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Seminars in Nuclear Medicine Sep 2023The bulk of biomedical positron emission tomography (PET)-scanning experiments are performed on mammals (ie, rodents, pigs, and dogs), and the technique is only... (Review)
Review
The bulk of biomedical positron emission tomography (PET)-scanning experiments are performed on mammals (ie, rodents, pigs, and dogs), and the technique is only infrequently applied to answer research questions in ectothermic vertebrates such as fish, amphibians, and reptiles. Nevertheless, many unique and interesting physiological characteristics in these ectothermic vertebrates could be addressed in detail through PET. The low metabolic rate of ectothermic animals, however, may compromise the validity of physiological and biochemical parameters derived from the images created by PET and other scanning modalities. Here, we review some of the considerations that should be taken into account when PET scanning fish, amphibians, and reptiles. We present specific results from our own experiments, many of which remain previously unpublished, and we draw on examples from the literature. We conclude that knowledge on the natural history and physiology of the species studied and an understanding of the limitations of the PET scanning techniques are necessary to avoid the design of faulty experiments and erroneous conclusions.
Topics: Animals; Swine; Dogs; Vertebrates; Reptiles; Amphibians; Fishes; Positron-Emission Tomography; Mammals
PubMed: 37438172
DOI: 10.1053/j.semnuclmed.2023.06.006 -
Current Opinion in Neurobiology Oct 2023The transition from larval to adult locomotion in the anuran, Xenopus laevis, involves a dramatic switch from axial to appendicular swimming including intermediate... (Review)
Review
The transition from larval to adult locomotion in the anuran, Xenopus laevis, involves a dramatic switch from axial to appendicular swimming including intermediate stages when the tail and hindlimbs co-exist and contribute to propulsion. Hatchling tadpole swimming is generated by an axial central pattern generator (CPG) which matures rapidly during early larval life. During metamorphosis, the developing limbs are controlled by a de novo appendicular CPG driven initially by the axial system before segregating to allow both systems to operate together or independently. Neuromodulation plays important roles throughout, but key modulators switch their effects from early inhibitory influences to facilitating locomotion. Temperature affects the construction and operation of locomotor networks and global changes in environmental temperature place aquatic poikilotherms, like amphibians, at risk. The locomotor control strategy of anurans differs from other amphibian groups such as salamanders, where evolution has acted upon the thyroid hormone pathway to sculpt different developmental outcomes.
Topics: Animals; Spinal Cord; Larva; Locomotion; Swimming; Anura; Metamorphosis, Biological
PubMed: 37549591
DOI: 10.1016/j.conb.2023.102753 -
Zoo Biology 2014Amphibian biology is intricate, and there are many inter-related factors that need to be understood before establishing successful Conservation Breeding Programs (CBPs).... (Review)
Review
Amphibian biology is intricate, and there are many inter-related factors that need to be understood before establishing successful Conservation Breeding Programs (CBPs). Nutritional needs of amphibians are highly integrated with disease and their husbandry needs, and the diversity of developmental stages, natural habitats, and feeding strategies result in many different recommendations for proper care and feeding. This review identifies several areas where there is substantial room for improvement in maintaining healthy ex situ amphibian populations specifically in the areas of obtaining and utilizing natural history data for both amphibians and their dietary items, achieving more appropriate environmental parameters, understanding stress and hormone production, and promoting better physical and population health. Using a scientific or research framework to answer questions about disease, nutrition, husbandry, genetics, and endocrinology of ex situ amphibians will improve specialists' understanding of the needs of these species. In general, there is a lack of baseline data and comparative information for most basic aspects of amphibian biology as well as standardized laboratory approaches. Instituting a formalized research approach in multiple scientific disciplines will be beneficial not only to the management of current ex situ populations, but also in moving forward with future conservation and reintroduction projects. This overview of gaps in knowledge concerning ex situ amphibian care should serve as a foundation for much needed future research in these areas.
Topics: Amphibians; Animal Husbandry; Animal Nutritional Physiological Phenomena; Animals; Animals, Zoo; Bone Diseases, Metabolic; Breeding; Conservation of Natural Resources; Life Cycle Stages; Stress, Physiological; Vitamin A Deficiency
PubMed: 25296396
DOI: 10.1002/zoo.21180 -
Sexual Development : Genetics,... 2023Reptiles and amphibians provide untapped potential for discovering how a diversity of genetic pathways and environmental conditions are incorporated into developmental... (Review)
Review
BACKGROUND
Reptiles and amphibians provide untapped potential for discovering how a diversity of genetic pathways and environmental conditions are incorporated into developmental processes that can lead to similar functional outcomes. These groups display a multitude of reproductive strategies, and whereas many attributes are conserved within groups and even across vertebrates, several aspects of sexual development show considerable variation.
SUMMARY
In this review, we focus our attention on the development of the reptilian and amphibian ovary. First, we review and describe the events leading to ovarian development, including sex determination and ovarian maturation, through a comparative lens. We then describe how these events are influenced by environmental factors, focusing on temperature and exposure to anthropogenic chemicals. Lastly, we identify critical knowledge gaps and future research directions that will be crucial to moving forward in our understanding of ovarian development and the influences of the environment in reptiles and amphibians.
