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Development, Growth & Differentiation Jan 2023
Topics: Animals; Amphibians; Models, Animal
PubMed: 36740732
DOI: 10.1111/dgd.12838 -
Current Opinion in Microbiology Jun 2021Amphibian populations around the world have been affected by two pathogenic fungi within the phylum Chytridiomycota. Batrachochytrium dendrobatidis (Bd) has infected... (Review)
Review
Amphibian populations around the world have been affected by two pathogenic fungi within the phylum Chytridiomycota. Batrachochytrium dendrobatidis (Bd) has infected hundreds of species and led to widespread declines and some species extinctions. Batrachochytrium salamandrivorans (Bsal) has devastated some native European salamanders, especially the iconic fire salamanders (Salamandra salamandra). Comparative genomic studies show that Bd is more diverse and widespread than previously thought, and global lineages occur together allowing for the development of hybrid lineages. New studies raise the concern of greater pathogenesis if both Bd and Bsal infect the same host. Although amphibians possess robust immune defenses, co-infected and many single-infected hosts seem unable to mount effective immune responses. A strong defense may actually be harmful. Analysis of Bd and Bsal secretions documents small metabolites that signal high density to limit their growth and to suppress adaptive immune defenses, thus enabling a stealth presence in the skin compartment.
Topics: Amphibians; Animals; Batrachochytrium; Chytridiomycota; Skin
PubMed: 33964650
DOI: 10.1016/j.mib.2021.04.002 -
Journal of Experimental Zoology. Part... Dec 2020Understanding host immune function and ecoimmunology is increasingly important at a time when emerging infectious diseases (EIDs) threaten wildlife. One EID that has... (Review)
Review
Understanding host immune function and ecoimmunology is increasingly important at a time when emerging infectious diseases (EIDs) threaten wildlife. One EID that has emerged and spread widely in recent years is chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), which is implicated unprecedented amphibian declines around the world. The impacts of Bd have been severe for many amphibian species, but some populations have exhibited signs of persistence, and even recovery, in some regions. Many mechanisms may underpin this pattern and amphibian immune responses are likely one key component. Although we have made great strides in understanding amphibian immunity, the complement system remains poorly understood. The complement system is a nonspecific, innate immune defense that is known to enhance other immune responses. Complement activation can occur by three different biochemical pathways and result in protective mechanisms, such as inflammation, opsonization, and pathogen lysis, thereby providing protection to the host. We currently lack an understanding of complement pathway activation for chytridiomycosis, but several studies have suggested that it may be a key part of an early and robust immune response that confers host resistance. Here, we review the available research on the complement system in general as well as amphibian complement responses to Bd infection. Additionally, we propose future research directions that will increase our understanding of the amphibian complement system and other immune responses to Bd. Finally, we suggest how a deeper understanding of amphibian immunity could enhance the conservation and management of amphibian species that are threatened by chytridiomycosis.
Topics: Amphibians; Animals; Batrachochytrium; Complement System Proteins; Mycoses
PubMed: 33052039
DOI: 10.1002/jez.2419 -
Molecular Ecology Resources Jan 2024Since Ficetola et al. (2008) alerted ecologists and conservation biologists to the existence of environmental DNA (eDNA), the number of studies using eDNA has exploded,...
Since Ficetola et al. (2008) alerted ecologists and conservation biologists to the existence of environmental DNA (eDNA), the number of studies using eDNA has exploded, with a rapidly increasing diversity of research, monitoring, and management objectives. Initial applications focused on amphibians and fishes while today's taxonomic targets span the phylogenetic tree. The environmental media that are sampled have expanded from freshwater to saltwater to soils, and, most recently, to air. In this issue of Molecular Ecology Resources, Lynggaard et al. (Molecular Ecology Resources, 2023) use eDNA captured on air filters to census vertebrate biodiversity in a forest. With a three day, six sample period, 143 sample effort in a nature park in a rural area of Zealand, Denmark, their wild species detections comprised about 25% of the terrestrial vertebrates that are known to occur in the area, including about 33% of the mammal, 17% of the bird, and 60% of the amphibian species. This study demonstrates that air sampling for eDNA has the potential to become a powerful standard method for terrestrial biodiversity assessment that is complementary to traditional methods (e.g., trapping, visual and acoustic observation, collection of scat and hair).
