10, 100, and 1000?g/L) on the timings of metamorphosis and body size at metamorphosis in the common South American toad, Rhinella arenarum (Anura: bufonidae). None of the atrazine concentrations tested significantly altered survival. Low atrazine concentrations in the range of 1-100?g/L were found to accelerate developmental rate in a non-monotonic U-shaped concentration-response relationship. This observed acceleration of the metamorphic process occurred entirely between stages 25 and 39; treated tadpoles proceeding through metamorphosis as control animals beyond this point. Together with proceeding through metamorphosis at a faster rate, tadpoles exposed to atrazine concentrations in the range of 1-100?g/L furthermore transformed into significantly larger metamorphs than controls, the concentration-response curve taking the form of an inverted U in this case. The no observed effect concentration (NOEC) was 0.1?g atrazine/L for both size at metamorphosis and timings of metamorphosis. Tadpoles exposed to 100?g/L 17?-estradiol presented the exact same alterations of developmental rate and body size as those treated with 1, 10 and 100?g/L of atrazine. Elements of the experimental design that facilitated the detection of alterations of metamorphosis at low concentrations of atrazine are discussed, together with the ecological significance of those findings. PMID:23499184

Brodeur, Julie C; Sassone, Alina; Hermida, Gladys N; Codugnello, Nadia

2013-06-01

395

Presence of fibronectin during early embryogenesis in amphibian Pleurodeles waltlii.  

PubMed

The presence of fibronectin (FN) has been investigated during the early development of Pleurodeles waltlii by using indirect immunofluorescence and gel electrophoresis methods. Between the early blastula and late gastrula stages, fluorescent staining was detected on cell surface, especially in cells from the blastocoele roof and the marginal zone. Through gastrulation, extracellular material which was accumulated in the area of the blastopore occurred heavily stained for FN. Sodium metaperiodate-sodium boro[3H]hydride has been used to label the surface carbohydrate residues. Labelled glycoproteins were characterized by sodium dodecyl sulphate and two-dimensional polyacrylamide gel electrophoresis coupled with fluorography. Autoradiograms revealed a 220K cell surface glycoprotein which was co-migrating with monomers of FN. The results suggested that FN may be involved in the early morphogenesis of the amphibian embryo. PMID:6825179

Boucaut, J C; Darribere, T

1983-02-01

396

Increase in liver pigmentation during natural hibernation in some amphibians  

PubMed Central

The amount/distribution of liver melanin in 3 amphibian species (Rana esculenta, Triturus a. apuanus, Triturus carnifex) was studied during 2 periods of the annual cycle (summer activity–winter hibernation) by light and electron microscopy, image analysis and microspectrofluorometry. The increase in liver pigmentation (melanin content) during winter appeared to be correlated with morphological and functional modifications in the hepatocytes, which at this period were characterised by a decrease in metabolic activity. These findings were interpreted according to the functional role (e.g. phagocytosis, cytotoxic substance inactivation) played by the pigment cell component in the general physiology of the heterothermic vertebrate liver and, in particular, in relation to a compensatory engagement of these cells against hepatocellular hypoactivity during the winter period.

BARNI, SERGIO; BERTONE, VITTORIO; CROCE, ANNA CLETA; BOTTIROLI, GIOVANNI; BERNINI, FRANCO; GERZELI, GIUSEPPE

1999-01-01

397

Evidence for a proenkephalin-like precursor in amphibian brain.  

PubMed Central

The mammalian proenkephalin-derived peptides [Leu]enkephalin, [Met]enkephalin, and [Met]enkephalin-Arg6-Phe7 were identified in acid extracts of the brain of Bufo marinus by using reversed-phase HPLC and specific radioimmunoassays. [Met]Enkephalin was the predominant opioid peptide present (270 pmol/g). In contrast, the octapeptide [Met]enkephalin-Arg6-Gly7-Leu8, which is also derived from mammalian proenkephalin, was not detected. The ratio of free [Met]enkephalin to [Met]enkephalin-Arg6-Phe7 was found to be 3.5 to 1, which is similar to that observed in mammalian proenkephalin-containing tissues. Together these data (i) indicate that amphibian brain contains a proenkephalin related to the mammalian precursor and (ii) establish the existence of enkephalins and proenkephalin-derived enkephalin-containing peptides in a submammalian species.

Kilpatrick, D L; Howells, R D; Lahm, H W; Udenfriend, S

1983-01-01

398

Correlates of species richness in the largest Neotropical amphibian radiation  

PubMed Central

Although tropical environments are often considered biodiversity hotspots, it is precisely in such environments where least is known about the factors that drive species richness. Here, we use phylogenetic comparative analyses to study correlates of species richness for the largest Neotropical amphibian radiation: New World direct-developing frogs. Clade-age and species richness were nonsignficantly, negatively correlated, suggesting that clade age alone does not explain among-clade variation in species richness. A combination of ecological and morphological traits explained 65% of the variance in species richness. A more vascularized ventral skin, the ability to colonize high-altitude ranges, encompassing a large variety of vegetation types, correlated significantly with species richness, whereas larger body size was marginally correlated with species richness. Hence, whereas high-altitude ranges play a role in shaping clade diversity in the Neotropics, intrinsic factors, such as skin structures and possibly body size, might ultimately determine which clades are more speciose than others.

