Amphibians Research Articles

Amphibians: threats and conservation

Click to increase image sizeClick to decrease image sizeKeywords: AmphibiansConservation strategies

"Canadian Skin and Scales: A Complete Encyclopedia of Canadian Amphibians and Reptiles" by Pat E. Bumstead [book review

"Canadian Skin and Scales: A Complete Encyclopedia of Canadian Amphibians and Reptiles" by Pat E. Bumstead [book review

The ontogeny and physiology confirms the dual nature of sleep states

In the Jouvet's laboratory, as early as 1960 the study of the ontogenesis of paradoxical sleep (PS) named "sleep 'with jerks" began in the kitten and led to the first publication in 1961. Then, several species were studied, lamb, rat, human neonates, etc. These works showed that at birth sleep with jerks was preponderant in altricial (immature) species (cat, rat) and the first to appear during the second half of gestation in precocious species (guinea pig). For Jouvet, sleep with jerks is a immature form of PS. Why PS is so important at birth? The maturation of the central nervous system, based on the myelinization, starts in the spinal cord then forwards to the brainstem and forebrain. So, PS mechanisms located in the brainstem are the first to mature and the only one to function. Then the slow wave sleep (SWS) and waking structures become mature. Phylogenetic studies showed that in mammals and birds PS was present even in marsupials and monotremes. Until now only the one exception is the dolphin with a voluntary breathing. To sleep and breath, dolphin has developed an unilateral sleep without classical PS. In other animals, reptiles, amphibians, fishes, PS was not observed with the parameters used in mammals. The study at birth (not yet done) of reptiles would allow perhaps the observation of a temporary PS. Based on these findings, a schematic model of the sleep regulation can be elaborated. Haeckel's aphorism "Ontogeny recapitulates phylogeny" seems true for PS which appears in birds and mammals i.e. at the end of evolution as it appears at the end of gestation when PS cerebral structures are present and mature.

The p53-induced Wig-1 zinc finger protein is highly conserved from fish to man.

The p53-induced wig-1 gene encodes an unusual nuclear zinc finger protein with high sequence similarity between human, rat and mouse. Wig-1 belongs to a group of proteins with widely spaced zinc fingers that bind double stranded (ds) RNA. We show here that wig-1 is present in Gallus gallus (chicken), Silurana tropicalis (frog) and Fugu rubripes (fish) by assembly of EST sequence data from a range of data bases into putative cDNAs. The zinc finger regions of Wig-1 are almost completely conserved from fish to man. A short upstream open reading frame is conserved in mammals and birds but not in amphibians. Sequence information from clones of Macaca mulatta (Rhesus macaque), Sus scrofa (pig), Danio rerio (Zebra fish) and Tetraodon nigroviridis (fresh water puffer fish) indicates that Wig-1 orthologs exist also in these species. No genes with striking similarities to wig-1 were found in invertebrates. Our results suggest that Wig-1 and particularly the zinc finger domains have an important biological function in the p53 pathway in vertebrates.

Neurotrophin and Trk receptor-like immunoreactivity in the frog gastrointestinal tract.

Nerve growth factor (NGF), brain derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) are members of the neurotrophin family, which is involved in the differentiation, growth, repair, plasticity and maintenance of many neuronal populations. They act through three tyrosin-kinase (Trk) specific receptors: NGF bind to TrkA, BDNF to TrkB and NT3 to TrkC. Despite increasing evidence regarding the presence of neurotrophin and their receptors in many vertebrate species, in amphibians there are very few data concerning them. Thus, the aim of this study was to extend the investigation to the presence of both neurotrophins and their Trk receptors in the gut of an anuran amphibian, Rana temporaria. In the frog gut NT-3- like immunoreactivity (IR) was observed in both the nervous system and endocrine cells of the stomach and intestine, while NGF-like IR was observed only in the enteric nervous system, and BDNF-like IR in the intestinal endocrine cells. TrkA- and TrkB-like IR was detected in both neurons and endocrine cells of the intestine, while TrkC-like IR was observed only in intestinal neurons. No Trk IR was detected in the stomach. The occurrence of the IR to neurotrophins and their receptors in the gut of the frog further confirms the well-conserved presence of this family of growth factors and Trk receptors during the evolution of vertebrates and suggests their complex involvement in the biology of the gastrointestinal neuro-endocrine system.

Naturalized reptiles and amphibians of the world

Naturalized reptiles and amphibians of the world

Declining amphibian populations: The pitfalls of count data in the study of diversity, distributions, dynamics, and demography

Most data used in the study of the demography, dynamics, distributions, diversity, and declines of amphibians are count data that are not adjusted for detection probabilities, which are generally variable and low. Such unadjusted count data are unreliable for understanding amphibian ecology, amphibian declines, or when developing conservation and management strategies. In the future, detection probabilities should be estimated and counts adjusted accordingly. This could be achieved by using capture-mark-recapture, distance sampling or novel Bayesian methods.

