Flow cytometric characterization of hemocytes of the abalone Haliotis diversicolor (Reeve, 1846) and effects of air exposure stresses on hemocyte parameters

Abstract

The variously colored abalone Haliotis diversicolor is widely distributed in the northwest Pacific region and commonly occurs in shallow subtidal regions of Jeju Island, off the south coast of Korea. In this study, we first characterized the morphology and immune-related activities of H. diversicolor hemocytes using flow cytometry and light microscopy. Flow cytometry revealed three types of hemocytes in the hemolymph: granulocytes, hyalinocytes, and blast-like cells. Hyalinocytes were the largest and most abundant, while granulocytes were intermediate-sized and contained many granules in the cytoplasm. Flow cytometry indicated that granulocytes were mainly involved in phagocytosis and oxidative activities, although hyalinocytes also exhibited a certain level of immune-related activities. Blast-like cells were the smallest and exhibited a lack of phagocytosis and oxidative capacities. To understand the adaptive capacity to air exposure, abalones were exposed to air or humidity over 30 h. All abalones perished within 24 h after dry-air exposure, while 20% of abalones had survived under humid conditions by the end of the experiment. After 6 h of air exposure and 12 h of humidity, total hemocyte counts and phagocytosis capacity declined dramatically, and the level of hemocyte DNA damage increased significantly (P < .05). This study suggests that sufficient oxygen supply during transportation could enhance the survival of H. diversicolor, thereby improving its market value.