scholarly journals Shifts in temperature influence howBatrachochytrium dendrobatidisinfects amphibian larvae

2017 ◽  
Author(s):  
Paul W. Bradley ◽  
Michael D. Brawner ◽  
Thomas R. Raffel ◽  
Jason R. Rohr ◽  
Deanna H. Olson ◽  
...  
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Temperature Shift ◽  
Amphibian Species ◽  
Change Models ◽  
Rana Aurora ◽  
Amphibian Larvae ◽  
Western Toads ◽  
Anaxyrus Boreas ◽  
Potential Shifts ◽  
Increased Susceptibility

AbstractMany climate change models predict increases in mean temperature, and increases in frequency and magnitude of temperature fluctuations. These potential shifts may impact ectotherms in several ways, including how they are affected by disease. Shifts in temperature may especially affect amphibians, a group with populations that have been challenged by several pathogens. Because amphibian hosts invest more in immunity at warmer than cooler temperatures and parasites may acclimate to temperature shifts faster than hosts (creating lags in optimal host immunity), researchers have hypothesized that a temperature shift from cold-to-warm might result in increased amphibian sensitivity to pathogens, whereas a shift from warm-to-cold might result in decreased sensitivity. Support for components of this climate-variability based hypothesis have been provided by prior studies of the fungusBatrachochytrium dendrobatidis(Bd) that causes the disease chytridiomycosis in amphibians. We experimentally tested whether temperature shifts before Bd exposure alter susceptibility to Bd in the larval stage of two amphibian species – western toads (Anaxyrus boreas) and northern red legged frogs (Rana aurora). Both host species harbored elevated Bd infection intensities under constant cold (15° C) temperature in comparison to constant warm (20° C) temperature. Additionally, both species experienced an increase in Bd infection abundance when shifted to 20° C from 15° C, compared to a constant 20° C but they experienced a decrease in Bd when shifted to 15° C from 20° C, compared to a constant 15° C. These results are in contrast to prior studies of adult amphibians that found increased susceptibility to Bd infection after a temperature shift in either direction, highlighting the potential for species and stage differences in the temperature-dependence of chytridiomycosis.

scholarly journals The observed decline of Western Toads (Anaxyrus boreas) over several decades at a novel winter breeding site

2018 ◽  
Vol 132 (1) ◽  
pp. 53-57 ◽  
Author(s):  
Brian G. Slough ◽  
Alexander DeBruyn
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Cold Water ◽  
Breeding Site ◽  
Breeding Phenology ◽  
Warm Springs ◽  
Amphibian Chytrid Fungus ◽  
Western Toads ◽  
Anaxyrus Boreas ◽  
Extraordinary Feature ◽  
Winter Breeding

The Western Toad (Anaxyrus boreas) population of the Atlin Warm Springs in northwestern British Columbia has persisted since at least 1924. An extraordinary feature of the population has been winter breeding in late February to early March, while nearby cold-water populations breed in late-May. Metamorphosis of tadpoles, enhanced by the warm water, occurs as early as late-March. In 2008, Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) was documented in toadlets at the warm springs. Until 2005, as many as eight egg clutches and 25 breeding adults had been observed at the warm springs, after which the population declined. In 2017, novel spring breeding occurred in a cooler pond in the spring complex. Future observations will help determine whether the population is recovering and whether breeding phenology and habitat use have changed.

scholarly journals Significant reductions of host abundance weakly impact infection intensity of Batrachochytrium dendrobatidis

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242913
Author(s):  
Jaime Bosch ◽  
Luis M. Carrascal ◽  
Andrea Manica ◽  
Trenton W. J. Garner
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Infection Intensity ◽  
Natural World ◽  
Natural Habitats ◽  
Amphibian Species ◽  
Host Abundance ◽  
Amphibian Larvae ◽  
Severity Of The Disease ◽  
The Impact ◽  
Salamander Larvae

