Measurements of histological changes in fish larvae, blue mussels and caged fish

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The ICES biological effects monitoring in pelagic ecosystems (BECPELAG) workshop is a multi-national, multi-disciplinary workshop aimed at establishing suitable techniques for monitoring the effects of contaminants on pelagic ecosystems. Fish larvae, blue mussels (Mytilus edulis) and cod (Gadus morhua) were evaluated for the presence of histological changes indicative of contaminant exposure. Fixed and sectioned specimens were examined for the presence of infectious diseases and for parasites, in addition to any morphological and toxicopathic tissue changes. Caged cod specimens displayed a number of pathologies with putative toxicopathic aetiology. Most significantly, changes in the histological appearance of the gonads of both male and female fish indicated a potential effect of contaminants on the caged cod. In this case, use of the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) assay allowed for the detection of apoptotic degeneration of spermatogonial and oogonial germ cells. Caged mussels displayed an array of pathologies indicative of contaminant exposure. Mussels deployed in close proximity to oil platforms displayed a higher prevalence of lysosomal abnormality in the epithelial cells of their digestive glands than did those deployed at reference locations. Furthermore, mussels from these sites appeared to show a higher prevalence of oocytic atresia than reference animals. Significantly, a number of mussels surveyed during the current study showed neoplastic changes associated with their connective tissues (disseminated neoplasia) and in one case, the testicular follicles (germinoma). The significance of these pathological findings in cod and mussels are discussed in relation to their use as environmental sentinels for future biological effects monitoring studies, particularly in relation to contaminant exposure in the proximity of oil platforms.