rhabdom

rhabdom
—rhabdomal /rab doh"meuhl, rab"deuh meuhl/, adj.
/rab"deuhm, -dom/, n. Anat., Zool.
1. any of various rod-shaped structures.
2. the rod-shaped portion of an arthropod ommatidium. Also, rhabdome /rab"dohm/.
[1875-80; < LGk rhábdoma bundle of rods; see RHABDO-, -OMA]

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      transparent, crystalline receptive structure found in the compound eyes of arthropods (arthropod). The rhabdom lies beneath the cornea and occurs in the central part of each ommatidium (visual unit) of compound eyes. Incoming rays of light pass through a transparent cone, which acts to converge the rays onto the tip of the rhabdom. The rhabdom itself is rodlike and consists of interdigitating fingerlike processes (microvilli) that are contributed by a small number of photoreceptor cells. The number of microvilli from photoreceptor cells varies, with eight being the typical number found in insects (insect). Each photoreceptor cell in a rhabdom contains a nucleus, an energy-producing region with mitochondria (mitochondrion), and an axon that conveys electrical signals to neurons (neuron). In addition to photoreceptor cells, rhabdoms also contain pigment cells of various kinds that separate one ommatidium from the next and act to restrict the amount of light that each rhabdom receives.

      Rhabdoms are capable of resolving wavelength and plane of polarization. The ability of bees (bee) to navigate using patterns of polarization in the sky instead of the Sun when the sky is overcast is due to the way the photopigment molecules are organized on the microvilli in the rhabdoms. A photon will only be detected if the light-sensitive part of the photopigment molecule lies in the plane of polarization of the photon. The rhabdoms in the dorsal regions of bee eyes have their photopigment molecules aligned with the axes of the microvilli, which lie parallel to one another in the receptor. As a result, each receptor is able to act as a detector for a particular plane of polarization.

Michael Land
 

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Universalium. 2010.

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Look at other dictionaries:

  • Rhabdom — Rhab dom (r[a^]b d[o^]m), n. [Gr. ra bdwma a bundle of rods, fr. ra bdos a rod.] (Zo[ o]l.) One of numerous minute rodlike structures formed of two or more cells situated behind the retinul[ae] in the compound eyes of insects, etc. See Illust.… …   The Collaborative International Dictionary of English

  • Rhabdom — ⇒ Ommatidium …   Deutsch wörterbuch der biologie

  • Rhabdom — Rhabdoms are transparent rods, found in the center of each ommatidium in the compound eye of arthropods. These rods are constructed from the eight photoreceptor cells in the ommatidium. Each photocell is long and thin. They pack their area of the …   Wikipedia

  • Rhabdom — Das Rhabdom (von griech. rhabdos = „Rute, Stab“) ist der lichtleitende Achsstab innerhalb eines Ommatidiums des Komplexauges, oder eines Punktauges (Ocellus) eines Gliederfüßers. Es wird durch die 5 bis 9 Mikrovillisäume der Retinulazellen, auch… …   Deutsch Wikipedia

  • Rhabdom — Rhab|dom 〈n. 11〉 stabförmiges Organ in den Sehzellen von Komplexaugen [zu grch. rhabdos „Stab“] * * * Rhab|dom, das; s, e [zu griech. rhábdos = Stab, Rute] (Anat.): ↑ Stäbchen (3) u. ↑ Zapfen (6) in der Netzhaut des Auges. * * * Rhabdo …   Universal-Lexikon

  • rhabdom — or rhabdome noun Etymology: New Latin, from Late Greek rhabdōma bundle of rods, from Greek rhabdos rod Date: 1878 one of the minute rodlike structures in the retinulae in the compound eyes of arthropods …   New Collegiate Dictionary

  • rhabdom — n. [Gr. rhabdos, rod] (ARTHROPODA) A rodlike light sensitive structure formed by rhabdomeres in the ommatidium of a compound eye …   Dictionary of invertebrate zoology

  • rhabdom — noun Any of the rods that support each ommatidium in the compound eye of arthropods …   Wiktionary

  • Rhabdom — Rhab|dom 〈n.; Gen.: s, Pl.: e; Zool.〉 stabförmiges Organ in den Sehzellen von Facettenaugen [Etym.: <grch. rhabdos »Stab«] …   Lexikalische Deutsches Wörterbuch

  • Rhabdom — Rhabdo̱m [zu gr. ϱ̔αβδος = Rute, Gerte, Stab] s; s, e: allg. Bez. für die Stäbchen und Zapfen in der Netzhaut des Auges …   Das Wörterbuch medizinischer Fachausdrücke

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