Over-wintering tadpoles of Mixophyes fasciolatus act as reservoir host for Batrachochytrium dendrobatidis

Edward J Narayan; Clara Graham; Hamish McCallum; Jean-Marc Hero

doi:10.1371/journal.pone.0092499

Over-wintering tadpoles of Mixophyes fasciolatus act as reservoir host for Batrachochytrium dendrobatidis

PLoS One. 2014 Mar 19;9(3):e92499. doi: 10.1371/journal.pone.0092499. eCollection 2014.

Authors

Edward J Narayan¹, Clara Graham², Hamish McCallum², Jean-Marc Hero¹

Affiliations

¹ Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast Campus, Queensland, Australia.
² Environmental Futures Research Institute, School of Environment, Griffith University, Nathan Campus, Queensland, Australia.

Abstract

Batrachochytrium dendrobatidis (Bd), a cutaneous amphibian fungus that causes the lethal disease chytridiomycosis, has been implicated as a cause of many amphibian declines. Bd can tolerate low temperatures with an optimum thermal range from 17-24°C. It has been shown that Bd infection may result in species extinction, avoiding the transmission threshold presented by density dependent transmission theory. Prevalence of Bd during autumn and winter has been shown to be as low as 0% in some species. It is currently unclear how Bd persists in field conditions and what processes result in carry-over between seasons. It has been hypothesised that overwintering tadpoles may host Bd between breeding seasons. The Great Barred Frog (Mixophyes fasciolatus) is a common, stable and widespread species in Queensland, Australia, and is known to carry Bd. Investigation into Bd infection of different life stages of M. fasciolatus during seasonally low prevalence may potentially reveal persistence and carry-over methods between seasons. Metamorphs, juveniles, and adults were swabbed for Bd infection over three months (between March and May, 2011) at 5 sites of varying altitude (66 m-790 m). A total of 93 swabs were analysed using Polymerase Chain Reaction (PCR) real-time analysis. PCR analysis showed 6 positive (1 excluded), 4 equivocal and 83 negative results for infection with Bd. Equivocal results were assumed to be negative using the precautionary principle. The 5 positive results consisted of 4 emerging (Gosner stage 43-45) metamorphs and 1 adult M. fasciolatus. Fisher's exact test on prevalence showed that the prevalence was significantly different between life stages. All positive results were sampled at high altitudes (790 m); however prevalence was not significantly different between altitudes. Infection of emerging metamorphs suggests that individuals were infected as tadpoles. We hypothesise that M. fasciolatus tadpoles carry Bd through seasons. Thus, Mixophyes fasciolatus may act as disease reservoirs at multiple life stages.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amphibians / microbiology*
Animals
Chytridiomycota / pathogenicity*
Larva / microbiology*

Grants and funding

This research was supported by the Griffith University Environmental Futures Centre, as part of CG's honours thesis. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.