Immune and intestinal microbiota responses to heat stress in Chinese mitten crab (Eriocheir sinensis)

Temperature is an important environmental stressor that affects the metabolism and immunity of Chinese mitten crab. In this study, we investigated immune-related enzyme activity, metabolism-related substances in haemolymph and intestinal microbiota responses of Eriocheir sinensis assigned to the control (24 °C) and heat stress (32 °C) groups. Based on the data obtained, the levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and lactate dehydrogenase in the heat stress group exhibited a trend of increasing first and then decreasing, and all peaked at 12 h or 24 h. The metabolism-related substances in the haemolymph, including glucose, total cholesterol, and total protein, all showed significant differences between the control and heat stress groups from the mid to late period (P < 0.05). Under heat stress, the levels of alkaline phosphatase and acid phosphatase were both significantly higher than those of the control group from 12 h to 24 h and significantly lower at 72 h and 96 h (P < 0.05). The T-AOC of the heat stress group was significantly lower than that of the control group from 48 h to 96 h (P < 0.05). High-throughput 16S ribosomal DNA (rDNA) sequencing revealed that heat stress altered the composition of intestinal microbes of Eriocheir sinensis. Specifically, the abundance of the beneficial bacteria Candidatus, Hepatoplasma and Marinifilum decreased significantly, while the abundance of the pathogenic bacteria Rhodococcus and Morganella increased significantly (P < 0.05). The results revealed that acute heat stress exposure affected immune function and intestinal microbial community in E. sinensis. This work can help to uncover the mechanisms of heat stress responses in this species.