Influence of desiccation threat on the metamorphic traits of the Asian common toad, <em>Duttaphrynus melanostictus</em> (Anura)

Abstract

Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Duttaphrynus melanostictus under laboratory conditions. Newly hatched Gosner stage 19 tadpoles were exposed to decreasing water levels (gradually or rapidly) up to the beginning of metamorphic climax (MC, Gosner stage 42). The control group was reared in unchanging water levels. The tadpoles experiencing desiccation threat reached MC earlier than those reared in constant water levels and metamorphosed (Gosner stage 46) at smaller body sizes. Time to reach MC was comparable between the groups of tadpoles experiencing a gradual or rapid decrease in water levels but their size at the completion of metamorphosis varied. They emerged at a significantly smaller size under rapid desiccation threat compared to the gradual desiccation threat. Impact on size at emergence was in proportion to the level of desiccation threat and this accelerated development and led to an early metamorphosis. The study shows the ability of D. melanostictus for developmental plasticity under adverse ecological conditions like the desiccation threat.