Growth performance, immune response, and disease resistance against Vibrio splendidus infection in juvenile sea cucumber Apostichopus japonicus fed a supplementary diet of the potential probiotic Paracoccus marcusii DB11

• P. marcusii DB11 in diets enhanced the growth and immunity of A. japonicus.
• Immune responses of A. japonicus to DB11 in diets were highly tissue specific.
• The coelomic fluid showed the most intensive immune response in A. japonicus.
• 108 CFU g− 1 DB11 was suggested for growth and immunity enhancement in A. japonicus.

The present study assessed the growth performance, immune response, and disease resistance against Vibrio splendidus infection in the juvenile sea cucumber Apostichopus japonicus by using a potential probiotic Paracoccus marcusii DB11. Fresh bacterial cells of DB11 were added to sea cucumber basal feed at doses of 0, 1 × 104, 1 × 106, and 1 × 108 CFU g− 1 of diet (Control, PM4, PM6, and PM8, respectively) and were administered orally to A. japonicus for 60 d. At the end of the growth trial, 20 sea cucumbers from each treatment were challenged using V. splendidus. The results showed that A. japonicus fed the probiotic exhibited significantly better growth performance when compared to that by the control (P < 0.05). The immune response in A. japonicus to supplemental DB11 was highly tissue specific and dose dependent. All immune parameters, including superoxide dismutase (SOD), catalase (CAT), lysozyme (LSZ), acid phosphatase (ACP), and alkaline phosphatase (ALP), were significantly enhanced in the coelomic fluid of A. japonicus fed DB11 at 1 × 108 CFU g− 1 of diet (P < 0.05). However, no significant effect was observed in the body wall of A. japonicus (P > 0.05). Comparatively, significantly increased SOD, CAT, and ACP activities and decreased LSZ activity were observed in the respiratory tree of A. japonicus fed DB11 at 1 × 108 CFU g− 1 (P < 0.05). LSZ and ALP activities in the intestine significantly improved, and SOD activity significantly decreased at 1 × 108 CFU g− 1 of DB11 in the diet (P < 0.05). The cumulative incidence and mortality after the V. splendidus challenge significantly decreased in sea cucumbers fed DB11 at 1 × 108 CFU g− 1 when compared to that in the control. The present results show that a diet supplemented with DB11 stimulated the immune system of juvenile A. japonicus, thus, enhancing their resistance against V. splendidus, which confirmed the potential beneficial effects of P. marcusii DB11 as a dietary probiotic in juvenile A. japonicus.