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Sexual Development : Genetics,... 2016Amphibians have been widely used to study developmental biology due to the fact that embryo development takes place independently of the maternal organism and that... (Review)
Review
Amphibians have been widely used to study developmental biology due to the fact that embryo development takes place independently of the maternal organism and that observations and experimental approaches are easy. Some amphibians like Xenopus became model organisms in this field. In the first part of this article, the differentiation of the gonads in amphibians and the mechanisms governing this process are reviewed. In the second part, the state of the art about sex reversal, which can be induced by steroid hormones in general and by temperature in some species, is presented. Also information about pollutants found in the environment that could interfere with the development of the amphibian reproductive apparatus or with their reproductive physiology is given. Such compounds could play a part in the amphibian decline, since in the wild, many amphibians are endangered species.
Topics: Amphibians; Animals; Disorders of Sex Development; Gonads; Reproduction; Sex Differentiation
PubMed: 27648840
DOI: 10.1159/000448797 -
Genes Apr 2021Sex is determined genetically in amphibians; however, little is known about the sex chromosomes, testis-determining genes, and the genes involved in testis... (Review)
Review
Sex is determined genetically in amphibians; however, little is known about the sex chromosomes, testis-determining genes, and the genes involved in testis differentiation in this class. Certain inherent characteristics of the species of this group, like the homomorphic sex chromosomes, the high diversity of the sex-determining mechanisms, or the existence of polyploids, may hinder the design of experiments when studying how the gonads can differentiate. Even so, other features, like their external development or the possibility of inducing sex reversal by external treatments, can be helpful. This review summarizes the current knowledge on amphibian sex determination, gonadal development, and testis differentiation. The analysis of this information, compared with the information available for other vertebrate groups, allows us to identify the evolutionarily conserved and divergent pathways involved in testis differentiation. Overall, the data confirm the previous observations in other vertebrates-the morphology of the adult testis is similar across different groups; however, the male-determining signal and the genetic networks involved in testis differentiation are not evolutionarily conserved.
Topics: Amphibians; Animals; Cell Differentiation; Male; Polyploidy; Sex Determination Processes; Testis
PubMed: 33923451
DOI: 10.3390/genes12040578 -
Genes Aug 2019In this contribution, the aspects of reptile and amphibian speciation that emerged from research performed over the past decade are reviewed. First, this study assesses... (Review)
Review
In this contribution, the aspects of reptile and amphibian speciation that emerged from research performed over the past decade are reviewed. First, this study assesses how patterns and processes of speciation depend on knowing the taxonomy of the group in question, and discuss how integrative taxonomy has contributed to speciation research in these groups. This study then reviews the research on different aspects of speciation in reptiles and amphibians, including biogeography and climatic niches, ecological speciation, the relationship between speciation rates and phenotypic traits, and genetics and genomics. Further, several case studies of speciation in reptiles and amphibians that exemplify many of these themes are discussed. These include studies of integrative taxonomy and biogeography in South American lizards, ecological speciation in European salamanders, speciation and phenotypic evolution in frogs and lizards. The final case study combines genomics and biogeography in tortoises. The field of amphibian and reptile speciation research has steadily moved forward from the assessment of geographic and ecological aspects, to incorporating other dimensions of speciation, such as genetic mechanisms and evolutionary forces. A higher degree of integration among all these dimensions emerges as a goal for future research.
Topics: Amphibians; Animals; Ecosystem; Evolution, Molecular; Genetic Speciation; Reptiles; Selection, Genetic
PubMed: 31455040
DOI: 10.3390/genes10090646 -
Nature Reviews. Microbiology Jun 2020Discovering that chytrid fungi cause chytridiomycosis in amphibians represented a paradigm shift in our understanding of how emerging infectious diseases contribute to... (Review)
Review
Discovering that chytrid fungi cause chytridiomycosis in amphibians represented a paradigm shift in our understanding of how emerging infectious diseases contribute to global patterns of biodiversity loss. In this Review we describe how the use of multidisciplinary biological approaches has been essential to pinpointing the origins of amphibian-parasitizing chytrid fungi, including Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans, as well as to timing their emergence, tracking their cycles of expansion and identifying the core mechanisms that underpin their pathogenicity. We discuss the development of the experimental methods and bioinformatics toolkits that have provided a fuller understanding of batrachochytrid biology and informed policy and control measures.
