compound eye


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compound eye:

see eyeeye,
organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other
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Compound Eye

 

(also faceted eye), the principal paired organ of vision in insects, crustaceans, and some other invertebrates. Compound eyes are made up of special structural units, ommatidia, whose corneal lenses are in the shape of convex hexahedrons. In insects they are immobile and located at the sides of the head, often occupying almost the entire surface, for example, in dragonflies, flies, and bees. In crustaceans they sometimes are set on movable stalks. The compound eyes most thoroughly studied are those of insects and larvae of species with incomplete metamorphosis; the eyes of such insects are composed of hundreds or even thousands of ommatidia.

Depending on the anatomical characteristics and optical properties of the ommatidia, three types of compound eyes are distinguished: apposition, superposition, and neurosuperposition. In apposition compound eyes, which are usually characteristic of diurnal insects, adjacent ommatidia are isolated from one another by an opaque pigment, and the receptors perceive only perpendicular light rays falling along the axis of a given ommatidium.

In superposition compound eyes, which are characteristic of nocturnal and crepuscular insects and many crustaceans, the ommatidia may be isolated as a result of the pigment’s ability to shift. When there is insufficient light, the rays that fall at an oblique angle are superposed and pass through several facets. Thus the sensitivity of the eye increases with weak illumination.

Neurosuperposition compound eyes accumulate signals from sense cells in various ommatidia, which receive light from the same point in space. In some insects, such as praying mantises and mayflies, one part of the eye may be of the apposition type, while the other is of the superposition type.

In all types of compound eyes the rhabdomeres of the sense cells, which contain a photopigment similar to rhodopsin, serve as the photosensitive element. The absorption of quanta of light by the photopigment is the first link in the chain of processes that results in the generation of a nerve signal by the sense cell.

Because of the projection of the retina on the optic ganglia of the brain and, in part, the characteristics of compound-eye optics, the ommatidium’s raster plays a more important role in the perception of the environment than individual sense cells. Because the optical axes of the ommatidia diverge at extremely acute angles (l°–6°), the compound eye is unable to distinguish minute details. However, its high adaptability and high contrast sensitivity (1–5 percent) permit some insects to distinguish the flashing of light at frequencies as high as 250–300 hertz (Hz) (the human limit is approximately 50 Hz). Compound eyes enable many invertebrates to distinguish color, perceive ultraviolet rays, and determine the direction of the plane of linearly polarized light.

REFERENCES

Mazokhin-Porshniakov, G. A. Zrenie nasekomykh. Moscow, 1965.
Prosser, L., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. Chapter 12. (Translated from English.)

G. A. MAZOKHIN-PORSHNIAKOV

compound eye

[′käm‚pau̇nd ′ī]
(invertebrate zoology)
An eye typical of crustaceans, insects, centipedes, and horseshoe crabs, constructed of many functionally independent photoreceptor units (ommatidia) separated by pigment cells.
References in periodicals archive ?
Caption: Figure 2: Modeled tissues from the extracted and the compound eye models.
After billions of years of evolution, some insects, arthropods, and the terrifying mantis shrimp, have ended up with compound eyes. While you and I, and most other animals on Earth, are equipped with just a pair of standard eyes (simple eyes in biological parlance), some living creatures have compound eyes that are made of thousands of ommatidia.
25); malar area about one-third width of median ocellar diameter; interalveolar distance slightly shorter than alveolar diameter; alveolocular distance 1.5 times interalveolar distance; interocellar distance 1.8 times median ocellar diameter; scape 5.2 times longer than wide; compound eye 2.4 times longer than broad; gena about 0.6 times width of compound eye in profile.
Head width (HW): Maximum width of head in full face view in an imaginary straight line close to the posterior margin of compound eyes.
On the basis of molecular phylogeny, other researchers (Oakley and Cunningham 2002) have shown that the paired compound eyes of some seed shrimp evolved within an otherwise eyeless group of Ostracoda.
They have 2 large compound eyes as well as 3 smaller eyes called ocelli which can detect changes in light and dark.
This compound eye proved to possess the same kind of structure as the eyes of bees and dragonflies living today, but it lacks the lenses that are typical of modern eyes of this type," said the researchers.
Ancient mechanisms of visual sense organ development based on comparison of the gene networks controlling larval eye, ocellus, and compound eye specification in Drosophila.
fn: lengths of flagellomeres 1.n of right antenna, IO, D and d respectively: minimum distance between compound eyes, antero-posterior diameter and transverse diameter of right compound eye, all in dorsal view of head, PO: d/D.
Landmark Anatomical Description 1 Anterior part of head 2 Left anterior-lateral part of the antennae 3 Left posterior-lateral part of the antennae 4 Left anterio-lateral most region of the compound eye 5 Lateral most region of the compound eye 6 Left posterio-lateral most region of the compound eye 7 Left mid posterior part of the head 8 Posterior mid part of the head 14 Right anterior-lateral part of the antennae 13 Right posterior-lateral part of the antennae 12 Right anterio-lateral most region of the compound eye 11 Lateral most region of the compound eye 10 Right posterio-lateral most region of the compound eye 9 mid posterior part of the head Table III: Location And Classification Of 32 Anatomical Landmarks Digitized On The Shape Of Pronotum Capsule Of B.
SEM micrographs of the compound eye of 3 Bactrocera species showing the shapes of the ommatidia (square and hexagonal), central region (A, C, E) and dorsal region (B, D, F).
Operating like the compound eye of an insect, the observatory will have a field of view 20 times greater than that of the American space agency's hugely successful Kepler space telescope.