CELLULAR DEFENSE REACTIONS OF PHASCOLOSOMA AGASSIZII, A SIPUNCULAN WORM: PHAGOCYTOSIS BY GRANULOCYTES

¹ Department of Biology, Knox College, Galesburg, Illinois 61401

Based on Wright's blood stain, uninucleate circulating granulocytes of the sipunculan Phascolosoma agassizii Keferstein are of two types: acidophils and basophils. The granulocytes are characterized by numerous granules scattered throughout the cytoplasm. Morphology of the granulocytes viewed with the light and electron microscope is illustrated and described. The granules of the granulocytes contain the enzymes acid phosphatase, alkaline phosphatase, lipase, and peroxidase. Fibrin-like strands entrap foreign particles—polystyrene latex beads and Staphylococcus aureus—introduced into the coelomic fluid in vivo or in vitro. Granulocytes accumulate in the vicinity of the trapped foreign particles. Both acidophilic and basophilic granulocytes phagocytize polystyrene latex beads and Staphylococcus aureus in vivo and in vitro. The cytoplasmic granules of the granulocytes degranulate into the phagocytic vacuoles and new granules form from the concave face of the Golgi complex.