Effects of water quality on development of Xenopus laevis: A frog embryo teratogenesis assay—Xenopus assessment of surface water associated with malformations in native anurans

Abstract

AbstractThe purpose of this work was to determine if surface water from a site in Minnesota, USA, with malformed anurans was able to elicit adverse developmental effects in the frog embryo teratogenesis assay: Xenopus (FETAX) and to isolate and identify the factors responsible for the effects. In the standard FETAX test, 25 organisms are placed in a 10‐ml volume of solution that is renewed daily. The organisms are assessed for abnormal development and the test is terminated at 96 h. Under these conditions, the site water adversely affected craniofacial development, gastrointestinal development, and growth. However, these effects were eliminated by each of several different treatments, including diluting the surface‐water sample with the standard testing solution, adding dry salts directly to the surface water, testing the organisms in larger volumes of site water, and evaporating site water to increase the concentration of total dissolved solids. These results are consistent with the hypothesis that the low ion concentrations found in this particular site water were responsible for the developmental effects observed in FETAX. This hypothesis was strengthened further when a reconstituted water, made with deionized water and reagent‐grade salts to mimic the content of the site water, affected survival, growth, and development similarly to the surface water. In addition, substantial ammonia accumulation in the FETAX tests was documented. These data suggest that the inherent variability in water quality of field‐collected samples is important and could result in artifactual developmental effects when using FETAX. As such, the developmental toxicity observed in these FETAX studies is probably not relevant to malformations observed in native anuran species. To obviate this type of problem, the volumes used in the FETAX protocol should be increased for better organism performance and to reduce the possibility of ammonia toxicity.