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ILAR Journal 2007Amphibians are most notably characterized by their glandular skin, which they shed regularly and ingest routinely. It is advisable to handle amphibians only with... (Review)
Review
Amphibians are most notably characterized by their glandular skin, which they shed regularly and ingest routinely. It is advisable to handle amphibians only with protective gloves to avoid damaging their skin. These animals absorb water readily across the skin as a means of maintaining hydration. They also easily absorb drugs and anesthetics that are applied directly to the skin. Investigators commonly utilize cutaneous respiration in amphibians and evaluate skin abnormalities via wet mount preparations, skin scrapes, and biopsy. The examination of blood samples can be useful in evaluating the status of ill amphibians, although the similarity in function of amphibian blood cell types and those of other species is largely unknown. If surgery is required, it is necessary to fast the animals before surgery, and to monitor their hydration. The wet environment required for amphibian surgery makes sterile technique challenging, and it is advisable to institute prophylactic antibiotic therapy before the procedure. The anesthetic of choice for amphibian surgery is tricaine methanesulfonate (MS-222). Postoperative recommendations include fluids, nutritional support if necessary, and analgesia. If euthanasia is required, MS-222 overdose or pentobarbital injection are the preferred methods.
Topics: Aminobenzoates; Amphibians; Anesthetics; Animal Diseases; Animals; Euthanasia, Animal; Female; Male; Skin Absorption; Surgical Procedures, Operative
PubMed: 17592187
DOI: 10.1093/ilar.48.3.255 -
Journal of Comparative Physiology. A,... Oct 2010Pheromonal communication is widespread in salamanders and newts and may also be important in some frogs and toads. Several amphibian pheromones have been behaviorally,... (Review)
Review
Pheromonal communication is widespread in salamanders and newts and may also be important in some frogs and toads. Several amphibian pheromones have been behaviorally, biochemically and molecularly identified. These pheromones are typically peptides or proteins. Study of pheromone evolution in plethodontid salamanders has revealed that courtship pheromones have been subject to continual evolutionary change, perhaps as a result of co-evolution between the pheromonal ligand and its receptor. Pheromones are detected by the vomeronasal organ and main olfactory epithelium. Chemosensory neurons express vomeronasal receptors or olfactory receptors. Frogs have relatively large numbers of vomeronasal receptors that are transcribed in both the vomeronasal organ and the main olfactory epithelium. Salamander vomeronasal receptors apparently are restricted to the vomeronasal organ. To date, no chemosensory ligands have been matched to vomeronasal receptors or olfactory receptors so it is unknown whether particular receptor types are (1) specialized for detection of pheromones versus other chemosignals, or (2) specialized for detection of volatile, nonvolatile, or water-borne chemosignals. Despite progress in understanding amphibian pheromonal communication, only a small fraction of amphibian species have been examined. Study of additional species of amphibians will indicate which traits related to pheromonal communication are evolutionarily conserved and which traits have diverged over time.
Topics: Amphibians; Animal Communication; Animals; Female; Male; Pheromones; Social Behavior; Species Specificity; Vomeronasal Organ
PubMed: 20526605
DOI: 10.1007/s00359-010-0540-6 -
Biotechnology and Bioengineering Feb 2024In recent years, environmental DNA (eDNA) has received attention from biologists due to its sensitivity, convenience, labor and material efficiency, and lack of damage... (Review)
Review
In recent years, environmental DNA (eDNA) has received attention from biologists due to its sensitivity, convenience, labor and material efficiency, and lack of damage to organisms. The extensive application of eDNA has opened avenues for the monitoring and biodiversity assessment of amphibians, which are frequently small and difficult to observe in the field, in areas such as biodiversity survey assessment and detection of specific, rare and threatened, or alien invasive species. However, the accuracy of eDNA can be influenced by factors such as ambient temperature, pH, and false positives or false negatives, which makes eDNA an adjunctive tool rather than a replacement for traditional surveys. This review provides a concise overview of the eDNA method and its workflow, summarizes the differences between applying eDNA for detecting amphibians and other organisms, reviews the research progress in eDNA technology for amphibian monitoring, identifies factors influencing detection efficiency, and discusses the challenges and prospects of eDNA. It aims to serve as a reference for future research on the application of eDNA in amphibian detection.
