PARENT SESSION
IP06 - The Japanese Medaka Model
8:00 AM to 12:00 PM - Monday, 18 November 2002
Room Room 151 G
(IP40) Development of gonads and secondary sex characteristics in Japanese medaka exposed to endocrine disruptor substances .
Metcalfe, Chris*,1, Metcalfe, Tracy1, Kiparissis, Yiannis1,2, Balch, Gord1, 1 Trent University, Peterborough, Ontario, Canada2 Queen's University, Kingston, Ontario, Canada
ABSTRACT- In our laboratory, the Japanese medaka (Oryzias latipes) has been used as a model organinism to evaluate the effects of estrogens (e.g. estradiol, ethinylestradiol, alkylphenols, isoflavones), androgens (e.g. methyltestosterone), anti-estrogens (e.g. ZM 189,154) and anti-androgens (e.g. cyproterone acetate, vinclozolin) on the development of the gonad and secondary sex characteristics in fish. In a standard test protocol, newly hatched medaka were exposed to aqueous concentrations of test compounds for 3 months. Histological examination of the gonads indicated that sex-reversal and gonadal inter-sex occur in fish exposed to all classes of endocrine disruptor substances; with the outcome depending on the potency and the exposure concentration of the test compound. The presence of papillary processes in the anal fin indicated feminization and changes in the shape of the dorsal and anal fins indicated masculinization of secondary sex characteristics. Detection of masculinization and feminization in tests with medaka has been improved by utilizing a strain of medaka with a genotypic marker of sex.
Key words: medaka, endocrine disruptors, intersex, gonad