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ommatidiumenUK
om·ma·tid·i·um O0072300 (ŏm′ə-tĭd′ē-əm)n. pl. om·ma·tid·i·a (-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.
[New Latin, diminutive of Greek omma, ommat-, eye; see okw- in Indo-European roots.]
om′ma·tid′i·al (-ē-əl) adj.ommatidium (ˌɒməˈtɪdɪəm) n, pl -tidia (-ˈtɪdɪə) (Zoology) any of the numerous cone-shaped units that make up the compound eyes of some arthropods[C19: via New Latin from Greek ommatidion, from omma eye] ˌommaˈtidial adjom•ma•tid•i•um (ˌɒm əˈtɪd i əm)
n., pl. -tid•i•a (-ˈtɪd i ə) one of the units that make up the compound eye of insects and other arthropods. [1880–85; < New Latin < Greek ommat-] om`ma•tid′i•al, adj. om·ma·tid·i·um (ŏm′ə-tĭd′ē-əm) Plural ommatidia One of the tiny light-sensitive parts of the compound eye of insects and other arthropods. An ommatidium resembles a single simplified eye. See more at compound eye.Thesaurus| Noun | 1. | ommatidium - any of the numerous small cone-shaped eyes that make up the compound eyes of some arthropodsocellus, simple eye, stemma - an eye having a single lenscompound eye - in insects and some crustaceans: composed of many light-sensitive elements each forming a portion of an image |
OmmatidiumenUK
ommatidium[‚äm·ə′tid·ē·əm] (invertebrate zoology) The structural unit of a compound eye, composed of a cornea, a crystalline cone, and a receptor element connected to the optic nerve. Ommatidium the structural and functional unit of a faceted eye in insects, crustaceans, and some myriapods. The om-matidium consists of three sections: a lens with a fixed focal length, the crystalline cone, and the group of light-sensitive receptor cells with nerve outgrowths that combine into nerve fibers. Each lens appears as a facet in the eye. Ommatidia developed in the course of evolution from isolated simple eyes, which eventually were integrated into compound, or faceted, eyes. The number of ommatidia in a compound eye varies, from 100 in a worker ant to 28,000 in a dragonfly. A faceted eye is specialized to discern movement and does not produce a sharp image or enough information to discern the shape of an object. The field of vision of a compound eye is very broad; for example, in the locust the visual angle of each om-matidium is 20°. Thus, any movement of a predator or prey would be noticed instantly by at least one ommatidium. ommatidiumenUK
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.ommatidiumenUK
Related to ommatidium: RhabdomereWords related to ommatidiumnoun any of the numerous small cone-shaped eyes that make up the compound eyes of some arthropodsRelated Words- ocellus
- simple eye
- stemma
- compound eye
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