Meeting Abstract
Thyroid hormones play a critical role in metamorphosis in most amphibians, driving growth, development and tissue differentiation, whereas corticosterone (C) action is more complex and less known. We tested for changes in their levels in tadpoles exposed to PBDE, which is known to slow tadpole development and growth, and at different temperature, which is also known to alter development and growth. We raised leopard frog tadpoles at 23 and 28° C from the free-swimming stage (Gosner Stage (GS) 25) through the end of metamorphic climax (GS 46) on diets with 0 (control), 10 and 50 ng/g PBDE. Animals were collected at 6 developmental stages (GS 28, 31, 37, 41, 42 and 46) for whole-body determinations of triiodothyronine (T3), thyroxine (T4) and C via ELISA. A pronounced peak in T3 concentrations at metamorphic climax (GS 42) was observed in control animals raised at both temperatures (P=0.01). PBDE-exposed animals at both temperatures, however, failed to show this rise during metamorphic climax (P>0.3). C concentrations showed a progressive increase in control animals raised at both temperatures, reaching significantly higher concentrations at the end of metamorphic climax (GS 42 and 46). Exposed animals also presented a similar pattern, but levels were higher at early stages (P=0.01). Taken together, our results indicate that both oral exposure to environmentally relevant concentrations of PBDE as well as warmer temperatures, induce hormonal alterations in developing Lithobates pipiens, suggesting that, in addition to environmental contamination, a warming change scenario might also interfere with their hormone secretion. Support from CNPq (postdoctoral fellowship M.F.) and Sea Grant NOAA (NA10OAR4170070, Proj R/HCE-14).
