Juveniles of the mussel Mytilus chilensis were exposed to a dietcontaining paralytic shellfish poisoning (PSP) toxins produced by the dinoflagellateAlexandrium catenella (strain ACC02). The feeding behaviour and thedynamics of intoxication and detoxification were evaluated over an intoxication period ofnine days, followed by a detoxification period of eight days. A significant reduction inthe feeding activity was measured during the first days of exposure to the PSP toxins(days 0 and 2), followed by a period of recovery observed on days 5 and 9, when theclearance rate of the contaminated mussels significantly increased. During thedetoxification period, the contaminated bivalves showed a total recovery of clearancerate, and no significant differences were observed between contaminated and controlgroups. The intoxication dynamic was characterised by a rapid and sustained increase inthe amount of PSP toxins accumulated in the tissues of the bivalves. Due to this increase,the level of PSP toxins critical for human consumption was reached on the first day, andat the end of the intoxication period, the mussels had accumulated 1601μg STX eq. 100 g-1 tissue. During the detoxification period, adecrease of PSP toxins was observed, down to 319 μg STX eq. 100g-1 tissue. The lower clearance rates observed over the first days ofexposure would produce a decrease in the energy intake and could affect the rate of growthof juveniles. Despite this initial effect, the rapid intoxication capacity of M.chilensis corroborates that this species is a good indicator for the earlydetection of harmful algal blooms.

Most recent authors have called the Chilean blue mussel (formerly Mytilus chilensis) Mytilus edulis. Mussels from four nominal species (Mytilus edulis, M. trossulus, M. galloprovincialis and M. chilensis) were collected from the eastern coast of Newfoundland, Canada, New Zealand and the southern coast of Chile. Canonical discriminant analysis of selected shell morphometrical characters showed that although there is some overlap in canonical variates, the three nominal species, M. edulis, M. trossulus and M. chilensis can be morphologically divided into three distinct groups. The two nuclear-DNA markers (ITS and Glu-5) and the mtDNA marker studied indicate that the nuclear and mitochondrial genomes of M. edulis and M. trossulus are different. M. edulis, M. galloprovincialis and M. chilensis share similar restriction fragment patterns for the mtDNA and for the ITS nuclear-DNA marker, while the Glu-5 polymerase chain reaction (PCR) assay showed that the M. edulis and M. chilensis genotypes disagree, producing species-specific banding patterns that can be used as a diagnostic marker between the two nominal species. The molecular and morphometric data reported here give more evidence to support the view of other authors that the Chilean blue mussel should be included as M. edulis subspecies: Mytilus edulis chilensis.

Heritability of larval growth rate in diferent food environments and genotype-food environment interaction (during larval growth) are estimated in Mytilus chilensis, based on a nested design, involving 24 full-sib families (8 males each mated to 3 separated females) grown under three different algal concentrations. The heritability estimates for larval shell length ranged between 0.2 ± 0.1 and 0.9 ± 0.3 and showed a decreased towards the low food treatment; but the values suggest that selection would be effective. However, since there is a significant genotype-food interaction, selection should be done in each environment in which the animals are expected to perform. The significant interaction term (p<0.001) associated with a significant genetic variability for larval growth suggest the presence of genes in the population whose expression depends upon local food conditions.