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Yilmaz A, Belušič G, J Foster J, Tocco C, Khaldy L, Dacke M. Polarisation vision in the dark: green-sensitive photoreceptors in the nocturnal ball-rolling dung beetle Escarabaeus satyrus. J Exp Biol 2024; 227:jeb246374. [PMID: 38284763 DOI: 10.1242/jeb.246374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 01/19/2024] [Indexed: 01/30/2024]
Abstract
Many insects utilise the polarisation pattern of the sky to adjust their travelling directions. The extraction of directional information from this sky-wide cue is mediated by specialised photoreceptors located in the dorsal rim area (DRA). While this part of the eye is known to be sensitive to the ultraviolet, blue or green component of skylight, the latter has only been observed in insects active in dim light. To address the functional significance of green polarisation sensitivity, we define the spectral and morphological adaptations of the DRA in a nocturnal ball-rolling dung beetle-the only family of insects demonstrated to orient to the dim polarisation pattern in the night sky. Intracellular recordings revealed polarisation-sensitive green photoreceptors in the DRA of Escarabaeus satyrus. Behavioural experiments verified the navigational relevance of this finding. To quantify the adaptive value of green sensitivity for celestial orientation at night, we also obtained the polarisation properties of the night sky in the natural habitat of the beetle. Calculations of relative photon catch revealed that under a moonlit sky the green-sensitive DRA photoreceptors can be expected to catch an order of magnitude more photons compared with the UV-sensitive photoreceptors in the main retina. The green-sensitive photoreceptors - which also show a range of morphological adaptations for enhanced sensitivity - provide E. satyrus with a highly sensitive system for the extraction of directional information from the night sky.
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Affiliation(s)
- Ayse Yilmaz
- Lund Vision Group, Department of Biology, Lund University, 223 62 Lund, Sweden
| | - Gregor Belušič
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia
| | - James J Foster
- Lund Vision Group, Department of Biology, Lund University, 223 62 Lund, Sweden
- Neurobiology, University of Konstanz, Universitätsstr. 10, 78464 Konstanz, Germany
| | - Claudia Tocco
- Lund Vision Group, Department of Biology, Lund University, 223 62 Lund, Sweden
| | - Lana Khaldy
- Lund Vision Group, Department of Biology, Lund University, 223 62 Lund, Sweden
| | - Marie Dacke
- Lund Vision Group, Department of Biology, Lund University, 223 62 Lund, Sweden
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Takács P, Száz D, Vincze M, Slíz-Balogh J, Horváth G. Sunlit zebra stripes may confuse the thermal perception of blood vessels causing the visual unattractiveness of zebras to horseflies. Sci Rep 2022; 12:10871. [PMID: 35927437 PMCID: PMC9352684 DOI: 10.1038/s41598-022-14619-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 06/09/2022] [Indexed: 11/09/2022] Open
Abstract
Multiple hypotheses have been proposed for possible functions of zebra stripes. The most thoroughly experimentally supported advantage of zebra stripes is their visual unattractiveness to horseflies (tabanids) and tsetse flies. We propose here a plausible hypothesis why biting horseflies avoid host animals with striped pelages: in sunshine the temperature gradients of the skin above the slightly warmer blood vessels are difficult to distinguish from the temperature gradients induced by the hairs at the borderlines of warmer black and cooler white stripes. To test this hypothesis, we performed a field experiment with tabanids walking on a host-imitating grey test target with vessel-mimicking thin black stripes which were slightly warmer than their grey surroundings in sunshine, while under shady conditions both areas had practically the same temperature as demonstrated by thermography. We found that horseflies spend more time walking on thin black stripes than surrounding grey areas as expected by chance, but only when the substrate is sunlit. This is because the black stripes are warmer than the surrounding grey areas in the sun, but not in the shade. This is consistent with the flies' well-documented attraction to warmer temperatures and provides indirect support for the proposed hypothesis. The frequent false vessel locations at the numerous black-white borderlines, the subsequent painful bitings with unsuccessful blood-sucking attempts and the host's fly-repellent reactions enhance considerably the chance that horseflies cannot evade host responses and are swatted by them. To eliminate this risk, a good evolutionary strategy was the avoidance of striped (and spotted) host animals.
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Affiliation(s)
- Péter Takács
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Dénes Száz
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Miklós Vincze
- MTA-ELTE Theoretical Physics Research Group, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Judit Slíz-Balogh
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Gábor Horváth
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary.
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Navigation and orientation in Coleoptera: a review of strategies and mechanisms. Anim Cogn 2021; 24:1153-1164. [PMID: 33846895 DOI: 10.1007/s10071-021-01513-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 03/30/2021] [Accepted: 04/04/2021] [Indexed: 10/21/2022]
Abstract
Spatial orientation is important for animals to forage, mate, migrate, and escape certain threats, and can require simple to complex cognitive abilities and behaviours. As these behaviours are more difficult to experimentally test in vertebrates, considerable research has focussed on investigating spatial orientation in insects. However, the majority of insect spatial orientation research tends to focus on a few taxa of interest, especially social insects. Beetles present an interesting insect group to study in this respect, due to their diverse taxonomy and biology, and prevalence as agricultural pests. In this article, I review research on beetle spatial orientation. Then, I use this synthesis to discuss mechanisms beetles employ in the context of different behaviours that require orientation or navigation. I conclude by discussing two future avenues for behavioural research on this topic, which could lead to more robust conclusions on how species in this diverse order are able to traverse through a wide variety of environments.
