Growth, metabolism and immune responses to evisceration and the regeneration of viscera in sea cucumber, Apostichopus japonicus

Growth, metabolism and immune responses of sea cucumber, Apostichopus japonicus, following evisceration induced artificially, were investigated in this study. The body weight, specific growth rate (SGR), oxygen consumption rate (OCR), activities of immunoenzymes including acidic phosphatase (ACP), alkaline phosphatase (AKP) from hydrolytic system, and catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and malonyl-dialdehyde (MDA) from antioxidant system in muscle, intestine and respiratory tree were measured to evaluate the physiological responses of A. japonicus to evisceration and regeneration of viscera. The results showed that body weight of sea cucumber significantly dropped following evisceration and then increased gradually with digestive function resumed. Accelerated growth rates were observed in the regeneration group from the 10th day to 20th day, but there was no significant difference between the regeneration group and control group at the end of the experiment. OCR reduced rapidly after evisceration and increased gradually afterwards. Compared to the control, no significant difference in OCR was found on the 45th day (P > 0.05). The immune responses of A. japonicus were highly tissue-specific during the regeneration of viscera. Both ACP and AKP activities in muscle peaked on the 10th day after evisceration, then decreased gradually to normal on the 45th day (P > 0.05), while those in the regenerated tissues exhibited a differential rising trend from the 20th day after evisceration. SOD activity in muscle was not significantly influenced by evisceration; however, in the regenerated tissues it was enhanced and significantly higher than those in the control on the 45th day (P < 0.01). CAT activity in muscle of the regeneration group was significantly higher than in the control during the experiment (P < 0.05). Comparatively, CAT activity in the respiration tree increased invariably after evisceration, while in the intestine CAT activity was not significantly affected by evisceration (P > 0.05). Significant increase was found in both T-AOC and MDA in all three tissues after evisceration (P < 0.05); however, they all returned to normal at the end of the experiment. Results of this study indicated that growth, metabolism and immune responses including hydrolytic and antioxidant enzymes in sea cucumber were significantly influenced by evisceration. Although the regeneration group did not catch up with the control in body weight, SGR, OCR, major non-specific immune parameters resumed to normal level within 45 days after evisceration, indicating that A. japonicus might have recovered physiologically from evisceration. Results from this study first presented comprehensive and valuable data of physiological responses to evisceration and the regeneration of viscera in A. japonicus, which would have important implications for those farmers engaged in sea cucumber culture.

► Evisceration influenced growth, metabolism and immune responses in sea cucumber.
► Immune responses in sea cucumber were tissue-specific during regeneration.
► Sea cucumber recovered physiologically within 45 days after evisceration.