ABSTRACT
In previously conducted laboratory studies with the South African clawed frog (Xenopus laevis), pond water and sediment samples collected from various sites in Minnesota, USA, were demonstrated to have the potential to induce a variety of developmental abnormalities, including early embryo-larval maldevelopment, abnormal limb development, and disruption of metamorphosis. The results of exposure of X. laevis to suspect pond water and sediment samples supported the hypothesis that these samples were capable of inducing these abnormalities as the result of either the presence of developmental toxicants or the absence of essential micronutrients. Physicochemical characterization of the causes of abnormal frog embryo-larval and limb development were performed using the frog embryo teratogenesis assay-Xenopus (FETAX). Specific compounds were subsequently identified within the complex mixture fractions and tested by dilution in a control solution and native reference water using both the 4- and 30-d treatment protocols. Results from these studies suggested that a complex mixture of both naturally occurring and man-made compounds was primarily responsible for the effects observed in X. laevis. The potency of several compounds was also enhanced by the site water, thus indicating that the water matrix deserves consideration as a contributing factor for both laboratory and field studies.
