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1

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. PMID:22481853

Miyata, Kaori; Ose, Keiko

2012-01-01

2

Triclosan exposure alters postembryonic development in a Pacific tree frog (Pseudacris regilla) Amphibian Metamorphosis Assay (TREEMA).  

PubMed

The Amphibian Metamorphosis Assay (AMA), developed for Xenopus laevis, is designed to identify chemicals that disrupt thyroid hormone (TH)-mediated biological processes. We adapted the AMA for use on an ecologically-relevant North American species, the Pacific tree frog (Pseudacris regilla), and applied molecular endpoints to evaluate the effects of the antibacterial agent, triclosan (TCS). Premetamorphic (Gosner stage 26-28) tadpoles were immersed for 21 days in solvent control, 1.5 ?g/L thyroxine (T(4)), 0.3, 3 and 30 ?g/L (nominal) TCS, or combined T(4)/TCS treatments. Exposure effects were scored by morphometric (developmental stage, wet weight, and body, snout-vent and hindlimb lengths) and molecular (mRNA abundance using quantitative real time polymerase chain reaction) criteria. T(4) treatment alone accelerated development concomitant with altered levels of TH receptors ? and ?, proliferating cell nuclear antigen, and gelatinase B mRNAs in the brain and tail. We observed TCS-induced perturbations in all of the molecular and morphological endpoints indicating that TCS exposure disrupts coordination of postembryonic tadpole development. Clear alterations in molecular endpoints were evident at day 2 whereas the earliest morphological effects appeared at day 4 and were most evident at day 21. Although TCS alone (3 and 30 ?g/L) was protective against tadpole mortality, this protection was lost in the presence of T(4). The Pacific tree frog is the most sensitive species examined to date displaying disruption of TH-mediated development by a common antimicrobial agent. PMID:23159728

Marlatt, Vicki L; Veldhoen, Nik; Lo, Bonnie P; Bakker, Dannika; Rehaume, Vicki; Vallée, Kurtis; Haberl, Maxine; Shang, Dayue; van Aggelen, Graham C; Skirrow, Rachel C; Elphick, James R; Helbing, Caren C

2013-01-15

3

Examination of an amphibian metamorphosis assay under an individual-separated exposure system using Silurana tropicalis tadpoles.  

PubMed

We examined the validity of an amphibian (Silurana tropicalis) metamorphosis assay (a 28-day semistatic test) under an individual-separated exposure system, where tadpoles were individually held in small glass beakers. We first conducted a comparative rearing experiment for 28 days between this exposure system and the traditional individual-grouped exposure system, both of which held 30 tadpoles (stages 49 and 50) in dechlorinated tap water (a control solution). The former system served to reduce interindividual variability in regard to three morphological measures (developmental stage, hind limb length, and total body length). Under this system, we tested thyroxine (T4, 1?g/L) and propylthiouracil (PTU, 75mg/L) for 28 days of exposure. The morphological data collected at 7-day intervals indicated that significant metamorphic acceleration and retardation were consistently induced in the tadpoles exposed to T4 and PTU, respectively. In addition, the thyroid glands of the tadpoles exposed to T4 and PTU clearly exhibited atrophy and hypertrophy accompanied with severe follicular cell hyperplasia, respectively. Our results are in agreement with the historical data generated from previous studies employing the traditional exposure system, thus indicating the validity of our alternative testing protocol. PMID:23067544

Saka, Masahiro; Tada, Noriko; Kamata, Yoichi

2012-12-01

4

The Metamorphosis of Amphibian Toxicogenomics  

PubMed Central

Amphibians are important vertebrates in toxicology often representing both aquatic and terrestrial forms within the life history of the same species. Of the thousands of species, only two have substantial genomics resources: the recently published genome of the Pipid, Xenopus (Silurana) tropicalis, and transcript information (and ongoing genome sequencing project) of Xenopus laevis. However, many more species representative of regional ecological niches and life strategies are used in toxicology worldwide. Since Xenopus species diverged from the most populous frog family, the Ranidae, ~200 million years ago, there are notable differences between them and the even more distant Caudates (salamanders) and Caecilians. These differences include genome size, gene composition, and extent of polyploidization. Application of toxicogenomics to amphibians requires the mobilization of resources and expertise to develop de novo sequence assemblies and analysis strategies for a broader range of amphibian species. The present mini-review will present the advances in toxicogenomics as pertains to amphibians with particular emphasis upon the development and use of genomic techniques (inclusive of transcriptomics, proteomics, and metabolomics) and the challenges inherent therein. PMID:22435070

Helbing, Caren C.

2012-01-01

5

Effects of freshwater petroleum contamination on amphibian hatching and metamorphosis  

SciTech Connect

This study examined the effects of freshwater petroleum contamination on amphibian reproduction. The primary objectives were to assess the potential environmental and physiological impacts of runoff petroleum products on amphibians, using the green tree frog (Hyla cinerea) as a target species and engine crankcase oil as a contaminant. Egg hatching success, tadpole growth, and successful metamorphosis were measured in four concentrations of oil. The effects of oil on food source was also studied. Hatching success was not measurably influenced by the presence of oil. Tadpole and alga growth were negatively associated with the presence of oil. No tadpoles from the high concentration of oil treatments successfully metamorphosed.

Mahaney, P.A. (Univ. of Georgia, Aiken, SC (United States). Dept. of Zoology)

1994-02-01

6

Amphibian metamorphosis has been used as a model system for investigating the performance consequences of rapid  

E-print Network

Amphibian metamorphosis has been used as a model system for investigating the performance a significant effect on undulatory locomotion, these changes are independent of metamorphosis (Babcock and Blais, 1973) or metamorphosis (Worthington, 1971; Babcock and Blais, 2001). In this study, we will focus

Brainerd, Elizabeth

7

Visual implant elastomer mark retention through metamorphosis in amphibian larvae  

USGS Publications Warehouse

Questions in population ecology require the study of marked animals, and marks are assumed to be permanent and not overlooked by observers. I evaluated retention through metamorphosis of visual implant elastomer marks in larval salamanders and frogs and assessed error in observer identification of these marks. I found 1) individual marks were not retained in larval wood frogs (Rana sylvatica), whereas only small marks were likely to be retained in larval salamanders (Eurycea bislineata), and 2) observers did not always correctly identify marked animals. Evaluating the assumptions of marking protocols is important in the design phase of a study so that correct inference can be made about the population processes of interest. This guidance should be generally useful to the design of mark-recapture studies, with particular application to studies of larval amphibians.

Grant, E. H. C.

2008-01-01

8

Visual implant elastomer mark retention through metamorphosis in amphibian larvae  

USGS Publications Warehouse

Questions in population ecology require the study of marked animals, and marks are assumed to be permanent and not overlooked by observers. I evaluated retention through metamorphosis of visual implant elastomer marks in larval salamanders and frogs and assessed error in observer identification of these marks. I found 1) individual marks were not retained in larval wood frogs (Rana sylvatica), whereas only small marks were likely to be retained in larval salamanders (Eurycea bislineata), and 2) observers did not always correctly identify marked animals. Evaluating the assumptions of marking protocols is important in the design phase of a study so that correct inference can be made about the population processes of interest. This guidance should be generally useful to the design of mark?recapture studies, with particular application to studies of larval amphibians.

Grant, E.H.C.

2008-01-01

9

Restructuring of the amphibian gut microbiota through metamorphosis.  

PubMed

Vertebrates maintain complex symbioses with a diverse community of microbes residing within their guts. The microbial players in these symbioses differ between major taxa of vertebrates, such that fish and amniotes maintain notably different communities. To date, there has not been a culture-independent inventory of an amphibian gut microbial community. Here, we compared gut microbial communities of tadpoles and frogs of the Northern leopard frog (Lithobates pipiens). We utilized Illumina sequencing, which allowed us to inventory more than 450?000 microbial sequences. We found that tadpoles and frogs differ markedly in the composition of their gut microbial communities, with tadpoles maintaining a community more similar to fish, whereas the frog community resembles that of amniotes. Additionally, frogs maintain a community with lower phylogenetic diversity compared with tadpoles. The significant restructuring of the microbiota is likely due to changes in diet as well as the large reorganization of the intestinal organ during metamorphosis. Overall, we propose that amphibians represent an important system in which to study regulation and selection of gut microbial communities. PMID:24249298

Kohl, Kevin D; Cary, Tawnya L; Karasov, William H; Dearing, M Denise

2013-12-01

10

The analysis of complex developmental programmes: amphibian metamorphosis  

Microsoft Academic Search

Metamorphosis in frogs and toads is a set of complex developmental programmes controlled by thyroid hormone (TH). The pervasive and dramatic changes that occur as a tadpole turns into a frog have captured the attention of life scientists from many disciplines. For evolutionary biologists, the extent to which related organisms incorporate metamorphosis in their life cycle is of paramount interest.

Akira Kanamoria; Donald D. Brown

1996-01-01

11

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....

12

Tissue-dependent induction of apoptosis by matrix metalloproteinase stromelysin-3 during amphibian metamorphosis.  

PubMed

Matrix metalloproteinases (MMPs) are a superfamily of Zn(2+)-dependent proteases that are capable of cleaving the proteinaceous component of the extracellular matrix (ECM). The ECM is a critical medium for cell-cell interactions and can also directly signal cells through cell surface ECM receptors, such as integrins. In addition, many growth factors and signaling molecules are stored in the ECM. Thus, ECM remodeling and/or degradation by MMPs are expected to affect cell fate and behavior during many developmental and pathological processes. Numerous studies have shown that the expression of MMP mRNAs and proteins associates tightly with diverse developmental and pathological processes, such as tumor metastasis and mammary gland involution. In vivo evidence to support the roles of MMPs in these processes has been much harder to get. Here, we will review some of our studies on MMP11, or stromelysin-3, during the thyroid hormone-dependent amphibian metamorphosis, a process that resembles the so-called postembryonic development in mammals (from a few months before to several months after birth in humans when organ growth and maturation take place). Our investigations demonstrate that stromelysin-3 controls apoptosis in different tissues via at least two distinct mechanisms. PMID:20301218

Mathew, Smita; Fu, Liezhen; Hasebe, Takashi; Ishizuya-Oka, Atsuko; Shi, Yun-Bo

2010-03-01

13

Effects of Endocrine Disrupting Chemicals on Amphibian Metamorphosis and Mitochondrial Membrane Permeability Transition  

Microsoft Academic Search

The estrogenic chemical bisphenol A (BPA) has multiple hormonal activities, but its effects on thyroid hormone (TH) action are not fully understood. TH is required for the metamorphosis of tadpoles into frogs, and thus tadpole tail regression, one of the most spectacular events in metamorphosis, can be used for studying the effect of BPA and related compounds (BPAs) on TH

Akihiko Kashiwagi; Kozo Utsumi; Keiko Kashiwagi; Shigeru Ohta; Kazumi Sugihara; Hideki Hanada; Shigeyuki Kitamurad

2008-01-01

14

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...

15

The effects of coal tar based pavement sealer on amphibian development and metamorphosis.  

PubMed

Coal tar based pavement sealers are applied regularly to parking lots and contain significant levels of polycyclic aromatic hydrocarbons (PAHs). Recently a connection between elevated levels of PAHs in streams and storm water runoff from parking lots has been identified. We tested the hypothesis that coal tar based pavement sealers could alter the survival, growth, and development of amphibians using a model species, Xenopus laevis. Ten fertilized individuals were placed singly into containers containing one of four treatment groups: control, low, medium, and high (respective nominal concentrations 0, 3, 30, and 300 ppm TPAH). All of the individuals in the high exposure group died by the sixth day of exposure. By day 14 there were significant patterns of stunted growth (p<0.0001) and slower development (p=0.006) in the medium and high exposure groups relative to the control and low treatment groups. When the experiment ended on day 52 the control and low-dose individuals had achieved more advanced developmental stages than the medium group (p=0.0007). These data indicate that these commonly used coal tar based pavement sealers may potentially affect the amphibian taxa living in areas that receive storm water runoff. PMID:16557355

Bryer, Pamela J; Elliott, Jan N; Willingham, Emily J

2006-04-01

16

Latex laboratory-gloves: an unexpected pitfall in amphibian toxicity assays with tadpoles  

Microsoft Academic Search

This study examined the unexpected toxic effects of protective latex laboratory gloves on developing amphibians. Mortality after exposure to rinsing water from the outside of the gloves was observed in Xenopus laevis and Rana temporaria, with R. temporaria being more sensitive. This phenomenon was further confirmed using the microtiter-version of the Microtox-Assay, an in vitro assay for general toxicity. Latex

Arno C. Gutleb; Monique Bronkhorst; Johan H. J. van den Berg; Albertinka J. Murk

2001-01-01

17

Regulation of pituitary thyrotropin gene expression during Xenopus metamorphosis: negative feedback is functional throughout  

E-print Network

Regulation of pituitary thyrotropin gene expression during Xenopus metamorphosis: negative feedback is functional throughout metamorphosis Richard G Manzon and Robert J Denver Department of Molecular, Cellular regulation during amphibian metamorphosis, we analyzed multiple pituitary genes known or hypothesized

Denver, Robert J.

18

Amphibians  

Microsoft Academic Search

The unpredictable nature of flood and flow pulses and river floodplain networks create challenges for organisms, such as a\\u000a variety of anuran amphibian species, in their aquatic larval and terrestrial or semi-terrestrial life stages. These vertebrates\\u000a undoubtedly form an important component of the fauna of floodplains and may contribute to the rapid recycling of detritus\\u000a and mud (Welcomme 1990). Moreover,

Paola M. Peltzer; Rafael C. Lajmanovich

19

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

20

Caged amphibian tadpoles and in situ genotoxicity monitoring of aquatic environments with the alkaline single cell gel electrophoresis (comet) assay  

Microsoft Academic Search

In previous studies we demonstrated that indigenous amphibian tadpoles are suitable organisms for monitoring small bodies of water (e.g., creeks, ponds, and drainage ditches) using the alkaline single cell gel electrophoresis (SCG) or `comet' assay. This approach involves detection, under alkaline conditions, of cell DNA fragments which on electrophoresis migrate from the nuclear core, resulting in a `comet with tail'

Steven Ralph; Michael Petras

1998-01-01

21

Tissue-dependent developmental expression of a cytosolic thyroid hormone protein gene in Xenopus: its role in the regulation of amphibian metamorphosis.  

PubMed

We have cloned the cDNA encoding the Xenopus laevis homolog of mammalian cytosolic thyroid hormone binding protein (CTHBP). We found that while its mRNA level varies little in whole animals during development, the expression of CTHBP is inversely correlated with tissue-specific transformations during metamorphosis. A high level of its mRNA was observed in the tail of premetamorphic tadpoles. However, the expression is dramatically repressed with the onset of rapid tail resorption. In the hindlimb, the expression of CTHBP is very low during morphogenesis. Subsequently, its expression continuously increases during the period of limb growth. In contrast, a low level of CTHBP expression was detected in the intestine throughout metamorphosis. These results suggest that CTHBP could function to modulate the metamorphic process by regulating the level of intracellular thyroid hormones. PMID:7957964

Shi, Y B; Liang, V C; Parkison, C; Cheng, S Y

1994-11-21

22

Metamorphosis Metaphora  

E-print Network

, both in literary and visual symbolism, can aptly describe the changes, conditions, and stages of life. "Metamorphosis Metaphora" is an exhibition that embodies these ideas and also acts as a reflection of recent personal experiences....

Barton, Rebecca Rose

2011-04-25

23

Ontogenetic loss of phenotypic plasticity of age at metamorphosis in tadpoles  

Microsoft Academic Search

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

F. R. Hensley

1993-01-01

24

Plasticity of the duration of metamorphosis in the African clawed toad  

E-print Network

Plasticity of the duration of metamorphosis in the African clawed toad P. T. Walsh, J. R. Downie, such as amphibians, selection is thought to have minimized the duration of metamorphosis, because this is the stage risk associated with prolonging metamorphosis is presumed to have selected for a duration as short

Gray, Matthew

25

Cross-Talk Between Estrogen and Thyroid Hormones During Amphibian Development .  

E-print Network

??It is generally thought that in amphibians, thyroid hormones (THs) regulate metamorphosis, while sex steroids (estrogens and androgens) regulate gonadal differentiation. However, inhibition of TH… (more)

Duarte Guterman, Paula

2011-01-01

26

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

27

metamorphosis superintegrable systems  

E-print Network

Coupling constant metamorphosis and nth order symmetries for superintegrable systems with a survey constant metamorphosis andnth order symmetries for superintegrable systems -- p. 1/51 #12; Superintegrable of superintegrable system. Coupling constant metamorphosis andnth order symmetries for superintegrable systems -- p

Weinberger, Hans

28

Program Metamorphosis Christoph Reichenbach  

E-print Network

Program Metamorphosis by Christoph Reichenbach M.Sc., University of Colorado at Boulder, 2004;This dissertation entitled: Program Metamorphosis written by Christoph Reichenbach has been approved mentioned discipline. #12;iii Reichenbach, Christoph (Ph.D., Computer Science) Program Metamorphosis

Massachusetts at Amherst, University of

29

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. PMID:22629159

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

2012-01-01

30

ACY: February 22, 2005 Metamorphosis  

E-print Network

© ACY: February 22, 2005 Metamorphosis Think Ahead Time: enough to have appropriate stages that this process is called metamorphosis: change of form. 3. Students will be able to state that there are three types of metamorphosis: without metamorphosis, incomplete metamorphosis, and complete metamorphosis. 4

Ginzel, Matthew

31

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...

32

Volumebased threedimensional metamorphosis using  

E-print Network

Volume­based three­dimensional metamorphosis using region correspondence G.M. Treece, R.W. Prager Street Cambridge CB2 1PZ England E­mail: gmt11,rwp,ahg@eng.cam.ac.uk #12; Abstract The metamorphosis­dimensional (3­D) metamorphosis, where a surface is transformed into another surface. One approach

Drummond, Tom

33

Amphioxus postembryonic development reveals the homology of chordate metamorphosis.  

PubMed

Most studies in evolution are centered on how homologous genes, structures, and/or processes appeared and diverged. Although historical homology is well defined as a concept, in practice its establishment can be problematic, especially for some morphological traits or developmental processes. Metamorphosis in chordates is such an enigmatic character. Defined as a spectacular postembryonic larva-to-adult transition, it shows a wide morphological diversity between the different chordate lineages, suggesting that it might have appeared several times independently. In vertebrates, metamorphosis is triggered by binding of the thyroid hormones (THs) T(4) and T(3) to thyroid-hormone receptors (TRs). Here we show that a TH derivative, triiodothyroacetic acid (TRIAC), induces metamorphosis in the cephalochordate amphioxus. The amphioxus TR (amphiTR) mediates spontaneous and TRIAC-induced metamorphosis because it strongly binds to TRIAC, and a specific TR antagonist, NH3, inhibits both spontaneous and TRIAC-induced metamorphosis. Moreover, as in amphibians, amphiTR expression levels increase around metamorphosis and are enhanced by THs. Therefore, TH-regulated metamorphosis, mediated by TR, is an ancestral feature of all chordates. This conservation of a regulatory network supports the homology of metamorphosis in the chordate lineage. PMID:18514519

Paris, Mathilde; Escriva, Hector; Schubert, Michael; Brunet, Frédéric; Brtko, Julius; Ciesielski, Fabrice; Roecklin, Dominique; Vivat-Hannah, Valérie; Jamin, Emilien L; Cravedi, Jean-Pierre; Scanlan, Thomas S; Renaud, Jean-Paul; Holland, Nicholas D; Laudet, Vincent

2008-06-01

34

Amphibia-Reptilia 34 (2013): 151-162 A non-invasive water-borne hormone assay for amphibians  

E-print Network

in decreased growth and development as well as immunosuppression. In amphibians, corticosterone (CORT and field populations of amphibians and the effects of urbanization, pesticides and diseases. An important - U.S. Fish and Wildlife Service, San Marcos Aquatic Resources Center, 500 East McCarty Lane, San

Gabor, Caitlin - Department of Biology, Texas State University

35

Factors influencing amphibian susceptibility to infectious diseases, an  

E-print Network

amphibians fight back diseases? · Synergistic reaction ­ Endocrine system ­ Immune system · Fight or flight · Increase metabolism · Dilation of blood vessels Stress response: Fight? Stress factor Hypothalamic Metamorphosis Decrease Increase Acute Chronic Stress response: Flight? #12;3/13/13 4 Amphibian

Gray, Matthew

36

Prolactin is not a juvenile hormone in Xenopus laevis metamorphosis  

Microsoft Academic Search

Prolactin (PRL) is widely considered to be the juvenile hormone of anuran tadpoles and to counteract the effects of thyroid hormone (TH), the hormone that controls amphibian metamorphosis. This putative function was concluded mainly from experiments in which mammalian PRL was injected into tadpoles or added to cultured tadpole tissues. In this study, we show that overexpression of ovine or

Haochu Huang; Donald D. Brown

2000-01-01

37

Establishment of transactivation assay systems using fish, amphibian, reptilian and human thyroid hormone receptors.  

PubMed

Thyroid hormones are essential for the regulation of a wide range of biological processes associated with normal development and metabolism in vertebrates. For the screening of chemicals with a potential thyroid hormone and anti-thyroid hormone activities, we have established transient transactivation assay systems using thyroid hormone receptors (TR? and TR?) from three frog species (Xenopus laevis, Silurana tropicalis and Rana rugosa), a fish (Oryzias latipes), an alligator (Alligator mississippiensis) and a human (Homo sapiens). In all species examined, similar transcriptional activities were found for triiodothyronine (T3 : 10(-11) M in TR? and 10(-10) M in TR?) and thyroxine (T4 : 10(-9) M in TR? and 10(-8) M in TR?). Analogs of thyroid hormone (3,5,3',-triiodothyroacetic acid and 3,3',5,5'-tetraiodothyroacetic acid) exhibited weaker activity, requiring 10-fold higher concentrations for induction of activity when compared with T3 and T4 . These results provide support for the usefulness of in vitro screening assay systems as part of an approach to test chemicals for potential thyroid hormone receptor activity. In addition, we observed that T3 -stimulated transcriptional activity of the O. latipes TR? was inhibited by 10(-5) M tetrabromobisphenol A (TBBPA). In contrast, TR antagonist activities on TR? were not encountered in other species, even with TBBPA concentrations at 10(-5) M. In vitro transactivation assay systems using TRs from various species can be used for the screening of chemicals with thyroid-receptor agonist and antagonist activities. They also can be used for studies that examine evolutionary differences among species in the potency of TR activation. PMID:23112079

Oka, Tomohiro; Mitsui-Watanabe, Naoko; Tatarazako, Norihisa; Onishi, Yuta; Katsu, Yoshinao; Miyagawa, Shinichi; Ogino, Yukiko; Yatsu, Ryohei; Kohno, Satomi; Takase, Minoru; Kawashima, Yukio; Ohta, Yasuhiko; Aoki, Yasunobu; Guillette, Louis J; Iguchi, Taisen

2013-09-01

38

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 ?g L(-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 ?g L(-1), sodium arsenite induced statistically significant genotoxicity at 24, 48, 72 and 96 h of the exposure in a concentration-dependent manner. However, it did not show time effects as the highest frequency was found between 48 and 72 h 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

39

Tadpoles of Early Breeding Amphibians are Negatively Affected by Leaf Litter From Invasive Chinese Tallow Trees  

Microsoft Academic Search

As wetlands are invaded by Chinese tallow trees (Triadica sebifera), native trees are displaced and detrital inputs to amphibian breeding ponds are altered. I used a mesocosm experiment to examine the effect of Chinese tallow leaf litter on the survival to, size at, and time to metamorphosis of amphibian larvae. Fifty 1000-L cattle watering tanks were treated with 1500 g

N. E. Leonard

2005-01-01

40

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......

41

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

42

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...

43

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

44

Effects of the amphibian chytrid fungus and four insecticides on Pacific treefrogs (Pseudacris regilla)  

USGS Publications Warehouse

Chemical contamination may influence host-pathogen interactions, which has implications for amphibian population declines. We examined the effects of four insecticides alone or as a mixture on development and metamorphosis of Pacific Treefrogs (Pseudacris regilla) in the presence or absence of the amphibian chytrid fungus (Batrachochytrium dendrobatidis [Bd]). Bd exposure had a negative impact on tadpole activity, survival to metamorphosis, time to metamorphosis, and time of tail absorption (with a marginally negative effect on mass at metamorphosis); however, no individuals tested positive for Bd at metamorphosis. The presence of sublethal concentrations of insecticides alone or in a mixture did not impact Pacific Treefrog activity as tadpoles, survival to metamorphosis, or time and size to metamorphosis. Insecticide exposure did not influence the effect of Bd exposure. Our study did not support our prediction that effects of Bd would be greater in the presence of expected environmental concentrations of insecticide(s), but it did show that Bd had negative effects on responses at metamorphosis that could reduce the quality of juveniles recruited into the population.

Kleinhez, Peter; Boone, Michelle D.; Fellers, Gary

2012-01-01

45

Overwintered Bullfrog tadpoles negatively affect Salamanders and Anurans in native amphibian communities  

USGS Publications Warehouse

We examined the interactive effects of overwintered Bullfrog (Rana catesbeiana) tadpoles and pond hydroperiod on a community of larval amphibians in outdoor mesocosms including American Toads (Bufo americanus), Southern Leopard Frogs (Rana sphenocephala), and Spotted Salamanders (Ambystoma maculatum) - species within the native range of Bullfrogs. Spotted Salamanders and Southern Leopard Frogs were negatively influenced by the presence of overwintered Bullfrogs. Spotted Salamanders had shorter larval periods and slightly smaller masses at metamorphosis, and Southern Leopard Frogs had smaller masses at metamorphosis when reared with Bullfrogs than without. Presence of overwintered Bullfrogs, however, did not significantly affect American Toads. Longer pond hydroperiods resulted in greater survival, greater size at metamorphosis, longer larval periods, and later time until emergence of the first metamorphs for Southern Leopard Frog tadpoles and Spotted Salamander larvae. Our study demonstrated that overwintered Bullfrog tadpoles can respond to changing pond hydroperiods and can negatively impact metamorphosis of native amphibians.

Boone, M. D.; Little, E. E.; Semlitsch, R. D.

2004-01-01

46

Effects of an insecticide on amphibians in large-scale experimental ponds  

USGS Publications Warehouse

We examined the effects of the insecticide carbaryl on larval amphibian communities in large-scale experimental ponds. Tadpoles of two anurans, Woodhouse's toad (Bufo woodhousii) and southern leopard Frog (Rana sphenocephala), were reared in ponds (800 m3 volume) to determine the effects of tadpole density and carbaryl exposure on mass at metamorphosis and on time and survival to metamorphosis. Exposure to carbaryl significantly affected toads at metamorphosis, but not leopard frogs. Carbaryl exposure nearly doubled toad survival compared to controls; this effect may be attributable to an indirect effect of earbaryl increasing algal food resources. The competitive environment (i.e., density) and carbaryl exposure significantly affected the trade-off between mass and time to metamorphosis for toads. Our study is the first to demonstrate that in pond communities where predation and competition may be strong, short-lived insecticides can significantly alter the community dynamics of amphibians.

Boone, M.D.; Semlitsch, R.D.; Fairchild, J.F.; Rothermel, B.B.

2004-01-01

47

Vacuum-driven Metamorphosis  

E-print Network

We show that nonperturbative vacuum effects can produce a vacuum-driven transition from a matter-dominated universe to one in which the effective equation of state is that of radiation plus cosmological constant. The actual material content of the universe after the transition remains that of non-relativistic matter. This metamorphosis of the equation of state can be traced to nonperturbative vacuum effects that cause the scalar curvature to remain nearly constant at a well-defined value after the transition, and is responsible for the observed acceleration of the recent expansion of the universe.

Parker, L; Parker, Leonard; Raval, Alpan

1999-01-01

48

Vacuum-driven Metamorphosis  

E-print Network

We show that nonperturbative vacuum effects can produce a vacuum-driven transition from a matter-dominated universe to one in which the effective equation of state is that of radiation plus cosmological constant. The actual material content of the universe after the transition remains that of non-relativistic matter. This metamorphosis of the equation of state can be traced to nonperturbative vacuum effects that cause the scalar curvature to remain nearly constant at a well-defined value after the transition, and is responsible for the observed acceleration of the recent expansion of the universe.

Leonard Parker; Alpan Raval

1999-08-26

49

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

PubMed Central

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 time points (Days 0, 2, 12, 28), and used microarray analysis to quantify mRNA abundances. Results Individuals reared in the higher T4 concentration initiated morphological and transcriptional changes earlier and completed metamorphosis by Day 28. In contrast, initiation of metamorphosis was delayed in the lower T4 concentration and none of the individuals completed metamorphosis by Day 28. We identified 402 genes that were statistically differentially expressed by ? two-fold between T4 treatments at one or more non-Day 0 sampling times. To complement this analysis, we used linear and quadratic regression to identify 542 and 709 genes that were differentially expressed by ? two-fold in the 5 and 50 nM T4 treatments, respectively. Conclusion We found that T4 concentration affected the timing of gene expression and the shape of temporal gene expression profiles. However, essentially all of the identified genes were similarly affected by 5 and 50 nM T4. We discuss genes and biological processes that appear to be common to salamander and anuran metamorphosis, and also highlight clear transcriptional differences. Our results show that gene expression in axolotls is diverse and precise, and that axolotls provide new insights about amphibian metamorphosis. PMID:18267027

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

2008-01-01

50

Phylogenetic and expression analysis of amphibian Xenopus Toll-like receptors  

Microsoft Academic Search

An anuran amphibian, South African clawed frog (Xenopus\\u000a laevis), is used to study the immune system, as it possesses a set of acquired immune system represented by T and B lymphocytes\\u000a and the immunoglobulins. The acquired immune system is impaired throughout the larva and the metamorphosis stage in the amphibians.\\u000a On the other hand, the role of innate immune system

Akihiro Ishii; Miyuki Kawasaki; Misako Matsumoto; Shin Tochinai; Tsukasa Seya

2007-01-01

51

POPULATION ECOLOGY Amphibian lipid levels at metamorphosis correlate  

E-print Network

In organisms that have complex life cycles, factors in the larval environment may affect both larval and adult), with limited data for one anuran species (southern leopard frog, Rana sphenocep- hala). Lipid levels were correlates Á Lipids Á Postmetamorphic survival Á Trade-offs Introduction In organisms with complex life

Georgia, University of

52

The potential impact of simulated ground-water withdrawals on the oviposition, larval development, and metamorphosis of pond-breeding frogs  

Microsoft Academic Search

Wetland hydroperiod is a key factor for the reproductive success of pond-breeding amphibians. Ground-water withdrawals may\\u000a cause intermittent ponds to dry prematurely, potentially affecting amphibian development. In three intermittent ponds, we\\u000a monitored hydrology and tracked oviposition, larval development, and metamorphosis for three frog species that represented\\u000a a range of breeding phenologies. The three species were the southern leopard frog (Lithobates

John F. BunnellJennifer; Jennifer L. Ciraolo

2010-01-01

53

Atrazine Contamination in Water and the Impact on Amphibian Populations: A Bioassay That Measures Water Quality  

Microsoft Academic Search

In recent laboratory studies, we showed that atrazine, a common herbicide, can inhibit metamorphosis, produce hermaphrodites, and inhibit male development in amphibians. In part, these effects are due to a decrease in androgen levels. These effects occur at ecologically relevant low doses (0.1 ppb), and the effective levels are below the current drinking level standard and below contaminant levels found

T. B. Hayes

2001-01-01

54

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

55

Metamorphosis: State Assignment by Retiming and Reencoding  

E-print Network

Metamorphosis: State Assignment by Retiming and Re­encoding Category : 2 (Sequential Logic & Corresponding Author #12; Metamorphosis: State Assignment by Retiming and Re­encoding Category: 2 (Sequential Logic Synthesis and Verification) ABSTRACT This paper presents Metamorphosis 1 -- a novel technique

Ciesielski, Maciej

56

Metamorphosis in Escher's Art Craig S. Kaplan  

E-print Network

Metamorphosis in Escher's Art Craig S. Kaplan David R. Cheriton School of Computer Science of metamorphosis and deformation in his art, using a small set of pictorial devices to express this theme. I classify Escher's various approaches to metamorphosis, and relate them to the works in which they appear. I

Kaplan, Craig S.

57

3D Metamorphosis: a Survey Francis Lazarusy  

E-print Network

3D Metamorphosis: a Survey Francis Lazarusy and Anne Verroustz y I.R.C.O.M.-S.I.C. SP2MI, Boulevard.P. 105, 78153 Le Chesnay Cedex, FRANCE Abstract A metamorphosis or a (3D) morphing is the process representations. We conclude by sketching some morphing strategies for the future. Key Words: metamorphosis, shape

Paris-Sud XI, Université de

58

Three-Dimensional Distance Field Metamorphosis  

E-print Network

Three-Dimensional Distance Field Metamorphosis DANIEL COHEN-OR DAVID LEVIN and AMIRA SOLOMOVICI Tel field metamorphosis. In the presented method the interpolation of the distance field is guided by a warp-blending, warping 1. INTRODUCTION Surface metamorphosis is the continuous evolution of a surface from a source

Frey, Pascal

59

Feature-based image metamorphosis  

Microsoft Academic Search

A new technique is presented for the metamorphosis of one digital image into another. The approach gives the animator high-level control of the visual effect by providing natural feature-based specification and interaction. When used effectively, this technique can give the illusion that the photographed or computer generated subjects are transforming in a fluid, surrealistic, and often dramatic way. Comparisons with

Thaddeus Beier; Shawn Neely

1992-01-01

60

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

61

The Euler-Poincare theory of Metamorphosis  

E-print Network

In the pattern matching approach to imaging science, the process of ``metamorphosis'' is template matching with dynamical templates. Here, we recast the metamorphosis equations of into the Euler-Poincare variational framework of and show that the metamorphosis equations contain the equations for a perfect complex fluid \\cite{Ho2002}. This result connects the ideas underlying the process of metamorphosis in image matching to the physical concept of order parameter in the theory of complex fluids. After developing the general theory, we reinterpret various examples, including point set, image and density metamorphosis. We finally discuss the issue of matching measures with metamorphosis, for which we provide existence theorems for the initial and boundary value problems.

