Effect of habitat cues on the swimming behavior of pre-competent Lacuna vincta larvae from Friday Harbor, WA, USA

Swimming behavior in planktonic larvae has been suggested to affect their dispersal and recruitment. Behavioral regulation of vertical distribution can affect the extent to which larvae may accumulate in or escape from vertically sheared flows or fronts. Competent larvae of many invertebrate species are known to respond to various settlement cues in the environment by regulating their behavior in order to facilitate settling in suitable habitats. The behavioral responses of pre-competent larvae to cues from the adult habitat could have implications for retention, however such responses have not been investigated. In this project we have studied the swimming behavior in pre-competent larvae from the gastropod Lacuna vincta in the laboratory with the objective of determining whether behavioral changes in response to potential settlement cues are present in larvae at that earlier developmental stage. Potential settlement cues included in this study are eelgrass (Zostera marina), the kelp Agarum fimbriatum, and adult L. vincta, in addition to a control of filtered seawater. Pre-competent L.vincta larvae were recorded swimming in water columns containing water in which these various cues had been soaked, and their behaviors were compared across treatments. Videos were analyzed for mean upward swimming speed, mean swimming speed along the path of travel, mean oscillatory speed, and mean axial speed for each treatment. For all metrics, there were no significant differences between all four treatments and the control. The sample size of larvae was consistently low in the kelp cue as larvae remained on the bottom of the column, possibly due to high viscosity of that cue water. Our results indicated no response to adult habitat cues when larvae are pre-competent