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.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.