Phenotypic and behavioral plasticity in the feeding of Balanus glandula

Abstract

Phenotypic plasticity is one mechanism by intertidal organisms to change and survive in a variety of local flow environments. One such species is the barnacle Balanus glandula, which exhibits plasticity in both its feeding behavior and the morphology of its feeding cirri. Barnacles feed actively at low flow speeds, but can feed passively at higher flow speeds. Additionally, individuals in habitually low flow environments have longer and thinner cirri than barnacles in high flow environments. This study explores how behavioral and morphological plasticity interact to give barnacles from low flow environments an advantage while feeding at slower water velocities. Using a flow tank to observe feeding behavior, barnacles were placed in flows ranging from 0 to 10 cm/sec. Barnacles from a low flow site employed passive feeding at lower water velocities than barnacles from a high flow site. Passive feeding, when possible, is thought to increase the energetic efficiency of feeding compared to active feeding. In slower water velocities, the increased ability to feed passively benefits low flow barnacles compared to high flow barnacles.