Effects of Ethinylestradiol and the Fungicide Prochloraz on Metamorphosisand Thyroid Gland Morphology in Rana temporaria

摘要

Several environmental xenobiotics have been found to affect the metamorphosis of amphibians. In this studywe exposed tadpoles of the Common frog Rana temporaria from hatching to metamorphosis to two known endocrinedisruptors, the estrogenic pharmaceutical 17α-ethinylestradiol and the antiandrogenic/antiestrogenic fungicide prochlorazto determine their effect on 1) days to metamorphosis and size at metamorphosis, 2) body concentrations oftriiodothyronine (T3) and corticosterone, and 3) thyroid morphology. We found effects of both compounds on each ofthese response variables. A low dose of prochloraz (115 μg/l) and all doses of ethinylestradiol also caused a delay inmetamorphosis. T3 levels were elevated in metamorphs exposed to high concentration of prochloraz (252 μg/l) but thegroup showed a delay in metamorphosis. A low dose of prochloraz (115 μg/l) and all doses of ethinylestradiol also causeda delay in metamorphosis but no changes in T3 levels. The delayed metamorphs weighed more than controls. Thyroidhistology revealed significant differences in the high prochloraz exposure group only. Ethinylestradiol and prochloraz,however not in environmentally relevant doses, may therefore impact the thyroid axis, and may cause other sublethaleffects especially in combination with other stressors likely encountered.