High Ultraviolet Reflectance Research Articles

Patterns of Visual and Ultraviolet Reflectance in Femoral Gland Secretions of Two Desert Lizards

Femoral gland secretions in lizards convey chemical information about the health and social status of the depositing individual. These secretions influence behaviors related to female mate choice and male–male competition, but little is known about how they are first located by lizards in the environment. Secretions are visually conspicuous and can be sighted from a distance by visually adept lizards, but the specificity of secretion reflectance to the depositing species remains unknown. We examined the reflectance spectra of femoral gland secretions from two sympatric lizard species, Aspidoscelis tigris and Gambelia wislizenii, to determine whether secretions could be visually distinguished. Mean reflectance did not differ between species, but A. tigris had higher reflectance in ultraviolet wavelengths. For both species, lizards in better body condition, as determined by the residuals of the relationship between snout–vent length and body mass, had higher ultraviolet reflectance. In summary, our results indicate that femoral gland secretions can be visually discriminated between species if the discriminating lizard is ultraviolet sensitive.

Enhanced UV-Reflection Facilitated a Shift in the Pollination System of the Red Poppy, Papaver rhoeas (Papaveraceae)

Evolutionary change is considered a major factor influencing the invasion of new habitats by plants. Yet, evidence on how such modifications promote range expansion remains rather limited. Here we investigated flower color modifications in the red poppy, Papaver rhoeas (Papaveraceae), as a result of its introduction into Central Europe and the impact of those modifications on its interactions with pollinators. We found that while flowers of Eastern Mediterranean poppies reflect exclusively in the red part of the spectrum, those of Central European poppies reflect both red and ultraviolet (UV) light. This change coincides with a shift from pollination by glaphyrid beetles (Glaphyridae) to bees. Glaphyrids have red-sensitive photoreceptors that are absent in bees, which therefore will not be attracted by colors of exclusively red-reflecting flowers. However, UV-reflecting flowers are easily detectable by bees, as revealed by visual modeling. In the North Mediterranean, flowers with low and high UV reflectance occur sympatrically. We hypothesize that Central European populations of P. rhoeas were initially polymorphic with respect to their flower color and that UV reflection drove a shift in the pollination system of P. rhoeas that facilitated its spread across Europe.

Evaluation of ultraviolet aging resistance of bitumen containing different organic layered double hydroxides

Layered double hydroxides (LDHs) have been alternatively employed to improve the ultraviolet (UV) aging resistance of bitumen due to their high UV reflectance, but LDHs particles cannot be dispersed into bitumen uniformly and stably since their poor compatibility with bitumen. Therefore, the problem of poor compatibility must be solved before its application. Generally, organic modification can change the surface characteristics of inorganic particle and then improve the compatibility. The objectives of this work are to evaluate the effect of prepared various organic LDHs on the anti-UV aging property of bitumen and then determine an optimal organic LDHs for bitumen modification. For these purposes, three organic anions, sodium dodecyl benzenesulfonate (SDBS), sodium dodecyl sulfate (SDS) and sodium dodecyl sulfonate (SDSO), were used as organic modifiers to prepare organic LDHs (OCLDHs), then the storage stability and anti-UV aging of OCLDHs modified bitumen were investigated. Experimental results show the organic modification can suppress the separation phenomenon of OCLDHs modified bitumen during the high temperature storage, indicating the compatibility and stability of the mixture is ameliorated. Compared with LDHs modified bitumen, OCLDHs modified bitumens show lower aging degree during UV exposure, which indicates that OCLDHs exhibit better effect in enhancing the anti-UV aging performance of bitumen. FTIR analysis indicates that OCLDHs effectively retard the formations of oxygen-containing functional groups and aromatic structure of bitumen. Furthermore, SDBS is a preferable modifier for the preparation of organic LDHs due to the most effective improvement in compatibility with bitumen and UV aging resistance of bitumen as compared with SDS and SDSO.

Habitat Impact on Ultraviolet Reflectance in Moths.

A comparison of 95 species of Central European moths, representing 11 families and inhabiting various habitats, was carried out in order to detect the potential impact of biotope on the ultraviolet (UV) light reflectance of their wings. Based on digitized photographs taken under UV light conditions, a phylogeny-controlled redundancy analysis relating UV reflectance to preferred habitat type (xerophilous, mesophilous, and hygrophilous) and habitat openness (open, semiopen, and closed) was carried out. Species preferring hygrophilous habitats displayed significantly higher UV wing reflectance than species inhabiting xerothermic and mesic habitats, and this pattern remained significant even after controlling for phyletic relationships. In contrast, UV wing reflectance displayed no pattern related to habitat openness. Given the higher UV reflectance of water and humid surfaces, we interpret these results, which are based on the first comprehensive sampling of UV reflectance in Central European moths, in terms of predator avoidance under habitat-specific light conditions. We conclude that the moisture content of the environment may markedly contribute to the variation of appearance of moth wings for better imitation habitat characteristics and therefore to increase protection.

