Definition of ommatidium in English:

ommatidium

noun

Biology
  • Each of the optical units that make up the compound eye of an insect.

    • ‘The compound eye is composed of ~ 800 units called ommatidia.’
    • ‘Normally, new ommatidia are added at the dorsal margin of the eye, and thus the retina gradually enlarges with growth of the eye at each successive molt.’
    • ‘Note that in the insect ommatidium (unlike vertebrate limbs and Drosophila appendages) cells are being specified and determined individually, not as groups of cells.’
    • ‘Flies, crabs, and other arthropods have compound eyes in which many, sometimes hundreds, of individual ommatidia, or unit eyes, gather visual information.’
    • ‘Postlarvae settling at the vents have reasonably normal ommatidia, with layered rhabdoms, standard crystalline cones, and faceted external corneas reflective of the zoeal apposition eye.’
    • ‘The Drosophila retina is composed of 750 unit eyes, or ommatidia.’
    • ‘These novel morphological approaches to the study of the ommatidia and the foregut ossicles may have limited application in the fossil record.’
    • ‘The normal compound eye has regular ommatidia and bristles.’
    • ‘In all these animals, the larval eye continues to exist as part of the adult eye, although the number of ommatidia in the adult compound eye far exceeds the larval quantity.’
    • ‘The retina of the compound eye is organized into approximately 3000 functional units or ommatidia, each containing eight photoreceptor cells.’
    • ‘In in flies we have seen examples of incorrect chiral type, incorrect rotation, symmetrical ommatidia, and ommatidia with an incorrect number of photoreceptor cells (data not shown).’
    • ‘At the end of each eyestalk are some 10,000 ommatidia, or little eyes.’
    • ‘The compound eye of Drosophila is composed of hundreds of nearly identical ommatidia or unit eyes.’
    • ‘In contrast, myriapods and chelicerates mostly lack compound eyes and the ommatidia of the few groups that have compound eyes are very different from insect/crustacean ommatidia.’
    • ‘The adult retina consists of 800 identical unit eyes or ommatidia that are packed into a hexagonal array so precise that it is often referred to as a ‘neurocrystalline lattice’.’
    • ‘The ommatidium, or ‘unit eye,’ is reiterated nearly 800 times in the compound eye.’
    • ‘The adult retina is composed of 750 unit eyes known as ommatidia; each ommatidium contains precisely 14 cells.’
    • ‘Fleas show a transformation of the multifaceted eyes and ommatidia of most insects, replaced instead with heavily sclerotized, atypical ocelli, or ‘eyespots,’ or in some cases, a complete absence of any eye at all.’
    • ‘This paper dealt with the size of ommatidia as a function of body size in various insects.’
    • ‘During their development, some crustaceans simply enlarge the larval eye, adding ommatidia as the animal grows.’

Origin

Late 19th century: modern Latin, from Greek ommatidion, diminutive of omma, ommat- eye.

Pronunciation:

ommatidium

/ˌɒməˈtɪdɪəm/