Feeding biomechanics in the Great Barracuda during ontogeny

Abstract

In this study we investigated bite force and functional morphology of the feeding mechanism of the great barracuda Sphyraena barracuda through ontogeny. Theoretical estimates of bite force at two bite points were calculated for a size series of barracuda ranging from 18 to 130 cm TL (n=27) using a three-dimensional static equilibrium model. In addition, electromyography was used to determine the role of the adductor mandibulae subdivisions (A1, A2, A3) in jaw closure. All recorded subdivisions were active during jaw adduction, although onset times and activity durations differed among them. Bite force ranged from 1 to 93 N at the most anterior bite point, and from 3 to 258 N at the most posterior bite point. Mechanical advantage, in lever and posterior out lever, as well as the cross-sectional area of the majority of the adductor mandibulae subdivisions scaled with isometry; consequently bite force at both bite points also scaled with isometry. Bite force in S. barracuda increased in proportion to total length during ontogeny, which may be associated with a piscivorous diet throughout its life. When compared to other fishes, values of bite force in S. barracuda are among the lowest relative to its body size.