Crevices increase feeding behavior, crawling behavior and glucose level of stressed sea cucumbers (Apostichopus japonicus)

Sea cucumbers seek refuge to crevices in adverse environments. However, the mechanism by which crevices mitigate the adverse impacts of stress on sea cucumbers remains totally unknown. The present study investigated the detrimental effects of mechanical perturbation on behavior and physiology of sea cucumbers (Apostichopus japonicus). We subjected sea cucumbers to mechanical perturbation by placing them in a sieve submerged in water and stirring the sieve parallel to the water surface to simulate common mechanical perturbation in seed production. We found that mechanical perturbation significantly reduced cortisol, glucose, crawling frequency, and feeding duration of A. japonicus. These results suggest that mechanical perturbation decreases cortisol and glucose levels, potentially impacting feeding and crawling behaviors of A. japonicus.

This study further investigated how crevices mitigated the negative effects of mechanical perturbation. There was a significant increase in the residence time of A. japonicus within crevices, while A. japonicus without crevices exhibited significantly increased movement distances after mechanical perturbation. These results indicate a preference among A. japonicus for inhabiting crevices or actively seeking such habitats following mechanical perturbation. Following mechanical perturbation, A. japonicus exhibited a significantly decrease in feeding time and crawling frequency compared to those that had been inhabiting crevices for 7 h. Sea cucumbers in the crevice showed a significantly higher crawling frequency after being exposed to 7 h of mechanical perturbation, compared to the individuals not in the crevice. These results indicate that crevices serve as an efficacious mechanism for ameliorating the negative impacts of mechanical perturbation on sea cucumber behaviors. Further, the glucose level increased significantly with the increase of time in the crevice in sea cucumbers subjected to mechanical perturbation.

In summary, crevices attenuate the deleterious impacts of mechanical perturbation on sea cucumbers by enhancing glucose level, crawling, and feeding behaviors, thereby probably promoting the production efficiency in aquaculture of A. japonicus. The study elucidates the mechanism by which crevices alleviate stress in A. japonicus, providing valuable insights into the seed production.