Holm, Darryl D; Younes, Laurent

2008-01-01

62

The Euler-Poincare theory of Metamorphosis  

E-print Network

In the pattern matching approach to imaging science, the process of ``metamorphosis'' is template matching with dynamical templates. Here, we recast the metamorphosis equations of into the Euler-Poincare variational framework of and show that the metamorphosis equations contain the equations for a perfect complex fluid \\cite{Ho2002}. This result connects the ideas underlying the process of metamorphosis in image matching to the physical concept of order parameter in the theory of complex fluids. After developing the general theory, we reinterpret various examples, including point set, image and density metamorphosis. We finally discuss the issue of matching measures with metamorphosis, for which we provide existence theorems for the initial and boundary value problems.

Darryl D. Holm; Alain Trouve; Laurent Younes

2008-06-04

63

A Role for Taiman in Insect Metamorphosis  

PubMed Central

Recent studies in vitro have reported that the Methoprene-tolerant (Met) and Taiman (Tai) complex is the functional receptor of juvenile hormone (JH). Experiments in vivo of Met depletion have confirmed this factor's role in JH signal transduction, however, there is no equivalent data regarding Tai because its depletion in larval or nymphal stages of the beetle Tribolium castaneum and the bug Pyrrhocoris apterus results in 100% mortality. We have discovered that the cockroach Blattella germanica possesses four Tai isoforms resulting from the combination of two indels in the C-terminal region of the sequence. The presence of one equivalent indel-1 in Tai sequences in T. castaneum and other species suggests that Tai isoforms may be common in insects. Concomitant depletion of all four Tai isoforms in B. germanica resulted in 100% mortality, but when only the insertion 1 (IN-1) isoforms were depleted, mortality was significantly reduced and about half of the specimens experienced precocious adult development. This shows that Tai isoforms containing IN-1 are involved in transducing the JH signal that represses metamorphosis. Reporter assays indicated that both T. castaneum Tai isoforms, one that contains the IN-1 and another that does not (DEL-1) activated a JH response element (kJHRE) in Krüppel homolog 1 in conjunction with Met and JH. The results indicate that Tai is involved in the molecular mechanisms that repress metamorphosis, at least in B. germanica, and highlight the importance of distinguishing Tai isoforms when studying the functions of this transcription factor in development and other processes. PMID:25356827

Lozano, Jesus; Kayukawa, Takumi; Shinoda, Tetsuro; Belles, Xavier

2014-01-01

64

A role for taiman in insect metamorphosis.  

PubMed

Recent studies in vitro have reported that the Methoprene-tolerant (Met) and Taiman (Tai) complex is the functional receptor of juvenile hormone (JH). Experiments in vivo of Met depletion have confirmed this factor's role in JH signal transduction, however, there is no equivalent data regarding Tai because its depletion in larval or nymphal stages of the beetle Tribolium castaneum and the bug Pyrrhocoris apterus results in 100% mortality. We have discovered that the cockroach Blattella germanica possesses four Tai isoforms resulting from the combination of two indels in the C-terminal region of the sequence. The presence of one equivalent indel-1 in Tai sequences in T. castaneum and other species suggests that Tai isoforms may be common in insects. Concomitant depletion of all four Tai isoforms in B. germanica resulted in 100% mortality, but when only the insertion 1 (IN-1) isoforms were depleted, mortality was significantly reduced and about half of the specimens experienced precocious adult development. This shows that Tai isoforms containing IN-1 are involved in transducing the JH signal that represses metamorphosis. Reporter assays indicated that both T. castaneum Tai isoforms, one that contains the IN-1 and another that does not (DEL-1) activated a JH response element (kJHRE) in Krüppel homolog 1 in conjunction with Met and JH. The results indicate that Tai is involved in the molecular mechanisms that repress metamorphosis, at least in B. germanica, and highlight the importance of distinguishing Tai isoforms when studying the functions of this transcription factor in development and other processes. PMID:25356827

Lozano, Jesus; Kayukawa, Takumi; Shinoda, Tetsuro; Belles, Xavier

2014-10-01

65

A Qualitative Meta-Analysis Reveals Consistent Effects of Atrazine on Freshwater Fish and Amphibians  

PubMed Central

Objective The biological effects of the herbicide atrazine on freshwater vertebrates are highly controversial. In an effort to resolve the controversy, we conducted a qualitative meta-analysis on the effects of ecologically relevant atrazine concentrations on amphibian and fish survival, behavior, metamorphic traits, infections, and immune, endocrine, and reproductive systems. Data sources We used published, peer-reviewed research and applied strict quality criteria for inclusion of studies in the meta-analysis. Data synthesis We found little evidence that atrazine consistently caused direct mortality of fish or amphibians, but we found evidence that it can have indirect and sublethal effects. The relationship between atrazine concentration and timing of amphibian metamorphosis was regularly nonmonotonic, indicating that atrazine can both accelerate and delay metamorphosis. Atrazine reduced size at or near metamorphosis in 15 of 17 studies and 14 of 14 species. Atrazine elevated amphibian and fish activity in 12 of 13 studies, reduced antipredator behaviors in 6 of 7 studies, and reduced olfactory abilities for fish but not for amphibians. Atrazine was associated with a reduction in 33 of 43 immune function end points and with an increase in 13 of 16 infection end points. Atrazine altered at least one aspect of gonadal morphology in 7 of 10 studies and consistently affected gonadal function, altering spermatogenesis in 2 of 2 studies and sex hormone concentrations in 6 of 7 studies. Atrazine did not affect vitellogenin in 5 studies and increased aromatase in only 1 of 6 studies. Effects of atrazine on fish and amphibian reproductive success, sex ratios, gene frequencies, populations, and communities remain uncertain. Conclusions Although there is much left to learn about the effects of atrazine, we identified several consistent effects of atrazine that must be weighed against any of its benefits and the costs and benefits of alternatives to atrazine use. PMID:20056568

Rohr, Jason R.; McCoy, Krista A.

2010-01-01

66

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

67

Juvenile hormones (JHs) are a class of regulatory sesquiterpenoids that control metamorphosis in immature  

E-print Network

Juvenile hormones (JHs) are a class of regulatory sesquiterpenoids that control metamorphosis glands with nervous connections to the brain, synthesize and release JH. The regulation of JH synthesis, 1992; Borovsky et al., 1992, 1994a,b); they developed an `exposed corpus allata' assay, i.e. the head

Noriega, Fernando Gabriel

68

Tadpoles of Early Breeding Amphibians are Negatively Affected by Leaf Litter From Invasive Chinese Tallow Trees  

NASA Astrophysics Data System (ADS)

As wetlands are invaded by Chinese tallow trees (Triadica sebifera), native trees are displaced and detrital inputs to amphibian breeding ponds are altered. I used a mesocosm experiment to examine the effect of Chinese tallow leaf litter on the survival to, size at, and time to metamorphosis of amphibian larvae. Fifty 1000-L cattle watering tanks were treated with 1500 g dry weight of one of five leaf litter treatments: Chinese tallow, laurel oak (Quercus laurifolia), water tupelo (Nyssa aquatica), slash pine (Pinus elliottii), or a 3:1:1:1 mixture. Each tank received 45 tadpoles of Pseudacris feriarum, Bufo terrestris, and Hyla cinerea in sequence according to their natural breeding phonologies. Every Pseudacris feriarum and Bufo terrestris tadpole exposed to Chinese tallow died prior to metamorphosis. Hyla cinerea survival in tanks with tallow-only was significantly lower than that observed for all other leaf treatments. Hyla cinerea tadpoles from tallow-only and mixed-leaf treatments were larger at metamorphosis and transformed faster than those in tanks with native leaves only. These results suggest that Chinese tallow leaf litter may negatively affect tadpoles of early breeding frogs and that Chinese tallow invasion may change the structure of amphibian communities in temporary ponds.

Leonard, N. E.

2005-05-01

69

Atrazine Contamination in Water and the Impact on Amphibian Populations: A Bioassay That Measures Water Quality  

NASA Astrophysics Data System (ADS)

In recent laboratory studies, we showed that atrazine, a common herbicide, can inhibit metamorphosis, produce hermaphrodites, and inhibit male development in amphibians. In part, these effects are due to a decrease in androgen levels. These effects occur at ecologically relevant low doses (0.1 ppb), and the effective levels are below the current drinking level standard and below contaminant levels found even in rainfall in some areas. Thus, the impact of this widespread compound on free-ranging amphibians is a concern. We undertook a large-scale study to examine atrazine levels in a variety of habitats (temporary pools, rivers, lakes and ponds, and field runoff) across the US where atrazine is used and areas that report no atrazine use. Also, we collected amphibians at each site to examine them for developmental abnormalities. These ongoing studies will help determine the extent of atrazine contamination and its potential impact on amphibian populations. The concern for atrazine's impact is increased, because the mechanism through which the compound produces this effect (inhibition of androgen production) is commonly observed in fish, reptiles and mammals in addition to amphibians, although amphibians appear to sensitive at much lower doses. Thus, effects on amphibians may indicate a much broader impact.

Hayes, T. B.

2001-12-01

70

The amphibian skin-associated microbiome across species, space and life history stages.  

PubMed

Skin-associated bacteria of amphibians are increasingly recognized for their role in defence against pathogens, yet we have little understanding of their basic ecology. Here, we use high-throughput 16S rRNA gene sequencing to examine the host and environmental influences on the skin microbiota of the cohabiting amphibian species Anaxyrus boreas, Pseudacris regilla, Taricha torosa and Lithobates catesbeianus from the Central Valley in California. We also studied populations of Rana cascadae over a large geographic range in the Klamath Mountain range of Northern California, and across developmental stages within a single site. Dominant bacterial phylotypes on amphibian skin included taxa from Bacteroidetes, Gammaproteobacteria, Alphaproteobacteria, Firmicutes, Sphingobacteria and Actinobacteria. Amphibian species identity was the strongest predictor of microbial community composition. Secondarily, within a given amphibian species, wetland site explained significant variation. Amphibian-associated microbiota differed systematically from microbial assemblages in their environments. Rana cascadae tadpoles have skin bacterial communities distinct from postmetamorphic conspecifics, indicating a strong developmental shift in the skin microbes following metamorphosis. Establishing patterns observed in the skin microbiota of wild amphibians and environmental factors that underlie them is necessary to understand skin symbiont community assembly, and ultimately, the role skin microbiota play in the extended host phenotype including disease resistance. PMID:24171949

Kueneman, Jordan G; Parfrey, Laura Wegener; Woodhams, Douglas C; Archer, Holly M; Knight, Rob; McKenzie, Valerie J

2014-03-01

71

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

PubMed

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. PMID:22957147

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

2012-07-01

72

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. PMID:22957147

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

2012-01-01

73

Amphibians of Washington  

NSDL National Science Digital Library

This resource on the Amphibians of Washington State has recently been placed online. Created by Brad Moon at the University of Washington at Seattle's Burke Museum of Natural History and Culture (Herpetology Section), the Website features northwestern amphibians. The Website is organized by Order, Family, and Species, with details provided for some species, including a color photograph, written description, and information on Distribution, Habitat, Cool Biology Facts, and Conservation status. Other information accessible via links includes distribution maps, identification keys, phylogenetic information, and online bibliographies. For students and researchers seeking basic information and natural history facts on Washington's amphibians, this resource is a nice reference.

Moon, Brad.

74

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. PMID:22655067

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

2012-01-01

75

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. PMID:22163335

Chen, Guangchun; Robert, Jacques

2011-01-01

76

Interaction between perchlorate and iodine in the metamorphosis of Hyla versicolor  

USGS Publications Warehouse

Perchlorate (ClO4-) is a water-soluble, inorganic anion that is often combined with ammonium, potassium or other cations for use in industry and agriculture. Ammonium perchlorate, for example, is a potent oxidizer and is used in various military applications including rocket fuel. It has also been found in an historically widely used fertilizer, Chilean nitrate and in other fertilizers. It has been found in ground and surface waters of over 30 states and is considered a human health risk. Because of its similar atomic radius and volume, perchlorate competes with iodide for thyroid uptake and storage and thereby inhibits production of thyroid hormones. Amphibians may be particularly affected by perchlorate because they rely on the thyroid for metamorphosis. This study exposed early larval Hyla versicolor to concentrations of perchlorate ranging from 2.2 to 50 ppm to determine the effects of perchlorate on a native amphibian. In addition, three controls, 0 perchlorate, 0 perchlorate with 0.10 ppm iodide (C + I) and 50 ppm perchlorate + 0.10 ppm iodide (50 + I) were tested. Mortality (<11% with all treatments) and growth appeared to be unaffected by perchlorate. Inhibition of development started with 2.2 ppm perchlorate and little or no development occurred at 22.9 ppm and above. This inhibition was particularly apparent at the latter stages of development including hindlimb formation and metamorphosis. The estimated EC50 for total inhibition of metamorphosis at 70 days of treatment was 3.63 ppm. There was no evidence of inhibition of development with the 50 + I, C + I, or controls, indicating that the presence of small concentrations of iodide could counter the effects of perchlorate. When tadpoles that had been inhibited by perchlorate were subsequently treated with iodide, development through prometamorphosis progressed but mortality was very high.

Sparling, D.W.; Harvey, G.; Nzengung, V.

2003-01-01

77

Interaction between perchlorate and iodine in the metamorphosis of Hyla versicolor  

USGS Publications Warehouse

Perchlorate (ClO4-) is a water-soluble, inorganic anion that is often combined with ammonium, potassium or other cations for use in industry and agriculture. Ammonium perchlorate, for example, is a potent oxidizer and is used in various military applications including rocket fuel. It has also been found in an historically widely used fertilizer, Chilean nitrate and in other fertilizers. It has been found in ground and surface waters of over 30 states and is considered a human health risk. Because of its similar atomic radius and volume, perchlorate competes with iodide for thyroid uptake and storage and thereby inhibits production of thyroid hormones. Amphibians may be particularly affected by perchlorate because they rely on the thyroid for metamorphosis. This study exposed early larval Hyla versicolor to concentrations of perchlorate ranging from 2.2 to 50 ppm to determine the effects of perchlorate on a native amphibian. In addition, three controls, 0 perchlorate, 0 perchlorate with 0.10 ppm iodide (C + I) and 50 ppm perchlorate + 0.10 ppm iodide (50 + I) were tested. Mortality (< 11% with all treatments) and growth appeared to be unaffected by perchlorate. Inhibition of development started with 2.2 ppm perchlorate and little or no development occurred at 22.9 ppm and above. This inhibition was particularly apparent at the latter stages of development including hindlimb formation and metamorphosis. The estimated EC50 for total inhibition of metamorphosis at 70 days of treatment was 3.63 ppm. There was no evidence of inhibition of development with the 50 + I, C + I, or controls, indicating that the presence of small concentrations of iodide could counter the effects of perchlorate. When tadpoles that had been inhibited by perchlorate were subsequently treated with iodide, development through prometamorphosis progressed but mortality was very high.

Sparling, D.; Harvey, G.; Nzengung, V.

2003-01-01

78

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

79

Growth and developmental effects of coal combustion residues on Southern Leopard Frog (Rana sphenocephala) tadpoles exposed throughout metamorphosis  

SciTech Connect

The effects of aquatic deposition of coal combustion residues (CCRs) on amphibian life histories have been the focus of many recent studies. In summer 2005, we raised larval Southern Leopard Frogs, Rana sphenocephala, on either sand or CCR substrate (approximately 1 cm deep within plastic bins) and documented effects of sediment type on oral disc condition, as well as time to, mass at, and total body length at key developmental stages, including metamorphosis (Gosner stages (GS) 37, 42, and 46). We found no significant difference in mortality between the two treatments and mortality was relatively low (eight of 48 in the control group and four of 48 in the CCR group). Ninety percent of exposed tadpoles displayed oral disc abnormalities, while no control individuals displayed abnormalities. Tadpoles raised on CCR-contaminated sediment had decreased developmental rates and weighed significantly less at all developmental stages, on average, when compared to controls. The CCR treatment group was also significantly shorter In length than controls at the completion of metamorphosis (GS 46). Collectively, these findings are the most severe sub-lethal effects noted for any amphibian exposed to CCRs to date. More research is needed to understand how these long term effects may contribute to the dynamics of local amphibian populations.

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

2008-09-15

80

Transgenic analysis reveals that thyroid hormone receptor is sufficient to mediate the thyroid hormone signal in frog metamorphosis.  

PubMed

Thyroid hormone (T3) has long been known to be important for vertebrate development and adult organ function. Whereas thyroid hormone receptor (TR) knockout and transgenic studies of mice have implicated TR involvement in mammalian development, the underlying molecular bases for the resulting phenotypes remain to be determined in vivo, especially considering that T3 is known to have both genomic, i.e., through TRs, and nongenomic effects on cells. Amphibian metamorphosis is an excellent model for studying the role of TR in vertebrate development because of its total dependence on T3. Here we investigated the role of TR in metamorphosis by developing a dominant positive mutant thyroid hormone receptor (dpTR). In the frog oocyte transcription system, dpTR bound a T3-responsive promoter and activated the promoter independently of T3. Transgenic expression of dpTR under the control of a heat shock-inducible promoter in premetamorphic tadpoles led to precocious metamorphic transformations. Molecular analyses showed that dpTR induced metamorphosis by specifically binding to known T3 target genes, leading to increased local histone acetylation and gene activation, similar to T3-bound TR during natural metamorphosis. Our experiments indicated that the metamorphic role of T3 is through genomic action of the hormone, at least on the developmental parameters tested. They further provide the first example where TR is shown to mediate directly and sufficiently these developmental effects of T3 in individual organs by regulating target gene expression in these organs. PMID:15456876

Buchholz, Daniel R; Tomita, Akihiro; Fu, Liezhen; Paul, Bindu D; Shi, Yun-Bo

2004-10-01

81

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

82

Toxicity of two insecticides to California, USA, anurans and its relevance to declining amphibian populations.  

PubMed

Contaminants have been associated with population declines of several amphibian species in California (USA). Pesticides from the Central Valley of California are transported by winds into the Sierra Nevada Mountains and precipitate into wet meadows where amphibians breed. The present study examined the chronic toxicity of two of the insecticides most commonly used in the Central Valley and found in the mountains, chlorpyrifos and endosulfan, to larval Pacific treefrogs (Pseudacris regilla) and foothill yellow-legged frogs (Rana boylii) and discusses the implications of this toxicity to declining amphibian populations. Larvae were exposed to the pesticides from Gosner stages 25 to 26 through metamorphosis. The estimated median lethal concentration (LC50) for chlorpyrifos was 365 microg/L in P. regilla and 66.5 microg/L for R. boylii. Time to metamorphosis increased with concentration of chlorpyrifos in both species, and cholinesterase activity declined with exposure concentration in metamorphs of both species at Gosner stages 42 to 46. For endosulfan, the estimated LC50 was 15.6 microg/L for P. regilla and 0.55 microg/L for R. boylii. All R. boylii exposed to concentrations of greater than 0.8 microg/L died before they entered metamorphosis. Pseudacris regilla remains relatively abundant and is broadly distributed throughout California. In contrast, R. boylii is among the species experiencing severe population declines. The present study adds to the increasing evidence that pesticides are very harmful to amphibians living in areas that are miles from sources of pesticide application. PMID:19290680

Sparling, Donald W; Fellers, Gary M

2009-08-01

83

Skeletal metamorphosis in fibrodysplasia ossificans progressiva (FOP)  

PubMed Central

Metamorphosis, the transformation of one normal tissue or organ system into another, is a biological process rarely studied in higher vertebrates or mammals, but exemplified pathologically by the extremely disabling autosomal dominant disorder fibrodysplasia ossificans progressiva (FOP). The recurrent single nucleotide missense mutation in the gene encoding activin receptor IA/activin-like kinase-2 (ACVR1/ALK2), a bone morphogenetic protein type I receptor that causes skeletal metamorphosis in all classically affected individuals worldwide, is the first identified human metamorphogene. Physiological studies of this metamorphogene are beginning to provide deep insight into a highly conserved signaling pathway that regulates tissue stability following morphogenesis, and that when damaged at a highly specific locus (c.617G > A; R206H), and triggered by an inflammatory stimulus permits the renegade metamorphosis of normal functioning connective tissue into a highly ramified skeleton of heterotopic bone. A comprehensive understanding of the process of skeletal metamorphosis, as revealed by the rare condition FOP, will lead to the development of more effective treatments for FOP and, possibly, for more common disorders of skeletal metamorphosis. PMID:18979151

Shen, Qi; Lounev, Vitali; Seemann, Petra; Groppe, Jay; Katagiri, Takenobu; Pignolo, Robert J.; Shore, Eileen M.

2013-01-01

84

How Do Amphibians Go Extinct?  

Microsoft Academic Search

Many causes have been proposed to explain the global decline of amphibian populations. These include acid precipitation, UV-b radiation, epidemic diseases, deformities, habitat disruption, etc. Amphibians are noted for their bi-phasic life histories, supposedly limited abilities to disperse, and permeable skins, yet amphibians also exhibit enormous variation in life histories and can maintain large populations. How do these intrinsic factors

David M. Green

85

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. PMID:22662314

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

2011-01-01

86

Metamorphosis of Tangential Visual System Neurons in Drosophila  

E-print Network

Metamorphosis of Tangential Visual System Neurons in Drosophila Paul H. Taghert,1 Marie E. Roberts differentiation at the start of metamorphosis. The numerous small OL3 neurons are generated postembry- onically and first detected later in metamorphosis. The onset of dFMRFa transcription coincides

Renn, Susan C.P.

87

Three-Dimensional Metamorphosis using Multiplanar Representation Mahesh Ramasubramanian  

E-print Network

Three-Dimensional Metamorphosis using Multiplanar Representation Mahesh Ramasubramanian Program method for three-dimensional metamorphosis between two polyhedral objects with differ- ent topologies the intermediate 3D objects. The user controls the metamorphosis by match- ing features during the 2D morphing

Mittal, Anurag

88

MicroRNA-dependent metamorphosis in hemimetabolan insects  

E-print Network

MicroRNA-dependent metamorphosis in hemimetabolan insects Eva Gomez-Orte and Xavier Belles1 metamorphosis, has fasci- nated mankind since ancient times. Modern physiology has estab- lished the endocrine biological processes, and we wondered whether they might be also involved in insect metamorphosis. In insects

Belles, Xavier

89

Ecdysone signaling at metamorphosis triggers apoptosis of Drosophila abdominal muscles  

E-print Network

Ecdysone signaling at metamorphosis triggers apoptosis of Drosophila abdominal muscles Jonathan KeywordsQ3 : Metamorphosis Muscle Drosophila Histolysis Apoptosis Autophagy Ecdysone Ftz-f1 a b s t r a c t One of the most dramatic examples of programmed cell death occurs during Drosophila metamorphosis

Perrimon, Norbert

90

Fast and Intuitive Metamorphosis of 3D Polyhedral Models Using  

E-print Network

Fast and Intuitive Metamorphosis of 3D Polyhedral Models Using SMCC Mesh Merging Scheme Tong-Yee Lee and Po-Hua Huang Abstract--A very fast and intuitive approach to generate the metamorphosis of two polyhedral metamorphosis. We demonstrate several examples of aesthetically pleasing morphs, which can

Chen, Sheng-Wei

91

Shadow Metamorphosis Bertrand Klimmek, Hartmut Prautzsch, Nikolaus Vahrenkamp  

E-print Network

Shadow Metamorphosis Bertrand Klimmek, Hartmut Prautzsch, Nikolaus Vahrenkamp {klimmek a metamorphosis A B, we could also replace R by any other continuous motion Mt, t [0, 1], that brings A Ã? B into the position B Ã? A. However, the metamorphosis resulting from R has particular nice characteris- tics as we

Prautzsch, Hartmut

92

Metamorphosis of 3D Polyhedral Models Using Progressive Connectivity Transformations  

E-print Network

Metamorphosis of 3D Polyhedral Models Using Progressive Connectivity Transformations Chao-Hung Lin and Tong-Yee Lee, Member, IEEE Abstract--Three-dimensional metamorphosis is a powerful technique to produce are demonstrated using the proposed method. Index Terms--Metamorphosis, connectivity fransformation, embedding

Chen, Sheng-Wei

93

Interior Modelling and Object Metamorphosis with Parametric Solids  

E-print Network

Interior Modelling and Object Metamorphosis with Parametric Solids Roman Durikovic and Silvester methodology and modelling tech- nique is applied to metamorphosis of two given 3-D shapes. 1. Introduction metamorphosis is discussed in Section 4.. 2. Three Construction Steps of Coons Body We will restrict ourselves

Durikovic, Roman

94

Volume-based three-dimensional metamorphosis using  

E-print Network

Volume-based three-dimensional metamorphosis using region correspondence G.M. Treece, R.W. Prager Street Cambridge CB2 1PZ England E-mail: gmt11,rwp,ahg@eng.cam.ac.uk #12;Abstract The metamorphosis-dimensional (3-D) metamorphosis, where a surface is transformed into another surface. One approach

Drummond, Tom

95

THREE-DIMENSIONAL OBJECT METAMORPHOSIS THROUGH ENERGY MINIMIZATION  

E-print Network

WSCG'97 THREE-DIMENSIONAL OBJECT METAMORPHOSIS THROUGH ENERGY MINIMIZATION IOANNIS KORFIATIS Ltd. All rights reserved. Key words: metamorphosis, energy minimization, shortest path algorithm metamorphosis involves a pair of objects represented as a collection of polygons. The vertices of the ®rst

Frey, Pascal

96

Synaptogenesis in the Mushroom Body Calyx During Metamorphosis in the  

E-print Network

Synaptogenesis in the Mushroom Body Calyx During Metamorphosis in the Honeybee Apis mellifera- phosis. We show that synaptogenesis in the mushroom body calycal neuropile starts in early metamorphosis of the adult calyx first appear at stage P8 but remain rare toward the end of metamorphosis. Our observations

Menzel, Randolf - Institut für Biologie

97

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.

2000-01-01

98

Figure 1. A texture metamorphosis sequence is generated from the leftmost to the rightmost. Pattern-based Texture Metamorphosis  

E-print Network

Figure 1. A texture metamorphosis sequence is generated from the leftmost to the rightmost. Pattern-based Texture Metamorphosis Ziqiang Liu Ce Liu Heung-Yeung Shum Yizhou Yu Microsoft Research Asia Zhejiang}@microsoft.com yyz@cs.uiuc.edu Abstract In this paper, we study texture metamorphosis, or how to generate texture

Oishi, Takeshi

99

Rainforest: Reptiles and Amphibians  

ERIC Educational Resources Information Center

Rainforest reptiles and amphibians are a vibrantly colored, multimedia art experience. To complete the entire project one may need to dedicate many class periods to production, yet in each aspect of the project a new and important skill, concept, or element is being taught or reinforced. This project incorporates the study of warm and cool color…

Olson, Susanna

2006-01-01

100

Global Amphibian Declines:Global Amphibian Declines: What Have We Done?What Have We Done?  

E-print Network

disturbance Direct Road disturbance Introduced amphibian and fish species Global warming UV-B radiation Acid1 Global Amphibian Declines:Global Amphibian Declines: What Have We Done?What Have We Done? Nikki Global Amphibian Assessment #12;2 Current Status of Amphibian PopulationsCurrent Status of Amphibian

Gray, Matthew

101

ThreeDimensional Distance Field Metamorphosis  

E-print Network

of the 3D model. Such view­dependent effects are impossible with image­space metamorphosis. This paper. This object­ space process of generating intermediate 3D models is to be distinguished from image of a source 3D model (on the upper left) into a target 3D model (on the bottom right). Note that the camera

Levin, David

102

Origin and Evolution of Insect Metamorphosis  

E-print Network

Origin and Evolution of Insect Metamorphosis Xavier Belles, Institute of Evolutionary Biology (CSIC are still obscure. Introduction One of the first formal theories related to the origin of insect, quiescent stage (as crickets and cockroaches); a third type was represented by species whose wings develop

Belles, Xavier

103

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

104

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

105

Hormonal Correlates of Environmentally Induced Metamorphosis in the Western Spadefoot Toad,  

E-print Network

Hormonal Correlates of Environmentally Induced Metamorphosis in the Western Spadefoot Toad to accelerate metamorphosis when their ponds dry. To understand the proximate mechanisms that mediate. Tad- poles exposed to a declining water level accelerated metamorphosis compared with tadpoles raised

Denver, Robert J.

106

No evidence for Dark Energy Metamorphosis ?  

E-print Network

Recent attempts to fit Type Ia supernova data by modeling the dark energy density as a truncated Taylor series have suggested the possibility of metamorphosis, i.e., a rapidly evolving equation of state parameter, w_DE(z). However, we show that fits using that parametrization have significant problems: evolution of w_DE(z) is both favoured and in some sense forced, and the equation of state parameter blows up or diverges in large regions of the parameter space used for the truncated series. To further elucidate these problems we have simulated sets of supernova data in a Lambda-universe to show that the suggested ``evidence'' for metamorphosis is also common for w_DE=-1.

Jonsson, J; Amanullah, R; Bergström, L

2004-01-01

107

No evidence for Dark Energy Metamorphosis ?  

E-print Network

Recent attempts to fit Type Ia supernova data by modeling the dark energy density as a truncated Taylor series have suggested the possibility of metamorphosis, i.e., a rapidly evolving equation of state parameter, w_DE(z). However, we show that fits using that parametrization have significant problems: evolution of w_DE(z) is both favoured and in some sense forced, and the equation of state parameter blows up or diverges in large regions of the parameter space. To further elucidate these problems we have simulated sets of supernova data in a Lambda-universe to show that the suggested ``evidence'' for metamorphosis is also common for w_DE=-1.

J. Jonsson; A. Goobar; R. Amanullah; L. Bergstrom

2004-04-23

108

Processor Reconfiguration Through Instruction-Set Metamorphosis  

Microsoft Academic Search

The processor reconfiguration through instruction-set metamorphosis (PRISM) general-purpose architecture, which speeds up computationally intensive tasks by augmenting the core processor's functionality with new operations, is described. The PRISM approach adapts the configuration and fundamental operations of a core processing system to the computationally intensive portions of a targeted application. PRISM-1, an initial prototype system, is described, and experimental results that

Peter M. Athanas; Harvey F. Silverman

1993-01-01

109

Homeomorphisms and Metamorphosis of Polyhedral Models Using Fields of Directions Defined on  

E-print Network

1 Homeomorphisms and Metamorphosis of Polyhedral Models Using Fields of Directions Defined interpolation and metamorphosis. Morphing animations have achieved widespread use in the entertainment industry

Kallmann, Marcelo

110

Interpreting in vivo Effects of Thyroid Synthesis Inhibitors through the Lens of in vitro and ex vivo Assays  

EPA Science Inventory

The US EPA has been charged to evaluate chemicals for their ability to disrupt endocrine pathways including estrogen, androgen, and thyroid hormone. Amphibian metamorphosis, which is regulated by thyroid hormone, is an ideal model system for investigating disruption of the thyroi...

111

Larval habitat duration and size at metamorphosis in frogs  

Microsoft Academic Search

The relationship between size at metamorphosis and adult size was studied in 12 closely-related species of frog from Malawi (Central Africa). These species of frogs breed in water of different durations, and occupy different habitats as adults. We could demonstrate no correlation between size at metamorphosis and size of adults when frogs were divided into groups on the basis of

Jeremy W. Patterson; Athol J. McLachlan

1989-01-01

112

Active metabolism of thyroid hormone during metamorphosis of amphioxus.  

PubMed

Thyroid hormones (THs), and more precisely the 3,3',5-triiodo-l-thyronine (T(3)) acetic derivative 3,3',5-triiodothyroacetic acid (TRIAC), have been shown to activate metamorphosis in amphioxus. However, it remains unknown whether TRIAC is endogenously synthesized in amphioxus and more generally whether an active TH metabolism is regulating metamorphosis. Here we show that amphioxus naturally produces TRIAC from its precursors T(3) and l-thyroxine (T(4)), supporting its possible role as the active TH in amphioxus larvae. In addition, we show that blocking TH production inhibits metamorphosis and that this effect is compensated by exogenous T(3), suggesting that a peak of TH production is important for advancement of proper metamorphosis. Moreover, several amphioxus genes encoding proteins previously proposed to be involved in the TH signaling pathway display expression profiles correlated with metamorphosis. In particular, thyroid hormone receptor (TR) and deiodinases gene expressions are either up- or down-regulated during metamorphosis and by TH treatments. Overall, these results suggest that an active TH metabolism controls metamorphosis in amphioxus, and that endogenous TH production and metabolism as well as TH-regulated metamorphosis are ancestral in the chordate lineage. PMID:21558188

Paris, Mathilde; Hillenweck, Anne; Bertrand, Stéphanie; Delous, Georges; Escriva, Hector; Zalko, Daniel; Cravedi, Jean-Pierre; Laudet, Vincent

2010-07-01

113

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

114

Batrachochytrium dendrobatidis prevalence and haplotypes in domestic and imported pet amphibians in Japan.  

