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Fish typically use a rostro-caudal wave of head expansion to generate suction, which is assumed to cause a uni-directional, anterior-to-posterior flow of water in the expanding head. However, compared with typical fish,syngnathid fishes have a remarkably different morphology (elongated snout,small hyoid, immobile pectoral girdle) and feeding strategy (pivot feeding:bringing the small mouth rapidly close to the prey by neurocranial dorsorotation). As a result, it is unclear how suction is generated in Syngnathidae. In this study, lateral and ventral expansions of the head were quantified in Hippocampus reidi and linked to the kinematics of the mouth, hyoid and neurocranium. In addition, the flow velocities inside the bucco-pharyngeal cavity and in front of the mouth were calculated. Our data suggest that the volume changes caused by lateral expansion are dominant over ventral expansion. Maximum gape …