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Experientia May 1973
Review
Topics: Amphibians; Animals; Anura; Bufonidae; Cell Division; Culture Media; Extremities; Gonads; Heart; Intestines; Kidney; Larva; Lens, Crystalline; Liver; Lung; Metamorphosis, Biological; Methods; Organ Culture Techniques; Pancreas; Regeneration; Skin; Spleen; Tail; Urodela; Xenopus
PubMed: 4580890
DOI: 10.1007/BF01913222 -
The Influence of Habitat and Phylogeny on the Skin Microbiome of Amphibians in Guatemala and Mexico.Microbial Ecology Jul 2019Microbial symbionts are increasingly recognized as playing a critical role in organismal health across a wide range of hosts. Amphibians are unique hosts in that their...
Microbial symbionts are increasingly recognized as playing a critical role in organismal health across a wide range of hosts. Amphibians are unique hosts in that their skin helps to regulate the exchange of water, ions, and gases, and it plays an active role in defense against pathogens through the synthesis of anti-microbial peptides. The microbiome of amphibian skin includes a diverse community of bacteria known to defend against pathogens, including the global pandemic lineage of Batrachochytrium dendrobatidis associated with mass amphibian die-offs. The relative influence of host phylogeny and environment in determining the composition of the amphibian skin microbiome remains poorly understood. We collected skin swabs from montane amphibians in Mexico and Guatemala, focusing on two genera of plethodontid salamanders and one genus of frogs. We used high throughput sequencing to characterize the skin bacterial microbiome and tested the impact of phylogeny and habitat on bacterial diversity. Our results show that phylogenetic history strongly influences the diversity and community structure of the total bacterial microbiome at higher taxonomic levels (between orders), but on lower scales (within genera and species), the effect of habitat predominates. These results add to a growing consensus that habitat exerts a strong effect on microbiome structure and composition, particularly at shallow phylogenetic scales.
Topics: Amphibians; Animals; Bacteria; Biodiversity; Guatemala; Mexico; Microbiota; Phylogeny; Skin
PubMed: 30467714
DOI: 10.1007/s00248-018-1288-8 -
PLoS Biology Jan 2022The trade-off between offspring size and number is central to life history strategies. Both the evolutionary gain of parental care or more favorable habitats for...
The trade-off between offspring size and number is central to life history strategies. Both the evolutionary gain of parental care or more favorable habitats for offspring development are predicted to result in fewer, larger offspring. However, despite much research, it remains unclear whether and how different forms of care and habitats drive the evolution of the trade-off. Using data for over 800 amphibian species, we demonstrate that, after controlling for allometry, amphibians with direct development and those that lay eggs in terrestrial environments have larger eggs and smaller clutches, while different care behaviors and adaptations vary in their effects on the trade-off. Specifically, among the 11 care forms we considered at the egg, tadpole and juvenile stage, egg brooding, male egg attendance, and female egg attendance increase egg size; female tadpole attendance and tadpole feeding decrease egg size, while egg brooding, tadpole feeding, male tadpole attendance, and male tadpole transport decrease clutch size. Unlike egg size that shows exceptionally high rates of phenotypic change in just 19 branches of the amphibian phylogeny, clutch size has evolved at exceptionally high rates in 135 branches, indicating episodes of strong selection; egg and tadpole environment, direct development, egg brooding, tadpole feeding, male tadpole attendance, and tadpole transport explain 80% of these events. By explicitly considering diversity in parental care and offspring habitat by stage of offspring development, this study demonstrates that more favorable conditions for offspring development promote the evolution of larger offspring in smaller broods and reveals that the diversity of parental care forms influences the trade-off in more nuanced ways than previously appreciated.
Topics: Amphibians; Animals; Biological Evolution; Body Size; Clutch Size; Ecosystem; Female; Life History Traits; Male; Maternal Behavior; Ovum; Paternal Behavior; Reproduction
PubMed: 34982764
DOI: 10.1371/journal.pbio.3001495 -
DNA Research : An International Journal... Feb 2019RNA sequencing (RNA-seq) has become one of the most powerful tools to unravel the genomic basis of biological adaptation and diversity. Although challenging, RNA-seq is...
