-
Current Biology : CB Nov 2018Since the dawn of history, amphibians have been a part of human culture. Western Europeans built fires for cooking and warmth, adding large logs as needed. What...
Since the dawn of history, amphibians have been a part of human culture. Western Europeans built fires for cooking and warmth, adding large logs as needed. What occasionally emerged was astounding: large black animals (which had found shelter in the logs) with four legs and a tail, jet black with striking bright yellow spots. These fire salamanders were variously thought to be the product of the fire itself, or, as Aristotle reported, capable of extinguishing fire. Pliny the Elder is said to have tested this idea by throwing a salamander into flames - the salamander died! - nevertheless the association with fire persisted. Pliny perpetuated other fantastical claims, which spread; even Leonardo da Vinci contributed to the legend, and myths from different regions merged - at one point, asbestos was claimed to be salamander wool. Salamanders were attributed great powers; a single salamander upstream was thought to be sufficient to kill an army. King Francis I. of France chose a salamander as his emblem - a powerful symbol, born of fire, filled with poison, immune from burning, and even able to douse flames. Before the emergence of great cities and conurbations, people grew up surrounded by nature. Salamanders and newts, toads and frogs were all part of normal human experience. Myths such as those surrounding the fire salamanders were commonplace. Shakespeare's witches brewed with an eye of newt and tail of frog. As a child, we raised tadpoles and were taught to shudder at the appearance of a tiger salamander in a root cellar. In general, amphibians are seen as benign and harmless, even helpful as creatures that devour harmful insects and serve as an alternative food source. Thus, it came as a shock to most biologists and to the public at large in the 1980s that amphibians around the world were in decline and that they were at greater risk of extinction as a taxon than any other vertebrate group. A study of every amphibian species known in 2004 showed that on the order of 40% were at high risk of extinction, and by 2008, the decline of amphibians was seen as evidence of an impending sixth mass extinction.
Topics: Amphibians; Animal Distribution; Animals; Biodiversity; Chytridiomycota; Conservation of Natural Resources; Life History Traits; Mycoses
PubMed: 30399342
DOI: 10.1016/j.cub.2018.09.028 -
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 -
Gerontology 1994Limited research findings up-to-date with a few amphibian models do not permit a generalisation of ageing phenomena in the class Amphibia. Short-lived species of... (Comparative Study)
Comparative Study Review
Limited research findings up-to-date with a few amphibian models do not permit a generalisation of ageing phenomena in the class Amphibia. Short-lived species of amphibians show gradual senescence comparable to the pattern seen in laboratory mammals. Long-lived species (mostly urodeles) continue to grow throughout life and are believed to exhibit very slow or negligible senescence which is unobtrusive. In a few species with gradual senescence, there is some evidence of an increase in mortality rate and a decrease in growth rate with advancing age. Increase in cross-linking of collagen, accumulation of age pigments (lipofuscin and melanin), decrease in metabolism and loss of immunocompetence are ageing phenomena common to both amphibians and mammals. On the other hand, persistence of neurogenesis and myogenesis, continuance of oogenesis beyond adult life and polyphyodonty are some of the features peculiar to ageing in amphibians. More authenticated reports are needed to fill up the gaps in our knowledge on amphibian senescence.
Topics: Aging; Amphibians; Animals; Behavior, Animal; Collagen; Female; Longevity; Male; Regeneration; Reproduction
PubMed: 7926854
DOI: 10.1159/000213585 -
Veterinary Clinical Pathology Mar 2017Amphibian declines and extinctions have worsened in the last 2 decades. Partly because one of the main causes of the declines is infectious disease, veterinary... (Review)
Review
Amphibian declines and extinctions have worsened in the last 2 decades. Partly because one of the main causes of the declines is infectious disease, veterinary professionals have increasingly become involved in amphibian research, captive husbandry, and management. Health evaluation of amphibians, free-living or captive, can benefit from employing the tools of clinical pathology, something that is commonly used in veterinary medicine of other vertebrates. The present review compiles what is known of amphibian clinical pathology emphasizing knowledge that may assist with the interpretation of laboratory results, provides diagnostic recommendations for common amphibian diseases, and includes RIs for a few amphibian species estimated based on peer-reviewed studies. We hope to encourage the incorporation of clinical pathology in amphibian practice and research, and to highlight the importance of applying veterinary medicine principles in furthering our knowledge of amphibian pathophysiology.
Topics: Amphibians; Animals; Hematology; Pathology, Clinical; Specimen Handling; Veterinary Medicine
PubMed: 28195641
DOI: 10.1111/vcp.12452 -
Experimental Cell Research Jul 2020Size is a fundamental feature of biology that affects physiology at all levels, from the organism to organs and tissues to cells and subcellular structures. How size is... (Review)
Review
Size is a fundamental feature of biology that affects physiology at all levels, from the organism to organs and tissues to cells and subcellular structures. How size is determined at these different levels, and how biological structures scale to fit together and function properly are important open questions. Historically, amphibian systems have been extremely valuable to describe scaling phenomena, as they occupy some of the extremes in biological size and are amenable to manipulations that alter genome and cell size. More recently, the application of biochemical, biophysical, and embryological techniques to amphibians has provided insight into the molecular mechanisms underlying scaling of subcellular structures to cell size, as well as how perturbation of normal size scaling impacts other aspects of cell and organism physiology.