Topics: Animals; DNA, Environmental; Ecosystem; Amphibians; Biodiversity
PubMed: 37986625
DOI: 10.1002/bit.28592 -
Molecular Reproduction and Development Oct 2019It is a widely held belief that environmental contaminants contribute to the decline of amphibian populations. By spending most of their early life in water and later... (Review)
Review
It is a widely held belief that environmental contaminants contribute to the decline of amphibian populations. By spending most of their early life in water and later stages on the land, amphibians face a constant risk of exposure to pesticides and other chemical pollutants in both aquatic and terrestrial environments. This review presents an overview of the studies carried out in Italian amphibians to highlight hazardous effects of bioaccumulation of chemical pollutants in juveniles and adults in various contaminated environments. Further, the studies in the laboratory setting assessing the effects of chemical pollutants on reproductive and developmental processes are reported. These studies and their relative references have been summarized in a tabular form. Three prominent contaminant groups were identified: herbicides, insecticides, and fungicides; and only a few works reported the effects of other chemical pollutants. Each pollutant group has been delegated to a section. All through the literature survey, it is seen that interest in this topic in Italy is very recent and sparse, where only a few anuran and caudata species and only some chemical pollutants have been studied.
Topics: Amphibians; Animals; Environmental Pollutants; Italy; Life Cycle Stages; Pesticides; Reproduction
PubMed: 31111596
DOI: 10.1002/mrd.23165 -
Viruses Nov 2011Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in... (Review)
Review
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.
Topics: Amphibians; Animals; DNA Virus Infections; Ranavirus; Virulence
PubMed: 22163349
DOI: 10.3390/v3112351 -
Alternatives To Laboratory Animals :... Oct 2007While spontaneous tumours may occasionally develop in inbred and isogenic strains of Xenopus laevis, the South African clawed toad, they are extremely rare in natural... (Review)
Review
While spontaneous tumours may occasionally develop in inbred and isogenic strains of Xenopus laevis, the South African clawed toad, they are extremely rare in natural and laboratory populations. Only two amphibian neoplasms, the renal adenocarcinoma of Rana pipiens and the lymphosarcoma of Xenopus laevis, have been extensively explored. Amphibians are resistant to the development of neoplasia, even following exposure to "direct-acting" chemical carcinogens such as N-methyl-N-nitrosourea, that are highly lymphotoxic, thus diminishing immune reactivity. Regenerative capacity in adults, and a dramatic metamorphosis which remodels much of the larval body to produce the adult form, are unique to amphibian vertebrates, and the control mechanisms involved may protect against cancer. For example, naturally rising corticosteroid titres during metamorphosis will impair some T-cell functions, and the removal of T-regulatory (suppressor) functions inhibits the induction of altered-self tolerance. Altered-self tolerance is not as effectively induced in adult Xenopus laevis as in mammals, so cancer cells with new antigenicity are more likely be rejected in amphibians. Amphibian immunocytes tend to undergo apoptosis readily in vitro, and, unlike mammalian immunocytes, undergo apoptosis without entering the cell cycle. Cells not in the cell cycle that die from nuclear damage (apoptosis), will have no opportunity to express genetic instability leading to cell transformation. We suggest that all these factors, rather than any one of them, may reduce susceptibility to cancer in amphibians.
Topics: Amphibians; Animals; Apoptosis; DNA Damage; DNA Repair; Neoplasms; Self Tolerance
PubMed: 18001168
DOI: 10.1177/026119290703500514 -
Journal of Genetics Dec 2019Amphibians show a very high level of diversity and endemism and are facing global declines from the past few decades. Studies have shown that the molecular tools can be... (Review)
Review
Amphibians show a very high level of diversity and endemism and are facing global declines from the past few decades. Studies have shown that the molecular tools can be helpful in their conservation efforts. In India, more than 80% of amphibians are endemic and most show a narrow range of distribution. Most of the Indian amphibians lack information on their genetic diversity. In this study, were view the overall trend on amphibian studies in India with the specific focus on conservation genetics. Overall, of the 173 studies, only 14 dealt with the conservation of amphibians through genetic tools and five studies estimated the genetic diversity or gene structure. Here, we discuss the gaps and provide future directions on how genetic studies can be helpful in Indian amphibian conservation.
