Meeting Abstract

82.4  Sunday, Jan. 6  An examination of the feeding behavior, cirral anatomy, and cirral fan leakiness of Balanus glandula, comparing three size classes spanning the range from post-metamorphic juvenile to the adult GEIERMAN, Christina; Oregon Institute of Marine Biology cgeierma@uoregon.edu

The acorn barnacle Balanus glandula can increase its diameter by a factor of twenty as it grows from a recruit to an adult. This study examines how the cirral morphology, feeding behavior at a low current speed, and leakiness of the cirri as calculated by a geometric model differ between three size classes. The three size classes examined were newly-settled juveniles (small, aperture diameter 0.36mm), the largest individuals found locally (large, aperture diameter 6.5mm), and an intermediate size (medium, aperture diameter 3.4mm). The barnacles were taped while feeding in a flow tank at a current speed of 4cm/s. Molts were collected and several morphometric and meristic traits were measured. Large individuals spent more time actively feeding (ANOVA, Tukeys p=0.001) and had fewer setae per millimeter on cirrus VI (ANOVA, Tukeys p<0.0001) than did medium or small individuals. Small individuals were observed passively feeding, while this feeding strategy was not observed in the larger groups. This may be due to the fact that smaller individuals are more likely to feed within the boundary layer and experience slower flow speeds. Also, the cirri of the small individuals operate a Reynolds numbers less than one, while the larger size classes operate at Reynolds numbers greater than one. In addition, barnacles were videotaped actively feeding while a stream of milk was aimed at their cirri. A geometric model of leakiness was generated from the observed billows. Trends in leakiness will be discussed.