Blue Iridescence Research Articles

Eremitis clarkiae and E. vinacea (Poaceae, Bambusoideae): two new species of herbaceous bamboos endemic to the Atlantic Forest of southern Bahia, Brazil increase the diversity of the genus in this hotspot

Background and aims – We here describe two new species of Eremitis from Bahia, Brazil, and compare them with morphologically similar species. We also provide illustrations, photos, a distribution map, and notes on habitat and conservation status of the new species.Material and methods – This study was based on fieldwork, analysis of herbarium specimens, and literature review. Specimens collected were analyzed and photographed during fieldwork and observed in cultivation in a greenhouse. The conservation assessment is based on field observations and spatial analyses, following the IUCN guidelines and criteria.Results – Eremitis clarkiae sp. nov. occurs in southern Bahia and has been collected only twice, in the municipality of Floresta Azul. The new species is similar to E. jardimii and E. robusta, both also endemic to Bahia, but can be distinguished by several vegetative and reproductive structures longer than those observed in these species, such as leafy culms, ligules, decumbent culm inflorescences, and pedicels of the staminate spikelets of the staminate whorls. Eremitis vinacea sp. nov. was collected in three localities in southern Bahia, but only the type population was found during recent field trips, in the municipality of Camacã. It is similar to E. afimbriata, a species endemic to Espírito Santo state, being differentiated by its leaf sheaths with persistent fimbriae (vs absent), leaf blades with green adaxial surface (vs bluish green with a blue iridescence), and a single inflorescence on decumbent culms (vs multiple). Both new species are endemic to the Bahian Coastal Forests subregion and should be considered Critically Endangered (CR), according to the IUCN guidelines and criteria.

Eremitis berbertii and E. fluminensis (Poaceae, Bambusoideae): New Species from the Brazilian Atlantic Forest and Updates on Leaf Microcharacters in the Genus

Eremitis Döll is a herbaceous bamboo genus (Poaceae, Bambusoideae, Olyreae) belonging to subtribe Parianinae that currently includes seven species. During fieldwork conducted throughout the geographic distribution of the genus, two new species with blue iridescent leaves, E. berbertii F. M. Ferreira & R. P. Oliveira and E. fluminensis F. M. Ferreira & R. P. Oliveira, from the Brazilian Atlantic forest, were collected and are here described and illustrated. Eremitis berbertii is endemic to the Private Reserve of Natural Heritage (Reserva Particular do Patrimônio Natural [RPPN]) Serra do Teimoso, in Bahia State, and E. fluminensis is restricted to the south of Rio de Janeiro State. In this study, micromorphological features of the leaf epidermis of the new species were compared with other species of the genus that display blue iridescence in their leaf blades. Variegated leaves are recorded for the first time in herbaceous bamboos. Comments on habitat, distribution, and conservation status of the new taxa are provided, as well as a revised identification key to all species of the genus described so far.

Coloration principles of the Great purple emperor butterfly (Sasakia charonda)

The dorsal wings of male Sasakia charonda butterflies display a striking blue iridescent coloration, which is accentuated by white, orange-yellow and red spots, as well as by brown margins. The ventral wings also have a variegated, but more subdued, pattern. We investigated the optical basis of the various colors of intact wings as well as isolated wing scales by applying light and electron microscopy, imaging scatterometry and (micro)spectrophotometry. The prominent blue iridescence is due to scales with tightly packed, multilayered ridges that contain melanin pigment. The scales in the brown wing margins also contain melanin. Pigments extracted from the orange-yellow and red spots indicate the presence of 3-OH-kynurenine and ommochrome pigment. The scales in the white spots also have multilayered ridges but lack pigment. The lower lamina of the scales plays a so-far undervalued but often crucial role. Its thin-film properties color the majority of the ventral wing scales, which are unpigmented and have large windows. The lower lamina acting as a thin-film reflector generally contributes to the reflectance of the various scale types.

Phototunable Morpho Butterfly Microstructures Modified by Liquid Crystal Polymers

AbstractThe unique hierarchical microstructures of the Morpho butterfly wing (MBW) exhibit angle independent blue iridescence. Biomimicking these microstructures and turning them into functional photonic crystals (PhCs) have fascinated scientists yet remain challenging. Here, a phototunable PhC is fabricated by depositing the azobenzene‐containing linear liquid crystal polymer (LLCP) onto the MBW template. Thanks to the excellent mechanical properties and deformability of LLCP, the generated 3D bilayer microstructures demonstrate hierarchical deformation upon UV light irradiation, leading to a blueshift of the reflection peak (70 nm) and a remarkable change of reflectance (40%). This phototunable PhC may have potential applications in pigments, cosmetics, and sensors.

