Feeding Behavior Reveals the Adaptive Nature of Plasticity in Barnacle Feeding Limbs

TitleFeeding Behavior Reveals the Adaptive Nature of Plasticity in Barnacle Feeding Limbs
Publication TypeJournal Article
Year of Publication2007
AuthorsMarchinko, K. B.
JournalBiological Bulletin

Barnacle feeding limbs are extremely plastic in response to spatial and temporal differences in wave exposure: individuals have long, thin feeding limbs in habitats with little wave action, and short, thick feeding limbs in wave-exposed habitats. This difference in feeding limb morphology is assumed to be adaptive. Individuals with shorter limbs may have the ability to feed in breaking waves because their limbs are better suited to withstanding drag forces than are those of individuals with longer feeding limbs. I tested this hypothesis by observing the feeding behavior of two populations of Balanus glandula (one from a protected shore and one from a wave-exposed shore) subjected to five different water velocities. Differences between populations in the ability to feed with the cirral net fully extended were highly significant. The wave-exposed population fed with the cirral net fully extended at all velocities tested (up to 49 cm/s), whereas full cirral extension ceased between 7.25 and 21.4 cm/s in all individuals from the protected-shore population. Clearly, barnacles possessing long, thin feeding limbs experience a strong disadvantage when feeding in faster flowing water, confirming earlier hypotheses that differences in feeding limb length between protected and wave-exposed shores are adaptive.