Meeting Abstract
Swimming and suction feeding involve remarkably different motions, yet many fishes use their epaxial musculature for both. Are different regions of the musculature specialized for locomotion and feeding, or this entire muscle bifunctional? Using electromyography (EMG) on three largemouth bass, we measured electrical activity in nine regions of the epaxial musculature and identified which regions contribute to low- and high-performance swimming and suction feeding. For all feeding strikes, bass consistently activated the dorsalmost region of the epaxial muscle—the dorsal pointing arm (DPA). Only high-performance strikes (strongest buccal pressures) consistently activated the more ventral muscle regions—the posterior- and anterior-pointing cones (PPC and APC). For all locomotor behaviors studied, bass consistently activated the ventralmost region of the epaxial muscle (APC). Only the highest-performance swimming behaviors (C-starts and sprints) consistently activated the more dorsal muscle regions (PPC, DPA). Thus, in the highest performance swimming and feeding behaviors, bass recruit muscle fibers from all regions of the epaxial musculature, whereas for lower performance behaviors, fibers are recruited preferentially from the dorsal region for feeding and ventral region for locomotion. Finally, we found that even the strongest goldfish strikes produced submaximal muscle activity relative to C-start intensities. These relatively low intensities suggest that, in largemouth bass, the epaxial muscles underperform in terms of power output during suction feeding. Future studies will reveal whether species that require higher muscle power outputs, such as bluegill sunfish, show a different pattern. These results inform our understanding of how axial muscles that originally evolved for swimming have been co-opted to power suction feeding.
