Over a one year period, seasonal variations in aspects of Mytilus edulis L. immune function, namely, total and differential blood cell counts, phagocytic capability and intracellular superoxide generation, were investigated. These immune parameters were found to be significantly affected by seasonal variations with special reference to M. edulis reproductive cycle.
A concomitant population genetics study, using electrophoresis at 9 allozyme loci, was carried out on the monthly samples of M. edulis used for the immunocompetence assays. Significant temporal genetic variations were observed.
When comparing the level of heterozygosity at the 9 allozyme loci surveyed, which was chosen as the genetic index, with the aspects of immunity studied, one association could be demonstrated between heterozygosity and the character of circulating haemocytes.
The effects of short-term (14 day) and long-term (40 day) in vivo exposures to the reference toxicant sodium pentachlorophenol (NaPCP), on aspects of M. edulis immune function (using the same immune parameters as for the seasonal variations study) were also investigated. Results showed that NaPCP had a toxic effect on the immune responses surveyed.
However, the seasonal results show that immune response may differ according to the time of year and therefore changes in immune response as a result of contaminant exposure could also vary with season.