Haemocytes and phenoloxidase activities during the molting cycle of mud crab

Abstract

The total haemocyte count and phenoloxidase activities of mud crabs throughout the 12 stages in the molting cycle were observed. The results showed that total haemocyte counts ranged from (5.02 ± 1.90)×106 to (17.64 ± 9.98)×106 cellml-1. Haemocyte numbers were higher in the postmolt (P<0.05) than those in the intermolt and premolt stages. Levels of phenoloxidase activities ranged from 0.65 ± 0.13 to 3.93 ± 2.48, 2.27 ± 0.33 to 7.40 ± 0.85, 0.52 ± 0.29 to 4.89 ±1.72 and 0.93 ± 0.21 to 3.65 ±1.80 units mg proteins-1 in the hepatopancreas, gill, integument and haemolymph, respectively. Phenoloxidase clearly showed activities in the gill and integument during the postmolt stage while that in the hepatopancreas was obviously found at the premolt stage. However, phenoloxidase activity in the haemolymph was distinctively high at 6 h early postmolt. This research has demonstrated that haemocyte count and phenoloxidase played an important role in the sclerotization, melanization and immunity system of crabs.