A new annual fish of the genus Austrolebias (Cyprinodontiformes: Rivulidae) from Rio Camaquã basin, Laguna dos Patos system, Brazilian Pampa.

A new species of Austrolebias is described from the middle course of the Rio Camaquã, Laguna dos Patos system, Rio Grande do Sul, Brazil. The new species belongs to the Austrolebias alexandri species group, which is distinguished from the remaining congeners by the presence of a dark gray pectoral fin with bright blue iridescence in males. The new species is distinguished from all remaining species of the A. alexandri species group by the following combination of characters: presence of well-defined bright blue bars on the flank in males, shorter caudal fin length in males and females, contact organs in the first three rays of the pectoral fin in males, one to two post-optic neuromasts (rarely three), basihyal width of 50% of the length, and basihyal cartilage about 50-60% of the basihyal length. The recognition of this new species belonging to the A. alexandri group endemic of the middle course of Rio Camaquã and the recent discovery of Austrolebias bagual in the same general region reinforces the claim of the middle Rio Camaquã basin as an area of endemism for annual fishes and as such, a priority area for conservation in southern Brazil.

Coloration and Structure of the Wings ofChorinea sylphinaBates

The structure and the origin of transparency of the wings of Chorinea sylphina, a species of glasswinged butterflies, were explored using optical microscopy, scanning electron microscopy, UV photography, spectrophotometry, and optical polarimetry. We found that for normally incident light, the clear transparent areas of the forewings and hindwings exhibit significant transmission as well as minuscule reflection throughout the visible regime in the electromagnetic spectrum. We found that the transparency results from the sparsity, the semitransparency, and the upright orientation of single scales on the wing membrane. The red and dark brown colors of the nontransparent areas of the wings have a pigmentary origin. Coherent scattering from the slanted and overlapping lamellae in the scale ridges and diffraction from every scale's longitudinal network of parallel ridges are responsible for blue iridescence and shimmer at large viewing angles. The transparent areas of the wings function as absorbing linear polarizers, due to both the parallel ridges and the almost unidirectional orientation of individual scales on those areas.

Lake Surface Full of Clouds, and: Quiet, and: Two Robins in Summer

Lake Surface Full of Clouds, and: Quiet, and: Two Robins in Summer Joseph Duemer Note from the Editors: It is with sadness that we report the passing away of Joseph Duemer, at the age of 66, on June 27, 2017. Joe served as Poetry Editor of The Wallace Stevens Journal for twenty years, from 1990 to 2010. He was Professor Emeritus of Humanities at Clarkson University, where he had taught courses in creative writing, literature, popular music, and Buddhism. He published numerous books of poetry, including The Light of Common Day, Customs, Static, and Magical Thinking, and coedited Dog Music: Poetry about Dogs. His poems and criticism appeared in more than seventy-five literary journals. His latest volume of poetry, which he was preparing for publication under the title River with Birds, contains several poems that testify to Stevens’s inspiration on him. We have decided to start our usual selection of poems by reproducing three of these works in celebration of Joe’s poetic career and his longtime service to the Journal. We express our sincere condolences to Joe’s wife, Carole Mathey, and thank her for granting permission to publish the following poems. Lake Surface Full of Clouds In this July evening in the mountains the lake lies within its stone perimeter & light presses against its surface. Wind shapes it & clouds print their exact images on the water, moving. The scent of jack pine fills the air, & the cry of a phoebe, two long notes repeated: thing & song [End Page 278] in their wild fullness full. The world is plainspoken; full of evening light, it is there before me. I lack the perfect mind of an animal, such that I can see myself seeing this. I know myself. I have the stupid human trick of language & a bright penny in my pocket. The tyrant kingbird swerves kit-kit-kit out over the lake’s edge & glances down so that one imagines the lake bottom as conceived from flight. The geography of the lakebed flickers with bronze coins consisting of light & the teal transparency of old glass, the blue iridescence of a trout’s fin in the sunlit shallows swept by shadows. But there is no book of the world—not the night sky’s constellations nor another’s body that we touch with our open hands—neither book nor mirror. We must content ourselves in ourselves in our desolation with the print of a mink’s forepaws on brown sand— left there when [End Page 279] he bent to lick a few streaks of light from the tensed lake. Note: Previously published in American Literary Review; “Lake Surface Full of Clouds” was the winner of the journal’s annual award for best poem in 2012. Quiet “One grows used to the weather.” —Stevens, “The American Sublime” I have always lived here without knowing anything much about anything much, except this slanting light & mild weather, mostly sunny & lulling me to sleep I now see that the light on the bright island is not as I had thought, not without precedent. It has alwaysbeen an exile’slight, trembling. Quiet. Quiet. My phonemes obey the island’s laws of limited motion— short & clear & as careful as needles scoring birdsong on precise devices. Or they will buzz slightly & blur [End Page 280] into the damaged music of language. I have listened but for too long without attention. It has alwaysbeen an exile’slight, trembling. Quiet. Quiet. Light shifts, singing only empty space. A flicker of ultraviolet shivers in the night sky. It is as dry as these dry stalks & shadows of dry stalks askew in soil long given over to waiting—some fleck of water glinting on the faucet’s lip. That will be enough, or almost enough. Light shifts . . . It has alwaysbeen an exile’s light, tense & trembling. Quiet. Quiet. . . . a sharp breeze shifts direction, adjusting leaves & stirring unbroken branches. Waking, the weather veers predictably enough toward beauty (which must be acknowledged) & loneliness (now devoid of the sublime) but I drift in & out of [End Page 281] shadows cast by stately cumulus. Here I am. It has alwaysbeen an exile’slight, trembling. Quiet. Quiet...

