Application of the FETAX protocol to assess the developmental toxicity of nonylphenol ethoxylate to Xenopus laevis and two Australian frogs

Abstract

The Frog Embryo Teratogenesis Assay– Xenopus (FETAX) protocol has recently been adopted as a valuable tool for evaluating the embryotoxicity of environmental contaminants in amphibians. The bioassay utilises Xenopus laevis as a test species, but there are few comparative studies to evaluate whether data collected in this species is applicable to other amphibians. In this study, the embryotoxicity of the nonionic surfactant, nonylphenol ethoxylate, was determined in X. laevis and the Australian frogs, Litoria adelaidensis and Crinia insignifera using the FETAX protocol. The 96-h LC 50, EC 50 and minimum concentration to inhibit growth (MCIG) values for X. laevis were 3.9–5.4, 2.8–4.6 and 1.0–3.0 mg/l, respectively. The 140-h LC 50, EC 50 and MCIG values for L. adelaidensis were 9.2, 8.8 and 5.1–6.0 mg/l, respectively. The 134-h LC 50, EC 50 and MCIG values for C. insignifera were 6.4, 4.5 and 4.0 mg/l, respectively. Teratogenicity indices for the three species ranged between 1.0 and 1.6, indicating either no or low teratogenicity. Growth inhibition as assessed by embryo length was the most sensitive indicator of effect in all three species. X. laevis was the more sensitive of the three species and the only species that displayed indisputable terata.