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Biology Letters Aug 2021Chytridiomycosis, an infectious disease of amphibians caused by the fungal pathogen (Bd), poses an imminent conservation threat. The global spread of Bd has led to mass...
Chytridiomycosis, an infectious disease of amphibians caused by the fungal pathogen (Bd), poses an imminent conservation threat. The global spread of Bd has led to mass mortality events in many amphibian species, resulting in at least 90 species' extinctions to date. Exposure to Bd metabolites (i.e. non-infectious antigenic chemicals released by Bd) partially protects frogs during subsequent challenges with live Bd, suggesting its use as a prophylactic treatment and potential vaccine. However, we do not know whether Bd metabolite exposure protects against strains beyond the one used for treatment. To address this knowledge gap, we conducted a 3 × 2 experiment where we exposed adult Cuban treefrogs, , to one of three treatments (Bd metabolites from California-isolated strain JEL-270, Panamá-isolated strain JEL-419, or an artificial spring water control) and then challenged individuals with live Bd from either strain. We found that exposure to Bd metabolites from the California-isolated strain significantly reduced Bd loads of frogs challenged with the live Panamá-isolated strain, but no other treatments were found to confer protective effects. These findings demonstrate asymmetric cross-protection of a Bd metabolite prophylaxis and suggest that work investigating multiple, diverse strains is urgently needed.
Topics: Amphibians; Animals; Anura; Chytridiomycota; Humans; Mycoses
PubMed: 34428958
DOI: 10.1098/rsbl.2021.0207 -
ELife Aug 2021As the biodiversity crisis continues, we must redouble efforts to understand and curb pressures pushing species closer to extinction. One major driver is the...
As the biodiversity crisis continues, we must redouble efforts to understand and curb pressures pushing species closer to extinction. One major driver is the unsustainable trade of wildlife. Trade in internationally regulated species gains the most research attention, but this only accounts for a minority of traded species and we risk failing to appreciate the scale and impacts of unregulated legal trade. Despite being legal, trade puts pressure on wild species via direct collection, introduced pathogens, and invasive species. Smaller species-rich vertebrates, such as reptiles, fish, and amphibians, may be particularly vulnerable to trading because of gaps in regulations, small distributions, and demand of novel species. Here, we combine data from five sources: online web searches in six languages, Convention on International Trade in Endangered Species (CITES) trade database, Law Enforcement Management Information System (LEMIS) trade inventory, IUCN assessments, and a recent literature review, to characterise the global trade in amphibians, and also map use by purpose including meat, pets, medicinal, and for research. We show that 1215 species are being traded (17% of amphibian species), almost three times previous recorded numbers, 345 are threatened, and 100 Data Deficient or unassessed. Traded species origin hotspots include South America, China, and Central Africa; sources indicate 42% of amphibians are taken from the wild. Newly described species can be rapidly traded (mean time lag of 6.5 years), including threatened and unassessed species. The scale and limited regulation of the amphibian trade, paired with the triptych of connected pressures (collection, pathogens, invasive species), warrants a re-examination of the wildlife trade status quo, application of the precautionary principle in regard to wildlife trade, and a renewed push to achieve global biodiversity goals.
