Determining the source of muscle power for suction feeding in ray-finned fishes

Brown University, Providence RI

Investigators

Abstract

Most fish capture food by sucking it into their mouths, and successful suction feeding is both fast and forceful. Speed and force combined require high power from muscles, but where does all of that muscle power come from? Fish head muscles are small, but the body muscles are large. Do fish transfer power from their bodies to their heads, similar to the way baseball pitchers transfer power from their legs and core to their throwing arms? Recent developments in 3D X-ray imaging have made it possible to measure power directly, and this project will use the new technology, XROMM (X-ray Reconstruction of Moving Morphology), to study fish with diverse body forms and feeding habits. The significance of this research is a new framework for understanding the structure and function of body and head muscles in 30,000 species of fish (half of all vertebrate species), and the results will impact ongoing research in numerous labs worldwide studying the biomechanics, ecology and evolution of suction feeding. This project will engage children from the Providence RI public schools in an after-school Marine Biology Science Camp, providing an opportunity to do fun science projects with students from groups traditionally underrepresented in the sciences. This project will develop a new technology, VROMM (Video Reconstruction of Moving Morphology), with similar capabilities as XROMM but with video cameras instead of expensive X-ray machines. VROMM will accelerate research by making the technology more widely available and advance US economic competiveness through technological innovation. A recent study of largemouth bass showed that axial muscles provide more than 95% of the power for high-performance suction feeding, but these results so far come from just one species. Might axial muscles be the main source of suction power in most fishes? The goal of this project is to measure the power capacity of cranial and axial musculature relative to the power required for suction feeding in six species of fishes with different body forms and distant phylogenetic relationships to largemouth bass. XROMM combined with the dynamic endocast method will be used to measure instantaneous rate of buccal volume change, and a pressure transducer will be used to measure buccal pressure. Pressure multiplied by the rate of volume change will yield instantaneous suction power. Optimal muscle power capacity (Popt) will be calculated from muscle mass and the maximum power produced by fish muscle, which assumes shortening at the optimal velocity. Actual muscle velocity will be measured with XROMM and fluoromicrometry, and velocity-corrected power capacity (Pvc) calculated. The Pvc for cranial and axial muscles will be compared to the power required for suction feeding to determine the maximum power that cranial muscles can contribute, and therefore the minimum power that axial muscles must be contributing. These results may provide a new framework for studying suction feeding, in which the anatomy, biomechanics, and evolution of the axial musculoskeletal system should be studied as the power source for feeding, or at least as compromises between the needs of swimming and feeding.