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Journal of Experimental Zoology. Part... Dec 2018Some hypotheses on the evolution of regeneration in amphibians and reptiles are presented. Amphibian regeneration is derived from metamorphosis present in sarcopterygian...
Some hypotheses on the evolution of regeneration in amphibians and reptiles are presented. Amphibian regeneration is derived from metamorphosis present in sarcopterygian fish and amphibians of the Devonian-Carboniferous. The genetic ability to rebuild organs during metamorphosis was maintained in form of "regeneration" in urodele and anuran tadpoles. Amphibian regeneration may be a consequence of the transition from an aquatic to a terrestrial environment through the evolution of a developmental program for the tadpole stage and replacements of adult organs controlled by the endocrine and immune system. Following metamorphosis, the regeneration program for terrestrial anurans and amniotes was lost or modified, whereas the immune system involved in self-integrity and microbial protection became in charge of regeneration that was replaced by scarring. Among amniotes only lizards regenerate an organ as large and complex as the tail. It is hypothesized that in Permian captorhinids and in Triassic lizards (eosuchians) a regenerative blastema evolved in relation to autotomy, a unique phenomenon present in these reptiles that enhanced survival against the larger predators of the Permian-Mesozoic. Appendage regeneration in amphibians and lizards occurs after the migration of activated mesenchymal and epidermal cells in the wounded areas to form soft and hyaluronate-rich blastemas. Autotomy and production of high hyaluronate levels allows high hydration and immunosuppression, favoring regeneration. It is suggested that a way for regenerative medicine to induce limb regeneration in humans is to develop medical procedures to recreate soft blastemas that can grow, a long and difficult process because it counteracts mammalian evolution toward scarring.
Topics: Amphibians; Animals; Biological Evolution; Extremities; Lizards; Phylogeny; Regeneration
PubMed: 30468307
DOI: 10.1002/jez.b.22835 -
Aquatic Toxicology (Amsterdam,... Jan 2009
Topics: Amphibians; Animals; Periodicals as Topic; Toxicology
PubMed: 19111356
DOI: 10.1016/j.aquatox.2008.11.013 -
Journal of Thermal Biology Aug 2020Understanding the thermal ecology of active amphibians, as well as its relationship with habitat and environmental features, is a central theme in ecology. However, this...
Understanding the thermal ecology of active amphibians, as well as its relationship with habitat and environmental features, is a central theme in ecology. However, this topic has been poorly studied in eastern Himalaya, which is a global biodiversity hotspot. To bridge this gap, we investigated how the body temperatures of active amphibians varied along an elevation gradient in the Arun and Tamor River catchments in eastern Nepal Himalaya in the present study. Amphibian assemblages were sampled from May to July in both 2014 and 2015 using nocturnal time-constrained visual encounter surveys, and the body temperature of each individual was directly measured using a digital infrared thermometer in the field. A combination of linear regression and hierarchical partitioning analyses was used to determine the effects of elevation and environmental variables on the body temperatures of active amphibians. In total, the body temperatures of 599 amphibian individuals belonging to 28 species from six families were recorded. Our results indicated that amphibian body temperature exhibited monotonically declining trends with increasing elevations in eastern Nepal Himalaya. Interestingly, this tread was much more pronounced in subtropical (lowland) areas than in warm and cool temperate regions. Inter- and intraspecies variations in body temperature were large, which can be attributed to distinct habitat utilization among species and the change in vegetation cover in different bioclimatic zones. Among all environmental variables, substrate temperature and water temperature were the best predictors of the amphibian body temperature. Overall, this study revealed amphibian body temperature patterns along an elevation gradient in eastern Nepal Himalaya, which were principally driven by temperature-related environmental factors. We believe our results can provide important information on amphibian physiological traits, which may help ecologists predict their responses to future climate change and formulate protection strategies.
Topics: Altitude; Amphibians; Animals; Biodiversity; Body Temperature; Ecosystem; Nepal; Species Specificity; Temperature
PubMed: 32888558
DOI: 10.1016/j.jtherbio.2020.102653 -
Journal of Wildlife Diseases Oct 2023One of the major threats for the massive loss in global amphibian diversity is chytridiomycosis, caused by chytrid fungi Batrachochytrium dendrobatidis (Bd) and B....
OCCURRENCE OF PATHOGENIC CHYTRID FUNGI BATRACHOCHYTRIUM SALAMANDRIVORANS AND BATRACHOCHYTRIUM DENDROBATIDIS IN THE HONG KONG NEWT (PARAMESOTRITON HONGKONGENSIS) AND OTHER WILD AND IMPORTED AMPHIBIANS IN A SUBTROPICAL ASIAN REGION.
