Effects of acute and chronic exposure to the xenoestrogen octhylfenol on early life stages of Chaunus (Bufo) arenarum (Amphibia, Anura).

Y. PIAZZA.; F. LO NOSTRO; M. C. MAGGESE; V. TRUDEAU; F. MEIJIDE

Montevideo, Uruguay

Congreso; VIII Congreso SETAC Latinoamérica; 2007

SETAC Latinoamérica

Endocrine disrupting compounds (EDCs) are often detected in the aquatic environment and can negatively affect the health of wildlife populations. However, little is known about the sensitivity of native amphibians to EDCs. Alkylphenols, such as 4-tert-octylphenol (OP), are biodegradation products of non-ionic surfactants used in domestic and industrial activities and exhibit estrogenic effects. In amphibians, the hormonal environment present during a critical period of larval development may have influence on gonadal sex differentiation; then this process may be affected by the exposure to EDCs. In this study we assessed OP acute toxicity on larval stages of Chaunus arenarum and evaluated the effect of chronic exposure to environmentally relevant concentrations of this xenoestrogen on gonadal development and sex differentiation. OP was more toxic to larvae at stage 26 (premetamorphosis) than at stage 36 (prometamorphosis), exhibiting LC50–96 h of 251,8 mg/l and 383,4 mg/l, respectively. In subsequent experiments, animals were exposed until 55 days post-metamorphosis to 5, 25 and 125 mg/l OP and 10 mg/l E2 (positive control) via immersion in a static-renewal system. Larval mortality was recorded for each treatment. At the end of the experiments, sex was determined by gross gonadal inspection and later confirmed by histology. 125 mg/l OP caused a significant mortality after chronic exposure, as compared to the other concentrations and the vehicle control. In the surviving juveniles, OP did not affect gonad development nor sex ratios, unlike E2 which showed a feminizing effect, even when exposure was done only during the larval period.