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Heading choices of flying Drosophila under changing angles of polarized light. Sci Rep 2019; 9:16773. [PMID: 31727972 PMCID: PMC6856357 DOI: 10.1038/s41598-019-53330-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/30/2019] [Indexed: 11/14/2022] Open
Abstract
Many navigating insects include the celestial polarization pattern as an additional visual cue to orient their travels. Spontaneous orientation responses of both walking and flying fruit flies (Drosophila melanogaster) to linearly polarized light have previously been demonstrated. Using newly designed modular flight arenas consisting entirely of off-the-shelf parts and 3D-printed components we present individual flying flies with a slow and continuous rotational change in the incident angle of linear polarization. Under such open-loop conditions, single flies choose arbitrary headings with respect to the angle of polarized light and show a clear tendency to maintain those chosen headings for several minutes, thereby adjusting their course to the slow rotation of the incident stimulus. Importantly, flies show the tendency to maintain a chosen heading even when two individual test periods under a linearly polarized stimulus are interrupted by an epoch of unpolarized light lasting several minutes. Finally, we show that these behavioral responses are wavelength-specific, existing under polarized UV stimulus while being absent under polarized green light. Taken together, these findings provide further evidence supporting Drosophila’s abilities to use celestial cues for visually guided navigation and course correction.
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Heinloth T, Uhlhorn J, Wernet MF. Insect Responses to Linearly Polarized Reflections: Orphan Behaviors Without Neural Circuits. Front Cell Neurosci 2018; 12:50. [PMID: 29615868 PMCID: PMC5870057 DOI: 10.3389/fncel.2018.00050] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 02/15/2018] [Indexed: 12/13/2022] Open
Abstract
The e-vector orientation of linearly polarized light represents an important visual stimulus for many insects. Especially the detection of polarized skylight by many navigating insect species is known to improve their orientation skills. While great progress has been made towards describing both the anatomy and function of neural circuit elements mediating behaviors related to navigation, relatively little is known about how insects perceive non-celestial polarized light stimuli, like reflections off water, leaves, or shiny body surfaces. Work on different species suggests that these behaviors are not mediated by the “Dorsal Rim Area” (DRA), a specialized region in the dorsal periphery of the adult compound eye, where ommatidia contain highly polarization-sensitive photoreceptor cells whose receptive fields point towards the sky. So far, only few cases of polarization-sensitive photoreceptors have been described in the ventral periphery of the insect retina. Furthermore, both the structure and function of those neural circuits connecting to these photoreceptor inputs remain largely uncharacterized. Here we review the known data on non-celestial polarization vision from different insect species (dragonflies, butterflies, beetles, bugs and flies) and present three well-characterized examples for functionally specialized non-DRA detectors from different insects that seem perfectly suited for mediating such behaviors. Finally, using recent advances from circuit dissection in Drosophila melanogaster, we discuss what types of potential candidate neurons could be involved in forming the underlying neural circuitry mediating non-celestial polarization vision.
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Affiliation(s)
- Tanja Heinloth
- Division of Neurobiology, Institut für Biology, Fachbereich Biologie, Chemie & Pharmazie, Freie Universität Berlin, Berlin, Germany
| | - Juliane Uhlhorn
- Division of Neurobiology, Institut für Biology, Fachbereich Biologie, Chemie & Pharmazie, Freie Universität Berlin, Berlin, Germany
| | - Mathias F Wernet
- Division of Neurobiology, Institut für Biology, Fachbereich Biologie, Chemie & Pharmazie, Freie Universität Berlin, Berlin, Germany
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Empirical corroboration of an earlier theoretical resolution to the UV paradox of insect polarized skylight orientation. Naturwissenschaften 2014; 101:95-103. [DOI: 10.1007/s00114-013-1134-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 12/17/2013] [Accepted: 12/20/2013] [Indexed: 11/29/2022]
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Schmeling F, Wakakuwa M, Tegtmeier J, Kinoshita M, Bockhorst T, Arikawa K, Homberg U. Opsin expression, physiological characterization and identification of photoreceptor cells in the dorsal rim area and main retina of the desert locust, Schistocerca gregaria. J Exp Biol 2014; 217:3557-68. [DOI: 10.1242/jeb.108514] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
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 a UV-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 coexpressed 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 life style at low light levels. The data support the role of the DRA in polarization vision and suggest trichromatic colour vision in the desert locust.
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Brady P, Cummings M. Differential Response to Circularly Polarized Light by the Jewel Scarab Beetle Chrysina gloriosa. Am Nat 2010; 175:614-20. [DOI: 10.1086/651593] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Seago AE, Brady P, Vigneron JP, Schultz TD. Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera). J R Soc Interface 2008; 6 Suppl 2:S165-84. [PMID: 18957361 DOI: 10.1098/rsif.2008.0354.focus] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Members of the order Coleoptera are sometimes referred to as 'living jewels', in allusion to the strikingly diverse array of iridescence mechanisms and optical effects that have arisen in beetles. A number of novel and sophisticated reflectance mechanisms have been discovered in recent years, including three-dimensional photonic crystals and quasi-ordered coherent scattering arrays. However, the literature on beetle structural coloration is often redundant and lacks synthesis, with little interchange between the entomological and optical research communities. Here, an overview is provided for all iridescence mechanisms observed in Coleoptera. Types of iridescence are illustrated and classified into three mechanistic groups: multilayer reflectors, three-dimensional photonic crystals and diffraction gratings. Taxonomic and phylogenetic distributions are provided, along with discussion of the putative functions and evolutionary pathways by which iridescence has repeatedly arisen in beetles.
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Affiliation(s)
- Ainsley E Seago
- Department of Environmental Science, University of California, Berkeley, CA 94720-3112, USA.
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