title: The effects of methyltestosterone on the sexual development and reproduction of adult medaka (Oryzias latipes).
abstract: We examined the effects of methyltestosterone (MT) on the reproduction of medaka (Oryzias latipes). Six mating pairs of medaka were exposed for 3 weeks to MT at the measured concentrations of 22.5, 46.8, 88.1, 188, and 380 ng/L. The fecundity and fertility of paired medaka were significantly decreased in the 46.8, 88.1, 188, and 380 ng/L MT groups compared with those of controls. The gonadosomatic indices of female fish exposed to >or=46.8 ng/L were increased significantly. Gonadal histology showed degeneration of oocytes in the ovaries of fish in all MT treatment groups. Hepatic vitellogenin concentrations were significantly decreased in female fish treated with MT at 188 and 380 ng/L, and the hatchability and survival rate of the offspring were decreased in all MT treatment groups. These results clearly demonstrate that MT at >or=46.8 ng/L inhibited gonadal development and adversely affected the reproduction of medaka.
authors.affiliation: Division of Bioresource and Bioenvironmental Sciences, Kyushu University Graduate School, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Ik Joon
authors.initials: IJ
authors.lastname: Kang
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yokota
authors.forename: Yuji
authors.initials: Y
authors.lastname: Oshima
authors.forename: Yukinari
authors.initials: Y
authors.lastname: Tsuruda
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shimasaki
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Honjo
mesh_terms: D000818:Animals; D005260:Female; D006066:Gonads / Q000187:drug effects* / Q000502:physiology; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008777:Methyltestosterone / Q000633:toxicity*; D009990:Oryzias; D012098:Reproduction / Q000187:drug effects* / Q000502:physiology; D046468:Sexual Development / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors; D014819:Vitellogenins / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014819:Vitellogenins; D014874:Water Pollutants, Chemical; D008777:Methyltestosterone