ommatidium

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Related to ommatidia: Rhabdomere

ommatidium

(ŏm′ə-tĭd′ē-əm)
n. pl. ommatid·ia (-ē-ə)
One of the optical units, consisting of photoreceptors and usually one or more lenses, that make up a compound eye of an insect or a crustacean.

om′ma·tid′i·al (-ē-əl) adj.

ommatidium

(pl. ommatidia) any of the numerous facets which make up the compound eye of insects and other arthropods. Each ommatidium has its own lens and is composed of a group of retinal cells surrounded by pigment cells. The light-sensitive part of the ommatidium is the RHABDOM, and on its receiving a stimulus a photochemical reaction takes place which results in impulses being sent to the optic nerve.

ommatidium 

One of the visual elements of the compound eye of arthropods. It is hexagonal in shape and about ten times longer than its diameter. It consists of a corneal facet below which is a crystalline cone which collects light and a sensory area called the rhabdom, all of it being enclosed in a dark pigment.
References in periodicals archive ?
The ommatidia at the center and posterior edge of the compound eyes were square, others were hexagonal.
They were commonly located in basal sockets and sparsely distributed between the ommatidia.
Pigment and eyes absent, or 1+1 vestigial ommatidia.
Eyes with 6 large ommatidia and 2 very small each side of head.
The number of ommatidia forming the compound eye ranged from 216 to 249, with a mean of 237.
Thirty min post inoculation, conidia were found in clusters around ommatidia on the eyes, on setae, in depressions in the integument, on the ventral pronotum, and in the grooves of scales located along the ventral surfaces.
Although among major workers, eye size and ommatidia number are reported to be adequate characters for separating S.
2004), species in the genus Xenylla are mainly characterized by (1) 5+5, rarely 4+4 ommatidia, (2) postantennal organ absent, (3) mandible short with a well developed molar plate, maxillary head with normal lamellae, (4) furca rarely absent, showing a diverse morphology, if mucro separated from the dens, which normally bears 2 setae; mucro, however, fused with the dens or mucro absent, the dens has 1 or 2 setae, (5) empodium absent, and (6) abdominal segment V tergite with p3 as sensilla.