Effects of chlorpyrifos stress on the Eriocheir sinensis suffering from Metschnikowia bicuspidata infection

Abstract

This study investigated the effects of chlorpyrifos (CPF) stress on the prevalence of “milky disease” caused by Metschnikowia bicuspidata in Chinese mitten crabs (Eriocheir sinensis), a key issue affecting crab aquaculture. The 96 h LC₅₀ of CPF was determined to be 0.568 mg/L. The experimental setup included a control group (no CPF exposure) and three CPF-treated groups exposed to low (0.0189 mg/L), medium (0.0568 mg/L), and high (0.189 mg/L) CPF concentrations. Over a 7-day period, histomorphological analyses, immune enzyme activity assessments, and gene expression evaluations were conducted. CPF exposure resulted in appendage rigidity, neurological symptoms, and increased severity of “milky disease” and hepatopancreatic damage. Yeast proliferation on day 7 increased with CPF concentration and was significantly higher in CPF-exposed crabs when low doses of M. bicuspidata were injected. Crabs subjected to higher CPF doses and infection showed elevated mortality rates. Physiological tests revealed CPF exposure reduced antioxidant defenses by inhibiting acid and alkaline phosphatase activities and altering phenol oxidase, malondialdehyde, lysozyme, and glutathione peroxidase levels. Transcriptome analysis showed CPF exposure impaired lipid metabolism, energy supply, and oxygen transport pathways, weakening immune defense mechanisms. These results demonstrate that CPF exposure reduces immune function and antioxidant capacity, thereby accelerating M. bicuspidata proliferation and worsening disease outcomes. This study offers critical insights into the role of environmental stressors in the spread of “milky disease,” providing valuable guidance for sustainable crab aquaculture practices.