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  1. Article ; Online: Polarization vision in terrestrial hermit crabs.

    How, Martin J / Robertson, Alasdair / Smithers, Samuel P / Wilby, David

    Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology

    2023  Volume 209, Issue 6, Page(s) 899–905

    Abstract: Polarization vision is used by a wide range of animals for navigating, orienting, and detecting objects or areas of interest. Shallow marine and semi-terrestrial crustaceans are particularly well known for their abilities to detect predator-like or ... ...

    Abstract Polarization vision is used by a wide range of animals for navigating, orienting, and detecting objects or areas of interest. Shallow marine and semi-terrestrial crustaceans are particularly well known for their abilities to detect predator-like or conspecific-like objects based on their polarization properties. On land, some terrestrial invertebrates use polarization vision for detecting suitable habitats, oviposition sites or conspecifics, but examples of threat detection in the polarization domain are less well known. To test whether this also applies to crustaceans that have evolved to occupy terrestrial habitats, we determined the sensitivity of two species of land and one species of marine hermit crab to predator-like visual stimuli varying in the degree of polarization. All three species showed an ability to detect these cues based on polarization contrasts alone. One terrestrial species, Coenobita rugosus, showed an increased sensitivity to objects with a higher degree of polarization than the background. This is the inverse of most animals studied to date, suggesting that the ecological drivers for polarization vision may be different in the terrestrial environment.
    MeSH term(s) Female ; Animals ; Anomura/physiology ; Ecosystem
    Language English
    Publishing date 2023-04-12
    Publishing country Germany
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 120907-3
    ISSN 1432-1351 ; 0302-9824 ; 0373-0859 ; 0340-7594
    ISSN (online) 1432-1351
    ISSN 0302-9824 ; 0373-0859 ; 0340-7594
    DOI 10.1007/s00359-023-01631-z
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Optical influence of oil droplets on cone photoreceptor sensitivity.

    Wilby, David / Roberts, Nicholas W

    The Journal of experimental biology

    2017  Volume 220, Issue Pt 11, Page(s) 1997–2004

    Abstract: Oil droplets are spherical organelles found in the cone photoreceptors of vertebrates. They are generally assumed to focus incident light into the outer segment, and thereby improve light catch because of the droplets' spherical lens-like shape. However, ...

    Abstract Oil droplets are spherical organelles found in the cone photoreceptors of vertebrates. They are generally assumed to focus incident light into the outer segment, and thereby improve light catch because of the droplets' spherical lens-like shape. However, using full-wave optical simulations of physiologically realistic cone photoreceptors from birds, frogs and turtles, we find that pigmented oil droplets actually drastically reduce the transmission of light into the outer segment integrated across the full visible wavelength range of each species. Only transparent oil droplets improve light catch into the outer segments, and any enhancement is critically dependent on the refractive index, diameter of the oil droplet, and diameter and length of the outer segment. Furthermore, oil droplets are not the only optical elements found in cone inner segments. The ellipsoid, a dense aggregation of mitochondria situated immediately prior to the oil droplet, mitigates the loss of light at the oil droplet surface. We describe a framework for integrating these optical phenomena into simple models of receptor sensitivity, and the relevance of these observations to evolutionary appearance and loss of oil droplets is discussed.
    MeSH term(s) Animals ; Biological Evolution ; Chickens ; Computer Simulation ; Light ; Oils ; Optics and Photonics ; Retinal Cone Photoreceptor Cells/cytology ; Retinal Cone Photoreceptor Cells/physiology ; Turtles ; Vision, Ocular ; Xenopus laevis
    Chemical Substances Oils
    Language English
    Publishing date 2017-03-17
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 218085-6
    ISSN 1477-9145 ; 0022-0949
    ISSN (online) 1477-9145
    ISSN 0022-0949
    DOI 10.1242/jeb.152918
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Spatial summation improves bird color vision in low light intensities.

