Meeting Abstract
Suction feeding is used by every group of aquatic vertebrates and is the primary mechanism of prey capture for most ray-finned fishes. Cranial mobility, or the process of rapidly expanding a mobile skull, is a crucial component of suction feeding. We studied evolution of cranial mobility in suction feeding fishes and compared to fishes that rely on biting. We recorded videos of prey capture by suction in 44 species, including 13 that normally feed by biting prey attached to the substrate. Kinematics of cranial motion were quantified by tracking the change in position of 18 landmarks on the head and body, which were used to generate variables describing components of motion, such as mandible rotation, upper jaw protrusion, and cranial rotation. We analyzed this dataset using a new multivariate, variable rate, state-dependent Brownian motion model of continuous character evolution to estimate rates of kinematic evolution. The diversity of cranial mobility among suction feeders was 10.2 times that of native biters, in association with a 2.4-fold higher rate of evolution of kinematics. Surprisingly, this difference in the rate of feeding motion diversification is not a simple consequence of variation in morphology, as we found that suction feeders have just 1.5 times the disparity in interspecific cranial morphology than biters. With lower rates of kinematic evolution, biters have convergently decreased cranial mobility and each of its components, indicating substantial anatomical and functional constraints on fishes that evolve biting feeding modes. We conclude that diversity in cranial mobility and high rates of kinematic evolution are characteristic of suction feeding and provide a link between feeding mode and the exceptional diversity of suction feeding vertebrates.