Gonzalez-Voyer, A; Padial, J M; Castroviejo-Fisher, S; De La Riva, I; Vila, C

2011-01-01

399

Farm Ponds as Critical Habitats for Native Amphibians: Field Season 2000 Report.  

National Technical Information Service (NTIS)

We studied constructed farm ponds in the Driftless Area Ecoregion of southeastern Minnesota, western Wisconsin, and northeastern Iowa. These ponds represent potentially significant breeding, rearing, and over-wintering habitat for amphibians in a landscap...

2001-01-01

400

Utilization of surface mine ponds in East Tennessee by breeding amphibians. Final report  

SciTech Connect

Breeding amphibians were found in 21 of 24 ponds examined on the Ollis Creek Surface Mine in Campbell County, Tennessee. Twelve species of amphibians were identified in ponds that range from 4.0 to 8.0 in pH. Although ponds with low pH values were used by breeding amphibians, significantly more amphibian species were found in ponds with higher pH values. Findings indicated high biological productivity in the surface mine ponds examined. Aquatic vegetation was present in 20 of the 24 ponds. Aquatic insects and a diverse wildlife fauna utilized the study ponds. Surface mine ponds were found to supply an important habitat component for a variety of wildlife species.

Turner, L.J.; Fowler, D.K.

1981-06-01

401

PROBABILISTIC RISK ASSESSMENT FOR THE EFFECTS OF SOLAR ULTRAVIOLET RADIATION ON AMPHIBIANS  

EPA Science Inventory

Several studies have demonstrated that exposure to solar ultraviolet (UV) radiation can cause elevated mortality and an increased prevalence of eye and limb malformations in developing amphibian larvae. From these observations scientists have hypothesized that recent increases in...

402

ASSESSMENT OF ENVIRONMENTAL STRESSORS POTENTIALLY RESPONSIBLE FOR MALFORMATIONS IN NORTH AMERICAN ANURAN AMPHIBIANS  

EPA Science Inventory

A number of species of anuran amphibians from different regions across North America have recently exhibited an increased occurrence of, predominantly, hind limb malformations. Research concerning factors potentially responsible for these malformations has focused extensively on ...

403

Species List of Alaskan Birds, Mammals, Fish, Amphibians, Reptiles, and Invertebrates. Alaska Region Report Number 82.  

ERIC Educational Resources Information Center

This publication contains a detailed list of the birds, mammals, fish, amphibians, reptiles, and invertebrates found in Alaska. Part I lists the species by geographical regions. Part II lists the species by the ecological regions of the state. (CO)

Taylor, Tamra Faris

404

Farm Ponds as Critical Habitats for Native Amphibians: Field Season 2001 Interim Report.  

National Technical Information Service (NTIS)

We studied constructed farm ponds in the Driftless Area Ecoregion of southeastern Minnesota during 2000 and 2001. These ponds represent potentially significant breeding, rearing, and over-wintering habitat for amphibians in a landscape where natural wetla...

2002-01-01

405

Confronting inconsistencies in the amphibian-chytridiomycosis system: implications for disease management.  

PubMed

Chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), is one of the largest threats to wildlife and is putatively linked to the extirpation of numerous amphibians. Despite over a decade of research on Bd, conflicting results from a number of studies make it difficult to forecast where future epizootics will occur and how to manage this pathogen effectively. Here, we emphasize how resolving these conflicts will advance Bd management and amphibian conservation efforts. We synthesize current knowledge on whether Bd is novel or endemic, whether amphibians exhibit acquired resistance to Bd, the importance of host resistance versus tolerance to Bd, and how biotic (e.g. species richness) and abiotic factors (e.g. climate change) affect Bd abundance. Advances in our knowledge of amphibian-chytrid interactions might inform the management of fungal pathogens in general, which are becoming more common and problematic globally. PMID:24118903

Venesky, Matthew D; Raffel, Thomas R; McMahon, Taegan A; Rohr, Jason R

2014-05-01

406

Parasites of Amphibians and Reptiles from Michigan: A Review of the Literature 1916-2003.  

National Technical Information Service (NTIS)

A summary of the literature on the parasites (protozoans, digenetic trematodes, monogeneans, cestodes, and nematodes) of amphibians and reptiles (herps) in Michigan is presented. It is divided into three sections: (1) a list of the parasite species by tax...

P. M. Muzzall

2005-01-01

407

Fabrication and Feasibility Testing of the Composite Roadwheel for the LVT-7 Amphibian Vehicle. Phase 1.  

National Technical Information Service (NTIS)

A composite roadwheel for the United States Marine Corps LVT-7 Amphibian Vehicle was designed and manufactured by Compositek Engineering Corporation. The composite roadwheel is comprised of glass/epoxy composite insert, produced by wet filament winding fo...

F. Shen

1988-01-01

408

[Nested species subsets of amphibians and reptiles in Thousand Island Lake].  

PubMed

Habitat fragmentation is a main cause for the loss of biological diversity. Combining line-transect methods to survey the amphibians and reptiles on 23 islands on Thousand Island Lake in Zhejiang province, along with survey data on nearby plant species and habitat variables collected by GIS, we used the"BINMATNEST (binary matrix nestedness temperature calculator)" software and the Spearman rank correlation to examine whether amphibians and reptiles followed nested subsets and their influencing factors. The results showed that amphibians and reptiles were significantly nested, and that the island area and habitat type were significantly associated with their nested ranks. Therefore, to effectively protect amphibians and reptiles in the Thousand Islands Lake area we should pay prior attention to islands with larger areas and more habitat types. PMID:23019024

Wang, Xi; Wang, Yan-Ping; Ding, Ping

2012-10-01

409

Amphibians and agrochemicals: Dermal contact and pesticide uptake from irrigated croplands in SW Georgia  

EPA Science Inventory

Background/Question/Methods Although isolated wetlands comprise a significant portion of amphibian breeding habitats throughout the United States, they are not protected under the Clean Water Act. In SW Georgia where agriculture is dominant within the landscape, many isolated ...

