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Dietary Carotenoid Supplementation Enhances the Cutaneous Bacterial Communities of the Critically Endangered Southern Corroboree Frog (Pseudophryne corroboree)


The rapid spread of infectious disease has resulted in the decline of animal populations globally. Amphibians support a diversity of microbial symbionts on their skin surface that help to inhibit pathogen colonisation and reduce disease susceptibility and virulence. These cutaneous microbial communities represent an important component of amphibian immune defence, however, very little is known about the environmental factors that influence the cutaneous microbiome. Here, we characterise the cutaneous bacterial communities of a captive colony of the critically endangered Australian southern corroboree frog, Pseudophyrne corroboree, and examine the effect of dietary carotenoid supplementation on bacterial abundance, species richness and community composition. Individuals receiving a carotenoid-supplemented diet exhibited significantly higher bacterial abundance and species richness as well as an altered bacterial community composition compared to individuals that did not receive dietary carotenoids. Our findings suggest that dietary carotenoid supplementation enhances the cutaneous bacteria community of the southern corroboree frog and regulates the presence of bacteria species within the cutaneous microbiome. Our study is the second to demonstrate that carotenoid supplementation can improve amphibian cutaneous bacterial community dynamics, drawing attention to the possibility that dietary manipulation may assist with the ex situ management of endangered species and improve resilience to lethal pathogens such as Batrachochytrium dendrobatidis (Bd).

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We would like to acknowledge Melbourne Zoo’s Herpetology Department for generating the southern corroboree frog eggs that we obtained and reared through to adulthood for use in this study. We also thank the staff of the Herpetofauna Division of Taronga Zoo for assistance and advice in preparing the captive facilities and husbandry requirements for these animals. We are grateful for the guidance and microbiology training provided by Dr Paul Thompson from Taronga Wildlife Hospital’s diagnostic pathology laboratory and for facilitating the MALDI-TOF MS identification of bacterial species that were unable to be identified using other techniques. We thank Alan Adolffson, Stephen Poon, Simon Goodfellow and Leesa Keogh for their additional microbiology assistance and advice throughout the experiment. Emma McInerney is acknowledged for her help with the care and husbandry of frogs during this experiment. This study was funded by grants awarded to PB and AS; the Australian Research Council (Linkage Grant LP140100808), NSW Environmental Trust (grant no. 2012/RD/0105) and the School of Biological Sciences, University of Wollongong.

Authors’ Contributions

AS and PB conceived the experiment. AS, PB and PH developed the methods. AS collected the skin swabs. CE collected the data. CE analysed the data with assistance from PB. AS wrote the paper with contributions from CE and PB.

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Correspondence to Aimee J. Silla.

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Ethics Statement

All procedures outlined in the present study were approved by the University of Wollongong Animal Ethics Committee (Protocol Number: AE13/13).

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Table S1

Results of pilot study determining optimal incubation temperature for culturing cutaneous bacteria. Data shown are bacteria species richness untransformed mean ± SEM (n = 6 per treatment) and bacterial abundance (CFU/plate) untransformed mean ± SEM (n = 6 per treatment). The result of a one-way ANOVA is shown by F d.f. and P values. Letters attached to each mean denote significant differences (P < 0.05) between dilution treatments as a result of a post hoc Tukey-Kramer HSD. (DOCX 16 kb)

Table S2

Unidentified bacteria species descriptions. (DOCX 14 kb)

Table S3

Bacteria species assemblages of individual carotenoid-supplemented (n = 22) and un-supplemented (n = 22) P. corroboree frogs. (DOCX 36 kb)

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Edwards, C.L., Byrne, P.G., Harlow, P. et al. Dietary Carotenoid Supplementation Enhances the Cutaneous Bacterial Communities of the Critically Endangered Southern Corroboree Frog (Pseudophryne corroboree). Microb Ecol 73, 435–444 (2017).

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