Infectious diseases are considered major threats to biodiversity, however strategies to mitigate their impacts in the natural world are scarce and largely unsuccessful. Chytridiomycosis is responsible for the decline of hundreds of amphibian species worldwide, but an effective disease management strategy that could be applied across natural habitats is still lacking. In general amphibian larvae can be easily captured, offering opportunities to ascertain the impact of altering the abundance of hosts, considered to be a key parameter affecting the severity of the disease. Here, we report the results of two experiments to investigate how altering host abundance affects infection intensity in amphibian populations of a montane area of Central Spain suffering from lethal amphibian chytridiomycosis. Our laboratory-based experiment supported the conclusion that varying density had a significant effect on infection intensity when salamander larvae were housed at low densities. Our field experiment showed that reducing the abundance of salamander larvae in the field also had a significant, but weak, impact on infection the following year, but only when removals were extreme. While this suggests adjusting host abundance as a mitigation strategy to reduce infection intensity could be useful, our evidence suggests only heavy culling efforts will succeed, which may run contrary to objectives for conservation.

scholarly journals Evaluation of the bacterial and fungal microbiome on the skin of Anaxyrus boreas, Rhinella marina, and Xenopus laevis and implications related to Batrachochytrium dendrobatidis susceptibility

2020 ◽  
Author(s):  
Moamen M. Elmassry ◽  
Scot Dowd ◽  
Cynthia Carey ◽  
Michael J. San Francisco
Keyword(s):  
Xenopus Laevis ◽  
Batrachochytrium Dendrobatidis ◽  
Research Area ◽  
Skin Microbiome ◽  
Amphibian Species ◽  
Rhinella Marina ◽  
Resistant Species ◽  
Frog Species ◽  
Fungal Microbiome ◽  
Anaxyrus Boreas

ABSTRACTThe skin and its microbiome are the first lines of defense against environmental stressors and pathogens. The symbiotic relationships between the host and the microbiome and within the microbiome are critical to host health. In frogs, this research area is lacking especially in the context of their skin infection with Batrachochytrium dendrobatidis. B. dendrobatidis is a major fungal skin pathogen to amphibians that has caused the extinction of hundreds of amphibian species populations. While some frog species are known susceptible to B. dendrobatidis infections, and others are resistant, we hypothesized that the skin microbiome of frogs plays a role in the prevention of B. dendrobatidis infections that is yet unknown. Therefore, in this work we have examined the bacterial and fungal skin microbiome of one species that is sensitive to B. dendrobatidis infections, Anaxyrus boreas (formerly: Bufo boreas), and the resistant species, Xenopus laevis and Rhinella marina (formerly: Bufo marinus). This was accomplished using tag-encoded FLX amplicon pyrosequencing (bTEFAP) of the 16S rRNA and ITS DNA regions. Our results showed that the bacterial and fungal skin microbiome of A. boreas and R. marina were more similar than to that of X. laevis. We found distinct patterns between the skin microbiome of B. dendrobatidis sensitive and resistant frog species. For the bacterial microbiome, the most abundant bacterial genus observed in all frog samples was Microbacterium. The resistant species had higher abundance in the genera Pseudomonas, Sphingobium, Pedobacter, Variovorax, Morganella, Sphingomonas, Giesbergeria, and Agromyces. In contrast, they had lower abundance of Elizabethkingia (formerly: Flavobacterium), Enterobacter, Ochrobactrum, Arthobacter, Stenotrophomonas, Shinella, Klebsiella, Aeromonas, Comomonas, Chitinophaga, and Rhodococcus. Regarding the fungal microbiome, the resistant species showed higher abundance in the genera Aspergillus, Cladosporium, Elaphomyces, Monascus, Tritirachium, Ceratostomella, and Claviceps, while Asterotremella, Trichosporon, and Malasezzia genera were less represented in resistant species. We have also observed that in the resistant species, the skin microbiome had higher diversity in the fungal microbiota, but not in the bacterial microbiota. We speculate that those observed differences have implications in B. dendrobatidis susceptibility that are yet to be determined, possibly through competition for nutrients or the production of specific anti-fungal molecules.GRAPHICAL ABSTRACT

scholarly journals Fungal infection, decline and persistence in the only obligate troglodytic Neotropical salamander

