Differential survivorship among allozyme genotypes of Hyalella azteca exposed to cadmium, zinc or low pH.

The survival functions (SF) during acute exposures to cadmium, zinc or low pH were examined for amphipods exhibiting variation at three loci. Significant differences were observed in eight of nine locus/toxicant combinations. Two general types of survival curve patterns were identified when genotype-related SF differences were observed. In the first pattern, the survival differences between genotypes were immediately apparent with two SF curves separated at the beginning of exposure with little or no overlap. For the second pattern, both genotypes had similar SF for a period of time, during which the two survival curves crossed or overlapped. After this period, the survival probability of one genotype dropped sharply relative to the other. While SF was related to genotype, it was not related to heterozygosity. Genetic distance analysis showed that exposure to cadmium, zinc or low pH each resulted in directional selection, suggesting the potential use of genetic distance as a bioindicator.