Genetic heterozygosity and growth rate in a cohort of Mytilus edulis from the Irish coast

Abstract

Mussels from a natural population of Mytilus edulis, which had settled onto ropes, were collected from Killary Harbour on the west coast of Ireland in November 1986 when they were approximately 5 mo old. Shell lengths in the cohort ranged between 13 and 33 mm and did not differ significantly from a normal distribution. Heterozygosity at five polymorphic loci (Gpi, Pgm, Lap, Odh, and Est-D) was determined for each measured individual. Highly heterozygous individuals did not achieve higher and more uniform growth rates than homozygous individuals of the same cohort. When the results for each locus were considered individually, there was a significant positive correlation between heterozygosity and growth rate for the Odh locus. Significant departures from Hardy-Weinberg expectations were observed at the Pgm, Lap and Odh loci, and the magnititude of the deficiency was marginally larger among smaller, slower growing mussels of the cohort. Overall, these results contrast with those observed by other investigators for a single cohort of M. edulis sampled from Long Island Sound (USA).