Molecular and genetic ecotoxicologic approaches to aquatic environmental bioreporting

Molecular and population genetic ecotoxicologic approaches are being develo ped for the utilization of arthropods as bioreporters of heavy metal mixtur es in the environment. The explosion of knowledge in molecular biology, mol ecular genetics, and biotechnology provides an unparalleled opportunity to use arthropods as bioreporter organisms. interspecific differences in aquat ic arthropod populations have been previously demonstrated in response to h eavy metal insult in the Arkansas River (AR) California Gulch Superfund sit e (CGSS). Population genetic analyses were conducted on the mayfly Baetis t ricaudatus. Genetic polymorphisms were detected in polymerase chain reactio n amplified 16S mitochondrial rDNA ia selectively neutral gene) of B. trica udatus using single-strand conformation polymorphism analysis. Genetic diff erences may have resulted from impediments to gene flow in the population c aused by mortality arising from exposure to heavy metal mixture pollution. In laboratory studies a candidate metal-responsive mucinlike gene, which is metal and dose specific, has been identified in Chironomus tentans and oth er potential AR-CGSS bioreporter species. Population genetic analyses using the mucinlike gene may provide insight into the role of this selectable ge ne in determining the breeding structure oi B. tricaudatus in the AR-CGSS a nd may provide mechanistic insight into determinants of aquatic arthropod r esponse to heavy metal insult. Metal-responsive (MRI genes and regulatory s equences are being isolated, characterized, and assayed for differential ge ne expression in response to heavy metal mixture pollution in the AR-CGSS. Identified promoter sequences can then be engineered into previously develo ped MR constructs to provide sensitive in vitro assays for environmental bi oreporting of heavy metal mixtures. The results of the population genetic s tudies are being entered into an AR geographic information system that cont ains substantial biological, chemical, and geophysical information. Integra ted spatial, structural, and temporal analyses of these parameters will pro vide invaluable information concerning environmental determinants that rest rict or promote gene flow in bioreporter populations.