Inability of yellow-bellied toad to accelerate metamorphosis in desiccation conditions

Abstract

Many amphibian species inhabit temporary aquatic habitats for reproduction to maximize larval growth under favorable conditions, but accelerate developmental rate to rapidly undergo metamorphosis under stress conditions when high desicca- tion risk exists. Desiccation affects different aspects of amphibian biology such as developmental rate, body size and mass, and growth rate. We studied the responses of yellow-bellied toad (Bombina variegata) to different water levels (constant high, decreasing water level, and constant low water level) in the laboratory using indi- viduals collected from natural ponds. To assess the effects of experimental pond drying, we investigated the effects on life-history and morphological traits at meta- morphosis as well as carry-over effects on post-metamorphic traits and locomotor performances. We found that B. variegata cannot accelerate developmental rate in response to pond drying. The metamorphs from decreasing and constant low water levels had similar size, mass, growth rate and body condition indices at metamorphosis, and all these traits were lower than in the constant high water level treatment. These changes in life-history traits at metamorphosis did not affect tail shape although they had carry-over effects on life-history and morphological traits after metamorphosis. Post-metamorphic individuals reared in desiccation treatments had similar but smaller lengths of femur and tibiofibula, but these changes did not have negative consequences on jumping performances. We show that responsiveness to pond drying of B. variegata is probably associated with maximum growth rate in favorable conditions and inability to increase growth rate as well as developmental rate in desiccation conditions. This resulted in prolonged developmental time to reach the minimum size and mass for metamorphosis.