Meeting Abstract

S9-1.1  Jan. 6  Feeding Mechanisms in Cartilaginous Fishes WILGA, C.D*; MOTTA, P.J.; SANFORD, C.P.; Univ. Rhode Island; Univ. South Florida; Hofstra Univ. cwilga@uri.edu

Early chondrichthyans had limited cranial kinesis and a non-suspensory hyoid, suggesting a ram dominated capture mechanism. Modern sharks are characterized by a kinetic upper jaw braced by a suspensory hyoid arch that is highly kinetic. The ventral hyoid arch in batoids is dissociated from the jaws, permitting extensive cranial kinesis. The evolution of kinetic jaws is thought to be responsible for the extensive radiation of feeding modes in actinopterygians, particularly that of suction, as well as that of chondrichthyan fishes. Modern elasmobranchs possess a remarkable variety of feeding modes for a group containing so few species. Ram, suction, bite or filter feeding may be used to capture prey, with most species able to use a combination of two modes during a strike. Suction feeding, which has repeatedly arisen within all major elasmobranch clades, is associated with a suite of morphological and behavioral specializations similar to that of actinopterygians. We investigate prey capture performance in a diverse assemblage of purported suction feeding elasmobranchs. Drop in water pressure measured at the prey shows that suction inflow drops off rapidly with distance from the mouth. Maximum suction pressure in the buccal cavity is 8 and 44 times greater than at a distance of half gape width from the mouth in ram and suction feeders respectively. Consequently, prey capture by suction alone is only successful at close range. Indeed, the strongest and most specialized suction feeders, such as bamboo and nurse sharks, are primarily benthic and thus are able to closely approach or lie-in-wait for potential prey. Generalist feeders like spiny dogfish use ram coupled with moderate suction to pursue and catch prey. Benthic batoids such as Little skates and Atlantic guitarfish use primarily ram with very little suction to capture prey.