PubMed

The international trade in amphibians is believed to have increased the spread of Batrachochytrium dendrobatidis (Bd), the fungal pathogen responsible for chytridiomycosis, which has caused a rapid decline in amphibian populations worldwide. We surveyed amphibians imported into Japan and those held in captivity for a long period or bred in Japan to clarify the Bd infection status. Samples were taken from 820 individuals of 109 amphibian species between 2008 and 2011 and were analyzed by a nested-PCR assay. Bd prevalence in imported amphibians was 10.3% (58/561), while it was 6.9% (18/259) in those in private collections and commercially bred amphibians in Japan. We identified the genotypes of this fungus using partial DNA sequences of the internal transcribed spacer (ITS) region. Sequencing of PCR products of all 76 Bd-positive samples revealed 11 haplotypes of the Bd ITS region. Haplotype A (DNA Data Bank of Japan accession number AB435211) was found in 90% (52/58) of imported amphibians. The results show that Bd is currently entering Japan via the international trade in exotic amphibians as pets, suggesting that the trade has indeed played a major role in the spread of Bd. PMID:24991744

Tamukai, Kenichi; Une, Yumi; Tominaga, Atsushi; Suzuki, Kazutaka; Goka, Koichi

2014-05-13

115

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

116

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

E-print Network

Nitric Oxide Inhibits Metamorphosis in Larvae of Crepidula fornicata, the Slippershell Snail JAN A metamorphosis in the marine gastropod Crepidula fornicata. Metamorphosis was stimulated by the nitric oxide) at concentrations of about 100­1000 mol l 1 and 50­200 mol l 1 , respectively. Metamorphosis was not, however

117

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

118

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. PMID:24086681

Strauss, Alex; Smith, Kevin G.

2013-01-01

119

Profound morphological and functional changes of rodent Purkinje cells between the first and the second postnatal weeks: a metamorphosis?  

PubMed Central

Between the first and the second postnatal week, the development of rodent Purkinje cells is characterized by several profound transitions. Purkinje cells acquire their typical dendritic “espalier” tree morphology and form distal spines. During the first postnatal week, they are multi-innervated by climbing fibers and numerous collateral branches sprout from their axons, whereas from the second postnatal week, the regression of climbing fiber multi-innervation begins, and Purkinje cells become innervated by parallel fibers and inhibitory molecular layer interneurons. Furthermore, their periods of developmental cell death and ability to regenerate their axon stop and their axons become myelinated. Thus a Purkinje cell during the first postnatal week looks and functions differently from a Purkinje cell during the second postnatal week. These fundamental changes occur in parallel with a peak of circulating thyroid hormone in the mouse. All these features suggest to some extent an interesting analogy with amphibian metamorphosis. PMID:22514522

Dusart, Isabelle; Flamant, Frederic

2012-01-01

120

Climate warming mediates negative impacts of rapid pond drying for three amphibian species.  

PubMed

Anthropogenic climate change will present both opportunities and challenges for pool-breeding amphibians. Increased water temperature and accelerated drying may directly affect larval growth, development, and survival, yet the combined effects of these processes on larvae with future climate change remain poorly understood. Increased surface temperatures are projected to warm water and decrease water inputs, leading to earlier and faster wetland drying. So it is often assumed that larvae will experience negative synergistic impacts with combined warming and drying. However, an alternative hypothesis is that warming-induced increases in metabolic rate and aquatic resource availability might compensate for faster drying rates, generating antagonistic larval responses. We conducted a mesocosm experiment to test the individual and interactive effects of pool permanency (permanent vs. temporary) and water temperature (ambient vs. (+) -3 degrees C) on three anurans with fast-to-slow larval development rates (Great Basin spadefoot [Spea intermontana], Pacific chorus frog [Pseudacris regilla], and northern red-legged frog [Rana aurora]). We found that although tadpoles in warmed pools reached metamorphosis 15-17 days earlier, they did so with little cost (< 2 mm) to size, likely due to greater periphyton growth in warmed pools easing drying-induced resource competition. Warming and drying combined to act antagonistically on early growth (P = 0.06) and survival (P = 0.06), meaning the combined impact was less than the sum of the individual impacts. Warming and drying acted additively on time to and size at metamorphosis. These nonsynergistic impacts may result from cotolerance of larvae to warming and drying, as well as warming helping to offset negative impacts of drying. Our results indicate that combined pool warming and drying may not always be harmful for larval amphibians. However, they also demonstrate that antagonistic responses are difficult to predict, which poses a challenge to proactive conservation and management. Our study highlights the importance of considering the nature of multiple stressor interactions as amphibians are exposed to an increasing number of anthropogenic threats. PMID:24933805

O'Regan, Sacha M; Palen, Wendy J; Anderson, Sean C

2014-04-01

121

This information sheet is for the care and use of amphibians. Potential Zoonotic Diseases for Amphibians  

E-print Network

. There are, however, a few agents that are found in amphibians and aquarium water that have the potential to Amphibians: Human sensitivity to amphibian proteins in the laboratory setting is rare. It remains possible, however, to become sensitized to amphibian proteins through inhalation or skin contact. You are strongly

Wood, Marcelo A.

122

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

E-print Network

LETTER An examination of amphibian sensitivity to environmental contaminants: are amphibians poor, there has been no systematic evaluation of amphibian sensitivity to environmental challenges relative found that amphibians only exhibit moderate relative responses to water-borne toxins. Our findings imply

Storfer, Andrew

123

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

124

Effects of polychlorinated biphenyl 126 on green frog (Rana clamitans) and leopard frog (Rana pipiens) hatching success, development, and metamorphosis  

SciTech Connect

Although increasing evidence links plana chlorinated hydrocarbons, such as polychlorinated biphenyls (PCBs), to decreases in survival and reproduction of fish, mammals, and birds near Green Bay, Wisconsin, and the Great Lakes, USA, relatively little is known of their bioaccumulation or of their possible effects in amphibians. The authors exposed embryos and larvae of two ranid species commonly occurring in the Green Bay ecosystem, the green frog (Rana clamitans) and the leopard frog (Rana pipiens), to PCB 126, a model coplanar PCB compound. Nominal concentrations ranged from 0.005 to 50 {micro}g/L, and exposure lasted through metamorphosis. Tissue concentrations of PCB 126 in tadpoles that did not metamorphose by the end of the experiment ranged from 1.2 to 9,600 ng/g wet mass. No significant mortality of embryos occurred before hatching; however, survival of larvae was significantly reduced at the highest concentration for both species. Few deformities were observed, but the incidence of edema was significantly higher in tadpoles exposed to 50 {micro}g/L. Swimming speed and growth of tadpoles was also significantly reduced in this treatment. The percent of tadpoles that reached metamorphosis was significantly lower in green frogs at the highest concentration, and no leopard frogs survived past day 47 of the experiment in this treatment. At high concentrations, PCB 126 affected both ranid species; however, sublethal effects were not apparent for the parameters the authors measured at concentrations that occur in water in the Green Bay ecosystem.

Rosenshield, M.L.; Jofre, M.B.; Karasov, W.H.

1999-11-01

125

Thermal and Shock Metamorphosis in NWA-5011 L6 Chondrite  

NASA Astrophysics Data System (ADS)

This work emphasize shock and thermal metamorphosis of meteorites, description of chondrule textures and their impact-related alteration processes (e.g. shearing, formation of high pressure minerals), and reclassification of petrologic type NWA 5011.

Gyollai, I.; Bérczi, Sz.; Nagy, Sz.; Gucsik, A.

2014-11-01

126

Amphibians Used in Research and Teaching  

Microsoft Academic Search

Amphibians have long been utilized in scientific research and in education. Historically, investigators have accumu- lated a wealth of information on the natural history and biology of amphibians, and this body of information is con- tinually expanding as researchers describe new species and study the behaviors of these animals. Amphibians evolved as models for a variety of developmental and physiological

Dorcas P. O'Rourke

2007-01-01

127

Infectious disease and amphibian population declines  

Microsoft Academic Search

A series of recent papers have impli- cated pathogens and parasites in amphibian population declines. Here, we review evidence on the link between infectious disease and amphibian population declines. We conclude that available data provide the clearest link for the fungal disease amphibian chytridiomycosis, although other pathogens are also implicated. We suggest additional experimental and observa- tional data that need

Peter Daszak; Andrew A. Cunningham; Alex D. Hyatt

2003-01-01

128

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

129

Advanced Metamorphosis Based on Bounded Space-time Blending  

Microsoft Academic Search

We further develop a new approach to shape metamorphosis using bounded blending operations in space-time. The key steps of the metamorphosis algorithm are: dimension increase by converting two input kD shapes into half-cylinders in (k+1)D space-time, applying bounded blending union with added material to the half-cylinders, and making cross-sections for getting intermediate shapes under the transformation. This approach is extended

Galina Pasko; Alexander A. Pasko; M. Ikeda; Tosiyasu L. Kunii

2004-01-01

130

Vijendravarma et al: Experimental evolution of critical size 1 Chronic malnutrition favours smaller critical size for metamorphosis  

E-print Network

critical size for metamorphosis initiation in Drosophila melanogaster Roshan K. Vijendravarma, Sunitha, life history, trade- offs, starvation resistance Abstract Critical size at which metamorphosis of holometabolous insects: the critical size at which metamorphosis is initiated. Although experimentally measured

Alvarez, Nadir

131

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

132

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...

133

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. PMID:14667332

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

2003-01-01

134

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. PMID:22163349

Miller, Debra; Gray, Matthew; Storfer, Andrew

2011-01-01

135

Amphibian ranavirus transmission and persistence  

E-print Network

Amphibian ranavirus transmission and persistence Jesse Brunner With an emphasis on ecological & Owens 2002 " ATV Brunner et al. 2005 " FV3 Pearman et al. 2004, Hoverman et al. 2010, Warne et al or Cophixalus ornatus adults (Cullen & Owen 2002) #12;Routes of transmission: direct contact Brunner et al

Gray, Matthew

136

Ecotoxicology of Amphibians and Reptiles  

USGS Publications Warehouse

For many years, ecological research on amphibians and reptiles has lagged behind that of other vertebrates such as fishes, birds, and mammals, despite the known importance of these animals in their environments. The lack of study has been particularly acute in the he area of ecotoxicology where the number of published scientific papers is a fraction of that found for the other vertebrate classes. Recently, scientists have become aware of severe crises among amphibian populations, including unexplained and sudden extinctions, worldwide declines, and hideous malformations. In many of these instances, contaminants have been listed as probable contributors. Data on the effects of contaminants on reptiles are so depauperate that even the most elementary interpretations are difficult. This state-of-the-science review and synthesis of amphibian and reptile ecotoxicology demonstrates the inter-relationships among distribution, ecology, physiology, and contaminant exposure, and interprets these topics as they pertain to comparative toxicity, population declines, malformations, and risk assessment . In this way, the book identifies and serves as a basis for the most pressing research needs in the coming years. The editors have invited 27 other internationally respected experts to examine the state of existing data in specific areas, interpret it in light of current problems, and identify research gaps and needs. Through its emphasis on recent research, extensive reviews and synthesis, Ecotoxicology of Amphibians and Reptiles will remain a definitive reference work well into the new century.

2000-01-01

137

Acute toxicity tests and meta-analysis identify gaps in tropical ecotoxicology for amphibians.  

PubMed

Amphibian populations are declining worldwide, particularly in tropical regions where amphibian diversity is highest. Pollutants, including agricultural pesticides, have been identified as a potential contributor to decline, yet toxicological studies of tropical amphibians are very rare. The present study assesses toxic effects on amphibians of 10 commonly used commercial pesticides in tropical agriculture using 2 approaches. First, the authors conducted 8-d toxicity assays with formulations of each pesticide using individually reared red-eyed tree frog (Agalychnis callidryas) tadpoles. Second, they conducted a review of available data for the lethal concentration to kill 50% of test animals from the US Environmental Protection Agency's ECOTOX database to allow comparison with their findings. Lethal concentration estimates from the assays ranged over several orders of magnitude. The nematicides terbufos and ethoprophos and the fungicide chlorothalonil were very highly toxic, with evident effects within an order of magnitude of environmental concentrations. Acute toxicity assays and meta-analysis show that nematicides and fungicides are generally more toxic than herbicides yet receive far less research attention than less toxic herbicides. Given that the tropics have a high diversity of amphibians, the findings emphasize the need for research into the effects of commonly used pesticides in tropical countries and should help guide future ecotoxicological research in tropical regions. PMID:24934557

Ghose, Sonia L; Donnelly, Maureen A; Kerby, Jacob; Whitfield, Steven M

2014-09-01

138

Induction of Larval Metamorphosis of the Coral Acropora millepora by Tetrabromopyrrole Isolated from a Pseudoalteromonas Bacterium  

PubMed Central

The induction of larval attachment and metamorphosis of benthic marine invertebrates is widely considered to rely on habitat specific cues. While microbial biofilms on marine hard substrates have received considerable attention as specific signals for a wide and phylogenetically diverse array of marine invertebrates, the presumed chemical settlement signals produced by the bacteria have to date not been characterized. Here we isolated and fully characterized the first chemical signal from bacteria that induced larval metamorphosis of acroporid coral larvae (Acropora millepora). The metamorphic cue was identified as tetrabromopyrrole (TBP) in four bacterial Pseudoalteromonas strains among a culture library of 225 isolates obtained from the crustose coralline algae Neogoniolithon fosliei and Hydrolithon onkodes. Coral planulae transformed into fully developed polyps within 6 h, but only a small proportion of these polyps attached to the substratum. The biofilm cell density of the four bacterial strains had no influence on the ratio of attached vs. non-attached polyps. Larval bioassays with ethanolic extracts of the bacterial isolates, as well as synthetic TBP resulted in consistent responses of coral planulae to various doses of TBP. The lowest bacterial density of one of the Pseudoalteromonas strains which induced metamorphosis was 7,000 cells mm?2 in laboratory assays, which is on the order of 0.1 –1% of the total numbers of bacteria typically found on such surfaces. These results, in which an actual cue from bacteria has been characterized for the first time, contribute significantly towards understanding the complex process of acroporid coral larval settlement mediated through epibiotic microbial biofilms on crustose coralline algae. PMID:21559509

Tebben, Jan; Tapiolas, Dianne M.; Motti, Cherie A.; Abrego, David; Negri, Andrew P.; Blackall, Linda L.; Steinberg, Peter D.; Harder, Tilmann

2011-01-01

139

Problems utilizing an enzyme sensitive site assay for photorepair of exogenous DNA with cell-free  

E-print Network

-B (UVB) damage repair ability of seven Ontario amphibian spe- cies using an enzyme sensitive siteNOTE Problems utilizing an enzyme sensitive site assay for photorepair of exogenous DNA with cell-free extracts made from amphibian embryos M. Alex Smith Abstract: Attempts were made to assay the ultraviolet

Smith, M. Alex

140

On the Metamorphosis of Vandermonde's Identity Don Rawlings and Lawrence Sze  

E-print Network

On the Metamorphosis of Vandermonde's Identity Don Rawlings and Lawrence Sze Math Department, the Vandermonde matrix is most certainly destined for fame. Which brings us back to our question of metamorphosis

Sze, Lawrence

141

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. PMID:24610865

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

2014-06-01

142

Induction of larval metamorphosis in the snail Ilyanassa.  

PubMed

The marine gastropod Ilyanassa obsoleta is a long-standing and very useful model for studies of embryonic development. It is an especially important model for spiralian development, and for studies of asymmetric cell division. The embryos are amenable to classic embryological manipulation techniques as well as a growing number of molecular approaches. Ilyanassa is also an important model for studies of metamorphosis, the ecology of parasitism, the effects of environmental contaminants on morphology and sexual function, and comparative neurobiology. Ilyanassa adults are readily obtainable and easy to keep in the laboratory, and they can produce high-quality embryos nearly year-round in the laboratory. After hatching from capsules, larval Ilyanassa can be maintained in culture, feeding on single-celled algae. The larvae will become competent to undergo metamorphosis after approximately 3 wk in culture. Metamorphosis can be induced artificially by treating with either the neurotransmitter serotonin or the nitric oxide synthase inhibitor 7-nitroindazole. Both of these reagents have been shown to induce metamorphosis in >75% of larvae within 48 h. This protocol describes the induction of metamorphosis in snail larvae. PMID:20147127

Gharbiah, Maey; Cooley, James; Leise, Esther M; Nakamoto, Ayaki; Rabinowitz, Jeremy S; Lambert, J David; Nagy, Lisa M

2009-04-01

143

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. PMID:16818245

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

144

Conserved repressive function of Kruppel homolog 1 on insect metamorphosis in  

E-print Network

Conserved repressive function of Kru¨ppel homolog 1 on insect metamorphosis in hemimetabolous´tim de la Barceloneta 37, 08003 Barcelona, Spain. Insect metamorphosis is regulated by ecdysteroids species. I nsect metamorphosis has fascinated mankind since the time of Aristotle, some two thousand years

Belles, Xavier

145

Short-term fluctuation in salinity promotes rapid larval development and metamorphosis in Dendraster excentricus  

E-print Network

Short-term fluctuation in salinity promotes rapid larval development and metamorphosis and metamorphosis of the sand dollar Dendraster excentricus was investigated in the laboratory. Sand dollar larvae then back to 31, induced metamorphosis with juvenile production being significantly higher than for those

George, Sophie B.

146

Larval experience and latent effects--metamorphosis is not a new beginning  

E-print Network

Larval experience and latent effects--metamorphosis is not a new beginning Jan A. Pechenik1. Such experiences may include delayed metamorphosis, short term starvation, short term salinity stress, or exposure be intuitively difficult to accept initially." (Desai and Hales 1997) Introduction Metamorphosis is a time

147

Methods for Volume Metamorphosis M. Chen, M.W. Jones and P. Townsend  

E-print Network

Methods for Volume Metamorphosis M. Chen, M.W. Jones and P. Townsend Department of Computer Science volume to another is referred to as volume metamorphosis or volume morphing. Several methods that provide of these methods are capable of produce good quality metamorphosis within an acceptable time. 1 Introduction Volume

Jones, Mark W.

148

Coupling constant metamorphosis and Nth order symmetries in classical and quantum  

E-print Network

Coupling constant metamorphosis and Nth order symmetries in classical and quantum mechanics E. G Abstract We review the fundamentals of coupling constant metamorphosis (CCM) and the St¨ackel transform of coupling constant metamorphosis [31], which enables a 1-1 in- vertible transformation between a 2nd order

Miller, Willard

149

Coupling constant metamorphosis and Nth order symmetries in classical and quantum  

E-print Network

Coupling constant metamorphosis and Nth order symmetries in classical and quantum mechanics E. G Abstract We review the fundamentals of coupling constant metamorphosis (CCM) and the StË?ackel transform results has been the StË?ackel transform [29, 30], a variant of coupling constant metamorphosis [31], which

Miller, Willard

150

Metamorphosis of a Butterfly-Associated Bacterial Tobin J. Hammer1,2  

E-print Network

Metamorphosis of a Butterfly-Associated Bacterial Community Tobin J. Hammer1,2 *, W. Owen McMillan2 simplifies and reorganizes during metamorphosis; thus, structural changes in a butterfly's bacterial studies using captive butterflies. Citation: Hammer TJ, McMillan WO, Fierer N (2014) Metamorphosis

Colorado at Boulder, University of

151

REARING OF PLAICE (PLEURONECTES PLATESSA) LARVAE TO METAMORPHOSIS USING AN ARTIFICIAL DIET  

E-print Network

REARING OF PLAICE (PLEURONECTES PLATESSA) LARVAE TO METAMORPHOSIS USING AN ARTIFICIAL DIET J. W. ADRON, A. BLAIR, AND C. B. COWEY' ABSTRACT Newly hakhed larval plaice were grown to metamorphosis using an artificial diet. The overall survival rate to metamorphosis was of the order of 20%. This compares

152

Evolution of Developmental Control Mechanism The hormonal pathway controlling cell death during metamorphosis in a  

E-print Network

metamorphosis in a hemimetabolous insect Daniel Mané-Padrós 1 , Josefa Cruz, Lluisa Vilaplana 2 , Claudia Nieva Hemimetabolous insect Blattella germanica Metamorphosis in holometabolous insects is mainly based metamorphosis, has shown that the steroid hormone 20-hydroxyecdysone (20E) signals cell death of larval tissues

Belles, Xavier

153

David Breen and Ross Whitaker, ``A Level-Set Approach for the Metamorphosis of Solid Models,''  

E-print Network

David Breen and Ross Whitaker, ``A Level-Set Approach for the Metamorphosis of Solid Models,'' IEEE-Set Approach for the Metamorphosis of Solid Models David E. Breeny Ross T. Whitakerz yComputer Graphics@cs.utah.edu October 30, 2000 #12;Abstract This paper presents a new approach to 3-D shape metamorphosis. We express

Utah, University of

154

Metamorphosis of the Mushroom Bodies; Large-Scale Rearrangements of the Neural  

E-print Network

Metamorphosis of the Mushroom Bodies; Large-Scale Rearrangements of the Neural Substrates of large-scale reorganization during metamorphosis. Extensive, though incomplete, degradation of the larval reorganization that takes place during metamorphosis. The adult Drosophila MBs are large paired neuropils

de Belle, J. Steven

155

ELSEVIER Aquaculture 148 (1997) 247-258 Hydrogen peroxide induced metamorphosis of  

E-print Network

ELSEVIER Aquaculture 148 (1997) 247-258 Hydrogen peroxide induced metamorphosis of queen conch, the current commercial inducer of queen conch (Strombus gigad metamorphosis, was examined. Exposure of larval larval metamorpho- sis. The percent metamorphosis induced by hydrogen peroxide was not significantly

Boettcher, Anne

156

FeatureBased Volume Metamorphosis Apostolos Lerios, Chase D. Garfinkle, Marc Levoy \\Lambda  

E-print Network

Feature­Based Volume Metamorphosis Apostolos Lerios, Chase D. Garfinkle, Marc Levoy \\Lambda Computer Science Department Stanford University Abstract Image metamorphosis, or image morphing pre­rendered images. In this paper we consider 3D metamorphosis applied to volume

Stanford University

157

Head Modeling from Pictures and Morphing in 3D with Image Metamorphosis based on triangulation  

E-print Network

Head Modeling from Pictures and Morphing in 3D with Image Metamorphosis based on triangulation WON with texture metamorphosis. There are various approaches to reconstruct a realistic person using a Laser animation. Other techniques for metamorphosis, or "morphing", involve the transformation between 2D images

Lee, WonSook

158

Mtamorphose des IHM et Plasticit Metamorphosis of User Interfaces and Plasticity  

E-print Network

1 Métamorphose des IHM et Plasticité Metamorphosis of User Interfaces and Plasticity Gaëlle CALVARY'usage, valeur, utilité, utilisabilité. Abstract. Ubiquitous computing has provoked a metamorphosis of User of UI metamorphosis, and then focuses on plasticity. It provides computer scientists with a problem

159

Feature-Based Volume Metamorphosis Apostolos Lerios, Chase D. Garfinkle, Marc Levoy  

E-print Network

Feature-Based Volume Metamorphosis Apostolos Lerios, Chase D. Garfinkle, Marc Levoy Computer Science Department Stanford University Abstract Image metamorphosis, or image morphing, is a popular tech pre-rendered images. In this paper we con- sider 3D metamorphosis applied to volume

Stanford University

160

What are amphibians and reptiles? Like birds and mammals, amphibians and  

E-print Network

amphibians have a complex life cycle that involves living both on land and in water. While most adult, based on their surroundings. Amphibians Amphibians include frogs, toads, newts, and salamanders. Many in your backyard are terrestrial, spending most of their life on land. Reptiles breathe only through

New Hampshire, University of

161

Interactions of an insecticide, herbicide, and natural stressors in amphibian community mesocosms  

USGS Publications Warehouse

Amphibians developing in wetlands embedded within or near agricultural lands may frequently encounter chemical mixtures. The objectives of our study were to determine the effects that post-application concentrations of an insecticide (carbaryl) and an herbicide (atrazine) have on body mass, development, and survival of two anuran species (southern leopard frog, Rana sphenocephala; American toad, Bufo americanus) and two caudate species (spotted salamander, Ambystoma maculatum; small-mouthed salamander, A. texanum) reared in outdoor cattle tank mesocosms. In one experiment, we manipulated tadpole density (low or high), carbaryl exposure (0, 3.5, 7.0 mg/L), and atrazine exposure (0 or 200 ??g/L) to test for effects on development, mass, and survival of larvae. In a second experiment, we manipulated pond hydroperiod (constant or drying), carbaryl exposure (0 or 5 mg/L), and atrazine exposure (0 or 200 ??g/L) to test for effects on mass, time, and survival to metamorphosis. Salamanders were virtually eliminated in carbaryl treatments, indicating that at realistic levels, this insecticide could cause population declines for salamanders in contaminated habitats. Carbaryl also had negative effects on toad survival. Exposure to atrazine had negative effects on body size, development, and time to metamorphosis in anuran species, which were associated with reduced chlorophyll levels. Both chemicals interacted significantly with density or hydroperiod, indicating that the environmental conditions could influence the impact of a contaminant. A significant atrazine-by-carbaryl interaction resulted in smaller and less developed spotted salamander larvae than in control ponds. Atrazine exposure, however, appeared to moderate negative effects of carbaryl for spotted salamanders. Our research suggests that important changes in the community's food web result from chemical exposure, which influence the susceptibility of amphibian species to contaminants.

Boone, M.D.; James, S.M.

2003-01-01

162

Female Sexual Arousal in Amphibians  

PubMed Central

Rather than being a static, species specific trait, reproductive behavior in female amphibians is variable within an individual during the breeding season when females are capable of reproductive activity. Changes in receptivity coincide with changes in circulating estrogen. Estrogen is highest at the point when females are ready to choose a male and lay eggs. At this time female receptivity (her probability of responding to a male vocal signal) is highest and her selectivity among conspecific calls (measured by her probability of responding to a degraded or otherwise usually unattractive male signal) is lowest. These changes occur even though females retain the ability to discriminate different acoustic characteristics of various conspecific calls. After releasing her eggs, female amphibians quickly become less receptive and more choosy in terms of their responses to male sexual advertisement signals. Male vocal signals stimulate both behavior and estrogen changes in amphibian females making mating more probable. The changes in female reproductive behavior are the same as those generally accepted as indicative of a change in female sexual arousal leading to copulation. They are situationally triggered, gated by interactions with males, and decline with the consummation of sexual reproduction with a chosen male. The changes can be triggered by either internal physiological state or by the presence of stimuli presented by males, and the same stimuli change both behavior and physiological (endocrine) state in such a way as to make acceptance of a male more likely. Thus amphibian females demonstrate many of the same general characteristics of changing female sexual state that in mammals indicate sexual arousal. PMID:20816968

Wilczynski, Walter; Lynch, Kathleen S.

2010-01-01

163

Effects of amphibian chytrid fungus exposure on American toads in the presence of an insecticide.  

PubMed

Abiotic factors such as pesticides may alter the impact of a pathogen on hosts, which could have implications for host-pathogen interactions and may explain variation in disease outbreaks in nature. In the present laboratory experiment, American toad (Anaxyrus americanus) metamorphs were exposed to the amphibian chytrid fungal pathogen Batrachochytrium dendrobatidis (Bd) and environmentally relevant concentrations of the insecticide malathion to determine whether malathion altered the effects of Bd exposure on growth and survival of toad metamorphs. Exposure to Bd significantly decreased survival over the 51 d of the experiment, suggesting that Bd could reduce recruitment into the terrestrial life stage when exposure occurs at metamorphosis. Malathion did not impact survival, but a 12-h exposure at metamorphosis significantly reduced terrestrial growth. Toads that were exposed to both Bd and malathion showed a nonsignificant trend toward the smallest growth compared with other treatments. The present study suggests that Bd may pose a threat to American toads even though population declines have not been observed for this species; in addition, the presence of both the insecticide malathion and Bd could reduce terrestrial growth, which could have implications for lifetime fitness and suggests that environmental factors could play a role in pathogen impacts in nature. Environ Toxicol Chem 2014;33:2541-2544. © 2014 SETAC. PMID:25099070

Wise, Rayona S; Rumschlag, Samantha L; Boone, Michelle D

2014-11-01

164

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...

165

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. PMID:17062167

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

166

Cultural Computing and the Self Concept: Towards Unconscious Metamorphosis  

Microsoft Academic Search

We are exploring an application for a novel direction in human- computer interaction named 'cultural computing', which aims to provide a new medium for cultural translation and unconscious metamorphosis. The main ob- jective of this project is to create an interactive experience that encourages peo- ple in Western culture to reflect on their self-concept. In Western culture the self-concept is

Tijn Kooijmans; Matthias Rauterberg

2007-01-01

167

The effects of acid precipitation on amphibians  

Microsoft Academic Search

A large number of studies conclusively demonstrate that low pH conditions have important ecological effects on amphibian communities. These effects vary developmentally and depend on complex interactions with other physical, chemical, and biological parameters. Acid sensitivity varies widely within and among species of amphibians. In spite of the importance of acidity to their reproductive success and the presence of many

Benjamin A. Pierce

1993-01-01

168

AMPHIBIANS AS BIOINDICATORS OF WETLAND CONDITION  

EPA Science Inventory

King county has over ten years of data on the distribution and abundance of amphibians in wetlands. Changes in wetland amphibian composition are being analyzed in relationship to physical changes within wetlands and surrounding land-use development and change. In addition to tes...

169

CHAPTER 5. AMPHIBIANS OF THE AFROTROPICAL REALM  

Microsoft Academic Search

Due to their permeable skin few amphibians are able to tolerate dry or salty conditions, a characteristic that has prevented most species from colonising oceanic islands. The most diverse oceanic island amphibian fauna is found in the Seychelles, an archipelago of about 115 granitic and coralline islands in the Indian Ocean, some 1,600km east of mainland Africa, and northeast of

Franco Andreone; Alan Channing; Robert Drewes; Justin Gerlach; Frank Glaw; Kim Howell; Malcolm Largen; Simon Loader; Stefan Lötters; Leslie Minter; Martin Pickersgill; Christopher Raxworthy; Mark-Oliver Rödel; Arne Schiøtz; Denis Vallan; Miguel Vences

170

Amphibian commerce and the threat of pathogen  

E-print Network

(pathogen pollution) · Possible implications of wildlife trade ­ Declines and extinctions ­ Disruption of historical relationshipsrelationships · 1.48 billion live animals imported by US since 2000 ­ 92 amphibians ­ Worldwide amphibian declines and extinctions · RV Ranaviruses· RV Ranaviruses ­ Affect

Gray, Matthew

171

Antipredator pheromones in amphibians: a review  

Microsoft Academic Search

Specific chemosignals (pheromones) have an important role in the antipredator behaviour in amphib- ians and other vertebrates. However, relatively little is known about the occurrence of chemical alarm cues just in amphibians. The site of chemosignals perception is vomeronasal system. The presence of the vomeronasal system in aquatic amphibians indicates that it did not arise as an adaptation to terrestrial

J. RAJCHARD

2006-01-01

172

AMPHIBIAN DECLINES AND UV RADIAnON  

E-print Network

AMPHIBIAN DECLINES AND UV RADIAnON In a letter to BioScience (45: 307). Lawrence Licht criticized our work on amphibians and ultraviolet (UV: radiation (Blaustein et aI. 1994a) Licht's criticisms, un. warranted assumptions and failun to appreciate the power of field ex. periments led him

Blaustein, Andrew R.

173

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. PMID:24535989

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

2014-01-01

174

Why Amphibians Are More Sensitive than Mammals to Xenobiotics  

Microsoft Academic Search

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

Angelo Quaranta; Vito Bellantuono; Giuseppe Cassano; Claudio Lippe

2009-01-01

175

Captive Breeding, Reintroduction, and the Conservation of Amphibians  

Microsoft Academic Search

The global amphibian crisis has resulted in renewed interest in captive breeding as a conservation tool for amphibians. Although captive breeding and reintroduction are controversial management actions, amphibians possess a number of attributes that make them potentially good models for such programs. We re- viewed the extent and effectiveness of captive breeding and reintroduction programs for amphibians through an analysis

RICHARD A. GRIFFITHS; LISSETTE PAVAJEAU

2008-01-01

176

First Evidence of Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) and Ranavirus in Hong Kong Amphibian Trade  

PubMed Central

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

177

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

178

Urea and amphibian water economy.  

PubMed

Accumulation of urea in the body fluids enables some amphibians to tolerate high ambient salinities (Bufo viridis, Xenopus laevis, Rana cancrivora, Ambystoma tigrinum, Batrachoseps spp.) or to estivate in soil with low water potentials (Scaphiopus spp.). These species are assumed not only to accumulate urea produced in the normal metabolism, but to synthesize urea in response to water shortage. Re-examination of the data did not support the view of an osmoregulatory urea synthesis. Increased urea synthesis on exposure to high salinities in X. laevis, R. cancrivora and Batrachoseps spp. seemed to reflect reactions to an adverse environment. It is suggested that in amphibians, solute concentration in the plasma and rate of excretion of urea are coordinated so that at a certain plasma concentration, urea is excreted at the same rate at which it is produced. The higher the level of urea in the body fluids at balance between production and excretion, the higher the tolerance of the species of low external water potentials. The mechanisms that integrate the relationship between plasma solute concentration and handling of urea by the kidneys are not known. PMID:9172374

Jørgensen, C B

1997-06-01

179

Sperm storage in caecilian amphibians  

PubMed Central

Background Female sperm storage has evolved independently multiple times among vertebrates to control reproduction in response to the environment. In internally fertilising amphibians, female salamanders store sperm in cloacal spermathecae, whereas among anurans sperm storage in oviducts is known only in tailed frogs. Facilitated through extensive field sampling following historical observations we tested for sperm storing structures in the female urogenital tract of fossorial, tropical caecilian amphibians. Findings In the oviparous Ichthyophis cf. kohtaoensis, aggregated sperm were present in a distinct region of the posterior oviduct but not in the cloaca in six out of seven vitellogenic females prior to oviposition. Spermatozoa were found most abundantly between the mucosal folds. In relation to the reproductive status decreased amounts of sperm were present in gravid females compared to pre-ovulatory females. Sperm were absent in females past oviposition. Conclusions Our findings indicate short-term oviductal sperm storage in the oviparous Ichthyophis cf. kohtaoensis. We assume that in female caecilians exhibiting high levels of parental investment sperm storage has evolved in order to optimally coordinate reproductive events and to increase fitness. PMID:22672478

2012-01-01

180

The first antimicrobial peptide from sea amphibian.  

