Understanding the interactions of diet and lighting on frogs and their symbiotic bacteria to improve ex situ husbandry of amphibians

Citation

Antwis RE, Michaels CJ, Preziosi R, and Fidgett AL. 2015. Understanding the interactions of diet and lighting on frogs and their symbiotic bacteria to improve ex situ husbandry of amphibians. In Bissell H, Brooks M Eds. Proceedings of the Eleventh Conference on Zoo and Wildlife Nutrition, AZA Nutrition Advisory Group, Portland, OR.

Abstract

Amphibians are undergoing massive population declines in the wild, in part due to infectious diseases including chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). In response, amphibian populations are being maintained in ex situ breeding programs while viable treatments for chytridiomycosis are developed. One potential action involves the use of symbiotic bacteria from the skin of amphibians; however multiple factors likely affect the success of such probiotic applications. Disturbances in the natural microbiota of amphibians may alter individual susceptibility to pathogens and disrupt any probiotic treatments that may have previously been applied. Studies have found wild populations of amphibians show large variation in bacterial communities according to host species and location, thus conservation efforts may require baseline data for specific species and populations. The bacterial community of an individual is influenced by its biotic and abiotic environment, and amphibians in the wild receive relatively high exposure to bacteria through environmental and conspecific interactions. Conversely, the captive environment likely provides lower environmental heterogeneity and reduced conspecific interactions, potentially resulting in lower exposure to bacteria. Therefore there may be species- and institution-specific responses of the amphibian microbiota to the captive environment.  Varying dietary and environmental conditions provided in captivity may also lead to differences in the microbial community, potentially leaving captive amphibians with compromised immunity to infectious diseases, such as the fungal pathogen Batrachochytrium dendrobatidis (Bd), which could be particularly significant for populations intended for reintroduction. The development of treatments against Bd will need to consider a range of complexities regarding the microbial ecology of symbiotic bacterial communities on the skin of amphibians, particularly in the context host-microbe-environment interactions.  The purpose of this research was to determine the impact of husbandry practices on symbiotic bacterial communities of frogs maintained at Chester Zoo and the University of Manchester.  Specifically, the research aimed to:

• investigate the effect of a carotenoid-rich diet on symbiotic bacterial communities of red-eyed tree frogs, and

• assess the effects of varying ultraviolet light provision and calcium diets on growth, body condition and symbiotic bacterial communities of red-eyed tree frogs.

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