HULSEY, C.D.; University of Tennessee, Knoxville: Linkage Mechanics, Jaw Protrusion, and Diet Specialization in Cichlid Fishes

I examined the anterior jaw four bar linkage model, jaw protrusion, and feeding specialization on evasive prey in Central American Heroine Cichlids. I modeled the anterior jaws of 30 cichlids as four bar linkages, using empirical measurements of the lower jaw, maxilla, nasal, and suspensorial fixed link. Then, using kinematic predictions from the four bar linkage model, I estimated kinematic transmission (KT) expected during jaw protrusion. Because the maxilla pushes the toothed premaxilla out during jaw protrusion, I predicted higher KT linkages should characterize species with greater jaw protrusion. Jaw protrusion ranged from 1.5 to 14.2 % of cichlid standard length as measured on cleared and stained specimens and was correlated with higher anterior jaw KT. Live cichlids were also filmed at 500 frames / sec when feeding on fish to determine if jaw protrusion measured on specimens was an accurate measure of the jaw protrusion organisms use to capture prey. Additionally, as jaw protrusion is commonly thought to aid in the capture of evasive prey, such as fish and shrimp, I determined the contribution of these prey types to the gut contents in the cichlids examined. Greater amounts of evasive prey in the diet were correlated with more protrusible jaws. Independent contrasts suggested the correlation between anterior jaw KT and protrusion as well as the correlation between protrusion and specialization on evasive prey were not simply due to phylogenetic history.