SNAKES have a unique sensory system for detecting infrared radiation, with which they can visualize temperature changes within their immediate environment. Using this special sense, they can image the body heat radiating from warm-blooded animals nearby. This enables them to track their prey quickly and with great accuracy, even in the dark, and to target the most vulnerable parts of the prey’s body when they strike. It also warns them of the presence of predators, and may be used to find appropriate locations for building dens.
Infrared detection is known to be mediated by a specialized sensory apparatus called the pit organ, but several important questions about the detection mechanisms remain. It is still unclear, for example, where in the pit organ the infrared sensor is located, and whether it detects light particles directly, in a similar way to the eye, or heat energy. These questions have now been answered by a group of researchers from the University of California in San Francisco. In an advance online publication in the journal Nature, they report the identification of the sensor: it is an ancient protein called TRPA1, which has been adapted for this purpose in snakes, but not in other vertebrates.