Topics: Amphibians; Animals; Body Patterning; Body Size; Cell Size; Developmental Biology; Genome; Models, Biological; Organ Size
PubMed: 32343955
DOI: 10.1016/j.yexcr.2020.112036 -
Seminars in Cell & Developmental Biology 2013Amphibians, i.e. salamanders, frogs and caecilians show a wide range of bright colours in combination with contrasting patterns. There is variation among species,... (Review)
Review
Amphibians, i.e. salamanders, frogs and caecilians show a wide range of bright colours in combination with contrasting patterns. There is variation among species, populations and also within species and populations. Furthermore, individuals often change colours during developmental stages or in response to environmental factors. This extraordinary variation means that there are excellent opportunities to test hypotheses of the adaptive significance of colours using amphibian species as models. We review the present view of functions of colouration in amphibians with the main focus on relatively unexplored topics. Variation in colouration has been found to play a role in thermoregulation, UV protection, predator avoidance and sexual signalling. However, many proposed cases of adaptive functions of colouration in amphibians remain virtually scientifically unexplored and surprisingly few genes influencing pigmentation or patterning have been detected. We would like to especially encourage more studies that take advantage of recent developments in measurement of visual properties of several possible signalling receivers (e.g. predators, competitors or mates). Future investigations on interactions between behaviour, ecology and vision have the potential to challenge our current view of the adaptive function of colouration in amphibians.
Topics: Adaptation, Physiological; Amphibians; Animals; Color; Pigmentation
PubMed: 23664831
DOI: 10.1016/j.semcdb.2013.05.004 -
Gerontology 1994The complex life history of many amphibians has been designed to take advantage of the resources of two completely different habitats. The aquatic free-living amphibian... (Comparative Study)
Comparative Study Review
The complex life history of many amphibians has been designed to take advantage of the resources of two completely different habitats. The aquatic free-living amphibian larva is different from the terrestrial adult regarding morphology, physiology and behavioural patterns. Therefore, in the life-time of an individual amphibian, two discontinuous growth stanzas are exhibited. The sigmoid growth model fits well with both stanzas. The rapid growth of the larval amphibian can be described by the double exponential Gompertz equation, whereas the slow growth process of the transformed amphibian can be described by the von Bertalanffy growth model. The bulk of amphibian growth occurs in the terrestrial phase and is not independent of size, age, sex and environmental conditions. The endocrine regulation of growth in amphibians is unique in the sense that the mechanism of pituitary action is different in aquatic and terrestrial phases.
Topics: Aging; Amphibians; Animals; Endocrine Glands; Female; Larva; Male; Models, Biological
PubMed: 7926853
DOI: 10.1159/000213584 -
The Veterinary Clinics of North... Sep 2000This article is an introduction to common amphibian surgical techniques. No overwhelming obstacles preclude incorporating amphibian surgeries into the repertoire of... (Review)
Review
This article is an introduction to common amphibian surgical techniques. No overwhelming obstacles preclude incorporating amphibian surgeries into the repertoire of veterinary clinicians. With the proper tools and reference materials and a little practice, the skills needed may be readily acquired.
Topics: Amphibians; Animals; Surgery, Veterinary
PubMed: 11228929
DOI: 10.1016/s1094-9194(17)30073-7 -
Developmental Neurobiology May 2019Regeneration of lost cells in the central nervous system, especially the brain, is present to varying degrees in different species. In mammals, neuronal cell death often... (Comparative Study)
Comparative Study Review
Regeneration of lost cells in the central nervous system, especially the brain, is present to varying degrees in different species. In mammals, neuronal cell death often leads to glial cell hypertrophy, restricted proliferation, and formation of a gliotic scar, which prevents neuronal regeneration. Conversely, amphibians such as frogs and salamanders and teleost fish possess the astonishing capacity to regenerate lost cells in several regions of their brains. While frogs lose their regenerative abilities after metamorphosis, teleost fish and salamanders are known to possess regenerative competence even throughout adulthood. In the last decades, substantial progress has been made in our understanding of the cellular and molecular mechanisms of brain regeneration in amphibians and fish. But how similar are the means of brain regeneration in these different species? In this review, we provide an overview of common and distinct aspects of brain regeneration in frog, salamander, and teleost fish species: from the origin of regenerated cells to the functional recovery of behaviors.
Topics: Amphibians; Animals; Brain; Brain Injuries; Fishes; Metamorphosis, Biological; Nerve Regeneration; Species Specificity
PubMed: 30600647
DOI: 10.1002/dneu.22665 -
Cold Spring Harbor Perspectives in... Aug 2015Size is a primary feature of biological systems that varies at many levels, from the organism to its constituent cells and subcellular structures. Amphibians populate... (Review)
Review
Size is a primary feature of biological systems that varies at many levels, from the organism to its constituent cells and subcellular structures. Amphibians populate some of the extremes in biological size and have provided insight into scaling mechanisms, upper and lower size limits, and their physiological significance. Body size variation is a widespread evolutionary tactic among amphibians, with miniaturization frequently correlating with direct development that occurs without a tadpole stage. The large genomes of salamanders lead to large cell sizes that necessitate developmental modification and morphological simplification. Amphibian extremes at the cellular level have provided insight into mechanisms that accommodate cell-size differences. Finally, how organelles scale to cell size between species and during development has been investigated at the molecular level, because subcellular scaling can be recapitulated using Xenopus in vitro systems.
Topics: Amphibians; Animals; Biological Evolution; Body Size; Cell Size; Genome Size; Ovum; Ploidies; Xenopus
PubMed: 26261280
DOI: 10.1101/cshperspect.a019166