Effects of artificial shelter on feeding, digestion, and growth of the sea cucumber Apostichopus japonicus

Shelters are widely used in sea cucumber aquaculture. But the long-term effects of shelters on behavior and physiology are unknown in sea cucumber aquaculture. In this research, the number of grasping of the sea cucumber mouth tentacle significantly increased in the experimental group (group Y) compared with the control group (group C) (P = 0.003), indicating that the shelter increases the feeding rate of sea cucumbers. The height of the intestinal crease in group Y was significantly higher than that in group C (P < 0.001), and the proportion of Patescibacteria in the intestine significantly increased. However, there was no significant difference in digestive enzyme activities, and the defecation rate of Apostichopus japonicus in group Y was significantly lower than that in group C (P = 0.047). This suggests that the shelter probably improves the digestive capacity of sea cucumbers by altering their gut microbial composition and gut structure. In addition, final body weight (P = 0.006) and daily gain (P = 0.008) in group Y were significantly higher than those in group C. This indicates that the shelter improves the growth efficiency of sea cucumbers. The present study reveals that long-term use of shelter greatly improves feeding behavior, defecation behavior, gut microbiota composition, gut structure, and growth of A. japonicus. In summary, the shelter improves the behavior and physiological activities of sea cucumbers, and consequently increases the aquaculture efficiency.