Topics: Africa, Central; Amphibians; Animals; Animals, Wild; Biodiversity; China; Commerce; Databases, Factual; Endangered Species; Internationality; Reptiles; South America; Species Specificity
PubMed: 34382939
DOI: 10.7554/eLife.70086 -
Biological Reviews of the Cambridge... May 2011The invasive spread of exotic plants in native vegetation can pose serious threats to native faunal assemblages. This is of particular concern for reptiles and... (Review)
Review
The invasive spread of exotic plants in native vegetation can pose serious threats to native faunal assemblages. This is of particular concern for reptiles and amphibians because they form a significant component of the world's vertebrate fauna, play a pivotal role in ecosystem functioning and are often neglected in biodiversity research. A framework to predict how exotic plant invasion will affect reptile and amphibian assemblages is imperative for conservation, management and the identification of research priorities. Here, we present a new predictive framework that integrates three mechanistic models. These models are based on exotic plant invasion altering: (1) habitat structure; (2) herbivory and predator-prey interactions; (3) the reproductive success of reptile and amphibian species and assemblages. We present a series of testable predictions from these models that arise from the interplay over time among three exotic plant traits (growth form, area of coverage, taxonomic distinctiveness) and six traits of reptiles and amphibians (body size, lifespan, home range size, habitat specialisation, diet, reproductive strategy). A literature review provided robust empirical evidence of exotic plant impacts on reptiles and amphibians from each of the three model mechanisms. Evidence relating to the role of body size and diet was less clear-cut, indicating the need for further research. The literature provided limited empirical support for many of the other model predictions. This was not, however, because findings contradicted our model predictions but because research in this area is sparse. In particular, the small number of studies specifically examining the effects of exotic plants on amphibians highlights the pressing need for quantitative research in this area. There is enormous scope for detailed empirical investigation of interactions between exotic plants and reptile and amphibian species and assemblages. The framework presented here and further testing of predictions will provide a basis for informing and prioritising environmental management and exotic plant control efforts.
Topics: Amphibians; Animals; Ecosystem; Introduced Species; Models, Biological; Plants; Reptiles
PubMed: 20735378
DOI: 10.1111/j.1469-185X.2010.00152.x -
Philosophical Transactions of the Royal... Aug 2019A number of hypotheses about compensatory mechanisms that allow ectothermic animals to cope with the latitudinal decrease in ambient temperature ( T) have been proposed...
A number of hypotheses about compensatory mechanisms that allow ectothermic animals to cope with the latitudinal decrease in ambient temperature ( T) have been proposed during the last century. One of these hypotheses, the 'metabolic homeostasis' hypothesis (MHH), states that species should show the highest thermal sensitivity of the metabolic rate ( Q) at the colder end of the range of Ts they usually experience in nature. This way, species should be able to minimize maintenance costs during the colder hours of the day, but quickly take advantage of increases in T during the warmer parts of the day. Here, we created a dataset that includes Q values for 58 amphibian species, assessed at four thermal ranges, to evaluate three predictions derived from the MHH. In line with this hypothesis, we found that: (i) Q values tended to be positively correlated with latitude when measured at lower Ts, but negative correlated with latitude when measured at higher Ts, (ii) Q measured at lower Ts were higher in temperate species, whereas Q measured at higher Ts were higher in tropical species, and (iii) the experimental T at which Q was maximal for each species decreased with latitude. This is the first study to our knowledge showing that the relationship between Q and latitude in ectotherms changes with the T at which Q is assessed, as predicted from an adaptive hypothesis. This article is part of the theme issue 'Physiological diversity, biodiversity patterns and global climate change: testing key hypotheses involving temperature and oxygen'.
Topics: Amphibians; Animals; Climate Change; Ecosystem; Homeostasis; Oxygen; Phylogeny; Temperature
PubMed: 31203760
DOI: 10.1098/rstb.2018.0544 -
Trends in Microbiology Oct 2019
Topics: Amphibians; Animal Diseases; Animals; Chytridiomycota; Mycoses; Urodela
PubMed: 31128929
DOI: 10.1016/j.tim.2019.04.009 -
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 -
The American Naturalist Nov 2007Amphibians exhibit the greatest diversity of reproductive strategies of all tetrapod vertebrates. While authors have traditionally attributed the evolution of these... (Review)
Review
Amphibians exhibit the greatest diversity of reproductive strategies of all tetrapod vertebrates. While authors have traditionally attributed the evolution of these strategies to factors such as complex topography, unpredictable larval environments, and predation on larvae and eggs, support for any of these hypotheses has been limited. Importantly, most authors have ignored parasites, including unicellular pathogens and multicellular parasites, as selective agents capable of influencing amphibian evolution. Insights in disease transmission, amphibian immunity, and their interaction with various life histories require that we consider parasites to be selective pressures in our exploration of the evolution of amphibian reproductive strategies. I review recent findings and describe how these principles converge to form a novel conceptual hypothesis for the evolution of alternative reproductive strategies in amphibians. I offer some specific predictions and recommend that parasites be considered with other selective pressures when constructing formal, falsifiable hypotheses during evaluative studies of amphibian reproductive behavior.
