Mouth closing model in clariid catfishes

[Silurus]

Van Wassenbergh S, P Aerts, D Adriaens & A Herrel, 2005. A dynamic model of mouth closing movements in clariid catfishes: the role of enlarged jaw adductors. JOurnal of Theoretical Biology, 234: 49-65.

Abstract

Some species of Clariidae (air breathing catfishes) have extremely large (hypertrophied) jaw closure muscles. Besides producing higher bite forces, the enlarged muscles may also cause higher accelerations of the lower jaw during rapid mouth closure. Thus, jaw adductor hypertrophy could potentially also enable faster mouth closure. In this study, a forward dynamic model of jaw closing is developed to evaluate the importance of jaw adductor hypertrophy on the speed of mouth closure. The model includes inertia, pressure, tissue resistance and hydrodynamic drag forces on the lower jaw, which is modelled as a rotating half-ellipse. Simulations are run for four clariid species showing a gradual increase in jaw adductor hypertrophy (Clarias gariepinus, Clariallabes longicauda, Gymnallabes typus and Channallabes apus). The model was validated using data from high-speed videos of prey captures in these species. In general, the kinematic profiles of the fastest mouth closure from each species are reasonably well predicted by the model. The model was also used to compare the four species during standardized mouth closures (same initial gape angle, travel distance and cranial size). These simulations suggest that the species with enlarged jaw adductors have an increased speed of jaw closure (in comparison with the non-hypertrophied C gariepinus) for short lower jaw rotations and when feeding at high gape angles. Consequently, the jaw system in these species seems well equipped to capture relatively large, evasive prey. For prey captures during which the lower jaw rotates freely over a larger distance before impacting the prey, the higher kinematic efficiency of the C gariepinus jaw system results in the fastest jaw closures. In all cases, the model predicts that an increase in the physiological crosssectional area of the jaw muscles does indeed contribute to the speed of jaw closure in clariid fish.

[beng]

Apparently this species feeds amphibiously and the mouth closing stuff may be an adaptation to this.

see:
http://news.bbc.co.uk/1/hi/sci/tech/4902784.stm

There are anecdotal reports of Clarius gariepinus coming out of water to eat birds on the shore etc.

I have seen a swamp eel, Monopterus albus, out of water, hunting worms on a wet drain bank at night.

What i am wondering about with regards to the latest report is how does the catfish sense the insects on land? Clariids usually have very small eyes, is their eyesight that good that they can see out of water and judge distance etc to catch insects?