title: Response of larval Xenopus laevis to atrazine: assessment of growth, metamorphosis, and gonadal and laryngeal morphology.
abstract: Larval Xenopus laevis were exposed to one of four concentrations of atrazine (0, 1, 10, or 25 microg/L, 11 replicate tanks per treatment, 60-65 larvae per replicate) dissolved in an artificial pond water (frog embryo teratogenesis assay- Xenopus [FETAX]) medium beginning 48 h after hatching until the completion of metamorphosis. Separate groups of larvae (six replicate tanks per treatment, 60-65 larvae per replicate) were exposed to estradiol (100 microg/L), dihydrotestosterone (100 microg/L), or ethanol vehicle control dissolved in FETAX medium. None of the treatments affected posthatch mortality, larval growth, or metamorphosis. There were no treatment effects on sex ratios except for estradiol, which produced a greater percentage of female offspring. Exposure to either estradiol or 25 microg atrazine/L increased the incidence of intersex animals based on assessment of gonadal morphology. Atrazine did not reduce the size of the laryngeal dilator muscle, a sexually dimorphic muscle in this species. We conclude that environmentally relevant concentrations of atrazine do not influence metamorphosis or sex ratios and do not inhibit sexually dimorphic larynx growth in X. laevis. The incidence of atrazine-induced intersex animals was small (<5%) and occurred only at the greatest concentration of atrazine tested, a concentration that is rarely observed in surface waters in the United States.
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, Texas 79409, USA. james.carr@ttu.edu
authors.forename: James A
authors.initials: JA
authors.lastname: Carr
authors.forename: Angie
authors.initials: A
authors.lastname: Gentles
authors.forename: Ernest E
authors.initials: EE
authors.lastname: Smith
authors.forename: Wanda L
authors.initials: WL
authors.lastname: Goleman
authors.forename: Lina J
authors.initials: LJ
authors.lastname: Urquidi
authors.forename: Kerry
authors.initials: K
authors.lastname: Thuett
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Kendall
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
authors.forename: Tim S
authors.initials: TS
authors.lastname: Gross
authors.forename: Keith R
authors.initials: KR
authors.lastname: Solomon
authors.forename: Glen
authors.initials: G
authors.lastname: Van Der Kraak
mesh_terms: D000818:Animals; D001280:Atrazine / Q000633:toxicity*; D013196:Dihydrotestosterone / Q000633:toxicity; D012734:Disorders of Sex Development / Q000139:chemically induced; D004958:Estradiol / Q000633:toxicity; D005260:Female; D006066:Gonads / Q000187:drug effects / Q000254:growth & development*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D007830:Larynx / Q000187:drug effects / Q000254:growth & development*; D008297:Male; D008675:Metamorphosis, Biological / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects; D012744:Sex Ratio; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D014982:Xenopus laevis
chemical_list: D014874:Water Pollutants, Chemical; D013196:Dihydrotestosterone; D004958:Estradiol; D001280:Atrazine