Fertilization success and sexual behavior in male medaka, Oryzias latipes, exposed to tributyltin

We evaluated the effects of tributyltin (TBT), polychlorinated biphenyls (PCBs), and a mixture of TBT and PCBs on reproduction, gonadal histology, and sexual behavior in Japanese medaka (Oryzias latipes). We administered TBT (I mug g(-1) body weight [b.w.] daily), PCBs (1 mug g(-1) b.w. daily), or both to medaka for 3 weeks. We assessed reproductive success during week 3 and the sexual behavior of male medaka after the exposure period. Fertilization success was significantly decreased in groups that received TBT. The profiles of fertility developed a bimodal distribution in the TBT and TBT + PCBs groups, and the numbers of males that performed following and dancing were significantly decreased in the TBT + PCBs group. The frequency of dancing also decreased after treatment with TBT, whereas fish that received PCBs only showed no difference in sexual behavior. Testes that had oocytes showed nor-mat spermatogenesis, even though two of the five males treated with TBT + PCBs bad some indication of testis-ova, which did not occur in any other group. Our results indicate that TBT, but not PCBs, affects sexual behavior and reproduction in medaka. (C) 2003 Elsevier Ltd. All rights reserved.