Evolution of Tapetum Lucidum

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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…show more content…
The tapetum lucidum, reflects with constructive interference allowing it to increase the quality of light to pass through the retina. For example, on a cat the tapetum lucidum lowers the minimum threshold of vision 6-fold, empowering the cat to see light that is invisible to the human.  A = optic disk (retina is strongly attached here). B = tapetum lucidum C = retina D = lens TYPES OF TAPETUM Tapeta can be classified according to their location in vertebrates and mechanism in invertebrates. Choroidal tapeta are the most common and are classified as tapetum fibrosum and tapetum cellulosum. The simplest type is the tapetum fibrosum, which is found principally in mammals, including herbivores (elephants, horses and goats), cetaceans (whales and dolphins), certain marsupials (Tasmanian Devil), and a rodent (Cuniculus pacas). The tapetum fibrosum consists of extracellular collagen fibrils that are stacked orderly with the majority of the its fibers running horizontally. The number of layered fibrils varies between species and can be up to several hundred thick. The most studied tapetum fibrosum among mammals is found in the cow and is located posteriorly and dorsally. The thickness is variable, increasing its thickness posteriorly. In species with a choroidal tapetum, the retinal epithelium in the area is the tapetum in un-pigmented, it allowing the light to pass subsequently reflected by the tapetum. This contrasts with the pigmented retinal epithelium

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