Topics: Amphibians; Animals; Biological Evolution; Host-Parasite Interactions; Larva; Population Dynamics; Reproduction
PubMed: 17926300
DOI: 10.1086/521958 -
Developmental and Comparative Immunology Jan 2017Like all other vertebrate groups, amphibian responses to the environment are mediated through the brain (hypothalamic)-pituitary-adrenal/interrenal (HPA/I) axis and the... (Review)
Review
Like all other vertebrate groups, amphibian responses to the environment are mediated through the brain (hypothalamic)-pituitary-adrenal/interrenal (HPA/I) axis and the sympathetic nervous system. Amphibians are facing historically unprecedented environmental stress due to climate change that will involve unpredictable temperature and rainfall regimes and possible nutritional deficits due to extremes of temperature and drought. At the same time, amphibians in all parts of the world are experiencing unprecedented declines due to the emerging diseases, chytridiomycosis (caused by Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans) and ranavirus diseases due to viruses of the genus Ranavirus in the family Iridoviridae. Other pathogens and parasites also afflict amphibians, but here I will limit myself to a review of recent literature linking stress and these emerging diseases (chytridiomycosis and ranavirus disease) in order to better predict how environmental stressors and disease will affect global amphibian populations.
Topics: Amphibians; Animals; Chytridiomycota; Climate Change; Humans; Hypothalamo-Hypophyseal System; Immune System; Immunity, Innate; Pituitary-Adrenal System; Ranavirus; Stress, Physiological
PubMed: 27387153
DOI: 10.1016/j.dci.2016.07.002 -
Diseases of Aquatic Organisms Feb 2023Ranaviruses can cause mass mortality events in amphibians, thereby becoming a threat to populations that are already facing dramatic declines. Ranaviruses affect all...
Ranaviruses can cause mass mortality events in amphibians, thereby becoming a threat to populations that are already facing dramatic declines. Ranaviruses affect all life stages and persist in multiple amphibian hosts. The detrimental effects of ranavirus infections to amphibian populations have already been observed in the UK and in North America. In Central and South America, the virus has been reported in several countries, but the presence of the genus Ranavirus (Rv) in Colombia is unknown. To help fill this knowledge gap, we surveyed for Rv in 60 species of frogs (including one invasive species) in Colombia. We also tested for co-infection with Batrachochytrium dendrobatidis (Bd) in a subset of individuals. For Rv, we sampled 274 vouchered liver tissue samples collected between 2014 and 2019 from 41 localities covering lowlands to mountaintop páramo habitat across the country. Using quantitative polymerase chain reaction (qPCR) and end-point PCR, we detected Rv in 14 individuals from 8 localities, representing 6 species, including 5 native frogs of the genera Osornophryne, Pristimantis and Leptodactylus, and the invasive American bullfrog Rana catesbeiana. Bd was detected in 7 of 140 individuals, with 1 co-infection of Rv and Bd in an R. catesbeiana specimen collected in 2018. This constitutes the first report of ranavirus in Colombia and should set off alarms about this new emerging threat to amphibian populations in the country. Our findings provide some preliminary clues about how and when Rv may have spread and contribute to understanding how the pathogen is distributed globally.
Topics: Animals; Amphibians; Anura; Batrachochytrium; Coinfection; Colombia; DNA Virus Infections; Mycoses; Rana catesbeiana; Ranavirus
PubMed: 36794841
DOI: 10.3354/dao03717 -
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