Light and Electron Microscopical Localization of Lysosomal Acid Hydrolases in Bivalve Haemocytes by Enzyme Cytochemistry.

Abstract

In the present work the haemocytes of mussels Mytilus galloprovincialis(Mollusca, Bivalvia) have been studied by enzyme cytochemistry in orderto investigate the light and electron microscopical distribution of twolysosomal marker enzymes, acid phosphatase (AcPase) and arylsulphatase(ASase). Both hyalinocytes and granulocytes show positive reactionproducts for the two enzymes but granulocytes are far more reactive. Inthe hyalinocytes, AcPase and ASase activities are observed in a fewpleomorphic lysosomes. In the granulocytes, the reaction product for theenzymes is found in Golgi bodies; AcPase is restricted to smalltrans-Golgi vesicles while ASase is localized in all the cisterns andvesicles. In addition, some but not all specific granules show bothAcPase and ASase activities, mostly associated to their periphery. Theseresults confirm that the granules of mussel granulocytes, althoughapparently similar in morphology, are functionally heterogeneous withregard to enzyme composition. Cortical or peripheral vesicularorganelles are negative for AcPase but some are positive for ASase,indicating their endolysosomal nature. Larger vesicles containingremnants of algal cells do show strong AcPase activity and are thusconsidered as phagolysosomes. In controls incubated without noprecipitation of reaction products was detected either for AcPase norfor ASase.