Arthropod Eye - Eyes and Functions

Eyes and Functions

Most copepods have a single compound eye in the middle of their head, but this copepod, of the family Corycaeus, possesses two large cuticular lenses paired to form a telescope. Like most spiders, this wolf spider has eight simple eyes, two main eyes at the front and six smaller secondary eyes. The main eyes form images. The secondary eyes detect peripheral movement, and have a reflective tapetum lucidum which improves night vision. Holochroal eye of an Early Devonian trilobite Paralejurus sp. Schizochroal eye of a Devonian trilobite from the family Calmoniidae Horseshoe crabs have two primary compound eyes and seven secondary simple eyes. Two of the secondary eyes are on the underside.

Most arthropods have at least one of two types of eye: lateral compound eyes, and smaller median ocelli, which are simple eyes. When both are present, the two eye types are used in concert because each has its own advantage. Flying insects can remain level with either type of eye surgically removed, but the two types combine to give better performance. Ocelli can detect lower light levels, and have a faster response time, while compound eyes are better at detecting edges and are capable of forming images.

Further information: Compound eye Further information: Ocellus

Read more about this topic:  Arthropod Eye

Famous quotes containing the words eyes and, eyes and/or functions:

    “They are friends; and friendly they guide him to prey
    Yet never partake of the treat—
    Eyes and brains to the dotard lethargic and dull,
    Pale ravener of horrible meat.”
    —Herman Melville (1819–1891)

    “Get up and once again politely lying
    Invite the ladies toward the mistletoe
    With greedy eyes that stare like an old crow.”
    —Allen Tate (1899–1979)

    “One of the most highly valued functions of used parents these days is to be the villains of their children’s lives, the people the child blames for any shortcomings or disappointments. But if your identity comes from your parents’ failings, then you remain forever a member of the child generation, stuck and unable to move on to an adulthood in which you identify yourself in terms of what you do, not what has been done to you.”
    —Frank Pittman (20th century)