Effect of yeast polysaccharide on the immune function of juvenile sea cucumber, Apostichopus japonicus Selenka under pH stress

Abstract

In the present study, we evaluated the effect of yeast polysaccharide (YSP) on the immune function of Apostichopus japonicus at different pH levels. Juvenile sea cucumbers were fed artificial feed containing 0.5% YSP. Phagocytic activity and activity of lysozyme (LSZ), acid phosphatase (ACP) and alkaline phosphatase (ALP) were measured under pH stress after 24 h. The results showed that the phagocytic index, the activity of LSZ and ACP in the intestines increased at pH 10.0, and ACP activity in the body wall decreased. The phagocytic rate and ALP activity in the intestines were not different from the control group. The phagocytic index was also not different from the control group at pH 5.5. The activity of LSZ and ACP in the intestines and the activity of ALP increased, while the activity of ACP in the body wall decreased. The phagocytic rate of YSP group increased and the phagocytic rate of control group decreased. Thus, this study indicated that YSP can modulate the non-specific immunity of A. japonicus, and the reasonable dose of YSP might be used as the immunostimulants in sea cucumbers farming under pH stress.