    Olsson, Peter / Wilby, David / Kelber, Almut

    Vision research

    2017  Volume 130, Page(s) 1–8

    Abstract: Color guides many important behaviors in birds. Previously we have shown that the intensity threshold for color discrimination in the chicken depends on the color contrast between stimuli and their brightness. The birds could discriminate larger color ... ...

    Abstract Color guides many important behaviors in birds. Previously we have shown that the intensity threshold for color discrimination in the chicken depends on the color contrast between stimuli and their brightness. The birds could discriminate larger color contrasts and brighter colors in lower light intensities. We suggested that chickens use spatial summation of cone signals to maintain color vision in low light levels. Here we tested this hypothesis by determining the intensity thresholds of color discrimination using similar stimuli, patterns of grey tiles of varying intensity interspersed with color tiles, adjusted for this specific aim. Chickens could discriminate stimuli with a larger single color tile, or with a larger proportion of small color tiles, in lower light intensities. This is in agreement with the hypothesis that spatial summation improves color discrimination in low light levels. There was no difference in the intensity threshold for discrimination of stimuli with a single 6×6mm color tile, stimuli with 30% colored tiles and stimuli in which color filled the whole pattern. This gives a first indication to the degree of spatial summation that can be performed. We compare this level of spatial summation to predictions from mathematical model calculations.
    MeSH term(s) Animals ; Chickens/physiology ; Color Perception/physiology ; Color Vision/physiology ; Contrast Sensitivity/physiology ; Photic Stimulation ; Retinal Cone Photoreceptor Cells/physiology ; Sensory Thresholds/physiology ; Space Perception/physiology
    Language English
    Publishing date 2017-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 200427-6
    ISSN 1878-5646 ; 0042-6989
    ISSN (online) 1878-5646
    ISSN 0042-6989
    DOI 10.1016/j.visres.2016.10.009
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Losing focus: how lens position and viewing angle affect the function of multifocal lenses in fishes.

    Gagnon, Yakir Luc / Wilby, David / Temple, Shelby Eric

    Journal of the Optical Society of America. A, Optics, image science, and vision

    2016  Volume 33, Issue 9, Page(s) 1901–1909

    Abstract: Light rays of different wavelengths are focused at different distances when they pass through a lens (longitudinal chromatic aberration [LCA]). For animals with color vision this can pose a serious problem, because in order to perceive a sharp image the ... ...

    Abstract Light rays of different wavelengths are focused at different distances when they pass through a lens (longitudinal chromatic aberration [LCA]). For animals with color vision this can pose a serious problem, because in order to perceive a sharp image the rays must be focused at the shallow plane of the photoreceptor's outer segments in the retina. A variety of fish and tetrapods have been found to possess multifocal lenses, which correct for LCA by assigning concentric zones to correctly focus specific wavelengths. Each zone receives light from a specific beam entrance position (BEP) (the lateral distance between incoming light and the center of the lens). Any occlusion of incoming light at specific BEPs changes the composition of the wavelengths that are correctly focused on the retina. Here, we calculated the effect of lens position relative to the plane of the iris and light entering the eye at oblique angles on how much of the lens was involved in focusing the image on the retina (measured as the availability of BEPs). We used rotational photography of fish eyes and mathematical modeling to quantify the degree of lens occlusion. We found that, at most lens positions and viewing angles, there was a decrease of BEP availability and in some cases complete absence of some BEPs. Given the implications of these effects on image quality, we postulate that three morphological features (aphakic spaces, curvature of the iris, and intraretinal variability in spectral sensitivity) may, in part, be adaptations to mitigate the loss of spectral image quality in the periphery of the eyes of fishes.
    Language English
    Publishing date 2016-09-01
    Publishing country United States
    Document type Journal Article
    ZDB-ID 283633-6
    ISSN 1520-8532 ; 1084-7529 ; 0740-3232
    ISSN (online) 1520-8532
    ISSN 1084-7529 ; 0740-3232
    DOI 10.1364/JOSAA.33.001901
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Quantitative studies of animal colour constancy: using the chicken as model.

