• A significant convergence between the calcitic compound eye of the trilobite is found with remarkably equivalent structures in the tips of the arms of the brittle-stars (echinoderms), and these latter structures derived from the mesodermal skeleton (stereom) are evidently optical. (mapoflife.org)
  • The eyes in these two systematic groups are remarkably similar in general appearance and organization but they are formed by different mechanisms during development and differ in many details. (pnas.org)
  • In nature, arthropods have a remarkably sophisticated class of imaging systems, with a hemispherical geometry, a wideangle field of view, low aberrations, high acuity to motion and an infinite depth of field. (spiedigitallibrary.org)
  • It is worth adding, perhaps, that it is only the male strepsipteran that has these eyes which it employs on its nuptial flight, in search for the female which is permanently enclosed in a host insect (often a wasp), with only the reproductive organs protruding. (mapoflife.org)
  • Our data show that cricket eyes are spectrally more specialized than has previously been assumed, suggesting that similar adaptations in other insect species might have been overlooked. (biomedcentral.com)
  • 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. (thefreedictionary.com)
  • Centipedes (Latin, = hundred foot) are exclusively predatory arthropods belonging to the class Chilopoda (Latin, = fang foot). (osu.edu)
  • Our data show that the r-opsin gene ( onychopsin ) is expressed exclusively in the photoreceptor cells of the eye, whereas c-opsin mRNA is confined to the optic ganglion cells and the brain. (biologists.org)
  • The spectral absorption properties of visual pigments are mainly determined by their opsins, and thus opsins are crucial for understanding the adaptations of animal eyes. (biomedcentral.com)
  • We assign three of these opsins to visual pigments found in the compound eyes with peak absorbances in the green (515 nm), blue (445 nm) and UV (332 nm) spectral range. (biomedcentral.com)
  • In addition, we provide evidence for two ocellar photopigments with peak absorbances in the green (511 nm) and UV (350 nm) spectral range, and with opsins that differ from those expressed in the compound eyes. (biomedcentral.com)
  • In phylogenetic analyses, onychopsin forms the sister group to the visual r-opsins of arthropods, suggesting that the product of this gene functions in onychophoran vision. (biologists.org)
  • Our behavioural analyses, in conjunction with previous data, demonstrate that both species exhibit photonegative responses to wavelengths ranging from ultraviolet to green light (370-530 nm), and electroretinograms reveal that the onychophoran eye is maximally sensitive to blue light (peak sensitivity ∼480 nm). (biologists.org)
  • We demonstrate that alternatively spliced RNAs derived from a single Pax-6 gene in the squid ( Loligo opalescens ) are expressed in the embryonic eye, olfactory organ, brain, and arms. (pnas.org)
  • Compound eyes in arthropods demonstrate distinct imaging characteristics from human eyes, with wide angle field of view, low aberrations, high acuity to motion and infinite depth of field. (spiedigitallibrary.org)
  • Arthropods include the only invertebrate group to evolve flight. (els.net)
  • A possible strategy used to evolve complex image-forming eyes from the primitive eyes present in the last common ancestor is the use of similar developmental mechanisms with the same or closely related transcription factors. (pnas.org)
  • This xiphosuran chelicerate shows many typical arthropod features both externally and internally, (c) comparison of the structure of the arthropod brain, for example, that of L. polyphemus and a crustacean and (d) might suggest that the chelicerae of the former are homologous to the second antennae of the latter, but this is far from clear. (els.net)
  • Pax-6 in vertebrates and its homolog eyeless in Drosophila are known to be essential for eye development. (pnas.org)
  • Recent data based on the demonstration that the paired domain/homeodomain transcription factor, Pax-6/eyeless, has a critical role in eye development in vertebrates ( 5 - 10 ) and Drosophila ( 11 ) support the idea of a monophyletic origin of the eyes. (pnas.org)
  • Heterozygous mutations in Pax-6 of vertebrates are associated with a variety of eye diseases, including aniridia in human and Small eye ( Sey ) in rodents ( 5 , 6 , 8 ). (pnas.org)
  • Taken together these data suggest that two types of image-forming eyes, complex eyes of vertebrates and compound eyes of arthropods, share-at least partially-developmental pathways. (pnas.org)
  • The Crustacea is a subphylum of arthropods defined by the nauplius larva, two pairs of antennae and biramous ('two branched') second antennae. (els.net)
  • A cross‐section of a typical arthropod segment showing basic characteristics. (els.net)
  • Mayer G, Whitington PM, Sunnucks P and Pflüger H‐J (2010) A revision of brain composition in Onychophora (velvet worms) suggests that the tritocerebrum evolved in arthropods. (els.net)
