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Maximum running speed is the most important variable influencingmammalian eye size other than body size, according to new researchfrom The University of Texas at Austin. Species with larger eyesusually have higher visual acuity, says Chris Kirk, associateprofessor in the Department of Anthropology. But what are theecological factors that cause some mammals to develop larger eyesthan others? "If you can think of mammals that are fast like a cheetah or horse,you can almost guarantee they've got really big eyes," says Kirk."This gives them better vision to avoid colliding with obstacles intheir environment when they're moving very quickly." Kirk and physical anthropology doctoral student Amber Heard-Boothare the first to apply Leuckart's Law - a hypothesis that wasdeveloped specifically for birds and speed of flight - to 50species of mammals. The paper is forthcoming in the journal Anatomical Record.Heard-Booth presented the findings at the 2011 American Associationof Physical Anthropology Meeting, where she was awarded the MildredTrotter Prize for exceptional graduate research in evolutionarymorphology. Previously it was thought that the time of day that an animal isactive (nocturnal or diurnal) would be the main factor driving theevolution of mammalian eye size. However, comparative research on the anatomy of the eye has shownthat although nocturnal and diurnal species differ in eye shape,they often have similar eye sizes. Although nocturnal species mayappear to have bigger eyes because more of the cornea is exposed tolet in more light, activity pattern only has a modest effect on eyesize. By comparison, body mass plus maximum running speed together canexplain 89 percent of the variation in eye size among mammals. The researchers controlled for body size and evolutionaryrelationships, and found that the relationship between eye diameterand maximum running speed is stronger than the relationship betweenbody mass and running speed. "You start looking at comparative data and one thing that is alwaysgoing to influence eye size is body size. An elephant is alwaysgoing to have bigger eyes than a mouse," Kirk says. "Elephants are the biggest animals we measured, but they are notthat fast compared to a cheetah or zebra. At the same time,porcupines - the biggest of the rodents in our sample - are slowwhile some smaller rodents are much faster. There is going to bethe effect of body mass, but when you look at maximum running speedin isolation or when you hold body mass constant, it's stillsignificantly related to eye size," Kirk says. "And when you combine maximum running speed and body mass as yourtwo variables influencing how big an eye is, they can explainalmost all of the differences observed between species. This is ahighly significant result.". The e-commerce company in China offers quality products such as Vertical Machining Center , Gantry Machining Center, and more. For more , please visit CNC Machining Centers today!
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