soulxtc
September 3rd, 2006, 05:40 PM
http://www.physorg.com/newman/gfx/news/Snake.jpg
The head of this pit viper shows a nostril, pit hole and eye (left to right). In the sketch at right, radiation enters the pit organ and hits a heat-sensitive membrane. Because point-like objects spread out into disc-shaped images on the membrane, images are blurry. Scientists recently found that edge detectors in the brain must reconstruct the heat distribution from blurry images to inform the snake of greater detail of its surroundings. Image credit: Sichert, Andreas, et al.
Call it a sixth sense, or evolution’s gift to these cold-blooded reptiles: some snakes have infrared vision. Also called “heat vision,” the infrared rays, which have longer wavelengths than those of visible light, signify the presence of warm-blooded prey in 3 dimensions, which helps snakes aim their attacks. Pit vipers and boids, the two snake types that possess this ability, have heat-sensitive membranes that can detect the difference in temperature between a moving prey—such as a running mouse—and its surroundings on the scale of milliKelvins.
The detection system, which consists of cavities located on each side of the head called “pit organs,” operates on a principle similar to that of a pinhole camera, explain scientists Andreas Sichert, Paul Friedel and J. Leo van Hemmen in a recent issue of Physical Review Letters. A pinhole camera is a camera without a lens, where light from an image passes through a very small hole. Similarly, a pit organ’s aperture is about 1 mm—large enough to allow the snake to quickly detect moving prey. Some scientists (de Cock Buning) even suggest that pythons—a type of boid—have a variety of differently shaped pit organs, each serving a different biological function.
“The information of the infrared and the visual system are both represented in the optic tectum,” Sichert told PhysOrg.com. “This information forms a neuronal map, where, for example, the front part of the optic tectum represents the part of visual space in front of the snake. How exactly the two systems merge is as yet unknown. In the optic tectum, six classes of tectal cells have been identified that respond to infrared and visual stimuli in different ways. So a snake can get additional information such as ‘is a moving visible object warm (e.g., a warm-blooded animal) or cold?’ In case of bad optical conditions (most prominent example is darkness), it can of course ‘see’ warm (or cold) objects.”
http://www.physorg.com/news76249412.html
The head of this pit viper shows a nostril, pit hole and eye (left to right). In the sketch at right, radiation enters the pit organ and hits a heat-sensitive membrane. Because point-like objects spread out into disc-shaped images on the membrane, images are blurry. Scientists recently found that edge detectors in the brain must reconstruct the heat distribution from blurry images to inform the snake of greater detail of its surroundings. Image credit: Sichert, Andreas, et al.
Call it a sixth sense, or evolution’s gift to these cold-blooded reptiles: some snakes have infrared vision. Also called “heat vision,” the infrared rays, which have longer wavelengths than those of visible light, signify the presence of warm-blooded prey in 3 dimensions, which helps snakes aim their attacks. Pit vipers and boids, the two snake types that possess this ability, have heat-sensitive membranes that can detect the difference in temperature between a moving prey—such as a running mouse—and its surroundings on the scale of milliKelvins.
The detection system, which consists of cavities located on each side of the head called “pit organs,” operates on a principle similar to that of a pinhole camera, explain scientists Andreas Sichert, Paul Friedel and J. Leo van Hemmen in a recent issue of Physical Review Letters. A pinhole camera is a camera without a lens, where light from an image passes through a very small hole. Similarly, a pit organ’s aperture is about 1 mm—large enough to allow the snake to quickly detect moving prey. Some scientists (de Cock Buning) even suggest that pythons—a type of boid—have a variety of differently shaped pit organs, each serving a different biological function.
“The information of the infrared and the visual system are both represented in the optic tectum,” Sichert told PhysOrg.com. “This information forms a neuronal map, where, for example, the front part of the optic tectum represents the part of visual space in front of the snake. How exactly the two systems merge is as yet unknown. In the optic tectum, six classes of tectal cells have been identified that respond to infrared and visual stimuli in different ways. So a snake can get additional information such as ‘is a moving visible object warm (e.g., a warm-blooded animal) or cold?’ In case of bad optical conditions (most prominent example is darkness), it can of course ‘see’ warm (or cold) objects.”
http://www.physorg.com/news76249412.html