Warmer temperature and provision of natural substrate enable earlier metamorphosis in the critically endangered Baw Baw frog.

Deon J Gilbert,Phillip G Byrne,Michael J L Magrath

doi:10.1093/conphys/coaa030

Deon J Gilbert, Phillip G Byrne + Show 1 more

Open Access

https://doi.org/10.1093/conphys/coaa030

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Abstract

Temperature and food availability are known to independently trigger phenotypic change in ectotherms, but the interactive effects between these factors have rarely been considered. This study investigates the independent and interactive effects of water temperature and food availability on larval growth and development of the critically endangered Baw Baw frog, Philoria frosti. Larvae were reared at low (12°C) or high (17°C) water temperature in the absence or presence of substrate that controlled food availability, and body size and time to metamorphosis were quantified. Growth and development of larvae was influenced by the individual effects of temperature and food availability; time to metamorphosis was shorter in warm water treatment groups and in the presence of substrate and increased food. Unexpectedly, however, water temperature and food availability did not have an interactive effect on either time to metamorphose or body size at metamorphosis. Under all treatment groups, metamorphic onset occurred once a developmental size threshold was reached, indicating that growth rate and body size are key factors controlling the metamorphic process in Baw Baw frogs (consistent with the Wilbur-Collins model for ectotherm development). From an applied perspective, our findings have implications for amphibian conservation because they indicate that simple manipulations of temperature and food availability can be used to increase the rate of frog production in conservation breeding programs.

Highlights

During ontogeny, individuals of many species respond to environmental changes by altering their phenotype so as to maximize their probability of survival and reproductive success (Sultan, 1995; Jannot, 2009; Tejedo et al, 2010)
In weeks 2, 3 and 4, there was a significant effect of temperature treatment on body size, with tadpoles in the warmer treatments being larger than those in the cooler treatments
In week 5, there was no significant effect of temperature or substrate treatment on tadpole body size

Summary

Introduction

Individuals of many species respond to environmental changes by altering their phenotype so as to maximize their probability of survival and reproductive success (Sultan, 1995; Jannot, 2009; Tejedo et al, 2010). The ‘temperature size rule’ (TSR) predicts that ectotherms developing at colder temperatures will have a slower growth rate, a longer larval duration and a larger body size at metamorphosis (Atkinson, 1994). This rule has been extensively tested under controlled laboratory conditions, and the general finding is that ectotherms adhere to the TSR (Angilletta et al, 2004; Walters and Hassall, 2006). In a review of empirical studies spanning bacterium, protists, plants and animals, Atkinson (1994) reported that 83.5% of 97 species (109 studies) showed decreased developmental size with increased temperature, lending further support to the TSR

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