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The Veterinary Clinics of North... May 2022Currently, there are more than 8200 amphibian species described, including the orders Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona... (Review)
Review
Currently, there are more than 8200 amphibian species described, including the orders Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians). Amphibians have 3 heart chambers: 2 atria and 1 ventricle. Their heart anatomy, histology, and physiology are reviewed. The basic morphology of the heart is similar in all amphibians with some differences due to their lifestyle. Blood flow, blood mixing, and blood oxygenation show variation due to interindividual and interspecific differences. Finally, different diagnostic methods to investigate the amphibian heart are described and reported amphibian heart diseases are summarized, including genetic, congenital, infectious, and neoplastic heart diseases.
Topics: Amphibians; Animals; Anura; Heart Diseases
PubMed: 35422258
DOI: 10.1016/j.cvex.2022.01.002 -
Developmental and Comparative Immunology Sep 2023Macrophage-lineage cells are indispensable to immunity and physiology of all vertebrates. Amongst these, amphibians represent a key stage in vertebrate evolution and are... (Review)
Review
Macrophage-lineage cells are indispensable to immunity and physiology of all vertebrates. Amongst these, amphibians represent a key stage in vertebrate evolution and are facing decimating population declines and extinctions, in large part due to emerging infectious agents. While recent studies indicate that macrophages and related innate immune cells are critically involved during these infections, much remains unknown regarding the ontogeny and functional differentiation of these cell types in amphibians. Accordingly, in this review we coalesce what has been established to date about amphibian blood cell development (hematopoiesis), the development of key amphibian innate immune cells (myelopoiesis) and the differentiation of amphibian macrophage subsets (monopoiesis). We explore the current understanding of designated sites of larval and adult hematopoiesis across distinct amphibian species and consider what mechanisms may lend to these species-specific adaptations. We discern the identified molecular mechanisms governing the functional differentiation of disparate amphibian (chiefly Xenopus laevis) macrophage subsets and describe what is known about the roles of these subsets during amphibian infections with intracellular pathogens. Macrophage lineage cells are at the heart of so many vertebrate physiological processes. Thus, garnering greater understanding of the mechanisms responsible for the ontogeny and functionality of these cells in amphibians will lend to a more comprehensive view of vertebrate evolution.
Topics: Animals; Myelopoiesis; Amphibians; Macrophages; Cell Differentiation; Hematopoiesis; Xenopus laevis
PubMed: 37196852
DOI: 10.1016/j.dci.2023.104701 -
The Veterinary Clinics of North... May 2023Amphibians are susceptible to a multitude of skin disorders, many of which can appear grossly similar. The most common clinical presentations include hyperemia,... (Review)
Review
Amphibians are susceptible to a multitude of skin disorders, many of which can appear grossly similar. The most common clinical presentations include hyperemia, discoloration, dermal mass, ulceration, and necrosis. Many amphibian skin diseases are related to captive husbandry. The diagnostic process starts with environmental evaluations, a full history, physical examination and sampling for direct observation, histology, polymerase chain reaction testing, and bacterial and fungal culture. This review emphasizes the main conditions encountered in amphibian dermatology.
Topics: Animals; Dermatology; Ranavirus; Amphibians; Specimen Handling
PubMed: 36965879
DOI: 10.1016/j.cvex.2023.01.001 -
Current Biology : CB Jan 2023Vanessa Smilansky and Thomas A. Richards introduce Perkinsea - a lineage of freshwater parasitic protists that infect certain amphibians and cause of severe Perkinsea...
Vanessa Smilansky and Thomas A. Richards introduce Perkinsea - a lineage of freshwater parasitic protists that infect certain amphibians and cause of severe Perkinsea infection.