    Olsson, Peter / Wilby, David / Kelber, Almut

    Proceedings. Biological sciences

    2016  Volume 283, Issue 1830

    Abstract: Colour constancy is the capacity of visual systems to keep colour perception constant despite changes in the illumination spectrum. Colour constancy has been tested extensively in humans and has also been described in many animals. In humans, colour ... ...

    Abstract Colour constancy is the capacity of visual systems to keep colour perception constant despite changes in the illumination spectrum. Colour constancy has been tested extensively in humans and has also been described in many animals. In humans, colour constancy is often studied quantitatively, but besides humans, this has only been done for the goldfish and the honeybee. In this study, we quantified colour constancy in the chicken by training the birds in a colour discrimination task and testing them in changed illumination spectra to find the largest illumination change in which they were able to remain colour-constant. We used the receptor noise limited model for animal colour vision to quantify the illumination changes, and found that colour constancy performance depended on the difference between the colours used in the discrimination task, the training procedure and the time the chickens were allowed to adapt to a new illumination before making a choice. We analysed literature data on goldfish and honeybee colour constancy with the same method and found that chickens can compensate for larger illumination changes than both. We suggest that future studies on colour constancy in non-human animals could use a similar approach to allow for comparison between species and populations.
    MeSH term(s) Animals ; Bees ; Chickens/physiology ; Color Perception ; Color Vision ; Goldfish ; Lighting ; Photic Stimulation
    Language English
    Publishing date 2016-05-12
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 209242-6
    ISSN 1471-2954 ; 0080-4649 ; 0962-8452 ; 0950-1193
    ISSN (online) 1471-2954
    ISSN 0080-4649 ; 0962-8452 ; 0950-1193
    DOI 10.1098/rspb.2016.0411
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Using micro-CT techniques to explore the role of sex and hair in the functional morphology of bumblebee (Bombus terrestris) ocelli.

    Wilby, David / Aarts, Tobio / Tichit, Pierre / Bodey, Andrew / Rau, Christoph / Taylor, Gavin / Baird, Emily

    Vision research

    2019  Volume 158, Page(s) 100–108

    Abstract: Many insects have triplets of camera type eyes, called ocelli, whose function remains unclear for most species. Here, we investigate the ocelli of the bumblebee, Bombus terrestris, using reconstructed 3D data from X-ray microtomography scans combined ... ...

    Abstract Many insects have triplets of camera type eyes, called ocelli, whose function remains unclear for most species. Here, we investigate the ocelli of the bumblebee, Bombus terrestris, using reconstructed 3D data from X-ray microtomography scans combined with computational ray-tracing simulations. This method enables us, not only to predict the visual fields of the ocelli, but to explore for the first time the effect that hair has on them as well as the difference between worker female and male ocelli. We find that bumblebee ocellar fields of view are directed forward and dorsally, incorporating the horizon as well as the sky. There is substantial binocular overlap between the median and lateral ocelli, but no overlap between the two lateral ocelli. Hairs in both workers and males occlude the ocellar field of view, mostly laterally in the worker median ocellus and dorsally in the lateral ocelli. There is little to no sexual dimorphism in the ocellar visual field, suggesting that in B. terrestris they confer no advantage to mating strategies. We compare our results with published observations for the visual fields of compound eyes in the same species as well as with the ocellar vision of other bee and insect species.
    MeSH term(s) Animals ; Bees/physiology ; Bees/ultrastructure ; Female ; Hair/physiology ; Male ; Photoreceptor Cells, Invertebrate/cytology ; Photoreceptor Cells, Invertebrate/ultrastructure ; Sex Factors ; Vision, Ocular/physiology ; Visual Fields/physiology ; X-Ray Microtomography
    Language English
    Publishing date 2019-03-07
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 200427-6
    ISSN 1878-5646 ; 0042-6989
    ISSN (online) 1878-5646
    ISSN 0042-6989
    DOI 10.1016/j.visres.2019.02.008
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Selection of the intrinsic polarization properties of animal optical materials creates enhanced structural reflectivity and camouflage.

