Integration of Undulatory Swimming Kinematics and Ram Suspension Feeding in A Model American Paddlefish

Ram suspension-feeding fishes are a taxonomically diverse group that is both economically and ecologically important. However, many questions remain pertaining to how they feed, including the types of prey they are capable of capturing, the metabolic costs associated with feeding, and the process of manipulating and transporting food around the oral cavity. Recent research has shown that the American paddlefish (Polyodon spathula) employs vortical cross-step filtration, which includes crossflow filtration processes that are organized into a spatial structure across the gill rakers by the formation of vortices behind the branchial arches. Potential temporal organization of filtration mechanisms in ram suspension-feeding fish has not been studied previously. Because ram suspension feeders swim forward with their mouths open to capture prey, we investigated the effect of the locomotory kinematics associated with undulatory swimming on intra-oral flow patterns and food particle transport. We constructed a mechanized model to simulate the swimming of suspension-feeding paddlefish, and recorded fluctuations of flow speed and pressure within the model. We also showed that swimming kinematics aided the transport of food particles from the gill rakers to the posterior margins of the gill slots. These findings suggest strong integration between locomotor and feeding systems in ram suspension-feeding fishes.