410

DISTRIBUTIONAL CHANGES AND POPULATION STATUS FOR AMPHIBIANS IN THE EASTERN MOJAVE DESERT  

EPA Science Inventory

A number of amphibian species historically inhabited sparsely distributed wetlands in the Mojave Desert of western North America, habitats that have been dramatically altered or eliminated as a result of human activities. The population status and distributional changes for amphi...

411

Steroid and Neuronal Regulation of Ecdysone Receptor Expression during Metamorphosis of Muscle in the Moth, Manduca sexta  

Microsoft Academic Search

Ecdysteroids regulate the remodeling of the dorsal external oblique 1 (DEO1) muscle during metamorphosis in Manduca sexta (Hegstrom and Truman, 1996a). We show that the tem- poral and spatial patterning of the A and B1 isoforms of the ecdysone receptor (EcR) within muscle DEO1 corresponds with the developmental fates of the fibers. Using antibodies directed to specific isoforms of EcR,

Carol D. Hegstrom; Lynn M. Riddiford; James W. Truman

1998-01-01

412

Significance of critical developmental stage on starvation induced endocrine mediated precocious metamorphosis in Oryctes rhinoceros (Coleoptera: Scarabaeidae)  

Microsoft Academic Search

Final (3rd) instar larvae of the coconut rhinoceros beetleOryctes rhinoceros were found to undergo precocious metamorphosis when subjected to starvation; the beetles produced as a result were subnormal\\u000a in size. However, the larva showed this kind of response to starvation only after attaining a certain critical stage of development;\\u000a otherwise they died after surviving for a varying period, depending on

A Mini; V K K Prabhu

1986-01-01

413

The POU Factor Ventral Veins Lacking/Drifter Directs the Timing of Metamorphosis through Ecdysteroid and Juvenile Hormone Signaling  

PubMed Central

Although endocrine changes are known to modulate the timing of major developmental transitions, the genetic mechanisms underlying these changes remain poorly understood. In insects, two developmental hormones, juvenile hormone (JH) and ecdysteroids, are coordinated with each other to induce developmental changes associated with metamorphosis. However, the regulation underlying the coordination of JH and ecdysteroid synthesis remains elusive. Here, we examined the function of a homolog of the vertebrate POU domain protein, Ventral veins lacking (Vvl)/Drifter, in regulating both of these hormonal pathways in the red flour beetle, Tribolium castaneum (Tenebrionidae). RNA interference-mediated silencing of vvl expression led to both precocious metamorphosis and inhibition of molting in the larva. Ectopic application of a JH analog on vvl knockdown larvae delayed the onset of metamorphosis and led to a prolonged larval stage, indicating that Vvl acts upstream of JH signaling. Accordingly, vvl knockdown also reduced the expression of a JH biosynthesis gene, JH acid methyltransferase 3 (jhamt3). In addition, ecdysone titer and the expression of the ecdysone response gene, hormone receptor 3 (HR3), were reduced in vvl knockdown larvae. The expression of the ecdysone biosynthesis gene phantom (phm) and spook (spo) were reduced in vvl knockdown larvae in the anterior and posterior halves, respectively, indicating that Vvl might influence ecdysone biosynthesis in both the prothoracic gland and additional endocrine sources. Injection of 20-hydroxyecdysone (20E) into vvl knockdown larvae could restore the expression of HR3 although molting was never restored. These findings suggest that Vvl coordinates both JH and ecdysteroid biosynthesis as well as molting behavior to influence molting and the timing of metamorphosis. Thus, in both vertebrates and insects, POU factors modulate the production of major neuroendocrine regulators during sexual maturation.

Chaieb, Leila; Koyama, Takashi; Sarwar, Prioty; Mirth, Christen K.; Smith, Wendy A.; Suzuki, Yuichiro

2014-01-01

414

X-irradiation effects on growth and metamorphosis of gastropod larvae ( Crepidula fornicata ): A model for environmental radiation teratogenesis  

Microsoft Academic Search

Little information is available on the effects of x-irradiation on the development of multicellular marine organisms. Larvae of the marine gastropodCrepidula fornicata were irradiated at 200 rad\\/min, 250 kVp x-rays, to doses between 500 and 20,000 rad in a single fraction. During the weeks following exposure, changes in shell length and biomass, incidence of metamorphosis to the juvenile stage of

Joel S. Greenberger; Jan Pechenik; Acha Lord; Lisa Gould; Elizabeth Naparstek; Kenneth Kase; T. J. FitzGerald

1986-01-01

415

The POU Factor Ventral Veins Lacking/Drifter Directs the Timing of Metamorphosis through Ecdysteroid and Juvenile Hormone Signaling.  

