| Crab were coelom injected with 2,4 mg yeastβ-glucan kg?1 crab weight, with injected 0.1mL saline and blank group as controls. The total haemocyte count (THC), different haemocyte count (DHC), the haemocyte phagocytic activity, respiratory burst (release of superoxide anion), the total phenoloxidase(PO)in haemocyte lysate supernatant (HLS), phenoloxidase (PO), peroxidase (POD), superoxide dismutase (SOD), acid phosphatase (ACP), alkaline phosphatase (ALP), catalase(CAT), lysozyme (LSZ), homolysin, antimicrobial activity in the serum were examined at 0, 1, 3, 5, and 8 days after administration ofβ-glucan. Crab were challenged at 1.2×107 colony forming units (cfu)/kg crab weight with a virulent strain of Aeromonas hydrophila (CL99920) of E. sinensis at the second sampling time (3d), and mortalities were recorded over a 7-day period. The results showed that the THC, the phagocytic activities and respiratory burst of haemocytes, the POD, SOD, ACP, ALP, CAT, LSZ, antibacterial activities and homolysin in serum of E. sinensis injected with 2 mg yeastβ-glucan kg?1 crab weight were higher than those of the control group and saline control group (P<0.05). However, no significant differences were observed in the DHC of E. sinensis among the crabs injected with 2,4 mg yeastβ-glucan kg?1 crab weight compared with control group and saline control group (P>0.05). Furthermore, the crabs injected with 2 mg yeastβ-glucan kg?1 crab weight were the more resistant. It was concluded that yeastβ-glucan could enhance the non-specific immune response and resistance to A. hydrophila of E. sinensis.
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