PubMed

The crab-eating frog, Rana cancrivora, is one of only a handful of amphibians worldwide that tolerates saline waters. It typically inhabits brackish water of mangrove forests of Southeast Asia. A large amount of antimicrobial peptides belonging to different families have been identified from skins of amphibians inhabiting freshwater. No antimicrobial peptide from sea amphibians has been reported. In this paper, we firstly reported the antimicrobial peptide and its cDNA cloning from skin secretions of the crab-eating frog R. cancrivora. The antimicrobial peptide was named cancrin with an amino acid sequence of GSAQPYKQLHKVVNWDPYG. By BLAST search, cancrin had no significant similarity to any known peptides. The cDNA encoding cancrin was cloned from the cDNA library of the skin of R. cancrivora. The cancrin precursor is composed of 68 amino acid residues including a signal peptide, acidic spacer peptide, which are similar to other antimicrobial peptide precursors from Ranid amphibians and mature cancrin. The overall structure is similar to other amphibian antimicrobial peptide precursors although mature cancrin is different from known peptides. The current results reported a new family of amphibian antimicrobial peptide and the first antimicrobial peptide from sea amphibian. PMID:17707909

Lu, Yi; Ma, Yufang; Wang, Xu; Liang, Jianguo; Zhang, Chongxin; Zhang, Keyun; Lin, Guoqing; Lai, Ren

2008-02-01

181

Checklist of Amphibian Species and Identification Guide  

NSDL National Science Digital Library

The US Geological Survey's Northern Prairie Wildlife Research Center has provided this online guide for identification of amphibians in North America north of Mexico. Checklists of all known amphibian species in North America north of Mexico are arranged both by family and species name, and by scientific name only. Many of the listed species are accompanied by photos, descriptions, and range maps. Since most of the information is accessible by scientific name, the site is best used by those users with some background knowledge of amphibians.

1997-01-01

182

Pathogenesis, diagnosis, and treatment of amphibian chytridiomycosis.  

PubMed

Chytridiomycosis, caused by the chytridiomycete fungus, Batrachochytrium dendrobatidis, is an important pathogen of amphibians in captivity and is a major concern for global conservation of amphibians. The organism infects keratinized epithelial cells of amphibian skin and causes disease and mortality by interfering with important skin functions, especially electrolyte balance. Primary treatments are with antifungal medications applied in a topical bath solution, and itraconazole is the most commonly used agent, although several different options are available. Supportive treatment of the clinically ill patient is necessary for success, with particular attention to electrolyte therapy. PMID:24018031

Baitchman, Eric J; Pessier, Allan P

2013-09-01

183

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

184

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.

185

Metamorphosis of Hydractinia echinata —natural versus artificial induction and developmental plasticity  

Microsoft Academic Search

Many marine invertebrates reproduce through a larval stage. The settlement and metamorphosis of most of the species are synchronised\\u000a and induced by environmental organisms, mainly bacteria. The hydrozoan Hydractinia echinata has become a model organism for metamorphosis of marine invertebrates. In this species, bacteria, e.g. Pseudoalteromonas espejiana, are the natural inducers of metamorphosis. Like in other species of marine invertebrates,

Stefanie Seipp; Jürgen Schmich; Tina Kehrwald; Thomas Leitz

2007-01-01

186

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. PMID:23036161

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

2012-01-01

187

Helminth and leech community structure in tadpoles and caudatan larvae of two amphibian species from Western Nebraska.  

PubMed

Currently no comparative studies exist on helminth and leech community structure among sympatric anuran tadpoles and salamander larvae. During June-August 2007-2009, we examined 50 bullfrog tadpoles, Rana catesbeiana , 50 barred tiger salamander larvae, Ambystoma mavortium , and 3 species of snails from Nevens Pond, Keith County, Nebraska for helminth and leech infections. The helminth and leech compound community of this larval amphibian assemblage consisted of at least 7 species, 4 in bullfrog tadpoles and 4 in barred tiger salamander larvae. Bullfrog tadpoles were infected with 2 species of nematodes ( Gyrinicola batrachiensis and Spiroxys sp.) and 2 types of metacercariae ( Telorchis sp. and echinostomatids), whereas barred tiger salamander larva were infected with 1 species of leech ( Placobdella picta ), 2 species of adult trematodes ( Telorchis corti and Halipegus sp.), and 1 species of an unidentified metacercaria. The component community of bullfrog tadpoles was dominated by helminths acquired through active penetration, or incidentally ingested through respiratory currents, or both, whereas the component community of larval salamanders was dominated by helminths acquired through ingestion of intermediate hosts (?² ?=? 3,455.00, P < 0.00001). Differences in amphibian larval developmental time (2-3 yr for bullfrog tadpoles versus 2-5 mo for salamander larvae), the ephemeral nature of intermediate hosts in Nevens Pond, and the ability of bullfrog tadpole to eliminate echinostome infections had significant effects on mean helminth species richness among amphibian species and years (t ?=? 12.31, P < 0.0001; t ?=? 2.09, P ?=? 0.04). Differences in herbivorous and carnivorous diet and time to metamorphosis among bullfrog tadpoles and barred tiger salamander larvae were important factors in structuring helminth communities among the larval stages of these 2 sympatric amphibian species, whereas size was important in structuring helminth and leech communities in larval salamanders, but not in bullfrog tadpoles. PMID:22059380

Rhoden, Heather R; Bolek, Matthew G

2012-04-01

188

Time and size at metamorphosis related to adult fitness in Ambystoma talpoideum  

SciTech Connect

The relationships among timing of metamorphosis, size at metamorphosis, and traits related to adult fitness were studied for 8 yr in the salamander Ambystoma talpoideum at a temporary pond. Among years, the modal time of metamorphosis and mean body size at metamorphosis were positively correlated with the date the pond dried. In years that the pond dried late, one group of larvae metamorphosed well before the pond dried, whereas the other group metamorphosed just before pond drying. Mean body size of late-metamorphosing individuals was not greater than that of individuals metamorphosing early. Early-metamorphosing males and females were larger at first and second reproduction than were late-metamorphosing individuals. Independent of timing of metamorphosis, larger juveniles at metamorphosis were also larger adults at first reproduction. Age at first reproduction for males was not associated with timing of or size at metamorphosis but large early-metamorphosing females reproduced at a younger age than did small early-metamorphosing females. Neither time of metamorphosis nor size at metamorphosis was associated with survival to first reproduction. These results demonstrate a direct relationship between phenotypic variation generated in the larval stage and adult traits closely associated with an individual's fitness.

Semlitsch, R.D.; Scott, D.E.; Pechmann, J.H.K.

1988-02-01

189

Amphibian responses to photoinduced toxicity of PAHs  

SciTech Connect

Amphibians are essential components of many ecosystems, yet little information exists on their sensitivity to environmental stressors. Recent evidence shows amphibian diversity is declining. Others have suggested this decline is a result of increasing ultraviolet (UV) light levels. Polycyclic aromatic hydrocarbons (PAHs) are widespread pollutants in the aquatic environment and their toxicity is increased in the presence of UV light. Embryos of two frogs (Rana pipiens and Xenopus laevis) were exposed to a PAH, fluoranthene, to evaluate amphibian responses to this common contaminant in the presence of sunlight. Hatching rate and development were measured in field and laboratory exposures at multiple concentrations and varying UV intensities. Hatching rate was relatively unaffected, while newly hatched larvae were sensitive to low (ug/L) concentrations. Response was related to both PAH concentration and UV intensity. Results suggest that PAH contamination in the aquatic environment may contribute to declines in amphibian populations.

Hatch, A.C.; Burton, G.A. Jr. [Wright State Univ., Dayton, OH (United States). Biological Sciences Dept.

1995-12-31

190

Amphibians and Reptiles of Los Alamos County  

SciTech Connect

Recent studies have shown that amphibians and reptiles are good indicators of environmental health. They live in terrestrial and aquatic environments and are often the first animals to be affected by environmental change. This publication provides baseline information about amphibians and reptiles that are present on the Pajarito Plateau. Ten years of data collection and observations by researchers at Los Alamos National Laboratory, the University of New Mexico, the New Mexico Department of Game and Fish, and hobbyists are represented.

Teralene S. Foxx; Timothy K. Haarmann; David C. Keller

1999-10-01

191

Heavy metals alter the survival, growth, metamorphosis, and antipredatory behavior of Columbia spotted frog (Rana luteiventris) tadpoles.  

PubMed

Amphibian populations appear to be declining around the world. Although there is no single cause, one factor may be pollution from heavy metals. As a result of mining in the Silver Valley of Idaho, heavy metals have been released into habitats containing many species of sensitive organisms, including spotted frogs (Rana luteiventris). While the gross extent of pollution has been well documented, the more subtle behavioral effects of heavy metals such as lead, zinc, and cadmium are less well studied. We tested the effects of heavy metals on the short-term survival (LC50) of spotted frog tadpoles. Compared to single metals, metals presented together were toxic at lower doses. We also raised the tadpoles in outdoor mini-ecosystems containing either a single heavy metal or soil from an EPA Superfund site in the Silver Valley known to be composed of numerous heavy metals. Exposure to Silver Valley soil resulted in delayed metamorphosis. We tested the ability of metal-exposed tadpoles to detect and respond to chemical cues emanating from predacious rainbow trout. We found that high levels of Silver Valley soil, medium levels of zinc, and medium and high levels of lead resulted in a decreased fright response. Low levels of cadmium, zinc, and lead did not cause a significant effect, but low levels of soil did result in a decreased fright response. Heavy metals may alter interactions between tadpoles and their predators. PMID:9732476

Lefcort, H; Meguire, R A; Wilson, L H; Ettinger, W F

1998-10-01

192

The chemistry of poisons in amphibian skin.  

PubMed Central

Poisons are common in nature, where they often serve the organism in chemical defense. Such poisons either are produced de novo or are sequestered from dietary sources or symbiotic organisms. Among vertebrates, amphibians are notable for the wide range of noxious agents that are contained in granular skin glands. These compounds include amines, peptides, proteins, steroids, and both water-soluble and lipid-soluble alkaloids. With the exception of the alkaloids, most seem to be produced de novo by the amphibian. The skin of amphibians contains many structural classes of alkaloids previously unknown in nature. These include the batrachotoxins, which have recently been discovered to also occur in skin and feathers of a bird, the histrionicotoxins, the gephyrotoxins, the decahydroquinolines, the pumiliotoxins and homopumiliotoxins, epibatidine, and the samandarines. Some amphibian skin alkaloids are clearly sequestered from the diet, which consists mainly of small arthropods. These include pyrrolizidine and indolizidine alkaloids from ants, tricyclic coccinellines from beetles, and pyrrolizidine oximes, presumably from millipedes. The sources of other alkaloids in amphibian skin, including the batrachotoxins, the decahydroquinolines, the histrionicotoxins, the pumiliotoxins, and epibatidine, are unknown. While it is possible that these are produced de novo or by symbiotic microorganisms, it appears more likely that they are sequestered by the amphibians from as yet unknown dietary sources. PMID:7816854

Daly, J W

1995-01-01

193

The effects of the amphibian chytrid fungus, insecticide exposure, and temperature on larval anuran development and survival.  

PubMed

Chytridiomycosis, a disease caused by Batrachochytrium dendrobatidis (Bd), has been implicated as a cause of amphibian declines. Susceptibility may be influenced by environmental factors that suppress the immune response. The authors conducted a laboratory study to examine the effect of temperature, insecticide exposure, and Bd exposure during larval anuran development. The authors examined the consequences of exposure to Bd, an insecticide (carbaryl or malathion), and static or fluctuating temperature (15?°C, 20?°C, 25?°C, or 15?°C to 25?°C 72-h flux) on larval development through metamorphosis of the Pacific treefrog (Pseudacris regilla). High and fluctuating temperature had negative effects on survival in the presence of Bd. Insecticides inhibited the effects of Bd; time to tail resorption of Pacific treefrogs decreased when tadpoles were exposed to carbaryl. The present study indicates that abiotic factors may play a role in the host-pathogen interactions in this system. Environ Toxicol Chem 2014;33:2545-2550. © 2014 SETAC. PMID:25098758

Rumschlag, Samantha L; Boone, Michelle D; Fellers, Gary

2014-11-01

194

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

195

Widespread occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in the southeastern USA  

USGS Publications Warehouse

From 1999 to 2006, we sampled >1200 amphibians for the fungal pathogen Batrachochytnum dendrobatidis (Bd) at 30 sites in the southeastern USA. Using histological techniques or PCR assays, we detected chytrid infection in 10 species of aquatic-breeding amphibians in 6 states. The prevalence of chytrid infection was 17.8% for samples of postmetamorphic amphibians examined using skin swab-PCR assays (n = 202 samples from 12 species at 4 sites). In this subset of samples, anurans had a much higher prevalence of infection than caudates (39.2% vs. 5.5%, respectively). Mean prevalence in ranid frogs was 40.7 %. The only infected salamanders were Notophthalmus viridescens at 3 sites. We found infected amphibians from late winter through late spring and in 1 autumn sample. Although we encountered moribund or dead amphibians at 9 sites, most mortality events were not attributed to Bd. Chytridiomycosis was established as the probable cause of illness or death in fewer than 10 individuals. Our observations suggest a pattern of widespread and subclinical infections. However, because most of the sites in our study were visited only once, we cannot dismiss the possibility that chytridiomycosis is adversely affecting some populations. Furthermore, although there is no evidence of chytrid-associated declines in our region, the presence of this pathogen is cause for concern given global climate change and other stressors. Although presence-absence surveys may still be needed for some taxa, such as bufonids, we recommend that future researchers focus on potential population-level effects at sites where Bd is now known to occur. ?? Inter-Research 2008.

Rothermel, B.B.; Walls, S.C.; Mitchell, J.C.; Dodd, C.K., Jr.; Irwin, L.K.; Green, D.E.; Vazquez, V.M.; Petranka, J.W.; Stevenson, D.J.

2008-01-01

196

Induction of Metamorphosis of Larvae of the Green Sea Urchin, Strongylocentrotus droebachiensis, by Coralline Red Algae  

Microsoft Academic Search

The coralline red algae, Lithothumnion gla- ciale, Phymatolithon luevigat urn, P. rugulosum, and Cor- allinu ollicinulis, induced >85% of laboratory-reared lar- vae of Strongyloccntrotus droehachiensis to metamor- phose. Larvae must contact live L. glaciale or its spores for metamorphosis to occur: the inducer is not sensed in the water column. However, aqueous extracts of L. gfu- ciule can induce metamorphosis,

CHRISTOPHER M. PEARCE; ROBERT E. SCHEIBLING

1990-01-01

197

Interactive Shape Metamorphosis David T. Chen*, Andrei State* and David Banks  

E-print Network

of cylindrical mapping surfaces, warping the model's 2D parameter space instead of a (projected) 2D image. 3 for controlled, feature-based metamorphosis of certain types of surfaces in 3-space; it applies well-understood 2D methods to produce shape metamorphosis between 3D models in a 2D parametric space. We also

State, Andrei

198

Dendritic Reorganization of Abdominal Motoneurons Metamorphosis of the Moth, Manduca sexta' during  

Microsoft Academic Search

During metamorphosis in the hawkmoth Manduca sexfa, muscles of the abdominal body wall undergo a reorganiza- tion. Many die at the end of larval life and are replaced in the adult by newly generated muscles. We have identified sev- eral of the motoneurons innervating these muscles and fol- lowed them through metamorphosis. The morphology of lar- val motoneurons is correlated

R. B. LEVINE; J. W. TRUMAN

199

THE JOURNAL OF VISUALIZATON AND COMPUTER ANIMATION, VOL. 8: 131146 (1997) Metamorphosis of Cylinder-like Objects  

E-print Network

THE JOURNAL OF VISUALIZATON AND COMPUTER ANIMATION, VOL. 8: 131­146 (1997) Metamorphosis the metamorphosis metaphor. The shape transformation is then primarily specified by two shapes and the animation and intuitive tool that compute a metamorphosis between two objects. Such a tool is useful in both animation

Verroust-Blondet, Anne

200

J. Exp. Mar. Biol. Ecol., 1986, Vol. 91, pp. 313-319 FIELD EVIDENCE FOR DELAYED METAMORPHOSIS OF LARVAL  

E-print Network

FOR DELAYED METAMORPHOSIS OF LARVAL GASTROPODS: CREPZDULA PLANA Say, C. FORNZCATA (L.), AND BZTTZUM ALTERNATUM invertebrate larvae to delay metamorphosis to adult form and habitat is known mostly from laboratory studies metamorphosis in the plankton should be recognizable since the larvae of these species continue to increase

201

IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS, VOL. 2, NO. 4, DECEMBER 1996 337 Image Metamorphosis with  

E-print Network

Metamorphosis with Scattered Feature Constraints Seungyong Lee, George Wolberg, Kyung-Yong Chwa, and Sung Yong Shin Abstract--This paper describes an image metamorphosis technique to handle scattered feature blending. Implementation details are furnished and comparisons among various metamorphosis techniques

Wolberg, George

202

ESTIMATING AMPHIBIAN OCCUPANCY RATES IN PONDS UNDER COMPLEX SURVEY DESIGNS  

EPA Science Inventory

Monitoring the occurrence of specific amphibian species in ponds is one component of the US Geological Survey's Amphibian Monitoring and Research Initiative. Two collaborative studies were conducted in Olympic National Park and southeastern region of Oregon. The number of ponds...

203

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. PMID:24495308

2014-01-01

204

Aquatic eutrophication promotes pathogenic infection in amphibians  

PubMed Central

The widespread emergence of human and wildlife diseases has challenged ecologists to understand how large-scale agents of environmental change affect host–pathogen interactions. Accelerated eutrophication of aquatic ecosystems owing to nitrogen and phosphorus enrichment is a pervasive form of environmental change that has been implicated in the emergence of diseases through direct and indirect pathways. We provide experimental evidence linking eutrophication and disease in a multihost parasite system. The trematode parasite Ribeiroia ondatrae sequentially infects birds, snails, and amphibian larvae, frequently causing severe limb deformities and mortality. Eutrophication has been implicated in the emergence of this parasite, but definitive evidence, as well as a mechanistic understanding, have been lacking until now. We show that the effects of eutrophication cascade through the parasite life cycle to promote algal production, the density of snail hosts, and, ultimately, the intensity of infection in amphibians. Infection also negatively affected the survival of developing amphibians. Mechanistically, eutrophication promoted amphibian disease through two distinctive pathways: by increasing the density of infected snail hosts and by enhancing per-snail production of infectious parasites. Given forecasted increases in global eutrophication, amphibian extinctions, and similarities between Ribeiroia and important human and wildlife pathogens, our results have broad epidemiological and ecological significance. PMID:17893332

Johnson, Pieter T. J.; Chase, Jonathan M.; Dosch, Katherine L.; Hartson, Richard B.; Gross, Jackson A.; Larson, Don J.; Sutherland, Daniel R.; Carpenter, Stephen R.

2007-01-01

205

Particle-Antiparticle Metamorphosis of Massive Majorana Neutrinos and Gauginos  

E-print Network

Recent results on neutrinoless double beta decay, as reported by Klapdor-Kleingrothaus et al., take us for the first time into the realm of Majorana spacetime structure. However, this structure has either been treated as an afterthought to the Dirac construct; or, when it has been attended to in its own right, its physical and mathematical content was never fully unearthed. In this Letter,we undertake to remedy the existing situation. We present a detailed formalism required for the description of the non-trivial spacetime structure underlying the "nu-nubar" metamorphosis - where "nu" generically represents a massive Majorana neutrino, or a massive gaugino.

Ahluwalia, D V

2002-01-01

206

Particle-Antiparticle Metamorphosis of Massive Majorana Neutrinos and Gauginos  

E-print Network

Recent results on neutrinoless double beta decay, as reported by Klapdor-Kleingrothaus et al., take us for the first time into the realm of Majorana spacetime structure. However, this structure has either been treated as an afterthought to the Dirac construct; or, when it has been attended to in its own right, its physical and mathematical content was never fully unearthed. In this Letter,we undertake to remedy the existing situation. We present a detailed formalism required for the description of the non-trivial spacetime structure underlying the "nu-nubar" metamorphosis - where "nu" generically represents a massive Majorana neutrino, or a massive gaugino.

D. V. Ahluwalia-Khalilova

2002-04-12

207

Forecasting changes in amphibian biodiversity: aiming at a moving target  

Microsoft Academic Search

Amphibian population declines and sudden species' extinctions began to be noted at the beginning of the 1980s. Understanding the causes of the losses is hampered by our poor knowledge of the amphibian fauna in many parts of the world. Amphibian taxa are still being described at a high rate, especially in the tropics, which means that even quantifying species lost

James P. Collins; Tim Halliday

2005-01-01

208

Environmental and historical constraints on global patterns of amphibian richness  

Microsoft Academic Search

Our knowledge of the broad-scale ecology of vertebrate ectotherms remains very limited. Despite ongoing declines and sensitivity to environmental change, amphibian distributions are particularly poorly understood. We present a global analysis of contemporary environmental and historical constraints on amphibian richness, the first for an ectotherm clade at this scale. Amphibians are presumed to experience environmental constraints distinct from those of

Lauren B. Buckley; Walter Jetz

2007-01-01

209

DISTRIBUTION OF AMPHIBIANS IN TERRESTRIAL HABITAT SURROUNDING WETLANDS  

Microsoft Academic Search

Estimating the distribution of amphibians in terrestrial habitats surrounding wetlands is essential for determining how much habitat is required to maintain viable amphibian populations and how much habitat may be allocated to other land use practices. We apply univariate kernel estimation in a new manner to determine the distribution of amphibians during the non-breeding season. We summarized data from 13

Tracy A. G. Rittenhouse; Raymond D. Semlitsch

2007-01-01

210

Colonization of Restored Wetlands by Amphibians in Minnesota  

Microsoft Academic Search

Twelve wetlands (7 recently restored; 5 reference) in central and southern Minnesota were monitored during the 1998 breeding season to assess colonization of recently restored wetlands by amphibians, compare the amphibian fauna to that of reference wetlands and identify important factors influencing the probability of colonization. Eight amphibian species rapidly colonized recently restored wetlands and established breeding populations. Reference wetlands

RICHARD M. LEHTINEN; SUSAN M. GALATOWITSCH

2001-01-01

211

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

212

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

213

Status and Trends of Amphibian Declines and Extinctions Worldwide  

Microsoft Academic Search

The first global assessment of amphibians provides new context to the well-publicised phenomenon of amphibian declines. Amphibians are more threatened, and are declining more rapidly, than either birds or mammals. Although many declines are due to habitat loss and over- utilization, other, unidentified processes threaten 48% of rapidly declining species, and are driving species most quickly to extinction. Declines are

Simon N. Stuart; Janice S. Chanson; Neil A. Cox; Bruce E. Young; Ana S. L. Rodrigues; Debra L. Fischman; Robert W. Waller

2004-01-01

214

Protein tyrosine phosphatase encoded in Cotesia plutellae bracovirus suppresses a larva-to-pupa metamorphosis of the diamondback moth, Plutella xylostella.  

PubMed

Parasitization by an endoparasitoid wasp, Cotesia plutellae, inhibits a larva-to-pupa metamorphosis of the diamondback moth, Plutella xylostella. This study tested an inhibitory effect of C. plutellae bracovirus (CpBV) on the metamorphosis of P. xylostella. Parasitized P. xylostella exhibited significantly reduced prothoracic gland (PTG) development at the last instar compared to nonparasitized larvae. Expression of the ecdysone receptor (EcR) was markedly suppressed during the last instar larvae parasitized by C. plutellae. By contrast, expression of the insulin receptor (InR) significantly increased in the parasitized larvae. Microinjection of CpBV significantly inhibited the larva-to-pupa metamorphosis of nonparasitized larvae in a dose-dependent manner. Injection of CpBV also inhibited the expression of the EcR and increased the expression of the InR. Individual CpBV segments were transiently expressed in its encoded genes in nonparasitized larvae and screened to determine antimetamorphic viral gene(s). Out of 21 CpBV segments, two viral segments (CpBV-S22 and CpBV-S27) were proved to inhibit larva-to-pupa metamorphosis by transient expression assay. RNA interference of each gene encoded in the viral segments was applied to determine antimetamorphic gene(s). Protein tyrosine phosphatase, early expressed gene, and four hypothetical genes were selected to be associated with the antimetamorphic activity of CpBV. These results suggest that antimetamorphosis of P. xylostella parasitized by C. plutellae is induced by inhibiting PTG development and subsequent ecdysteroid signaling with viral factors of CpBV. PMID:23651929

Kim, Jiwan; Hepat, Rahul; Lee, Daeweon; Kim, Yonggyun

2013-09-01

215

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

216

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. PMID:23794877

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

2013-01-01

217

Design of an Amphibian Exploring Robot  

NASA Astrophysics Data System (ADS)

To design and develop an amphibian exploring robot capable of operation in constrained mine environment puts a tremendous challenge to the system developers from both scientific and engineering perspective. Very few attempts have been made to fulfil these criteria of versatility in design, communication and control. The CSIR-CMERI developed amphibian subterranean robotic explorer (SR) is capable of moving over fairly rough terrain. It can swim as well as crawl over basin floor effortlessly. It is capable of operating at a maximum depth of 10m and can swim at 1 knot. A number of field trials have been carried out for performance testing of the system to ascertain its capability in underground flooded mine tunnels. This paper presents the insight on the design of an amphibian exploring robot for mine safety and disaster mitigation with special features of low power consumption vis-a-vis high mission time.

Maity, Atanu; Majumder, Somajyoti

2014-07-01

218

[Beier 92] Thaddeus Beier and Shawn Neely, ``FeatureBased Image Metamorphosis,'' Computer Graphics, Vol. 26, No. 2 (SIGGRAPH 92), pp. 3542.  

E-print Network

7 References [Beier 92] Thaddeus Beier and Shawn Neely, ``Feature­Based Image Metamorphosis. Metamorphosis of surface shapes in 3­space. Top row: 0% and 33% versions of the David ­> Heidi metamorphosis sequence. Bottom row: 67%, and 100% versions of the David ­> Heidi metamorphosis sequence #12; 5 Figure 2b

Chen, David T.

219

Physiological, Behavioral and Maternal Factors That Contribute to Size Variation in Larval Amphibian Populations  

PubMed Central

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

220

Fluoxetine alters adult freshwater mussel behavior and larval metamorphosis.  

PubMed

We used acute and partial-lifecycle tests to examine the effects of the pharmaceutical fluoxetine on freshwater mussels (Unionida). In acute tests lasting 24-48 h, we determined median effective concentrations (EC50s) for fluoxetine with larval (glochidia viability) and juvenile (survival) life-stages of fatmucket (Lampsilis siliquoidea) and black sandshell (Ligumia recta). In a 28-d behavioral test we exposed brooding adult female wavy-rayed lampmussels (Lampsilis fasciola) to 0.37 and 29.3 ?g/L fluoxetine to determine effects on adult behavior (foot protrusion, mantle lure display and glochidia parturition). We also assessed the effects of 24-h exposure of 1 and 100 ?g/L fluoxetine on glochidia viability duration and metamorphosis success for the wavy-rayed lampmussel. Fluoxetine EC50s ranged from 62 ?g/L for juveniles (96 h) to 293 ?g/L for glochidia (24 h). In adults, statistically significant increases were observed in foot protrusion at 0.37 and 29.3 ?g/L fluoxetine and lure display rates at 29.3 ?g/L; glochidia parturition was not significantly affected at any test concentration. Twenty-four hour exposure of glochidia to fluoxetine did not affect viability duration, but likelihood of metamorphosis to the juvenile stage significantly increased with 1 and 100 ?g/L treatments. Our results demonstrated effects of fluoxetine to unionid mussels at concentrations less than previously reported and approaching concentrations measured in surface waters. PMID:23321069

Hazelton, Peter D; Cope, W Gregory; Mosher, Shad; Pandolfo, Tamara J; Belden, Jason B; Barnhart, M Christopher; Bringolf, Robert B

2013-02-15

221

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

222

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. PMID:23115204

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

2012-01-01

223

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

224

Proteomic analysis during larval development and metamorphosis of the spionid polychaete Pseudopolydora vexillosa  

PubMed Central

Background While the larval-juvenile transition (metamorphosis) in the spionid polychaete Pseudopolydora vexillosa involves gradual morphological changes and does not require substantial development of juvenile organs, the opposite occurs in the barnacle Balanus amphitrite. We hypothesized that the proteome changes during metamorphosis in the spionids are less drastic than that in the barnacles. To test this, proteomes of pre-competent larvae, competent larvae (ready to metamorphose), and juveniles of P. vexillosa were compared using 2-dimensional gel electrophoresis (2-DE), and they were then compared to those of the barnacle. Results Unlike the significant changes found during barnacle metamorphosis, proteomes of competent P. vexillosa larvae were more similar to those of their juveniles. Pre-competent larvae had significantly fewer protein spots (384 spots), while both competent larvae and juveniles expressed about 660 protein spots each. Proteins up-regulated during competence identified by MALDI-TOF/TOF analysis included a molecular chaperon (calreticulin), a signal transduction regulator (tyrosin activation protein), and a tissue-remodeling enzyme (metallopeptidase). Conclusions This was the first time to study the protein expression patterns during the metamorphosis of a marine polychaete and to compare the proteomes of marine invertebrates that have different levels of morphological changes during metamorphosis. The findings provide promising initial steps towards the development of a proteome database for marine invertebrate metamorphosis, thus deciphering the possible mechanisms underlying larval metamorphosis in non-model marine organisms. PMID:20003395

2009-01-01

225

Lethal and sublethal effects of three insecticides on two developmental stages of Xenopus laevis and comparison with other amphibians.  

PubMed

It has been suggested that Xenopus laevis is less sensitive than other amphibians to some chemicals, and therefore, that the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) may have limited use in risk assessments for other amphibians. However, comparisons are based mostly on results of FETAX, which emphasizes embryos. Larval X. laevis may be more sensitive to chemicals than embryos and may serve as a better life stage in risk assessments. The present study was conducted to determine the lethal and sublethal effects of 3 insecticides (malathion, endosulfan, and ?-cypermethrin) on X. laevis embryos and larvae and to compare toxicity of X. laevis with that of other amphibians. All 3 insecticides have different modes of action, and they caused mortality, malformations, and growth inhibition in both developmental stages. Compared with embryos, larvae were more sensitive to endosulfan and ?-cypermethrin but not to malathion. Xenopus laevis larvae had low sensitivity to endosulfan, median sensitivity to malathion, and high sensitivity to ?-cypermethrin/cypermethrin relative to other larval amphibians. Our results suggest that X. laevis larvae may generate more protective toxicity estimates in risk assessments than embryos. Xenopus laevis may have limited use in evaluating risk of organochlorine insecticides to other amphibians but may provide useful toxicity thresholds for pyrethroid and perhaps organophosphorus insecticides. PMID:23686650

Yu, Shuangying; Wages, Mike R; Cai, Qingsong; Maul, Jonathan D; Cobb, George P

2013-09-01

226

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. PMID:24624048

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

2014-01-01

227

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

228

Presence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in native amphibians exported from Madagascar.  

PubMed

The emerging infectious disease chytridiomycosis is driven by the spread of amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd), a highly virulent pathogen threatening global amphibian biodiversity. Although pandemic in distribution, previous intensive field surveys have failed to detect Bd in Madagascar, a biodiversity hotspot home to hundreds of endemic amphibian species. Due to the presence of Bd in nearby continental Africa and the ecological crisis that can be expected following establishment in Madagascar, enhanced surveillance is imperative. I sampled 565 amphibians commercially exported from Madagascar for the presence of Bd upon importation to the USA, both to assist early detection efforts and demonstrate the conservation potential of wildlife trade disease surveillance. Bd was detected in three animals via quantitative PCR: a single Heterixalus alboguttatus, Heterixalus betsileo, and Scaphiophryne spinosa. This is the first time Bd has been confirmed in amphibians from Madagascar and presents an urgent call to action. Our early identification of pathogen presence prior to widespread infection provides the necessary tools and encouragement to catalyze a swift, targeted response to isolate and eradicate Bd from Madagascar. If implemented before establishment occurs, an otherwise likely catastrophic decline in amphibian biodiversity may be prevented. PMID:24599336

Kolby, Jonathan E

2014-01-01

229

Presence of the Amphibian Chytrid Fungus Batrachochytrium dendrobatidis in Native Amphibians Exported from Madagascar  

PubMed Central

The emerging infectious disease chytridiomycosis is driven by the spread of amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd), a highly virulent pathogen threatening global amphibian biodiversity. Although pandemic in distribution, previous intensive field surveys have failed to detect Bd in Madagascar, a biodiversity hotspot home to hundreds of endemic amphibian species. Due to the presence of Bd in nearby continental Africa and the ecological crisis that can be expected following establishment in Madagascar, enhanced surveillance is imperative. I sampled 565 amphibians commercially exported from Madagascar for the presence of Bd upon importation to the USA, both to assist early detection efforts and demonstrate the conservation potential of wildlife trade disease surveillance. Bd was detected in three animals via quantitative PCR: a single Heterixalus alboguttatus, Heterixalus betsileo, and Scaphiophryne spinosa. This is the first time Bd has been confirmed in amphibians from Madagascar and presents an urgent call to action. Our early identification of pathogen presence prior to widespread infection provides the necessary tools and encouragement to catalyze a swift, targeted response to isolate and eradicate Bd from Madagascar. If implemented before establishment occurs, an otherwise likely catastrophic decline in amphibian biodiversity may be prevented. PMID:24599336

Kolby, Jonathan E.

