ALLOZYME GENETICS OF MYTILUS-EDULIS SUBJECTED TO COPPER AND NUTRITIVESTRESS

Mytilus edulis (Mollusca: Bivalvia) collected as spat from the wild in 1990 and held in the laboratory for 18 months were divided into four groups: fed (control); starved; fed with 100 ppb added copper; and sta rved with 100 ppb added copper. Following >60% mortalities in the star ved and copper stressed groups (but negligible mortalities in the cont rol) surviving mussels from all four groups were genotyped at seven al lozyme loci (Gpi, Lap, Pgm, Idh, Odh, Gsr and Est). Allele frequencies did not vary significantly between any of the four groups at any loci , except Gsr where fed and starved groups differed. Mortalities were n ot genotype dependent at the Pgm locus but, in contrast, genotype freq uencies at most other loci varied significantly between groups. At the Gpi, Lap, Gsr and Odh loci there were significant changes in proporti ons of heterozygotes following copper induced mortalities such that, i n general, heterozygotes survived longer and homozygotes succumbed soo ner. No similar pattern was evident in relation to mortalities caused by starvation; at only one locus (Idh) was there evidence of a signifi cant effect but this was not apparently independent of the effect of c opper.