Captive conditions influence amphibian skin microbes

The Panamanian golden frog (Atelopus zeteki) currently only exists in captivity. Photo by Matthew Becker.

The Panamanian golden frog (Atelopus zeteki) currently only exists in captivity, meaning that its microbial skin community has probably changed considerably. Photo by Matthew Becker.

As amphibians decline around the globe, more and more species are being pulled into captivity to initiate breeding programs for population insurance purposes. However, there is some speculation as to whether this is actually a viable method of species conservation, since captive frogs are eventually going to become different from their wild counterparts. In fact, their microbial communities most likely dramatically change within a matter of weeks of them being taken into captivity. A new study by in the open access journal PLoS ONE reveals that microbial diversity not only declines precipitously in captivity, but diet can have a significant effect on the microbial community. The authors conducted a simple experiment where captive bred red-eyed tree frogs (Agalychnis callidryas) were fed either crickets gut-loaded with a carotenoid-rich diet, or crickets that were not gut-loaded with carotenoids. The results showed that captive red-eyed tree frogs fed carotenoids had more diverse skin microbiota, indicating that carotenoids could influence the survival of skin bacteria.

Antwis et al. fed captive  red-eyed tree frogs (Agalychnis callidryas) diets rich in carotenoids and carotenoid-free diets to test the effect of diet on skin microbe communities.

Antwis et al. fed captive red-eyed tree frogs (Agalychnis callidryas) diets rich in carotenoids and carotenoid-free diets to test the effect of diet on skin microbe communities.

Amphibian guts are thought to serve as a reservoir of microbial diversity for the amphibian skin (see Wiggins et al. 2011 for an example from redback salamanders). Therefore, not only environment but also diet in captivity could be resulting in the dramatic declines in microbial biodiversity seen on amphibian skin. This has a lot of conservation implications since species being maintained in captivity may lose disease resistance due to having a less diverse skin community. Further studies are needed to tease apart the diversity = disease resistance hypothesis regarding amphibian skin microbes. If it is the case that all of the captive frogs are becoming less resistant to the amphibian chytrid fungus, perhaps there are husbandry changes that can be made to boost the skin microbe communities of the frogs, such as including probiotics into the substrate used for housing the frogs, or utilizing more natural tank conditions rather than just sanitary paper towels and plastic dishes.

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