High chytrid prevalence and infection intensities in tadpoles of Mixophyes fleayi

Matthijs Hollanders; Laura F. Grogan; Hamish I. McCallum; David A. Newell

doi:10.1071/WR23126

RESEARCH ARTICLE (Open Access)

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High chytrid prevalence and infection intensities in tadpoles of Mixophyes fleayi

Matthijs Hollanders

^A ^* , Laura F. Grogan ^B ^C ^D , Hamish I. McCallum ^B ^C and David A. Newell ^A

+ Author Affiliations

- Author Affiliations

^A Faculty of Science and Engineering, Southern Cross University, Lismore, NSW, Australia.

^B Centre for Planetary Health and Food Security, Griffith University, Southport, Qld, Australia.

^C School of Environment and Science, Griffith University, Southport, Qld, Australia.

^D School of the Environment, University of Queensland, St Lucia, Qld, Australia.

^* Correspondence to: matthijs.hollanders@gmail.com

Handling Editor: Thomas Prowse

Wildlife Research 51, WR23126 https://doi.org/10.1071/WR23126

Submitted: 7 October 2023 Accepted: 17 August 2024 Published: 30 September 2024

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has caused catastrophic biodiversity loss globally, but species and life stages within species respond differently to the pathogen. Although tadpoles are often reported to be less vulnerable to disease, they can constitute important infection reservoirs in ecosystems.

Aims

We aimed to describe Bd infection patterns of a long-lived tadpole in a species where post-metamorphic animals appear to exhibit limited mortality as a result of chytridiomycosis. We further investigated how oral dekeratinisation can be used as an indicator of infection.

Methods

We conducted surveys of tadpoles of Mixophyes fleayi (Fleay’s barred frog) over 2 years, at two rainforest streams on the east coast of Australia, to assess patterns in Bd infection prevalence and intensity. We developed an integrated hierarchical model propagating pathogen-detection errors and incorporating how Bd infections affect oral dekeratinisation.

Key results

We found that Bd infection prevalence was strongly associated with lower temperatures and a larger body size, consistent with Bd optimal thermal range and a cumulative risk of exposure for tadpoles. The individual probability of a tadpole being infected with Bd was estimated to be 0.58 [95% HPDI: 0.432, 0.713], the odds of which were approximately eight times greater than for adults at the same sites. Tadpoles infected with Bd were 113 [29, 293] times more likely to have oral dekeratinisation than were uninfected tadpoles, where uninfected individuals were estimated to have a 0.05 [95% HPDI: 0.011, 0.11] probability of having mouthpart loss.

Conclusions

Our results showed that M. fleayi tadpoles are more likely to be infected with Bd than are adults, suggesting that tadpoles could contribute to Bd maintenance in streams. We further showed that sites can be rapidly assessed for Bd by visually checking for oral dekeratinisation.

Implications

Long-lived tadpoles, in general, may contribute to Bd maintenance in ecosystems. We suggest continued exploration of Bd immunocompetence across amphibian life stages to further understand the vastly different infection patterns.

Keywords: amphibian, Batrachochytrium dendrobatidis, chytridiomycosis, dekeratinisation, mouthpart loss, pathogen detection, pathogen load, tadpole.

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