Colour formation on the wings of the butterfly Hypolimnas salmacis by scale stacking.

The butterfly genus Hypolimnas features iridescent blue colouration in some areas of its dorsal wings. Here, we analyse the mechanisms responsible for such colouration on the dorsal wings of Hypolimnas salmacis and experimentally demonstrate that the lower thin lamina in the white cover scales causes the blue iridescence. This outcome contradicts other studies reporting that the radiant blue in Hypolimnas butterflies is caused by complex ridge-lamellar architectures in the upper lamina of the cover scales. Our comprehensive optical study supported by numerical calculation however shows that scale stacking primarily induces the observed colour appearance of Hypolimnas salmacis.

Photonic multilayer structure of Begonia chloroplasts enhances photosynthetic efficiency.

Enhanced light harvesting is an area of interest for optimizing both natural photosynthesis and artificial solar energy capture1,2. Iridescence has been shown to exist widely and in diverse forms in plants and other photosynthetic organisms and symbioses3,4, but there has yet to be any direct link demonstrated between iridescence and photosynthesis. Here we show that epidermal chloroplasts, also known as iridoplasts, in shade-dwelling species of Begonia5, notable for their brilliant blue iridescence, have a photonic crystal structure formed from a periodic arrangement of the light-absorbing thylakoid tissue itself. This structure enhances photosynthesis in two ways: by increasing light capture at the predominantly green wavelengths available in shade conditions, and by directly enhancing quantum yield by 5-10% under low-light conditions. These findings together imply that the iridoplast is a highly modified chloroplast structure adapted to make best use of the extremely low-light conditions in the tropical forest understorey in which it is found5,6. A phylogenetically diverse range of shade-dwelling plant species has been found to produce similarly structured chloroplasts7-9, suggesting that the ability to produce chloroplasts whose membranes are organized as a multilayer with photonic properties may be widespread. In fact, given the well-established diversity and plasticity of chloroplasts10,11, our results imply that photonic effects may be important even in plants that do not show any obvious signs of iridescence to the naked eye but where a highly ordered chloroplast structure may present a clear blue reflectance at the microscale. Chloroplasts are generally thought of as purely photochemical; we suggest that one should also think of them as a photonic structure with a complex interplay between control of light propagation, light capture and photochemistry.

Symmetry constraints during the development of anisotropic spinodal patterns.

Spinodal decomposition is a phase-separation phenomenon occurring at non-equilibrium conditions. In isotropic materials, it is expected to improve the physical properties, in which modulated structures arise from a single system of spinodal waves. However, in anisotropic materials this process is controversial and not very well understood. Here, we report anisotropic spinodal decomposition patterns in single crystals of K-rich feldspar with macroscopic monoclinic 2/m symmetry. The periodicity of the spinodal waves at ~450 nm produces a blue iridescence, typical of the gemstone moonstone. Stripe patterns in the (010) plane, labyrinthine patterns in the (100) plane, and coexistence of the two patterns in the (110) plane are first resolved by scanning Rayleigh scattering microscopy. Two orthogonal systems of spinodal waves with the same periodicity are derived from the features and orientations of the patterns on the crystal surfaces. The orthogonality of the waves is related to the perpendicularity of the binary axis and the mirror plane. Thus, the spinodal patterns must be controlled by symmetry constraints during phase separation at early stages. Unusual and new properties could be developed in other anisotropic materials by thermal treatment inducing two orthogonal systems of periodic spinodal waves.

