Number and types of hemocytes in Sunetta scripta and Villorita cyprinoides var. cochinensis (Bivalvia), and leukocytosis subsequent to bacterial challenge

Abstract

The number and types of hemocytes in four size groups of the clam species Sunetta scripta and Villorita cyprinoides var. cochinensis, and leukocytosis in the 38- to 40-mm-size-group clams of both species subsequent to challenge with Vibrio alginolyticus at a concentration of 1 × 10 8 cells/0.02 ml of sterile 2% saline was investigated. In S. scripta, the mean total hemocyte count in the 42- to 44-mm size group was significantly lower than that of the three other size groups but there was no significant variation in total cell counts in the four size groups of V. cyprinoides var. cochinensis. Only two types of hemocytes, granulocytes and agranulocytes, occur and the percentage of agranulocytes was roughly half of that of granulocytes. The data on the effects of sham injection and Vibrio injection suggest that there is significant leukocytosis early in both clam species as a result of sham injection; the bacterial challenge produces significant leukocytosis in V. cyprinoides var. cochinensis both early (6 and 12 hr) and later (48,96 and 120 hr), but only at 48 hr in S. scripta; and in both clam species there is significant increase in total cell counts in Vibrio-injected ones than in untampered controls at various time intervals.