Evolution of Tapetum Lucidum
Human Eye Vs. Animal EyeBy:Andrea Torres
ABSTRACT
The tapetum lucidum is an evolutionary advantage for animals. It enables animals to see in dimmer light than the animal would otherwise be able to see in. The tapetum lucidum is useful to animals, but it also has a use to humans. Human beings use the tapetum lucidum to scan for reflected eye-shine, in order to detect and identify the species of animals in the dark and to send trained search dogs and search horses out at night. Historically, its function was regarded as simply to increase the light intensity of an image on the retina. Using eye shine to identify animals in the dark implies not only color but, also several other features. The color reciprocates to the type of tapetum lucidum with some distinction between species. Other features also include the distance between pupils’ related to its size, the height above the ground; the manner of blinking, (if there is any) and the movement of the eye shine (such as weaving, hopping, leaping, climbing or flying.) Tapetum cellulosum was discovered in the eyes of sharks, sturgeons, and coelacanths, suggesting that it may have been the first type of tapetum to evolve in vertebrates. These species have similar enough tapeta that they may have had a common ancestor with a tapetum developing at approximately the Devonian period or, at the earliest, the very late Silurian.
INTRODUCTION
The tapetum lucidum, in Latin it means “shining carpet”, a layer of the tissue in the eye of vertebrate and invertebrate animals. The tapetum is proximal to the photoreceptors and may be located in either the retina in vertebrate animals and proximal to the reticular cells in invertebrates animals. The "shining carpet" reflects visible light back through the retina increasing the light available for photo receptors. The tapetum reflects the photons that are not initially absorbed after they are passed through the photoreceptors. These reflector mechanisms are able to provide the
ABSTRACT
The tapetum lucidum is an evolutionary advantage for animals. It enables animals to see in dimmer light than the animal would otherwise be able to see in. The tapetum lucidum is useful to animals, but it also has a use to humans. Human beings use the tapetum lucidum to scan for reflected eye-shine, in order to detect and identify the species of animals in the dark and to send trained search dogs and search horses out at night. Historically, its function was regarded as simply to increase the light intensity of an image on the retina. Using eye shine to identify animals in the dark implies not only color but, also several other features. The color reciprocates to the type of tapetum lucidum with some distinction between species. Other features also include the distance between pupils’ related to its size, the height above the ground; the manner of blinking, (if there is any) and the movement of the eye shine (such as weaving, hopping, leaping, climbing or flying.) Tapetum cellulosum was discovered in the eyes of sharks, sturgeons, and coelacanths, suggesting that it may have been the first type of tapetum to evolve in vertebrates. These species have similar enough tapeta that they may have had a common ancestor with a tapetum developing at approximately the Devonian period or, at the earliest, the very late Silurian.
INTRODUCTION
The tapetum lucidum, in Latin it means “shining carpet”, a layer of the tissue in the eye of vertebrate and invertebrate animals. The tapetum is proximal to the photoreceptors and may be located in either the retina in vertebrate animals and proximal to the reticular cells in invertebrates animals. The "shining carpet" reflects visible light back through the retina increasing the light available for photo receptors. The tapetum reflects the photons that are not initially absorbed after they are passed through the photoreceptors. These reflector mechanisms are able to provide the
Cited: "Evolution of the Tapetum." Web. 20 Nov. 2010. . "Eye Anatomy and Function in Animals." Pet Health Care | Dog and Cat Behavior Information by Veterinarians. Web. 20 Nov. 2010. . Heinselman, By Craig. "Bigfoot: Eye Shine, Why and How by Craig Heinselman, Cryptozoologist 1999." Bigfoot Encounters. Web. 20 Nov. 2010. . Mifflin, From Krista. "Tapetum Lucidum." Dogs on About.com - All About Dogs and Puppies. Web. 20 Nov. 2010. . "Mythology of Tapetum Lucidum." Web. 20 Nov. 2010. "Tapetum Lucidum (anatomy) -- Britannica Online Encyclopedia." Encyclopedia - Britannica Online Encyclopedia. Web. 20 Nov. 2010. . "The Ocular Tapetum Lucidum: A Model System for Interdisciplinary Studies in Elasmobranch Biology - Heath - 2005 - Journal of Experimental Zoology." Wiley Online Library. Web. 20 Nov. 2010. .