Stress responses of the intestinal digestion, antioxidant status, microbiota and non-specific immunity in Songpu mirror carp (Cyprinus carpio L.) under starvation.

Songpu mirror carp, Cyprinus carpio L., is a new variety of common carp that has become an economically important freshwater fish in China. However, it remains unknown how its metabolism is regulated under starvation. Here, we investigated how intestinal digestion, antioxidant status, microbiota and immune activities were affected under starvation stress. The feeding regimes were designed as follows: ST0 comprised fish allowed to feed continuously; ST1 comprised fish starved for 1 week; ST2 comprised fish starved for 2 weeks; ST3 comprised fish starved for 3 weeks; ST4 comprised fish starved for 4 weeks. Our results showed a significant decrease in the level of intestinal amylase, lipase, and protease activities in the group ST4 (P < 0.05). Compared with the control group, intestinal antioxidant enzyme activities were significantly increased during short-term starvation. The gene expression levels of interleukin 1ß (IL-1ß), interleukin 8 (IL-8) and tumor necrosis factor-alpha (TNF-α) were elevated in the groups ST3 and ST4. We also detected the reduction in the expression levels of interleukin 10 (IL-10) and transforming growth factor ß (TGF-ß2) compared with those of the group ST0. Notably, the gut microbial composition was dominated by Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. The relative abundance of the dominant microbial phyla changed significantly under starvation stress. Taken together, our results suggest that starvation can induce the change of intestinal digestion, non-specific immunity and microbiota in Songpu mirror carp, and provide new insights into its habitat selection and adaptation to environmental changes.