TRANSMISSION OF FORCE AND VELOCITY IN THE FEEDING MECHANISMS OF LABRID FISHES (TELEOSTEI, PERCIFORMES)

The feeding mechanisms of four species of the teleostean family Labrid ae (Cheilinus fasciatus, C. trilobatus, Oxycheilinus bimaculatus, and O. unifasciatus) were modeled using four-bar linkage theory from mecha nical engineering. The predictions of four-bar linkage models regardin g the kinematics of feeding were compared to the movements observed wi th high speed cinematography (200 frames/s). A four-bar linkage was an accurate model of the mechanism by which upper jaw protrusion, maxill ary rotation, and gape increase occur in each species. A four-bar mech anism of hyoid depression was an accurate predictor of hyoid depressio n when simultaneous cranial elevation and sternohyoideus contraction w ere simulated. Morphometrics of the linkage systems of the jaws and hy oid were collected for 12 labrid species. These data were used to calc ulate the transmission of force and motion through the musculoskeletal linkages. Several measures of mechanical advantage and displacement a dvantage were compared, including both traditional lever ratios and tr ansmission coefficients of four-bar linkages. Alternative designs of t he feeding mechanisms maximize force or velocity for the capture of di fferent prey types. High velocity transmission of both the jaw and hyo id systems is characteristic of those species that feed on evasive pre y, whereas species that feed on benthic invertebrates favor increased force transmission in both systems. Quantitative models of biomechanic al systems supply criteria for functionally relevant morphometrics, an d aid in calculating the capacity for transmission of force and veloci ty in musculoskeletal systems.