Changes in Hemolymph Microbiota of Chinese Mitten Crab () in Response to or Infection.

The Chinese mitten crab () has significant economic potential in both the Chinese domestic and global markets. The hemolymph microbiota is known to play a critical role in regulating physiological and biochemical functions in crustaceans. However, the study of the hemolymph microbiota of in response to infections has not been undertaken. In this study, changes in the composition and function of the hemolymph microbiota in infected with either (Sa) or (Ah) were investigated using 16S rRNA sequencing, with a phosphate buffer saline (PBS) injection serving as the control. Results showed that the dominant hemolymph microbiota of were Proteobacteria, Bacteroidota, and Firmicutes. The relative abundance of the phyla Firmicutes, Bdellovibrionota, and Myxococcota was significantly reduced in both Sa and Ah groups compared to the PBS group. At the genus level, compared to the PBS group, a significant increase in the abundance of and was found in both Ah and Sa groups. The analysis of the functional profile showed that pathways related to 'cell growth and death', 'metabolism of terpenoids and polyketides', 'cancers', 'lipid metabolism', 'neurodegenerative diseases', 'metabolism of other amino acids', 'xenobiotics biodegradation and metabolism', and 'circulatory system and endocrine system' were predominant in the Ah group. Meanwhile, pathways related to 'metabolism or genetic information progressing', such as 'translation', 'metabolic diseases', and 'cellular processes and signaling', were enriched in the Sa group. This study revealed the effects of pathogens ( or ) on the maintenance of the hemolymph microbiota in . It shed light on the mechanisms employed by the hemolymph microbiota of under pathogen stimulation.