NDL 00010 | Crocodile | Protective crocodile bumps provide underwater sensing capabilities.

The crocodile has tough leathery skin for protection but lacks touch sensitivity. To counter this lack of perception, small dark-colored dimples cover the entire body of the crocodile. These beta-keratin domed spots can detect prey movement in the water. This dome reacts three-dimensionally due to a single hinge at a portion of the dome's edge, like a "living hinge" on a human-designed plastic part. The downward flex of the dome allows the crocodile to determine the direction of the stimulus. The externally stimulated dome, in turn, activates fast and slow-acting Merkel cells. The unique shape and specific task-oriented cells provide the crocodile with a map of its surroundings, steady-state (such as water current), and dynamic activity (such as approaching fish). This natural design could help inspire sensors on ships, municipal water systems, or fluid-based manufacturing processes.