| 释义 |
‖ ommatidium Zool.|ɒməˈtɪdɪəm|
Pl. -ia.
[mod.L., f. Gr. type *ὀµµατίδιον, dim. of ὄµµα, ὄµµατ- eye.]
A structural element of the eyes of Invertebrates; e.g. one of the simple eyes which make up the compound eye of an insect.
1884J. Carrière in Q. Jrnl. Microsc. Sci. XXIV. 674 The whole set of eye-units (ommatidia) of Musca vomitoria are enclosed in a chitinous capsule. [Note] The term ‘ommateum’ was introduced by Lankester in his memoir on the eyes of Scorpions to signify the entire soft parts of the non-segregate (unicorneal) eye of Arachnida and Hexapoda... The similar term ‘ommatidium’ is introduced in this paper to signify the units consisting each of a retinula and a vitrella, together with their sheath of pigment cells, into which the ommateum of the multi-corneal (polymeniscous) eye of Arthropods, is segregated. 1888Rolleston & Jackson Anim. Life 452 note, Patten..points out..the following general features...Every eye consists as a rule of a number of eye-elements or ommatidia, which may and do occur isolated as well as aggregated. Every ommatidium is composed of 2–4 central cells or retinophoræ fused together, and inclosing an axial nerve, and of one or more surrounding circles of pigmented cells or retinulæ. Ibid. 492 [Arthropoda] In a polymeniscous eye a single lens-facet, a vitrella, and retinula constitute an ‘element’, or the two latter..an ommatidium. 1925A. D. Imms Gen. Textbk. Entomol. i. 79 The distinctness of vision depends partly upon the number and size of the ommatidia. 1932Metcalf & Flint Fund. Insect Life iv. 110 It is believed that each ommatidium does not form an image of the whole object, but only preserves the intensity, pattern, and color of the light coming from the particular small part of the object that is in line with its long axis. Indeed, the several ommatidia, or ‘tubes’, are usually so isolated from each other by pigment, that no light can pass from one to the other. 1973Sci. Amer. Dec. 35/3 The compound eye of Drosophila is a remarkable structure consisting of about 800 ommatidia: unit eyes containing eight receptor cells each.
Hence ommaˈtidial a., pertaining to an ommatidium.
1890Anatomischer Anzeiger V. 356 This spine-bearing cornea is soon shed and a faceted one formed, each facet..often containing in the centre the remnants of an ommatidial spine. 1925A. D. Imms Gen. Textbk. Entomol. i. 76 The hypodermis between the ommatidial pillars becomes transformed into the secondary pigment cells. 1975Nature 10 Apr. 522/2 The axons from seven retinula cells of one ommatidium interweave with those of their four neighbouring facets in such a way that four bundles of three fibres, heterogeneous with regard to their ommatidial origin, plus one single axon are produced. |