One of the major threats for the massive loss in global amphibian diversity is chytridiomycosis, caused by chytrid fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal). Following its discovery in 2013, Bsal has emerged as a severe threat to the global survival of urodelans. In 2018, a study reported a high prevalence of Bsal (65.6%) in the Hong Kong newts (Paramesotriton hongkongensis, Near Threatened) of a southern China population adjacent to Hong Kong (HK). Uncertainty regarding the Bsal infection status of P. hongkongensis inhabiting HK raised deep concern over the risk of introducing Bsal from that population. We screened the skin swabs from wild individuals of P. hongkongensis, 15 sympatric amphibian species, and 16 imported amphibian species in HK for chytrids. We found that both Bsal and Bd occur in low prevalences in P. hongkongensis (Bsal 1.7%, 5/293; Bd 0.34%, 1/293), Hong Kong cascade frog, Amolops hongkongensis, family Ranidae (Bsal only, 5.26%, 1/19), and Asian common toad, Duttaphrynus melanostictus, family Bufonidae (Bsal only, 5.88%, 1/17), populations of HK, with infected individuals being asymptomatic, suggesting a potential role of these species as reservoirs of Bsal. Conversely, Bd, but not Bsal, was present on 13.2% (9/68) of imported amphibians, indicating a high chytrid introduction risk posed by international amphibian trade. Long-term surveillance of the presence of Bd and Bsal in wild and captive amphibians would be advisable, and we recommend that import and export of nonnative chytrid carriers should be prevented, especially to those regions with amphibian populations naïve to Bd and Bsal.
Topics: Humans; Animals; Batrachochytrium; Chytridiomycota; Hong Kong; Amphibians; Salamandridae; Bufonidae; Ranidae
PubMed: 37768785
DOI: 10.7589/JWD-D-22-00145 -
The Journal of Animal Ecology Dec 2022Nested subset pattern (nestedness) has been raised to explain the distribution of species on islands and habitat fragments for over 60 years. However, previous studies...
Nested subset pattern (nestedness) has been raised to explain the distribution of species on islands and habitat fragments for over 60 years. However, previous studies on nestedness focused on species richness and composition and overlooked the role of species traits and phylogeny in generating and explaining nestedness. To address this gap, we sampled amphibians on 37 land-bridge islands in the largest archipelago of China, the Zhoushan Archipelago, to explore nestedness as well as the underlying causal processes through three facets of diversity, that is, taxonomic, functional and phylogenetic diversity. The taxonomic nestedness was measured through organizing the species incidence matrix to achieve a maximum value, while the functional and phylogenetic nestedness were quantified by incorporating the similarity of species in terms of their ecological traits and phylogeny. We also obtained six island characteristics and seven species traits as predictors of nestedness. Amphibian metacommunities were significantly nested in these three facets of diversity. When relating different predictors to nestedness, island area, habitat diversity and species traits were highly correlated with taxonomic nestedness. Moreover, island area and habitat diversity significantly influenced functional and phylogenetic nestedness. Therefore, the results support the selective extinction and habitat nestedness hypotheses. Interestingly, although we did not observe significant influences of island isolation on taxonomic nestedness, functional and phylogenetic diversities were significantly higher than expected when matrices were ordered by increasing distance to mainland. The result suggests that there are more functionally and phylogenetically diverse species on less-isolated islands, reflecting a selective colonization process overlooked by the traditional analysis of taxonomic nestedness. Although the three facets of nestedness and underlying processes were largely congruent, we detected the distance-related functional and phylogenetic nestedness for amphibian assemblages. Therefore, we highlight that a framework that simultaneously considers taxonomic, functional and phylogenetic nestedness can contribute to a complementary understanding of nestedness processes. In addition, it also improves our ability to conserve insular biodiversity from different perspectives.
Topics: Animals; China; Phylogeny; Amphibians; Ecosystem; Animal Distribution; Species Specificity
PubMed: 36260356
DOI: 10.1111/1365-2656.13824 -
Scientific Reports Dec 2020Understanding the occurrence and consequence of co-infections can be useful in designing disease management interventions. Amphibians are the most highly threatened...
Understanding the occurrence and consequence of co-infections can be useful in designing disease management interventions. Amphibians are the most highly threatened vertebrates, and emerging pathogens are a serious threat to their conservation. The amphibian chytrid fungus and the viruses of the Ranavirus genus are already widely distributed, causing disease outbreaks and population declines worldwide. However, we lack information about the occurrence and consequences of coinfection with these pathogens across age-classes of amphibian hosts. Here, we analyze the occurrence of infection of the amphibian chytrid fungus and ranaviruses during one season in two susceptible amphibian species at two different locations at which outbreaks have occurred. We found that the co-occurrence of both pathogens in a particular host is not common except in highly susceptible life-stages, and that single infections are the most common situation. Moreover, we found that the occurrence of one pathogen in a particular host did not predict the occurrence of the other. We attribute these results to the niches in which both pathogens proliferate in amphibian hosts.
