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 ?
These single-lens systems have a limited field of view, but insects and other species with eyes composed of multiple units called ommatidia enjoy panoramic vision.
From the most basal to the most derived groups there is a tendency towards reduction on the number of ommatidia in the eyes from few in C.
1993), they also share a V-pattern in the rhabdomeres of the ommatidia, further supporting their relationship (Fischer et al.
If spider secondary eyes evolved from single ommatidia, what might these ancestral ommatidia have looked like?
This study aimed to acquire additional relevant knowledge by morphometric investigations of differences between males and females and between the 3 species of various morphological features, including eye size, facet size, and numbers of ommatidia and ommatrichia.
1); eyes bare, holoptic, contiguous at median part of upper frons (Figs 2, 3), ommatidia largest anterodorsally, but no distinct demarcation between upper and lower ommatidia; ocellar tubercle slightly prominent; lower frons triangular, with very fine median groove; face with margins continuous with those of lower frons, diverging ventrally, receding; gena narrowly visible in lateral view (Fig.
Three individuals exhibited necrotizing hepatopancreatitis (44, 48, and 67; numbers reflect specimen numbers as shown in Table 1), 3 had extensive (affecting [greater than or equal to] 66% of the surface) lesions of the ommatidia (7, 14, 21), and 7 had moderate to extensive granulomas (18, 19, 20, 42, 45, 58, 67; animal 67 also had necrotizing hepatopancreatitis, as noted earlier).
In this mechanism, distance is computed by measuring the convergence angle formed by the lines-of-sight from ommatidia of the left and right eyes (Baldus 1926; Barros-Pita & Maldonado 1970; Wehner 1981; Bauer 1981, 1985; Kral 1999; Kral et al.
He and his Berkeley colleagues Ki-Hun Jeong and Jaeyoun Kim created an artificial, dome-shaped eye with faux ommatidia.
The head is slightly narrower anteriorly, the eyes, always present, are reduced to a few ommatidia and the propodeum is very short.
In general, serpulid receptors are roughly analogous to ommatidia in arthropod apposition compound eyes, with a single lens element passing light into a single sensory cavity, fully shielded by screening pigment in the supporting cells.
After expelling the meconium, it molts to the pupal stage which turns yellow, with red ommatidia and ocelli (Chien et al.