Effects of rusted copper alloy in prevention and control of cryptocaryoniasis in large yellow croaker Larimichthys crocea

Abstract

Copper alloy can be used to prevent and control cryptocaryoniasis in marine fish. However, it is not known whether the soaking corrosion of seawater can affect the parasiticidal effect of copper alloy. This study compared the killing effects of copper alloy mesh (CAM) and rust copper alloy mesh (RCAM) on the protomonts and tomonts of Cryptocaryon irritans and the control effects of cryptocaryoniasis in Larimichthys crocea. Results showed that with the increase of contact time with CAM and RCAM, the survival rate of the protomonts and tomonts of C. irritans were gradually decreased. The contents of Cu²⁺ and malondialdehyde (MDA) in the tomonts gradually increased, while the activities of superoxide dismutase (SOD), Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase in the tomonts increased first and then decreased. Morphological observation showed that sufficient contact with CAM or RCAM damaged the cyst wall of the tomonts, and the cytoplasm have lysed and spilled out of the cell. In the treatment test of diseased fish, at the end of the assay (14 d), the survival rates of L. crocea in the CAM treatment group (group B) and the RCAM treatment group (group C) were 77.77% and 64.44%, respectively, which were significantly higher than those in the untreated group (group A, 0.00%) (P < 0.05). RCAM could still successfully prevent the outbreak of cryptocaryoniasis in a short time. Our study serves as a theoretical reference for the long–term application of metal materials in the prevention and control of cryptocaryoniasis in marine fish.