Topics: Animals; Alveolata; Amphibians; Fresh Water
PubMed: 36626865
DOI: 10.1016/j.cub.2022.11.032 -
Biological Reviews of the Cambridge... Oct 2022Descriptions of amphibian habitat, both aquatic and terrestrial, often include plants as characteristics but seldom is it understood whether and how those plants affect... (Review)
Review
Descriptions of amphibian habitat, both aquatic and terrestrial, often include plants as characteristics but seldom is it understood whether and how those plants affect amphibian ecology. Understanding how plants affect amphibian populations is needed to develop strategies to combat declines of some amphibian populations. Using a systematic approach, we reviewed and synthesized available literature on the effects of plants on pond-breeding amphibians during the aquatic and terrestrial stages of their life cycle. Our review highlights that plant communities can strongly influence the distribution, abundance, and performance of amphibians in multiple direct and indirect ways. We found three broad themes of plants' influence on amphibians: plants can affect amphibians through effects on abiotic conditions including the thermal, hydric, and chemical aspects of an amphibian's environment; plants can have large effects on aquatic life stages through effects on resource quality and abundance; and plants can modify the nature and strength of interspecific interactions between amphibians and other species - notably predators. We synthesized insights gained from the literature to discuss how plant community management fits within efforts to manage amphibian populations and to guide future research efforts. While some topical areas are well researched, we found a general lack of mechanistic and trait-based work which is needed to advance our understanding of the drivers through which plants influence amphibian ecology. Our literature review reveals the substantial role that plants can have on amphibian ecology and the need for integrating plant and amphibian ecology to improve research and management outcomes for amphibians.
Topics: Amphibians; Animals; Ecosystem; Life Cycle Stages; Plant Breeding; Plants
PubMed: 35441800
DOI: 10.1111/brv.12861 -
The Veterinary Clinics of North... Jan 2020Amphibians are a remarkably diverse group of vertebrates with lifestyles ranging from fully aquatic to entirely terrestrial. Although some aspects of renal anatomy and... (Review)
Review
Amphibians are a remarkably diverse group of vertebrates with lifestyles ranging from fully aquatic to entirely terrestrial. Although some aspects of renal anatomy and physiology are similar among all amphibians, species differences in nitrogenous waste production and broad normal variation in plasma osmolality and composition make definitive antemortem diagnosis of renal disease challenging. Treatment is often empirical and aimed at addressing possible underlying infection, reducing abnormal fluid accumulation, and optimizing husbandry practices to support metabolic and fluid homeostasis. This article reviews amphibian renal anatomy and physiology, provides recommendations for diagnostic and therapeutic options, and discusses etiologies of renal disease.
Topics: Amphibians; Animals; Kidney Diseases; Neoplasms
PubMed: 31759449
DOI: 10.1016/j.cvex.2019.09.005 -
Philosophical Transactions of the Royal... Jul 2023Amphibians are at the forefront of bridging the evolutionary gap between mammals and more ancient, jawed vertebrates. Currently, several diseases have targeted... (Review)
Review
Amphibians are at the forefront of bridging the evolutionary gap between mammals and more ancient, jawed vertebrates. Currently, several diseases have targeted amphibians and understanding their immune system has importance beyond their use as a research model. The immune system of the African clawed frog, , and that of mammals is well conserved. We know that several features of the adaptive and innate immune system are very similar for both, including the existence of B cells, T cells and innate-like T cells. In particular, the study of the immune system at early stages of development is benefitted by studying tadpoles. The tadpoles mainly rely on innate immune mechanisms including pre-set or innate-like T cells until after metamorphosis. In this review we lay out what is known about the innate and adaptive immune system of including the lymphoid organs as well as how other amphibian immune systems are similar or different. Furthermore, we will describe how the amphibian immune system responds to some viral, bacterial and fungal insults. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
Topics: Animals; Immune System; Biological Evolution; Metamorphosis, Biological; Xenopus laevis; Mammals
PubMed: 37305914
DOI: 10.1098/rstb.2022.0123 -
The Veterinary Clinics of North... Jan 2022Amphibians commonly are managed under human care for research, education, conservation, and companionship and frequently are in need of sedation, anesthesia, or... (Review)
Review
Amphibians commonly are managed under human care for research, education, conservation, and companionship and frequently are in need of sedation, anesthesia, or end-of-life care involving euthanasia. Objective investigation of sedative and anesthetic protocols in these taxa still is in its infancy, but knowledge of current best practices is paramount to appropriate care. Tricaine methanesulfonate delivered via immersion (bath) is the most common anesthetic agent in amphibians, but several other effective techniques have been identified. This summary provides a comprehensive review of the current evidence-based literature regarding amphibian sedative, anesthetic, and euthanasia techniques.
