Differences in immune function and metabolites between aestivating and non-aestivating Apostichopus japonicus

• We compared the physiology of non-aestivation group and aestivation group of A. japonicus during the aestivation period.
• The antioxidant and metabolic enzyme activities were both higher in non-aestivation group than those in aestivation group.
• Non-aestivation group had a greater variety of metabolites than those in aestivation group of A. japonicus.
• Non-aestivation group had stronger thermostable performance than aestivation group of A. japonicus.

With water temperature increasing in summer, large-sized sea cucumbers (Apostichopus japonicus) generally enter aestivation, while there still occurs a small portion of individuals that do not enter aestivation and remain active and ingesting. In this study we investigated the differences in immuno- and metabolic enzyme activities and metabolites between non-aestivating and aestivating groups of A. japonicus. Animals (wet weight > 150 g) were collected from July to October in a seawater pond, north China. The individuals that voided feces, or had intestine contents after dissection, were defined as non-aestivating group, whereas those without feces or intestine contents were defined as aestivating group. Relative intestine mass (RIM), immuno-enzyme activities (SOD, CAT, T-AOC) and metabolic enzyme activities (PK, HK, MDH, LDH) of the body wall, and metabolites in intestine in both groups were determined. Results showed that temperature had significant effects on RIM and all enzyme activities in the non-aestivating group (P < 0.05). However, the significant effects of temperature on the T-AOC, PK and LDH activities were not found in the aestivating group (P > 0.05). Meanwhile, the RIM and all enzyme activities in the non-aestivating group were significantly higher than those in the aestivating group before September 10. The metabolites including glutamate, 3-aminoisobutyrate, aspartate, choline, phosphocholine, and taurine were abundant in the aestivating group, whereas 12 kinds of amino acids, glucose, glycogen, dimethylamine, inosine, and homarine were abundant in the non-aestivating group. It was obvious that metabolism of the non-aestivating group was more active than that of the aestivating group. This study provided new insights for understanding the differences in intestine degradation, enzyme activities and metabolites between non-aestivating and aestivating A. japonicus under high temperature in summer. Meanwhile, the results might be helpful for high temperature resistant sea cucumber selection in aquaculture.Statement of relevanceWe state that the work has not been published and is not being considered for published elsewhere.