PubMed

Although endocrine changes are known to modulate the timing of major developmental transitions, the genetic mechanisms underlying these changes remain poorly understood. In insects, two developmental hormones, juvenile hormone (JH) and ecdysteroids, are coordinated with each other to induce developmental changes associated with metamorphosis. However, the regulation underlying the coordination of JH and ecdysteroid synthesis remains elusive. Here, we examined the function of a homolog of the vertebrate POU domain protein, Ventral veins lacking (Vvl)/Drifter, in regulating both of these hormonal pathways in the red flour beetle, Tribolium castaneum (Tenebrionidae). RNA interference-mediated silencing of vvl expression led to both precocious metamorphosis and inhibition of molting in the larva. Ectopic application of a JH analog on vvl knockdown larvae delayed the onset of metamorphosis and led to a prolonged larval stage, indicating that Vvl acts upstream of JH signaling. Accordingly, vvl knockdown also reduced the expression of a JH biosynthesis gene, JH acid methyltransferase 3 (jhamt3). In addition, ecdysone titer and the expression of the ecdysone response gene, hormone receptor 3 (HR3), were reduced in vvl knockdown larvae. The expression of the ecdysone biosynthesis gene phantom (phm) and spook (spo) were reduced in vvl knockdown larvae in the anterior and posterior halves, respectively, indicating that Vvl might influence ecdysone biosynthesis in both the prothoracic gland and additional endocrine sources. Injection of 20-hydroxyecdysone (20E) into vvl knockdown larvae could restore the expression of HR3 although molting was never restored. These findings suggest that Vvl coordinates both JH and ecdysteroid biosynthesis as well as molting behavior to influence molting and the timing of metamorphosis. Thus, in both vertebrates and insects, POU factors modulate the production of major neuroendocrine regulators during sexual maturation. PMID:24945490

Cheng, CeCe; Ko, Amy; Chaieb, Leila; Koyama, Takashi; Sarwar, Prioty; Mirth, Christen K; Smith, Wendy A; Suzuki, Yuichiro

2014-06-01

416

Reptiles as potential vectors and hosts of the amphibian pathogen Batrachochytrium dendrobatidis in Panama.  

PubMed

Chytridiomycosis, the disease caused by Batrachochytrium dendrobatidis, is considered to be a disease exclusively of amphibians. However, B. dendrobatidis may also be capable of persisting in the environment, and non-amphibian vectors or hosts may contribute to disease transmission. Reptiles living in close proximity to amphibians and sharing similar ecological traits could serve as vectors or reservoir hosts for B. dendrobatidis, harbouring the organism on their skin without succumbing to disease. We surveyed for the presence of B. dendrobatidis DNA among 211 lizards and 8 snakes at 8 sites at varying elevations in Panama where the syntopic amphibians were at pre-epizootic, epizootic or post-epizootic stages of chytridiomycosis. Detection of B. dendrobatidis DNA was done using qPCR analysis. Evidence of the amphibian pathogen was present at varying intensities in 29 of 79 examined Anolis humilis lizards (32%) and 9 of 101 A. lionotus lizards (9%), and in one individual each of the snakes Pliocercus euryzonus, Imantodes cenchoa, and Nothopsis rugosus. In general, B. dendrobatidis DNA prevalence among reptiles was positively correlated with the infection prevalence among co-occurring anuran amphibians at any particular site (r = 0.88, p = 0.004). These reptiles, therefore, may likely be vectors or reservoir hosts for B. dendrobatidis and could serve as disease transmission agents. Although there is no evidence of B. dendrobatidis disease-induced declines in reptiles, cases of coincidence of reptile and amphibian declines suggest this potentiality. Our study is the first to provide evidence of non-amphibian carriers for B. dendrobatidis in a natural Neotropical environment. PMID:22303629

Kilburn, Vanessa L; Ibáñez, Roberto; Green, David M

2011-12-01

417

Chytridiomycosis and Amphibian Population Declines Continue to Spread Eastward in Panama  

Microsoft Academic Search

Chytridiomycosis is a globally emerging disease of amphibians and the leading cause of population declines and extirpations\\u000a at species-diverse montane sites in Central America. We continued long-term monitoring efforts for the presence of the fungal\\u000a pathogen Batrachochytrium dendrobatidis (Bd) and for amphibian populations at two sites in western Panama, and we began monitoring at three new sites to the east.

Douglas C. Woodhams; Vanessa L. Kilburn; Laura K. Reinert; Jamie Voyles; Daniel Medina; Roberto Ibáñez; Alex D. Hyatt; Donna G. Boyle; James D. Pask; David M. Green; Louise A. Rollins-Smith

2008-01-01

418

Uptake and Effects on Detoxication Enzymes of Cypermethrin in Embryos and Tadpoles of Amphibians  

Microsoft Academic Search

A number of factors have been suggested for recently observed amphibian decreases, and one potential factor is pesticide exposure. We studied the uptake and effects of environmentally relevant concentrations of the pyrethroid insecticide cypermethrin on two different amphibian species, Bombina variegata and Rana arvalis. The uptake from water of 14C-labeled cypermethrin (0.4 ?g\\/L) by eggs and tadpoles of B. variegata

K. Greulich; S. Pflugmacher

2004-01-01

419

Biodiversity of trematodes associated with amphibians from a variety of habitats in Corrientes Province, Argentina.  

