Comparative developmental toxicity of nickel to Gastrophryne carolinensis, Bufo terrestris, and Xenopus laevis

The early embryo-larval developmental toxicity of nickel (Ni) to 3 amphibian species, Xenopus laevis (South African clawed frog), Bufo terrestris (southern toad), and Gastrophryne carolinensis (eastern narrow-mouthed toad), was evaluated using a modified FETAX model. Studies were initiated from late blastulae stage (Nieuwkoop and Faber [NF] stage 10 or Gosner stage 12) and completed at a common embryological-based test termination point, which represented the completion of the major stages of organogenesis (NF stage 46 for Xenopus or Gosner stage 26 for the toads). Results indicated that, in terms of lethality, G. carolinensis was the most sensitive and X. laevis was the least sensitive of the species tested. The 4-d LC50 in X. laevis value was approximately 7.2- and 2.8-fold greater than the G. carolinensis and B. terrestris, respectively. In terms of malformation, X. laevis was the most sensitive and B. terrestris was the least sensitive of the species tested. The 7-d EC50 (malformation) in B. terrestris was 10.6- and 7.0-fold greater than X. laevis or G. carolinensis, respectively. The chronic value (ChV) for growth in X. laevis was nearly 4.5-fold less than the ChV for growth determined for B. terrestris. As with the malformation endpoint, X. laevis was more sensitive than the other species, which were nearly equisensitive. Overall, the present study provides new data regarding the toxicity of Ni to larval amphibian species, which may be useful in the establishment of new aquatic life criteria for Ni.