Indigenous Lactobacillus plantarum as probiotic for larviculture of blue swimming crab, Portunus pelagicus (Linnaeus, 1758): Effects on survival, digestive enzyme activities and water quality

Portunus pelagicus larvae in hatcheries experience high mortality during the early stages of development, primarily due to bacterial infections. A study was performed to determine the effectiveness of the indigenous probiotic Lactobacillus plantarum as a water additive in P. pelagicus larviculture. Three treatments and the control were tested in triplicate. The treatments consisted of three levels of L. plantarum were added daily at designated concentrations 1.0 x 10(6) (T-1), 5.0 x 10(6) (T-2) and 1.0 x 10(7) cfu ml(-1) (T-3) and control without any probiotic. The addition of the probiotic significantly enhanced (p < 0.05) survival rate of crab larvae for all treatments over the control. L. plantarum population (cfu ml(-1)) progressively increased (p < 0.05) in treated tanks over the time. Total bacteria and Vibrio counts found significantly lower (p < 0.05) in treated tanks over the control. The addition of L. plantarum influenced the nitrogen content and pH of culture water. Supplementation of L. plantarum significantly increased (p < 0.05) the protease and amylase activities in the treated groups over the control. The significantly highest protease activity was observed in T-2; while the amylase activity was higher in T-2 and T-3. The increased concentration of probiotic level (1 x 10(7)) did not increase the enzyme activities and survival of larvae. These results signify that L. plantarum addition at 5.0 x 10(6) cfu ml(-1) can effectively enhance the larval survival rate, enzyme activity and improve the water quality of P. pelagicus larviculture. (C) 2013 Elsevier B. V. All rights reserved.