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In this study, the non-specific immunostimulatory effect of alginate oligosaccharides (AOSs) with three types of molecular weights, namely, A 1 = below 1 kD (polymerization of 2–5), A 2 = 1 kD to 2 kD (polymerization of 5–10), and A 3 = 2 kD to 4 kD (polymerization of 10–20), as well as their two types of corresponding purified uronic acid oligomers (mannuronate and guluronate oligomers) on sea cucumber ( Apostichopus japonicus ) coelomocyte were investigated in vitro. Coelomocytes cultured in L-15 medium containing different AOS concentrations (0, 50, 100, 200, or 400 μg mL − 1 ) were sampled, and non-specific immune responses, such as phagocytic capacity, reactive oxygen species, lysozyme activity, peroxidase activity, total nitric oxide synthase and acid phosphatase activity were determined and compared with those of the control samples (i.e., treatments without immunostimulants) after exposure to AOS for 3, 6, 12, or 24 h. Most of the above mentioned immune parameters were significantly ( P 1 group showed better effects on phagocytic capacity, lysozyme activity, peroxidase activity and total nitric oxide synthase of coelomocytes because of the higher increase, earlier appearance, and longer duration time than those of the A 2 and A 3 groups. Furthermore, among the significant differences of various molecular weights of the AOS groups relative to the control sample, these immune parameters in mannuronate or guluronate oligomer groups were all significantly higher than those in the control sample ( P 1 mannuronate group had a higher increase in phagocytic activity than that of guluronate, and no significant difference was observed in other immune parameters between corresponding mannuronate and guluronate oligomer groups. These results indicated that AOS could enhance the non-specific immune response of sea cucumber coelomocytes in vitro and provided basic information regarding AOS as a potential immunostimulant in sea cucumber culture.

The effect of a commercially available compound probiotics product containing Bacillus subtilis YB-1 (50%) and Bacillus cereus YB-2 (50%) fed to sea cucumbers, Apostichopus japonicus (Selenka) on challenge infections and non-specific immune responses was assessed. Sea cucumbers (were randomly allocated into nine aquariums at a density of 30 sea cucumbers per tank and triplicate groups) were fed diets containing 0 (control), 107 and 1010 cfu (g diet)−1 of the probiotics mixture for 32 days. The growth factors and immunological parameters were measured. In addition, the effects on resistance against Vibrio alginolyticus infection were also evaluated. The results indicate that all the immunological parameters (phagocytic activity, superoxide anion production, lysozyme activity, catalase activity and phenoloxidase activity) measured and the growth rate of sea cucumbers fed 1010 cfu of the probiotics mixture were significantly (P 0.05), Bacillus sp. levels were significantly elevated in sea cucumbers fed the probiotics mixture (P

This feeding trial was conducted to determine the vitamin E requirement of sea cucumber (Apostichopus japonicus) and to study the effects of vitamin E on nonspecific immune parameters. Commercial sea cucumber diets supplemented with 0, 50, 100, 200, 500 or 1000 mg kg−1 vitamin E were fed to juvenile sea cucumber (7.96 ± 0.01 g) for 60 days. Specific growth rate and total coelomocyte counts were maximized in sea cucumber fed diets supplemented with 100 mg kg−1 vitamin E. Reactive oxygen species production was maximized at 50 mg kg−1 vitamin E, whereas superoxide dismutase activity was the highest in sea cucumber fed diets supplemented with 100 mg kg−1 vitamin E. The vitamin E concentration in the body wall of the sea cucumber increased as the vitamin E level in the diet increased. Analysis of specific growth rate and total coelomocyte counts of the sea cucumber indicated that 88–92 mg kg−1 vitamin E is required for maximal growth and nonspecific immune responses of A. japonicus and that 114.7 mg kg−1 vitamin E is required to minimize lipid peroxidation levels.