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9763
Author(s):  
Mizraim Olivares-Miranda ◽  
Vance T. Vredenburg ◽  
Julio C. García-Sánchez ◽  
Allison Q. Byrne ◽  
Erica B. Rosenblum ◽  
...  
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Infection Intensity ◽  
Sampling Technique ◽  
Sympatric Species ◽  
Amphibian Declines ◽  
Small Range ◽  
Museum Specimens ◽  
Amphibian Species ◽  
Extant Population ◽  
Epidemic Wave

The fungal pathogen Batrachochytrium dendrobatidis (Bd) is implicated in global mass die-offs and declines in amphibians. In Mesoamerica, the Bd epidemic wave hypothesis is supported by detection of Bd in historic museum specimens collected over the last century, yet the timing and impact of the early stages of the wave remain poorly understood. Chiropterotriton magnipes, the only obligate troglodytic Neotropical salamander, was abundant in its small range in the decade following its description in 1965, but subsequently disappeared from known localities and was not seen for 34 years. Its decline is roughly coincident with that of other populations of Neotropical salamanders associated with the invasion and spread of Bd. To determine the presence and infection intensity of Bd on C. magnipes and sympatric amphibian species (which are also Bd hosts), we used a noninvasive sampling technique and qPCR assay to detect Bd on museum specimens of C. magnipes collected from 1952 to 2012, and from extant populations of C. magnipes and sympatric species of amphibians. We also tested for the presence of the recently discovered Batrachochytrium salamandivorans (Bsal), another fungal chytridiomycete pathogen of salamanders, using a similar technique specific for Bsal. We did not detect Bd in populations of C. magnipes before 1969, while Bd was detected at low to moderate prevalence just prior to and during declines. This pattern is consistent with Bd-caused epizootics followed by host declines and extirpations described in other hosts. We did not detect Bsal in any extant population of C. magnipes. We obtained one of the earliest positive records of the fungus to date in Latin America, providing additional historical evidence consistent with the Bd epidemic wave hypothesis. Genotyping results show that at least one population is currently infected with the Global Panzootic Lineage of Bd, but our genotyping of the historical positive samples was unsuccessful. The lack of large samples from some years and the difficulty in genotyping historical Bd samples illustrate some of the difficulties inherent in assigning causality to historical amphibian declines. These data also provide an important historical baseline for actions to preserve the few known remaining populations of C. magnipes.

scholarly journals Establishement of a national monitoring program based on environmental DNA for amphibians and the chytrid fungus Batrachochytrium dendrobatidis     

2021 ◽  
Vol 4 ◽  
Author(s):  
Omneya Osman ◽  
Johan Andersson ◽  
Tomas Larsson ◽  
Mats Töpel ◽  
Alexander Eiler
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
National Level ◽  
Monitoring Program ◽  
12S Rrna ◽  
Rrna Gene ◽  
Chytrid Fungus ◽  
Rana Arvalis ◽  
Amphibian Species ◽  
National Monitoring ◽  
Wide Range

