Meeting Abstract
78.5 Sunday, Jan. 6 Hyoid kinematics and hypaxial muscle strain during suction feeding in largemouth bass (Micropterus salmoides) CAMP, A.L.*; BRAINERD, E.L.; Brown University, Providence RI; Brown University, Providence RI ariel_camp@brown.edu
To capture food, suction feeding fishes use their kinetic skulls to rapidly expand the mouth cavity both laterally and dorsoventrally. Ventrally, mouth volume is increased by depression and retraction of the hyoid, but the muscular cause of this motion is unclear. This ventral expansion could be produced by the sternohyoid muscle, which attaches directly to the hyoid apparatus at the urohyal. If this is true, sternohyoid muscle shortening should equal urohyal retraction. The ventral body muscles, the hypaxials, could also retract the hyoid by rotating the cleithrum of the pectoral girdle, which is linked to the urohyal by the sternohyoid muscle. In this case, hypaxial muscle shortening should equal urohyal retraction. We tested these hypotheses by measuring urohyal and cleithrum kinematics, as well as sternohyoid and hypaxial muscle shortening, during suction strikes in 3 largemouth bass (Micropterus salmoides). Bone kinematics were measured relative to a body axis plane using X-ray Reconstruction of Moving Morphology. This technique combines bone models with motion recorded from bilateral x-ray video to create 3D animations of bone kinematics. Muscle shortening was measured with fluoromicrometry, which uses x-ray videos to measure distance changes between intramuscular markers. The urohyal moved both caudally (retraction) and ventrally (depression) relative to the body axis, and the cleithrum was retracted. Hypaxial muscle shortening was similar to urohyal retraction distance, with means of 6.2mm and 8.5mm, respectively, whereas mean sternohyoid muscle shortening was only 0.5mm. The hypaxial muscles generated hyoid depression, via cleithrum retraction, while the sternohyoid muscle acted like a ligament to transmit hypaxial shortening to the urohyal.
