Scientists from the Field Museum of Natural History and the University of Chicago have studied the bite mechanics of the Great barracuda (Sphyraena barracuda) and have published their results in the latest issue of the journal Zoology.
Justin Grubich, Aaron Rice, and Mark Westneat examined and measured the musculoskeletal architecture of the upper and lower jaws by dissecting fresh and preserved specimens, and analyzed the bite pattern of the barracuda by placing gelatin blocks in the mouths of barracuda specimens, closing them by hand and then staining the blocks.
The authors also generated predictions of mechanical advantage, effective mechanical advantage, muscle torque, individual bite power, and dynamic and static bite forces by analysing their measurements with computer programs, and used high-speed cameras to film juvenile barracudas capturing and processing prey.
Great barracudas are predatory fish common throughout the world's tropical seas and are almost exclusively piscivorous.
AttackThe species attacks prey by swimming rapidly and capturing it with long serrated jaws, slicing into the flesh with a multitude of sharp caniniform teeth.
Barracudas employ a ram-feeding mode to capture large prey by slamming into the prey with extremely high body velocity, and completing the strike with a powerful slicing bite.
The authors found that arracudas process large prey with a series of powerful bites and rapid lateral headshakes. In several instances, post-capture biting observed in the juvenile barracuda in this study resulted in severing the prey into pieces...
Impale and sliceIn summarizing their findings, the authors write: he jaws and teeth of the great barracuda are built for impaling and then quickly slicing their piscine prey. The anatomy of the lower jaw reveals a strong third class lever mechanism that maximizes force from the adductor muscles through an increased mechanical advantage at the rear of the mandible.
Dynamic simulations and static modeling of barracuda jaw mechanics predict moderate bite forces that, when transmitted through the razor sharp teeth, can produce tremendous flesh slicing pressures.
This force generating capacity in combination with the scissor-like morphology of a serrated lower jaw that slides past a robust toothed palatine bone produces a shearing bite capable of cutting large fish prey into smaller manageable pieces for swallowing.
Barracuda bite forces scale with positive allometry, suggesting that larger fish may use the prey slicing technique to a greater degree than small individuals.
Barracudas employ a specialized feeding mode that we describe here as ram-biting, that involves a ram strike followed by biting with a scissor-like cutting motion of the jaws.
For more information, see the paper, Grubich, JR, AN Rice and MW Westneat (2008) Functional morphology of bite mechanics in the great barracuda (Sphyraena barracuda). Zoology 111, pp. 16"29.