Temperature-dependent shifts in the gut microbiota profile of swimming crab Portunus trituberculatus

The swimming crab Portunus trituberculatus is an important economic species in aquaculture. However, the impact of temperature fluctuations on its intestinal microbiota remains unclear. Against the backdrop of growing concerns about the impacts of global warming on ectothermic species, this study investigates the effects of four temperatures (20℃, 23℃, 26℃ and 29℃) on the intestinal histology and microorganisms of P. trituberculatus using HE staining and 16S rRNA high-throughput sequencing. It was revealed that the intestinal duplicature (a key indicator of digestive capacity) in the 26℃ and 29℃ groups had significantly larger length and width compared with those in the 20℃ and 23℃ groups. Also, the sequencing results showed that 307, 326, 478 and 354 representative amplicon sequence variants (ASV) in the intestinal microorganisms of four temperature groups, respectively. The α-diversity analysis revealed that microbial richness and diversity of intestinal microbiota were significantly higher in the higher temperature groups (26℃, 29℃) than in the lower temperature groups (20℃, 23℃). Specifically, richness peaked at 29℃, while diversity indices slightly decreased at 29℃ compared to 26℃ but remained higher than at lower temperatures. The β-diversity analysis also revealed that the intestinal microbiota diversity in the higher temperature groups (26℃, 29℃) was higher than that in the lower temperature groups (20℃, 23℃). At the phylum level, the dominant intestinal flora in all four temperature groups were Proteobacteria , Fusobacteriota and Firmicutes , which accounted for 90% of the entire intestinal flora of P. trituberculatus . At the genus level, the abundance of Photobacterium , Hypnocyclicus , Bacteroides , Muribaculaceae and Citrobacter in the 29℃ group was higher than that of other groups. Among them, Bacteroides was involved in lipid metabolism. KEGG enrichment showed significantly higher abundance of differential microorganisms in the “Digestive system” and “Transport and catabolism” pathways in the higher temperature groups (26℃, 29℃) than in the low temperature groups (20℃, 23℃). Collectively, higher temperatures (26℃, 29℃) significantly increased the length and width of intestinal duplicator and altered the composition of intestinal microorganisms—particularly taxa associated with digestive and metabolic functions. These changes in intestinal structure and microbial function collectively affected the physiological metabolism of P. trituberculatus .