Morphological Changes in Xenopus laevis Embryos with Lithium and Evaluation of the Fetax Test

The main goal was to standardize the FETAX (Frog Embryos Teratogenesis Assay: Xenopus) test. Since lithium ions are known to be teratogenic for embryos of many organisms, they were prefferred for our first standardization assay. Xenopus laevis embryos were exposed to lithium chloride (from 2x10–4 to 6 x 10–3 M concentrations) for 96 hours at 2–4 cell stages of development. Exposure to lower LiCl concentrations permitted larvae to survive and to develop into normal ones. On the other hand, depending on the increase in the LiCl concentration, the body length and survival rate (%) decreased. In addition, the decreased survival and increased malformation rates were shown to be parallel with the increased concentration rates. The most common abnormalities were found to be tail kinks and edema. The less frequents abnormalities were microcephaly, cyclopia, shortening of the trunk (micromyelia), depigmentation, macrocephaly, spina bifida, anteriozation, posteriozation, medially located eyes and abnormally of the yolk. In the Fetax test, at ninety–six hours, LC50 value was 0.002 g/L, and EC50 value was 0.0088g/L for lithium chloride. Finally, the teratogenicity index was found to be about 2.5. These results showed that lithium chloride was a moderate teratogen.