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

Abstract

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.

Phagocytic and enzymatic activities of cells and urn cell complexes in the coelomic fluid of the marine wormSipunculus nudus(Sipuncula)

“…Following Volkonsky (1933), we further distinguished both granulocytes and hyalinocytes into two subpopulations, small and large. In S. nudus, most of the cytoplasmic granules of granulocytes are lysosomes, as indicated by their enzymatic content and affinity to Neutral Red, which typically accumulates inside these organelles, as previously reported in P. agassizii (Dybas, 1981b).…”

“…In vitro phagocytic assay revealed that both granulocytes and hyalinocytes are phagocytes -in contrast with previous results for the same species (Valembois & Boiledieu, 1980), and for P. vulgare (Volkonsky, 1933) and P. agassizii (Dybas, 1981b) in which phagocytic activity was reported only for granulocytes, but in agreement with those reported for Golfingia capensis in which all leukocyte types ingest thorium particles (Brown & Winterbottom, 1969). In the case of uptake of large foreign particles, Ladreyt (1903) considered that phagocytes pass through the nephridial wall and incorporate themselves into the nephridial cells, which then cut off and eject their tips.…”

“…In sipunculans, the phagocytised material undergoes intracellular digestion mediated by lysosomal hydrolytic enzymes, such as acid phosphatase, alkaline phosphatase and lipase detected in granulocytes of P. agassizii (Dybas, 1981b). We demonstrated that all leukocyte types of S. nudus are positive to some hydrolytic and oxidative enzymes, although their distribution may be different among these cell types.…”

“…Granulocytes are involved in defence mechanisms against pathogens and foreign materials, as observed in both in vitro and in vivo phagocytosis assays in P. vulgare (Volkonsky, 1933), Dendrostomum zostericolum (Triplett et al, 1958), P. agassizii (Dybas, 1981b) and Themistepetricola (Blanco et al, 1995). The in vitro phagocytic activity of T. petricola is enhanced when coelomic fluid is present in the culture medium or when yeast is preincubated in cell-free coelomic fluid, indicating the presence of soluble opsonins (Blanco et al, 1995).…”

“…Granulocytes are characterised by numerous granules distinguished into acidophils and basophils, as described in Phascolosoma agassizii (Dybas, 1981b). Urn cell complexes are large, ciliated, multicellular systems (Dybas, 1981a).…”