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  • 1
    Online-Ressource
    Online-Ressource
    The Royal Society ; 2012
    In:  Journal of The Royal Society Interface Vol. 9, No. 77 ( 2012-12-07), p. 3338-3350
    In: Journal of The Royal Society Interface, The Royal Society, Vol. 9, No. 77 ( 2012-12-07), p. 3338-3350
    Kurzfassung: Light absorption by carotenoids is known to vary substantially with the shape or conformation of the pigment molecule induced by the molecular environment, but the role of interactions between carotenoid pigments and the proteins to which they are bound, and the resulting impact on organismal coloration, remain unclear. Here, we present a spectroscopic investigation of feathers from the brilliant red scarlet ibis ( Eudocimus ruber, Threskiornithidae), the orange-red summer tanager ( Piranga rubra, Cardinalidae) and the violet-purple feathers of the white-browed purpletuft ( Iodopleura isabellae, Tityridae). Despite their striking differences in colour, all three of these feathers contain canthaxanthin (β,β-carotene-4,4′-dione) as their primary pigment. Reflectance and resonance Raman (rR) spectroscopy were used to investigate the induced molecular structural changes and carotenoid–protein interactions responsible for the different coloration in these plumage samples. The results demonstrate a significant variation between species in the peak frequency of the strong ethylenic vibration ( ν 1 ) peak in the rR spectra, the most significant of which is found in I. isabellae feathers and is correlated with a red-shift in canthaxanthin absorption that results in violet reflectance. Neither polarizability of the protein environment nor planarization of the molecule upon binding can entirely account for the full extent of the colour shift. Therefore, we suggest that head-to-tail molecular alignment (i.e. J-aggregation) of the protein-bound carotenoid molecules is an additional factor.
    Materialart: Online-Ressource
    ISSN: 1742-5689 , 1742-5662
    Sprache: Englisch
    Verlag: The Royal Society
    Publikationsdatum: 2012
    ZDB Id: 2156283-0
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 226, No. 7 ( 2023-04-01)
    Kurzfassung: The Australian lycaenid butterfly Jalmenus evagoras has iridescent wings that are sexually dimorphic, spectrally and in their degree of polarization, suggesting that these properties are likely to be important in mate recognition. We first describe the results of a field experiment showing that free-flying individuals of J. evagoras discriminate between visual stimuli that vary in polarization content in blue wavelengths but not in others. We then present detailed reflectance spectrophotometry measurements of the polarization content of male and female wings, showing that female wings exhibit blue-shifted reflectance, with a lower degree of polarization relative to male wings. Finally, we describe a novel method for measuring alignment of ommatidial arrays: by measuring variation of depolarized eyeshine intensity from patches of ommatidia as a function of eye rotation, we show that (a) individual rhabdoms contain mutually perpendicular microvilli; (b) many rhabdoms in the array have their microvilli misaligned with respect to neighboring rhabdoms by as much as 45 deg; and (c) the misaligned ommatidia are useful for robust polarization detection. By mapping the distribution of the ommatidial misalignments in eye patches of J. evagoras, we show that males and females exhibit differences in the extent to which ommatidia are aligned. Both the number of misaligned ommatidia suitable for robust polarization detection and the number of aligned ommatidia suitable for edge detection vary with respect to both sex and eye patch elevation. Thus, J. evagoras exhibits finely tuned ommatidial arrays suitable for perception of polarized signals, likely to match sex-specific life history differences in the utility of polarized signals.
    Materialart: Online-Ressource
    ISSN: 0022-0949 , 1477-9145
    Sprache: Englisch
    Verlag: The Company of Biologists
    Publikationsdatum: 2023
    ZDB Id: 1482461-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    American Association for the Advancement of Science (AAAS) ; 2017
    In:  Science Vol. 356, No. 6344 ( 2017-06-23), p. 1249-1254
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 356, No. 6344 ( 2017-06-23), p. 1249-1254
    Kurzfassung: Avian egg shape is generally explained as an adaptation to life history, yet we currently lack a global synthesis of how egg-shape differences arise and evolve. Here, we apply morphometric, mechanistic, and macroevolutionary analyses to the egg shapes of 1400 bird species. We characterize egg-shape diversity in terms of two biologically relevant variables, asymmetry and ellipticity, allowing us to quantify the observed morphologies in a two-dimensional morphospace. We then propose a simple mechanical model that explains the observed egg-shape diversity based on geometric and material properties of the egg membrane. Finally, using phylogenetic models, we show that egg shape correlates with flight ability on broad taxonomic scales, suggesting that adaptations for flight may have been critical drivers of egg-shape variation in birds.
    Materialart: Online-Ressource
    ISSN: 0036-8075 , 1095-9203
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2017
    ZDB Id: 128410-1
    ZDB Id: 2066996-3
    ZDB Id: 2060783-0
    SSG: 11
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2018
    In:  Nature Communications Vol. 9, No. 1 ( 2018-12-18)
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2018-12-18)
    Kurzfassung: Many animal signals are complex, often combining multimodal components with dynamic motion. To understand the function and evolution of these displays, it is vital to appreciate their spatiotemporal organization. Male broad-tailed hummingbirds ( Selasphorus platycercus ) perform dramatic U-shaped courtship dives over females, appearing to combine rapid movement and dive-specific mechanical noises with visual signals from their iridescent gorgets. To understand how motion, sound and color interact in these spectacular displays, we obtained video and audio recordings of dives performed by wild hummingbirds. We then applied a multi-angle imaging technique to estimate how a female would perceive the male’s iridescent gorget throughout the dive. We show that the key physical, acoustic and visual aspects of the dive are remarkably synchronized—all occurring within 300 milliseconds. Our results highlight the critical importance of accounting for motion and orientation when investigating animal displays: speed and trajectory affect how multisensory signals are produced and perceived.
