title: Feminization of Japanese medaka (Oryzias latipes) exposed to 17beta-estradiol: effect of exposure period on spawning performance in sex-transformed females.
abstract: Two groups of Japanese medaka (Oryzias latipes) were exposed to 17beta-estradiol (E2: 150ng/L, nominal concentration) for either a short-term exposure (STE: 0-31 days after fertilization (daf); egg-larval period) or a long-term exposure period (LTE: 0-81 daf; egg-adult period) and their subsequent spawning performance was compared in terms of fecundity, spawning time, and fertility. Most genetic males were transformed to phenotypic females by E2 following both short-term and long-term exposure, but spawning performance and gonad somatic index (GSI) of sex-transformed females (XY females) following long-term exposure were lower than those of sex-transformed females following short-term exposure and those of normal females (XX) in the control group. Sex-transformed females in the STE group and normal females possessed mature ovary, whereas most of the sex-transformed females in the LTE group possessed immature ovary, with most oocytes being in the pre-vitellogenic phase. Moreover, the chromosome types of first filial generation delivered from sex-transformed female in STE group composed with 51.9% as XY, 18.5% as YY, and 29.6% as XX. From these results, it seems that exposure to E2 until the end of the larval period produces sex-transformed medaka with high reproductive ability, similar to normal females, but longer exposure to E2 may inhibit sexual maturation in the sex-transformed female.
authors.affiliation: National Institute for Environmental Studies, Onogawa 16-2, Tsukuba 305-8506, Japan. hirai.narisato@nies.go.jp
authors.forename: Narisato
authors.initials: N
authors.lastname: Hirai
authors.forename: Ayumi
authors.initials: A
authors.lastname: Nanba
authors.forename: Masaaki
authors.initials: M
authors.lastname: Koshio
authors.forename: Takuya
authors.initials: T
authors.lastname: Kondo
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Morita
authors.forename: Norihisa
authors.initials: N
authors.lastname: Tatarazako
mesh_terms: D000818:Animals; D004958:Estradiol / Q000032:analysis / Q000633:toxicity*; D005260:Female; D005262:Feminization / Q000139:chemically induced / Q000662:veterinary*; D005393:Fish Diseases / Q000139:chemically induced*; D007814:Larva / Q000187:drug effects; D008297:Male; D009865:Oocytes / Q000187:drug effects; D009990:Oryzias / Q000502:physiology*; D010053:Ovary / Q000187:drug effects; D012098:Reproduction / Q000187:drug effects*; D012730:Sex Chromosomes / Q000235:genetics; D013223:Statistics as Topic; D013997:Time Factors; D014819:Vitellogenins / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D014819:Vitellogenins; D014874:Water Pollutants, Chemical; D004958:Estradiol