title: Atrazine reduces reproduction in Japanese medaka (Oryzias latipes).
abstract: Atrazine is an effective broadleaf herbicide and the second most heavily used herbicide in the United States. Effects along the hypothalamus-pituitary-gonad axis in a number of vertebrate taxa have been demonstrated. Seasonally elevated concentrations of atrazine in surface waters may adversely affect fishes, but only a few studies have examined reproductive effects of this chemical. The present study was designed to evaluate a population endpoint (egg production) in conjunction with histological (reproductive stage, gonad pathology) and biochemical (aromatase activity, sex hormone production) phenotypes associated with atrazine exposure in Japanese medaka. Adult virgin breeding groups of one male and four females were exposed to nominal concentrations of 0, 0.5, 5.0, and 50 μg/L (0, 2.3, 23.2, 231 nM) of atrazine in a flow-through diluter for 14 or 38 days. Total egg production was lower (36-42%) in all atrazine-exposed groups as compared to the controls. The decreases in cumulative egg production of atrazine-treated fish were significant by exposure day 24. Reductions in total egg production in atrazine treatment groups were most attributable to a reduced number of eggs ovulated by females in atrazine-treated tanks. Additionally, males exposed to atrazine had a greater number of abnormal germ cells. There was no effect of atrazine on gonadosomatic index, aromatase protein, or whole body 17 β-estradiol or testosterone. Our results suggest that atrazine reduces egg production through alteration of final maturation of oocytes. The reduced egg production observed in this study was very similar to our previously reported results for fathead minnow. This study provides further information with which to evaluate atrazine's risk to fish populations.
authors.affiliation: US Geological Survey, Columbia Environmental Research Center, 4200 New Haven Rd., Columbia, MO 65251, United States. Electronic address: dpapoulias@usgs.gov.
authors.forename: Diana M
authors.initials: DM
authors.lastname: Papoulias
authors.affiliation: US Geological Survey, Columbia Environmental Research Center, 4200 New Haven Rd., Columbia, MO 65251, United States.
authors.forename: Donald E
authors.initials: DE
authors.lastname: Tillitt
authors.affiliation: Institute of Biology of Inland Waters, Russian Academy of Sciences, 152742 Borok, Nekouz, Yaroslavl, Russia.
authors.forename: Melaniya G
authors.initials: MG
authors.lastname: Talykina
authors.affiliation: US Geological Survey, Columbia Environmental Research Center, 4200 New Haven Rd., Columbia, MO 65251, United States.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Whyte
authors.affiliation: US Geological Survey, Columbia Environmental Research Center, 4200 New Haven Rd., Columbia, MO 65251, United States.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Richter
mesh_terms: D000818:Animals; D001280:Atrazine / Q000633:toxicity*; D005260:Female; D005854:Germ Cells / Q000187:drug effects; D012739:Gonadal Steroid Hormones; D008297:Male; D009990:Oryzias / Q000502:physiology*; D010058:Oviposition / Q000187:drug effects; D012098:Reproduction / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D012739:Gonadal Steroid Hormones; D014874:Water Pollutants, Chemical; D001280:Atrazine
keywords: Egg production; Genotoxicity; Herbicides