Meeting Abstract
32.6 Tuesday, Jan. 5 Morphological and Kinematic Variation in Upper Jaw Protrusion in Cypriniform Fishes STAAB, KL*; FERRY-GRAHAM, LA; HERNANDEZ, LP; George Washington University; Moss Landing Marine Labs; George Washington University kstaab@gwmail.gwu.edu
Cypriniformes is a diverse clade of freshwater fishes that likely owes some of its success to the novel feeding mechanism employed by members of the group. Cypriniform fishes effect premaxillary protrusion via a kinethmoid, a sesamoid ossification that is a synapomorphy for the order. The kinethmoid is entirely suspended by ligaments to the premaxillae, maxillae, palatines, and neurocranium. While the ligamentous attachments are relatively conserved among species, there is variation in kinethmoid shape. Cypriniforms are trophically diverse with most species feeding on secondary producers such as macrocrustaceans and insects. Many members are benthic feeders, while others can switch between pelagic and benthic modes depending on food availability. Our previous work has suggested that morphological variation in kinethmoid shape is likely correlated with ecological niche. Here we performed kinematic analyses on five cypriniform species with varying kinethmoid shape. Our initial hypothesis was that Carassius auratus and Catostomus insignis, species with elongate kinethmoids that feed on benthos would have slower protrusion speeds than Danio rerio and Devario aequipinnatus, which feed on insects and possess shorter kinethmoids. Our results tell a more complex story. C. auratus and C. insignis both fall into the faster protrusion category and this may be due to the architecture of the adductor mandibulae. Determination of where these species fall on the ram-suction spectrum revealed that Gila robusta and C. auratus are more suction-dominated feeders than the others. These data suggest that kinethmoid-mediated premaxillary protrusion in benthic cypriniforms is a versatile mechanism, allowing for searching through benthos as well as effective capture of elusive prey.
