Meeting Abstract
Direct development is a life-history strategy that has evolved independently in at least a dozen amphibian lineages. Direct-developing frogs, including the Puerto Rican coquí, Eleutherodactylus coqui, typically hatch from terrestrial eggs as miniature adults. Their embryonic development is characterized by precocious formation of adult features, such as limbs, and modified features such as a highly vascularized tail used for respiration. Embryos of E. coqui undergo morphological changes mediated by thyroid hormone (TH) that mirror those at metamorphosis. TH also modulates metamorphosis, a fundamental amphibian life history trait, in indirect developing frogs. Because TH has widespread and diverse effects throughout metamorphosis, changes in TH signaling could underlie the evolution of direct development. Specifically, changes in temporal or spatial expression of peripheral TH regulators, such as the nuclear thyroid receptor α (TRα) or thyroid receptor β (TRβ) could coordinate the heterochronic shift in metamorphic events observed during embryogenesis. Quantitative real-time PCR was used to quantify transcript levels of TRα and TRβ in the limbs and tail at key developmental stages. LC-MS was used to determine the corresponding thyroid hormone profile at these stages. These data inform our understanding of the role of hormones in direct development and the evolution of this successful life-history strategy.