Topics: Amphibians; Animals; Biodiversity; Conservation of Natural Resources; Databases, Factual; Genetic Markers; Genetic Variation; India; Phylogeography; Population Density
PubMed: 31819027
DOI: No ID Found -
Developmental Dynamics : An Official... Dec 2002Recent revisions in the Xenopus laevis fate map led to the designation of the rostral/caudal axis and reassignment of the dorsal/ventral axis (Lane and Smith [1999]... (Review)
Review
Recent revisions in the Xenopus laevis fate map led to the designation of the rostral/caudal axis and reassignment of the dorsal/ventral axis (Lane and Smith [1999] Development 126:423-434; Lane and Sheets [2000] Dev. Biol. 225:37-58). It is unprecedented to reassign primary embryonic axes after many years of research in a model system. In this review, we use insights about vertebrate development from anatomy and comparative embryology, as well as knowledge about gastrulation in frogs, to reexamine several traditional amphibian fate maps. We show that four extant maps contain information on the missing rostral/caudal axis. These maps support the revised map as well as the designation of the rostral/caudal axis and reassignment of the dorsal/ventral axes. To illustrate why it is important for researchers to use the revised map and nomenclature when thinking about frog and fish embryos, we present an example of alternative interpretations of "dorsalized" zebrafish mutations.
Topics: Amphibians; Animals; Body Patterning; Cell Lineage; Embryo, Nonmammalian; Gene Expression Regulation, Developmental; Models, Biological; Xenopus
PubMed: 12454921
DOI: 10.1002/dvdy.10182 -
Viruses Nov 2011Although a variety of virus species can infect amphibians, diseases caused by ranaviruses ([RVs]; Iridoviridae) have become prominent, and are a major concern for... (Review)
Review
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.
Topics: Amphibian Proteins; Amphibians; Animals; DNA Virus Infections; Humans; Ranavirus; Urodela; Xenopus laevis
PubMed: 22163335
DOI: 10.3390/v3112065 -
EcoHealth Sep 2012Understanding linkages between environmental changes and disease emergence in human and wildlife populations represents one of the greatest challenges to ecologists and... (Review)
Review
Understanding linkages between environmental changes and disease emergence in human and wildlife populations represents one of the greatest challenges to ecologists and parasitologists. While there is considerable interest in drivers of amphibian microparasite infections and the resulting consequences, comparatively little research has addressed such questions for amphibian macroparasites. What work has been done in this area has largely focused on nematodes of the genus Rhabdias and on two genera of trematodes (Ribeiroia and Echinostoma). Here, we provide a synopsis of amphibian macroparasites, explore how macroparasites may affect amphibian hosts and populations, and evaluate the significance of these parasites in larger community and ecosystem contexts. In addition, we consider environmental influences on amphibian-macroparasite interactions by exploring contemporary ecological factors known or hypothesized to affect patterns of infection. While some macroparasites of amphibians have direct negative effects on individual hosts, no studies have explicitly examined whether such infections can affect amphibian populations. Moreover, due to their complex life cycles and varying degrees of host specificity, amphibian macroparasites have rich potential as bioindicators of environmental modifications, especially providing insights into changes in food webs. Because of their documented pathologies and value as bioindicators, we emphasize the need for broader investigation of this understudied group, noting that ecological drivers affecting these parasites may also influence disease patterns in other aquatic fauna.
Topics: Amphibians; Animals; Climate Change; Ecosystem; Host-Parasite Interactions; Life Cycle Stages
PubMed: 22810498
DOI: 10.1007/s10393-012-0785-3