| The functional interpretation of cranial morphology in teleost fish and other suction feeders has been limited by an incomplete understanding of the musculoskeletal basis of suction feeding performance. In this dissertation research, I used biomechanical modeling and invasive experimentation to address this issue. In Chapter 1 activation and strain were measured in the sternohyoideus of five largemouth bass (Micropterus salmoides) to understand how this muscle functions during feeding. The stemohyoideus contracted at strain rates (2--4 fascicle lengths s-1) that indicate it functions to produce mechanical power. In Chapter 2 a model of force transmission in the teleost head was developed, by balancing the stress produced by the epaxial muscle mass with the subambient pressure in the oral cavity generated during feeding. Subambient oral pressure is thought to be a partial metric of suction feeding performance in fish. The model was tested by correlating measured pressure during maximal effort with a morphologically based estimate of pressure generating potential for each individual. The model significantly explained variation in pressure among 45 individuals from five species of centrarchid fishes (M. salmoides, Pomoxis nigromaculatus, Lepomis punctatus, Lepomis microlophus, and Lepomis macrochirus). Furthermore, the mean estimated muscle stress across individuals (68.5 kPa) was similar to that expected for muscle contracting to produce power. In Chapter 3, muscle power production was measured in the epaxial muscle mass of four largemouth bass. Muscle strain was measured directly with sonomicrometry and muscle stress was estimated using the model described in Chapter 2. Buccal volume and muscle activation were also measured. The epaxials shortened in all strikes to produce power, and maximal levels of power production varied from 17 to 137 kPa across all fish. Levels of power production were significantly correlated with EMG rectified area and the estimated power required for cranial expansion. The slope of the latter relationship (∼1) indicates that the epaxial muscle mass are the predominant actuator of suction feeding kinematics in largemouth bass. Taken together, this dissertation research provides the theoretical, experimental, and technical foundation for a detailed, deterministic, and general model of the musculoskeletal basis of suction feeding performance. |
