ALLOZYME GENOTYPE AND TIME-TO-DEATH OF MOSQUITOFISH, GAMBUSIA-HOLBROOKI, DURING ACUTE INORGANIC MERCURY EXPOSURE - A COMPARISON OF POPULATIONS

Relationships between enzyme genotype and time-to-death (TTD) during acute mercury exposure were examined in mosquitofish taken from two isolated field populations. Results were compared with those from an exposure conducted two years previously, with fish from one of these populations, in which genotypes at three enzyme loci, Icd-1, Gpi-2, and Mdh-1, were significantly related to TTD, as was overall heterozygosity. Neither genotype nor heterozygosity were related to TTD in the present exposure of fish from this population. In the exposure of fish from the population not sampled previously, two loci, Icd-2 and Mpi, were significantly related to TTD. Multiple locus heterozygosity was not related to mortality in this exposure. These two populations exhibited different genotype-TTD relationships during laboratory exposures, suggesting that the response of one population exposed in the laboratory may not accurately represent the responses of other populations, either in the laboratory or during exposures in nature.