The feeding behavior and digestive physiology 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.
In this article the tentacle locomotion, feeding rhythms, ingestion rate (IR), feces production rate (FPR) and
digestive enzyme activitieswere 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 b 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 b 0.05). Additionally, the peak activities of digestive enzymes were 2–4 h earlier
than the peak of feeding. Taken together, these results demonstrated that the light/dark cyclewas a powerful environment
factor that influenced biological rhythms of A. japonicus, which had the ability to optimize the digestive
processes for a forthcoming ingestion.
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