After ruling out a bunch of functions, the researchers discovered that the ISOs contain "mechanoreceptors," which are nerves that respond to pressure and vibration. Some are specially tuned to vibrations in the 20-35 Hertz range, just right for detecting tiny water ripples. Others respond to levels of pressure that are too faint for the human fingertip to detect.
This helps to explain how crocodiles and alligators can find prey so quickly, directing their strong jaws and sharp, big teeth in just the right direction for the death snap.
The most heavily wired ISOs are located in the mouth near the teeth. Crocs and gators use their teeth for many different things. Females, for example, delicately break open their eggs when they are ready to hatch. They also carry their hatchlings in their jaws, the same ones that can clamp down on prey with incredible force.
The sensitivity then permits such diverse actions. It also, I think, gives many species a cool speckled look. Unfortunately people like this style too, on handbags, shoes, luggage. Better to admire it on the living animal.
(Images: Steven Green, Catania Laboratory/Vanderbilt University)