JANOVETZ, J.; Sweet Briar College: Functional Morphology of Feeding in the Scale-eating Piranha, Catoprion mento

The Wimple piranha, Catoprion mento, has a narrow natural diet with fish scales comprising an important proportion of its total food intake. Scales are eaten throughout most of ontogeny and adults feed almost exclusively on this food source. Catoprion exhibits a novel prey capture behavior when removing scales for ingestion. Scale-feeding strikes involve a high speed, open mouth, ramming attack where the prey is both bitten to remove scales and the force of the collision knocks scales free. Unique kinematic parameters of scale-feeding strikes include an average gape angle of over 120 degrees and a �plateau� stage of prolonged maximum displacement for cranial elevation and opercular expansion. When feeding on live fish or loose scales, Catoprion performs a typical ram/suction attack that is modulated according to the elusiveness of the prey. Captures of elusive fish elicit faster strikes with greater displacement of cranial elements than attacks on loose scales sinking in the water column. Despite its specialized diet and suite of anatomical characters, functional versatility in feeding behavior has not been reduced in Catoprion as predicted by many analagous studies in functional morphology. On the contrary, the behavioral repertoire of Catoprion has been broadened by the addition of a novel behavior for scale-feeding.