Effects of eyestalk ablation on the ecdysone and chitinase levels and N-acetyl-β-D-glocosaminidase activity of the freshwater crab(Sinopotamon henanense)

Molting is an essential stage during the growth of crustacean,which is coordinated by ecdysone secreted by Y-organ,chitinase synthesized by the epidermis;while negatively regulated by molting-inhibiting hormone secreted by X-organ sinus-gland complex at the bottom of eyestalk.However,the specific mechanisms of the molting triggered by eyestalk ablation are still unknown.In this study,two eyestalks were ablated and the ecdysone level in Sinopotamon henanense haemolymph and chitinase level in the epidermis were measured by ELISA,and N-acetyl-β-D-glocosaminidase(β-NAGase)activity in the epidermis was measured by colormetry.Crabs were divided into one control group and seven eyestalk ablation groups respectively(from 24 hours to 168 hours).Our results showed that the level of ecdysone in haemolymph showed an increase at first and then decrease,with the maximum value at 96 h.♂:(23.25±4.56) ng/L;♀:(35.75±7.15) ng/L,P<0.01.This tendency was accompanied by similar changes as that of chitinase levels in the epidermis.After the two eyestalks were ablated for 48 h to 120 h,chitinase level increased significantly(compared with the control group,P<0.05).Activity of β-NAGase increased continuously by the eyestalk ablation and reached the maximum value at 144 h♂:(400.44±21.00) U/g;♀:(216.94±23.97) U/g,P<0.05.Then the activity of β-NAGase decreased gradually,but still higher than that of control group.The results imply that eyestalk ablation may affect the molting process by increasing the levels of ecdysone in the haemolymph,chitinase in the epidermis and the activity of β-NAGase.This study will provide the theoretical basis for the further study on the physiological regulation of crustacean molting and growth.