Immune responses and disease resistance of the juvenile sea cucumber Apostichopus japonicus induced by Metschnikowia sp. C14

Metschnikowia sp. C14 was isolated from the intestine of sea cucumber Apostichopus japonicus. It inhibited the growth of the pathogenic Shewanella marisflavi AP629 and Vibrio splendidus NB13 of A. japonicus in vitro. The yeast was added to basal diet at 104, 105 and 106 CFU g− 1 of feed to evaluate its effects on immune response and disease resistance against V. splendidus infection in juvenile sea cucumber A. japonicus. After feeding for 30 days and 45 days, five sea cucumbers from each tank were sampled for immunological analyses. Results indicated that C14 significantly improved the phagocytic activity in coelomocytes of sea cucumbers (P < 0.05). Moreover, C14 administration significantly elevated lysozyme (LSZ), phenoloxidase activity (PO), total nitric oxide synthase (T-NOS), superoxide dismutase (SOD), alkaline phosphatase (AKP) in coelomic fluid, and LSZ, T-NOS, SOD and acid phosphatase (ACP) activities in CLS of sea cucumbers (P < 0.05). After feeding for 45 days, ten sea cucumbers from each dose group were challenged with V. splendidus NB13. Cumulative incidence and mortality of sea cucumbers fed with C14 were found to be lower than those of control group. The present results show that diet supplemented with C14 stimulates the immune system of juvenile A. japonicus thus enhancing their resistance against V. splendidus. C14 enhanced the immune responses and disease resistance of sea cucumbers.