    Feller, Kathryn D / Jordan, Thomas M / Wilby, David / Roberts, Nicholas W

    Philosophical transactions of the Royal Society of London. Series B, Biological sciences

    2017  Volume 372, Issue 1724

    Abstract: Many animals use structural coloration to create bright and conspicuous visual signals. Selection of the size and shape of the optical structures animals use defines both the colour and intensity of the light reflected. The material used to create these ... ...

    Abstract Many animals use structural coloration to create bright and conspicuous visual signals. Selection of the size and shape of the optical structures animals use defines both the colour and intensity of the light reflected. The material used to create these reflectors is also important; however, animals are restricted to a limited number of materials: commonly chitin, guanine and the protein, reflectin. In this work we highlight that a particular set of material properties can also be under selection in order to increase the optical functionality of structural reflectors. Specifically, polarization properties, such as birefringence (the difference between the refractive indices of a material) and chirality (which relates to molecular asymmetry) are both under selection to create enhanced structural reflectivity. We demonstrate that the structural coloration of the gold beetle
    MeSH term(s) Animals ; Birefringence ; Chitin/chemistry ; Coleoptera/chemistry ; Coleoptera/physiology ; Color ; Fishes/physiology ; Guanine/chemistry ; Stereoisomerism
    Chemical Substances Chitin (1398-61-4) ; Guanine (5Z93L87A1R)
    Language English
    Publishing date 2017-05-22
    Publishing country England
    Document type Journal Article
    ZDB-ID 208382-6
    ISSN 1471-2970 ; 0080-4622 ; 0264-3839 ; 0962-8436
    ISSN (online) 1471-2970
    ISSN 0080-4622 ; 0264-3839 ; 0962-8436
    DOI 10.1098/rstb.2016.0336
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Hermit crabs (

    Wilby, David / Riches, Samuel / Daly, Ilse M / Bird, Andrew / Wheelwright, Matthew / Foster, James J

    The Journal of experimental biology

    2018  Volume 221, Issue Pt 13

    Abstract: Animals can make use of camouflage to reduce the likelihood of visual detection or recognition and thus improve their chances of survival. Background matching, where body colouration is closely matched to the surrounding substrate, is one form of ... ...

    Abstract Animals can make use of camouflage to reduce the likelihood of visual detection or recognition and thus improve their chances of survival. Background matching, where body colouration is closely matched to the surrounding substrate, is one form of camouflage. Hermit crabs have the opportunity to choose their camouflage independently of body colouration as they inhabit empty gastropod shells, making them ideal to study their choice of camouflage. We used 3D-printed artificial shells of varying contrasts against a grey substrate to test whether hermit crabs prefer shells that they perceive as less conspicuous. Contrast-minimising shells were chosen for Weber contrasts stronger than -0.5. However, in looming experiments, animals responded to contrasts as weak as -0.2, indicating that while they can detect differences between shells and the background, they are only motivated to move into those shells when the alternatives contrast strongly. This suggests a trade-off between camouflage and vulnerability introduced by switching shells.
    MeSH term(s) Animal Shells ; Animals ; Anomura/physiology ; Biological Mimicry/physiology ; Male ; Printing, Three-Dimensional ; Visual Perception
    Language English
    Publishing date 2018-07-04
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 218085-6
    ISSN 1477-9145 ; 0022-0949
    ISSN (online) 1477-9145
    ISSN 0022-0949
    DOI 10.1242/jeb.173831
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Long-Wavelength Reflecting Filters Found in the Larval Retinas of One Mantis Shrimp Family (Nannosquillidae).