PubMed

The main goals of this study were to compare the richness of parasitic trematodes in amphibians with diverse habits (terrestrial, fossorial, semi-aquatic and arboreal), and to evaluate whether the composition of the trematode community is determined by ecological relationships. Specimens were collected between April 2001 and December 2006 from a common area (30 ha) in Corrientes Province, Argentina. Trematodes of amphibians in this area comprised a total of 19 species, and were dominated by common species. Larval trematodes presented highest species richness, with the metacercaria of Bursotrema tetracotyloides being dominant in the majority (7/9, 78%) of the parasite communities. Adults of the trematode Catadiscus inopinatus were dominant in the majority (6/9, 67%) of amphibians. The amphibians Leptodactylus latinasus, Leptodactylus bufonius and Scinax nasicus presented a high diversity of trematodes, whereas Leptodactylus chaquensis had the lowest diversity even though it presented with the highest species richness. The patterns of similarity among amphibian species showed groups linking with their habitats. Leptodactilid amphibians, with a generalist diet and an active foraging strategy showed highest infection rates with adult trematodes. The mean richness of trematode species related to host's habitat preferences was higher in semi-aquatic amphibians. Results suggest that semi-aquatic amphibians, present in both aquatic and terrestrial environments, present a greater diversity of parasites as they have a higher rate of exposure to a wider range of prey species and, hence, to diverse infective states. The trematode composition is related to the diets and mobility of the host, and habitat. PMID:22874101

Hamann, M I; Kehr, A I; González, C E

2013-09-01

420

Synergism between UV-B radiation and pathogen magnifies amphibian embryo mortality in nature  

Microsoft Academic Search

Previous research has shown that amphibians have differential sensitivity to ultraviolet-B (UV-B) radiation. In some species, ambient levels of UV-B radiation cause embryonic mortality in nature. The detrimental effects of UV-B alone or with other agents may ultimately affect amphibians at the population level. Here, we experimentally demonstrate a synergistic effect between UV-B radiation and a pathogenic fungus in the

J. M. Kiesecker; R. Blaustein

1995-01-01

421

Influence of forest management on headwater stream amphibians at multiple spatial scales  

USGS Publications Warehouse

Background Amphibians are important components of headwater streams in forest ecosystems of the Pacific Northwest (PNW). They comprise the highest vertebrate biomass and density in these systems and are integral to trophic dynamics both as prey and as predators. The most commonly encountered amphibians in PNW headwater streams include the Pacific giant salamander (Dicamptodon tenebrosus), the tailed frog (Ascaphus truei), the southern torrent salamander (Rhyacotriton variegatus), and the Columbia torrent salamander (R. kezeri).

Stoddard, Margo; Hayes, John P.; Erickson, Janet L.

2004-01-01

422

Evaluation of seven aquatic sampling methods for amphibians and other aquatic fauna  

USGS Publications Warehouse

To design effective and efficient research and monitoring programs researchers must have a thorough understanding of the capabilities and limitations of their sampling methods. Few direct comparative studies exist for aquatic sampling methods for amphibians. The objective of this study was to simultaneously employ seven aquatic sampling methods in 10 wetlands to compare amphibian species richness and number of individuals detected with each method. Four sampling methods allowed counts of individuals (metal dipnet, D-frame dipnet, box trap, crayfish trap), whereas the other three methods allowed detection of species (visual encounter, aural, and froglogger). Amphibian species richness was greatest with froglogger, box trap, and aural samples. For anuran species, the sampling methods by which each life stage was detected was related to relative length of larval and breeding periods and tadpole size. Detection probability of amphibians varied across sampling methods. Box trap sampling resulted in the most precise amphibian count, but the precision of all four count-based methods was low (coefficient of variation > 145 for all methods). The efficacy of the four count sampling methods at sampling fish and aquatic invertebrates was also analyzed because these predatory taxa are known to be important predictors of amphibian habitat distribution. Species richness and counts were similar for fish with the four methods, whereas invertebrate species richness and counts were greatest in box traps. An effective wetland amphibian monitoring program in the southeastern United States should include multiple sampling methods to obtain the most accurate assessment of species community composition at each site. The combined use of frogloggers, crayfish traps, and dipnets may be the most efficient and effective amphibian monitoring protocol. ?? 2007 Brill Academic Publishers.

Gunzburger, M. S.

2007-01-01

423

Analysis of nitric oxide-cyclic guanosine monophosphate signaling during metamorphosis of the nudibranch Phestilla sibogae Bergh (Gastropoda: Opisthobranchia)  

PubMed Central

SUMMARY The gas nitric oxide (NO), and in some cases its downstream second messenger, cyclic guanosine monophosphate (cGMP) function in different taxa to regulate the timing of life-history transitions. Increased taxonomic sampling is required to foster conclusions about the evolution and function of NO/cGMP signaling during life-history transitions. We report on the function and localization of NO and cGMP signaling during metamorphosis of the nudibranch Phestilla sibogae. Pharmacological manipulation of NO or cGMP production in larvae modulated responses to a natural settlement cue from the coral Porites compressa in a manner that suggest inhibitory function for NO/cGMP signaling. However, these treatments were not sufficient to induce metamorphosis in the absence of cue, a result unique to this animal. We show that induction of metamorphosis in response to the settlement cue is associated with a reduction in NO production. We documented the expression of putative NO synthase (NOS) and the production of cGMP during larval development and observed no larval cells in which NOS and cGMP were both detected. The production of cGMP in a bilaterally symmetrical group of cells fated to occupy the distal tip of rhinophores is correlated with competence to respond to the coral settlement cue. These results suggest that endogenous NO and cGMP are involved in modulating responses of P. sibogae to a natural settlement cue. We discuss these results with respect to habitat selection and larval ecology.

