Aspects of the digestive gland cells of the mussel Mytilus galloprovincialis, in relation to lysosomal enzymes, lipofuscin presence and shell size: contribution in the assessment of marine pollution biomarkers

The present study investigates the histochemical localization of N-acetyl-β-hexozaminidase (Hex), acid phosphatase (AcP) and β-glucuronidase (β-Gus) in the digestive gland of mussels Mytilus galloprovincialis, as well as the clarification of suitable enzyme for biomarkers' application dealing with lysosomes. The results show more intense and homogenous localization of Hex, in relation to AcP and β-Gus and, thus, Hex histochemistry is supported as more suitable procedure for the evaluation of "lysosomal membrane stability" and "morphometrical alterations of lysosomes". The affection of lipofuscin granules on lysosomal enzymes' activity is also discussed. Additionally, the present study examines the response of small- and large-sized mussels M. galloprovincialis by assessing the "lysosomal membrane stability", "morphometrical alterations of lysosomes", "lysosomal response index (LRI)" and "structural epithelial changes in digestive tubules". The results indicate appreciable alterations of the above parameters in large-sized mussels, supporting their greater influence by the environmental factors, in relation to small-sized ones.