Meeting Abstract

P1.56  Sunday, Jan. 4  Morphological and Kinematic Variation in Upper Jaw Protrusion of Four Species of Cyprinid Fishes STAAB, KL*; FERRY-GRAHAM, LA; HERNANDEZ, LP; George Washington University; Moss Landing Marine Labs; George Washington University kstaab@gwmail.gwu.edu

Cyprinidae is the largest family of freshwater fishes and likely owes some of its success to the novel feeding mechanism employed by members of the group. Cyprinid fishes effect premaxillary protrusion via a kinethmoid, a novel sesamoid ossification within the rostral skeleton that is a cypriniform synapomorphy. 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. Cyprinid fishes are trophically diverse with most species feeding on secondary producers such as macrocrustaceans and insects. Many basal 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 of the kinethmoid is more likely to be correlated with ecological niche than phylogenetic position of a species within the group. Here we performed kinematic analyses on four cyprinid species with widely varying kinethmoid shape. Our initial hypothesis was that Carassius auratus, a species with an elongate kinethmoid that feeds on benthos would have slower protrusion speeds than species that feed on insects and possess shorter kinethmoids. We found the opposite to be true. C. auratus protrudes its upper jaw faster than Gila robusta, Danio rerio, and Devario aequipinnatus. C. auratus is a member of the Cyprininae, the most basal subfamily within Cyprinidae. Our data suggest that when kinethmoid-mediated premaxillary protrusion first evolved, it was a versatile mechanism, allowing basal cyprinids to search through benthos as well as effectively capture elusive prey.