Topics: Amphibians; Animals; Biodiversity; Chytridiomycota; Genotype; Population Dynamics; Recombination, Genetic; Time Factors; Virulence
PubMed: 32099078
DOI: 10.1038/s41579-020-0335-x -
Developmental and Comparative Immunology Jan 2017Like all other vertebrate groups, amphibian responses to the environment are mediated through the brain (hypothalamic)-pituitary-adrenal/interrenal (HPA/I) axis and the... (Review)
Review
Like all other vertebrate groups, amphibian responses to the environment are mediated through the brain (hypothalamic)-pituitary-adrenal/interrenal (HPA/I) axis and the sympathetic nervous system. Amphibians are facing historically unprecedented environmental stress due to climate change that will involve unpredictable temperature and rainfall regimes and possible nutritional deficits due to extremes of temperature and drought. At the same time, amphibians in all parts of the world are experiencing unprecedented declines due to the emerging diseases, chytridiomycosis (caused by Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans) and ranavirus diseases due to viruses of the genus Ranavirus in the family Iridoviridae. Other pathogens and parasites also afflict amphibians, but here I will limit myself to a review of recent literature linking stress and these emerging diseases (chytridiomycosis and ranavirus disease) in order to better predict how environmental stressors and disease will affect global amphibian populations.
Topics: Amphibians; Animals; Chytridiomycota; Climate Change; Humans; Hypothalamo-Hypophyseal System; Immune System; Immunity, Innate; Pituitary-Adrenal System; Ranavirus; Stress, Physiological
PubMed: 27387153
DOI: 10.1016/j.dci.2016.07.002 -
Development, Growth & Differentiation Aug 2022
Topics: Amphibians; Animals
PubMed: 36088539
DOI: 10.1111/dgd.12805 -
Development, Growth & Differentiation Dec 2022
Topics: Animals; Amphibians
PubMed: 36579413
DOI: 10.1111/dgd.12829 -
Biological Reviews of the Cambridge... Aug 2016Despite the ubiquitous nature of sleep, its functions remain a mystery. In an attempt to address this, many researchers have studied behavioural and electrophysiological... (Review)
Review
Despite the ubiquitous nature of sleep, its functions remain a mystery. In an attempt to address this, many researchers have studied behavioural and electrophysiological phenomena associated with sleep in a diversity of animals. The great majority of vertebrates and invertebrates display a phase of immobility that could be considered as a sort of sleep. Terrestrial mammals and birds, both homeotherms, show two sleep states with distinct behavioural and electrophysiological features. However, whether these features have evolved independently in each clade or were inherited from a common ancestor remains unknown. Unfortunately, amphibians and reptiles, key taxa in understanding the evolution of sleep given their position at the base of the tetrapod and amniote tree, respectively, remain poorly studied in the context of sleep. This review presents an overview of what is known about sleep in amphibians and reptiles and uses the existing data to provide a preliminary analysis of the evolution of behavioural and electrophysiological features of sleep in amphibians and reptiles. We also discuss the problems associated with analysing existing data, as well as the difficulty in inferring homologies of sleep stages based on limited data in the context of an essentially mammalian-centric definition of sleep. Finally, we highlight the importance of developing comparative approaches to sleep research that may benefit from the great diversity of species with different ecologies and morphologies in order to understand the evolution and functions of sleep.
Topics: Amphibians; Animals; Biological Evolution; Reptiles; Sleep
PubMed: 26031314
DOI: 10.1111/brv.12197 -
Development, Growth & Differentiation Oct 2023
Topics: Animals; Amphibians
PubMed: 37881023
DOI: 10.1111/dgd.12889 -
Development, Growth & Differentiation Jan 2023
Topics: Animals; Amphibians; Models, Animal
PubMed: 36740732
DOI: 10.1111/dgd.12838