LIGHT AND ELECTRON-MICROSCOPIC LOCALIZATION OF LYSOSOMAL ACID-HYDROLASES IN BIVALVE HEMOCYTES BY ENZYME CYTOCHEMISTRY

In the present work the haemocytes of mussels Mytilus galloprovinciali s (Mollusca, Bivalvia) have been studied by enzyme cytochemistry in or der to investigate the light and electron microscopical distribution o f two lysosomal marker enzymes, acid phosphatase (AcPase) and arylsulp hatase (ASase). Both hyalinocytes and granulocytes show positive react ion products for the two enzymes but granulocytes are far more reactiv e. Int he hyalinocytes, AcPase and ASase activities are observed in a few pleomorphic lysosomes. In the granulocytes, the reaction product f or the enzymes is found in Golgi bodies; AcPase is restricted to small trans-Golgi vesicles while ASase is localized in all the cisterns and vesicles. In addition, some but not all specific granules show both A cPase and ASase activities, mostly associated to their periphery. Thes e results confirm that the granules of mussel granulocytes, although a pparently similar in morphology, are functionally heterogeneous with r egard to enzyme composition. Cortical or peripheral vesicular organell es are negative for AcPase but some are positive for ASase, indicating their endolysosomal nature. Larger vesicles containing remnants of al gal cells do show strong AcPase activity and are thus considered as ph agolysosomes. In controls incubated without no precipitation of reacti on products was detected either for AcPase nor for ASase.