Abstract: Aim: In order to observe the fine structure of phagocytotic hemocytes with an attention to make sure whether oenonytoids are also phagocytotic in the silkworm, Bombyx mori. Methods: Larvae of pnd pS strain of the silkworm were injected with fluorescent microbeads for this experiment. Stained with acridine orange and propidium iodide, the phagocytotic hemocytes were serially scanned for fine structure by the Radiance 2000 confocal scanning laser microscope (Bio-Rad), and confocal fluorescent images were processed with the Lasersharp 2000 software. Results: the observation showed that besides granulocytes and plasmatocytes, some prohemocytes (stem hemocytes) and oenocytoids (prophenoloxidase producer) could also phagocytose fluorescent beads. Furthermore, inside some oenocytoids there were lots of acridine orange green granules that were similar to granules in granulocytes. Spherulocytes were not observed to have phagocytosed any fluorescent beads, but they had large acridine orange green granules. These granules were supposed to be apoptotic bodies which should be introduced by phagocytosis. Conclusion: Besides granulocytes and plasmatocytes, the circulating hemocytes oenocytoids are also phagocytotic in the silkworm.

Key words: Bombyx mori, hemocytes, phagocytosis, fluorescent microscopy