MOVEMENT AND FEEDING BEHAVIOR AND PHYSIOLOGY OF SEA CUCUMBER Apostichopus japonicus  

The movement and feeding behavior of the sea cucumber, Apostichopus japonicus are not well understood. A better understanding may provide useful information for the development of the aquaculture of this species. Combining the advanced time-lapse photography technology with professional behavior-analysis software, the behavioral research system for A. japonicus has been conducted, and the movement and feeding behavior of A. japonicus have been systematically studied. The average movement speed of A. japonicas is around 1.6-3.4 cm/min, and the daily moving distance is around 20-50 m in the laboratory with normal condition. The influence of flow velocity on the motor behavior of the sea cucumber, A. japonicus was investigated. Sea cucumbers move in a downstream direction at faster current speeds. When there was no water flow, sea cucumbers tended to move in an irregular pattern. The tentacle locomotion, feeding rhythms, ingestion rate (IR), feces production rate (FPR) and digestive enzyme activities were studied in three size groups (small, mediumand large) of sea cucumber under a 12 h light/12 h dark cycle. Frame-by-frame video analysis revealed that all size groups had similar feeding strategies using a grasping motion to pick up sediment particles. The tentacle insertion rates of the large size group were significantly faster than those of the small and medium-sized groups (P＜0.05). Feeding activities investigated by charge coupled device cameras with infrared systems indicated that all size groups of sea cucumber were nocturnal and their feeding peaks occurred at 02:00-04:00. The medium and large-sized groups also had a second feeding peak during the day. Both IR and FPR in all groups were significantly higher at night than those during the daytime (P＜0.05). Additionally, the peak activities of digestive enzymes were 2-4 h earlier than the peak of feeding.