SURVIVAL OF COPPER-EXPOSED JUVENILE FATHEAD MINNOWS (PIMEPHALES PROMELAS) DIFFERS AMONG ALLOZYME GENOTYPES

摘要

The effects of seven variable enzyme loci and multiple-locus heterozygosity on time to death (TTD) during an acute 96-h copper exposure were examined by two failure-time regression models. Allozymes for five enzyme loci (GPI-1~*, GPI-2~*, IDHP-1~*, MDH-2~*, and PGM~*) were significantly related to TTD. Heterozygosity was not significantly related to TTD. Fish weight was found to have a negative relationship with TTD, larger fish having shorter TTD. This unusual relationship may have resulted from differential survivorship of individuals with sensitive and resistant alleles at the MDH-2~* and the IDHP-1~* loci. For the IDHP-1~* locus the allele ~*a was associated with increased copper survivorship; however, it was also associated with small size. Conversely, the allele ~*a at the MDH-2~* locus, which was present in higher frequency in larger fish, was associated with decreased survivorship. These results indkate that genetic selection for one characteristic may have a negative impact on other characteristics. Survivors of the copper exposure were genetically selected for copper resistance, resulting in the significant reduction in frequencies of several sensitive genotypes in the population. We conclude that monitoring population genetic structure and frequency changes of sensitive genotypes is a useful biomarker.