Changes in the Immunity, Histopathology, and Metabolism of Crayfish (Procambarus clarkii) in Response to Drought

SIMPLE SUMMARY: The freshwater biodiversity crisis is in the spotlight due to the destruction of freshwater ecosystems. Factors threatening freshwater biodiversity are much wider and more complex, including climate change and severe weather events such as drought, unexpected floods, heavy storms, etc. Drought is an important factor contributing to this crisis. In this study, we evaluated changes in the immune function, antioxidant function, histopathology, and metabolites of crayfish in response to drought. The results indicate that drought suppresses immune function, the balance between oxidative and antioxidative systems, and induces tissue damage and metabolic disorder. Our work provides more information on how crayfish respond to drought. ABSTRACT: Freshwater ecosystems are among the most threatened ecosystems on Earth. The freshwater biodiversity crisis has caused widespread global concern. Drought as one of the factors causing freshwater biodiversity is still poorly understood. Crayfish is often used in academic research as a biological indicator. In this study, flow cytometry, hematoxylin-eosin staining, and untargeted metabolomics were used to analyze the immune function, histopathology, and metabolism of crayfish under drought conditions. After drought exposure, the total hemocytes count (THC) was significantly decreased (from 8.9 × 10(5) mL(−1) in the control group to 2.2 × 10(5) mL(−1) at day 5). Phagocytosis decreased by 66% after 5 days of drought. The level of reactive oxygen species (ROS) in the hepatopancreas was upregulated. Moreover, histological disorder and metabolism changes in the hepatopancreas were obvious. These results indicate that drought suppresses immune function, disrupts the balance of oxidative and antioxidative systems, and induces tissue damage and metabolic changes in crayfish.