Topics: Animals; Phylogeny; Environmental Monitoring; DNA Barcoding, Taxonomic; Vertebrates; Biodiversity; Fishes; Amphibians; Mammals; DNA, Environmental; Ecosystem
PubMed: 37864493
DOI: 10.1111/1755-0998.13883 -
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 -
Molecular and Cellular Endocrinology Aug 2020Concern over global amphibian declines and possible links to agrochemical use has led to research on the endocrine disrupting actions of agrochemicals, such as... (Review)
Review
Concern over global amphibian declines and possible links to agrochemical use has led to research on the endocrine disrupting actions of agrochemicals, such as fertilizers, fungicides, insecticides, acaricides, herbicides, metals, and mixtures. Amphibians, like other species, have to partition resources for body maintenance, growth, and reproduction. Recent studies suggest that metabolic impairments induced by endocrine disrupting chemicals, and more particularly agrichemicals, may disrupt physiological constraints associated with these limited resources and could cause deleterious effects on growth and reproduction. Metabolic disruption has hardly been considered for amphibian species following agrichemical exposure. As for metamorphosis, the key thyroid hormone-dependent developmental phase for amphibians, it can either be advanced or delayed by agrichemicals with consequences for juvenile and adult health and survival. While numerous agrichemicals affect anuran sexual development, including sex reversal and intersex in several species, little is known about the mechanisms involved in dysregulation of the sex differentiation processes. Adult anurans display stereotypical male mating calls and female phonotaxis responses leading to successful amplexus and spawning. These are hormone-dependent behaviours at the foundation of reproductive success. Therefore, male vocalizations are highly ecologically-relevant and may be a non-invasive low-cost method for the assessment of endocrine disruption at the population level. While it is clear that agrochemicals disrupt multiple endocrine systems in frogs, very little has been uncovered regarding the molecular and cellular mechanisms at the basis of these actions. This is surprising, given the importance of the frog models to our deep understanding of developmental biology and thyroid hormone action to understand human health. Several agrochemicals were found to have multiple endocrine effects at once (e.g., targeting both the thyroid and gonadal axes); therefore, the assessment of agrochemicals that alter cross-talk between hormonal systems must be further addressed. Given the diversity of life-history traits in Anura, Caudata, and the Gymnophiona, it is essential that studies on endocrine disruption expand to include the lesser known taxa. Research under ecologically-relevant conditions will also be paramount. Closer collaboration between molecular and cellular endocrinologists and ecotoxicologists and ecologists is thus recommended.
Topics: Agrochemicals; Amphibians; Animals; Endocrine Disruptors; Endocrine System; Female; Male; Metamorphosis, Biological; Reproduction; Sex Differentiation; Sexual Development
PubMed: 32450283
DOI: 10.1016/j.mce.2020.110861 -
The Science of the Total Environment Nov 2019Environmental contamination contributes to the threatened status of many amphibian populations. Many contaminants alter behaviour at concentrations commonly experienced... (Meta-Analysis)
Meta-Analysis Review
Environmental contamination contributes to the threatened status of many amphibian populations. Many contaminants alter behaviour at concentrations commonly experienced in the environment, with negative consequences for individual fitness, populations and communities. A comprehensive, quantitative evaluation of the behavioural sensitivity of amphibians is warranted to better understand the population-level and resultant ecological impacts of contaminants. We conducted a systematic review and meta-analysis evaluating behavioural changes following exposure to contaminants. Most studies were conducted in North America and Europe on larval stages, and 64% of the 116 studies focussed on the effects of insecticides. We found that a suite of contaminants influence a wide range of behaviours in amphibians, with insecticides typically invoking the strongest responses. In particular, insecticides increased rates of abnormal swimming, and reduced escape responses to simulated predator attacks. Our analysis identified five key needs for future research, in particular the need: (1) for researchers to provide more details of experimental protocols and results (2) to develop a strong research base for future quantitative reviews, (3) to broaden the suite of contaminants tested, (4) to better study and thus understand the effects of multiple stressors, and (5) to establish the ecological importance of behavioural alterations. Behavioural endpoints provide useful sub-lethal indicators of how contaminants influence amphibians, and coupled with standard ecotoxicological endpoints, can provide valuable information for population models assessing the broader ecological consequences of environmental contamination.
Topics: Amphibians; Animals; Behavior, Animal; Ecotoxicology; Europe; Insecticides; Larva; North America; Water Pollutants, Chemical
PubMed: 31369889
DOI: 10.1016/j.scitotenv.2019.07.376 -
Aquatic Toxicology (Amsterdam,... May 2024Poly- and perfluoroalkyl substances (PFASs) are commonly used in various industries and everyday products, including clothing, electronics, furniture, paints, and many... (Review)
Review
Poly- and perfluoroalkyl substances (PFASs) are commonly used in various industries and everyday products, including clothing, electronics, furniture, paints, and many others. PFASs are primarily found in aquatic environments, but also present in soil, air and plants, making them one of the most important and dangerous pollutants of the natural environment. PFASs bioaccumulate in living organisms and are especially dangerous to aquatic and semi-aquatic animals. As endocrine disruptors, PFASs affect many internal organs and systems, including reproductive, endocrine, nervous, cardiovascular, and immune systems. This manuscript represents the first comprehensive review exclusively focusing on PFASs in amphibians and reptiles. Both groups of animals are highly vulnerable to PFASs in the natural habitats. Amphibians and reptiles, renowned for their sensitivity to environmental changes, are often used as crucial bioindicators to monitor ecosystem health and environmental pollution levels. Furthermore, the decline in amphibian and reptile populations worldwide may be related to increasing environmental pollution. Therefore, studies investigating the exposure of amphibians and reptiles to PFASs, as well as their impacts on these organisms are essential in modern toxicology. Summarizing the current knowledge on PFASs in amphibians and reptiles in a single manuscript will facilitate the exploration of new research topics in this field. Such a comprehensive review will aid researchers in understanding the implications of PFASs exposure on amphibians and reptiles, guiding future investigations to mitigate their adverse effects of these vital components of ecosystems.
Topics: Animals; Ecosystem; Water Pollutants, Chemical; Amphibians; Reptiles; Fluorocarbons
PubMed: 38564994
DOI: 10.1016/j.aquatox.2024.106907 -
Trends in Microbiology Oct 2019
Topics: Amphibians; Animal Diseases; Animals; Chytridiomycota; Mycoses; Urodela
PubMed: 31128929
DOI: 10.1016/j.tim.2019.04.009 -
Developmental and Comparative Immunology May 2023
Topics: Animals; Amphibians; Ranavirus
PubMed: 36739929
DOI: 10.1016/j.dci.2023.104655