title: Bottom Feeding and Beyond: How the Premaxillary Protrusion of Cypriniforms Allowed for a Novel Kind of Suction Feeding.
abstract: While much of the functional work on suction feeding has involved members of Acanthopterygii, an earlier cypriniform radiation led to over 3200 species filling nearly every freshwater trophic niche. Within the great majority of acanthomorph clades that have been investigated suction feeding and the underlying morphology responsible for the generation of rapid suction have been largely conserved. This conserved feeding-apparatus is often associated with increasing the force experienced by the prey item, thus making a strike on elusive prey more effective. Cypriniforms' trophic anatomy is comprised of a number of novelties used for benthic feeding, which characterized early members of this clade. The modified cypriniform structure of the oral jaws represents a situation in which a particular type of suction feeding allowed for probing the benthos with a more functionally maneuverable anatomy. Requisite evolutionary modifications included origin and elongation of a median kinethmoid, duplications of certain divisions of the muscles of the adductor mandibulae, and origin of a dorsal, intra-buccal muscular palatal organ used in winnowing detritus. The elongated kinethmoid (coupled with modified adductor muscles) allowed for a type of premaxillary protrusion that decoupled the upper and lower jaws, enabled premaxillary protrusions with a closed mouth, and facilitated benthic feeding by increasing functional flexibility. The resultant flow of fluid generated by cypriniforms is also quite flexible, with multiple instances of peak flow in a single feeding event. This greatly modified morphology allowed for a degree of kinematic maneuverability not seen within most acanthomorphs. Later cypriniform radiations into piscivorous, insectivorous, or planktivorous feeding guilds were associated with shortening of the kinethmoid and with simplified morphology of the adductor, likely involving an emphasis on ram feeding. Although this suite of morphological novelties seemingly originated within the context of benthic feeding, with minimal modifications these anatomical features were later coopted during radiations into different functional niches.
authors.affiliation: *Department of Biological Sciences, The George Washington University, Science and Engineering Hall, 800 22nd Street NW, Suite 6000, Washington, DC 20052, USA; Department of Biology, McDaniel College, 2 College Hill, Westminster, MD 21157, USA phernand@gwu.edu.
authors.forename: L Patricia
authors.initials: LP
authors.lastname: Hernandez
authors.affiliation: *Department of Biological Sciences, The George Washington University, Science and Engineering Hall, 800 22nd Street NW, Suite 6000, Washington, DC 20052, USA; Department of Biology, McDaniel College, 2 College Hill, Westminster, MD 21157, USA.
authors.forename: Katie Lynn
authors.initials: KL
authors.lastname: Staab
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D003531:Cypriniformes / Q000033:anatomy & histology* / Q000502:physiology*; D005247:Feeding Behavior; D007568:Jaw / Q000033:anatomy & histology; D018482:Muscle, Skeletal / Q000502:physiology; D011235:Predatory Behavior