3. Results
3.1. Feeding behavior
The frame-by-frame analysis of the video footage revealed that sea cucumbers of different sizes used similar strategy in feeding. Each tentacle contained several tree-like branches, and each branch comprised more sub-branches. The number and size of the tentacle branches increased with sea cucumber growth (Fig. 2). The feeding process involved several continuously coordinated movements. Some of the tentacles were outstretched from the oral crown during feeding and moved towards the sediment particles. As the tentacle approached the sediment surface, each branch was stretched outwards to maximize the available surface coverage for feeding. The tentacles spread out and collected sediment with a grasping motion. Once the tentacle had grasped a certain number of particles, it would retract inward. The tentacle was then inserted into the mouth and the food particles were rubbed onto the oral crown by the oral muscle and other tentacles (Fig. 3). The same action was repeated continuously during the sea cucumber feeding period