RNA sequencing (RNA-seq) has become one of the most powerful tools to unravel the genomic basis of biological adaptation and diversity. Although challenging, RNA-seq is particularly promising for research on non-model, secretive species that cannot be observed in nature easily and therefore remain comparatively understudied. Among such animals, the caecilians (order Gymnophiona) likely constitute the least known group of vertebrates, despite being an old and remarkably distinct lineage of amphibians. Here, we characterize multi-tissue transcriptomes for five species of caecilians that represent a broad level of diversity across the order. We identified vertebrate homologous elements of caecilian functional genes of varying tissue specificity that reveal a great number of unclassified gene families, especially for the skin. We annotated several protein domains for those unknown candidate gene families to investigate their function. We also conducted supertree analyses of a phylogenomic dataset of 1,955 candidate orthologous genes among five caecilian species and other major lineages of vertebrates, with the inferred tree being in agreement with current views of vertebrate evolution and systematics. Our study provides insights into the evolution of vertebrate protein-coding genes, and a basis for future research on the molecular elements underlying the particular biology and adaptations of caecilian amphibians.
Topics: Amphibian Proteins; Amphibians; Animals; Evolution, Molecular; Multigene Family; Phylogeny; Sequence Analysis, Protein; Sequence Analysis, RNA; Transcriptome
PubMed: 30351380
DOI: 10.1093/dnares/dsy034 -
Current Topics in Developmental Biology 2013The timing of metamorphosis is a central amphibian life history trait and is controlled by the interplay of developmental progression, body size and condition, and... (Review)
Review
The timing of metamorphosis is a central amphibian life history trait and is controlled by the interplay of developmental progression, body size and condition, and environmental signals. These different processes and signals are integrated by the neuroendocrine system to regulate production of hormones by the thyroid gland. Thyroid hormone (TH) is the primary morphogen controlling metamorphosis, while corticosteroids (CSs) produced by the interrenal glands synergize with TH to promote metamorphic changes. The actions of TH are modulated by monodeiodinase enzymes expressed in TH target tissues. CSs act by sensitizing tissues to the actions of TH via the upregulation of TH receptors and monodeiodinases. The increase in thyroid gland activity during metamorphosis is controlled by the hypothalamus and pituitary gland. The hypothalamo-pituitary-thyroid and hypothalamo-pituitary-interrenal axes are regulated at multiple levels. Hypothalamic corticotropin-releasing factor (CRF) functions as a common, central regulator of pituitary thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH) secretion in tadpoles. CRF neurons transduce the signals of environmental change (e.g., pond drying, resource availability, etc.) on metamorphic timing by regulating TSH and ACTH secretion, and consequently the production of TH and CS.
Topics: Amphibians; Animals; Environment; Hormones; Metamorphosis, Biological; Neurosecretory Systems; Time Factors
PubMed: 23347520
DOI: 10.1016/B978-0-12-385979-2.00007-1 -
Current Opinion in Neurobiology Dec 2021Recent studies have served to emphasize the unique placement of amphibians, composed of more than 8000 species, in the evolution of the brain. We provide an overview of... (Review)
Review
Recent studies have served to emphasize the unique placement of amphibians, composed of more than 8000 species, in the evolution of the brain. We provide an overview of the three amphibian orders and their respective ecologies, behaviors, and brain anatomy. Studies have probed the origins of independently evolved parental care strategies in frogs and the biophysical principles driving species-specific differences in courtship vocalization patterns. Amphibians are also important models for studying the central control of movement, especially in the context of the vertebrate origin of limb-based locomotion. By highlighting the versatility of amphibians, we hope to see a further adoption of anurans, urodeles, and gymnophionans as model systems for the evolution and neural basis of behavior across vertebrates.
