Abstract

This study investigated morphological and immunological functions of hemocytes from hard clam, Meretrix petechialis for determination of proper sediment composition and rearing density. The hard clams were cultured with various ratio of sand:mud (100:0, 70:30, 50:50, 30:70, 0:100) and rearing density (50, 100, 150 individuals/m2). After 4 weeks, viability, phagocytosis, reactive oxygen species (ROS)-release and apoptosis were analyzed by flow cytometry in the hemocyte of hard clam. Main types of hemocyte from hard clam were identified as hemoblast-like cell, agranulocyte, granulocyte and degranulated cell. In the sediment composition test, ROS-release was significant low at 70:30 and 50:50 although there were no significant differences in viability, phagocytosis and apoptosis under various conditions. In rearing density test, phagocytosis showed the highest value at density of 100 individuals/m2 and decreased at 150 individuals/m2. Also ROS-release increased rearing density-dependently. These results suggest that 50-70% of sand composition and rearing density less than 100 individuals/m2 would be a proper condition for hard clam culture. Moreover, Phagocytosis and ROS release would be useful indicators for physiological condition in artificial culture.