Embryos (stage 8-47, Nieuwkoop and Faber) of the
African clawed frog (
Xenopus laevis) were subjected to water-borne
depleted uranium (DU) concentrations that ranged from 4.8 to 77.7 mg/L using an acute 96-h frog
embryo teratogenesis assay-Xenopus (FETAX). In a chronic 64-d
assay, X. laevis (from
embryo through
metamorphosis; stages 8-66) were subjected to concentrations of DU that ranged from 6.2 to 54.3 mg/L. Our results indicate DU is a non
teratogenic metal. No effects on mortality,
malformations, or growth were observed in the 96-h FETAX with concentrations of DU that ranged from 4.8 to 77.7 mg/L. From stage 8 to stage 47, X. laevis tadpoles do not actively feed and the
gills are not well developed. Thus, uptake of DU was reduced despite exposure to elevated concentrations. The 64-d
assay resulted in no concentration response for either mortality or
malformations; however, a delay in
metamorphosis was observed in tadpoles subjected to elevated DU concentrations (from 13.1 to 54.3 mg/L) compared to tadpoles in both the well-water control and reference. The delay in
metamorphosis was likely due to increasing
body burden of DU that ranged from 0.98 to 2.82 mg/kg.
