Monday, July 11, 2011
mini post 2- Depth perception in other species
Chapter 10 provides some insight into depth perception in other species. I thought this was interesting so I looked into it further. I found some information on chameleons and colossal squids. Chameleons have the ability to change color which allows them to communicate and express their intentions, or mood, to other chameleons. They also have very unusual eyes. Their eyelids are fused, and cover almost the entire eyeball, except for a small hole to let the pupil see through. The chameleon can scan for prey and potential threats at the same time because each eye can be moved independently from the other. Because of this the chameleon has a full 360 degree field of vision. When the chameleon sees a potential prey, it focuses both eyes in the same direction. By doing this the chameleon gains stereoscopic vision. Stereoscopic vision is where an object can be seen with two eyes at the same time, with both eyes set in the same plane. Stereoscopic vision is very important in depth perception. Animals that have this type of vision usually need the ability to judge distances precisely. Because the chameleon captures prey by shooting out its tongue at high speed, a technique that requires a very precise distance and depth perception, which is where stereoscopic vision is very important for a chameleon.
Colossal squids have the largest eyes in the animal kingdom. Each eye can be up to 30 cms across, which is bigger than a dinner plate and its lenses are the size of oranges. Their huge eyes allow for them to see in dim light conditions. The ability to see in dim conditions is very useful for the squid because it spends most of its time hunting 2000 meters below the surface. Like the chameleon, the colossal squid has stereoscopic vision. Stereoscopic vision also distinguishes the colossal squid from the giant squid. Having stereoscopic vision gives the colossal squid a greater ability to judge distances. Another unique vision characteristic the colossal squid has is that each eye has an organ known as a photophore. The photophore is like a built-in "headlight". Whenever the colossal squid focuses its eyes to the front, the photophores produce enough light for the squid to see its prey in the dark.