Topics: Aminobenzoates; Amphibians; Anesthesia; Anesthetics; Animals
PubMed: 34823696
DOI: 10.1016/j.cvex.2021.08.008 -
Cell Biology International Dec 2022Compared to other animals, the spontaneous occurrence of tumors in wild amphibians is relatively rare, generally limited to specific populations or species. The number... (Review)
Review
Compared to other animals, the spontaneous occurrence of tumors in wild amphibians is relatively rare, generally limited to specific populations or species. The number of reports of spontaneous tumors in amphibians known up to 1986 was 491 cases in anurans and about 253 cases in urodeles. Similarly, there have been many, unsuccessful attempts to chemically or biologically induce tumors in amphibians. With these considerations, it is inevitable to wonder: do urodeles and anurans have an inherent resistance to cancer? Here, we review the spontaneous and induced occurrence of tumors in amphibians in a timeline, as well as failed attempts to induce tumors in these amphibians. Indeed, recent studies seem to indicate that there is a relationship between regeneration and cancer because regenerating tissues seem to resist tumorigenesis, as opposed to nonregenerative tissues of the same amphibian models. Although the mechanisms that allow regenerating tissues to resist tumorigenesis have not been elucidated, it is worth to note that, in addition to the apparent relationship between regeneration and cancer, amphibians possess characteristics that could contribute to their ability to resist the development of neoplastic events. The implications of these features in cancer susceptibility are discussed.
Topics: Animals; Amphibians; Neoplasms; Cell Transformation, Neoplastic
PubMed: 35979661
DOI: 10.1002/cbin.11888 -
Environmental Toxicology and Chemistry Jul 2021Amphibian populations are declining globally. Major drivers of these global declines are known. However, the contribution of these major drivers to population declines... (Review)
Review
Amphibian populations are declining globally. Major drivers of these global declines are known. However, the contribution of these major drivers to population declines varies by the presence or absence and the interactive effect of drivers, thus creating local challenges for conservation of populations. Studies have determined that environmental contaminants contribute to amphibian population declines. However, there is a disagreement over the use of amphibians as sentinel species in ecotoxicological testing rather than the traditional taxa used, fish and invertebrates. Reviews of ecotoxicological studies have demonstrated that amphibians are generally less sensitive than fish and invertebrates to different groups of contaminants. Nonetheless, because of the distinct nature and mechanism of toxicity of various contaminants, it is necessary to study contaminants individually to be able to come to any conclusion on the relative sensitivity of amphibians. Copper is one of the most studied environmental contaminants. We conducted a literature review of Cu toxicity to amphibians and the relative sensitivity of amphibians to other aquatic animals. The available data suggest that although amphibians may be tolerant of acute Cu exposure, they are relatively sensitive to chronic exposure (i.e., 100-fold greater sensitivity to chronic compared to acute exposure). In addition, ecologically relevant endpoints specific to amphibians (e.g., duration of metamorphosis and behavior) are shown to provide a better understanding of their sensitivity compared to traditional endpoints (e.g., survival and growth). Our current knowledge on amphibian sensitivity is far from complete. Considering the current status of this globally threatened class of animals, it is necessary to fill the knowledge gaps regarding their sensitivity to individual contaminants, beginning with Cu. Environ Toxicol Chem 2021;40:1810-1821. © 2021 SETAC.
Topics: Amphibians; Animals; Copper; Fishes; Invertebrates
PubMed: 33749926
DOI: 10.1002/etc.5049