Meeting Abstract
32.6 Wednesday, Jan. 5 Do convergent means of premaxillary protrusion produce similar flows during suction feeding? STAAB, KL*; HOLZMAN, R; HERNANDEZ, LP; WAINWRIGHT, PC; George Washington Univ; UC Davis; George Washington Univ; UC Davis kstaab@gwmail.gwu.edu
A protrusible upper jaw has independently evolved at least twice within teleosts and has been implicated in the success of the groups that possess this morphology: Acanthomorpha and Cyrpiniformes. We use digital particle image velocimetry (DPIV) to compare suction feeding flow dynamics in a representative of each of these groups: goldfish, a cyprinid, and bluegill, a centrarchid. Bluegill protrude the upper jaws via linkages to the opercular apparatus as well as to the lower jaw. Goldfish protrude the upper jaws via a sesamoid bone, the kinethmoid, a synapomorphy for Cypriniformes. Using DPIV, we contrast 1) the spatial pattern of flow in the two species, 2) the temporal relationship between flow and head kinematics with a focus on the timing of flow and jaw protrusion, and 3) the contribution of jaw protrusion to the forces exerted on prey. We found that spatial patterns of flow were similar in the two species. However, goldfish were slower to reach maximal excursions, and more flexible in the relative timing of jaw protrusion, other jaw movements, and suction flows. Goldfish were also able to sustain high flow longer than bluegill, in part because they appear to generate lower peak flow speeds. The different timing of jaw protrusion in goldfish resulted in less ability to magnify suction forces. This discrepancy of force exerted on prey corresponds with different trophic niches and feeding behavior of the two species, with bluegill using powerful suction to capture insect larvae whilst goldfish sort through detritus and sediment. The kinethmoid of goldfish may permit jaw protrusion independent of lower jaw movement, perhaps explaining the ability of goldfish to decouple suction flows due to buccal expansion from upper jaw protrusion.
