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Nov 28, 2011

Does it matter if you are dull?

Does it matter if you are dull?  How carotenoids affect fitness in frogs

Amphibians are facing an extinction crisis and for many species managed breeding programmes have become necessary for their conservation; yet understanding of amphibian nutritional requirements is currently limited.

Anecdotal reports suggest captive bred amphibians have duller skin colouration than wild members of the same species. Many amphibians use carotenoid (yellow-red) pigments in their skin, however vertebrates cannot make these compounds themselves and frogs must instead rely entirely on dietary sources.

Carotenoids are known to also function in the immune, antioxidant and reproductive systems of other vertebrate taxa, so dietary deficiencies could impact not just on colour of frogs, but also their health and reproduction. Research focussed on two neotropical Hylid tree frog species, the redeyed tree frog (Agalychnis callidryas) and Morelet's tree frog (Agalychnis moreletii), both characterised by brightly coloured skin. Observations of wild frogs found carotenoid-based skin colouration involved in mate selection; brightly coloured females mate with brightly coloured males.

In captivity, skin colour degrades quickly but was improved by dietary supplementation during specific developmental periods post-metamorphosis, from tadpole to adult. Post-metamorphic carotenoid availability positively influenced growth, skin colour and reproductive success. Studies also found carotenoid availability to captive frogs was low unless provided with feeder invertebrates recently gut-loaded on carotenoid-rich foods.

Hylid frogs were studied yet it may be possible to extrapolate findings to species from other families and to the preparation of nutritional recommendations for frogs, thereby improving the fitness of captive-bred individuals and increasing the success of ex-situ conservation programmes.

Chester Zoo

COMMENDATION received in BIAZA Awards 2011 for Best research project

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