Carotenoids and amphibians: effects on life history and susceptibility to the infectious pathogen, Batrachochytrium dendrobatidis.

Rickey D Cothran,Jenny Urbina,Cindy Murray,Paul W Bradley,Beverly J French,Rick A Relyea,Andrew R Blaustein,Stephanie S Gervasi

doi:10.1093/conphys/cov005

Abstract

Carotenoids are considered beneficial nutrients because they provide increased immune capacity. Although carotenoid research has been conducted in many vertebrates, little research has been done in amphibians, a group that is experiencing global population declines from numerous causes, including disease. We raised two amphibian species through metamorphosis on three carotenoid diets to quantify the effects on life-history traits and post-metamorphic susceptibility to a fungal pathogen (Batrachochytrium dendrobatidis; Bd). Increased carotenoids had no effect on survival to metamorphosis in gray treefrogs (Hyla versicolor) but caused lower survival to metamorphosis in wood frogs [Lithobates sylvaticus (Rana sylvatica)]. Increased carotenoids caused both species to experience slower development and growth. When exposed to Bd after metamorphosis, wood frogs experienced high mortality, and the carotenoid diets had no mitigating effects. Gray treefrogs were less susceptible to Bd, which prevented an assessment of whether carotenoids could mitigate the effects of Bd. Moreover, carotenoids had no effect on pathogen load. As one of only a few studies examining the effects of carotenoids on amphibians and the first to examine potential interactions with Bd, our results suggest that carotenoids do not always serve amphibians in the many positive ways that have become the paradigm in other vertebrates.

Highlights

Animal diets provide energy and nutrients that are essential to life
For survival to metamorphosis (Fig. 1), we found no effect of the carotenoid diets on wood frogs
To test whether carotenoid diet affected the final mass of the animals immediately before the Batrachochytrium dendrobatidis (Bd) exposure stage of the experiment, we used a generalized linear model

Summary

Introduction

Animal diets provide energy and nutrients that are essential to life. Carotenoids are one such group of nutrients; they consist of more than 600 pigments that are categorized as either carotenes or xanthophylls (both are comprised of hydrocarbon chains, but carotenes contain no oxygen whereas xanthophylls containoxygen; Pérez-Rodríguez, 2009). Animal diets provide energy and nutrients that are essential to life. Carotenoids are one such group of nutrients; they consist of more than 600 pigments that are categorized as either carotenes or xanthophylls 1993; Hill, 1995; Vershinin, 1999; Alonso-Alvarez et al, 2004; but see Costantini et al, 2007; Pérez-Rodríguez, 2009). Animals fed diets higher in carotenoids should be less susceptible to many pathogens and diseases; this prediction has been supported in a number of animal species, including humans (Bendich, 1993; Skarstein and Folstad, 1996; Horak et al, 2001; Hill and Farmer, 2005; Babin et al, 2010)

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Results

Discussion

Conclusion