GRUBICH, Justin R.; RICE, Aaron N.*; WESTNEAT, Mark W.; Field Museum of Natural History; Field Museum of Natural History; Univ. of Chicago; Field Museum of Natural History: Functional Morphology of Bite Mechanics in the Great Barracuda, Sphyraena barracuda (Walbaum 1792)
The great barracuda, Sphyraena barracuda, is a voracious marine predator that captures fish with a swift ram feeding strike. While aspects of its ram feeding kinematics have been examined, the actual bite mechanism used to process prey remains an unexplored aspect of their feeding strategy. Barracuda attack fish larger than the gape of their jaws, and in order to swallow large prey, can sever their prey into pieces with powerful jaws replete with sharp teeth. Our study examines the functional morphology and biomechanics of great barracuda jaws and teeth used to slice through prey. Using specimens from the Field Museum and Florida Keys, we examined the jaw mechanism of an ontogenetic series of barracuda ranging from 20 g to 8.2 kg. Jaw functional morphology was described from dissections of fresh specimens and bite mechanics were determined from digitized photos using the software program MandibLever (v. 3.0). High speed video of barracuda biting (1500 f/s) revealed that prey are impacted at the corner of the mouth during capture in a orthogonal position where rapid repeated bites and small lateral headshakes result in cutting the prey in two. Predicted force output of the lower jaw approximately doubles from the jaw tip to the corner of the mouth reaching as high as 9 N in large individuals. A robust palatine bone embedded with large triangular blade-like teeth opposes the mandible at rear of the jaws providing for a bite capable of cutting through the flesh and bone of its prey. From biting experiments, the palatine teeth puncture and hold the prey item, while the lower jaw teeth saw the prey item in half. The combination of biomechanical techniques to examine the bite of the barracuda demonstrates how the different components of the feeding mechanism interact.
