EFFECTS OF FLOW ON THE BEHAVIOR OF THE SOUTHERN OYSTER DRILL STRAMONITA HAEMASTOMA IN RESPONSE TO EXUDATES FROM OYSTERS AND OYSTER REEF FAUNA

摘要

Stramonita haemastoma, the southern oyster drill, is a predatory gastropod that locates prey using waterborne chemical cues. These cues move by advection and are subjected to hydrodynamic forces such as turbulence, which can have significant effects on both the delivery of cues and on the efficiency and success of organisms that use chemical cues to find prey. We investigated how flow velocity and turbulence would affect oyster drill foraging behavior in a laboratory flume, and found that oyster drills would move upstream toward exudates from fouled oyster clumps but not toward seawater controls. We then measured foraging behavior in a range of flow conditions and did not find significant differences in either foraging success or efficiency among the flow treatments. We also found that a significant number of oyster drills would continue to mow upstream even if cue delivery was stopped midway through the trial. Oyster drills placed their siphon near the sediment when oyster reef exudates were delivered through the sediment, and in turbulent flows when greater momentum delivered cues to the sediment. In all flow treatments, oyster drills spent similar to 2.5 min motionless before proceeding upstream. Based on these observations, we posit that when first detecting an attractive cue, oyster drills evaluate the cue and flow direction using cues in the sediment and water column before making a decision to move upstream. While moving toward an attractive cue source, oyster drills will continue to move upstream even when the attractive cues are no longer being released, which allows them to find oyster reef habitats successfully in a range of flow conditions.