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65 results for “iridescence”
Data and code from: Evolution of brilliant iridescent feather nanostructures
<p>The brilliant iridescent plumage of birds creates some of the most stunning color displays known in the natural world. Iridescent plumage colors are produced by nanostructures in feathers and have evolved in a wide variety of birds. The building blocks of these structures—melanosomes (melanin-filled organelles)—come in a variety of forms, yet how these different forms contribute to color production across birds remains unclear. Here, we leverage evolutionary analyses, optical simulations and reflectance spectrophotometry to uncover general principles that govern the production of brilliant iridescence. We find that a key feature that unites all melanosome forms in brilliant iridescent structures is thin melanin layers. Birds have achieved this in multiple ways: by decreasing the size of the melanosome directly, by hollowing out the interior, or by flattening the melanosome into a platelet. The evolution of thin melanin layers unlocks color-producing possibilities, more than doubling the range of colors that can be produced with a thick melanin layer and simultaneously increasing brightness. We discuss the implications of these findings for the evolution of iridescent structures in birds and propose two evolutionary paths to brilliant iridescence.</p>
Data from: Iridescence untwined - Honey bees can separate hue variations in space and time
<p><span>Iridescence is a phenomenon whereby the hue of a surface changes with viewing or illumination angle. Many animals display iridescence but it currently remains unclear whether relevant observers process iridescent color signals as a complex collection of colors (spatial variation), or as moving patterns of colors and shapes (temporal variation). This is important as animals may use only the spatial or temporal component of the signal, although this possibility has rarely been considered or tested. Here, we investigated whether honey bees could separate the temporal and spatial components of iridescence by training them to discriminate between iridescent disks and photographic images of the iridescent patterns presented by the disks. Both stimuli therefore contained spatial color variation, but the photographic stimuli do not change in hue with varying angle (no temporal variation). We found that individual bee observers could discriminate the variable patterns of iridescent disks from static photographs during unrewarded tests. Control experiments showed that bees reliably discriminated iridescent disks from control silver disks, showing that bees were processing chromatic cues. These results suggest that honey bees could selectively choose to attend to the temporal component of iridescence signals to make accurate decisions. </span></p>
Fig. 4 in Iridescent plumage in a juvenile dromaeosaurid theropod dinosaur
Fig. 4. Reconstruction of the dromaeosaurid dinosaur Wulong bohaiensis Poust, Gao, Varricchio, Wu, and Zhang, 2020 (DNHM D2933), from Shangheshou, Chaoyang, Liaoning, China, Early Cretaceous Jiufotang Formation with a minimum age of 120.3 Ma. This illustration broadly depicts iridescent plumage on the limbs and grey feathers on the body. It should be noted that the full extent of the iridescence has been extrapolated in the creation of this illustration, based on the evidence provided by a small but significant distribution of iridescent samples across several limbs of the fossil. Artwork by Robert Nicholls (Bob Nicholls Art).
Fig. 2 in Iridescent plumage in a juvenile dromaeosaurid theropod dinosaur
Fig. 2. Preserved melanosome imprints characteristic of each sample from the dromaeosaurid dinosaur Wulong bohaiensis Poust, Gao, Varricchio, Wu, and Zhang, 2020 (DNHM D9233) from Shangheshou, Chaoyang, Liaoning, China, Early Cretaceous Jiufotang Formation with a minimum age of 120.3 Ma. All melanosome imprints are from solid and cylindrical melanosomes. Preservation on samples 7 and 14 is less clear. Three distinctive types of melanosome morphology were found on sample 15. Each was measured separately and treated as different samples for analysis (15a/15b/15c).
