title: Toxicity of Guthion and Guthion 2S to Xenopus laevis embryos.
abstract: The development of Xenopus laevis (African clawed frog) embryos exposed to the pesticide Guthion (technical grade) and Guthion 2S (commercial formulation) was evaluated in modified Frog Embryo Teratogenesis Assay--Xenopus (FETAX) tests. The embryos were exposed to five or six increasing concentrations of pesticide in 10- and 100-ml exposure volumes of test solution for 96 h. Embryos exposed in 10-ml volumes of Guthion exhibited increased mortality, increased deformation, and decreased size as compared to those exposed in 100-ml volumes. LC50s for embryos exposed in the 10-ml Guthion tests ranged from 6.1 to 6.3 mg/L as compared to 10.6 to 11.9 mg/L for those in the 100-ml tests. The percentage of deformities at 3 mg/L Guthion in test survivors in 10-ml tests ranged from 73 to 89%, while in the 100-ml tests less than 2% were deformed at the same concentration. Mean control embryo lengths at test completion were 8.2 and 10.6 mm, respectively, for 10- and 100-ml tests. The LC50 for embryos in 100 ml Guthion 2S was 1.6 mg/L active ingredient, indicating a much greater toxicity of the commercial formulation. NOAEL (No Observed Adverse Effect Level) values for Guthion and Guthion 2S ranged from 0.48 to 7.96 mg/L, depending upon basis (length, deformity, mortality) and pesticide formulation, and were many times greater than the existing water quality criterion of 0.01 microgram/L.
authors.affiliation: U.S. Environmental Protection Agency, Corvallis Environmental Research Laboratory, Oregon 97333.
authors.forename: G S
authors.initials: GS
authors.lastname: Schuytema
authors.forename: A V
authors.initials: AV
authors.lastname: Nebeker
authors.forename: W L
authors.initials: WL
authors.lastname: Griffis
mesh_terms: D000014:Abnormalities, Drug-Induced / Q000662:veterinary*; D000818:Animals; D000835:Animals, Wild / Q000002:abnormalities*; D001387:Azinphosmethyl / Q000633:toxicity*; D001681:Biological Assay; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D047108:Embryonic Development; D007928:Lethal Dose 50; D014982:Xenopus laevis
chemical_list: D001387:Azinphosmethyl