Ultrastructural and cytochemical study of the Golgi complex of molluscan (Mytilus galloprovincialis) digestive cells

Abstract

The present study has been performed to investigate the ultrastructure and subcellular distribution of several marker enzymes within the Golgi complex of digestive cells of the mussel, Mytilus galloprovincialis. This cell type is involved in the intracellular digestion of food and contains a well-developed lysosomal-vacuolar system and a characteristic cup-shaped Golgi complex. The number and degree of compaction of the tubulo-filamentous structures extending across the distended regions of the cisternae, the number of Golgi stacks per cell and the number of cisternae per stack vary with season and nutritional status of the animals. The degree of compaction of the tubulo-filamentous structures defines the cis- and trans-portions of the Golgi apparatus, the less compacted structures being associated with the cis-portion. Acid phosphatase and arylsulphatase activities are located within some tubules and vesicles in the trans-Golgi network and in some membrane-bounded organelles comprising the lysosomal-vacuolar system. The tubulo-filamentous structures of the dilated rims are reactive for arylsulphatase activity only when located in the trans-portion. Osmium impregnation techniques label all the cisternae of the Golgi complex. No nicotinamide adenine dinucleotide phosphatase activity is present in Golgi bodies or other associated structures in digestive cells. Thiamine pyrophosphatase activity only rarely occurs in some elongate tubules that are interpreted as belonging to trans-cisternae.