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Goris, R. C. (2011) Infrared Organs of Snakes: An Integral Part of Vision. Journal of Herpetology, 45 2–14. 
Added by: Sarina (26 Jul 2021 12:22:05 UTC)   Last edited by: Sarina (29 Jul 2021 18:28:07 UTC)
Resource type: Journal Article
DOI: 10.1670/10-238.1
BibTeX citation key: Goris2011
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Categories: Englisch = English
Keywords: Infrarot = Infrared, Schlangen = Snakes
Creators: Goris
Collection: Journal of Herpetology
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Abstract
The infrared organs of boas, pythons, and pit vipers are true eyes that function not by a photochemical reaction but on the basis of heat generated in the receptors (called terminal nerve masses, TNMs), by electromagnetic radiation. In the pythons and pit vipers, the pit opening acts as the aperture of a pinhole camera, a virtual lens that permits the receptors to encode the movements of an infrared source sufficiently for the brain to form an image. Many boid snakes possess TNMs identical to those of the pythons but lack an opening that could serve as a lens. All TNMs are irrigated by a dense capillary network that serves as a heat regulator, mimicking the role of the photochemical cycle in the lateral eyes. Thus, the pits are an integral part of the snakes’ visual system, which makes use of the longer waves of the electromagnetic spectrum for which there are no appropriate photoreceptive pigments in nature; they do everything the eyes do. They are definitely not, as they have often been treated, a ‘‘sixth sense,’’ useful only for the detection and acquisition of prey. Just as the world that most insects see includes both the visual and the ultraviolet spectra, so the world that boas, pythons, and pit vipers see includes both the visual and the infrared spectra.
Added by: Sarina  Last edited by: Sarina
Notes
Thus, it is a fallacy to consider the pit organs as an independent sixth sense evolved solely for the purpose of detecting and acquiring prey. Not so. [...] Thus, the pits/infrared receptors are an integral part of the snakes’ visual system that makes use of the longer waves of the electromagnetic spectrum for which there are no appropriate photoreceptive pigments in nature. [...] To put it another way, just as the world that most insects see includes both the visual and the ultraviolet spectra, so the world that boas, pythons, and pit vipers see includes both the visual and the infrared spectra.

 

When examined with an electron microscope, the keratinous surface of the pit membrane or of the pit fundus is punctuated by a large number of pitlike depressions of micrometer proportions (Fig. 8). These are from 0.25–0.5 mm in depth and average in number about 3.66/mm2 (Amemiya et al., 1996a). Their effect is to efficiently disperse wavelengths centered around 500 nm, while allowing free passage of longer infrared wavelengths (Safer and Grace, 2004)


Added by: Sarina  Last edited by: Sarina
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