A functional analysis of the jaw mechanism in the sling-jaw wrasse

Abstract

Sling-jaw wrasse can deploy their mouths forward at high speed to catch prey and collect food. The forward swimming of the fish and the deployment of the jaw mechanism has been simulated using numerical analysis of the equations of motion. Computed tomography and reverse engineering have been used to obtain accurate geometrical and mass data of an actual sling jaw wrasse including the jaw mechanism. The analysis shows that maximum snout acceleration is up to 10.7 g, whereas the maximum fish acceleration is up to 0.25 g, thus showing the advantage of having the deployable snout. The analysis also shows that maximum snout acceleration is highly dependent on the size of the fish. Small fish of 7.5 cm length have a maximum snout acceleration of up to 10.7 g, whereas large fish of 35 cm length have a maximum snout acceleration of up to 5.2 g. The analysis may help to explain why deployable jaws are not seen on fish greater than about 35 cm in length. Hypothetical predator-prey chasing scenarios show that the deployable mouth gives the sling-jaw wrasse a very significant advantage when the prey is in close range. The sling-jaw wrasse demonstrates that linkage mechanisms enable a high degree of optimisation of movement to be achieved in a deployment mechanism. Biomimetic applications of the jaw mechanism are briefly discussed. © 2011 WIT Press.