Meeting Abstract
Many ray-finned fishes use their large body muscles to help power mouth cavity expansion during suction feeding. The dorsal (epaxial) body muscles can power expansion by shortening to elevate the cranium, and the ventral (hypaxial) body muscles by shortening to retract the pectoral girdle. While epaxial-powered cranial elevation has received much more study, in some species (including catfishes) it appears to be absent. Can these fish generate powerful suction expansion with the hypaxials alone, or are they limited to low-power feeding or a greater reliance on cranial muscle power? We measured 3D skeletal kinematics and axial muscle shortening using X-ray Reconstruction of Moving Morphology (XROMM) and fluoromicrometry, respectively, during suction feeding in channel catfish. The rate of mouth volume expansion was calculated from the XROMM animations using a dynamic digital endocast, and combined with intraoral pressure recordings to estimate suction expansion power. Catfish generated powerful strikes (10-12 W, similar to peak powers of largemouth bass and bluegill sunfish), without epaxial power. During suction expansion, the epaxials shortened minimally, and the cranium elevated less than 5 degrees relative to the body. The hypaxials shortened substantially (10% strain) to retract the pectoral girdle by about 12 degrees relative to the body. Some cranial muscles also shortened, but were too small to contribute meaningful power to mouth expansion. The hypaxials alone were capable of powering these strikes without exceeding 90 W/kg, a relatively low power output. Thus, powerful suction feeding doesn’t require epaxial-powered cranial elevation, and the contribution of dorsal and ventral body muscles to suction power clearly varies across fishes.