2014-01-01

230

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

2014-01-01

231

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...

232

Explanation for missing limbs in deformed amphibians  

Microsoft Academic Search

We present evidence that the most commonly found deformities in wild-caught amphibians, those featuring missing limbs and missing limb segments, may be the result of selective predation. Here we report that predatory dragonfly nymphs can severely injure and even fully amputate developing hind limbs of anuran tadpoles. Developmental responses of the injured\\/ amputated tadpole limbs range from complete regeneration to

Brandon Ballengée

2009-01-01

233

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

234

Chemical communication in an archaic anuran amphibian  

Microsoft Academic Search

Bioacoustic signals appear to be so essential to the social communication of anuran amphibians that other sensory modalities have been largely ignored. We studied the abilities of Leiopelma hamiltoni, a species evolutionarily basal to most living anurans, to communicate by means of chemosignals. We collected frogs in the field, held them in captivity for 72 h, and then tested their

Bruce Waldman; Phillip J. Bishop

2004-01-01

235

Adding infection to injury: synergistic effects of predation and parasitism on amphibian malformations.  

PubMed

We explored the importance of interactions between parasite infection and predation in driving an emerging phenomenon of conservation importance: amphibian limb malformations. We suggest that injury resulting from intraspecific predation in combination with trematode infection contributes to the frequency and severity of malformations in salamanders. By integrating field surveys and experiments, we evaluated the individual and combined effects of conspecific attack and parasite (Ribeiroia ondatrae) infection on limb development of long-toed salamanders (Ambystoma macrodactylum). In the absence of Ribeiroia, abnormalities involved missing digits, feet, or limbs and were similar to those produced by cannibalistic attack in experimental trials. At field sites that supported Ribeiroia, malformations were dominated by extra limbs and digits. Correspondingly, laboratory exposure of larval salamanders to Ribeiroia cercariae over a 30-day period induced high frequencies of malformations, including extra digits, extra limbs, cutaneous fusion, and micromelia. However, salamander limbs exposed to both injury and infection exhibited 3-5 times more abnormalities than those exposed to either factor alone. Infection also caused significant delays in limb regeneration and time-to-metamorphosis. Taken together, these results help to explain malformation patterns observed in natural salamander populations while emphasizing the importance of interactions between parasitism and predation in driving disease. PMID:16995623

Johnson, Pieter T J; Preu, Eric R; Sutherland, Daniel R; Romansic, John M; Han, Barbara; Blaustein, Andrew R

2006-09-01

236

Is there Supernova Evidence for Dark Energy Metamorphosis ?  

E-print Network

We reconstruct the equation of state w(z) of dark energy (DE) using a recently released data set containing 172 type Ia supernovae without imposing any priors on w(z) (in contrast to previous studies). We find that dark energy evolves rapidly and metamorphoses from dust-like behaviour at high z ($w \\simeq 0$ at $z \\sim 1$) to a strongly negative equation of state at present ($w \\lleq -1$ at $z \\simeq 0$). Dark energy metamorphosis appears to be a robust phenomenon which manifests for a large variety of Sn data samples provided one does not invoke the weak energy prior $\\rho + p \\geq 0$. Invoking this prior considerably weakens the rate of growth of w(z). These results demonstrate that dark energy with an evolving equation of state provides a compelling alternative to a cosmological constant if data are analysed in a prior-free manner and the weak energy condition is not imposed by hand.

Alam, U; Saini, T D; Starobinsky, A A; Alam, Ujjaini; Sahni, Varun; Saini, Tarun Deep

2003-01-01

237

Is there Supernova Evidence for Dark Energy Metamorphosis ?  

E-print Network

We reconstruct the equation of state $w(z)$ of dark energy (DE) using a recently released data set containing 172 type Ia supernovae without assuming the prior $w(z) \\geq -1$ (in contrast to previous studies). We find that dark energy evolves rapidly and metamorphoses from dust-like behaviour at high $z$ ($w \\simeq 0$ at $z \\sim 1$) to a strongly negative equation of state at present ($w \\lleq -1$ at $z \\simeq 0$). Dark energy metamorphosis appears to be a robust phenomenon which manifests for a large variety of SNe data samples provided one does not invoke the weak energy prior $\\rho + p \\geq 0$. Invoking this prior considerably weakens the rate of growth of $w(z)$. These results demonstrate that dark energy with an evolving equation of state provides a compelling alternative to a cosmological constant if data are analysed in a prior-free manner and the weak energy condition is not imposed by hand.

Ujjaini Alam; Varun Sahni; Tarun Deep Saini; A. A. Starobinsky

2003-11-16

238

Establishing causality in the decline and deformity of amphibians: The amphibian research and monitoring initiative model  

USGS Publications Warehouse

Research to date has indicated that a range of environmental variables such as disease, parasitism, predation, competition, environmental contamination, solar ultraviolet radiation, climate change, or habitat alteration may be responsible for declining amphibian populations and the appearance of deformed organisms, yet in many cases no definitive environmental variable stands out as a causal factor. Multiple Stressors are often present in the habitat, and interactions among these can magnify injury to biota. This raises the possibility that the additive or synergistic impact of these Stressors may be the underlying cause of amphibian declines. Effective management for the restoration of amphibian populations requires the identification of causal factors contributing to their declines. A systematic approach to determine causality is especially important because initial impressions may be misleading or ambiguous. In addition, the evaluation of amphibian populations requires consideration of a broader spatial scale than commonly used in regulatory monitoring. We describe a systematic three-tiered approach to determine causality in amphibian declines and deformities. Tier 1 includes an evaluation of historic databases and extant data and would involve a desktop synopsis of the status of various stressors as well as site visits. Tier 2 studies are iterative, hypothesis driven studies beginning with general tests and continuing with analyses of increasing complexity as certain stressors are identified for further investigation. Tier 3 applies information developed in Tier 2 as predictive indicators of habitats and species at risk over broad landscape scales and provides decision support for the adaptive management of amphibian recovery. This comprehensive, tiered program could provide a mechanistic approach to identifying and addressing specific stressors responsible for amphibian declines across various landscapes.

Little, E.E.; Bridges, C.M.; Linder, G.; Boone, M.

2003-01-01

239

Palatal Metamorphosis in Basal Caecilians (Amphibia: Gymnophiona) as Evidence for Lissamphibian Monophyly  

E-print Network

; it runs anteromedially, close to the lateral edge of the para- sphenoid. At metamorphosis the maxilla from the posterior part of the pterygoid. The quadrate develops a rostrally directed quadratojugal

Reiss, John

240

Juvenile hormone metabolism in the larval-pupal metamorphosis of Manduca sexta  

E-print Network

JUVENILE HORMONE METABOLISM IN THE LARVAL-PUPAL METAMORPHOSIS OF MA/V DUCA SEXTA A Thesis by STEVEN PAUL SPARAGANA Submitted to the Graduate College of Texas ALM University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE MAY 19Q4 Major Subject: BIOLOGY JUVENILE HORMONE METABOLISM IN THE LARVAL-PUPAL METAMORPHOSIS OF MANDUCA SEXFA A Thesis by STEVEN PAUL SPARAGANA Approved as to style and content by: GOVINDAN BHASKARAN (CHAIRMAN) DAVID W. OWENS (MEMBER...

Sparagana, Steven Paul

2012-06-07

241

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

NASA Astrophysics Data System (ADS)

A pilot on-line course on amphibians was offered free to 20 educators around the United States in 1999. This course, called Helping Your Local Amphibians (HYLA), was the first of its kind on-line course for educators dealing with amphibian issues. It also used these animals as a focus to teach about the environment. The course lasted 9 weeks with some additional time for continued discussions and used various aspects of Internet technology (including a virtual conference center), media, and traditional paper-based products to complete the learning process. Five teachers were selected to attend a national amphibian summit hosted by the Center for Global Environmental Education, Hamline University, St. Paul, MN. The course was aimed primarily at upper elementary and middle school teachers, but participants included formal and nonformal educators. For the most part, educators expressed satisfaction with the course and the content, as well as the structure of the web site. For 80% of the group, this was their first Internet-based course. In addition, as part of the course, the educators were expected to take some action with their primary audiences to help local amphibian populations. This mainly took the form of surveys or habitat clean-ups. The development of the course was underwritten by grants from the National Fish and Wildlife Foundation, U.S. Fish and Wildlife Service, the Best Buy Children's Foundation, and Hamline University.

Murphy, Tony P.

2001-12-01

242

Direct and indirect effects of climate change on amphibian populations  

USGS Publications Warehouse

As part of an overall decline in biodiversity, populations of many organisms are declining and species are being lost at unprecedented rates around the world. This includes many populations and species of amphibians. Although numerous factors are affecting amphibian populations, we show potential direct and indirect effects of climate change on amphibians at the individual, population and community level. Shifts in amphibian ranges are predicted. Changes in climate may affect survival, growth, reproduction and dispersal capabilities. Moreover, climate change can alter amphibian habitats including vegetation, soil, and hydrology. Climate change can influence food availability, predator-prey relationships and competitive interactions which can alter community structure. Climate change can also alter pathogen-host dynamics and greatly influence how diseases are manifested. Changes in climate can interact with other stressors such as UV-B radiation and contaminants. The interactions among all these factors are complex and are probably driving some amphibian population declines and extinctions.

Blaustein, Andrew R.; Walls, Susan C.; Bancroft, Betsy A.; Lawler, Joshua J.; Searle, Catherine L.; Gervasi, Stephanie S.

2010-01-01

243

Pesticide Detection in Rainwater, Stemflow, and Amphibians from Agricultural Spray Drift in Southern Georgia, USA  

EPA Science Inventory

Amphibians are important sentinel environmental species since they integrate stressors from both aquatic and terrestrial ecosystems. Pesticides are well established as a significant stressor for amphibians. In order to study spray-drift contributions to amphibian habitats, pestic...

244

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.

245

Explanation for missing limbs in deformed amphibians.  

PubMed

We present evidence that the most commonly found deformities in wild-caught amphibians, those featuring missing limbs and missing limb segments, may be the result of selective predation. Here we report that predatory dragonfly nymphs can severely injure and even fully amputate developing hind limbs of anuran tadpoles. Developmental responses of the injured/amputated tadpole limbs range from complete regeneration to no regeneration, with intermediate conditions represented by various idiosyncratic limb deformities, depending mainly on the developmental stage of the tadpole at the time of injury/amputation. These findings were reinforced by experimental amputations of anuran tadpole hind limbs that resulted in similar deformities. Our studies suggest that selective predation by dragonfly nymphs and other aquatic predators may play a significant role in the most common kinds of limb deformities found in natural populations of amphibians. PMID:19507246

Ballengée, Brandon; Sessions, Stanley K

2009-11-15

246

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. PMID:22649387

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

2011-01-01

247

Distribution of amphibians in terrestrial habitat surrounding wetlands  

Microsoft Academic Search

Estimating the distribution of amphibians in terrestrial habitats surrounding wetlands is essential for determining how much\\u000a habitat is required to maintain viable amphibian populations and how much habitat may be allocated to other land use practices.\\u000a We apply univariate kernel estimation in a new manner to determine the distribution of amphibians during the non-breeding\\u000a season. We summarized data from 13

Tracy A. G. Rittenhouse; Raymond D. Semlitsch

2007-01-01

248

Ranavirus outbreaks in amphibian populations of northern Idaho  

USGS Publications Warehouse

Ranavirus outbreaks, caused by pathogens in the genus Ranavirus (Family Iridoviridae), were the largest single cause of reported amphibian mass mortality events in the United States from 1996–2001 (Green et al. 2002). Mortality events associated with ranaviruses have been documented on five continents and throughout the latitudes and elevations where amphibians occur (Gray et al. 2009). However, the threat of ranaviruses to amphibian and reptile populations in specific regions is still largely unknown (Chinchar 2002; Gray et al. 2009).

Russell, Danelle M.; Goldberg, Caren S.; Sprague, Laura; Waits, Lisette P.; Green, D. Earl; Schuler, Krysten L.; Rosenblum, Erica Bree

2011-01-01

249

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. PMID:10603206

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

1999-01-01

250

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. PMID:21197215

Song, Fengyu; Li, Bingbing

2010-01-01

251

Restoring ponds for amphibians: a success story  

Microsoft Academic Search

Large-scale restoration of quality habitats is often considered essential for the recovery of threatened pond-breeding amphibians\\u000a but only a few successful cases are documented, so far. We describe a landscape-scale restoration project targeted at two\\u000a declining species—the crested newt (Triturus cristatus Laur.) and the common spadefoot toad (Pelobates fuscus Wagler)—in six protected areas in southern and southeastern Estonia. The ponds

R. Rannap; A. Lõhmus; L. Briggs

2009-01-01

252

Restoring ponds for amphibians: a success story  

Microsoft Academic Search

\\u000a Large-scale restoration of quality habitats is often considered essential for the recovery of threatened pond-breeding amphibians\\u000a but only a few successful cases are documented, so far. We describe a landscape-scale restoration project targeted at two\\u000a declining species—the crested newt (Triturus cristatus Laur.) and the common spadefoot toad (Pelobates fuscus Wagler)—in six protected areas in southern and southeastern Estonia. The ponds

R. Rannap; A. Lõhmus; L. Briggs

253

New Mexico Species List : Reptiles and Amphibians  

NSDL National Science Digital Library

The New Mexico Department of Game and Fish compiled this extensive list of reptiles and amphibians for New Mexico and Arizona. Organized alphabetically by common name (with scientific name in parenthesis), each hyperlinked name connects the viewer to further details (taxonomy, status, life history, distribution, habitat information, food habits, environmental associations, management practices, and references) via the Biota Information System Of New Mexico (BISON). Researchers will appreciate the extent and clarity of information in this database.

254

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

255

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

256

Analgesia in Amphibians: Preclinical Studies and Clinical Applications  

PubMed Central

SYNOPSIS Preclinical studies of analgesia in amphibians or recommendations for clinical use of analgesics in amphibian species are extremely limited. This article briefly reviews the issues surrounding the use of analgesics in amphibians starting with common definitions of pain and analgesia when applied to non-human animals. Nociceptive and endogenous opioid systems in amphibians are reviewed and results of preclinical research on opioid and non-opioid analgesics summarized. Recommended opioid and non-opioid analgesics are summarized and practical recommendations made for their clinical use. PMID:21074701

Stevens, Craig W.

2010-01-01

257

Amphibian Populations in the Terrestrial Environment: Is There Evidence of Declines of Terrestrial Forest Amphibians in Northwestern California?  

Microsoft Academic Search

Amphibian declines have been documented worldwide; however the vast majority are species associated with aquatic habitats. Information on the status and trends of terrestrial amphibians is almost entirely lacking. Here we use data collected across a 12-yr period (sampling from 1984-86 and from 1993-95) to address the question of whether evidence exists for declines among terrestrial amphibians in northwestern California

HARTWELL H. WELSH JR.; Gary M. Fellers; Amy J. Lind

2007-01-01

258

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

NASA Astrophysics Data System (ADS)

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 km of the Ain River, beyond the mountain front, are situated in a valley of outwash deposits where the floodplain is 0.2 to 1.2 km wide. A complex mosaic of floodplain landscape units has developed. Maps dating back to 1766 and six sets of aerial photographs dated between 1945 and 1991 were used to document changes in channel pattern. Aerial photos and field surveys were used to compile maps of landscape units based on dominant vegetation life-forms, species, and substrate. Six maps dated between 1945 and 1991 were digitized in ARC/INFO and an overlay was generated to determine the changes in landscape units as related to channel disturbance. Change from a braided to a single-thread meandering channel probably took place in the period 1930-1950. The process of river entrenchment has occurred throughout the Holocene but has accelerated in the present century due to shortening of the river course, construction of lateral embankments, and vegetation encroachment following reservoir construction and cessation of wood-cutting and grazing. The increase in horizontal channel stability coupled with channel entrenchment have decreased floodplain disturbance and lowered the water table by approximately one meter. Pioneer and disturbance-dependent landscape units have experienced a more terrestrial-like succession to an alluvial forest. Abandoned channels have also been replaced by alluvial forests. On poorly drained soils, shrub-swamp communities of willow and hydrophytic herbaceous plants have been replaced by mixed forests of ash, alder, black poplar, and oak. On well drained alluvial soils, ash and oak dominated hardwood forests have declined in favor of mesophytic stands of black poplar. All types of vegetation, but particularly dry grasslands-shrublands, have been cleared for mines, campgrounds, agriculture, and other types of development. Using several measures, landscape diversity decreased between 1945 and 1991.

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

1995-09-01

259

From metamorphosis to maturity in complex life cycles: equal performance of different juvenile life history pathways.  

PubMed

Performance in one stage of a complex life cycle may affect performance in the subsequent stage. Animals that start a new stage at a smaller size than conspecifics may either always remain smaller or they may be able to "catch up" through plasticity, usually elevated growth rates. We study how size at and date of metamorphosis affected subsequent performance in the terrestrial juvenile stage and lifetime fitness of spadefoot toads (Pelobates fuscus). We analyzed capture-recapture data of > 3000 individuals sampled during nine years with mark-recapture models to estimate first-year juvenile survival probabilities and age-specific first-time breeding probabilities of toads, followed by model selection to assess whether these probabilities were correlated with size at and date of metamorphosis. Males attained maturity after two years, whereas females reached maturity 2-4 years after metamorphosis. Age at maturity was weakly correlated with metamorphic traits. In both sexes, first-year juvenile survival depended positively on date of metamorphosis and, in males, also negatively on size at metamorphosis. In males, toads that metamorphosed early at a small size had the highest probability to reach maturity. However, because very few toadlets metamorphosed early, the vast majority of male metamorphs had a very similar probability to reach maturity. A matrix projection model constructed for females showed that different juvenile life history pathways resulted in similar lifetime fitness. We found that the effects of date of and size at metamorphosis on different juvenile traits cancelled each other out such that toads that were small or large at metamorphosis had equal performance. Because the costs and benefits of juvenile life history pathways may also depend on population fluctuations, ample phenotypic variation in life history traits may be maintained. PMID:22624219

Schmidt, Benedikt R; Hödl, Walter; Schaub, Michael

2012-03-01

260

Vestibular Lesion-Induced Developmental Plasticity in Spinal Locomotor Networks during Xenopus laevis Metamorphosis  

PubMed Central

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, Andre; Simmers, John; Le Ray, Didier

2013-01-01

261

Conceptual Design for the Amphibian Research and Monitoring Initiative (ARMI)  

NASA Astrophysics Data System (ADS)

In 2000, the President of the United States (US) and Congress directed Department of Interior (DOI) agencies to develop a program for monitoring trends in amphibian populations on DOI lands and to conduct research into causes of declines. The U.S. Geological Survey (USGS) was given lead responsibility for planning and implementing the Amphibian Research and Monitoring Initiative (ARMI) in cooperation with the National Park Service (NPS), Fish and Wildlife Service, and Bureau of Land Management. The program objectives are to (1) establish a network for monitoring the status and distribution of amphibian species on DOI lands; (2) identify and monitor environmental conditions known to affect amphibian populations; (3) conduct research on causes of amphibian population change and malformations; and (4) provide information to resource managers, policy makers, and the public in support of amphibian conservation. The ARMI program will integrate research efforts of USGS, other Federal, and non-federal herpetologists, hydrologists, and geographers across the Nation. ARMI will conduct a small number (~20) of intensive research efforts (for example, studies linking amphibian population changes to hydrologic conditions) and a larger number (~50) of more generalized inventory and monitoring studies encompassing broader areas such as NPS units. ARMI will coordinate with and try to augment other amphibian inventory studies such as the National Amphibian Atlas and the North American Amphibian Monitoring Program. ARMI will develop and test protocols for the standardized collection of amphibian data and provide a centrally managed database designed to simplify data entry, retrieval, and analysis. ARMI pilot projects are underway at locations across the US.

Battaglin, W. A.; Langtimm, C. A.; Adams, M. J.; Gallant, A. L.; James, D. L.

2001-12-01

262

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

263

Functional Divergence of the miRNA Transcriptome at the Onset of Drosophila Metamorphosis.  

PubMed

MicroRNAs (miRNAs) are endogenous RNA molecules that regulate gene expression posttranscriptionally. To date, the emergence of miRNAs and their patterns of sequence evolution have been analyzed in great detail. However, the extent to which miRNA expression levels have evolved over time, the role different evolutionary forces play in shaping these changes, and whether this variation in miRNA expression can reveal the interplay between miRNAs and mRNAs remain poorly understood. This is especially true for miRNA expressed during key developmental transitions. Here, we assayed miRNA expression levels immediately before (?18BPF [18 h before puparium formation]) and after (PF) the increase in the hormone ecdysone responsible for triggering metamorphosis. We did so in four strains of Drosophila melanogaster and two closely related species. In contrast to their sequence conservation, approximately 25% of miRNAs analyzed showed significant within-species variation in male expression levels at ?18BPF and/or PF. Additionally, approximately 33% showed modifications in their pattern of expression bias between developmental timepoints. A separate analysis of the ?18BPF and PF stages revealed that changes in miRNA abundance accumulate linearly over evolutionary time at PF but not at ?18BPF. Importantly, ?18BPF-enriched miRNAs showed the greatest variation in expression levels both within and between species, so are the less likely to evolve under stabilizing selection. Functional attributes, such as expression ubiquity, appeared more tightly associated with lower levels of miRNA expression polymorphism at PF than at ?18BPF. Furthermore, ?18BPF- and PF-enriched miRNAs showed opposite patterns of covariation in expression with mRNAs, which denoted the type of regulatory relationship between miRNAs and mRNAs. Collectively, our results show contrasting patterns of functional divergence associated with miRNA expression levels during Drosophila ontogeny. PMID:24951729

Yeh, Shu-Dan; von Grotthuss, Marcin; Gandasetiawan, Kania A; Jayasekera, Suvini; Xia, Xiao-Qin; Chan, Carolus; Jayaswal, Vivek; Ranz, José M

2014-10-01

264

Pore metamorphosis during liquid phase sintering in microgravity  

NASA Astrophysics Data System (ADS)

This dissertation documents the pore metamorphosis in microgravity liquid phase sintered Co-Cu and Fe-Cu samples that have been successfully conducted on several sounding rocket flights, Space Shuttle missions and aboard the Mir Station. Pore filling and coarsening were found in most samples while pore breakup was also found in low liquid volume samples. Pores showed bifurcated behaviors based on their liquid volume fractions. These behaviors resulted from particle rearrangement, particle growth and volume diffusion that associated with interfacial energy differences, instabilities, and grain coarsening along the interface between phases. The mechanisms for pore breakup, pore coarsening and pore filling are discussed. An initiation mechanism induced by grain growth, capillary force and other weak forces is proposed and the results from theoretical analysis and CFD numerical simulation for pore breakup are presented. The microstructure evolutions of Co-Cu and Fe-Cu samples and the grain growth measurements that associated with pore morphological changes are also documented in this dissertation.

He, Yubin

265

Amphibian Pathogen Batrachochytrium dendrobatidis Is Inhibited by the Cutaneous Bacteria of Amphibian Species  

E-print Network

and salamander species (Rollins-Smith et al., 2005). Among species exposed to B. dendrobatidis, some populations, Duke University, Box 90338, Durham, NC 27708 Abstract: Population declines of amphibian species in many the skins of the salamander P. cinereus and members of seven genera isolated from the salamander H. scutatum

James, Timothy

266

Canopy closure and amphibian diversity in forested wetlands  

Microsoft Academic Search

The crowns of trees and shrubs often overtop temporary wetlands in forested regions. By shading pond basins, canopy can dramatically change the conditions experienced by residents such as amphibians. In this study, we estimated the presence of 8 amphibian species across 17 temporary wetlands at the Yale–Myers Forest in northeastern Connecticut, USA. In addition, we quantified the light environment using

David K. Skelly; M. Anders Halverson; L. Kealoha Freidenburg; Mark C. Urban

2005-01-01

267

Amphibians as a model for the study of endocrine disruptors  

Microsoft Academic Search

Evidence shows that environmental compounds can interfere with the endocrine systems of wildlife and humans. The main sink of such substances, called endocrine disruptors (EDs), which are mainly of anthropogenic origin, is surface water; thus, aquatic vertebrates such as fishes and amphibians are most endangered. Despite numerous reports on EDs in fishes, information about EDs in amphibians is scarce, and

Werner Kloas

2002-01-01

268

[Helminths of amphibians of the Fergana valley of Uzbekistan].  

PubMed

Species diversity and some ecological peculiarities of helminthes parasitizing amphibians in the Fergana Valley of Uzbekistan have been investigated. In 652 examined specimens of amphibians (Bufo viridis--237, Rana ridibunda--415 specimens), have been found 32 helminth species belonging to 26 genera of 12 families. PMID:15069882

Ikramov, E F; Azimov, D A

2004-01-01

269

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

270

The effect of fish and aquatic habitat complexity on amphibians  

Microsoft Academic Search

Fish introductions are considered one of the most widespread anthropogenic threats to aquatic ecosystems. Their negative impact on native amphibian communities has received increasing attention in recent years. We investi- gated the relationship between the introduced fish, emergent vegetation cover and native amphibians in man-made ponds generated by regulation and dam building along the Tarnava Mare Valley (Romania) during the

Tibor Hartel; Szilard Nemes; Dan Coga; Kinga Ollerer; Oliver Schweiger; Cosmin-Ioan Moga

2006-01-01

271

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...

272

Incorporating Amphibian Malformations into Inquiry-Based Learning  

ERIC Educational Resources Information Center

Amphibians, a class of vertebrates consisting of frogs and toads, salamanders, and caecilians, are excellent organisms for middle school science students to study because of their ecological significance. Because they exchange oxygen and carbon dioxide through their skin, amphibians absorb any chemicals or substances present in their immediate…

Talley, Brooke L.

2007-01-01

273

Amphibians and Reptiles from Paramakatoi and Kato, Guyana  

USGS Publications Warehouse

We report the herpetofauna of two neighboring upland locations in west-central Guyana. Twenty amphibian and 24 reptile species were collected. Only 40% of amphibians and 12.5% of reptiles were collected in both locations. This is one of the few collections made at upland (750–800 m) locations in the Guiana Shield.

MacCulloch, Ross D.; Reynolds, Robert P.

2012-01-01

274

BIOACCUMULATION AND MATERNAL TRANSFER OF MERCURY AND SELENIUM IN AMPHIBIANS  

E-print Network

BIOACCUMULATION AND MATERNAL TRANSFER OF MERCURY AND SELENIUM IN AMPHIBIANS CHRISTINE M. BERGERON toxicity to other wildlife, and complex relationships with other elements, such as selenium (Se. 2010;29:989­997. # 2010 SETAC Keywords--Amphibians Mercury Methylmercury Selenium Maternal transfer

Hopkins, William A.

275

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

276

Global amphibian declines: a perspective from the Caribbean  

Microsoft Academic Search

Recent concern over the possibility of a global decline in amphibians prompted this assessment of the West Indian species. At the species level, the West Indian amphibian fauna (156 species, all frogs and toads) has not undergone a general decline, and no species is known to be extinct. However, one Puerto Rican species (Eleutherodactylus karlschmidti) has not been seen in

S. Blair Hedges

1993-01-01

277

INTRODUCTION Hensen's node, the amniote equivalent of the amphibian  

E-print Network

INTRODUCTION Hensen's node, the amniote equivalent of the amphibian `Spemann's organizer counterpart (the dorsal lip of the blasto- pore), Hensen's node can be characterized by a well-defined set's organizer in amphibians is Hensen's node, which lies at the tip of the primitive streak during gastru

Stern, Claudio

278

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

279

Amphibian Species Diversity Exceeds that of Zoologische Staatssammiung Miinchen  

E-print Network

their number was estimated to be about 4675 in the middle of 1995 (Hutterer 1995). These estimates prompted us a synthesis of the data provided in Amphibian Species of the World (Frost 1985) and the additions and correc and Reeder (1993) as updated by Hutterer (1995). Annual rates of amphibian species descriptions have been ex

280

Asymmetries in amphibians: A review of morphology and behaviour  

Microsoft Academic Search

Morphological and behavioural asymmetries in amphibians are reviewed. Among the characteristics considered are: (1) the asymmetry of the shoulder girdle (epicoracoid overlap); (2) the distribution of the left and right variants of its structure in amphibian populations; (3) asymmetry in the position of the spiracle(s); (4) asymmetric order of forelimb emergence from opercular chambers in tadpoles; and (5) preferential forelimb

Yegor B. Malashichev

2002-01-01

281

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

282

Effects of chemical cues on larval survival, settlement and metamorphosis of abalone Haliotis asinina  

NASA Astrophysics Data System (ADS)

Low larval survival, poor settlement, and abnormal metamorphosis are major problems in seed production of donkey-ear abalone Haliotis asinina. We examined the effects of chemical cues including epinephrine, nor-epinephrine, and serotonin on larval survival, settlement, and metamorphosis in order to determine the possibility of using these chemicals to induce the problems. The results show that epinephrine could enhance metamorphosis rate at 10-6 mol/L only but higher concentrations (10-3-10-4 mol/L); and nor-epinephrine could inhibit the performance significantly, and serotonin could increase significantly the performance at a wide-range concentration (10-3-10-6 mol/L). Treatment with serotonin at 10-5 mol/L for 72 hours resulted in the highest settlement rate (42.2%) and survival rate (49.3%), while at 10-4 mol/L for 72 hours resulted in the highest metamorphosis rate (38.8%). Therefore, serotonin may be used as a fast metamorphosis inducer in abalone culture.

Wang, Xiaobing; Bai, Yang; Huang, Bo

2010-11-01

283

Partners in amphibian and reptile conservation 2013 annual report  

USGS Publications Warehouse

Partners in Amphibian and Reptile Conservation (PARC) was established in 1999 to address the widespread declines, extinctions, and range reductions of amphibians and reptiles, with a focus on conservation of taxa and habitats in North America. Amphibians and reptiles are affected by a broad range of human activities, both as incidental effects of habitat alteration and direct effect from overexploitation; these animals are also challenged by the perception that amphibians and reptiles are either dangerous or of little environmental or economic value. However, PARC members understand these taxa are important parts of our natural an cultural heritage and they serve important roles in ecosystems throughout the world. With many amphibians and reptiles classified as threatened with extinction, conservation of these animals has never been more important.

Edited by Conrad, Paulette M.; Weir, Linda A.; Nanjappa, Priya

2014-01-01

284

Amphibians Are Not Ready for Roundup ®  

Microsoft Academic Search

\\u000a The herbicide glyphosate, sold under a variety of commercial names including Roundup\\u000a ®\\u000a and Vision\\u000a ®\\u000a , has long been viewed as an environmentally friendly herbicide. In the 1990s, however, after nearly 20 years of use, the\\u000a first tests were conducted on the herbicide’s effects on amphibians in Australia. The researchers found that the herbicide\\u000a was moderately toxic to Australian

Rick A. Relyea

285

Cloning and stage-specific expression of CK-M1 gene during metamorphosis of Japanese flounder, Paralichthys olivaceus  

NASA Astrophysics Data System (ADS)

The symmetrical body of flatfish larvae changes dramatically into an asymmetrical form after metamorphosis. The molecular mechanisms responsible for this change are poorly understood. As an initial step to clarify these mechanisms, we used representational difference analysis of cDNA for the identification of genes active during metamorphosis in the Japanese flounder, Paralichthys olicaceus. One of the up-regulated genes was identified as creatine kinase muscle type 1 (CK-M1). Sequence analysis of CK-M1 revealed that it spanned 1 708 bp and encoded a protein of 382 amino acids. The overall amino acid sequence of the CK-M1 was highly conserved with those of other organisms. CK-M1 was expressed in adult fish tissues, including skeletal muscle, intestine and gill. Whole mount in-situ hybridization showed that the enhanced expression of CK-M1 expanded from the head to the whole body of larvae as metamorphosis progressed. Quantitative analysis revealed stage-specific high expression of CK-M1 during metamorphosis. The expression level of CK-M1 increased initially and peaked at metamorphosis, decreased afterward, and finally returned to the pre-metamorphosis level. This stage-specific expression pattern suggested strongly that CK-M1 was related to metamorphosis in the Japanese flounder. Its specific role in metamorphosis requires further study.

Chen, Yanjie; Zhang, Quanqi; Qi, Jie; Wang, Zhigang; Wang, Xubo; Sun, Yeying; Zhong, Qiwang; Li, Shuo; Li, Chunmei

2010-05-01

286

Juvenile Hormone Prevents 20-Hydroxyecdysone-induced Metamorphosis by Regulating the Phosphorylation of a Newly Identified Broad Protein.  