虹色素胞による青い光沢を有するメダカの体色変異体

観賞魚の“幹之メダカ”は，背部の光沢のある青い体色を特徴とするミナミメダカの自然変異体である。幹之メダカの背部体表色を解明するため，電子顕微鏡を用いた組織学的検討を行った。幹之メダカでは真皮深層に規則的に重層配列した反射小板を含む虹色素胞を認めた。一方，野生型メダカでは虹色素胞は確認できなかった。幹之メダカの金属様光沢は虹色素胞によるものであることが確認できた。また，規則的な反射小板の配列が青色の構造色を発現していることが示唆された。

Fabrication of hierarchical photonic nanostructures inspired by Morpho butterflies utilizing laser interference lithography

We introduce laser interference lithography (LIL) as a tool to fabricate hierarchical photonic nanostructures inspired by blue Morpho butterflies. For that, we utilize the interference pattern in vertical direction in addition to the conventional horizontal one. The vertical interference creates the lamellae by exploiting the back reflection from the substrate. The horizontal interference patterns the ridges of the hierarchical Christmas tree like structure. The artificial Morpho replica produced with this technique feature a brilliant blue iridescence up to an incident angle of 40°.

Global stone heritage: Larvikite, Norway

Abstract Larvikite is a peculiar and unique monzonitic rock originating in the Carboniferous–Permian Oslo Rift, SE Norway. The blue iridescence in the feldspar crystals made the rock particularly attractive as ornamental stone, and since the start of industrial scaled production in 1884, the use of larvikite has reached every corner of the global community. With resources for hundreds of years, the region will produce larvikite blocks far into the future. The production of larvikite has changed significantly during the last decades, towards more sustainable production finding new applications and markets for excess rock in the quarries. The significance of larvikite in the global market has also created a wider appreciation of the rock in the Norwegian society, acknowledging the rich history of larvikite production and use.

Optical Lattices on Wings ofApaturaButterflies

Optical microscopy of scales from the wings of the male butterfly Apatura ilia reveals parallel fibers with a spacing of about 710 nm. These fibers, together with tiny transverse grooves, cause violet blue or blue iridescence due to interference of light on the wings, which normally have brown pigmentation. Here we establish the dependence of the sudden color changes on variable illumination and observation angle.

Short Communication: A new record of naturalized Selaginella uncinata (Desv.) Spring (Selaginellaceae) from Java, Indonesia

Setyawan AD. 2014. A new record of naturalized Selaginella uncinata (Desv.) Spring (Selaginellaceae) from Java, Indonesia. Biodiversitas 15: 261-268. During extensive field researches on the diversity and distribution of Selaginella in Java, between 2007 and2014, an alien species has been found in nature, i.e. Selaginella uncinata. This species is a trailing herb with small, wiry, creeping mainstem, fan-shaped branches, rooting at the nodes to c.a. 100 cm long or more; leaves are dimorphic, 4-ranked, and characterized byconspicuous blue iridescent; strobili are tetragonal, up to c.a. 2 cm long. S. uncinata was found growing wild in the highlands with highrainfall, namely: Cibodas Botanical Garden, Cianjur, West Java and Tawangsari, in the city district of Wonosobo, Central Java,Indonesia. Transplant experiments showed that this plant was able to grow and reproduce well in lowlands (Depok, 107 m asl.) andhighlands (Wonosobo, 768 m asl.). In the experimental garden, it could compete successfully with native species of Javan selaginellas, for space, sunlight and nutrients. Therefore, we must be concerned about the invasion ability of this species.

Disorder and broad-angle iridescence from Morpho-inspired structures.

The ordered, lamellae-structured ridges on the wing scales of Morpho butterflies give rise to their striking blue iridescence by multilayer interference and grating diffraction. At the same time, the random offsets among the ridges broaden the directional multilayer reflection peaks and the grating diffraction peaks that the color appears the same at various viewing angles, contrary to the very definition of iridescence. While the overall process is well understood, there has been little investigation into confirming the roles of each factor due to the difficulty of controllably reproducing such complex structures. Here we use a combination of self-assembly, selective etching, and directional deposition to fabricate Morpho-inspired structure with controlled random offsets. We find that while random offsets are necessary, it alone is not sufficient to produce the broad-angle reflection of Morpho butterflies. We identify diffraction as a critical factor for the bright, anisotropic broadening of the reflection peak of Morpho butterflies to a solid angle of 0.23 sr, and suggest random macroscopic surface curvature as a practical alternative, with an isotropic broad reflection peak whose solid angle can reach 0.11 sr at an incident angle of 60°.

