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A brighter future for frogs? The influence of carotenoids on the health, development and reproductive success of the red-eye tree frog



Richard Preziosi, The University of Manchester, Oxford Road, Manchester M13 9PT, UK. Tel: +44 (0)161 275 5959



Ex situ conservation is an important tool for the prevention of species extinction in amphibians. Currently, there is limited information on the nutritional requirements of amphibians in captivity, and there have been anecdotal reports of skin colour degradation in captive amphibians. Amphibians use carotenoids for skin pigmentation, and because carotenoids are only obtainable through the diet, colour degradation could result from limited carotenoid availability. Studies of other vertebrate taxa have shown that carotenoids contribute to health and reproductive success; however, their importance to amphibians is currently unknown. We assessed the influence of carotenoids on the health and development of red-eye tree frogs (Agalychnis callidryas) during larval and post-metamorphic stages, and looked at effects on skin colour and reproductive success. Carry-over effects of larval exposure to carotenoids were also investigated, and the effects of carotenoids on skin colour development and degradation in adulthood were examined. Carotenoids did not significantly influence larval growth or survival; however, post-metamorphic carotenoid availability significantly increased growth rate in female but not in male frogs. Frogs fed a carotenoid diet post-metamorphosis had significantly redder skin than controls, and larval carotenoid exposure significantly influenced post-metamorphic skin colour. Fecundity was significantly higher in female frogs raised on a carotenoid diet post-metamorphosis compared with controls. Finally, skin colour did not change in adulthood despite changes in dietary carotenoid availability, which suggests that there is a critical period during post-metamorphic growth for deposition of carotenoids in the skin. We have shown that carotenoids influence the development, phenotype and reproductive success of A. callidryas, and these important nutrients should therefore be considered when nutritional recommendations for amphibians are made.

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