Society for the Study of Amphibians and Reptiles: Benefit Auction

Society for the Study of Amphibians and Reptiles: Benefit Auction

"Firefly Encyclopedia of Reptiles and Amphibians" edited by Tim Halliday and Kraig Adler. 2002. [book review

"Firefly Encyclopedia of Reptiles and Amphibians" edited by Tim Halliday and Kraig Adler. 2002. [book review

The Complexity of Deformed Amphibians

The Complexity of Deformed Amphibians

Association of Reptilian and Amphibian Veterinarians

Association of Reptilian and Amphibian Veterinarians

Studying Amphibians and Reptiles

Studying Amphibians and Reptiles

The role of call frequency modulation and the auditory papillae in phonotactic behavior in a dart-poison frog

Territorial males of the Brilliant-thighed dart-poison frog, Epipedobates femoralis, are known to present stereotypic phonotactic responses to the playback of conspecific and synthetic calls. Fixed site attachment and a long calling period within an environment of little microclimatic changes render this terrestrial and diurnal pan-Amazonian species a rewarding subject for frog bioacoustics. In field experiments at Aratai, French Guiana, we tested whether the prominent frequency modulation of the advertisement call notes is critical for eliciting phonotactic response. Substitution of the natural upward sweep by either a pure tone within the species frequency range or a reverse sweep did not alter the males’ phonotactic behavior. Playbacks with advertisement calls embedded in high levels of either low-pass or high-pass masking noise designed to saturate either the amphibian (AP) or basilar papilla (BP) showed that male phonotactic behavior in this species is subserved by activation of the BP rather than the AP of the inner ear. [Work supported by grants from Austrian Science Foundation P 11565, P 15345 (WH), and NIH (PMN).]

On the Future of Florida Biodiversity: Threats from an Exotic Amphibian

On the Future of Florida Biodiversity: Threats from an Exotic Amphibian

Amphibians and reptiles of Pennsylvania and the Northeast

Amphibians and reptiles of Pennsylvania and the Northeast

SKELETAL AND DENTAL ONTOGENY IN THE LONG-TAILED CLAWED SALAMANDER, Onychodactylus fischeri (URODELA: HYNOBIIDAE)

Skull, hyobranchial, and dental ontogeny of Onychodactylus fischeri (Hynobiidae) is described based on a developmental series ranging from early larvae to old postmetamorphic animals. If compared with other hynobiids ( Ranodon sibiricus and Salamandrella keyserlingii ), larvae of O. fischeri display the underdevelopment of certain larval specific features: e.g., the coronoid is edentate and occurs as a tiny bone only in the earliest larvae; the «Zahnfeld» on the vomer and palatine is absent, the palatine portion of the palatopterygoid is reduced. On the other hand, adult postmetamorphic O. fischeri specimens show the underdeveloped cranial and postcranial skeletal features in comparison with adult R. sibiricus and S. keyserlingii . Two phenomena seem to account for the abbreviation of the ontogenetic trajectory in O. fischeri . First, in O. fischeri which has the largest eggs among hynobiids, the initial larval development appears to have been shifted into the embryonic period (embryonalization which is accompanied in amphibians by the reduction or loss of certain larval specific features). Second, paedomorphosis caused by the retarded rate of somatic development in O. fischeri appears to have resulted in the loss or reduction of features that appear later in R. sibiricus and S. keyserlingii and, likely, in the ancestral ontogeny.

Amphibians and reptiles of Pennsylvania and the Northeast

Amphibians and reptiles of Pennsylvania and the Northeast

Nondestructive indices of trace element exposure in squamate reptiles

Compared with birds, mammals, fish, and even amphibians, very little is known about the effects of contaminants on reptiles. Recent evidence that many reptile populations may be declining has stimulated demand for toxicological studies of reptiles as well as development of nondestructive sampling techniques useful for assessing and monitoring contaminant exposure. The current study experimentally evaluated the utility of shed skins, tail clips, and blood samples as nondestructive indices of trace element exposure in banded water snakes, Nerodia fasciata. For 13.5 months, snakes were either fed fish from a coal ash-contaminated site or uncontaminated food from a reference site. Snakes fed contaminated prey accumulated As, Cd, Se, Sr, and V in various organs (i.e. liver, kidney, and/or gonads). Moreover, non-parametric discriminant function analysis revealed that snakes could be placed in two groups that reliably reflected their experimental diet based upon Se, Sr, and As concentrations in tail clips, blood, and/or shed skins. We suggest that nondestructive sampling techniques, particularly analyses of blood and tail clips, may be easily applied in evaluations of contaminant exposure in the field and laboratory and may prevent excessive destructive sampling of potentially threatened reptile species.

Transfer of a Pathogen from Fish to Amphibians

Abstract:Ecological studies of exotic species focus primarily on how invaders directly affect particular resident species. In contrast, little is known about the indirect effects of introduced species on native communities, including how pathogens may be spread by introduced species. We provide evidence suggesting that introduced fish may serve as a vector for a pathogenic oomycete,Saprolegnia ferax, that has been associated with embryonic mortality of amphibians in the Cascade Mountains of Oregon, U.S.A. In laboratory experiments, mortality induced byS. feraxwas greater in western toad ( Bufo boreas) embryos exposed directly to hatchery‐reared rainbow trout (Oncorhynchus mykiss) experimentally infected withS. feraxand hatchery‐reared trout not experimentally infected than in control embryos. Embryos also developed significantS. feraxinfections when raised on soil that was exposed to trout experimentally infected withS. ferax. Furthermore, toad embryos exposed toS. feraxisolated from sites whereSaprolegniaoutbreaks are common experienced higher mortality than embryos exposed toS. feraxisolated from sites whereSaprolegniaoutbreaks have not occurred. Given the widespread practice of introducing hatchery‐reared fishes, we suggest that fish used in stocking programs could be an important vector for diseases responsible for amphibian losses.

Amphibians: the world of frogs, toads, salamanders and newts

Amphibians: the world of frogs, toads, salamanders and newts