MALFORMATIONS PERSIST AFTER METAMORPHOSIS OF XENOPUS-LAEVIS TADPOLES EXPOSED TO NI2+, CO2+, OR CD2+ IN FETAX ASSAYS

This study was performed to determine whether malformations induced in Xenopus laevis embryos by exposures to divalent nickel, cobalt, or ca dmium chlorides in FETAX assays persist after the tadpoles undergo met amorphosis to juvenile frogs. Embryos were exposed for four days to EC (50) concentrations of Ni2+, Co2+, or Cd2+ under the standard conditio ns of FETAX assays; thereafter, the exposures were discontinued and th e tadpoles were kept in aquaria through metamorphosis. Controls were t reated similarly, without exposure to metals. At 13 weeks of age, surv iving frogs were killed and examined for malformations. Control and me tal-exposed groups of Xenopus did not differ significantly in their me dian ages at metamorphosis, mean body weights, or survival at 13 weeks . Overall incidences of malformations found in Ni2+-, Co2+-, or Cd2+-e xposed frogs at 13 weeks of age were 55, 40, and 51%, respectively (P < 0.01 vs. 3% in controls). The malformations of metal-exposed frogs i ncluded retinal depigmentation, diastematomyelia, scoliosis, kyphosis, phocomelia, sacro-pelvic and hind-limb deformities, and dysplasias of the heart, kidney, ovary and gut. (C) 1994 Wiley-Liss, Inc.