    Materialart: Online-Ressource
    ISSN: 2041-1723
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2018
    ZDB Id: 2553671-0
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    The Royal Society ; 2019
    In:  Interface Focus Vol. 9, No. 1 ( 2019-02-06), p. 20180053-
    In: Interface Focus, The Royal Society, Vol. 9, No. 1 ( 2019-02-06), p. 20180053-
    Kurzfassung: The use of artificially coloured stimuli, especially to test hypotheses about sexual selection and anti-predator defence, has been common in behavioural ecology since the pioneering work of Tinbergen. To investigate the effects of colour on animal behaviour, many researchers use paints, markers and dyes to modify existing colours or to add colour to synthetic models. Because colour perception varies widely across species, it is critical to account for the signal receiver's vision when performing colour manipulations. To explore this, we applied 26 typical coloration products to different types of avian feathers. Next, we measured the artificially coloured feathers using two complementary techniques—spectrophotometry and digital ultraviolet--visible photography—and modelled their appearance to mammalian dichromats (ferret, dog), trichromats (honeybee, human) and avian tetrachromats (hummingbird, blue tit). Overall, artificial colours can have dramatic and sometimes unexpected effects on the reflectance properties of feathers, often differing based on feather type. The degree to which an artificial colour differs from the original colour greatly depends on an animal's visual system. ‘White’ paint to a human is not ‘white’ to a honeybee or blue tit. Based on our analysis, we offer practical guidelines for reducing the risk of introducing unintended effects when using artificial colours in behavioural experiments.
    Materialart: Online-Ressource
    ISSN: 2042-8898 , 2042-8901
    Sprache: Englisch
    Verlag: The Royal Society
    Publikationsdatum: 2019
    ZDB Id: 2585655-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2016
    In:  Scientific Reports Vol. 6, No. 1 ( 2016-09-12)
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 6, No. 1 ( 2016-09-12)
    Kurzfassung: Animals achieve camouflage through a variety of mechanisms, of which background matching and disruptive coloration are likely the most common. Although many studies have investigated camouflage mechanisms using artificial stimuli and in lab experiments, less work has addressed camouflage in the wild. Here we examine egg camouflage in clutches laid by ground-nesting Snowy Plovers Charadrius nivosus and Least Terns Sternula antillarum breeding in mixed aggregations at Bahía de Ceuta, Sinaloa, Mexico. We obtained digital images of clutches laid by both species. We then calibrated the images and used custom computer software and edge detection algorithms to quantify measures related to three potential camouflage mechanisms: pattern complexity matching, disruptive effects and background color matching. Based on our image analyses, Snowy Plover clutches, in general, appeared to be more camouflaged than Least Tern clutches. Snowy Plover clutches also survived better than Least Tern clutches. Unexpectedly, variation in clutch survival was not explained by any measure of egg camouflage in either species. We conclude that measures of egg camouflage are poor predictors of clutch survival in this population. The behavior of the incubating parents may also affect clutch predation. Determining the significance of egg camouflage requires further testing using visual models and behavioral experiments.
    Materialart: Online-Ressource
    ISSN: 2045-2322
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2016
    ZDB Id: 2615211-3
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2009
    In:  International Journal of Primatology Vol. 30, No. 6 ( 2009-12), p. 893-917
    In: International Journal of Primatology, Springer Science and Business Media LLC, Vol. 30, No. 6 ( 2009-12), p. 893-917
    Materialart: Online-Ressource
    ISSN: 0164-0291 , 1573-8604
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2009
    ZDB Id: 2016016-1
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    Online-Ressource
    Online-Ressource
    Oxford University Press (OUP) ; 2011
    In:  Behavioral Ecology Vol. 22, No. 5 ( 2011-09-01), p. 1042-1052
    In: Behavioral Ecology, Oxford University Press (OUP), Vol. 22, No. 5 ( 2011-09-01), p. 1042-1052
    Materialart: Online-Ressource
    ISSN: 1465-7279 , 1045-2249
    RVK:
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2011
    ZDB Id: 1496189-1
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Online-Ressource
    Online-Ressource
    Oxford University Press (OUP) ; 2016
    In:  Behavioral Ecology Vol. 27, No. 3 ( 2016), p. e6-e7
    In: Behavioral Ecology, Oxford University Press (OUP), Vol. 27, No. 3 ( 2016), p. e6-e7
    Materialart: Online-Ressource
    ISSN: 1045-2249 , 1465-7279
    RVK:
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2016
    ZDB Id: 1496189-1
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    Online-Ressource
    Online-Ressource
    Oxford University Press (OUP) ; 2020
    In:  The Condor Vol. 122, No. 4 ( 2020-12-31)
    In: The Condor, Oxford University Press (OUP), Vol. 122, No. 4 ( 2020-12-31)
    Materialart: Online-Ressource
    ISSN: 0010-5422 , 1938-5129
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2020
    ZDB Id: 215921-1
    ZDB Id: 2066173-3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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