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This study examined the effects of Bacillus licheniformis strain CIGBC-232, isolated from the gut of shrimp Litopenaeus vannamei and having antagonistic activity against Vibrio harveyi, on the immunity and larval quality of L. vannamei at various ontogenetic stages, in two separate experiments:(1) PL2 to PL17 exposed to the strain CIGBC-232 under laboratory conditions (2) zoea I to PL8 exposed to the strain CIGBC-232 and EPICIN 3W probiotics under farming conditions. The first experiment showed that phenoloxidase, peroxidase and superoxide dismutase activities were improved in animals grown with CIGBC-232 compared to the untreated control. In tests, the resistance to osmotic stress was also enhanced. During the second experiment, animals treated with CIGBC-232 exhibited significant (P < 0.05) increases in phenoloxidase activity (30-40% higher in zoea I-II, mysis II-III and PL 2-7) and in the respiratory burst (30% higher from PL 2 to 7) as compared to those animals that received EPICIN 3W. There was no significant difference in the lectins and agglutinins (except in PL1, 6 and 7), in peroxidase and superoxide dismutase activities, in the resistance to osmotic stress, nor in the survival rate among treatments. CIGBC-232 treatment was able to reduce, the level of presumptive Vibrio spp. with respect to EPICIN 3W treatment in the tank water as well as in animals. At the end of both experiments, the growth of shrimp, i.e. weight and length was increased by CIGBC-232 treatment. This study showed the probiotic effect of CIGBC-232, which appeared to have a better probiotic performance than EPICIN 3W treatment.

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The effects of Psychrobacter sp., isolated from the gut of shrimp Penaeus vannamei Boone, 1931, on growth, digestive enzyme activities, total protein content, osmotic stress resistance, immunity and disease resistance of postlarvae were investigated. For enzymatic activities assays whole postlarvae were homogenized. Shrimp subjected to Psychrobacter sp. treatment showed higher weight (40%) and length (5.6%) than that observed in untreated animals. Compared to the untreated control group, levels of protease and amylase activities in postlarvae, were higher in the probiotic group. Postlarvae treated with Psychrobacter sp. showed significantly increase in the survival compared to the untreated ones after osmotic stress. Nitric oxide metabolite levels and the enzymatic activities of phenoloxidase, superoxide dismutase and peroxidase from treated postlarvae were significantly higher than untreated postlarvae. Increased survival was also found after challenge with Aeromonas sp. This is the first study that demonstrates the probiotic effect of Psychrobacter sp. in P. vannamei postlarvae.