Effects of dietary supplementation with Haematococcus pluvialis on the growth, antioxidantase activities, and gut microbiota of Chinese mitten crab (Eriocheir sinensis)

Abstract The Chinese mitten crab ( Eriocheir sinensis ) is bred extensively in Eastern and Northern China and faces a series of problems such as frequent diseases, germplasm degradation, and declining benefits, which have appeared to seriously affect the sustainable development of the cultivation industry. Haematococcus pluvialis , a type of unicellular green algae, have been proven to be the suitable dietary supplementation in crustacean feeds. After 14 days of feeding with 5% dietary supplementation with Haematococcus pluvialis powder, the growth, antioxidantase activities, and gut microbiota of E. sinensis were analyzed. The results indicated that H. pluvialis powder could significantly improve growth indicators including weight gain rate (WGR) and specific growth rate (SGR) of E. sinensis ( p < 0.05). The levels of superoxide dismutase (SOD) and catalase (CAT) declined, while that of phenoloxidase (PO) kept rising under the treatment of H. pluvialis powder. Moreover, alkaline phosphatase (AKP) activity dropped initially and then increased. No significant differences in the Simpson index and Chao1 index in the control and H. pluvialis powder treatment were observed ( p > 0.05). Although the dominant microbiota in the crab gut were not affected significantly by H. pluvialis powder, significant differences in the relative abundance of the dominant phyla between the control and H. pluvialis powder treatment groups were observed ( p < 0.05). Furthermore, the relative abundance of Firmicutes and Candidatus_Bacilloplasma, which play an important role in the life activities of E. sinensis , were significantly higher in the group treated by H. pluvialis powder than in the control ( p < 0.05). Therefore, the H. pluvialis powder could be potentially used not only as a rapid fattening regulator, but also to improve the immunity and metabolic capacity of E. sinensis .