National monitoring programs provide the basis for evaluating the integrity of ecosystems, their responses to disturbances, and the success of actions taken to conserve or recover biodiversity. In this study, we successfully established a national program for the invasive chytrid fungus Batrachochytrium dendrobatidis (Bd) based on dual TaqMan assays. Amphibian diversity based on metabarcoding of the mitochondrial 12S rRNA gene was also performed. Assays were optimized for sensitive detection of target species from a wide range of amphibian ponds with variable potential of inhibitions for eDNA based detection. An amphibian mock community of 5 species was used to validate the metabarcoding approach while internal standards were used in the case of the dual TaqMan assays. First sampling of over 170 ponds in Norway resulted in Bd detection in 12 environmental samples and one swab sample taken over multiple years indicating the establishment of Bd in Norway. Five amphibian species Bufo bufo, Lissotriton vulgaris, Triturus cristatus, Rana arvalis and Rana temporaria as predicted from data in long-term citizen science reporting systems were widely detected in the collected eDNA samples. Our large scale-monitoring program indicates a low risk of a Bd outbreak and amphibian decline caused by chytridiomycosis but continued monitoring is recommended in the future. These findings indicate that eDNA is an effective method to detect invasive species, and to monitor endangered amphibian species. Still, several shortcomings (such as PCR inhibitors and sample volume) were identified that need to be addressed to improve eDNA-based monitoring at the national level.

scholarly journals Ancestral chytrid pathogen remains hypervirulent following its long coevolution with amphibian hosts

2019 ◽  
Vol 286 (1904) ◽  
pp. 20190833 ◽  
Author(s):  
Minjie Fu ◽  
Bruce Waldman
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Population Declines ◽  
Amphibian Species ◽  
South Korean ◽  
Global Pandemic ◽  
Litoria Caerulea ◽  
Experimental Treatments ◽  
Amphibian Chytrid Fungus ◽  
Genomic Recombination ◽  
Blank Solution

Many amphibian species around the world, except in Asia, suffer morbidity and mortality when infected by the emerging infectious pathogen Batrachochytrium dendrobatidis (Bd). A lineage of the amphibian chytrid fungus isolated from South Korean amphibians (BdAsia-1) is evolutionarily basal to recombinant global pandemic lineages (BdGPL) associated with worldwide amphibian population declines. In Asia, the Bd pathogen and its amphibian hosts have coevolved over 100 years or more. Thus, resilience of Asian amphibian populations to infection might result from attenuated virulence of endemic Bd lineages, evolved immunity to the pathogen or both. We compared susceptibilities of an Australasian amphibian, Litoria caerulea , known to lack resistance to BdGPL, with those of three Korean species, Bufo gargarizans , Bombina orientalis and Hyla japonica , after inoculation with BdAsia-1, BdGPL or a blank solution. Subjects became infected in all experimental treatments but Korean species rapidly cleared themselves of infection, regardless of Bd lineage. They survived with no apparent secondary effects. By contrast, L. caerulea , after infection by either BdAsia-1 or BdGPL, suffered deteriorating body condition and carried progressively higher Bd loads over time. Subsequently, most subjects died. Comparing their effects on L. caerulea , BdAsia-1 induced more rapid disease progression than BdGPL. The results suggest that genomic recombination with other lineages was not necessary for the ancestral Bd lineage to evolve hypervirulence over its long period of coevolution with amphibian hosts. The pathogen's virulence may have driven strong selection for immune responses in endemic Asian amphibian host species.

scholarly journals Tracking Batrachochytrium dendrobatidis Infection Across the Globe

EcoHealth ◽  
2020 ◽  
Vol 17 (3) ◽  
pp. 270-279
Author(s):  
Federico Castro Monzon ◽  
Mark-Oliver Rödel ◽  
Jonathan M. Jeschke
Keyword(s):  
Systematic Review ◽  
Host Species ◽  
Batrachochytrium Dendrobatidis ◽  
Atlantic Coast ◽  
Amphibian Species ◽  
Species Overlap ◽  
The Usa

