An Increase in Immune Response and Protection against Vibrio Alginolyticus in the White Shrimp Litopenaeus Vannamei after a Fucoidan Immersion

White shrimp Litopenaeus vannamei that immersed in seawater containing fucoidan at 0 (control), 100, 200 and 400 mg/l after 5 h were challenged with Vibrio alginolyticus at 6 x 106 colony-forming units (cfu)/shrimp, and then placed in seawater. The survival rate of shrimp that immersed in seawater containing fucoidan at either dose was significantly higher than that of control shrimp over 48~120 h. In another experiment, hemocyte count, phenoloxidase (PO) activity, respiratory burst (RB), superoxide dismutase (SOD) activity, and glutathione peroxidase (GPx) activity, phagocytic activity and clearance efficiency against V. alginolyticus were examined when the white shrimp L. vannamei were immersed in seawater containing different concentrations of fucoidan (0, 100, 200, and 400 mg/l) for 1, 3, and 5 h. These immune parameters increased directly with the concentration of fucoidan and exposure time. White shrimp L. vannamei that immersed in seawater containing fucoidan at 100, 200, and 400 mg/l had increased phagocytic activity and clearance efficiency against V. alginolyticus. It was concluded that the shrimp immersed in seawater containing fucoidan at a concentration of 100 mg/l exhibited an immunomodulatory effect, as well as protection against V. alginolyticus infection.