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Effects of 4‐nonylphenol and 4‐ tert ‐octylphenol on sex differentiation and vitellogenin induction in medaka ( Oryzias latipes )
Author(s) -
Seki Masanori,
Yokota Hirofumi,
Maeda Masanobu,
Tadokoro Hiroshi,
Kobayashi Kunio
Publication year - 2003
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620220712
Subject(s) - oryzias , vitellogenin , nonylphenol , feminization (sociology) , sexual differentiation , biology , andrology , alkylphenol , endocrine disruptor , fish <actinopterygii> , development of the gonads , methyltestosterone , toxicology , medicine , endocrinology , zoology , gonad , chemistry , genetics , endocrine system , fishery , social science , alkyl , organic chemistry , sociology , gene , hormone
Abstract Medaka ( Oryzias latipes ) were continuously exposed to various concentrations of two alkylphenols, 4‐nonylphenol (NP) and 4‐ tert ‐octylphenol (OP), from fertilized eggs to 60 d posthatch. The effects on sexual differentiation and hepatic vitellogenin (VTG) induction in medaka were assessed to elucidate the lowest‐observed‐effect concentrations (LOECs) of NP and OP for these events during early life stages. The LOECs of NP and OP for these events were 11.6 and 11.4 μg/L, respectively. These results suggest that NP and OP may have adverse effects at similar concentrations during early life stage in medaka. Additionally, we investigated whether the abnormal sex differentiation induced by these alkylphenols would be permanent or reversible once the medaka were returned to clean water. The appearance of the secondary sex characteristics reverted from female to male when fish were returned to clean water. However, gonadal histology showed that intersex gonads still existed, even after the fish were transferred to clean water for two months. These results suggest that the induced feminization of secondary sex characteristics in medaka exposed to alkylphenols during the stage of sexual differentiation may not always be permanent, but the gonadal alteration (testisova) may continue much longer.