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

The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) protocol has recently b een adopted as a valuable tool for evaluating the embryotoxicity of environ mental contaminants in amphibians. The bioassay utilises Xenopus laevis as a test species, but there are few comparative studies to:evaluate whether d ata collected in this species is applicable to other amphibians. In this st udy, 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 LC50, EC50 and m inimum 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 LC50, EC50 and MCIG values for L. adelaidensis were 9.2, 8.8 and 5.1-6.0 mg/l, respectively. T he 134-h LC50, EC50 and MCIG values for C. insignifera were 6.4, 4.5 and 4. 0 mg/l, respectively. Teratogenicity indices for the three species ranged b etween 1.0 and 1.6, indicating either no or low teratogenicity. Growth inhi bition as assessed by embryo length was the most sensitive indicator of eff ect in all three species. X. laevis was the more sensitive of the three spe cies and the only species that displayed indisputable terata. (C) 2000 Else vier Science B.V. All rights reserved.