Differential survivorship of allozyme genotypes in mosquitofish populations exposed to copper or cadmium

Abstract

Laboratory stocks of mosquitofish (Gambusia affinis) were acutely exposed to copper (0.16–0.24 mg/L) or cadmium (6.7–9.5 mg/L) for 48 h using a static renewal system. Allozyme genotypes at three polymorphic loci: phosphoglucomutase‒2 (PGM‒2), glucose phosphate isomerase‒2 (GPI‒2), and isocitrate dehydrogenase‒2 (ICD‒2) were resolved using a modified starch gel (13%) electrophoretic technique. Differential survivorship of allozyme genotypes was analyzed using a Wilcoxon matched pair signed‒rank test. Copper significantly (p < 0.05) decreased the overall survivorship of fish heterozygous at the GPI‒2 locus. The frequency of the (ab) genotype was significantly higher in the dead fraction of the test populations than in the surviving fraction. The frequencies of the (aa) genotype and the (a) allele at the ICD‒2 locus were significantly higher in female fish surviving exposure to copper than in nonsurviving females. The frequencies of the (bb) genotype and the (b) allele at the GPI‒2 locus were significantly higher in fish surviving exposure to cadmium than in nonsurvivors. These results indicate that some electrophoretically detectable allozymes are more sensitive than others to the toxic effects of environmental pollutants. This suggests that the genetic structure of natural populations should be considered for use as a biological monitor of environmental pollution. Copyright © 1989 SETAC