Thursday, December 30, 2010
The Compound Eye
The type of eye commonly found in arthropods, including many insects and crustaceans. A compound eye has a mesh like appearance because it consists of hundreds or thousands of tiny lens-capped optical units called ommatidia. Each ommatidium has its own cornea, lens, and photoreceptor cells for distinguishing brightness and color. Individual ommatidia guide light through a lens and cone into a channel, known as a rhabdom, which contains light-sensitive cells. These are connected to optical nerve cells to produce the image. The ommatidia are separated from each other by varying degrees of pigment.
The ommatidia are packed side by side into bulges that create a wide field of view. As each unit is orientated in a slightly different direction, the honeycombed eye creates a mosaic image which, although poor at picking out detail, is excellent at detecting movement.