AbstractInfection records of Batrachochytrium dendrobatidis (Bd), a pathogen that has devastated amphibian populations worldwide, have rapidly increased since the pathogen’s discovery. Dealing with so many records makes it difficult to (a) know where, when and in which species infections have been detected, (b) understand how widespread and pervasive Bd is and (c) prioritize study and management areas. We conducted a systematic review of papers and compiled a database with Bd infection records. Our dataset covers 71 amphibian families and 119 countries. The data revealed how widespread and adaptable Bd is, being able to infect over 50% of all tested amphibian species, with over 1000 confirmed host species and being present in 86 countries. The distribution of infected species is uneven among and within countries. Areas where the distributions of many infected species overlap are readily visible; these are regions where Bd likely develops well. Conversely, areas where the distributions of species that tested negative overlap, such as the Atlantic Coast in the USA, suggest the presence of Bd refuges. Finally, we report how the number of tested and infected species has changed through time, and provide a list of oldest detection records per country.

scholarly journals Climate change correlates with rapid delays and advancements in reproductive timing in an amphibian community

2010 ◽  
Vol 278 (1715) ◽  
pp. 2191-2197 ◽  
Author(s):  
Brian D. Todd ◽  
David E. Scott ◽  
Joseph H. K. Pechmann ◽  
J. Whitfield Gibbons
Keyword(s):  
Climate Change ◽  
South Carolina ◽  
Community Dynamics ◽  
Niche Overlap ◽  
Reproductive Timing ◽  
Amphibian Species ◽  
Larval Amphibians ◽  
Amphibian Larvae ◽  
Air Temperatures ◽  
And Migration

Climate change has had a significant impact globally on the timing of ecological events such as reproduction and migration in many species. Here, we examined the phenology of reproductive migrations in 10 amphibian species at a wetland in South Carolina, USA using a 30 year dataset. We show for the first time that two autumn-breeding amphibians are breeding increasingly later in recent years, coincident with an estimated 1.2°C increase in local overnight air temperatures during the September through February pre-breeding and breeding periods. Additionally, two winter-breeding species in the same community are breeding increasingly earlier. Four of the 10 species studied have shifted their reproductive timing an estimated 15.3 to 76.4 days in the past 30 years. This has resulted in rates of phenological change that range from 5.9 to 37.2 days per decade, providing examples of some of the greatest rates of changing phenology in ecological events reported to date. Owing to the opposing direction of the shifts in reproductive timing, our results suggest an alteration in the degree of temporal niche overlap experienced by amphibian larvae in this community. Reproductive timing can drive community dynamics in larval amphibians and our results identify an important pathway by which climate change may affect amphibian communities.

scholarly journals Phylogenetic investigation of skin sloughing rates in frogs: relationships with skin characteristics and disease-driven declines

2019 ◽  
Vol 286 (1896) ◽  
pp. 20182378 ◽  
Author(s):  
Michel E. B. Ohmer ◽  
Rebecca L. Cramp ◽  
Craig R. White ◽  
Peter S. Harlow ◽  
Michael S. McFadden ◽  
...  
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Phylogenetic Signal ◽  
Interspecific Variation ◽  
Phylogenetic Position ◽  
Turnover Rates ◽  
Amphibian Skin ◽  
Amphibian Species ◽  
Wide Range ◽  
Skin Morphology ◽  
And Function

Amphibian skin is highly variable in structure and function across anurans, and plays an important role in physiological homeostasis and immune defence. For example, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis ( Bd ), but interspecific variation in sloughing frequency is largely unknown. Using phylogenetic linear mixed models, we assessed the relationship between skin turnover rate, skin morphology, ecological traits and overall evidence of Bd -driven declines. We examined skin sloughing rates in 21 frog species from three continents, as well as structural skin characteristics measured from preserved specimens. We found that sloughing rate varies significantly with phylogenetic group, but was not associated with evidence of Bd -driven declines, or other skin characteristics examined. This is the first comparison of sloughing rate across a wide range of amphibian species, and creates the first database of amphibian sloughing behaviour. Given the strong phylogenetic signal observed in sloughing rate, approximate sloughing rates of related species may be predicted based on phylogenetic position. While not related to available evidence of declines, understanding variation in sloughing rate may help explain differences in the severity of infection in genera with relatively slow skin turnover rates (e.g. Atelopus ).

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