Bishop, Cory D.; Pires, Anthony; Norby, Shong-Wan; Boudko, Dmitri; Moroz, Leonid L.; Hadfield, Michael G.

2014-01-01

424

Morphology and metamorphosis of the peptidergic Va neurons and the median nerve system of the fruit fly, Drosophila melanogaster.  

PubMed

Metamorphosis is a fundamental developmental process and has been intensively studied for various neuron types of Drosophila melanogaster. However, detailed accounts of the fate of identified peptidergic neurons are rare. We have performed a detailed study of the larval morphology and pupal remodelling of identified peptidergic neurons, the CAPA-expressing Va neurons of D. melanogaster. In the larva, Va neurons innervate abdominal median and transverse nerves that are typically associated with perisympathetic organs (PSOs), major neurohaemal release sites in insects. Since median and transverse nerves are lacking in the adult, Va neurites have to undergo substantial remodelling during metamorphosis. We have examined the hitherto uncharacterised gross morphology of the thoracic PSOs and the abdominal median and transverse nerves by scanning electron microscopy and found that the complete reduction of these structures during metamorphosis starts around pupal stage P7 and is completed at P9. Concomitantly, neurite pruning of the Va neurons begins at P6 and is preceded by the high expression of the ecdysone receptor (EcR) subtype B1 in late L3 larvae and the first pupal stages. New neuritic outgrowth mainly occurs from P7-P9 and coincides with the expression of EcR-A, indicating that the remodelling of the Va neurons is under ecdysteroid control. Immunogold-labelling has located the CAPA peptides to large translucent vesicles, which are released from the transverse nerves, as suggested by fusion profiles. Hence, the transverse nerves may serve a neurohaemal function in D. melanogaster. PMID:16685531

Santos, Jonathan G; Pollák, Edit; Rexer, Karl-Heinz; Molnár, László; Wegener, Christian

2006-10-01

425

Evolution of metamorphosis: role of environment on expression of mutant nuclear receptors and other signal-transduction proteins.  

PubMed

Various lipophilic signals, including ecdysone, retinoic acid, estradiol, cortisol, testosterone, and progesterone, act through nuclear receptors, a large group of transcription factors that regulate differentiation and development, which are central to metamorphosis. Here, we focus on environmental factors (for example climate and chemicals) in the evolution of nuclear receptors and other signal-transduction proteins that interact with heat-shock protein 90 (Hsp90), a chaperone that promotes the proper folding and trafficking in cells of proteins. Hsp90 also promotes functional folding of some mutant signal proteins, which would be otherwise destabilized. Stress diverts Hsp90 from stabilizing mutant signal-transduction proteins and toward promoting proper folding of stress-damaged proteins and preventing the aggregation of denatured proteins. Reduced Hsp90 levels allow expression of cryptic mutations in signal-transduction proteins and new developmental patterns. Thus, environmental stress in the form of extreme climate can influence the evolution of metamorphosis. We discuss how extreme cooling called "Snowball Earth," which occurred in the late Proterozoic, diverted Hsp90 from chaperoning signal-transduction proteins. As a result, pre-existing mutant signal-transduction proteins were expressed in animals. Some mutations were selectively advantageous in animals that are seen in the Cambrian, when diverse pathways for metamorphosis in metazoans first appear in the fossil record. Other environmental factors, such as biological chemicals (for example the antibiotic geldanamycin) can reduce the levels of active Hsp90 providing another mechanism for the emergence of mutant signaling pathways. PMID:21672786

Baker, Michael E

2006-12-01

426

Detection probabilities and site occupancy estimates for amphibians at Okefenokee National Wildlife Refuge  

USGS Publications Warehouse

We conducted an amphibian inventory at Okefenokee National Wildlife Refuge from August 2000 to June 2002 as part of the U.S. Department of the Interior's national Amphibian Research and Monitoring Initiative. Nineteen species of amphibians (15 anurans and 4 caudates) were documented within the Refuge, including one protected species, the Gopher Frog Rana capito. We also collected 1 y of monitoring data for amphibian populations and incorporated the results into the inventory. Detection probabilities and site occupancy estimates for four species, the Pinewoods Treefrog (Hyla femoralis), Pig Frog (Rana grylio), Southern Leopard Frog (R. sphenocephala) and Carpenter Frog (R. virgatipes) are presented here. Detection probabilities observed in this study indicate that spring and summer surveys offer the best opportunity to detect these species in the Refuge. Results of the inventory suggest that substantial changes may have occurred in the amphibian fauna within and adjacent to the swamp. However, monitoring the amphibian community of Okefenokee Swamp will prove difficult because of the logistical challenges associated with a rigorous statistical assessment of status and trends.

Smith, L. L.; Barichivich, W. J.; Staiger, J. S.; Smith, K. G.; Dodd, Jr. , C. K.

