A deposit-feeder sea cucumber also ingests suspended particles through the mouth

Although the sea cucumber Apostichopus japonicus has been characterised as a deposit feeder, nutrients sourced from the water column have been recorded in the intestines of this species. However, the mechanisms whereby nutrients in the water enter the intestinal tract of A. japonicus, and whether other suspended particles can be ingested via the mouth of A. japonicus adults, remain unknown. Here, we reveal how A. japonicus ingests suspended particles through the mouth. We used synthetic particles and video recording to confirm the suspension uptake by the sea cucumber. A. japonicus continued to ingest suspended particles (if present) over time, and the particle-ingestion rate was positively correlated with the concentration of suspended particles (Pearson correlation: r=0.808). Additionally, clearance rates of the suspended particles ranged from 0.3–0.9 L−1 h−1. The findings of this study thus provide evidence of a previously undescribed particle uptake mechanism in a commercially important species.