Vibrations help a frog locate tasty prey

Living in southern Africa, the aquatic clawed frog Xenopus laevis laevis finds insects by localizing their vibrations on the water’s surface. Hunting at night and unable to see well, the frog gets a wealth of information from about 180 sensory organs (the white “stitches” in the photo, collectively called the lateral-line system) on its skin. As an insect sloshes around, the moving water triggers signals in hair cells attached to the organs. Now, a group of researchers in Germany, led by Leo van Hemmen (Technical University of Munich), have developed a simple model, with a minimal set of assumptions, that explains how the lateral-line system works. Strikingly, the model suggests that the frog can both reconstruct the waveform of the water disturbance and determine its direction. The model thus explains the frog’s ability to distinguish between two different water disturbances coming simultaneously from insects—one of which might be inedible—in different directions. The model also agrees with experiment in showing that the sensory system can operate even if some of the lateral-line organs do not function properly. The researchers’ model may also be applicable to the mechanosensory systems of other animals, such as fish and crocodiles, which have similar receptor organs (J.-M. P. Franosch et al., Phys. Rev. Lett. 91 , 158101, 2003 http://dx.doi.org/10.1103/PhysRevLett.91.158101 )