Effects of copper on the fitness of the Chilean scallop Argopecten purpuratus (Mollusca : Bivalvia)

Exposure to high concentrations of metals can affect populations and indivi duals at morphological, physiological, biochemical or genetic levels. Metal pollution is a source of environmental stress that can have deleterious ef fects on organisms and generate selective pressure upon populations. This w ork attempts to establish whether concentrations of copper, above physiolog ical requirements, can affect the genetic structure of a cohort of Chilean scallop Argopecten purpuratus. Following the determination of LC50 for 96 h experiments, other acute toxicity tests were carried out, exposing the juv eniles to solutions of 150 ppb copper for 120 h. Dead, surviving and contro l individuals from these bioassays were genetically characterized for five polymorphic loci, Isocitrate dehydrogenase (Idh), Octopine dehydrogenase (O cdh), Phosphogluconate dehydrogenase (Pgd), Leucine aminopeptidase (Lap) an d Phosphoglucose isomerase (Pgi). Results showed no significant differences in allele and genotypic frequencies between surviving and dead individuals , although for the same groups significant differences were found in estima ted mean heterozygosity. Pgi and Ocdh showed significantly different hetero zygosity values for dead and surviving individuals. A positive relationship between multilocus heterozygosity and survival was found for young A. purp uratus exposed to high copper concentrations; thus, we found evidence of a differential response to exposure to high copper concentrations, related to degree of heterozygosity.