2006-01-01

427

Vast underestimation of Madagascar's biodiversity evidenced by an integrative amphibian inventory  

PubMed Central

Amphibians are in decline worldwide. However, their patterns of diversity, especially in the tropics, are not well understood, mainly because of incomplete information on taxonomy and distribution. We assess morphological, bioacoustic, and genetic variation of Madagascar's amphibians, one of the first near-complete taxon samplings from a biodiversity hotspot. Based on DNA sequences of 2,850 specimens sampled from over 170 localities, our analyses reveal an extreme proportion of amphibian diversity, projecting an almost 2-fold increase in species numbers from the currently described 244 species to a minimum of 373 and up to 465. This diversity is widespread geographically and across most major phylogenetic lineages except in a few previously well-studied genera, and is not restricted to morphologically cryptic clades. We classify the genealogical lineages in confirmed and unconfirmed candidate species or deeply divergent conspecific lineages based on concordance of genetic divergences with other characters. This integrative approach may be widely applicable to improve estimates of organismal diversity. Our results suggest that in Madagascar the spatial pattern of amphibian richness and endemism must be revisited, and current habitat destruction may be affecting more species than previously thought, in amphibians as well as in other animal groups. This case study suggests that worldwide tropical amphibian diversity is probably underestimated at an unprecedented level and stresses the need for integrated taxonomic surveys as a basis for prioritizing conservation efforts within biodiversity hotspots.

Vieites, David R.; Wollenberg, Katharina C.; Andreone, Franco; Kohler, Jorn; Glaw, Frank; Vences, Miguel

2009-01-01

428

Amphibians acquire resistance to live and dead fungus overcoming fungal immunosuppression.  

PubMed

Emerging fungal pathogens pose a greater threat to biodiversity than any other parasitic group, causing declines of many taxa, including bats, corals, bees, snakes and amphibians. Currently, there is little evidence that wild animals can acquire resistance to these pathogens. Batrachochytrium dendrobatidis is a pathogenic fungus implicated in the recent global decline of amphibians. Here we demonstrate that three species of amphibians can acquire behavioural or immunological resistance to B. dendrobatidis. Frogs learned to avoid the fungus after just one B. dendrobatidis exposure and temperature-induced clearance. In subsequent experiments in which B. dendrobatidis avoidance was prevented, the number of previous exposures was a negative predictor of B. dendrobatidis burden on frogs and B. dendrobatidis-induced mortality, and was a positive predictor of lymphocyte abundance and proliferation. These results suggest that amphibians can acquire immunity to B. dendrobatidis that overcomes pathogen-induced immunosuppression and increases their survival. Importantly, exposure to dead fungus induced a similar magnitude of acquired resistance as exposure to live fungus. Exposure of frogs to B. dendrobatidis antigens might offer a practical way to protect pathogen-naive amphibians and facilitate the reintroduction of amphibians to locations in the wild where B. dendrobatidis persists. Moreover, given the conserved nature of vertebrate immune responses to fungi and the fact that many animals are capable of learning to avoid natural enemies, these results offer hope that other wild animal taxa threatened by invasive fungi might be rescued by management approaches based on herd immunity. PMID:25008531

McMahon, Taegan A; Sears, Brittany F; Venesky, Matthew D; Bessler, Scott M; Brown, Jenise M; Deutsch, Kaitlin; Halstead, Neal T; Lentz, Garrett; Tenouri, Nadia; Young, Suzanne; Civitello, David J; Ortega, Nicole; Fites, J Scott; Reinert, Laura K; Rollins-Smith, Louise A; Raffel, Thomas R; Rohr, Jason R

2014-07-10

429

Infectious disease and worldwide declines of amphibian populations, with comments on emerging diseases in coral reef organisms and in humans.  

PubMed Central

Many populations of amphibians are declining on all six continents on which they occur. Some causes of amphibian declines, such as habitat destruction, direct application of xenobiotics, and introduction of predators or competitors, are clearly attributable to human activities. Infectious disease appears to be the direct cause of mass amphibian die-offs in relatively undisturbed areas of the world where anthropomorphic environmental disruption is minimal. In these cases, it is not yet clear whether these epizootics result from the natural evolution of new pathogens or from environmental changes that promote the emergence of pathogenic forms and/or that weaken the immune defenses of amphibians. Because some aspects of pathogen-related amphibian mass mortalities are similar to outbreaks of new diseases in humans and coral reef organisms, amphibian declines may be part of a much larger pattern than previously appreciated.

Carey, C

2000-01-01

430

Effects of cadmium, estradiol-17?? and their interaction on gonadal condition and metamorphosis of male and female African clawed frog, Xenopus laevis  

USGS Publications Warehouse

To assess interaction effects between cadmium (Cd, a putative xenoestrogen) and estradiol-17?? (E2) on sex differentiation and metamorphosis, Xenopus laevis were exposed to solvent-control (0.005% ethanol), Cd (10 ??g L-1), E2 (1 ??g L-1), or Cd and E2 (Cd + E2) in FETAX medium from fertilization to 75 d postfertilization. Each treatment was applied to four aquaria, each with 30 fertilized eggs. Mortality was recorded and animals were sampled as they completed metamorphosis (Nieuwkoop and Faber stage 66). Gonadal sex of individuals (including tadpoles ???NF stage 55 at day 75) was determined gross-morphologically and used to compute sex ratios. Time course and percent completion of metamorphosis, snout-vent length (SVL), hindlimb length (HLL) and weight were analyzed for each gender separately. Survival rates did not differ among treatments. The E2 and Cd + E2 treatments significantly skewed sex ratios towards females; however, no sex-ratio differences were observed between the control and Cd treatments or between the E2 and Cd + E2 treatments. Time course of metamorphosis was generally delayed and percent completion of metamorphosis was generally reduced in males and females exposed to Cd, E2 or their combination compared to control animals. In males, but not females, the effect of Cd + E2 was greater than that of individual chemicals. Weight at completion of metamorphosis was reduced only in females and only by the Cd + E2 treatment. In conclusion, although Cd at an environmentally relevant concentration did not exhibit direct or indirect feminizing effects in Xenopus tadpoles, the metal and E2 both had similar inhibitory effects on metamorphosis that were of greater magnitude in males than females.