PubMed

The steroid hormone 20-hydroxyecdysone (20E) initiates insect molting and metamorphosis. By contrast, juvenile hormone (JH) prevents metamorphosis. However, the mechanism by which JH inhibits metamorphosis remains unclear. In this study, we propose that JH induces the phosphorylation of Broad isoform Z7 (BrZ7), a newly identified protein, to inhibit 20E-mediated metamorphosis in the lepidopteran insect Helicoverpa armigera. The knockdown of BrZ7 in larvae inhibited metamorphosis by repressing the expression of the 20E response gene. BrZ7 was weakly expressed and phosphorylated during larval growth but highly expressed and non-phosphorylated during metamorphosis. JH regulated the rapid phosphorylation of BrZ7 via a G-protein-coupled receptor-, phospholipase C-, and protein kinase C-triggered pathway. The phosphorylated BrZ7 bound to the 5'-regulatory region of calponin to regulate its expression in the JH pathway. Exogenous JH induced BrZ7 phosphorylation to prevent metamorphosis by suppressing 20E-related gene transcription. JH promoted non-phosphorylated calponin interacting with ultraspiracle protein to activate the JH pathway and antagonize the 20E pathway. This study reveals one of the possible mechanisms by which JH counteracts 20E-regulated metamorphosis by inducing the phosphorylation of BrZ7. PMID:25096576

Cai, Mei-Juan; Liu, Wen; Pei, Xu-Yang; Li, Xiang-Ru; He, Hong-Juan; Wang, Jin-Xing; Zhao, Xiao-Fan

2014-09-19

287

Broad-complex functions in postembryonic development of the cockroach Blattella germanica shed new light on the evolution of insect metamorphosis  

E-print Network

light on the evolution of insect metamorphosis Jia-Hsin Huang 1 , Jesus Lozano, Xavier Belles Institute metamorphosis Juvenile hormone Ecdysone Evolution of holometaboly Drosophila Tribolium Background: Insect metamorphosis proceeds in two modes: hemimetaboly, gradual change along the life cycle; and holometaboly, abrupt

Belles, Xavier

288

The Consequences of Metamorphosis on Salamander (Ambystoma) Locomotor Performance Author(s): H. Bradley Shaffer, C. C. Austin, R. B. Huey  

E-print Network

The Consequences of Metamorphosis on Salamander (Ambystoma) Locomotor Performance Author(s): H in morphology and ecology of salamanders during metamorphosis affect many aspects of their life history. Wequantify the effects of metamorphosis on burst speed and endurance capacity on a large sample of

Shaffer, H. Bradley

289

Image Metamorphosis Using Snakes and FreeForm Deformations SeungYong Lee y , KyungYong Chwa, Sung Yong Shin  

E-print Network

Image Metamorphosis Using Snakes and Free­Form Deformations Seung­Yong Lee y , Kyung­Yong Chwa transition functions to control geometry and color blending. Keywords: Image metamorphosis, morphing, snakes, multilevel free­form deformation, multilevel B­spline interpolation. 1. Introduction Image metamorphosis

Wolberg, George

290

/ www.sciencexpress.org / 31 July 2008 / Page 1 / 10.1126/science.1158712 During Drosophila metamorphosis, most larval cells die.  

E-print Network

metamorphosis, most larval cells die. Pupal and adult tissues form from imaginal cells, tissue- specific and fate mapping of single, identified cells shows that tracheal system remodeling at metamorphosis or all of larval life, then proliferate and differentiate into pupal and adult tissues at metamorphosis

Krasnow, Mark A.

291

Technical Report No. UIUCDCS-R-2004-2439 (Engr. UILU-ENG-2004-1739) Video Metamorphosis Using Dense Flow Fields  

E-print Network

Technical Report No. UIUCDCS-R-2004-2439 (Engr. UILU-ENG-2004-1739) Video Metamorphosis Using Dense-Champaign {yyz,qingwu1}@uiuc.edu Abstract--- Metamorphosis is generally known as the continu- ous evolution algorithm. Experimental results show that our approach to video metamorphosis can produce superior results

Yu, Yizhou

292

Larval metamorphosis of the mussel Mytilus galloprovincialis Lamarck, 1819 in response to neurotransmitter blockers and tetraethylammonium.  

PubMed

The metamorphic response of pediveliger larvae of Mytilus galloprovincialis to the neurotransmitter blockers chlorpromazine, amitriptyline, rauwolscine, idazoxan, atenolol and butoxamine, and to tetraethylammonium chloride (TEA) was investigated through a series of bioassays. Chlorpromazine, amitriptyline and idazoxin inhibited larval metamorphosis induced by 10?? M epinephrine. The concentration that inhibited metamorphosis by 50% (IC??) for chlorpromazine and amitriptyline was 1.6 x 10?? M and 6.6 x 10?? M, respectively. Idazoxan was less effective with an IC?? of 4.4 x 10¹³ M. Moreover, these three inhibitors showed no toxicity at any of the concentrations tested. The larval metamorphic response to K+ was not inhibited by 10?³ M tetraethylammonium chloride after 96 h. Thus, the neurotransmitter blockers chlorpromazine and amitriptyline are inhibitors of larval metamorphosis, and will be useful tools for antifouling studies. PMID:21271410

Yang, Jin-Long; Li, Yi-Feng; Bao, Wei-Yang; Satuito, Cyril Glenn; Kitamura, Hitoshi

2011-02-01

293

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. PMID:22412378

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

294

The first gene-encoded amphibian neurotoxin.  

PubMed

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 microM. 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 microM. Anntoxin was distributed in skin, brain, stomach, and liver with a concentration of 25, 7, 3, and 2 microg/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. PMID:19535333

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

2009-08-14

295

Metamorphosis of an identified serotonergic neuron in the Drosophila olfactory system  

E-print Network

ral ssBioMed CentNeural Development Open AcceResearch article Metamorphosis of an identified serotonergic neuron in the Drosophila olfactory system Bidisha Roy1, Ajeet P Singh2, Chetak Shetty2, Varun Chaudhary1, Annemarie North3, Matthias Landgraf... in the embryo, has a relatively simple pattern in the larval stages and is remodeled dur- ing pupation to give rise to an elaborate adult pattern. We chart the changes occurring during metamorphosis and examine which events are due to the autonomous action...

Roy, Bidisha; Singh, Ajeet P; Shetty, Chetak; Chaudhary, Varun; North, Annemarie; Landgraf, Matthias; Vijay Raghavan, K; Rodrigues, Veronica

2007-10-24

296

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. PMID:24941262

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

2014-01-01

297

Cool temperatures reduce antifungal activity of symbiotic bacteria of threatened amphibians--implications for disease management and patterns of decline.  

PubMed

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. PMID:24941262

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

2014-01-01

298

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 PMID:10504145

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

1999-01-01

299

Amphibian skin may select for rare environmental microbes.  

PubMed

Host-microbe symbioses rely on the successful transmission or acquisition of symbionts in each new generation. Amphibians host a diverse cutaneous microbiota, and many of these symbionts appear to be mutualistic and may limit infection by the chytrid fungus, Batrachochytrium dendrobatidis, which has caused global amphibian population declines and extinctions in recent decades. Using bar-coded 454 pyrosequencing of the 16S rRNA gene, we addressed the question of symbiont transmission by examining variation in amphibian skin microbiota across species and sites and in direct relation to environmental microbes. Although acquisition of environmental microbes occurs in some host-symbiont systems, this has not been extensively examined in free-living vertebrate-microbe symbioses. Juvenile bullfrogs (Rana catesbeiana), adult red-spotted newts (Notophthalmus viridescens), pond water and pond substrate were sampled at a single pond to examine host-specificity and potential environmental transmission of microbiota. To assess population level variation in skin microbiota, adult newts from two additional sites were also sampled. Cohabiting bullfrogs and newts had distinct microbial communities, as did newts across the three sites. The microbial communities of amphibians and the environment were distinct; there was very little overlap in the amphibians' core microbes and the most abundant environmental microbes, and the relative abundances of OTUs that were shared by amphibians and the environment were inversely related. These results suggest that, in a host species-specific manner, amphibian skin may select for microbes that are generally in low abundance in the environment. PMID:24858782

Walke, Jenifer B; Becker, Matthew H; Loftus, Stephen C; House, Leanna L; Cormier, Guy; Jensen, Roderick V; Belden, Lisa K

2014-11-01

300

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 ...

301

Metamorphosis of dentistry. Update on alternative delivery systems.  

PubMed

In 1985, Americans spent $27.8 billion for dental care. Patients paid $18 billion out-of-pocket, while private health insurance paid about $9.2 billion. Public programs paid approximately $600 million primarily through Medicaid. Commercial insurance carriers have increased their market share to more than 80 million subscribers, or more than 70 per cent of the total market. Dental service corporations and Blue Cross/Blue Shield plans cover more than 30 million subscribers, while independent plans have policies with more than 6 million customers. Dentistry today is a big business, and Big Business wants to make it their business. What makes health care vastly different from the manufacture and sale of microwaves, furniture and clothing, or the production and serving of fast foods is that the provider is in a unique relationship with the consumer/patient and will always have a large measure of control for this reason. Receiving dental care is not the same as purchasing a new pair of tennis shoes, but good business practices from other business arenas can make it possible for greater numbers of people to have greater access to it. Over the past 25 years a metamorphosis of dentistry has been generated by a rather constant interplay between the various involved parties to obtain a position of least financial risk. Insurance carriers and/or administrative intermediaries want the risk placed on the dentist, employers want the administrators to take it, and dentists want employers, administrators, or patients to assume it. The future will see the gradual evolvement of equitable plans dividing the risk among the four principle parties. Plans are being put in place today that already reflect this. A viable alternative delivery system means: Dental care providers who have the knowledge and incentive to perform quality care; administrators willing to share some of the risk; and employers and consumers who are sophisticated and realistic in their demands in today's marketplace. All these factions are currently interacting to create the new dental picture we see today--and will see in the future. PMID:3422193

Tekavec, M M

1988-01-01

302

cDNA clone and expression analysis of ?-Tropomyosin during Japanese flounder (Paralichthys olivaceus) metamorphosis.  

PubMed

Tropomyosin (TM) plays a critical role in skeletal and cardiac muscle development and function. To assess the functional significance of ?-TM in Japanese flounder (Paralichthys olivaceus) development and metamorphosis, cDNA from Japanese flounder was cloned and ?-TM mRNA measured during development and metamorphosis. The full-length cDNA is 1 191 bp, including a 5'-untranslated region of 114 bp, a 3'-UTR of 222 bp, and an open reading frame of 855 bp encoding a polypeptide of 284 amino acids. Real-time quantitative PCR revealed that ?-TM mRNA is initially expressed in unfertilized ovum, indicating the ?-TM gene is maternal. Relatively low mRNA levels were observed in different embryonic stages. A higher level of ?-TM mRNA was detected 3 days post hatching (dph), while the highest level was measured at 29 dph (metamorphic climax) after which it declined towards the end of metamorphosis. The expression of ?-TM mRNA was up-regulated in thyroid hormone-treated larvae at 36 dph, but there was no marked difference at other stages when compared to control animals. After thiourea treatment, the expression of ?-TM mRNA declined slightly. These data provide basic information that can be utilized in further studies into the role of ?-TM in P. olivaceus development and metamorphosis. PMID:25017750

Zhang, Hong-Mei; Su, Yan-Fang; Shi, Zhi-Yi; Fu, Yuan-Shuai

2014-07-18

303

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

304

Energetics of metamorphosis in Drosophila melanogaster Allison B. Merkey, Carrie K. Wong 1  

E-print Network

Energetics of metamorphosis in Drosophila melanogaster Allison B. Merkey, Carrie K. Wong 1 in the fruitfly, Drosophila melanogaster. Metabolic rates decreased rapidly in the first 24 h and remained low in revised form 18 July 2011 Accepted 19 July 2011 Available online 24 July 2011 Keywords: Drosophila

Ahmad, Sajjad

305

PATTERNS OF NATURAL SELECTION ON SIZE AT METAMORPHOSIS IN WATER FROGS  

Microsoft Academic Search

Abstract Strategies for optimal metamorphosis are key adaptations in organisms with complex life cycles, and the components,of the larval growth environment,causing variation in this trait are well studied empirically and theoretically. However, when relating these findings to a broader evolutionary or ecological context, usually the following assumptions are made: (1) size at metamorphosispositively relates to future fitness, and (2) the

Res Altwegg; Heinz-Ulrich Reyer

2003-01-01

306

Intraspecific variation of temperature-induced effects on metamorphosis in the pool frog (Rana lessonae)  

Microsoft Academic Search

Understanding the factors that affect the process of metamorphosis in species with complex life cycles, and in particular their variation within and among populations, has been rarely explored until recently. We examined the effects of temperature environment on several metamorphic characteristics in three populations of the pool frog (Rana lessonae Camerano, 1882) by rearing individuals at two temperature environments (20

German Orizaola; Anssi Laurila

2009-01-01

307

Caring about Strangers: A Lingisian Reading of Kafka's "Metamorphosis"  

ERIC Educational Resources Information Center

This article explores a significant question, implicit in Kafka's novel "Metamorphosis," explicitly asked by Rorty: "Can I care about a stranger?" Alphonso Lingis's view is adopted to overcome a mainstream belief that there is a distinction between my community and the stranger's community, or us community and…

Hung, Ruyu

2013-01-01

308

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....

309

The predominance of polyunsaturated fatty acids in the butterfly Morpho peleides before and after metamorphosis  

Microsoft Academic Search

We hypothesized that the polyunsaturated fatty acids of the butterfly were probably derived from the diet and that there might be a great loss of body fat during metamorphosis. To substantiate these hypotheses, we ana- lyzed the fatty acid composition and content of the diet, the larva, and the butterfly Morpho peleides. Both the diet and the tissues of the

Yingming Wang; Don S. Lin; Linda Bolewicz; William E. Connor

2005-01-01

310

EVIDENCE FOR ACCELERATED METAMORPHOSIS IN BULLFROG (RANA CATESBIEANA) TADPOLES IN AN EPHEMERAL POND  

EPA Science Inventory

It has been widely accepted that time to metamorphosis for non-native bullfrog tadpoles in the Pacific Northwest is greater than one year. We surveyed 22 ponds within the EE Wilson Reserve (Benton County, Oregon) for bullfrog tadpoles and metamorphs from April through September, ...

311

Metamorphosis enhances the effects of metal exposure on the mayfly, Centroptilum triangulifer  

USGS Publications Warehouse

The response of larval aquatic insects to stressors such as metals is used to assess the ecological condition of streams worldwide. However, nearly all larval insects metamorphose from aquatic larvae to winged adults, and recent surveys indicate that adults may be a more sensitive indicator of stream metal toxicity than larvae. One hypothesis to explain this pattern is that insects exposed to elevated metal in their larval stages have a reduced ability to successfully complete metamorphosis. To test this hypothesis we exposed late-instar larvae of the mayfly, Centroptilum triangulifer, to an aqueous Zn gradient (32–476 ?g/L) in the laboratory. After 6 days of exposure, when metamorphosis began, larval survival was unaffected by zinc. However, Zn reduced wingpad development at concentrations above 139 ?g/L. In contrast, emergence of subimagos and imagos tended to decline with any increase in Zn. At Zn concentrations below 105 ?g/L (hardness-adjusted aquatic life criterion), survival between the wingpad and subimago stages declined 5-fold across the Zn gradient. These results support the hypothesis that metamorphosis may be a survival bottleneck, particularly in contaminated streams. Thus, death during metamorphosis may be a key mechanism explaining how stream metal contamination can impact terrestrial communities by reducing aquatic insect emergence.

Wesner, Jeff S.; Kraus, Johanna M.; Schmidt, Travis S.; Walters, David M.; Clements, William H.

2014-01-01

312

Metamorphosis enhances the effects of metal exposure on the mayfly, Centroptilum triangulifer.  

PubMed

The response of larval aquatic insects to stressors such as metals is used to assess the ecological condition of streams worldwide. However, nearly all larval insects metamorphose from aquatic larvae to winged adults, and recent surveys indicate that adults may be a more sensitive indicator of stream metal toxicity than larvae. One hypothesis to explain this pattern is that insects exposed to elevated metal in their larval stages have a reduced ability to successfully complete metamorphosis. To test this hypothesis we exposed late-instar larvae of the mayfly, Centroptilum triangulifer, to an aqueous Zn gradient (32-476 ?g/L) in the laboratory. After 6 days of exposure, when metamorphosis began, larval survival was unaffected by zinc. However, Zn reduced wingpad development at concentrations above 139 ?g/L. In contrast, emergence of subimagos and imagos tended to decline with any increase in Zn. At Zn concentrations below 105 ?g/L (hardness-adjusted aquatic life criterion), survival between the wingpad and subimago stages declined 5-fold across the Zn gradient. These results support the hypothesis that metamorphosis may be a survival bottleneck, particularly in contaminated streams. Thus, death during metamorphosis may be a key mechanism explaining how stream metal contamination can impact terrestrial communities by reducing aquatic insect emergence. PMID:25093980

Wesner, J S; Kraus, J M; Schmidt, T S; Walters, D M; Clements, W H

2014-09-01

313

FOOD OF YOUNG ATLANTIC MENHADEN, BREVOORTIA TYRANNUS, IN RELATION TO METAMORPHOSIS  

Microsoft Academic Search

To rear this species in captivity required knowledge of the kinds of organisms it ate. Larvae ate zooplankton (copepods), but prejuveniles and juveniles fed chiefly on phytoplankton. There were similarities as well as dif­ ferences between the alimentary tract contents of the fish and the composition of the plankton community. Changes in food habits during metamorphosis were Laboratory research is

FRED C. JUNEI; FRANK T. CARLSON

314

Development of adult thoracic leg muscles during metamorphosis of the hawk moth Manduca sexta  

Microsoft Academic Search

During metamorphosis, the larval thoracic legs of the hawk moth Manduca sexta are replaced by a new set of adult legs. The larval leg motoneurons persist to innervate new adult muscles, and the motor terminals remain within the developing adult legs. Here we describe the fate of the larval leg muscles and the origin of new muscles within the adult

C. Consoulas; M. Anezaki; R. B. Levine

1997-01-01

315

Losses of Cd, Hg, and Zn During Metamorphosis in the Beetle Tenebrio Molitor (Coleoptera: Tenebrionidae)  

Microsoft Academic Search

Insects occur in great numbers and are important for the transport of metals between trophic levels in food webs. Therefore, processes influencing metal concentrations in insects are important for the distribution of metals in ecosystems. The metamorphosis in holometabolous insects is of importance for metal concentrations. During this process some organs undergo an extensive breakdown as new organs are built

L. Lindqvist; M. Block

1997-01-01

316

Excretion of cadmium during moulting and metamorphosis in Tenebrio molitor (Coleoptera; Tenebrionidae)  

Microsoft Academic Search

The effects of moulting between instars and metamorphosis on the contents of Cd were studied in T. molitor larvae both by following the radioactive tracer 108Cd ingested on one occasion and by analysing Cd concentration in larvae and newly hatched adults with a continuous intake of Cd. Larvae were given 109Cd in one meal. Contents of 109Cd were then determined

Lars Lindqvist; Mats Block

1995-01-01

317

Tooth morphology in Triturus vulgaris meridionalis (Amphibia Urodela) during larval development and metamorphosis  

Microsoft Academic Search

Arrangement and morphology of teeth in larval and metamorphic Triturus vulgaris meridionalis were studied at the scanning electron microscope and compared with adult and neothenic newts. Monocuspid larval teeth are monostichous on margin of jaws and polystichous on palatine and coronoid bone. They are substituted during metamorphosis by bicuspid teeth arranged in a single row on margin of the jaws

Fiorenza Accordi; Donatella Mazzarani

1992-01-01

318

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

319

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

320

Sound Source Perception in Anuran Amphibians  

PubMed Central

Sound source perception refers to the auditory system’s ability to parse incoming sensory information into coherent representations of distinct sound sources in the environment. Such abilities are no doubt key to successful communication in many taxa, but we know little about their function in animal communication systems. For anuran amphibians (frogs and toads), social and reproductive behaviors depend on a listener’s ability to hear and identify sound signals amid high levels of background noise in acoustically cluttered environments. Recent neuroethological studies are revealing how frogs parse these complex acoustic scenes to identify individual calls in noisy breeding choruses. Current evidence highlights some interesting similarities and differences in how the auditory systems of frogs and other vertebrates (most notably birds and mammals) perform auditory scene analysis. PMID:22265243

Bee, Mark A

2012-01-01

321

Ambient UV-B radiation causes deformities in amphibian embryos  

PubMed Central

There has been a great deal of recent attention on the suspected increase in amphibian deformities. However, most reports of amphibian deformities have been anecdotal, and no experiments in the field under natural conditions have been performed to investigate this phenomenon. Under laboratory conditions, a variety of agents can induce deformities in amphibians. We investigated one of these agents, UV-B radiation, in field experiments, as a cause for amphibian deformities. We monitored hatching success and development in long-toed salamanders under UV-B shields and in regimes that allowed UV-B radiation. Embryos under UV-B shields had a significantly higher hatching rate and fewer deformities, and developed more quickly than those exposed to UV-B. Deformities may contribute directly to embryo mortality, and they may affect an individual’s subsequent survival after hatching. PMID:9391095

Blaustein, Andrew R.; Kiesecker, Joseph M.; Chivers, Douglas P.; Anthony, Robert G.

1997-01-01

322

Ambient UV-B radiation causes deformities in amphibian embryos  

USGS Publications Warehouse

There has been a great deal of recent attention on the suspected increase in amphibian deformities. However, most reports of amphibian deformities have been anecdotal, and no experiments in the field under natural conditions have been performed to investigate this phenomenon. Under laboratory conditions, a variety of agents can induce deformities in amphibians. We investigated one of these agents, UV-B radiation, in field experiments, as a cause for amphibian deformities. We monitored hatching success and development in long-toed salamanders under UV-B shields and in regimes that allowed UV-B radiation. Embryos under UV-B shields had a significantly higher hatching rate and fewer deformities, and developed more quickly than those exposed to UV-B. Deformities may contribute directly to embryo mortality, and they may affect an individual's subsequent survival after hatching.

Blaustein, A.R.; Kiesecker, J.M.; Chivers, D.P.; Anthony, R.G.

1997-01-01

323

CHARACTERIZATION OF RELATIVE SENSITIVITY OF AMPHIBIANS TO ULTRA VIOLET RADIATION  

EPA Science Inventory

Different studies have demonstrated that solar ultraviolet (UV) radiation can adversely affect survival and development of embryonic and larval amphibians. However, because of among-laboratory variations in exposure profiles (artificial vs. natural sunlight; natural sunlight at d...

324

Why Study Amphibians? They are environmental indicators-their moist,  

E-print Network

to environmental changes and toxins. They have a biphasic life cycle - many species need aquatic habitats Amphibian Research and Monitoring Initiative The southeastern US has 58 species of frogs. Worldwide

Fleskes, Joe

325

Checklist of Helminth parasites of Amphibians from South America.  

PubMed

Parasitological studies on helminths of amphibians in South America have increased in the past few years. Here, we present a list with summarized data published on helminths of South American amphibians from 1925 to 2012, including a list of helminth parasites, host species, and geographic records. We found 194 reports of helminths parasitizing 185 amphibian species from eleven countries: Argentina, Brazil, Chile, Colombia, Equador, French Guyana, Guyana, Paraguay, Peru, Uruguay and Venezuela. Helminth biodiversity includes 278 parasite species of the groups Acanthocephala, Nematoda, Cestoda, Monogenea and Trematoda. A list of helminth parasite species per host, and references are also presented. This contribution aims to document the biodiversity of helminth parasites in South American amphibians, as well as identify gaps in our knowledge, which in turn may guide subsequent studies.  PMID:25082165

Campião, Karla Magalhães; Morais, Drausio Honorio; Dias, Olívia Tavares; Aguiar, Aline; Toledo, Gislayne; Tavares, Luiz Eduardo Roland; Da Silva, Reinaldo José

2014-01-01

326

CHARACTERIZATION OF RELATIVE SENSITIVITY OF AMPHIBIANS TO ULTRAVIOLET RADIATION  

EPA Science Inventory

Different studies have demonstrated that solar ultraviolet (UV) radiation can adversely affect survival and development of embryonic and larval amphibians. However, because of among-laboratory variations in exposure profiles (artificial vs. natural sunlight; natural sunlight at d...

327

A database of life-history traits of European amphibians  

PubMed Central

Abstract In the current context of climate change and landscape fragmentation, efficient conservation strategies require the explicit consideration of life history traits. This is particularly true for amphibians, which are highly threatened worldwide, composed by more than 7400 species, which is constitute one of the most species-rich vertebrate groups. The collection of information on life history traits is difficult due to the ecology of species and remoteness of their habitats. It is therefore not surprising that our knowledge is limited, and missing information on certain life history traits are common for in this species group. We compiled data on amphibian life history traits from literature in an extensive database with morphological and behavioral traits, habitat preferences and movement abilities for 86 European amphibian species (50 Anuran and 36 Urodela species). When it were available, we reported data for males, females, juveniles and tadpoles. Our database may serve as an important starting point for further analyses regarding amphibian conservation.

Moulherat, Sylvain; Calvez, Olivier; Stevens, Virginie M; Clobert, Jean; Schmeller, Dirk S

2014-01-01

328

Molecular characterization of an inhibitor of apoptosis in the Egyptian armyworm, Spodoptera littoralis, and midgut cell death during metamorphosis.  

PubMed

The cDNA corresponding to an inhibitor of apoptosis (IAP) from the Egyptian armyworm, Spodoptera littoralis, was cloned by RT-PCR. Sequence analysis showed that the IAP of S. littoralis (SlIAP) contains two baculoviral IAP repeat (BIR) motifs, followed by a RING finger, an organization which is very similar to that of other lepidopteran IAPs. SlIAP mRNA was detected in ovary, testis, salivary gland, fat body, epidermis, brain and midgut of S. littoralis. During the last larval instar, prepupal and pupal stages, brain mRNA levels remained approximately constant, whereas those of midgut showed a large peak centred in the prepupal stage. Midgut morphology changed during metamorphosis from a semi-transparent, cylindrical structure in last instar larvae to a brownish globular mass in pupae. TUNEL assays, LysoTracker staining and caspase-3 immunohistochemistry, indicated that programmed cell death in midgut starts actively at the onset of pupation process, coinciding with the dramatic decrease of SlIAP mRNA levels observed at the same time. PMID:17967343

Vilaplana, Lluïsa; Pascual, Nuria; Perera, Nathalia; Bellés, Xavier

2007-12-01

329

The influence of acidic pond water on amphibians: A review  

Microsoft Academic Search

Acidic pond water may influence the reproduction of amphibians by causing direct mortality of embryos and larvae, and\\/or by disrupting trophic relationships between amphibians and other aquatic organisms. The embryo is the most sensitive stage of development and may abort soon after exposure to very low pH or eventually fail to hatch at a more moderate pH. Larvae are killed

Joseph Freda

1986-01-01

330

The effect of fish and aquatic habitat complexity on amphibians  

Microsoft Academic Search

Fish introductions are considered one of the most widespread anthropogenic threats to aquatic ecosystems. Their negative impact\\u000a on native amphibian communities has received increasing attention in recent years. We investigated the relationship between\\u000a the introduced fish, emergent vegetation cover and native amphibians in man-made ponds generated by regulation and dam building\\u000a along the Târnava Mare Valley (Romania) during the last

Tibor Hartel; Szilárd Nemes; Dan Cog?lniceanu; Kinga Öllerer; Oliver Schweiger; Cosmin-Ioan Moga; László Demeter

2007-01-01

331

Toxicity of road salt to Nova Scotia amphibians  

Microsoft Academic Search

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 (LC50) were performed on five locally common amphibian species using a

Sara J. Collins; Ronald W. Russell

2009-01-01

332

Focal Review: The Origin(s) of Modern Amphibians  

Microsoft Academic Search

The recent description of the stem batrachian Gerobatrachus has changed the terms of the ongoing debate on the origin of extant amphibians (Lissamphibia: frogs, salamanders, and the\\u000a limbless caecilians). This important fossil, through a shared mosaic of unique derived salientian and urodele characters,\\u000a links frogs and salamanders with an archaic group of fossil amphibians known as amphibamid temnospondyls. The present

Jason S. Anderson

2008-01-01

333

Tropical amphibian populations experience higher disease risk in natural habitats.  

PubMed

Habitat loss and disease are main drivers of global amphibian declines, yet the interaction between them remains largely unexplored. Here we show that paradoxically, habitat loss is negatively associated with occurrence, prevalence, and infection intensity of the chytrid fungus Batrachochytrium dendrobatidis (Bd) in amphibian populations in the tropics. At a large spatial scale, increased habitat loss predicted lower disease risk in amphibian populations across Costa Rica and eastern Australia, even after jointly considering the effect of potential biotic and abiotic correlates. Lower host-species richness and suboptimal microclimates for Bd in disturbed habitats are potential mechanisms underlying this pattern. Furthermore, we found that anthropogenic deforestation practices biased to lowlands and natural vegetation remaining in inaccessible highlands explain increased Bd occurrence at higher elevations. At a smaller spatial scale, holding constant elevation, latitude, and macroclimate, we also found a negative relationship between habitat loss, and both Bd prevalence and infection intensity in frog populations in two landscapes of the Brazilian Atlantic Forest. Our results indicate that amphibians will be disproportionately affected by emerging diseases in pristine environments, and that, paradoxically, disturbed habitats may act as shelters from disease, but only for the very few species that can tolerate deforestation. Thus, tropical amphibian faunas are threatened both by destruction of natural habitats as well as increased disease in pristine forests. To curb further extinctions and develop effective mitigation and restoration programs we must look to interactions between habitat loss and disease, the two main factors at the root of global amphibian declines. PMID:21628560

Becker, C Guilherme; Zamudio, Kelly R

2011-06-14

334

Global amphibian declines: perspectives from the United States and beyond  

USGS Publications Warehouse

Over recent decades, amphibians have experienced population declines, extirpations and species-level extinctions at an alarming rate. Numerous potential etiologies for amphibian declines have been postulated including climate and habitat degradation. Other potential anthropogenic causes including overexploitation and the frequent introductions of invasive predatory species have also been blamed for amphibian declines. Still other underlying factors may include infectious diseases caused by the chytrid fungus Batrachochytrium dendrobatidis, pathogenic viruses (Ranavirus), and other agents. It is nearly certain that more than one etiology is to blame for the majority of the global amphibian declines, and that these causal factors include some combination of climatological or physical habitat destabilization and infectious disease, most notably chytridiomycosis. Scientific research efforts are aimed at elucidating these etiologies on local, regional, and global scales that we might better understand and counteract the driving forces behind amphibian declines. Conservation efforts as outlined in the Amphibian Conservation Action Plan of 2005 are also being made to curtail losses and prevent further extinctions wherever possible.

Densmore, Christine L.

2011-01-01

335

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

336

Multiple stressor effects in relation to declining amphibian populations  

USGS Publications Warehouse

This book represents the work of several authors who participated in the symposium entitled 'Multiple Stressor Effects in Relation to Declining Amphibian Populations' convened 16-17 April, 2002, in Pittsburgh, Pennsylvania. Declines of amphibian populations of varying severity have been observed for many years, and in the last 8 to 10 years considerable progress has been made in documenting the status and distribution of a range of amphibian species. Habitat alteration and destruction are likely linked to many amphibian declines, but a variety of other factors, both anthropogenic and natural, have been observed or proposed to have caused declines or extinctions of amphibian populations. Unfortunately, determining the environmental causes for the decline of many species has proven difficult. The goals of this symposium were three-fold. First, highlight ASTM's historic role in providing a forum for the standardization of amphibian toxicity test methods and the characterization of adverse effects potentially associated with chemical stressors. Second, demonstrate through case studies the current state of technical 'tools' available to biologists, ecologists, environmental scientists and natural resource professionals for assessing amphibian populations exposed to various environmental stressors. And third, characterize a process that brings a range of interdisciplinary technical and management tools to the tasks of causal analysis, especially as those relate to a multiple stressor risk assessment 'mind-set.' As part of the symposium, scientists and resource management professionals from diverse fields including ecotoxicology and chemistry, ecology and field biology, conservation biology, and natural resource management and policy contributed oral presentations and posters that addressed topics related to declining amphibian populations and the role that various stressors have in those losses. The papers contained in this publication reflect the commitment of ASTM International committee E47 on Biological Fate and Environmental Effects to provide timely and comprehensive information to the technical community and the lay-public who have become increasingly aware of amphibians and their current plight. Common themes emphasized throughout the symposium can be found in this issue, including papers focused on (1) toxicity assessment, (2) integrated field and laboratory studies, and (3) causal analysis. In addition to historical accounts of the development of amphibian test methods and contemporary studies illustrating current applications of these methods, this publication addresses future needs by providing contributions focused on research requirements in these areas.

2003-01-01

337

Topoisomerase assays.  

PubMed

Topoisomerases are nuclear enzymes that play essential roles in DNA replication, transcription, chromosome segregation, and recombination. All cells have two major forms of topoisomerases: type I enzymes, which make single-stranded cuts in DNA, and type II enzymes, which cut and pass double-stranded DNA. DNA topoisomerases are important targets of approved and experimental anti-cancer agents. The protocols described in this unit are for assays used to assess new chemical entities for their ability to inhibit both forms of DNA topoisomerase. Included are an in vitro assay for topoisomerase I activity based on relaxation of supercoiled DNA, and an assay for topoisomerase II based on the decatenation of double-stranded DNA. The preparation of mammalian cell extracts for assaying topoisomerase activity is described, along with a protocol for an ICE assay to examine topoisomerase covalent complexes in vivo, and an assay for measuring DNA cleavage in vitro. PMID:22684721

Nitiss, John L; Soans, Eroica; Rogojina, Anna; Seth, Aman; Mishina, Margarita

2012-06-01

338

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

339

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. PMID:20497544

2010-01-01

340

Deciphering amphibian diversity through DNA barcoding: chances and challenges  

PubMed Central

Amphibians globally are in decline, yet there is still a tremendous amount of unrecognized diversity, calling for an acceleration of taxonomic exploration. This process will be greatly facilitated by a DNA barcoding system; however, the mitochondrial population structure of many amphibian species presents numerous challenges to such a standardized, single locus, approach. Here we analyse intra- and interspecific patterns of mitochondrial variation in two distantly related groups of amphibians, mantellid frogs and salamanders, to determine the promise of DNA barcoding with cytochrome oxidase subunit I (cox1) sequences in this taxon. High intraspecific cox1 divergences of 7–14% were observed (18% in one case) within the whole set of amphibian sequences analysed. These high values are not caused by particularly high substitution rates of this gene but by generally deep mitochondrial divergences within and among amphibian species. Despite these high divergences, cox1 sequences were able to correctly identify species including disparate geographic variants. The main problems with cox1 barcoding of amphibians are (i) the high variability of priming sites that hinder the application of universal primers to all species and (ii) the observed distinct overlap of intraspecific and interspecific divergence values, which implies difficulties in the definition of threshold values to identify candidate species. Common discordances between geographical signatures of mitochondrial and nuclear markers in amphibians indicate that a single-locus approach can be problematic when high accuracy of DNA barcoding is required. We suggest that a number of mitochondrial and nuclear genes may be used as DNA barcoding markers to complement cox1. PMID:16221604

Vences, Miguel; Thomas, Meike; Bonett, Ronald M; Vieites, David R

2005-01-01

341

Total sialic acid profile in regressing and remodelling organs during the metamorphosis of marsh frog (Pelophylax ridibundus Pallas 1771).  

