title: Opsin expression, physiological characterization and identification of photoreceptor cells in the dorsal rim area and main retina of the desert locust, Schistocerca gregaria.
abstract: For compass orientation many insects rely on the pattern of sky polarization, but some species also exploit the sky chromatic contrast. Desert locusts, Schistocerca gregaria, detect polarized light through a specialized dorsal rim area (DRA) in their compound eye. To better understand retinal mechanisms underlying visual navigation, we compared opsin expression, spectral and polarization sensitivities and response-stimulus intensity functions in the DRA and main retina of the locust. In addition to previously characterized opsins of long-wavelength-absorbing (Lo1) and blue-absorbing visual pigments (Lo2), we identified an opsin of an ultraviolet-absorbing visual pigment (LoUV). DRA photoreceptors exclusively expressed Lo2, had peak spectral sensitivities at 441 nm and showed high polarization sensitivity (PS 1.3-31.7). In contrast, ommatidia in the main eye co-expressed Lo1 and Lo2 in five photoreceptors, expressed Lo1 in two proximal photoreceptors, and Lo2 or LoUV in one distal photoreceptor. Correspondingly, we found broadband blue- and green-peaking spectral sensitivities in the main eye and one narrowly tuned UV peaking receptor. Polarization sensitivity in the main retina was low (PS 1.3-3.8). V-log I functions in the DRA were steeper than in the main retina, supporting a role in polarization vision. Desert locusts occur as two morphs, a day-active gregarious and a night-active solitarious form. In solitarious locusts, sensitivities in the main retina were generally shifted to longer wavelengths, particularly in ventral eye regions, supporting a nocturnal lifestyle at low light levels. The data support the role of the DRA in polarization vision and suggest trichromatic colour vision in the desert locust.
authors.affiliation: Fachbereich Biologie, Tierphysiologie, Philipps-Universität Marburg, 35032 Marburg, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Schmeling
authors.affiliation: Laboratory of Neuroethology, Sokendai (The Graduate University for Advanced Studies), Shonan Village, Hayama, Kanagawa 240-0193, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Wakakuwa
authors.affiliation: Fachbereich Biologie, Tierphysiologie, Philipps-Universität Marburg, 35032 Marburg, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tegtmeier
authors.affiliation: Laboratory of Neuroethology, Sokendai (The Graduate University for Advanced Studies), Shonan Village, Hayama, Kanagawa 240-0193, Japan.
authors.forename: Michiyo
authors.initials: M
authors.lastname: Kinoshita
authors.affiliation: Fachbereich Biologie, Tierphysiologie, Philipps-Universität Marburg, 35032 Marburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bockhorst
authors.affiliation: Laboratory of Neuroethology, Sokendai (The Graduate University for Advanced Studies), Shonan Village, Hayama, Kanagawa 240-0193, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Arikawa
authors.affiliation: Fachbereich Biologie, Tierphysiologie, Philipps-Universität Marburg, 35032 Marburg, Germany homberg@biologie.uni-marburg.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Homberg
mesh_terms: D000818:Animals; D004596:Electroretinography; D005123:Eye / Q000033:anatomy & histology / Q000378:metabolism; D005260:Female; D006110:Grasshoppers / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D008027:Light; D008297:Male; D055355:Opsins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D009949:Orientation; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology*; D012333:RNA, Messenger; D012160:Retina / Q000033:anatomy & histology / Q000502:physiology*; D012168:Retinal Pigments / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D055355:Opsins; D012333:RNA, Messenger; D012168:Retinal Pigments
keywords: Compound eye; Dorsal rim area; Opsin expression; Phase change; Polarization sensitivity; Spectral sensitivity