Fig. 3 in Iridescent plumage in a juvenile dromaeosaurid theropod dinosaur
Fig. 3. Melanosome length against diameter for each colour category. The fifth panel shows the measurements for the dromaeosaurid dinosaur Wulong bohaiensis Poust, Gao, Varricchio, Wu, and Zhang, 2020 (DNHM D2933), from Shangheshou, Chaoyang, Liaoning, China, Early Cretaceous Jiufotang Formation with a minimum age of 120.3 Ma. Note 15c, which outlies all extant measurements. This figure is a good visual representation of why the models conflict in their prediction for 15c. cluded in SOM: table S2. Sample 15 is from the chest region Colour prediction.—In this study, the two prevailing preof the abdomen. Multiple unique populations of melano- dictive modelling approaches (QDA and MLR) for analysing somes were observed with differing morphologies. These fossil melanosome shape were applied to each of the datawere treated as separate samples (15a, 15b, and 15c) and sets (see Table 1), using length, diameter and aspect ratio as assessed for their colour. Fig. 3 plots length against diam- predictor variables for the QDA. For MLR, diameter, aspect eter for the melanosome data, with the right-most panel in- ratio, hollowness (categorical) and flatness (categorical) precluding the measurements from Wulong bohaiensis DNHM dictor variables were used. The analyses were conducted in D2933 facilitating visual comparison of the colour category Stata-16 (StataCorp 2019a), see SOM for commands to exedistributions in the first four panels. cute the models and justifications for the variable selection. Accounting for melanosome shrinkage.—Only melanosome The first dataset "LiNord" incorporates the Nordén et al. imprints were available for study, which have been argued (2019) modifications of the original Li et al. (2012) dataset to preserve the original morphology better than organically where, to avoid systematic bias from different sampling preserved melanosomes (Vinther 2020). Organically pre- methods and sample sizes, coefficient of variation and skew served melanosomes appear to shrink isometrically up to variables were excluded, as well as all samples with a sam- ~20% (McNamara et al. 2013; Colleary et al. 2015). The ple size less than 10. It does not include any of the new addiassumption is that if the rock matrix formed earlier than the tional samples from Hu et al. (2018) or Nordén et al. (2019). diagenetic shrinkage taking place, then imprints are a better The second dataset "NordSC" is a revised version of the proxy for the original size. While aspect ratio is unaffected expanded Nordén et al. (2019) dataset. First, a minor correcby shrinkage, the length and diameter would be affected tion reassigned colour categories to four samples that were and could affect predictions. To inspect this effect, three mislabelled (see SOM). Nordén et al. (2019) also excluded the scaling compensations of 10%, 20%, and 30% for length species sampled by Hu et al. (2018) because the data was not and diameter have been applied to investigate any possible phylogenetically broad, instead creating their own, broader shift in prediction. iridescent dataset. Additionally, here all hollow and flat sam-
Fig. 5 in Iridescent plumage in a juvenile dromaeosaurid theropod dinosaur
Fig. 5. Variation of probability with respect to the aspect ratio predictor variable (one of the two variables included in analysis M2). This plot shows that at aspect ratios of approximately 2.5–3.5, the probabilities of predicting any of the four possible colour categories are similar, and none are very likely. Several samples in Wulong bohaiensis (DNHM D2933) had an aspect ratio within this range.
Fig. 1 in Iridescent plumage in a juvenile dromaeosaurid theropod dinosaur
Fig. 1. Dromaeosaurid dinosaur Wulong bohaiensis Poust, Gao, Varricchio, Wu, and Zhang, 2020 (DNHM D2933), from Shangheshou, Chaoyang, Liaoning, China, Early Cretaceous Jiufotang Formation with a minimum age of 120.3 Ma (A1). Samples 1–16 were labelled by SLB while taking samples at the museum. Illustration by JV (A2) to show distinct plumage groupings on Wulong bohaiensis (DNHM D2933). For clarity, in this illustration only the samples with successful melanosome preservation are labelled. Preservation on each of the excluded samples was not sufficient for study.
Data and code from: Evolution of brilliant iridescent feather nanostructures
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Data from: Iridescence untwined - Honey bees can separate hue variations in space and time
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Feather iridescence of Coeligena hummingbird species varies due to differently organized barbs and barbules
<p>Hummingbirds are perhaps the most exquisite bird species because of their prominent iridescence, created by stacks of melanosomes in the feather barbules. The feather colours crucially depend on the nanoscopic dimensions of the melanosome, and the displayed iridescence can distinctly vary, dependent on the spatial organization of the barbs and barbules. We have taken the genus Coeligena as a model group, with species having feathers that strongly vary in their spatial reflection properties. We studied the feather morphology and the optical characteristics. We found that the coloration of Coeligena hummingbirds depends on both the Venetian-blind-like arrangement of the barbules and the V-shaped, angular arrangement of the barbules at opposite sides of the barbs. Both the nanoscopic and microscopic organization of the hummingbird feather components determine the bird's macroscopical appearance.</p>
Syngnathus scovelli band iridescence measurements
<p>This is the raw data that corresponds to the manuscript "The development of a quantification method for measuring iridescence using sexually selected traits in the Gulf pipefish (<em>Syngnathus scovelli</em>)" (DOI: <a href="https://doi.org/10.3389/fmars.2023.1127790">10.3389/fmars.2023.1127790</a>). The two datasets contain the iridescence measurements for each individual band on the pipefish for each study outlined in the manuscript.</p> <ol> <li><strong>iridescence_across_lighting_RAW</strong>: contains every iridescence measurements for the study about lighting conditions, to see if lighting has any affect on the amount of iridescence measured from a photo.</li> <li><strong>pipefish_measures_iridescence_RAW</strong>: contatins all of the other iridescence measurements for the geographic study, for females from two Texas populations and two Florida populations, and the estrogen study, where we measured the development of iridescence on male pipefish in response to synthetic estrogen.</li> </ol>
