Meeting Abstract
Many fishes can recruit the axial musculature for both swimming and suction feeding, yet little is known about how this dual-function muscle operates under the distinct mechanical demands of these behaviors (lateral versus dorsal axial flexion). Using electromyography and sonomicrometry, we measured muscle activity and strain for suction feeding and burst swimming in three dorsoventral epaxial regions in a bluegill sunfish. Sunfish consistently activated the dorsalmost epaxial region for low- and high-performance strikes and added activation of the middle and ventral regions for high-performance strikes on live prey. By contrast, sunfish always activated all three epaxial regions for fast-starts. Our results suggest that sunfish use recruitment patterns similar to largemouth bass, where they increase performance for suction feeding by activating the epaxial muscle from dorsal to ventral, and in the case of swimming, from ventral to dorsal. We also found that longitudinal strain varied with respect to distance from the vertebral column, as predicted by beam theory. Strains for fast-starts were highest in the lateral region and lowest in the medial region, while strains for suction feeding were highest in the dorsal region and lowest in the ventral region for suction feeding. Our EMG data suggest that sunfish vary regional muscle recruitment for modifying swimming and suction feeding performance. Our strain data suggest that the different modes of axial bending used for feeding and swimming behaviors create distinct strain gradients. Future studies examining the relationship between longitudinal strain and muscle fiber strain are needed to quantify regional differences in power output for swimming and suction feeding.
