Abstract
Developmental effects of amitraz (acaricide), its metabolite (2,4-dimethylaniline), and paraquat (herbicide) on embryos of a nontarget organism, Xenopus laevis, were investigated. Following the standard protocol of the American Society for Testing and Materials (ASTM), the experiments were carried out using native Xenopus frogs. There was a drastic increase in mortality from 24 h to 96 h for paraquat, but 2,4-dimethylaniline showed no mortality at the highest concentration tested (100 mg/L). The 96-h LC50 values were 0.67, 3.27, and ≫100 mg/L for paraquat, amitraz, and 2,4-dimethylaniline, respectively. At concentrations higher than 0.2 mg/L of paraquat all the embryos were malformed, whereas growth reduction was apparent at all test concentrations (0.1–5 mg/L). The most common teratogenic effects were flexures of the notochord and stunting of growth. Edema was the most common effect of amitraz on the embryos, and 100% of the surviving embryos in 5 mg/L were edematous. The 96-h EC50 (malformation) values were 1.21 (95% CI 0.48–3.03) and 0.18 (95% CI 0.16–0.20) mg/L for amitraz and paraquat, respectively. The ratio of 96-h LC50 to 96-h EC50 (malformation), i.e., the teratogenicity index (TI) were 2.7 and 3.72 for amitraz and paraquat, respectively, and for 2,4-dimethylaniline (TI > 5) all the embryos in 25 mg/L showed observable pigment loss and encephalomegaly. This shows that paraquat and the degradation product of amitraz, 2,4-dimethylaniline, should be classified as teratogens. Teratogenic risks of massive application of these pesticides on Kenyan farms should therefore be considered.
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Received: 27 June 2001/Accepted: 4 February 2002
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Osano, O., Oladimeji, A., Kraak, M. et al. Teratogenic Effects of Amitraz, 2,4-Dimethylaniline, and Paraquat on Developing Frog (Xenopus) Embryos. Arch. Environ. Contam. Toxicol. 43, 42–49 (2002). https://doi.org/10.1007/s00244-002-1132-4
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DOI: https://doi.org/10.1007/s00244-002-1132-4