Evaluating the Opercular Linkage in Suction Feeding Fishes with Video Reconstruction of Moving Morphology (VROMM)

Abstract

Suction feeding in ray-finned fishes is a highly kinetic behavior. Musculoskeletal components are arranged in linkages, which move in complex, 3-dimensional ways. In order to precisely measure the 3-D rotations and translations of bones during suction feeding, we developed a new imaging method called Video Reconstruction of Moving Morphology (VROMM). VROMM combines bi-planar high speed video with 3-D mesh models to create highly precise animations of real-life motions. Using VROMM animations, we evaluated the opercular linkage for lower jaw depression by measuring the rotation of the lower jaw and the operculum at the quadratomandibular and operculohyomandibular joints, respectively. We filmed two species of sculpin, Leptocottus armatus and Hemilepidotus hemilepidotus, during suction feeding, and also filmed a post-mortem manipulation where we pulled straight up on the operculum to simulate the dorsal rotation described by the classic 4-bar linkage. In the manipulated trials, the measured kinetic transmission (KT) for Leptocottus and Hemilepidotus was 2.3 and 2.0 respectively. The measured KT for the live Leptocottus was 4.0, and, notably, the operculum reached maximum rotation significantly before the lower jaw. These data suggest that in Leptocottus, operculum rotation is responsible for initial jaw depression, while other linkages subsequently drive the rest of mouth opening.