Pond drying conditions do not alter whole-body corticosterone content and metamorphic time of yellow-bellied toad (Bombina variegata) metamorphs

Abstract

Amphibian species that inhabit temporary ponds for reproduction maximize larval growth under favorable conditions and accelerate their development to undergo rapid metamorphosis under stressful conditions such as pond drying. Corticosterone controls development, metabolism, and growth, and has an invaluable role in anuran metamorphosis under stress conditions. In this study, we evaluated whether the whole-body corticosterone (CORT) level is related to drying conditions in species that cannot accelerate the developmental rate in response to pond drying. Specifically, we investigated the effects of different water levels in combination with exogenous CORT and corticosteroid synthesis inhibitor metyrapone (treatments: high water level, high water level with exogenous CORT, low water level, low water level with metyrapone) on the whole-body corticosterone (at prometamorphosis and metamorphic climax), life history and morphological traits at the metamorphic climax. We found that these conditions did not alter the whole-body content of CORT and the developmental rate in treatments, although low water levels and exogenous CORT in high water level negatively affected other life history traits and tail shape. Individuals from a high water level with exogenous CORT had the smallest body size and mass and changed tail shape at metamorphosis, while changes in life history traits did not affect the tail shape in the other treatments. Our findings indicate that the absence of developmental response (i.e. canalized development) in the timing of metamorphosis of B. variegata may be explained by a modification of endocrine regulation but further studies that would include closely related species are required.