  • Furthermore, this suggests that the last common ancestor of these organisms at the protostome-deuterostome divergence possessed eyes in which a Pax-6 gene was already active ( 16 ). (pnas.org)
  • Arthropods exhibit unparalleled diversity and abundance along with a correspondingly large ecological impact. (els.net)
  • Different explanations for the diversity of eyes have been proposed. (pnas.org)
  • 1. the simple eye of many invertebrates, consisting of retinal cells, pigments, and nerve fibers. (thefreedictionary.com)
  • 1997) Evidence for a clade of nematodes, arthropods and other moulting animals. (els.net)
  • There is an explanation in the beginning of the book 'expedition' explaining why animals there have no eyes. (blogspot.com)
  • Arthropods are the most successful of all animals on earth. (iaszoology.com)
  • This is called an apposition eye . (britannica.com)
  • However, the established semiconductor sensor technologies and optics are essentially planar, which experience great challenges in building such systems with hemispherical, compound apposition layouts. (spiedigitallibrary.org)
  • With the recent advancement of stretchable optoelectronics, we have successfully developed strategies to build a fully functional artificial apposition compound eye camera by combining optics, materials and mechanics principles. (spiedigitallibrary.org)
  • However, the challenges in building such systems with hemispherical, compound apposition layouts cannot be met through established planar sensor technologies and conventional optics. (spiedigitallibrary.org)
  • At a more fundamental level there is now evidence that a fully functioning compound eye with precise focus and good visual acuity has evolved at least twice in the arthropods. (mapoflife.org)
  • Here we discuss the emergence of camera-like eyes, corneal nipple arrays, extreme visual accuity, fibre optics and eye loss. (mapoflife.org)
  • One of the visual elements of the compound eye of arthropods. (thefreedictionary.com)
  • In an alternate pathway to the one that transmits visual images, the eye perceives sunlight. (thefreedictionary.com)
  • To clarify which type of opsin the single visual pigment is based on, we localised the corresponding mRNA in the onychophoran eye and brain using in situ hybridization. (biologists.org)
  • According to the rival theory advocated by Gottsche and others, each element of the compound eye yields a small but complete image. (yorku.ca)
  • A theory put forth by Johannes Müller to explain the vision of Arthropods possessed of compound eyes. (yorku.ca)
  • When the atmosphere cleared up later, these alternate senses were so well developed and entrenched that vision did not have much chance: the first stages of eyes would be poor, and would not convey an appreciable advantage to their owners, so their evolution never got under way. (blogspot.com)
  • I doubt eye evolution would really be held back by superior senses, already present, but that line of thought deserves further thought. (blogspot.com)
  • The devices combine elastomeric compound optical elements with deformable arrays of thin silicon photodetectors, which were fabricated in the planar geometries and then integrated and elastically transformed to hemispherical shapes. (spiedigitallibrary.org)
  • Unlike the two outer layers of the eye, the retina does not extend to the front of the eyeball. (thefreedictionary.com)
  • Accessory structures of the eye are the lacrimal gland and its ducts in the upper lid, which bathe the eye with tears tears, watery secretion of the lacrimal gland, which is located at the outer corner of the eye socket immediately above the eyeball. (thefreedictionary.com)
  • 2010) Arthropod relationships revealed by phylogenomic analysis of nuclear protein‐coding sequences. (els.net)
  • Recently, an enigmatic r-opsin-like protein called arthropsin has been identified in various bilaterian taxa, including arthropods, lophotrochozoans, and chordates, by performing transcriptomic and genomic analyses. (frontiersin.org)
  • Centipedes are essential predators in our ecosystem, feeding on numerous other arthropods. (osu.edu)
  • On the basis of these results it was proposed that eyeless/Pax-6 is the master control gene for eye morphogenesis ( 11 , 14 , 15 ). (pnas.org)
  • Molluscs represent a third phylum in which highly complex eyes are present. (pnas.org)
  • Our data show that arthropsin is expressed in the central nervous system of E. rowelli , including the brain and the ventral nerve cords, but not in the eyes. (frontiersin.org)
  • In homozygotes, Pax-6 mutations are lethal due to a complete absence of eyes and nose and severe defects in brain formation (see ref. 12 for a review). (pnas.org)
  • Arthropod Structure and Development 39: 143-153. (els.net)
  • The human eye is a spheroid structure that rests in a bony cavity (socket, or orbit) on the frontal surface of the skull. (thefreedictionary.com)
  • In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. (thefreedictionary.com)