Re-aliment regains feed deprivation-induced microflora dysbiosis and immune stress in the gut of red swamp crayfish (Procambarus clarkii)

Gut microflora plays a key role in host gut health. Unlike feed deprivation, re-feeding has a positive impact on gut health, but their effects on gut microbes remain unclear. Three treatment groups were established in this study to investigate the changes in the gut microbial community and immunity of red swamp crayfish (Procambarus clarkii) under various nutritional states and their functions: Con (the control group, fed for 0 days), Starved (starved for 3 days) and Refed (starved for 3 days, re-fed for 3 days). The results showed that Firmicutes, Bacteroidetes, Deferribacteres and Proteobacteria were the main microbial taxonomy in the gut of P. clarkii. 3-day starvation increased the number of microbial species and their abundance, while the diversity of gut microbes was elevated. The relative abundance of Firmicutes, on the other hand, was significantly reduced, owing to a significant increase in the relative abundance of Deferribacteres (classified as Mucispirillum). 3-day re-feeding restored the number of species and their abundance. Furthermore, starvation induced microbial community disorders by limiting ecological networks and reducing modularity. Re-feeding mitigated the negative effects of starvation on the gut microbial co-occurrence network, increasing the clustering coefficient and the mean network distance, thus maintaining the stability of the gut microbes. Starvation exacerbated the differences in microbial function compared to the control group, while re-feeding restored their function to levels comparable to the control group. Moreover, re-feeding markedly reversed the negative effects of starvation on gut immunity and improved gut health. In conclusion, 3-day starvation disturbed the stability of the gut microbial community, whereas 3-day re-feeding helped to restore the balance of the gut microbial community and its function. It suggested that feed nutrition played an essential role in shaping the gut microbial structure and potentially provided new insights into implications of diet-induced inflammation for gut development in crayfish.