KEY MESSAGES
Reptiles and amphibians provide excellent models for understanding the diversity of sex determination strategies and reproductive development. However, a greater understanding of the basic biology of these systems is necessary for deciphering the adaptive and potentially disruptive implications of embryo-by-environment interactions in a rapidly changing world.
Topics: Animals; Female; Reptiles; Amphibians; Sex Differentiation; Ovary; Temperature; Sex Determination Processes
PubMed: 36380624
DOI: 10.1159/000526009 -
Sexual Development : Genetics,... 2017Sex chromosomes in most amphibians are homomorphic (undifferentiated) in both sexes and are characterized by frequent turnover. This is in sharp contrast to sex... (Review)
Review
Sex chromosomes in most amphibians are homomorphic (undifferentiated) in both sexes and are characterized by frequent turnover. This is in sharp contrast to sex chromosomes in 2 major vertebrate groups, the mammals and birds, where they are heteromorphic in one sex and are highly conserved. Sex-determining mechanisms in anuran amphibians, particularly in relation to the turnover of sex-determining genes and sex chromosomes, are summarized and their evolution is discussed.
Topics: Amphibians; Animals; Female; Male; Sex Chromosomes; Sex Determination Analysis; Sex Determination Processes
PubMed: 29241181
DOI: 10.1159/000485270 -
Dong Wu Xue Yan Jiu = Zoological... Jul 2016Model organisms have long been important in biology and medicine due to their specific characteristics. Amphibians, especially Xenopus, play key roles in answering... (Review)
Review
Model organisms have long been important in biology and medicine due to their specific characteristics. Amphibians, especially Xenopus, play key roles in answering fundamental questions on developmental biology, regeneration, genetics, and toxicology due to their large and abundant eggs, as well as their versatile embryos, which can be readily manipulated and developed in vivo. Furthermore, amphibians have also proven to be of considerable benefit in human disease research due to their conserved cellular developmental and genomic organization. This review gives a brief introduction on the progress and limitations of these animal models in biology and human disease research, and discusses the potential and challenge of Microhyla fissipes as a new model organism.
Topics: Amphibians; Animals; Cell Cycle; Humans; Models, Animal; Regeneration; Research Design; Toxicology
PubMed: 27469255
DOI: 10.13918/j.issn.2095-8137.2016.4.237 -
Cytogenetic and Genome Research 2015This review summarizes the current status of the known extant genuine polyploid anuran and urodelan species, as well as spontaneously originated and/or experimentally... (Review)
Review
This review summarizes the current status of the known extant genuine polyploid anuran and urodelan species, as well as spontaneously originated and/or experimentally produced amphibian polyploids. The mechanisms by which polyploids can originate, the meiotic pairing configurations, the diploidization processes operating in polyploid genomes, the phenomenon of hybridogenesis, and the relationship between polyploidization and sex chromosome evolution are discussed. The polyploid systems in some important amphibian taxa are described in more detail.
Topics: Amphibians; Animals; Cell Fusion; Chromosome Duplication; Diploidy; Female; Genetic Techniques; Germ Cells; Hybridization, Genetic; Larva; Male; Meiosis; Models, Genetic; Polyploidy; Ranidae; Sex Chromosomes; Species Specificity; Xenopus
PubMed: 26112701
DOI: 10.1159/000431388 -
Current Biology : CB Jun 2019Many animals undergo a transition during their lifetime from a larval to an adult form, a major developmental change known as metamorphosis. This developmental process,...
Many animals undergo a transition during their lifetime from a larval to an adult form, a major developmental change known as metamorphosis. This developmental process, which involves behavioural, morphological, physiological and biochemical changes, has a broad phylogenetic distribution, occurring in diverse branches of the animal kingdom, from invertebrates (molluscs, arthropods, tunicates) to certain classes of vertebrates, including amphibians (Figure 1). This phenomenon, which has fascinated biologists for centuries, remains an attractive experimental model for studying mechanisms of post-embryonic development as well as molecular mechanisms underlying hormonal regulation.
Topics: Amphibians; Animals; Larva; Locomotion; Metamorphosis, Biological; Nerve Net; Neuronal Plasticity; Respiration
PubMed: 31211970
DOI: 10.1016/j.cub.2019.05.005 -
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 -
Philosophical Transactions of the Royal... Dec 2016Chytridiomycosis is an emerging infectious disease of amphibians that affects over 700 species on all continents where amphibians occur. The amphibian-chytridiomycosis... (Review)
Review
Chytridiomycosis is an emerging infectious disease of amphibians that affects over 700 species on all continents where amphibians occur. The amphibian-chytridiomycosis system is complex, and the response of any amphibian species to chytrid depends on many aspects of the ecology and evolutionary history of the amphibian, the genotype and phenotype of the fungus, and how the biological and physical environment can mediate that interaction. Impacts of chytridiomycosis on amphibians are varied; some species have been driven extinct, populations of others have declined severely, whereas still others have not obviously declined. Understanding patterns and mechanisms of amphibian responses to chytrids is critical for conservation and management. Robust estimates of population numbers are needed to identify species at risk, prioritize taxa for conservation actions, design management strategies for managing populations and species, and to develop effective measures to reduce impacts of chytrids on amphibians.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.
Topics: Amphibians; Animals; Chytridiomycota; Communicable Diseases, Emerging; Mycoses
PubMed: 28080989
DOI: 10.1098/rstb.2015.0465