Evolutionary history and analysis of iridescent ultraviolet butterfly scales
<p>Iridescent ultraviolet (IUV) patterns on pierid butterfly wings are phenotypic adaptations commonly used as sexual signals, generated by scales with ultrastructural modifications. Pierid IUV patterns are sexually dichromatic, with reduced size in females, where conspicuous sexual signaling balances courtship against ecological predation. There have been no phylogenetic reconstructions of IUV within Pieridae and little morphological characterization of phenotypic diversity. Our genus-wide characterization of IUV revealed the uniform similarity of stacked lamellar ridges on the dorsal surface of cover scales. We tested a hypothesis of single versus multiple origins by reconstructing a phylogeny of 534 species (~43.2% described species), with all genera represented, and a trait matrix of 734 species (~59.4%) screened for IUV. A single, early dimorphic origin of IUV followed by several losses and gains received strong support, concluding that IUV patterns and structural coloration are old traits. Collectively, these results support the homology of IUV scales and patterns that diversified within several lineages, suggesting an interplay between female-mediated sexual selection and ecological predatory selection.</p>
A genetic switch for male UV-iridescence in an incipient species pair
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Evolutionary history and analysis of iridescent ultraviolet butterfly scales
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Feather iridescence of Coeligena hummingbird species varies due to differently organized barbs and barbules
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Data from: <em>Araucan</em> regulates butterfly wing iridescence by coordinating scale structure and pigmentation
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Data from: Interspecific covariation in courtship displays, iridescent plumage, solar orientation, and their interactions in hummingbirds
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Data from: Biomimicry of iridescent, patterned insect cuticles: comparison of biological and synthetic, cholesteric microcells using hyperspectral imaging
<p>Biological systems inspire the design of multifunctional materials and devices. However, current syynthetic replicas rarelyy capture the range of structural complexityy observed in natural materials. Prior to the definition of a biomimetic design, a dual investigation with a common set of criteria for comparing the biological material and the replica is required. Here, we deal with this issue by addressing the non-trivial case of insect cuticles tessellated with polygonal microcells with iridescent colors due to the twisted cholesteric organization of chitin fibers. By using hyperspectral imaging within a common methodology, we compare, at several length scales, the textural, structural and spectral properties of the microcells found in the two-band cuticle of the scarab beetle <i>Chrysina gloriosa</i> with those of the polygonal texture formed in flat films of cholesteric liquid crystal oligomers. The hyperspectral imaging technique offers a unique opportunity to reveal the common features and differences in the spectral-spatial signatures of biological and synthetic samples at a 6-nm spectral resolution over 400 nm-1000 nm and a spatial resolution of 150 nm. The biomimetic design of chiral tessellations is relevant to the field of non-specular properties such as deflection and lensing in geometric phase planar optics.</p>
Data from: A reliable technique to quantify the individual variability of iridescent coloration in birds
The study of iridescent coloration in birds emerged only recently, mainly due to the difficulty inherent in quantifying its directionality. Directionality restrains color perception to a limited angle and thereby causes drastic changes in brightness when an animal is in motion. Although a versatile goniometer for quantifying iridescent coloration has been developed recently, so far, it has only been applied to measuring the highly directional iridescent coloration in a hummingbird species. Thus, the reliability of the goniometer for species displaying more common and less directional iridescent coloration has yet to be evaluated. Additionally, two important methodological aspects remain to be assessed before this apparatus can be used confidently: 1) whether directionality, which could be subject to sexual selection, can be quantified in a repeatable way; and 2) whether the apparatus gives more precise and accurate measurements than a less complex traditional method. Using feathers collected from 271 male tree swallows Tachycineta bicolor over two years, we found that the goniometer provided repeatable measurements of directionality across individuals and across three body regions, namely the crown, mantle and rump. The apparatus was also more repeatable than a traditional method involving a bifurcated probe and reduced a brightness bias associated with individual differences in barbule tilt. We strongly encourage researchers to invest in this methodological change considering the multiple advantages demonstrated and to quantify the directionality of iridescent coloration as to unveil its role in signaling and sexual selection.
Fig. 4 in Microanatomy and evolution of the nanostructures responsible for iridescent coloration in Trogoniformes (Aves)
Fig. 4 Iridescence-producing nanostructures at 8000× magnification. a Apaloderma vittatum. b Apaloderma narina. c Harpactes oreskios. d Harpactes diardii. e Harpactes ardens. f Euptilotis neoxenus. g
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