PubMed

This study aimed to investigate the functional relationship of sialic acid in regressing and remodelling organs such as the tail, small intestine and liver during the metamorphosis of Pelophylax ridibundus. For this purpose, four groups were composed according to developmental periods by considering Gosner's criteria (1964). Our findings showed that the sialic acid content of the larval tail has an opposite profile to cell death process. Although the sialic acid content of the small intestine and liver did not change evidently during metamorphosis, it increased after the completion of metamorphosis. Frog tail extensively exhibited cell death process and decreased proliferative activity and underwent complete degeneration during metamorphic climax. In spite of increased apoptotic index, a decreased sialic acid level in the tail tissues during climax can be the indication of a death cell removal process. However, the intestine and the liver included both cell death and proliferative process and remodelling in their adult forms. Thus, their sialic acid profiles during metamorphosis were different from the tail's profile. These data show that sialic acid may be an indicator of the presence of some cellular events during metamorphosis and that it can have different roles in the developmental process depending on the organ's fate throughout metamorphosis. PMID:22972462

Kaptan, Engin; Bas, Serap Sancar; Inceli, Meliha Sengezer

2013-03-01

342

19 CFR 12.26 - Importations of wild animals, fish, amphibians, reptiles, mollusks, and crustaceans; prohibited...  

Code of Federal Regulations, 2012 CFR

... false Importations of wild animals, fish, amphibians, reptiles, mollusks...12.26 Importations of wild animals, fish, amphibians, reptiles, mollusks...Pycnonotus jocosus; (x) Any live fish or viable eggs of the family...

2012-04-01

343

19 CFR 12.26 - Importations of wild animals, fish, amphibians, reptiles, mollusks, and crustaceans; prohibited...  

Code of Federal Regulations, 2011 CFR

... false Importations of wild animals, fish, amphibians, reptiles, mollusks...12.26 Importations of wild animals, fish, amphibians, reptiles, mollusks...Pycnonotus jocosus; (x) Any live fish or viable eggs of the family...

2011-04-01

344

19 CFR 12.26 - Importations of wild animals, fish, amphibians, reptiles, mollusks, and crustaceans; prohibited...  

... false Importations of wild animals, fish, amphibians, reptiles, mollusks...12.26 Importations of wild animals, fish, amphibians, reptiles, mollusks...Pycnonotus jocosus; (x) Any live fish or viable eggs of the family...

2014-04-01

345

19 CFR 12.26 - Importations of wild animals, fish, amphibians, reptiles, mollusks, and crustaceans; prohibited...  

Code of Federal Regulations, 2013 CFR

... false Importations of wild animals, fish, amphibians, reptiles, mollusks...12.26 Importations of wild animals, fish, amphibians, reptiles, mollusks...Pycnonotus jocosus; (x) Any live fish or viable eggs of the family...

2013-04-01

346

Amphibian antimicrobial peptides and Protozoa: Lessons from parasites Luis Rivas a,  

E-print Network

Review Amphibian antimicrobial peptides and Protozoa: Lessons from parasites Luis Rivas a, , Juan: Antiprotozoal peptide Plasma membrane Parasite glycocalix Plasmodium Leishmania Cryptosporidium Antimicrobial peptides (AMPs) from amphibians and other eukaryotes recognize pathogenicity patterns mostly related

Pompeu Fabra, Universitat

347

Canyon of the Ancients National Monument Amphibian and Reptile Brad Lambert  

E-print Network

Canyon of the Ancients National Monument Amphibian and Reptile Inventory by Brad Lambert March 2004................................................................................................................ 14 REPTILES OBSERVED IN 2003 SURVEYS Program to conduct field surveys for amphibians and reptiles in the Canyon of the Ancients National

348

Amphibian populations in the terrestrial environment: Is there evidence of declines of terrestrial forest amphibians in northwestern California?  

USGS Publications Warehouse

Amphibian declines have been documented worldwide; however the vast majority are species associated with aquatic habitats. Information on the status and trends of terrestrial amphibians is almost entirely lacking. Here we use data collected across a 12-yr period (sampling from 1984-86 and from 1993-95) to address the question of whether evidence exists for declines among terrestrial amphibians in northwestern California forests. The majority of amphibians, both species and relative numbers, in these forests are direct-developing salamanders of the family Plethodontidae. We examined amphibian richness and evenness, and the relative abundances of the four most common species of plethodontid salamanders. We examined evidence of differences between years in two ecological provinces (coastal and interior) and across young, mature, and late seral forests and with reference to a moisture gradient from xeric to hydric within late seral forests. We found evidence of declines in species richness across years on late seral mesic stands and in the coastal ecological province, but these differences appeared to be caused by differences in the detection of rarer species, rather than evidence of an overall pattern. We also found differences among specific years in numbers of individuals of the most abundant species, Ensatina eschscholtzii, but these differences also failed to reflect a consistent pattern of declines between the two decadal sample periods. Results showing differences in richness, evenness, and relative abundances along both the seral and moisture continua were consistent with previous research. Overall, we found no compelling evidence of a downward trend in terrestrial plethodontid salamanders. We believe that continued monitoring of terrestrial salamander populations is important to understanding mechanisms of population declines in amphibian species. Copyright 2007 Society for the Study of Amphibians and Reptiles.

Welsh, H.H., Jr.; Fellers, G.M.; Lind, A.J.

2007-01-01

349

A review of the role of contaminants in amphibian declines  

USGS Publications Warehouse

CONCLUSIONS--Although there are no published studies that demonstrate beyond all doubt that contaminants are involved in long term population declines of amphibians, there is ample evidence and reason to encourage active research and concern about effects. Many contaminants are lethal to amphibians at environmentally realistic concentrations. Acute mortality from these compounds may be difficult to detect because investigators would have to be present shortly after exposures. Chronic mortality may be masked by metapopulation phenomena so that areas that serve as population sinks may be repeatedly recolonized and difficult to identify. Metapopulation dynamics also make it more difficult to define discrete populations. Contaminants also have many sublethal effects on behavior, energetics, malformations, and diverse effects on physiological pathways which, by themselves might not lead to overt death but could alter reproduction or interact with other factors to result in gradual declines in populations. Scientific understanding of these interactions, and of the ecotoxicology of amphibians in general is far behind what is known about birds, fish, and mammals, and research is desperately needed in this area. Some specific suggestions for critically needed research include: (1) Determination of lethal concentrations of common contaminants - pesticides, PAHs, metals--under environmentally realistic conditions of light, temperature, and water chemistry. (2) Better understanding of the effects of long term (weeks, months), low- concentration exposure of persistent pesticides and stable contaminants on amphibians. (3) Development and refinement of bioindicators in amphibians to use in monitoring and screening for potential effects of contaminants in declining amphibian populations. (4) Further studies on the interaction between contaminants and disease agents including immunosuppression in amphibians. (5) Additional research on the interaction between ultraviolet radiation - both UV-A and UV-B--and a broader range of contaminants. (6) Development of models to assess risk in amphibians as related to landscape factors and especially in the aquatic-terrestrial interface. (7) Population survival requires that organisms survive through their entire life cycle; to date, there have been no studies that have examined the responses of amphibians to contaminants in all phases (egg, embryo, larvae and adult) of their life cycles.

Sparling, D. W.

2003-01-01

350

Amphibian cathelicidin fills the evolutionary gap of cathelicidin in vertebrate.  

PubMed

Cathelicidins comprise a family of antimicrobial peptides (AMPs) sharing a highly conserved cathelin domain, and play a central role in the innate defense against infection in most of vertebrates. But so far it has not yet been found in amphibians although a large number of other groups of AMPs have been identified. In the current work, the first amphibian cathelicidin (cathelicidin-AL) has been characterized from the frog skin of Amolops loloensis. Cathelicidin-AL (RRSRRGRGGGRRGGSGGRGGRGGGGRSGAGSSIAGVGSRGGGGGRHYA) is a cationic peptide containing 48 amino acid residues (aa) with 12 basic aa and no acidic aa. The chemical synthesized peptide efficiently killed bacteria and some fungal species including clinically isolated drug-resistance microorganisms. The cDNA encoding cathelicidin-AL precursor was cloned from the skin cDNA library of A. loloensis. As other cathelicidins, the precursor of cathelicidin-AL also contains highly conserved anionic cathelin domain of cysteine proteinase inhibitor followed by the AMP fragment at C-terminus. Phylogenetic analysis revealed that as connecting link, the amphibian cathelicidin predates reptilia but postdates fish cathelicidin. The peptide purification combined with gene cloning results confirms the presence of cathelicidin in amphibians and filled the evolutionary gap of cathelicidin in vertebrate, considering amphibians' special niche as the animals bridging the evolutionary land-water gap. PMID:22009138

Hao, Xue; Yang, Hailong; Wei, Ling; Yang, Shilong; Zhu, Wenjuan; Ma, Dongying; Yu, Haining; Lai, Ren

2012-08-01

351

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. PMID:20190117

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

2010-01-01

352

Forest mediated light regime linked to amphibian distribution and performance.  

PubMed

The vegetation in and around the basins of ephemeral wetlands can greatly affect light environments for aquatic species such as amphibians. We used hemispherical photographs to quantify the light environment in terms of the global site factor (GSF), the proportion of available solar radiation that actually strikes the wetland. We compared GSF to the distribution and performance of two amphibian species (Pseudacris crucifer and Rana sylvatica) within 17 ephemeral wetlands in northeastern Connecticut, USA. We found that P. crucifer is restricted to lighter wetlands (GSF >0.34) and that its abundance is proportional to GSF. By contrast, R. sylvatica is found across the light gradient and its abundance is unrelated to GSF. For both species, GSF is a strong predictor of larval developmental rate. In addition, P. crucifer growth rate is higher in lighter wetlands. Through thermal effects, changes in resources, or other influences, light appears to be an important predictor of the distribution and performance of amphibians. Because the structure of canopies can change rapidly, and because amphibians can be strongly impacted by these changes, vegetation mediated effects on wetland light environments may be critical to understanding the dynamics of amphibian populations within forested biomes. PMID:12647143

Halverson, M A; Skelly, D K; Kiesecker, J M; Freidenburg, L K

2003-02-01

353

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

354

Imperfect eggs and oviform nymphs: a history of ideas about the origins of insect metamorphosis.  

PubMed

The problem of insect metamorphosis has inspired naturalists for centuries. One question that often arises is why some insects, such as butterflies and bees, undergo a fairly radical metamorphosis while others, such as crickets and lice, do not. Even before the concept of homology emerged scientists speculated which stage found in more direct-developing insects would correspond with the pupal stage of metamorphosing insects. William Harvey (1651) considered the pupal stage to be a continuation of embryonic events, calling it a "second egg." Since then variations of this idea have emerged over the centuries of scientific research and have been supported by a wide variety of methods and rationales. This review will follow those ideas and the ideas that emerged in opposition to them to the present state of the field. PMID:21672785

Erezyilmaz, Deniz F

2006-12-01

355

[Effect of weak electromagnetic radiation on larva development and metamorphosis of grain beetle Tenebrio molitor].  

PubMed

The effect of weak electromagnetic radiation (36 GHz, 100 mu W/cm2) on the development of the grain beetle Tenebrio molitor was studied. Insects were irradiated in different larval instars and at the pupal stage. It was found that weak electromagnetic radiation stimulated the molting and pupation of larvae and the metamorphosis of pupae. The stimulating effect of radiation was weak when animals were exposed in the initial period of the instar and the pupal stage and was more pronounced if the irradiation was carried out in the second half of the current instar and the pupil stage. The effect of weak electromagnetic radiation on the development of beetle can be related to the function of the hormones of metamorphosis. PMID:12630124

She?man, I M; Shkutin, M F

2003-01-01

356

INFLUENCE OF LAND USE ON POSTMETAMORPHIC BODY SIZE OF PLAYA LAKE AMPHIBIANS  

Microsoft Academic Search

Abstract: Agricultural land use may indirectly affect the body size of amphibians by altering the hydroperiods,of nearby wetlands and influencing amphibian,densities—both factors which can limit the larval and postmetamorphic,growth rates of amphibians. Wemeasured postmetamorphic body size for 4 species (Spea multiplicata, S. bombifrons, Bufo cogna- tus, Ambystoma tigrinum mavortium) and 3 age classes (metamorph, subadult, adult) of amphibians captured at

MATTHEW J. GRAY; LOREN M. SMITH

2005-01-01

357

Influence of bacteria and diatoms in biofilms on metamorphosis of the marine slipper limpet Crepidula onyx  

Microsoft Academic Search

Larvae of the slipper limpet Crepidula onyx metamorphose in response to marine biofilms. In this study, we investigated how the percentage of larval metamorphosis in\\u000a this species was affected by biofilms that differed in certain attributes. To manipulate bacterial and diatom cell densities\\u000a and community composition, we developed biofilms in the laboratory (1) at different temperatures (16, 23 and 30°C)

Jill Man-Ying Chiu; Vengatesen Thiyagarajan; Jan A. Pechenik; Oi-Shing Hung; Pei-Yuan Qian

2007-01-01

358

Delayed costs of an induced defense in tadpoles? Morphology, hopping, and development rate at metamorphosis.  

PubMed

Models for the evolution of plasticity predict that individuals having phenotypes induced by exposure to enemies should experience relatively low fitness when enemies are absent. However, costs of induced phenotypes have been difficult to find in both plants and animals, perhaps because costs are expressed at later stages in the life cycle. We searched for delayed costs of an induced defense in larvae of the water frog Rana ridibunda, which exhibits strong phenotypic responses to predators. Tadpoles grew to metamorphosis in outdoor artificial ponds, in either the presence or absence of Aeshna dragonfly larvae confined within cages. We collected metamorphs at forelimb emergence, estimated their development rate until tail resorption was complete, and measured their body and leg shape and hopping performance. Development rate through metamorphosis reflects the duration of a transitional period during which metamorphs are especially vulnerable to predators, and hopping performance may reflect ability to escape predators. Froglets from the dragonfly treatment lost mass through metamorphosis significantly faster than those from predator-free ponds, but they resorbed their tails at about the same rate, despite the fact that their tails were relatively large to begin with. Froglets developing from predator-induced tadpoles had shorter, more muscular legs, and hopped 5% longer distances (difference not significant). Therefore, producing an induced defense against insect predators during the tadpole stage did not exact a cost during or immediately after metamorphosis; if anything, tadpoles with the predator-induced phenotype gave rise to more vigorous froglets. These results focus attention on other costs of the induced phenotype, as well as alternative explanations for plasticity that do not rely on direct fitness trade-offs. PMID:11392399

Van Buskirk, J; Saxer, G

2001-04-01

359

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. PMID:22923392

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

2012-01-01

360

Neuroectodermal and endodermal expression of the ascidian Cdx gene is separated by metamorphosis  

Microsoft Academic Search

Ascidians are a group of invertebrate chordates that exhibit a biphasic life history, with chordate-specific structures developing\\u000a during embryogenesis (dorsal neural tube and notochord) and metamorphosis (pharyngeal gill slits and endostyle). Here we characterize\\u000a the expression of a caudal\\/Cdx gene homologue, Hec-Cdx, from the ascidian Herdmania curvata. Vertebrate Cdx genes are expressed at gastrulation and in the posterior of the

Veronica F. Hinman; Erika Becker; Bernard M. Degnan

2000-01-01

361

Variation in somatic and ovarian development: Predicting susceptibility of amphibians to estrogenic contaminants  

Microsoft Academic Search

Although amphibian sex determination is genetic, it can be manipulated by exogenous hormone exposure during sexual differentiation. The timing of sexual differentiation varies among anuran amphibians such that species may or may not be a tadpole during this period, and therefore, may or may not be exposed to aquatic contaminants. Estrogenic contamination is present in amphibian habitats worldwide. We examined

Sara I. Storrs; Raymond D. Semlitsch

2008-01-01

362

Dryness increases predation risk in efts: support for an amphibian decline hypothesis  

Microsoft Academic Search

One hypothesis for amphibian declines is that increased dryness attributed to global climate change exposes amphibians to greater biotic threat and, consequently, greater mortality. But, little is known about behavioral responses of terrestrial amphibians to dry conditions alone or in combination with biotic threats. We used field observations and laboratory experiments to test the response of efts (terrestrial juveniles) of

Jason R. Rohr; Dale M. Madison

2003-01-01

363

Low Prevalence of Chytrid Fungus (Batrachochytrium dendrobatidis) in Amphibians of U.S. Headwater Streams  

Microsoft Academic Search

Many declines of amphibian populations have been associated with chytridiomycosis, a disease caused by the aquatic fungus Batrachochytrium dendrobatidis (Bd). Despite the relatively high prevalence of chytridiomycosis in stream amphibians globally, most surveys in North America have focused primarily on wetland-associated species, which are frequently infected. To better understand the distribution and prevalence of Bd in headwater amphibian communities, we

Blake R. Hossack; Michael J. Adams; Evan H. Campbell Grant; Christopher A. Pearl; James B. Bettaso; William J. Barichivich; Winsor H. Lowe; Kimberly True; Joy L. Ware; Paul Stephen Corn

2010-01-01

364

2003 Blackwell Publishing Ltd. http://www.blackwellpublishing.com/journals/ddi 89 SPECIAL ISSUE: AMPHIBIAN DECLINES  

E-print Network

amphibians and global amphibian declines have led to public concern, particularly because amphibians, remedies for these problems are not simple. For class II hypotheses, global change (including UV radiation, scientists from around the world exchanged anecdotal reports that led to concern about the possibility

Storfer, Andrew

365

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

366

Effects of forest removal on amphibian migrations: implications for habitat and landscape connectivity  

Microsoft Academic Search

Summary 1. Habitat loss is a leading cause of global amphibian declines. Forest removal is a particularly significant threat because an estimated 82% of amphibians rely on forests for part of their lives. 2. Biphasic amphibians rely on suitable terrestrial habitat to support their post-metamorphic growth and survival and also to maintain appropriate habitat and landscape connectivity. 3. We created

Brian D. Todd; Thomas M. Luhring; Betsie B. Rothermel; J. Whitfield Gibbons

2009-01-01

367

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. PMID:23922930

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

2013-01-01

368

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. PMID:21888661

2011-01-01

369

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

370

Competency of reptiles and amphibians for eastern equine encephalitis virus.  

PubMed

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. PMID:21896798

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

2011-09-01

371

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. PMID:21896798

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

2011-01-01

372

The invasive chytrid fungus of amphibians paralyzes lymphocyte responses.  

PubMed

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 supernatants 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. PMID:24136969

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

2013-10-18

373

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. PMID:24136969

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

374

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

375

Survey of Turkey's endemic amphibians for chytrid fungus Batrachochytrium dendrobatidis.  

PubMed

We report a new survey for Batrachochytrium dendrobatidis (Bd) in Turkey. We swabbed 228 individuals of 7 amphibian species (from 5 families) living in 2 locations (26-August National Park and the Turkish Lakes District) in the southwestern Anatolian region. The infection intensity of all the samples was determined using quantitative PCR. All 4 amphibian breeding sites and 4 amphibian species in 26-August National Park were infected by Bd, with the prevalence at each site ranging from 8 to 29%. Only 1 species was sampled from Beysehir Lake near the conservation area Beysehir Natural Park, but these samples were notable for their high detection rates (prevalence of 32.11%). This study reports the first records of Bd infecting wild Pelophylax ridibundus, Hyla orientalis, Pseudepidalea variabilis, and endemic Beysehir frogs Pelophylax caralitanus. PMID:25266902

Erismis, Ugur Cengiz; Konuk, Muhsin; Yoldas, Taner; Agyar, Pinar; Yumuk, Dilay; Korcan, Safiye Elif

2014-09-30

376

Thirty years of discovering arthropod alkaloids in amphibian skin.  

PubMed

Amphibian skin has provided a wide range of biologically active alkaloids. During the past 30 years, over 400 alkaloids of over 20 structural classes have been detected. These include the batrachotoxins, which are potent and selective activators of sodium channels, the histrionicotoxins, which are potent noncompetitive blockers of nicotinic receptor-gated channels, the pumiliotoxins and related allo- and homo-pumiliotoxins, which have myotonic and cardiotonic activity due to effects on sodium channels, and epibatidine, which has potent antinociceptive activity due to agonist activity at nicotinic receptors. Further classes of alkaloids from amphibian skin include pyrrolidines and piperidines, decahydroquinolines, pyrrolizidines, various indolizidines, quinolizidines, and tricyclic gephyrotoxins, pyrrolizidine oximes, pseudophrynamines, coccinellines, and cyclopentaquinolizidines. Most alkaloids of amphibian skin appear to be sequestered from dietary arthropods. The source of the batrachotoxins, histrionicotoxins, pumiliotoxins, epibatidine, and certain izidines are unknown. PMID:9461669

Daly, J W

1998-01-01

377

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. PMID:24575233

Shahrudin, Shahriza; Jaafar, Ibrahim

2012-01-01

378

Rev: Field Guide to the Amphibians and Reptiles of Bali  

E-print Network

(Wallace's L i n e ) , the islands constitut­ ing Indonesia represent o n e of the world's true su­ perpowers of biodiversity a n d the origin of many of its most spectacular amphibians a n d reptiles. Given these facts, plus the simple truth that Bali... is a popu­ lar vacation spot, a g o o d field guide of the amphib­ ians and reptiles of this island has been badly needed . Bali is an ecotourism mecca . Its amphibians and reptiles ought to be readily accessible to the many thousands of travelers...

Brown, Rafe M.

2008-01-01

379

Development, organization, and remodeling of phoronid muscles from embryo to metamorphosis (Lophotrochozoa: Phoronida)  

PubMed Central

Background The phoronid larva, which is called the actinotrocha, is one of the most remarkable planktotrophic larval types among marine invertebrates. Actinotrochs live in plankton for relatively long periods and undergo catastrophic metamorphosis, in which some parts of the larval body are consumed by the juvenile. The development and organization of the muscular system has never been described in detail for actinotrochs and for other stages in the phoronid life cycle. Results In Phoronopsis harmeri, muscular elements of the preoral lobe and the collar originate in the mid-gastrula stage from mesodermal cells, which have immigrated from the anterior wall of the archenteron. Muscles of the trunk originate from posterior mesoderm together with the trunk coelom. The organization of the muscular system in phoronid larvae of different species is very complex and consists of 14 groups of muscles. The telotroch constrictor, which holds the telotroch in the larval body during metamorphosis, is described for the first time. This unusual muscle is formed by apical myofilaments of the epidermal cells. Most larval muscles are formed by cells with cross-striated organization of myofibrils. During metamorphosis, most elements of the larval muscular system degenerate, but some of them remain and are integrated into the juvenile musculature. Conclusion Early steps of phoronid myogenesis reflect the peculiarities of the actinotroch larva: the muscle of the preoral lobe is the first muscle to appear, and it is important for food capture. The larval muscular system is organized in differently in different phoronid larvae, but always exhibits a complexity that probably results from the long pelagic life, planktotrophy, and catastrophic metamorphosis. Degeneration of the larval muscular system during phoronid metamorphosis occurs in two ways, i.e., by complete or by incomplete destruction of larval muscular elements. The organization and remodeling of the muscular system in phoronids exhibits the combination of protostome-like and deuterostome-like features. This combination, which has also been found in the organization of some other systems in phoronids, can be regarded as an important characteristic and one that probably reflects the basal position of phoronids within the Lophotrochozoa. PMID:23617418

2013-01-01

380

Genetic evidence for a high diversity and wide distribution of endemic strains of the pathogenic chytrid fungus Batrachochytrium dendrobatidis in wild Asian amphibians.  

PubMed

Population declines and extinctions of amphibians have been attributed to the chytrid fungus Batrachochytrium dendrobatidis (Bd), especially one globally emerging recombinant lineage ('Bd-GPL'). We used PCR assays that target the ribosomal internal transcribed spacer region (ITS) of Bd to determine the prevalence and genetic diversity of Bd in South Korea, where Bd is widely distributed but is not known to cause morbidity or mortality in wild populations. We isolated Korean Bd strains from native amphibians with low infection loads and compared them to known worldwide Bd strains using 19 polymorphic SNP and microsatellite loci. Bd prevalence ranged between 12.5 and 48.0%, in 11 of 17 native Korean species, and 24.7% in the introduced bullfrog Lithobates catesbeianus. Based on ITS sequence variation, 47 of the 50 identified Korean haplotypes formed a group closely associated with a native Brazilian Bd lineage, separated from the Bd-GPL lineage. However, multilocus genotyping of three Korean Bd isolates revealed strong divergence from both Bd-GPL and the native Brazilian Bd lineages. Thus, the ITS region resolves genotypes that diverge from Bd-GPL but otherwise generates ambiguous phylogenies. Our results point to the presence of highly diversified endemic strains of Bd across Asian amphibian species. The rarity of Bd-GPL-associated haplotypes suggests that either this lineage was introduced into Korea only recently or Bd-GPL has been outcompeted by native Bd strains. Our results highlight the need to consider possible complex interactions among native Bd lineages, Bd-GPL and their associated amphibian hosts when assessing the spread and impact of Bd-GPL on worldwide amphibian populations. PMID:23802586

Bataille, Arnaud; Fong, Jonathan J; Cha, Moonsuk; Wogan, Guinevere O U; Baek, Hae Jun; Lee, Hang; Min, Mi-Sook; Waldman, Bruce

2013-08-01

381

The Effects of Ultraviolet Radiation on the Biology of Amphibians  

Microsoft Academic Search

SYNOPSIS. Potential causes for the global decline of amphibians include habi- tat loss, disease, environmental contaminants and climate changes. The di- minishing ozone layer and consequent increase of ultraviolet-B radiation reaching the earth's surface has been hypothesized to be a mortality factor, especially in habitats otherwise undisturbed. We discuss the fundamental physics of UV and types of biological damage after

LAWRENCE E. LICHT; KAREN P. GRANT

1997-01-01

382

Tropical amphibian populations experience higher disease risk in natural habitats  

E-print Network

that anthropogenic deforestation practices biased to lowlands and natural vegetation remaining in inaccessible disease, but only for the very few species that can tolerate deforestation. Thus, tropical amphibian and chytridiomycosis, a disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), are two main causes

Zamudio, Kelly R.

383

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

384

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...

385

Invasive hybrid tiger salamander genotypes impact native amphibians  

E-print Network

Invasive hybrid tiger salamander genotypes impact native amphibians Maureen E. Ryana,1 , Jarrett R California Tiger Salamander (Amby- stoma californiense) and the introduced Barred Tiger Salamander (Ambystoma for 20 generations. We found that most classes of hybrid tiger salamander larvae dramatically reduced

Grether, Gregory

386

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...

387

Amphibian diversity: Decimation by disease Pieter T. J. Johnson*  

E-print Network

have detailed its origin, pa- thology, physiology, life cycle, genetic vari- ation, and infection of amphibians. Batrachochytrium has been recovered from the skin of dead or dying frogs associated with numerous exposure of healthy frogs to chytrid zoospores causes rapid deterioration and death in certain species (6

Horton, Tom

388

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

389

Batrachochytrium salamandrivorans sp. nov. causes lethal chytridiomycosis in amphibians  

PubMed Central

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

2013-01-01

390

Applied reproductive technologies and genetic resource banking for amphibian conservation  

Microsoft Academic Search

Abstract. As amphibian populations continue to decline, both government and non-government organisations are estab- lishing captive assurance colonies to secure populations deemed at risk of extinction if left in the wild. For the most part, little is known about the nutritional ecology, reproductive biology or husbandry needs of the animals placed into captive breeding programs. Because of this lack of

Andrew J. Kouba; Carrie K. Vance

2009-01-01

391

ORIGINAL ARTICLE Co-habiting amphibian species harbor unique skin  

E-print Network

amphibian individuals were sampled from three different species including northern leopard frogs (Lithobates pipiens), western chorus frogs (Pseudacris triseriata) and tiger salamanders (Ambystoma tigrinum). We diversity varied strongly across species: L. pipiens had the highest diversity; A. tigrinum the lowest. Host

McKenzie, Valerie

392

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,...

393

Genome variations in the transition from amphibians to reptiles  

Microsoft Academic Search

Summary Many characters differentiate amphibian from reptilian genomes. The former have, on the average, larger and more variable genome sizes, a greater repetitive DNA percentage, and a higher interspersion level among DNAs with different degrees of repetitivity. Reptiles have more reduced and uniform genome sizes, a repetitive DNA percentage generally lower than 50%, and a lower interspersion level. Other differences

Ettore Olmo

1991-01-01

394

Embryonic appearance of rod opsin in the urodele amphibian eye  

Microsoft Academic Search

Notophthalmus (Triturus) viridescens, a urodele amphibian (newt) common to the Eastern United States, is a promising subject for developmental and regeneration studies. We have available a monoclonal antibody shown to be specific in many vertebrates for rod opsin, the membrane apoprotein of the visual pigment rhodopsin. This antibody to an N-terminal epitope, by rigorous biochemical and immunological criteria, recognizes only

David Stephen McDevitt; Samir Kumar Brahma; Jean-Claude Jeanny

1993-01-01

395

Amphibian ocular malformation associated with frog virus 3  

Microsoft Academic Search

During an on-going amphibian ecology study, a free-ranging American bullfrog (Rana catesbeiana) metamorph was captured in a pitfall trap adjacent to a constructed farm pond at the Plateau Research and Education Center (PREC) on the Cumberland Plateau near Crossville, Tennessee, USA. Grossly, the right eye was approximately 50% the size of the left. Stereo and light microscopic examination revealed two

Elizabeth C. Burton; Debra L. Miller; Eloise L. Styer; Matthew J. Gray

2008-01-01

396

Evidence for disease-related amphibian decline in Colorado  

Microsoft Academic Search

The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture-recapture of adults and counts of egg masses to examine the

Erin Muths; Paul Stephen Corn; Allan P. Pessier; D. Earl Green

397

Amphibians of an open cerrado fragment in southeastern Brazil  

Microsoft Academic Search

The Cerrado encompasses ca. 2 million km2 in Brazil. Most Cerrado areas have been greatly disturbed in the past decades. Only 20% of this biome remain undisturbed, and only 1.2% is protected. Knowledge on the biology and diversity of Cerrado amphibian assemblages is still incipient. Here we present natural history information (habitat use and reproductive activity) of 28 species of

Cínthia Aguirre Brasileiro; Ricardo J. Sawaya; Mara C. Kiefer; Marcio Martins

2005-01-01

398

Measuring the Meltdown: Drivers of Global Amphibian Extinction and Decline  

PubMed Central

Habitat loss, climate change, over-exploitation, disease and other factors have been hypothesised in the global decline of amphibian biodiversity. However, the relative importance of and synergies among different drivers are still poorly understood. We present the largest global analysis of roughly 45% of known amphibians (2,583 species) to quantify the influences of life history, climate, human density and habitat loss on declines and extinction risk. Multi-model Bayesian inference reveals that large amphibian species with small geographic range and pronounced seasonality in temperature and precipitation are most likely to be Red-Listed by IUCN. Elevated habitat loss and human densities are also correlated with high threat risk. Range size, habitat loss and more extreme seasonality in precipitation contributed to decline risk in the 2,454 species that declined between 1980 and 2004, compared to species that were stable (n?=?1,545) or had increased (n?=?28). These empirical results show that amphibian species with restricted ranges should be urgently targeted for conservation. PMID:18286193

Sodhi, Navjot S.; Bickford, David; Diesmos, Arvin C.; Lee, Tien Ming; Koh, Lian Pin; Brook, Barry W.; Sekercioglu, Cagan H.; Bradshaw, Corey J. A.

2008-01-01

399

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

400

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

401

Effects of experimental forestry treatments on a Maine amphibian community  

Microsoft Academic Search

Predicting how timber harvesting will influence sensitive taxa such as amphibians is of critical importance for sustainable management of forests. In 2004 and 2005, we studied the effects of four forestry treatments (clearcut with coarse woody debris [CWD] removed, clearcut with CWD retained, partial-cut of 50% of canopy cover, and an uncut control) on movement, habitat selection, and abundance of

David A. Patrick; Malcolm L. Hunter Jr.; Aram J. K. Calhoun

2006-01-01

402

Responses of Aquatic and Streamside Amphibians to Timber Harvest  

E-print Network

of timber harvest vary among species, physical habitats, and regions of the Pacific Northwest. Populations of giant salamanders (Dicamptodon) increased fol lowing clear-cutting in the Oregon Cascades, while Northwest. Amphibians play several ecological roles. Giant salamanders (Dicamptodon) replace salmonid fishes

403

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the mortality and growth of two amphibian species (Xenopus laevis and Pseudacris triseriata).  

