Dietary carotenoids change the colour of Southern corroboree frogs

Abstract

Animal coloration can be the result of many interconnected elements, including the production of colourproducing molecules de novo, as well as the acquisition of pigments from the diet. When acquired through the diet, carotenoids (a common class of pigments) can influence yellow, orange, and red coloration and enhanced levels of carotenoids can result in brighter coloration and/or changes in hue or saturation. We tested the hypothesis that dietary carotenoid supplementation changes the striking black and yellow coloration of the southern corroboree frog (Pseudophryne corroboree, Amphibia: Anura). Our dietary treatment showed no measurable difference in colour or brightness for black patches in frogs. However, the reflectance of yellow patches of frogs raised on a diet rich in carotenoids was more saturated (higher chroma) and long-wave shifted in hue (more orange) compared to that of frogs raised without carotenoids. Interestingly, frogs with carotenoid-poor diets still developed their characteristic yellow and black coloration, suggesting that their yellow colour patches are a product of pteridines manufactured de novo. Running Title: Colouration of corroboree frogs ABSTRACT Animal colouration can be the product of many interconnected elements including the production of colour-producing molecules de novo and from the acquisition of pigments from diet. When acquired through diet, carotenoids (a common class of pigments), can influence yellow, orange and red colouration; enhanced levels of carotenoids result in brighter colouration and/or changes in hue or saturation. We tested the hypothesis that dietary carotenoid supplementation can change the striking black and yellow colouration of the southern corroboree frog (Pseudophryne corroboree, Amphibia: Anura). Our dietary treatment showed no measurable difference in colour or brightness for the frogs' black patches. However, the reflectance of the yellow patches of frogs raised on a diet rich in carotenoids were more saturated (higher chroma) and long-wave shifted in hue (more orange) than those frogs raised without carotenoids.Interestingly, frogs with carotenoid-poor diets still developed their characteristic yellow and black colouration suggesting that their yellow colour patches are a product of pteridines manufactured de novo.

Testing the effect of dietary carotenoids on larval survival, growth and development in the critically endangered southern corroboree frog

“…However, because the natural diet of southern corroboree frog larvae consists of algae and detritus known to be rich in carotenoids (Eeva, Helle, Salminen, & Hakkarainen, 2010;Osborne, 1991), an inability to utilize these micronutrients seems unlikely. Furthermore, using the same dietary manipulation experiment detailed in the present study, we have previously shown that access to carotenoids during the larval and post-metamorphic life stages improves P. corroboree exercise performance and skin coloration (Umbers, Silla, Bailey, Shaw, & Byrne, 2016). Additionally, we have recently discovered that dietary carotenoids improve the diversity of skin bacteria typically associated with anuran immunity (Edwards, Byrne, Harlow, & Silla, 2017).…”

“…Although our study provided no evidence that carotenoids improve the growth and development of larval P. corroboree , it is important to recognize that it also provided no evidence that carotenoids are detrimental to larvae, as has been reported for some other threatened frog species (Cothran et al, ). This is important because we have recently discovered that supplying southern corroboree frogs with dietary carotenoids at the dose reported in the present study significantly improves coloration and locomotory performance (Silla et al, ; Umbers et al, ), as well as the diversity and abundance of skin bacteria, known to play a role in anuran immunity (Edwards et al, ). As such, while including carotenoids in the diet of captive southern corroboree frogs may not improve larval survival, growth and development, controlling access to these micronutrients could be used to manipulate other phenotypic traits known to strongly influence anuran fitness.…”

Dietary Carotenoid Supplementation Enhances the Cutaneous Bacterial Communities of the Critically Endangered Southern Corroboree Frog (Pseudophryne corroboree)

“…Of note, results from our laboratory show no significant effect of carotenoid supplementation on juvenile or postmetamorphic growth, development or survival of P. corroboree (Byrne and Silla unpublished data). Additionally, supplementing southern corroboree frogs with the carotenoid dose used in the present study has recently been shown to enhance colouration and escape performance [ 22,38 ]. Given the positive effects of this concentration of dietary carotenoids on other fitness determining traits, we predict that the enhanced cutaneous bacterial communities reported will translate to increased immunity in this species.…”

Educating the enemy: Harnessing learned avoidance behavior in wild predators to increase survival of reintroduced southern corroboree frogs

“…We thus used humans as a proxy for predators to measure detectability, as is commonplace in sensory ecology, because unlike wild bird predators humans can tell us when they see a model (Bergeron & Fuller, ; Mappes, Kokko, Ojala, & Lindström, ; Seddon, Tobias, Eaton, & Ödeen, ). Although human vision differs from bird vision in that we do not detect ultraviolet, Southern Corroboree Frogs do not reflect in the ultraviolet, so humans can see the complete reflectance of Corroboree Frog coloration (Figure , Umbers, Silla, Bailey, Shaw, & Byrne, ). Our hypothesis was that the model types differed in their detectability.…”