Crevice is beneficial to fitness-related behaviors of small sea cucumbers Apostichopus japonicus exposed to handling stress

Sea cucumbers naturally prefer to inhabit crevices. Although this biological characteristic is widely used in sea cucumber aquaculture, the benefits of crevices remain largely unknown. The present study found that feeding and defecation rates significantly increased in sea cucumbers in the crevices for 24 h. After leaving the crevice, tentacle activity time of sea cucumbers in the experimental group was significantly more than that of those in the control group. Further, the present study found that sea cucumbers cultured in crevices for 21 days showed significantly longer adhesion time and tentacles activity time after air exposure and mechanical perturbation. Righting time of sea cucumbers cultured in crevices was significantly less than that in the control group after air exposure. In conclusion, the present study clarifies that crevice is beneficial to fitness-related behaviors of small A. japonicus. We consequently encourage aqua-farmers to increase the number of crevices in both pond culture and seed production, which is conducive to improve the feeding, defecation, adhesion, and righting behaviors of sea cucumbers.