Nitrite Stress on Density of Hemocyte and Phenoloxidase Activity in Hemolymph of <i>Charybdis japonica</i>

Abstract

In order to discuss the effects of nitrite on the density of hemocyte (DHC) and phenoloxidase (PO) activity in hemolymph of Charybdis japonica, the crabs were exposed to six nitrite-N groups (0, 2.0, 4.0, 6.0, 8.0 and 10.0 mg L-1 ambient nitrite-N concentrations). The DHC and PO activity was examined on days 1, 3, 5, 10 and 15 following the stress. Results showed that the two indexes appeared to have a decline trend after an initial ascent. After 1 day treatment, the DHC of five treatments were higher than that of the control group respectively, while the PO activity of 8.0 and 10.0 mg L-1 nitrite-N exposed group decreased compared with control. With time elapsed, the DHC of lower concentration nitrite-N exposed group increased faster, while the PO activity of higher concentration nitrite-N exposed group rised faster than other treatments. After 15-day stress, all parameters tested were lower than those of control group barring the DHC of 2.0 and 4.0 mg L-1 nitrite-N exposed group and the PO activity of 2.0, 4.0, and 6.0 mg L-1 nitrite-N exposed group.