The snout of the sling-jaw wrasse captures prey using multibar linkages to shoot its jaw out at high speed.
"Nonetheless, the jaw mechanism of even a fancy snake looks simple next to what some fish do with multibar linkages in their heads (Westneat 1991). The most extreme must be the sling-jaw wrasse, Epibulus insidiator, which shoots out an otherwise unnoticeable snout to snag prey. According to Westneat and Wainwright (1989), who've analyzed the biomechanics of the system, this wrasse can protrude its jaw by a length equal to 65 percent of normal head length. Protrusion takes only about a thirtieth of a second; acceleration exceeds 100 meters per second squared, or 10 g; and snout speed hits 2.3 meters per second, or over 5 miles per hour. The components--bones, ligaments, and muscle--may be ordinary, but their arrangement is anything but." (Vogel 2003:401)
"Epibulus insidiator (Pallas) possesses the most extreme jaw protrusion ever measured in fishes. Biomechanical models of the mechanisms of jaw protrusion and hyoid depression in Epibulus are proposed and tested. The models are designed using principles of four-bar linkages from engineering theory. The models calculate the geometry of the feeding mechanisms from morphometric data on cranial anatomy. Predictions made from the models about the feeding kinematics of Epibulus are tested by comparison with kinematic data. The model of the jaw mechanism is accurate in predicting the unique feeding mechanics of the jaws of Epibulus for most relationships between kinematic variables. A model of simultaneous cranial elevation and sternohyoideus muscle contraction is accurate in predicting hyoid depression during feeding. Biomechanical considerations limit the number of possible pathways of evolution of the jaw mechanism of Epibulus from that of its closest labrid relatives." (Westneat 1991:159)
Learn more about this functional adaptation.
- Steven Vogel. 2003. Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press. 580 p.
- Westneat, MW. 1991. Linkage biomechanics and evolution of the unique feeding mechanism of Epibulus insidiator (Labridae: Teleostei). Journal of Experimental Biology. 159: 165-184.