Effects of pond water, sediment, and sediment extracts from minnesota and vermont, USA, on early development and metamorphosis of xenopus.

In recent studies, a high incidence of amphibian mortality and malformation has been reported in the field, suggesting that toxic and/or bioactive agents are present in the environment of the affected amphibians. This study provides evidence for this hypothesis, because it applies to several affected ponds in Minnesota and Vermont, USA. Three developmental bioassays were carried out on samples from three reference and three test sites in Minnesota and one reference and three test sites, in Vermont. The bioassays utilized Xenopus as a model system, measuring altered developmental patterns during the first 4 d of development (frog embryo teratogenesis assay-Xenopus [FETAX]), hind-limb development over a 30-d period, and tail length resorption over a 14-d period. Strong correlations were observed among the results for all three in vitro bioassays, as well as between adverse developmental effects in vitro and in the field.

PROGRESS TOWARD IDENTIFYING CAUSES OF MALDEVELOPMENT INDUCED IN XENOPUS BY POND WATER AND SEDIMENT EXTRACTS FROM MINNESOTA, USA.

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.