Waltzek, T.B.*; Wainwright, P.C.: The Functional Morphology of Jaw Protrusion Among Neotropical Cichlids

The evolution of protrusible upper jaws among acanthopterygian teleosts has long been argued a major factor contributing to the success of this extremely diverse group of fishes. Yet, few studies have investigated upper jaw protrusion in a comparative framework. Additionally, previously unstudied taxa are revealing new kinematic pathways of protrusion of not only the upper jaws but also the lower jaws. In this investigation the kinematics, functional morphology, and performance measures of upper and lower jaw protrusion were analyzed among several Central and South American cichlids. Petenia splendida and a member of its sister genus, Caquetaia spectabile, both which exhibit extreme jaw protrusion were compared to each other and to the basal outgroups Cichla ocellaris and Astronotus ocellatus which do not exhibit the same level of jaw protrusion. Digital high speed film (500 fps) of feeding on live guppy prey was utilized to compare kinematic and performance variables. Dissection and bone/cartilage clearing and staining were used to compare the functional morphology among the taxa. Unlike much of the previous work on jaw protrusion, kinematic data was used to measure prey capture performance by measuring the ram and suction components of successful feeding events. Feeding performance data was used to explore the relationship between jaw protrusion and the generation of suction and ram. Comparisons of dissected and cleared and stained specimens revealed novel joints within the suspensorium allowing considerable lower jaw protrusion coordinated with upper jaw protrusion in Petenia splendida and Caquetaia spectabile. Finally, patterns of kinematic and morphological convergence will be compared among Petenia splendida, Caquetaia spectabile, and other distantly related extreme jaw protruding teleosts.