Toxic effects of bisphenol A on sexual and asexual reproduction in Hydra oligactis

Hydra oligactis, an evolutionarily primitive invertebrate, produced eggs or testes (sexual reproduction) when starved at 10 degrees C, and produced buds (asexual reproduction) when fed at 20 degrees C. Bisphenol A (BPA) at 2-4 mg/L given to male or female hydra had adverse effects on both sexual and asexual reproduction. Despite the estrogenic nature of BPA, testis formation and egg formation were similarly affected. The doses causing these acute toxicities were comparable to those reported earlier in aquatic invertebrates and were much higher than environmentally detected doses, at which the disruption of the endocrine system has been reported in fishes. All these facts indicate that the adverse effects are the results of general toxicity and may not be due to the estrogenic function of the compound. On the other hand, we found that BPA at 1 mg/L (a dose still much higher than environmental doses) stimulated asexual reproduction. No such stimulation of sexual reproduction was seen. When male hydras were fed at 10 degrees C, they produced both buds and testes simultaneously. BPA at 0.5 and 1 mg/L under this condition also stimulated asexual reproduction, whereas it suppressed sexual reproduction more severely than BPA at 2-3 mg/L. There may be some interaction between processes involved in sexual and asexual reproduction under this condition, and the stimulation of asexual reproduction by BPA may cause suppression of sexual reproduction.