Society of Integrative and Comparative Biology Abstract 2006

Using Morphology to Predict Feeding Behavior: A Preliminary Study of Juvenile Red Snapper (Lutjanus campechanus) Feeding

Case, J.E. Texas A&M University at Galveston,
Marshall, C.D. Texas A&M University at Galveston

Red snapper are an important commercial species in the Gulf of Mexico. However, their biology and feeding mechanics are virtually unknown. The goals of this study were to, (1) characterize the feeding biomechanics of juvenile red snapper and, (2) to test the hypothesis that the jaw biomechanics differ between subjects from different size classes and habitats. Juvenile red snapper from three size classes (<49 mm, 50-69 mm, and >70 mm SL) and two habitats (on-ridge & off-ridge) were collected from the northwestern Gulf of Mexico off the coast of Texas. Fourteen morphometric measurements of the lower jaw and main closing adductor muscles, A2 and A3, were recorded. These data were used in the biomechanical model MandibLever 3.0 (M.W. Westneat), which provided dynamic outputs of predicted jaw function, such as effective mechanical advantage (EMA) and jaw velocity (VR). Outputs from the model were used to predict and characterize the feeding biomechanics from the three size classes and two habitats. Overall, the model reported a low EMA and high VR, suggesting that juvenile red snapper are primarily suction feeders. This suggestion is supported by kinematic feeding trials of live juvenile red snapper. No significant differences among size classes (p > 0.05) or between habitats (p > 0.05) were observed in EMA or VR. However, as body size increased, VR tended to decrease, and EMA tended to increase. Although our data is for juveniles only, the trends in EMA and VR suggest a shift from primarily suction feeding as juveniles to primarily biting as adults. This trend is supported by kinematic feeding trials of juvenile red snapper, modeling data from a few adult red snapper, as well as observations of feeding behavior in adults.