Compound eye of a dragonfly

A compound eye is a visual organ found in arthropods such as insects and crustaceans. Anisoptera redirects here For the genus of trees see Anisoptera (tree. In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting It may consist of thousands^[1] of ommatidia which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distinguish brightness and color. The Compound eye of Insects is composed of units called ommatidia. The cornea is the transparent front part of the Eye that covers the iris, Pupil, and Anterior chamber. The lens is a transparent biconvex structure in the Eye that along with the Cornea, helps to Refract Light to be focused A photoreceptor, or photoreceptor cell, is a specialized type of Neuron (nerve cell found in the Eye 's Retina that is capable of The image perceived by the arthropod is a combination of inputs from the numerous ommatidia, which are oriented to point in slightly different directions. Compared with single-aperture eyes, compound eyes have poor image resolution; however, they possess a very large view angle and the ability to detect fast movement and, in some cases, the polarization of light. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain Image resolution describes the detail an Image holds The term applies equally to Digital images film images and other types of images Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations ^[2]

Types

Drawing from Robert Hooke's, Micrographia of the compound eye of a grey drone fly. Robert Hooke, FRS (18 July 1635 – 3 March 1703 was an English Natural philosopher and Polymath who played an important role in the Micrographia is a historical book by Robert Hooke, detailing the then twenty-eight year-old Hooke's observations through various lenses.

Compound eyes are typically classified as either apposition eyes, that form multiple inverted images, or superposition eyes, that form a single erect image. ^[3]

Apposition eyes

Apposition eyes can be divided into two groups. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Rhabdoms are transparent rods found in the center of each Ommatidium in the Compound eye of Arthropods These rods are constructed from the eight photoreceptor The Compound eye of Insects is composed of units called ommatidia. The mantis shrimp is the most advanced example of an animal with this type of eye. Mantis shrimp or stomatopods are marine Crustaceans the members of the order Stomatopoda. In the other kind of apposition eye, found in the Strepsiptera, each lens forms an image, and the images are combined in the brain. The Strepsiptera (known in older literature as twisted-winged parasites) are an order of Insects with nine families making up about 600 species This is called the schizochroal compound eye or the neural superposition eye (which, despite its name, is a form of the apposition eye).

Superposition eyes

The second type is named the superposition eye. The superposition eye is divided into three types; the refracting, the reflecting and the parabolic superposition eye. The refracting superposition eye has a gap between the lens and the rhabdom, and no side wall. Each lens takes light at an angle to its axis and reflects it to the same angle on the other side. The result is an image at half the radius of the eye, which is where the tips of the rhabdoms are. This kind is used mostly by nocturnal insects. In the parabolic superposition compound eye type, seen in arthropods such as mayflies, the parabolic surfaces of the inside of each facet focus light from a reflector to a sensor array. Mayflies are Insects which belong to the Order Ephemeroptera (from the Greek ephemeros = "short-lived" pteron Long-bodied decapod crustaceans such as shrimp, prawns, crayfish and lobsters are alone in having reflecting superposition eyes, which also has a transparent gap but uses corner mirrors instead of lenses. True shrimp are swimming decapod Crustaceans classified in the Infraorder Caridea, found widely around the world in both fresh Prawns are Crustaceans belonging to the sub-order Dendrobranchiata   Crayfish, crawfish, crawdads, or crodgers are freshwater Crustaceans resembling small Lobsters to which they are closely Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as A mirror is an object with a surface that has good Specular reflection; that is it is smooth enough to form an Image.

Compound eye of Antarctic krill as imaged by an electron microscope

Other

The holoptic compound eyes of a syrphid fly (Eristalinus taeniops)

Good fliers like flies or honey bees, or prey-catching insects like praying mantis or dragonflies, have specialized zones of ommatidia organized into a fovea area which gives acute vision. Antarctic krill ( Euphausia superba) is a Species of Krill found in the Antarctic waters of the Southern Ocean. An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image Holoptic refers to the way the eyes of a Diptera meet along the dorsal length of its head The Insect order Mantodea or mantises consists of approximately 2000 species worldwide in Temperate and Tropical habitats of Anisoptera redirects here For the genus of trees see Anisoptera (tree. The Compound eye of Insects is composed of units called ommatidia. In the acute zone the eye are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution.

There are some exceptions from the types mentioned above. Some insects have a so-called single lens compound eye, a transitional type which is something between a superposition type of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp Dioptromysis paucispinosa. The Mysidacea is a group of small Shrimp -like creatures comprising the two related orders Mysida and Lophogastrida. The shrimp has an eye of the refracting superposition type, in the rear behind this in each eye there is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone. This projects an upright image on a specialized retina. The resulting eye is a mixture of a simple eye within a compound eye.

Another version is the pseudofaceted eye, as seen in Scutigera. The House centipede, Scutigera coleoptrata, is a yellowish grey Centipede with 15 pairs of legs This type of eye consists of a cluster of numerous ocelli on each side of the head, organized in a way that resembles a true compound eye. An ocellus (plural ocelli) is a type of Photoreceptor organ in animals

The body of Ophiocoma wendtii, a type of brittle star, is covered with ommatidia, turning its whole skin into a compound eye. The Brittle star Ophiocoma wendtii inhabits Coral reefs from Bermuda to Brazil. Brittle stars, or ophiurids, are Echinoderms closely related to Sea stars.

References

See also

• Rhabdom

External links

• The Compound Eye
• Make Your Own Compound Eye by Stephanie Bailey
• Did you know that shrimps blink?