Effects of temperature changes on oxidative stress and mud crab reovirus (MCRV) replication in mud crab (Scylla...

The mud crab (Scylla paramamosain) is an important species in marine aquaculture along China's southeast coast, but seasonal epidemic diseases, particularly those caused by mud crab reovirus (MCRV), have increasingly threatened its health. This study investigates the impact of temperature fluctuations on MCRV outbreaks from March to June 2024. A total of 160 mud crabs (80 healthy and 80 diseased) were tested for MCRV. Based on the monitored temperature data of mud crab aquaculture water, indoor simulation experiments were designed with different temperature groups to explore the effects of temperature changes on the survival rate, oxidative stress and apoptosis-related indexes of mud crab. Results showed that from March to May, MCRV infection in healthy crabs increased rapidly, reaching 100% in May, while diseased crabs remained 100% infected. The water temperature fluctuated sharply in early March, with a maximum daily difference of 11 °C, before stabilizing in April. In the fluctuating-temperature group, survival rates were lowest (25%), and MCRV levels peaked at 8.5 × 10⁸ copies/μL by day 8. Antioxidant enzyme activities, including superoxide dismutase (SOD) and glutathione reductase (GR), showed significant changes in this group. Additionally, immune enzymes such as phenoloxidase (PO) and lysozyme (LZM) exhibited varying trends, with the most pronounced changes in the fluctuating-temperature group. Gene expression levels of heat shock protein (Hsp70) and cysteine-aspartic acid protease-3 (Caspase-3) were also significantly altered. This study enhances the understanding of the relationship between mud crabs and MCRV under temperature stress and provides insights for improving environmental control strategies to prevent seasonal epidemics, supporting sustainable aquaculture development.