title: Photoreceptor spectral tuning by colorful, multilayered facet lenses in long-legged fly eyes (Dolichopodidae).
abstract: The facet lenses of the compound eyes of long-legged flies (Dolichopodidae) feature a striking, interlaced coloration pattern, existing of alternating rows of green-yellow and orange-red reflecting facets, due to dielectric multilayers located distally in the facet lenses (Bernard and Miller. Invest Ophthalmol 7:416-434 (1968). We investigated this phenomenon in the dolichopodid Dolichopus nitidus by applying microspectrophotometry, electron microscopy and optical modeling. The measured narrow-band reflectance spectra, peaking at ~540 and ~590 nm with bandwidth ~105 nm, are well explained by a refractive index oscillating sinusoidally in six periods around a mean value of about 1.44 with amplitude 0.6. The facet lens reflectance spectra are associated with a spectrally restricted, reduced transmittance, which causes modified spectral sensitivities of the underlying photoreceptors. Based on the modeling and electroretinography of the dolichopodid Condylostylus japonicus we conjecture that the green and orange facets narrow the spectral bandwidths of blue and green central photoreceptors, respectively, thus possibly improving color and/or polarization vision.
authors.affiliation: Computational Physics, Zernike Institute for Advanced Materials, University of Groningen, NL9747AG, Groningen, The Netherlands. D.G.Stavenga@rug.nl.
authors.forename: D G
authors.initials: DG
authors.lastname: Stavenga
authors.affiliation: Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, Slovenia.
authors.forename: A
authors.initials: A
authors.lastname: Meglič
authors.affiliation: Laboratory of Neuroethology, Sokendai-Hayama, The Graduate University for Advanced Studies, Hayama, 240-0193, Japan.
authors.forename: P
authors.initials: P
authors.lastname: Pirih
authors.affiliation: Laboratory of Neuroethology, Sokendai-Hayama, The Graduate University for Advanced Studies, Hayama, 240-0193, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Koshitaka
authors.affiliation: Laboratory of Neuroethology, Sokendai-Hayama, The Graduate University for Advanced Studies, Hayama, 240-0193, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Arikawa
authors.affiliation: Air Force Research Laboratory, Eglin Air Force Base, FL, 32542-6810, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Wehling
authors.affiliation: Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, Slovenia.
authors.forename: G
authors.initials: G
authors.lastname: Belušič
mesh_terms: D000818:Animals; D054910:Compound Eye, Arthropod / Q000378:metabolism* / Q000648:ultrastructure*; D004175:Diptera / Q000033:anatomy & histology* / Q000378:metabolism*; D004596:Electroretinography; D005260:Female; D019476:Insect Proteins / Q000378:metabolism; D000068897:Iridescence; D008297:Male; D046529:Microscopy, Electron, Transmission; D015591:Microspectrophotometry; D008954:Models, Biological; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D012168:Retinal Pigments / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D012168:Retinal Pigments
keywords: Iridescence; Photoreceptors; Spectral filters; Spectral sensitivity; Visual pigments