Effects of Dietary Yeast Polysaccharides on the Immune Responses of Apostichopus japonicus to a Sudden Drop in Temperature

Abstract

The effect of yeast polysaccharides (YSPs) on immune function was evaluated in sea cucumber, Apostichopus japonicus, exposed to two protocols of acute decrease in temperature (T5 group: 20 C → 15 C → 10 C → 4 C; T10 group: 20 C → 10 C → 4 C). Juvenile sea cucumbers were fed an artificial diet containing 0.5% YSP. The phagocytic rate and index and the activities of lysozyme, acid phosphatase, and alkaline phosphatase were measured 24 h after each drop in temperature. The immune indices generally decreased in animals fed the basal diet (BD) in both temperature-change protocols. Supplementing the feed of A. japonicus with YSPs led to increases in most indices compared with those fed the BD, except for the phagocytic index at 10 C in the T5 group. Therefore, the addition of YSPs to the BD improves the immunocompetence of A. japonicus during exposure to a rapid decrease in temperature.