PubMed

We observed a slight drop in the growth of Xenopus laevis and Pseudacris triseriata larvae following acute exposure (24-48 h) during egg development to three concentrations of TCDD (0.3, 3.0, 30.0 microg/l). Our exposure protocol was modeled on a previous investigation that was designed to mimic the effects of maternal deposition of TCDD. The doses selected were consistent with known rates of maternal transfer between mother and egg using actual adult body burdens from contaminated habitats. Egg and embryonic mortality immediately following exposure increased only among 48 h X. laevis treatments. Control P. triseriata and X. laevis completed metamorphosis more quickly than TCDDtreated animals. The snout-vent length of recently transformed P. triseriata did not differ between treatments although controls were heavier than high-dosed animals. Likewise, the snout-vent length and weight of transformed X. laevis did not differ between control and TCDD treatments. These findings provide additional evidence that amphibians, including P. triseriata and X. laevis are relatively insensitive to acute exposure to TCDD during egg and embryonic development. Although the concentrations selected for this study were relatively high, they were not inconsistent with our current understanding of bioaccumulation via maternal transfer. PMID:19151431

Collier, Alex; Orr, Lowell; Morris, Julie; Blank, James

2008-12-01

404

Projected climate impacts for the amphibians of the western hemisphere  

USGS Publications Warehouse

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.

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

2010-01-01

405

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

406

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

407

Applied reproductive technologies and genetic resource banking for amphibian conservation.  

PubMed

As amphibian populations continue to decline, both government and non-government organisations are establishing captive assurance colonies to secure populations deemed at risk of extinction if left in the wild. For the most part, little is known about the nutritional ecology, reproductive biology or husbandry needs of the animals placed into captive breeding programs. Because of this lack of knowledge, conservation biologists are currently facing the difficult task of maintaining and reproducing these species. Academic and zoo scientists are beginning to examine different technologies for maintaining the genetic diversity of founder populations brought out of the wild before the animals become extinct from rapidly spreading epizootic diseases. One such technology is genetic resource banking and applied reproductive technologies for species that are difficult to reproduce reliably in captivity. Significant advances have been made in the last decade for amphibian assisted reproduction including the use of exogenous hormones for induction of spermiation and ovulation, in vitro fertilisation, short-term cold storage of gametes and long-term cryopreservation of spermatozoa. These scientific breakthroughs for a select few species will no doubt serve as models for future assisted breeding protocols and the increasing number of amphibians requiring conservation intervention. However, the development of specialised assisted breeding protocols that can be applied to many different families of amphibians will likely require species-specific modifications considering their wide range of reproductive modes. The purpose of this review is to summarise the current state of knowledge in the area of assisted reproduction technologies and gene banking for the conservation of amphibians. PMID:19567216

Kouba, Andrew J; Vance, Carrie K

2009-01-01

408

Control of pituitary thyroid-stimulating hormone synthesis and secretion by thyroid hormones during Xenopus metamorphosis.  

PubMed

We used ex vivo and in vivo experiments with Xenopus laevis tadpoles to examine the hypothesis that the set-point for negative feedback on pituitary thyroid-stimulating hormone (TSH) synthesis and secretion by thyroid hormones (THs) increases as metamorphosis progresses to allow for the previously documented concomitant increase in serum TH concentrations and pituitary TSH mRNA expression during this transformative process. First, pituitaries from climactic tadpoles were cultured for up to 96 h to characterize the ability of pituitary explants to synthesize and secrete TSH? in the absence of hypothalamic and circulating hormones. Next, pituitary explants from tadpoles NF stages 54-66 were exposed to physiologically-relevant concentrations of THs to determine whether stage-specific differences exist in pituitary sensitivity to negative feedback by THs. Finally, in vivo exposures of tadpoles to THs were conducted to confirm the results of the ex vivo experiments. When pituitaries from climactic tadpoles were removed from the influence of endogenous hormones, TSH? mRNA expression increased late or not at all whereas the rate of TSH? secreted into media increased dramatically, suggesting that TSH secretion, but not TSH mRNA expression, is under the negative regulation of an endogenous signal during the climactic stages of metamorphosis. Pituitaries from pre- and prometamorphic tadpoles were more sensitive to TH-induced inhibition of TSH? mRNA expression and secretion than pituitaries from climactic tadpoles. The observed decrease in sensitivity of pituitary TSH? mRNA expression to negative feedback by THs from premetamorphosis to metamorphic climax was confirmed by in vivo experiments in which tadpoles were reared in water containing THs. Based on the results of this study, a model is proposed to explain the seemingly paradoxical, concurrent rise in serum TH concentrations and pituitary TSH mRNA expression during metamorphosis in larval anurans. PMID:21803044

Sternberg, Robin M; Thoemke, Kara R; Korte, Joseph J; Moen, Scott M; Olson, Jessica M; Korte, Lisa; Tietge, Joseph E; Degitz, Sigmund J

2011-09-15

409

Histone acetylation mediates epigenetic regulation of transcriptional reprogramming in insects during metamorphosis, wounding and infection  

PubMed Central

Background Gene expression in eukaryotes is regulated by histone acetylation/deacetylation, an epigenetic process mediated by histone acetyltransferases (HATs) and histone deacetylases (HDACs) whose opposing activities are tightly regulated. The acetylation of histones by HATs increases DNA accessibility and promotes gene expression, whereas the removal of acetyl groups by HDACs has the opposite effect. Results We explored the role of HDACs and HATs in epigenetic reprogramming during metamorphosis, wounding and infection in the lepidopteran model host Galleria mellonella. We measured the expression of genes encoding components of HATs and HDACs to monitor the transcriptional activity of each enzyme complex and found that both enzymes were upregulated during pupation. Specific HAT inhibitors were able to postpone pupation and to reduce insect survival following wounding, whereas HDAC inhibitors accelerated pupation and increased survival. The administration of HDAC inhibitors modulated the expression of effector genes with key roles in tissue remodeling (matrix metalloproteinase), the regulation of sepsis (inhibitor of metalloproteinases from insects) and host defense (antimicrobial peptides), and simultaneously induced HAT activity, suggesting that histone acetylation is regulated by a feedback mechanism. We also discovered that both the entomopathogenic fungus Metarhizium anisopliae and the human bacterial pathogen Listeria monocytogenes can delay metamorphosis in G. mellonella by skewing the HDAC/HAT balance. Conclusions Our study provides for the first evidence that pathogenic bacteria can interfere with the regulation of HDACs and HATs in insects which appear to manipulate host immunity and development. We conclude that histone acetylation/deacetylation in insects mediates transcriptional reprogramming during metamorphosis and in response to wounding and infection. PMID:23035888

2012-01-01

410

Post-embryonic transcriptomes of the prawn Macrobrachium rosenbergii: multigenic succession through metamorphosis.  

PubMed

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. PMID:23372848

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

2013-01-01

411

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

412

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. PMID:23372848

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

2013-01-01

413

Transcription factor E93 specifies adult metamorphosis in hemimetabolous and holometabolous insects  

PubMed Central

All immature animals undergo remarkable morphological and physiological changes to become mature adults. In winged insects, metamorphic changes either are limited to a few tissues (hemimetaboly) or involve a complete reorganization of most tissues and organs (holometaboly). Despite the differences, the genetic switch between immature and adult forms in both types of insects relies on the disappearance of the antimetamorphic juvenile hormone (JH) and the transcription factors Krüppel-homolog 1 (Kr-h1) and Broad-Complex (BR-C) during the last juvenile instar. Here, we show that the transcription factor E93 is the key determinant that promotes adult metamorphosis in both hemimetabolous and holometabolous insects, thus acting as the universal adult specifier. In the hemimetabolous insect Blattella germanica, BgE93 is highly expressed in metamorphic tissues, and RNA interference (RNAi)-mediated knockdown of BgE93 in the nymphal stage prevented the nymphal–adult transition, inducing endless reiteration of nymphal development, even in the absence of JH. We also find that BgE93 down-regulated BgKr-h1 and BgBR-C expression during the last nymphal instar of B. germanica, a key step necessary for proper adult differentiation. This essential role of E93 is conserved in holometabolous insects as TcE93 RNAi in Tribolium castaneum prevented pupal–adult transition and produced a supernumerary second pupa. In this beetle, TcE93 also represses expression of TcKr-h1 and TcBR-C during the pupal stage. Similar results were obtained in the more derived holometabolous insect Drosophila melanogaster, suggesting that winged insects use the same regulatory mechanism to promote adult metamorphosis. This study provides an important insight into the understanding of the molecular basis of adult metamorphosis. PMID:24778249

Urena, Enric; Manjon, Cristina; Franch-Marro, Xavier; Martin, David

2014-01-01

414

Diagrammar and metamorphosis of coset symmetries in dimensionally reduced type IIB supergravity  

E-print Network

Studying the reduction of type IIB supergravity from ten to three space-time dimensions we describe the metamorphosis of Dynkin diagram for gravity line "caterpillar" into a type IIB supergravity "dragonfly" that is triggered by inclusion of scalars and antisymmetric tensor fields. The final diagram corresponds to type IIB string theory E8 global symmetry group which is the subgroup of the conjectured E11 hidden symmetry group. Application of the results for getting the type IIA/IIB T-duality rules and for searching for type IIB vacua solutions is considered.

Alexei J. Nurmagambetov

2004-03-09

415

Diagrammar and metamorphosis of coset symmetries in dimensionally reduced type IIB supergravity  

E-print Network

Studying the reduction of type IIB supergravity from ten to three space-time dimensions we describe the metamorphosis of Dynkin diagram for gravity line "caterpillar" into a type IIB supergravity "dragonfly" that is triggered by inclusion of scalars and antisymmetric tensor fields. The final diagram corresponds to type IIB string theory E8 global symmetry group which is the subgroup of the conjectured E11 hidden symmetry group. Application of the results for getting the type IIA/IIB T-duality rules and for searching for type IIB vacua solutions is considered.

Nurmagambetov, A J

2004-01-01

416

Interactions between amphibians' symbiotic bacteria cause the production of emergent anti-fungal metabolites.  

PubMed

Amphibians possess beneficial skin bacteria that protect against the disease chytridiomycosis by producing secondary metabolites that inhibit the pathogen Batrachochytrium dendrobatidis (Bd). Metabolite production may be a mechanism of competition between bacterial species that results in host protection as a by-product. We expect that some co-cultures of bacterial species or strains will result in greater Bd inhibition than mono-cultures. To test this, we cultured four bacterial isolates (Bacillus sp., Janthinobacterium sp., Pseudomonas sp. and Chitinophaga arvensicola) from red-backed salamanders (Plethodon cinereus) and cultured isolates both alone and together to collect their cell-free supernatants (CFS). We challenged Bd with CFSs from four bacterial species in varying combinations. This resulted in three experimental treatments: (1) CFSs of single isolates; (2) combined CFSs of two isolates; and (3) CFSs from co-cultures. Pair-wise combinations of four bacterial isolates CFSs were assayed against Bd and revealed additive Bd inhibition in 42.2% of trials, synergistic inhibition in 42.2% and no effect in 16.6% of trials. When bacteria isolates were grown in co-cultures, complete Bd inhibition was generally observed, and synergistic inhibition occurred in four out of six trials. A metabolite profile of the most potent co-culture, Bacillus sp. and Chitinophaga arvensicola, was determined with LC-MS and compared with the profiles of each isolate in mono-culture. Emergent metabolites appearing in the co-culture were inhibitory to Bd, and the most potent inhibitor was identified as tryptophol. Thus mono-cultures of bacteria cultured from red-backed salamanders interacted synergistically and additively to inhibit Bd, and such bacteria produced emergent metabolites when cultured together, with even greater pathogen inhibition. Knowledge of how bacterial species interact to inhibit Bd can be used to select probiotics to provide amphibians with protection against Bd. PMID:25191317

Loudon, Andrew H; Holland, Jessica A; Umile, Thomas P; Burzynski, Elizabeth A; Minbiole, Kevin P C; Harris, Reid N

2014-01-01

417

Comet assay in genetic ecotoxicology: a review.  

PubMed

The Comet assay, also called the single cell gel electrophoresis (SCGE) assay or microgel electrophoresis (MGE) assay, primarily measures DNA strand breakage in single cells. Since the protocol was published by Singh et al. [1988], its use has increased in different topic areas: clinical applications, human monitoring, radiation biology, genetic toxicology, and genetic ecotoxicology. This study is a review of the investigations that have involved the alkaline version of the Comet assay in genetic ecotoxicology. It focuses mainly on the type of organisms (plants, worms, molluscs, fish, amphibians, and mammalians) but also on the type of cells that have been used for ecotoxicological studies. In the 23 papers published since 1993 and presented here, the original test procedure may have been slightly modified according to the cell type. In vitro and in vivo experiments as well as in situ studies have been carried out in various environments (water, soil, and air). Although the Comet assay is able to detect genotoxic effects of chemical and physical agents, only chemical substances and environmental complex mixtures will be considered in this review. PMID:10618172

Cotelle, S; Férard, J F

1999-01-01

418

Meconial peritrophic membranes and the fate of midgut bacteria during mosquito (Diptera: Culicidae) metamorphosis.  

PubMed

The location of midgut bacteria relative to meconial peritrophic membranes (MPMs) and changes in bacterial numbers during midgut metamorphosis were studied in Anopheles punctipennis (Say), Culex pipiens (L.), and Aedes aegypti (L.) pupae and newly emerged adults. After adult emergence in Aedes, Anopheles, and most Culex, there were few to no bacteria in the midgut. In most newly emerged adult mosquitoes, few bacteria were found in either the lumen or within the MPMs/meconia. In a few Culex specimens, high numbers of bacteria were found in the MPMs/meconia and low numbers in the lumen. In all three species bacterial counts were high in fourth instars, decreased after final larval defecation, increased in young pupae, and increased further in old pupae. A very effective gut sterilization mechanism is operating during mosquito metamorphosis and adult emergence. This mechanism appears to involve the sequestration of remaining larval gut bacteria within the confines of the meconium and one or two MPMs and the possible bactericidal effect of the exuvial (molting) fluid, which is ingested during the process of adult emergence. PMID:11268687

Moll, R M; Romoser, W S; Modrzakowski, M C; Moncayo, A C; Lerdthusnee, K

2001-01-01

419

A field guide to amphibian larvae and eggs of Minnesota, Wisconsin, and Iowa  

USGS Publications Warehouse

Apparent worldwide declines in amphibian populations (Pechmann and Wake 1997) have stimulated interest in amphibians as bioindicators of the health of ecosystems. Because we have little information on the population status of many species, there is interest by public and private land management agencies in monitoring amphibian populations. Amphibian egg and larval surveys are established methods of surveying pond-breeding amphibians. Adults may be widely dispersed across the landscape, but eggs and larvae are confined to the breeding site during a specific season of the year. Also, observations of late-stage larvae or metamorphs are evidence of successful reproduction, which is an important indicator of the viability of the population. The goal of this guide is to help students, natural resources personnel, and biologists identify eggs and larval stages of amphibians in the field without the aid of a microscope.

Parmelee, J.R.; Knutson, M.G.; Lyon, J.E.

2002-01-01

420

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

421

Visualising lymph movement in anuran amphibians with computed tomography.  

PubMed

Lymph flux rates in anuran amphibians are high relative to those of other vertebrates owing to 'leaky' capillaries and a high interstitial compliance. Lymph movement is accomplished primarily by specialised lymph muscles and lung ventilation that move lymph through highly compartmentalised lymph sacs to the dorsally located lymph hearts, which are responsible for pumping lymph into the circulatory system; however, it is unclear how lymph reaches the lymph hearts. We used computed tomography (CT) to visualise an iodinated contrast agent, injected into various lymph sacs, through the lymph system in cane toads (Rhinella marina). We observed vertical movement of contrast agent from lymph sacs as predicted, but the precise pathways were sometimes unexpected. These visual results confirm predictions regarding lymph movement, but also provide some novel findings regarding the pathways for lymph movement and establish CT as a useful technique for visualising lymph movement in amphibians. PMID:25165132

Hedrick, Michael S; Hansen, Kasper; Wang, Tobias; Lauridsen, Henrik; Thygesen, Jesper; Pedersen, Michael

2014-09-01

422

Congenital malformations of the vertebral column in ancient amphibians.  

PubMed

Temnospondyls, the largest group of Palaeozoic and Mesozoic amphibians, primitively possess rhachitomous vertebrae with multipartite centra (consisting of one horse-shoe-shaped inter- and paired pleurocentra). In a group of temnospondyls, the stereospondyls, the intercentra became pronounced and disc-like, whereas the pleurocentra were reduced. We report the presence of congenital vertebral malformations (hemi, wedge and block vertebrae) in Permian and Triassic temnospondyls, showing that defects of formation and segmentation in the tetrapod vertebral column represent a fundamental failure of somitogenesis that can be followed throughout tetrapod evolution. This is irrespective of the type of affected vertebra, that is, rhachitomous or stereospondylous, and all components of the vertebra can be involved (intercentrum, pleurocentrum and neural arch), either together or independently on their own. This is the oldest known occurrence of wedge vertebra and congenital block vertebra described in fossil tetrapods. The frequency of vertebral congenital malformations in amphibians appears unchanged from the Holocene. PMID:23551141

Witzmann, F; Rothschild, B M; Hampe, O; Sobral, G; Gubin, Y M; Asbach, P

2014-04-01

423

Batrachochytrium dendrobatidis infection and lethal chytridiomycosis in caecilian amphibians (Gymnophiona).  

PubMed

Batrachochytrium dendrobatidis (Bd) is commonly termed the 'amphibian chytrid fungus' but thus far has been documented to be a pathogen of only batrachian amphibians (anurans and caudatans). It is not proven to infect the limbless, generally poorly known, and mostly soil-dwelling caecilians (Gymnophiona). We conducted the largest qPCR survey of Bd in caecilians to date, for more than 200 field-swabbed specimens from five countries in Africa and South America, representing nearly 20 species, 12 genera, and 8 families. Positive results were recovered for 58 specimens from Tanzania and Cameroon (4 families, 6 genera, 6+ species). Quantities of Bd were not exceptionally high, with genomic equivalent (GE) values of 0.052-17.339. In addition, we report the first evidence of lethal chytridiomycosis in caecilians. Mortality in captive (wild-caught, commercial pet trade) Geotrypetes seraphini was associated with GE scores similar to those we detected for field-swabbed, wild animals. PMID:23677560

Gower, David J; Doherty-Bone, Thomas; Loader, Simon P; Wilkinson, Mark; Kouete, Marcel T; Tapley, Benjamin; Orton, Frances; Daniel, Olivia Z; Wynne, Felicity; Flach, Edmund; Müller, Hendrik; Menegon, Michele; Stephen, Ian; Browne, Robert K; Fisher, Mathew C; Cunningham, Andrew A; Garner, Trenton W J

2013-06-01

424

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.

425

Invasive hybrid tiger salamander genotypes impact native amphibians  

PubMed Central

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.

2009-01-01

426

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

427

Enzymatic Synthesis of the Skin-lightening Agent, Melatonin, in Amphibians  

Microsoft Academic Search

MELATONIN (N-acetyl-5-methoxytryptamine) has been shown to be the most effective skin-lightening agent in amphibians1,2. This compound produces changes in pigmentation by causing the aggregation of melanin granules within the amphibian melanocyte. Although melatonin has been found to occur in mammals, no evidence for its formation has been obtained in amphibians where it exerts its most potent effects. High concentrations of

Julius Axelrod; WILBUR B. QUAY; PETER C. BAKER

1965-01-01

428

Size-structured effects of common carp on reproduction of pond-breeding amphibians  

Microsoft Academic Search

The role of fish in driving amphibian communities has been widely recognized. However, little is known about size-structured\\u000a interactions between amphibian and fish populations. This study compared the taxonomic occurrence and densities of larval\\u000a amphibians between unstocked ponds and ponds stocked with different age cohorts of common carp Cyprinus carpio differing in average body size. The average total densities of

Janusz Kloskowski

2009-01-01

429

Evidence of continued effects from timber harvesting on lotic amphibians in redwood forests of northwestern California  

Microsoft Academic Search

We compared species richness and relative abundance of stream-associated amphibians in late-seral redwood forests with those in mid-seral, second-growth forests to examine the continued (as opposed to immediate) effects of timber harvest on amphibian populations. Lacking pre-harvest data on amphibian abundances for streams in the second-growth stands, we assumed that nearby tributaries transecting late-seral stands with similar topography and flora

Donald T. Ashton; Sharyn B. Marks; Hartwell H. Welsh

2006-01-01

430

Acid sensitivity and water chemistry correlates of amphibian breeding ponds in northern Wisconsin, USA  

Microsoft Academic Search

Fifty-one amphibian breeding sites in northern Wisconsin were sampled in two surveys, in 1986 and 1987, to determine the chemical conditions and amphibian inhabitants present. All twenty-one ponds in 1986 and twenty-eight in 1987 were mildly acidic and sensitive to acidification. The pH levels encountered were generally not toxic to the resident amphibians, and may have been related to levels

Franz J. Kutka; Marilyn D. Bachmann

1990-01-01

431

Extinction risk assessments at the population and species level: implications for amphibian conservation  

Microsoft Academic Search

Amphibian populations are declining worldwide and this is causing growing concern. High levels of population declines followed\\u000a by the expansion of red lists are creating demands for effective strategies to maximize conservation efforts for amphibians.\\u000a Ideally, integrated and comprehensive strategies should be based on complementary information of population and species extinction\\u000a risk. Here we evaluate the congruence between amphibian extinction

Carlos Guilherme Becker; Rafael Dias Loyola

2008-01-01

432

COMBINED EFFECTS OF UV-B RADIATION AND NITRATE FERTILIZER ON LARVAL AMPHIBIANS  

Microsoft Academic Search

As part of a global loss of biodiversity, amphibian populations are declining worldwide. Numerous factors may be involved in these declines, including environmental changes and the spread of contaminants. Ultraviolet-B (UV-B) radiation (280-315 nm) and chemical pollution are two factors that have become increasingly important as contributing to amphibian mortality and, perhaps, to amphibian population declines. Therefore, we studied the

Audrey C. Hatch; Andrew R. Blaustein

2003-01-01

433

Association of amphibians with attenuation of ultraviolet-b radiation in montane ponds  

Microsoft Academic Search

Ambient ultraviolet-b (UV-B) radiation (280-320 nm) has increased at north-temperate latitudes in the last two decades. UV-B can be detrimental to amphibians, and amphibians have shown declines in some areas during this same period. We documented the distribution of amphibians and salmonids in 42 remote, subalpine and alpine ponds in Olympic National Park, Washington, United States. We inferred relative exposure

Michael J. Adams; Daniel E. Schindler; Bruce R. Bury

2001-01-01

434

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

435

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

436

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

437

South Asian amphibians: taxonomy, diversity and conservation status  

Microsoft Academic Search

The global conservation crisis facing amphibians re- quires regional taxonomic-based assessments of conser- vation status. The current and probable future needs for captive-breeding facilities in zoos and other institutions are revealed by the number, habitat and life-cycle types of threatened candidate species in the region. The geopoli- tical region of South Asia is home to four biodiversity hotspots with very

S. MOLUR

2008-01-01

438

Chytridiomycosis Survey in Wild and Captive Mexican Amphibians  

Microsoft Academic Search

Mexico, a rich country in terms of amphibian diversity, hosts about 375 described species. Population declines have been documented\\u000a for several species where it is evident that their habitat is being destroyed or modified. However, other species which inhabit\\u000a pristine areas are declining as well. It has been suggested that the chytrid fungus Batrachochytrium dendrobatidis\\u000a (B.d.) may be one of

Patricia Frías-Alvarez; Vance T. Vredenburg; Mariel Familiar-López; Joyce E. Longcore; Edna González-Bernal; Georgina Santos-Barrera; Luis Zambrano; Gabriela Parra-Olea

2008-01-01

439

Amphibian glucagon family peptides: potent metabolic regulators in fish hepatocytes  

Microsoft Academic Search

Peptides analogous to glucagon-like peptide-1 (GLP-1) have been isolated from amphibian pancreas and intestine, and their amino acid sequences and cDNA structures elucidated. Just like their mammalian counterpart, these peptides are potent insulinotropins in mammalian pancreatic cells. We show here that these peptides also exert strong glycogenolytic actions when applied to dispersed fish hepatocytes. We compared the potencies of three

Thomas P Mommsen; J. Michael Conlon; David M Irwin

2001-01-01

440

Sensitivity to Urea Fertilization in Three Amphibian Species  

Microsoft Academic Search

Forest fertilization with granular urea is a well-established management practice in many forested regions of the world. We\\u000a hypothesize that chemical forest fertilizers may be affecting forest-dwelling wildlife. In the laboratory, we studied the\\u000a effects of fertilization doses of granular urea on three species of forest-dwelling amphibians (Plethodon vehiculum, Rhyacotriton variegatus, and Taricha granulosa). In avoidance experiments, the three species

A. Marco; D. Cash; L. K. Belden; A. R. Blaustein

2001-01-01

441

Explanation for naturally occurring supernumerary limbs in amphibians.  

PubMed

The occasional occurrence of high frequencies of limb abnormalities, including extra limbs, in natural populations of amphibians has long been a puzzle. In this paper we report the discovery of a population in which such limb abnormalities appear to be caused by a parasitic flatworm (trematode) that uses amphibians as intermediate hosts. The cercarial larval stage of the trematode attacks amphibians, penetrating the skin to form cysts (metacercariae). The cysts are preferentially localized in the cloacal region, including the developing hind limb regions in larvae of both frogs (Hyla regilla) and salamanders (Ambystoma macrodactylum). A wide range of limb abnormalities are seen, including duplicated limb structures ranging from extra digits to several extra whole limbs. We hypothesize that these limb abnormalities result from localized regulatory responses of developing and regenerating limb tissues to mechanical disruption caused by the trematode cysts. We have tested this idea by implanting inert resin beads into developing limb buds of frogs and salamanders. Since this treatment can cause supernumerary limb structures, our hypothesis is sufficient to explain the naturally occurring extra limbs. PMID:2348164

Sessions, S K; Ruth, S B

1990-04-01

442

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

443

Interventions for reducing extinction risk in chytridiomycosis-threatened amphibians.  

PubMed

Wildlife diseases pose an increasing threat to biodiversity and are a major management challenge. A striking example of this threat is the emergence of chytridiomycosis. Despite diagnosis of chytridiomycosis as an important driver of global amphibian declines 15 years ago, researchers have yet to devise effective large-scale management responses other than biosecurity measures to mitigate disease spread and the establishment of disease-free captive assurance colonies prior to or during disease outbreaks. We examined the development of management actions that can be implemented after an epidemic in surviving populations. We developed a conceptual framework with clear interventions to guide experimental management and applied research so that further extinctions of amphibian species threatened by chytridiomycosis might be prevented. Within our framework, there are 2 management approaches: reducing Batrachochytrium dendrobatidis (the fungus that causes chytridiomycosis) in the environment or on amphibians and increasing the capacity of populations to persist despite increased mortality from disease. The latter approach emphasizes that mitigation does not necessarily need to focus on reducing disease-associated mortality. We propose promising management actions that can be implemented and tested based on current knowledge and that include habitat manipulation, antifungal treatments, animal translocation, bioaugmentation, head starting, and selection for resistance. Case studies where these strategies are being implemented will demonstrate their potential to save critically endangered species. PMID:24975971

Scheele, Ben C; Hunter, David A; Grogan, Laura F; Berger, Lee; Kolby, Jon E; McFadden, Michael S; Marantelli, Gerry; Skerratt, Lee F; Driscoll, Don A

2014-10-01

444

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

445

Sensitivity to urea fertilization in three amphibian species.  

PubMed

Forest fertilization with granular urea is a well-established management practice in many forested regions of the world. We hypothesize that chemical forest fertilizers may be affecting forest-dwelling wildlife. In the laboratory, we studied the effects of fertilization doses of granular urea on three species of forest-dwelling amphibians (Plethodon vehiculum, Rhyacotriton variegatus, and Taricha granulosa). In avoidance experiments, the three species avoided a substrate treated with a dose of 225 kg N/ha urea. In toxicity experiments, we exposed amphibians to urea at doses of 225 kg N/ha and 450 kg N/ha for 4 days. The observed effects increased with time and dose, and there were significant differences in sensitivity among the species. Both treatment levels had an acute effect on survival of P. vehiculum and R. variegatus. At 24 h, mortality at the highest dose was 67% for P. vehiculum, and 47% for R. variegatus. In contrast, there was no mortality for T. granulosa at these concentrations. We suggest that environmental levels of urea could be affecting behavior and survival of some amphibians species in fertilized forests. PMID:11443373

Marco, A; Cash, D; Belden, L K; Blaustein, A R

2001-04-01

446

Cardiac performance correlates of relative heart ventricle mass in amphibians.  

PubMed

This study used an in situ heart preparation to analyze the power output and stroke work of spontaneously beating hearts of four anurans (Rhinella marina, Lithobates catesbeianus, Xenopus laevis, Pyxicephalus edulis) and three urodeles (Necturus maculosus, Ambystoma tigrinum, Amphiuma tridactylum) that span a representative range of relative ventricle mass (RVM) found in amphibians. Previous research has documented that RVM correlates with dehydration tolerance and maximal aerobic capacity in amphibians. The power output (mW g(-1) ventricle mass) and stroke work (mJ g(-1) ventricle muscle mass) were independent of RVM and were indistinguishable from previously published results for fish and reptiles. RVM was significantly correlated with maximum power output (P max, mW kg(-1) body mass), stroke volume, cardiac output, afterload pressure (P O) at P max, and preload pressure (P I) at P max. P I at P max and P O at P max also correlated very closely with each other. The increases in both P I and P O at maximal power outputs in large hearts suggest that concomitant increases in blood volume and/or increased modulation of vascular compliance either anatomically or via sympathetic tone on the venous vasculature would be necessary to achieve P max in vivo. Hypotheses for variation in RVM and its concomitant increased P max in amphibians are developed. PMID:23619575

Kluthe, Gregory J; Hillman, Stanley S

2013-08-01

447

Latent inhibition of predator recognition by embryonic amphibians  

PubMed Central

To avoid being captured, prey animals need to be able to distinguish predators from non-predators. Recent studies have shown that amphibians can learn to recognize their future predators while in the egg. Here, we investigated whether amphibians would similarly be able to learn to recognize non-predators while in the egg. We exposed newly laid wood frog eggs to the odour of tiger salamander or a water control daily for 5 days. After hatching, the wood frog larvae were raised for two weeks at which time we tried to condition them to recognize the salamander as a predator. Larvae were exposed to injured conspecific cues paired with salamander odour, a well-established mode of learning for aquatic prey. When subsequently tested for their response to salamander odour, the larvae pre-exposed to water as embryos showed significant anti-predator responses. However, larvae pre-exposed to the salamander odour as embryos showed no learning of the predator, indicating that they had already learned to recognize the salamander as a non-predator. These results indicate that amphibian embryos can (i) learn to recognize stimuli as non-threatening and (ii) remember it for at least two weeks. The widespread ability of prey to learn to recognize non-predators might explain the persistence of injured conspecific cues as a reliable mechanism for learned predator recognition. PMID:19056547

Ferrari, Maud C.O.; Chivers, Douglas P.

2008-01-01

448

Inductive action of epithelium on differentiation of intestinal connective tissue of Xenopus laevis tadpoles during metamorphosis in vitro  

Microsoft Academic Search

The action of the epithelium on differentiation of connective tissue cells of Xenopus small intestine during metamorphosis was investigated by using culture and morphological techniques. Connective tissue fragments isolated from the small intestine at stage 57 were cultivated in the presence or absence of homologous epithelium. In the presence of the epithelium, metamorphic changes in the connective tissue were fully

Atsuko Ishizuya-Oka; Atsumi Shimozawa

1994-01-01

449

http://www.jstor.org Initiation of Metamorphosis in the Pitcher-Plant Mosquito: Effects of Larval Growth History  

E-print Network

http://www.jstor.org Initiation of Metamorphosis in the Pitcher-Plant Mosquito: Effects of Larval., 1995), pp. 2055-2065 Published by: Ecological Society of America Stable URL: http://www.jstor.org/stable/1941680 Accessed: 10/04/2008 21:07 Your use of the JSTOR archive indicates your acceptance of JSTOR

Oregon, University of

450

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

451

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...

452

Transformation & Metamorphosis  

ERIC Educational Resources Information Center

The sculptures of Canadian artist Brian Jungen are a great inspiration for a lesson on creating new forms. Jungen transforms found objects into unique creations without fully concealing their original form or purpose. Frank Stella's sculpture series, including "K.132,2007" made of stainless steel and spray paint, is another great example of…

Lott, Debra

2009-01-01

453

Stellar Metamorphosis:  

NASA Technical Reports Server (NTRS)

[TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae edge-on, where the direct starlight is blocked by the dusty cocoon. Otherwise, the starlight would overwhelm the nebular light, making it very difficult to see the butterfly-shaped nebula. In a few hundred years, intense ultraviolet radiation from the central star will energize the surrounding gas, causing it to glow brightly, and a planetary nebula is born. These observations were made with the Wide Field and Planetary Camera 2 using three filters: yellow-green, blue, and near-infrared. The images were taken in 1997 by Sun Kwok and in 1996 by Matt Bobrowsky. Credits: Sun Kwok and Kate Su (University of Calgary), Bruce Hrivnak (Valparaiso University), and NASA ----------------- The Hubble Space Telescope Sees Remarkable Structure in the Heart of a Planetary Nebula [BOTTOM LEFT AND RIGHT] This Wide Field and Planetary Camera 2 image of NGC 6818 shows two distinct layers of gas (with dust): a spherical outer region and a brighter, vase-shaped interior 'bubble.' Astronomers believe that a fast wind - material propelled by radiation from the hot central star - is creating the inner elongated shape. The central star of the planetary nebula appears as a tiny blue dot. The material in the wind is traveling so fast that it smashes through older, slower-moving stellar debris, causing a 'blowout' at both ends of the bubble (lower right and upper left). This nebula looks like a twin of NGC 3918, another planetary nebula that has been observed by the Hubble telescope. The structure of NGC 3918 is remarkably similar to that of NGC 6818. It has an outer spherical envelope and an inner, brighter, elongated bubble. A fast-moving wind also appears to have created an orifice at one end (bottom right