    Feller, Kathryn D / Wilby, David / Jacucci, Gianni / Vignolini, Silvia / Mantell, Judith / Wardill, Trevor J / Cronin, Thomas W / Roberts, Nicholas W

    Current biology : CB

    2019  Volume 29, Issue 18, Page(s) 3101–3108.e4

    Abstract: Both vertebrates and invertebrates commonly exploit photonic structures adjacent to their photoreceptors for visual benefits. For example, use of a reflecting structure (tapetum) behind the retina increases photon capture, enhancing vision in dim light [ ... ...

    Abstract Both vertebrates and invertebrates commonly exploit photonic structures adjacent to their photoreceptors for visual benefits. For example, use of a reflecting structure (tapetum) behind the retina increases photon capture, enhancing vision in dim light [1-5]. Colored filters positioned lateral or distal to a photoreceptive unit may also be used to tune spectral sensitivity by selective transmission of wavelengths not absorbed or scattered by the filters [6-8]. Here we describe a new category of biological optical filter that acts simultaneously as both a transmissive spectral filter and narrowband reflector. Discovered in the larval eyes of only one family of mantis shrimp (stomatopod) crustaceans (Nannosquillidae), each crystalline structure bisects the photoreceptive rhabdom into two tiers and contains an ordered array of membrane-bound vesicles with sub-wavelength diameters of 153 ± 5 nm. Axial illumination of the intrarhabdomal structural reflector (ISR) in vivo produces a narrow band of yellow reflectance (mean peak reflectivity, 572 ± 18 nm). The ISR is similar to several synthetic devices, such as bandgap filters, laser mirrors, and (in particular) fiber Bragg gratings used in optical sensors for a wide range of industries. To our knowledge, the stomatopod larval ISR is the first example of a naturally occurring analog to these human-made devices. Considering what is known about these animals' visual ecology, we propose that these reflecting filters may help improve the detection of pelagic bioluminescence in shallow water at night. VIDEO ABSTRACT.
    MeSH term(s) Animals ; Compound Eye, Arthropod/anatomy & histology ; Compound Eye, Arthropod/physiology ; Crustacea ; Larva/metabolism ; Larva/physiology ; Light ; Photoreceptor Cells/metabolism ; Photoreceptor Cells/physiology ; Photoreceptor Cells, Invertebrate/metabolism ; Photoreceptor Cells, Invertebrate/physiology ; Retina/pathology ; Retina/physiology ; Ultraviolet Rays ; Vision, Ocular/physiology
    Language English
    Publishing date 2019-08-29
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1071731-6
    ISSN 1879-0445 ; 0960-9822
    ISSN (online) 1879-0445
    ISSN 0960-9822
    DOI 10.1016/j.cub.2019.07.070
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  10. Article ; Online: Correction to: Polarisation vision: overcoming challenges of working with a property of light we barely see.

    Foster, James J / Temple, Shelby E / How, Martin J / Daly, Ilse M / Sharkey, Camilla R / Wilby, David / Roberts, Nicholas W

    Die Naturwissenschaften

    2018  Volume 105, Issue 5-6, Page(s) 32

    Abstract: In "Polarisation vision: overcoming challenges of working with a property of light we barely see" (Foster et al. 2018) we provide a basic description of how Stokes parameters can be estimated and used to calculate the angle of polarisation (AoP). ...

    Abstract In "Polarisation vision: overcoming challenges of working with a property of light we barely see" (Foster et al. 2018) we provide a basic description of how Stokes parameters can be estimated and used to calculate the angle of polarisation (AoP).
    Language English
    Publishing date 2018-05-03
    Publishing country Germany
    Document type Published Erratum
    ZDB-ID 123257-5
    ISSN 1432-1904 ; 0028-1042
    ISSN (online) 1432-1904
    ISSN 0028-1042
    DOI 10.1007/s00114-018-1559-8
    Database MEDical Literature Analysis and Retrieval System OnLINE

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