Australoheros sanguineus sp. n. - a new cichlid species from the rio Cubatão basin, southern Brazil (Cichlidae: Heroini)

A new species of Australoheros is herein described from the rio Cubatão basin, southern Brazil. The new species differs from all its congeners mainly by the following character states: presence of a conspicuous rounded caudal-fin base; presence of two blood red regions on the corners of caudal-fin posterior margin; absence of conspicuous metallic blotches on anal-fin base; absence of a red pigmented line on dorsal-fin margin; presence of one conspicuous blue iridescence bar on dorsal-margin; more pectoral-fin rays (14); fewer proximal radials on dorsal-fin base (24 – 25); more proximal radials on anal-fin base (13); anal-fin base squamation beginning at 7th anal-fin spine; and dorsal-fin base squamation beginning between 11th and 12th dorsal-fin spine.

Silica nanoparticles aid in structural leaf coloration in the Malaysian tropical rainforest understorey herb Mapania caudata.

Blue-green iridescence in the tropical rainforest understorey sedge Mapania caudata creates structural coloration in its leaves through a novel photonic mechanism. Known structures in plants producing iridescent blues consist of altered cellulose layering within cell walls and in special bodies, and thylakoid membranes in specialized plastids. This study was undertaken in order to determine the origin of leaf iridescence in this plant with particular attention to nano-scale components contributing to this coloration. Adaxial walls of leaf epidermal cells were characterized using high-pressure-frozen freeze-substituted specimens, which retain their native dimensions during observations using transmission and scanning microscopy, accompanied by energy-dispersive X-ray spectroscopy to identify the role of biogenic silica in wall-based iridescence. Biogenic silica was experimentally removed using aqueous Na2CO3 and optical properties were compared using spectral reflectance. Blue iridescence is produced in the adaxial epidermal cell wall, which contains helicoid lamellae. The blue iridescence from cell surfaces is left-circularly polarized. The position of the silica granules is entrained by the helicoid microfibrillar layers, and granules accumulate at a uniform position within the helicoids, contributing to the structure that produces the blue iridescence, as part of the unit cell responsible for 2 ° Bragg scatter. Removal of silica from the walls eliminated the blue colour. Addition of silica nanoparticles on existing cellulosic lamellae is a novel mechanism for adding structural colour in organisms.

Theoretical and experimental analysis of the structural pattern responsible for the iridescence of Morpho butterflies

Morpho butterflies are well-known for their iridescence originating from nanostructures in the scales of their wings. These optical active structures integrate three design principles leading to the wide angle reflection: alternating lamellae layers, "Christmas tree" like shape, and offsets between neighboring ridges. We study their individual effects rigorously by 2D FEM simulations of the nanostructures of the Morpho sulkowskyi butterfly and show how the reflection spectrum can be controlled by the design of the nanostructures. The width of the spectrum is broad (≈ 90 nm) for alternating lamellae layers (or "brunches") of the structure while the "Christmas tree" pattern together with a height offset between neighboring ridges reduces the directionality of the reflectance. Furthermore, we fabricated the simulated structures by e-beam lithography. The resulting samples mimicked all important optical features of the original Morpho butterfly scales and feature the intense blue iridescence with a wide angular range of reflection.

<i>Eremitis afimbriata</i> and <i>E. magnifica</i> (Poaceae, Bambusoideae, Olyreae): two remarkable new species from Brazil and a first record of blue iridescence in bamboo leaves

Two new species belonging to the herbaceous bamboo genus Eremitis (Poaceae, Bambusoideae) are herein described as E. afimbriata and E. magnifica. We discuss the morphological characters and SEM leaf epidermis patterns that distinguish the new species and compare them to E. parviflora, the only species currently accepted in this genus. An identification key for the species is provided. Both new species display blue iridescence in their leaf blades, the first time this is recorded in bamboos. These new taxa are only known from their type localities, both from Atlantic Forest in Southern Brazil, the first one from Southern Espírito Santo and the second from Eastern Minas Gerais. They are restricted to semi-deciduous seasonal forests and are considered critically endangered according to the IUCN criteria, while E. parviflora, restricted to Bahia, occurs in distinct forest types throughout its distribution area.