Sharma, B.; Patino, R.

2010-01-01

431

Effects of environmental change on helminth infections in amphibians: exploring the emergence of Ribeiroia and Echinostoma infections in North America  

Microsoft Academic Search

\\u000a Amphibians have long served as model organisms for studying animal physiology, vertebrate anatomy, and host–parasite interactions.\\u000a Recently, however, the occurrence of precipitous declines in many amphibian populations and of severe limb malformations in\\u000a others has catalyzed renewed efforts to understand the effects of parasites on amphibians. In this brief review, we examine\\u000a the importance of two groups of trematodes that

Valerie J. McKenzie

432

Effects of the herbicide atrazine on Ambystoma tigrinum metamorphosis: duration, larval growth, and hormonal response  

USGS Publications Warehouse

We exposed larval tiger salamanders (Ambystoma tigrinum) reared in the laboratory from eggs collected from a prairie wetland in North Dakota to three concentrations of atrazine (0, 75, and 250 i??g/L) in a static renewal test to determine the pesticide's effect on (1) plasma corticosterone and thyroxine concentrations, (2) larval size, and (3) days-to-stage at stages 2 and 4 of metamorphic climax. We found significant effects of atrazine on each of these response variables. Plasma thyroxine was elevated in both atrazine-exposed groups compared to the control group; plasma corticosterone was depressed in the 75 i??g/L treatment compared with both the control and 250 i??g/L treatment. Larvae exposed to 75 i??g/L atrazine reached stage 4 later, but at a size and weight comparable to the control group. By contrast, larvae in the 250 i??g/L treatment progressed to stage 4 at the same time but at a smaller size and lower weight than larvae in the control group. These results indicate that the herbicide has the potential to influence tiger salamander life history. We present a model consistent with our results, whereby corticosterone and thyroxine interact to regulate metamorphosis of tiger salamanders based on nutrient assimilation and adult fitness

Larson, D. L.; McDonald, S.; Fivizanni, A. J.; Newton, W. E.; Hamilton, S. J.

1998-01-01

433

Bisubstrate specificity in histidine/tryptophan biosynthesis isomerase from Mycobacterium tuberculosis by active site metamorphosis  

PubMed Central

In histidine and tryptophan biosynthesis, two related isomerization reactions are generally catalyzed by two specific single-substrate enzymes (HisA and TrpF), sharing a similar (?/?)8-barrel scaffold. However, in some actinobacteria, one of the two encoding genes (trpF) is missing and the two reactions are instead catalyzed by one bisubstrate enzyme (PriA). To unravel the unknown mechanism of bisubstrate specificity, we used the Mycobacterium tuberculosis PriA enzyme as a model. Comparative structural analysis of the active site of the enzyme showed that PriA undergoes a reaction-specific and substrate-induced metamorphosis of the active site architecture, demonstrating its unique ability to essentially form two different substrate-specific actives sites. Furthermore, we found that one of the two catalytic residues in PriA, which are identical in both isomerization reactions, is recruited by a substrate-dependent mechanism into the active site to allow its involvement in catalysis. Comparison of the structural data from PriA with one of the two single-substrate enzymes (TrpF) revealed substantial differences in the active site architecture, suggesting independent evolution. To support these observations, we identified six small molecule compounds that inhibited both PriA-catalyzed isomerization reactions but had no effect on TrpF activity. Our data demonstrate an opportunity for organism-specific inhibition of enzymatic catalysis by taking advantage of the distinct ability for bisubstrate catalysis in the M. tuberculosis enzyme.

Due, Anne V.; Kuper, Jochen; Geerlof, Arie; von Kries, Jens Peter; Wilmanns, Matthias

2011-01-01

434

Proliferation and differentiation of intestinal stem cells during metamorphosis of the red flour beetle, Tribolium castaneum.  

PubMed

The insect midgut epithelium is remodeled during larval-pupal metamorphosis when larval polyploid cells (LPCs) are replaced by the daughters of intestinal stem cells (ISCs). We characterized the proliferation of ISCs during midgut remodeling in the red flour beetle, Tribolium castaneum. Midgut remodeling is initiated at 96 hr after ecdysis into the final instar larval stage. Immunocytochemistry with bromodeoxyuridine and phospho-histone H3 antibodies showed that the ISCs are the progenitors of the pupal/adult midgut epithelium and they undergo proliferation and differentiation to form new midgut epithelium. In vitro midgut culture experiments revealed that 20-hydroxyecdysone (20E) in the absence of juvenile hormone induces proliferation of ISCs. RNA interference (RNAi) mediated silencing of ecdysone receptors (EcRA and EcRB) and ultraspiracle (USP) identified EcRA and USP but not EcRB as the proteins involved in 20E regulation of ISCs proliferation. These data show that the proliferation of ISCs is under both developmental and endocrine regulation. PMID:18297733

Parthasarathy, R; Palli, Subba R

2008-04-01

435