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nin nisms of immune defence against diseases in crabs might be beneficial to the management of crustacean farming practice. Both cellular and humoral responses are involved in the process of crustacean recognizing and destroying non-self materials, e.g. microbial pathogens [4]. Cellular immune responses such as cell melanisation process observed in response to infection, and which is also occurs in cuticular wounds or nodules and capsule forma-tion around invading parasites [18,19]. The invertebrate proPO gene was first purified and cloned from the freshwater signal crayfish, Pacifastacus leniusculus [20,21], and the second proPO gene was cloned from Penaeus monodon in 1999 [22]. Subse-quently, a lot of proPO genes have been identified and cloned from a variety of arthropods species [23–28]. All of these proPOs contain two functional copper-binding sites and a proteolytic activatio