Meeting Abstract
68.4 Tuesday, Jan. 6 XROMM analysis of 3D skeletal movement during premaxillary protrusion in common carp GIDMARK, NJ*; STAAB, KL; HERNANDEZ, JP; BRAINERD, EL; Brown University; George Washington University; George Washington University; Brown University nicholas_gidmark@brown.edu
Multiple mechanisms have evolved in fishes for premaxillary protrusion, each resulting in suction, gape, and/or speed benefits during feeding. A novel, midline sesamoid bone, the kinethmoid, is present in cypriniform fishes and is highly mobile during jaw protrusion. The kinethmoid is suspended in a ligamentous sling between the neurocranium and the premaxilla, and is also ligamentously attached to the maxillae and palatines. Historically, jaw movements have been characterized by either speculations from dead specimens or by using external landmarks of live specimens. We used X-ray Reconstruction of Moving Morphology (XROMM) to visualize and measure 3D bone kinematics during oral jaw protrusion in common carp, Cyprinus carpio. Using biplanar x-ray video and laser-scanned bone data in a digital animation framework, XROMM produces accurate (0.1 mm) 3D animations of bone models, and can be used to explore movements and extract quantitative kinematic data. XROMM analysis of common carp collecting food from the bottom of an aquarium shows that the kinethmoid rotates in the sagittal plane, with the dorsal end rotating anteriorly, effecting premaxillary protrusion. Kinethmoid rotation is driven by the maxillae rotating slightly about their long axes, translating ventrally, and rotating in a parasagittal plane. The movements of the maxillae are caused in part by lower jaw rotation, and are consistent with previously hypothesized action of the A1 beta muscle. Lower jaw and maxillary rotation occurs prior to ventral translation of the maxilla and rotation of the kinethmoid. Protrusion of the premaxilla occurs over the entire duration, and is followed by lateral buccal expansion. This is the first description of cypriniform jaw bone kinematics in 3D space.
