Carotenoid intake during early life mediates ontogenetic colour shifts and dynamic colour change during adulthood

Abstract

Carotenoids play an import role as one of the most prevalent pigments in animals. Carotenoid-based coloration accounts for striking sexually and naturally selected colour adaptations. Several anurans (frogs and toads) change body coloration either slowly and permanently between life stages (ontogenetic colour change), or rapidly and temporarily within minutes or hours (dynamic colour change). We investigated ontogenetic colour change from orange to green morphs in the Wallace's flying frog, Rhacophorus nigropalmatus , and tested the influence of dietary carotenoids on colour change during postmetamorphic development. At the age of 9 months, while all individuals still possessed orange-red body coloration, a 20-week-long feeding experiment was performed by supplying the frogs with either no carotenoid supplements or dietary carotenoids once or four times per week. A high carotenoid diet resulted in a faster increase in green colour chroma as well as higher levels of green and carotenoid chroma of back coloration. Less or no carotenoid supplementation led to an increase in UV-blue chroma, contributing to a dull turquoise appearance often observed in captive-bred and captive-raised anurans. In addition, we showed for the first time that Wallace's flying frogs also perform dynamic colour changes. We tested dynamic changes triggered either by 2 min tactile handling or varying 1 h dark and light conditions. Our results demonstrate that a high carotenoid diet facilitates rapid and reversible change of body coloration in response to a tactile stressor, an adaptation absent in frogs receiving no carotenoids. Dynamic colour changes were likewise observed in response to changing light conditions presumably camouflaging individuals and providing protection from UV irradiation. The ontogenetic and dynamic pigmentation changes are discussed in relation to mechanism and as a likely strategy to avoid predation both at different life stages and in different environments. • Dietary carotenoids impact the development of the green back coloration of frogs. • Lack of carotenoids increase UV-blue chroma, contributing to turquoise appearance. • Early life acquisition of carotenoids regulates dynamic colour change behaviour. • Light conditions mediate reversible full and partial body colour change of frogs.