RESPONSE OF EOSINOPHILIC GRANULE CELLS OF GILTHEAD SEABREAM (SPARUS-AURATA, TELEOSTEI) TO BACTERIA AND BACTERIAL PRODUCTS

Eosinophilic granule cells in the gills and peritoneal exudate of gilt head seabream (Sparus aurata L.) are characterized by the presence of prominent eosinophilic granules in their cytoplasm and are here descri bed for the first time. The oval granules of these cells contain an el ectron-dense inclusion surrounded by a less dense filamentous matrix a nd are peroxidase- and acid phosphatase-negative. Unlike other granulo cytes of gilthead seabream, eosinophilic granule cells do not ingest b acteria in vivo. The intraperitoneal injection of extracellular produc ts of Pasteurella piscicida induces mobilization of eosinophilic granu le cells to the blood and other tissues and causes changes in their st ructure. Shortly after injection, the granules of eosinophilic granule cells become swollen and some fuse with the cell membrane. From 7 h p ost-injection, many eosinophilic granule cells in the gills degenerate and are then phagocytosed by macrophages, which are especially abunda nt after 24 h. From 24 h to 72 h, eosinophilic granule cells from the gills contain abundant autolysosomes together with granules of a norma l morphology.