Biomechanics, Evolution, and Modulation of Suction Feeding Mechanisms in Fishes

Numerous jawed vertebrate species use suction feeding to capture evasive prey by rapidly expanding the skull and pulling water into the mouth. Many biomechanical mechanisms specific to this behavior are unknown, and how this behavior has evolved through time is still under investigation. In this thesis I quantify cranial kinematics for two non-teleost actinopterygian taxa using X-Ray Reconstruction of Moving Morphology (XROMM), exploring how mobile skeletal elements may drive suction feeding success. Furthermore, I compare the contribution of each cranial bone to changes in oral cavity volume across four species spanning the gnathostome phylogeny. In chapter 1 I introduce the field of suction feeding biomechanics, providing morphological and phylogenetic context for the subsequent chapters, and set up specific questions that are addressed in this thesis. In chapter 2 I describe the cranial kinesis employed during suction feeding by Polypterus bichir, a member of the earliest branching actinopterygian clade. I quantify the precise 3D motions of the ceratohyal and find that these motions are strongly associated with prey motion and the peak rate of volume expansion during suction strikes. I describe and employ a new method of quantifying the relative contribution of individual bones to volume change (RCVC) during suction feeding strikes. I also explore the mechanics of jaw opening in P. bichir, including the role of the sternohyoideus muscle in depressing the hyoid during suction feeding. In chapter 3 I quantify the suction feeding kinematics of Amia calva feeding on both evasive and non-evasive prey, finding that strikes on evasive feeder fish are statistically distinct from those on worms. This chapter provides another dataset for understanding the variability and modulation of suction feeding strikes in fishes. I further explore the role of the sternohyoideus muscle in depressing the hyoid and generating force for suction feeding in A. calva. In chapter 4 I measure the RCVC (relative contribution to volume change) during suction feeding across four species: P. bichir, A. calva, Protopertus annectens, and Chitala blanci. These species span the gnathostome phylogeny and have distinct morphologies. Our analysis reveals variation in which bones drive volume change during suction feeding. In chapter 5 I provide a summary of the findings and impacts of this dissertation and lay out several future directions for study to expand upon this work