Meeting Abstract

P2.130  Jan. 5   Influence of orientation and flow speed on feeding behavior and metabolism of the barnacle Semibalanus balanoides LAKE, B.*; JOHNSON, A.S.; MAUCK, R.A.; Bowdoin College; Bowdoin College; Kenyon College blake@bowdoin.edu

In areas of unidirectional flow intertidal barnacles settle oriented facing upstream within 90 degrees of the flow direction. Optimal foraging theory predicts that this favored orientation may enable greater feeding efficiency in terms of higher food yield, lower energy expenditure or both. To examine changes in feeding behavior and metabolism, solitary barnacles were collected and maintained on a tidal flat off Kent Island, NB, Canada during the summer. During testing, barnacles were oriented within a liquid-phase respiration chamber such that the feeding cirri were either: (1) Closing Against the Current (CAC), (2) Closing With the Current (CWC) or (3) Closing Perpendicular to the Current (CPC). Their feeding behavior and oxygen consumption were monitored at each orientation at two current speeds. Preliminary data analysis revealed no significant differences in beat rate or duration between the three orientations at either current speed. In faster flow the barnacles fed more actively, sweeping their cirri at significantly higher rates and shorter beat durations in all orientations. In slower flow metabolic rate was significantly higher when barnacles were oriented against the current (CAC) relative to the two other orientations. These data suggest that at low flow speeds the CAC orientation requires higher energy expenditure relative to the other orientations. We speculate that this trade-off compensates for greater metabolic costs via increased food collection.