Topics: Amphibians; Animals; Biological Evolution; Brain; Locomotion; Neurobiology; Vertebrates
PubMed: 34481981
DOI: 10.1016/j.conb.2021.07.015 -
Journal of Embryology and Experimental... Nov 1985Recent studies on temporal control of early amphibian development are reviewed. It is becoming clear that the development of an embryo is not timed by a single clock set... (Review)
Review
Recent studies on temporal control of early amphibian development are reviewed. It is becoming clear that the development of an embryo is not timed by a single clock set in motion at fertilization, instead each developmental event seems to be timed by its own clock-like mechanism. The timing of developmental events is rigidly determined within embryonic cells, and usually can not be altered experimentally. One exception, however, is the timing of midblastula transition in amphibian embryos; recent studies have shown that its timing is regulated by the nucleocytoplasmic ratio. Several developmental events, particularly those associated with transcriptional activities, require DNA replication prior to their occurrence, suggesting an intimate relationship between DNA replication cycles and their onset. On the other hand, there are many other developmental events where timing is not controlled by the number of cell divisions, DNA replication cycles, or the nucleocytoplasmic ratio. Cytoplasmic machinery with autonomous oscillatory properties is thought to be involved in the timing of these events.
Topics: Ambystoma; Amphibians; Animals; Biological Clocks; Cell Cycle; DNA Ligases; Fibronectins; Gastrula; Pleurodeles; RNA, Ribosomal; Time Factors; Xenopus
PubMed: 3913734
DOI: No ID Found -
Communications Biology Jan 2021Impacts on ecosystems and biodiversity are a prominent area of research in climate change. However, little is known about the effects of abrupt climate change and...
Impacts on ecosystems and biodiversity are a prominent area of research in climate change. However, little is known about the effects of abrupt climate change and climate catastrophes on them. The probability of occurrence of such events is largely unknown but the associated risks could be large enough to influence global climate policy. Amphibians are indicators of ecosystems' health and particularly sensitive to novel climate conditions. Using state-of-the-art climate model simulations, we present a global assessment of the effects of unabated global warming and a collapse of the Atlantic meridional overturning circulation (AMOC) on the distribution of 2509 amphibian species across six biogeographical realms and extinction risk categories. Global warming impacts are severe and strongly enhanced by additional and substantial AMOC weakening, showing tipping point behavior for many amphibian species. Further declines in climatically suitable areas are projected across multiple clades, and biogeographical regions. Species loss in regional assemblages is extensive across regions, with Neotropical, Nearctic and Palearctic regions being most affected. Results underline the need to expand existing knowledge about the consequences of climate catastrophes on human and natural systems to properly assess the risks of unabated warming and the benefits of active mitigation strategies.
Topics: Amphibians; Animals; Computer Simulation; Databases, Factual; Ecosystem; Endangered Species; Environmental Monitoring; Extinction, Biological; Global Warming; Ice; Models, Theoretical; Population Density; Temperature; Water Movements
PubMed: 33514877
DOI: 10.1038/s42003-021-01665-6 -
Seminars in Cell & Developmental Biology Jun 2010Ontogenetic series of extinct taxa are extremely rare and when preserved often incomplete and difficult to interpret. However, the fossil record of amphibians includes a... (Review)
Review
Ontogenetic series of extinct taxa are extremely rare and when preserved often incomplete and difficult to interpret. However, the fossil record of amphibians includes a number of well-preserved ontogenetic sequences for temnospondyl and lepospondyl taxa, which have provided valuable information about the development of these extinct groups. Here we summarize the current knowledge on fossil ontogenies of amphibians, their potential and limitations for relationship assessments, and discuss the insights they have provided for our understanding of the anatomy, life history, and ecology of extinct amphibians.
Topics: Amphibians; Animals; Biological Evolution; Bone and Bones; Fossils; Metamorphosis, Biological; Phylogeny; Skeleton
PubMed: 19913630
DOI: 10.1016/j.semcdb.2009.11.001 -
Science (New York, N.Y.) Sep 2022
Topics: Amphibians; Animals; Classification; Genomics
PubMed: 36108017
DOI: 10.1126/science.ade5002