Toxic Effects of Fungicide Tebuconazole on the Early Development of African Clawed Frog, Xenopus laevis

Abstract

We investigated the toxic effects of tebuconazole on development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of tebuconazole(0-100 μM). LC100 for tebuconazole was 100 μM, and the LC50 determined by probit analysis was 82.35 μM. The exposure to tebuconazole concentrations ≥40 μM resulted in 11 different types of severe external malformations including gut dysplasia. Histological examinations revealed various dysplasia in the eye, heart, liver, intestine, somatic muscle, and in the pronephric ducts. The tissue-specific toxic effects were investigated with an animal cap assay. Blood cells are generally induced at a high frequency by the combination of mSCF and activin A, however, the induction of blood cells was strongly inhibited by the addition of tebuconazole. Electron micrographs of tested embryos showed many of multivesicular bodies and dysplasia of photo-receptive cell, however, the somatic muscle degeneration was not severe. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction and revealed that expression of the blood-specific marker, β globin Ⅱ and muscle-specific marker, muscle actin were more strongly inhibited than the neural-specific marker, XEn2.