The study of color patterns in the animal integument is a fundamental question in biology, with many lepidopteran species being exemplary models in this endeavor due to their relative simplicity and ...elegance. While significant advances have been made in unraveling the cellular and molecular basis of lepidopteran pigmentary coloration, the morphogenesis of wing scale nanostructures involved in structural color production is not well understood. Contemporary research on this topic largely focuses on a few nymphalid model taxa (e.g.,
Bicyclus
,
Heliconius
), despite an overwhelming diversity in the hierarchical nanostructural organization of lepidopteran wing scales. Here, we present a time-resolved, comparative developmental study of hierarchical scale nanostructures in
Parides eurimedes
and five other papilionid species. Our results uphold the putative conserved role of F-actin bundles in acting as spacers between developing ridges, as previously documented in several nymphalid species. Interestingly, while ridges are developing in
P. eurimedes
, plasma membrane manifests irregular mesh-like crossribs characteristic of Papilionidae, which delineate the accretion of cuticle into rows of planar disks in between ridges. Once the ridges have grown, disintegrating F-actin bundles appear to reorganize into a network that supports the invagination of plasma membrane underlying the disks, subsequently forming an extruded honeycomb lattice. Our results uncover a previously undocumented role for F-actin in the morphogenesis of complex wing scale nanostructures, likely specific to Papilionidae.
Complex three-dimensional biophotonic nanostructures produce the vivid structural colors of many butterfly wing scales, but their exact nanoscale organization is uncertain. We used small angle X-ray ...scattering (SAXS) on single scales to characterize the 3D photonic nanostructures of five butterfly species from two families (Papilionidae, Lycaenidae). We identify these chitin and air nanostructures as single network gyroid (I4₁32) photonic crystals. We describe their optical function from SAXS data and photonic band-gap modeling. Butterflies apparently grow these gyroid nanostructures by exploiting the self-organizing physical dynamics of biological lipid-bilayer membranes. These butterfly photonic nanostructures initially develop within scale cells as a core-shell double gyroid (Ia3d), as seen in block-copolymer systems, with a pentacontinuous volume comprised of extracellular space, cell plasma membrane, cellular cytoplasm, smooth endoplasmic reticulum (SER) membrane, and intra-SER lumen. This double gyroid nanostructure is subsequently transformed into a single gyroid network through the deposition of chitin in the extracellular space and the degeneration of the rest of the cell. The butterflies develop the thermodynamically favored double gyroid precursors as a route to the optically more efficient single gyroid nanostructures. Current approaches to photonic crystal engineering also aim to produce single gyroid motifs. The biologically derived photonic nanostructures characterized here may offer a convenient template for producing optical devices based on biomimicry or direct dielectric infiltration.
We investigate the mechanism of structural coloration by quasi‐ordered nanostructures in bird feather barbs. Small‐angle X‐ray scattering (SAXS) data reveal the structures are isotropic and have ...short‐range order on length scales comparable to optical wavelengths. We perform angle‐resolved reflection and scattering spectrometry to fully characterize the colors under directional and omni‐directional illumination of white light. Under directional lighting, the colors change with the angle between the directions of illumination and observation. The angular dispersion of the primary peaks in the scattering/reflection spectra can be well explained by constructive interference of light that is scattered only once in the quasi‐ordered structures. Using the Fourier power spectra of structure from the SAXS data we calculate optical scattering spectra and explain why the light scattering peak is the highest in the backscattering direction. Under omni‐directional lighting, colors from the quasi‐ordered structures are invariant with the viewing angle. The non‐iridescent coloration results from the isotropic nature of structures instead of strong backscattering.
Color generation by short‐range ordered nanostructures in bird feather barbs is investigated with angle‐resolved optical spectrometry. The color is produced mostly by the interference of singly scattered light, and is noniridescent under omnidirectional lighting due to structure isotropy.
The self‐assembly of films that mimic color‐producing nanostructures in bird feathers is described. These structures are isotropic and have a characteristic length‐scale comparable to the wavelength ...of visible light. Structural colors are produced when wavelength‐independent scattering is suppressed by limiting the optical path length through geometry or absorption.
Butterfly wing scales can develop intricate cuticular nanostructures that produce silver colors, but the underlying genetic and physical basis of such colors is mostly unexplored. Here, we ...characterize different types of wild-type silver scales in Bicyclus anynana butterflies and show that the varying thickness of the air layer between two cuticular laminas is most important for producing silvery broadband reflectance. We then address the function of five genes—apterous A, Ultrabithorax, doublesex, Antennapedia, and optix—in silver scale development by examining crispants with either ectopic gains or losses of silver scales. Simultaneous transformations of three parameters—loss of the upper lamina, increased lower lamina thickness, and increased pigmentation—occur when silver scales become brown and vice versa when brown scales become silver. Antennapedia and optix are high-level regulators of different silver scale types and determine cell shape in both sexes. Moreover, Antennapedia is involved in determining ridge and crossrib orientation.
Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or ...quasi-ordered) spongy β-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities. Using synchrotron small angle X-ray scattering (SAXS) and optical spectrophotometry, we characterized the nanostructure and optical function of 297 distinctly coloured feathers from 230 species belonging to 163 genera in 51 avian families. The SAXS data provided quantitative diagnoses of the channel- and sphere-type nanostructures, and confirmed the presence of a predominant, isotropic length scale of variation in refractive index that produces strong reinforcement of a narrow band of scattered wavelengths. The SAXS structural data identified a new class of rudimentary or weakly nanostructured feathers responsible for slate-grey, and blue-grey structural colours. SAXS structural data provided good predictions of the single-scattering peak of the optical reflectance of the feathers. The SAXS structural measurements of channel- and sphere-type nanostructures are also similar to experimental scattering data from synthetic soft matter systems that self-assemble by phase separation. These results further support the hypothesis that colour-producing protein and air nanostructures in feather barbs are probably self-assembled by arrested phase separation of polymerizing β-keratin from the cytoplasm of medullary cells. Such avian amorphous photonic nanostructures with isotropic optical properties may provide biomimetic inspiration for photonic technology.
The colour of fossil feathers Vinther, Jakob; Briggs, Derek E.G; Prum, Richard O ...
Biology letters,
10/2008, Letnik:
4, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Feathers are complex integumentary appendages of birds and some other theropod dinosaurs. They are frequently coloured and function in camouflage and display. Previous investigations have concluded ...that fossil feathers are preserved as carbonized traces composed of feather-degrading bacteria. Here, an investigation of a colour-banded feather from the Lower Cretaceous Crato Formation of Brazil revealed that the dark bands are preserved as elongate, oblate carbonaceous bodies 1-2 μm long, whereas the light bands retain only relief traces on the rock matrix. Energy dispersive X-ray analysis showed that the dark bands preserve a substantial amount of carbon, whereas the light bands show no carbon residue. Comparison of these oblate fossil bodies with the structure of black feathers from a living bird indicates that they are the eumelanin-containing melanosomes. We conclude that most fossil feathers are preserved as melanosomes, and that the distribution of these structures in fossil feathers can preserve the colour pattern in the original feather. The discovery of preserved melanosomes opens up the possibility of interpreting the colour of extinct birds and other dinosaurs.
Colloidal crystals reflecting interference‐based structural colors have been reported in many organisms, but many are yet to be accurately described. Herein, the bright, iridescent scales of green ...and blue
Glenea celestis
beetles are investigated using optical and ultrastructural techniques. The ultrastructural studies based on focused ion‐beam scanning electron microscopy and synchrotron small‐angle X‐ray scattering data reveal the origin of the colors to stem from previously undocumented hexagonal‐close‐packed colloidal crystals within their scales. The optical properties of various colloidal structures are investigated using full‐wave optical simulations. The results highlight the need for further research regarding the development of structural color in beetles.
Vocal learning is thought to have evolved in three clades of birds (parrots, hummingbirds, and oscine passerines), and three clades of mammals (whales, bats, and primates). Behavioural data indicate ...that, unlike other suboscine passerines, the three‐wattled bellbird Procnias tricarunculata (Cotingidae) is capable of vocal learning. Procnias tricarunculata shows conspicuous vocal ontogeny, striking geographical variation in song, and rapid temporal change in song within a population. Deprivation studies of vocal development in P. tricarunculata are impractical. Here, we report evidence from mitochondrial DNA sequences and nuclear microsatellite loci that genetic variation within and among the four allopatric breeding populations of P. tricarunculata is not congruent with variation in vocal behaviour. Sequences of the mitochondrial DNA control region document extensive haplotype sharing among localities and song types, and no phylogenetic resolution of geographical populations or behavioural groups. The vocally differentiated, allopatric breeding populations of P. tricarunculata are only weakly genetically differentiated populations, and are not distinct taxa. Mitochondrial DNA and microsatellite variation show small (2.9% and 13.5%, respectively) but significant correlation with geographical distance, but no significant residual variation by song type. Estimates of the strength of selection that would be needed to maintain the observed geographical pattern in vocal differentiation if songs were genetically based are unreasonably high, further discrediting the hypothesis of a genetic origin of vocal variation. These data support a fourth, phylogenetically independent origin of avian vocal learning in Procnias. Geographical variations in P. tricarunculata vocal behaviour are likely culturally evolved dialects.
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