ALLOZYME GENOTYPE AND DIFFERENTIAL RESISTANCE TO MERCURY POLLUTION IN THE CADDISFLY, NECTOPSYCHE-ALBIDA .1. SINGLE-LOCUS GENOTYPES

The caddisfly, Nectopsyche albida, was exposed to 0.6 mg mercury nitrate/L for 72 h and individual times to death recorded. All individuals were analyzed electrophoretically at six polymorphic loci. Time to death differed significantly among genotypes at the phosphoglucomutase and two alcohol dehydrogenase loci and among levels of heterozygosity. There is substantial evidence suggesting that many taxa possess allozyme genotypes exhibiting differential sensitivity to anthropogenic contaminants and natural stressors. Elimination of sensitive genotypes may reduce the ability of impacted populations to recover from additional impacts and may lessen the likelihood that they will adapt to slowly changing environmental conditions. Accordingly, we emphasize that (1) genetic standardization of bioassay organisms is necessary to assure consistency of results among testing facilities, (2) genetic monitoring may be a more sensitive method than numerical censusing to detect low levels of anthropogenic pollution, and (3) loss of genetic variation may hinder population persistence.