In total darkness, some snakes can locate a warm-blooded prey without ever seeing it clearly. How do they manage it? The answer lies in a small pit located between the eye and the nostril.
Publicité
Publicité
This pit is lined with a very thin membrane that responds to infrared radiation, the heat given off by any body. In rattlesnakes and other pit vipers, the membrane is warmed by this radiation, and nerve endings turn that warmth into a signal. The heat-sensitive ion channel TRPA1 appears to act as the receptor.
The surprising detail is that the pit works somewhat like a pinhole camera. It forms a heat image, but with very poor spatial resolution, so the snake does not see a sharp outline. The brain then combines this information with vision in the optic tectum.
Not all snakes have this organ. It is found in some rattlesnakes, some pythons and some boas, while most snakes lack it. Even in these animals, the exact way the pit turns heat into a nerve signal is still debated.