Topics: Amphibians; Animals; Batrachochytrium; Coinfection; DNA Virus Infections; Models, Biological; Mycoses; Probability; Ranavirus
PubMed: 33273613
DOI: 10.1038/s41598-020-78196-3 -
Cellular and Molecular Life Sciences :... Jun 1999Amphibians employ a genetic mechanism of sex determination, according to all available information on sex chromosomes or breeding tests. Sex reversal allows breeding... (Review)
Review
Amphibians employ a genetic mechanism of sex determination, according to all available information on sex chromosomes or breeding tests. Sex reversal allows breeding tests to establish which sex is heterogametic and provides an indication of the mechanism of sex determination. Cases of spontaneous and experimental sex reversal (by temperature, hormones or surgery) are reviewed and illustrated by previously unpublished studies on crested newts. These newts respond conventionally to temperature and hormone treatment but provide anomalous results from breeding tests. It is suggested that both the evolution from temperature dependency to a genetic switch and from ZZ/ZW to XX/XY are superimposed on a generally uniform mechanism of sex determination in all vertebrates.
Topics: Amphibians; Animals; Castration; Disorders of Sex Development; Female; Gonadal Steroid Hormones; Gonads; Larva; Male; Sex Determination Processes; Sex Differentiation; Temperature; X Chromosome; Y Chromosome
PubMed: 10412371
DOI: 10.1007/s000180050343 -
Pacific Symposium on Biocomputing.... 2007Herein, we describe our ongoing efforts to develop a robust ontology for amphibian anatomy that accommodates the diversity of anatomical structures present in the group....
Herein, we describe our ongoing efforts to develop a robust ontology for amphibian anatomy that accommodates the diversity of anatomical structures present in the group. We discuss the design and implementation of the project, current resolutions to issues we have encountered, and future enhancements to the ontology. We also comment on future efforts to integrate other data sets via this amphibian anatomical ontology.
Topics: Amphibians; Animals; Computational Biology; Computer Simulation; Models, Anatomic; Semantics; Software
PubMed: 17992749
DOI: No ID Found -
BMC Genomics May 2019Evolution leaves an imprint in species through genetic change. At the molecular level, evolutionary changes can be explored by studying ratios of nucleotide...
BACKGROUND
Evolution leaves an imprint in species through genetic change. At the molecular level, evolutionary changes can be explored by studying ratios of nucleotide substitutions. The interplay among molecular evolution, derived phenotypes, and ecological ranges can provide insights into adaptive radiations. Caecilians (order Gymnophiona), probably the least known of the major lineages of vertebrates, are limbless tropical amphibians, with adults of most species burrowing in soils (fossoriality). This enigmatic order of amphibians are very distinct phenotypically from other extant amphibians and likely from the ancestor of Lissamphibia, but little to nothing is known about the molecular changes underpinning their radiation. We hypothesised that colonization of various depths of tropical soils and of freshwater habitats presented new ecological opportunities to caecilians.
RESULTS
A total of 8540 candidate groups of orthologous genes from transcriptomic data of five species of caecilian amphibians and the genome of the frog Xenopus tropicalis were analysed in order to investigate the genetic machinery behind caecilian diversification. We found a total of 168 protein-coding genes with signatures of positive selection at different evolutionary times during the radiation of caecilians. The majority of these genes were related to functional elements of the cell membrane and extracellular matrix with expression in several different tissues. The first colonization of the tropical soils was connected to the largest number of protein-coding genes under positive selection in our analysis. From the results of our study, we highlighted molecular changes in genes involved in perception, reduction-oxidation processes, and aging that likely were involved in the adaptation to different soil strata.
CONCLUSIONS
The genes inferred to have been under positive selection provide valuable insights into caecilian evolution, potentially underpin adaptations of caecilians to their extreme environments, and contribute to a better understanding of fossorial adaptations and molecular evolution in vertebrates.
Topics: Amphibian Proteins; Amphibians; Animals; Evolution, Molecular; Genome; Molecular Sequence Annotation; Phenotype; Phylogeny; Radiation Effects; Selection, Genetic
PubMed: 31072350
DOI: 10.1186/s12864-019-5694-1 -
International Review of Cytology 1993
Review
Topics: Adrenal Cortex Hormones; Amino Acid Sequence; Amphibians; Animals; Growth Hormone; Hormones; Metamorphosis, Biological; Molecular Sequence Data; Pituitary Hormones; Prolactin; Rana catesbeiana; Sequence Homology, Amino Acid; Thyroid Hormones
PubMed: 8500980
DOI: 10.1016/s0074-7696(08)60426-x