Meeting Abstract
54.11 Saturday, Jan. 5 Evolutionary Divergence in the Suction Feeding Mechanism of Fishes WILGA, C.D.; Univ. of Rhode Island cwilga@uri.edu
Recent studies have increased our understanding of suction generation during feeding in actinopterygian fishes. However, whether sharks and rays, which lack the dermal bones of the head used extensively by actinopterygians in suction feeding, use a similar mechanism was unknown. The jaw mechanism of elasmobranchs differs in from that of bony fishes in several ways: suspension, jaw elements, depression couplings. Jaw suspension as well as hyoid depression, a key component in suction generation, also differs between sharks and batoids, thus it is unknown whether this alteration has modified the suction mechanism. Jaw and hyoid kinematics and buccal pressure was quantified in three elasmobranch species and compared with two actinopterygian species from other studies. The suction feeding mechanism in elasmobranchs differs from actinopterygians primarily in hyoid arch movements due to morphological constraints. In all three elasmobranch species, the hyoid is depressed ventrally during suction generation as in actinopterygians; however, at the same time the hyoid is laterally compressed. The orientation of the hyomandibulae in the three suction feeding elasmobranchs constrains the distal hyomandibulae to adduct when the basihyal is depressed. This causes a temporal delay in the attainment of peak pressure in elasmobranchs compared to actinopterygians in which lateral and ventral expansion of the hyoid arch function jointly to generate pressure. The three elasmobranchs are still able to generate considerable suction pressure while paradoxically compressing the hyoid arch laterally. This represents a fundamental difference in the mechanism used to generate suction between elasmobranchs and actinopterygians. Future research includes the study of bite feeding elasmobranchs and basal actinopterygians to determine at what point the divergence in mechanism occurred.
