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.

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.

Sets of adult male and female Xenopus laevis were administered a boron-deficient (-B) diet under low-boron culture conditions, a boron-supplemented (+B) diet under ambient boron culture conditions, a copper-deficient (-Cu) diet under low-copper culture conditions, or a copper-supplemented (+Cu) diet under ambient copper culture conditions, for 120 d. Adults from each group were' subsequently bred, and the progeny were cultured and bred. Results from these studies indicated that although pronounced effects on adult reproduction and early embryo-larval development were noted in the -B F1 generation, no effects on limb development were observed. No significant effects on reproduction, early embryogenesis, or limb development were noted in the +B group, irrespective of generation. Highly specific forelimb and hindlimb defects, including axial flexures resulting in crossed limbs and reduction deficits, were observed in -B F2 larvae, but not in the +B F2 larvae. As was noted in the boron-deficiency studies, significant effects on reproduction and early embryo development were observed in the -Cu F1 generation, but not in the +Cu F, generation. Unlike the effects associated with boron deficiency, maldevelopment of the hindlimbs (32 responders, n = 40) was found in the F1 generation.

Abstract-Analytically impure (ϳ85-88%) and purified (99.5%) preparations of two sulfonylurea herbicides, sulfometuron methyl and nicosulfuron, were evaluated for short-and long-term developmental effects on organogenesis (0-4 d) and limb development (0-30 d), and impact on metamorphosis (tail resorption [50-64 d]). Overall, the analytically impure sulfonylurea herbicides were more developmentally toxic than the purified preparations. Purified preparations did not induce early embryo-larval developmental effects or effects on hind limb development, although the rate of tail resorption was slowed at relatively high concentrations. Tail resorption rates were slowed significantly and abnormal limb development was induced by the analytically impure sulfonylurea herbicides. The process of organogenesis as monitored by the traditional frog embryo teratogenesis assay-Xenopus (FETAX) test was the least sensitive stage of development monitored in this study. Although some maldevelopment was induced at the limit of aqueous solubility of the analytically impure material, the severity of the malformations with the impure preparations was moderate. Based on this study, the analytically impure herbicides were more developmentally toxic than purified preparations of the same herbicides, which exerted little effect at maximum soluble concentrations. Thus, the capacity of purified nicosulfuron and sulfometuron methyl to interfere with amphibian development and maturation seems to be relatively low.

Analytically impure (∼85–88%) and purified (99.5%) preparations of two sulfonylurea herbicides, sulfometuron methyl and nicosulfuron, were evaluated for short‐ and long‐term developmental effects on organogenesis (0–4 d) and limb development (0–30 d), and impact on metamorphosis (tail resorption [50–64 d]). Overall, the analytically impure sulfonylurea herbicides were more developmentally toxic than the purified preparations. Purified preparations did not induce early embryo–larval developmental effects or effects on hind limb development, although the rate of tail resorption was slowed at relatively high concentrations. Tail resorption rates were slowed significantly and abnormal limb development was induced by the analytically impure sulfonylurea herbicides. The process of organogenesis as monitored by the traditional frog embryo teratogenesis assay—Xenopus (FETAX) test was the least sensitive stage of development monitored in this study. Although some maldevelopment was induced at the limit of aqueous solubility of the analytically impure material, the severity of the malformations with the impure preparations was moderate. Based on this study, the analytically impure herbicides were more developmentally toxic than purified preparations of the same herbicides, which exerted little effect at maximum soluble concentrations. Thus, the capacity of purified nicosulfuron and sulfometuron methyl to interfere with amphibian development and maturation seems to be relatively low.