Testosterone levels in relation to size and UV reflectance of achromatic plumage traits of female pied flycatchers

In a substantial number of species, females show some development of secondary sexual characters. These traits can function as signals of individual phenotypic or genetic qualities and status to conspecifics. Individuals may benefit potentially from expressing signals or badges of status if they are reliable and honest signals of individual quality. In many species, badge sizes have been shown to correlate with dominance rank, which may be mediated by testosterone (T) levels. Here, we explored geographic variation in the size and properties of the white wing patch of female pied flycatchersFicedula hypoleucaand its relation to circulating T levels in three populations (two southern populations in central Spain and a northern population in Finland). Furthermore, we aimed at detecting if the size of the white wing patch and its ultraviolet (UV) reflectance indicate individual quality. We found that females in Spain had larger, brighter and more UV reflecting wing patches than those in Finland. Females with higher UV reflectance and larger primary white patches bred earlier. Younger females and females with larger primary white wing patches showed higher T levels. In contrast, higher values of UV reflectance in feathers from these patches were associated with low T levels. Despite genetic differentiation and differences in trait expression between populations, female pied flycatchers from different populations may converge and use the size of white wing patches to signal their T levels and thereby their social dominance.

Reflectance spectroscopy (200–2500 nm) of highly-reduced phases under oxygen- and water-free conditions

Spectra of highly-reduced mineral phases from 200 to 2500nm provide new laboratory constraints on the surfaces of asteroids and other extremely reduced solid assemblages. Synthetic oldhamite (CaS) is distinguished by high ultraviolet reflectance (which decreases toward shorter wavelengths). Oldhamite and osbornite spectra show absorption features at ∼401nm and ∼436nm, respectively. Chemically pure synthetic oldhamite is spectrally distinct from naturally-occurring oldhamite from the Norton County aubrite, possibly due to differences in minor and trace element compositions, presence or absence of inclusions, or differences in oxidation/hydration (terrestrial weathering). Iron powders at 50nm and 10μm nominal particle sizes, nanophase graphite, and carlsbergite (CrN) all have very low reflectivity over the 200–2500nm wavelength range. Carlsbergite has a slight blue spectral slope in the visible and near-infrared (400–2500nm), while the iron powders and nanophase graphite show slight red slopes over this wavelength range.

Colour choice behaviour in the pollen beetle Meligethes aeneus (Coleoptera: Nitidulidae)

The pollen beetle Meligethes aeneus Fabricius (Coleoptera, Nitidulidae), a pest of oilseed rape (Brassica napus), is known to respond to coloured stimuli; however, current understanding of the underlying mechanisms of colour choice in this species is limited. In the present study, physiological and behavioural experiments are conducted to determine the response of the pollen beetle to colours in the field. Spectral sensitivity is measured in 10 animals using the electroretinogram technique. Light flashes (100 ms) at varied wavelengths (340–650 nm, 10‐nm steps) and at different light intensities are applied to the eye after dark adaptation. In behavioural experiments in the field, 100 water traps of varying colours (from yellow to green to blue with varying amounts of white and black added, and with known spectral reflectance) are set out on a bare soil field in May 2008. The mean spectral sensitivity curve of M. aeneus peaks at 520 nm; however, a model template fitted to the long wavelength tail of the observed curve reveals a peak at approximately 540 nm (green). A secondary sensitivity peak is observed in the ultraviolet (UV) range (370 nm). A total of 2482 pollen beetles are captured in the coloured traps. The results show that the pollen beetles' preference for yellow over other colours can be modelled as a colour opponent mechanism (green versus blue); however, further experiments are needed to specify responses to colours with higher UV reflectance. These findings may be used to optimize trap colours for monitoring to help develop integrated pest management strategies for pollen beetle control.

Individual quality and nuptial throat colour in male European green lizards

AbstractNuptial traits signalling individual quality are common in numerous animal taxa, and play a significant role in sexual selection. Detecting female mate choice based on visual cues is notoriously hard in lizards. Previously, we found that female European green lizards (Lacerta viridis) preferred to associate with males with high ultraviolet (UV) throat reflectance. Here, we investigated if different components of nuptial throat colour of male European green lizards were correlated to other fitness‐related traits, and thus could signal male quality. We found that (1) high UV chroma correlates positively with directional asymmetry and shows a negative trend with body condition; (2) blue chroma is not related to any individual traits; and (3) total throat brightness correlates positively with body size and relative head size, and negatively with ectoparasite load. Our results suggest that having high throat UV reflectance is costly for male European green lizards, so probably only high‐quality individuals can afford it, while total brightness of the throat colour signals age, relative head size and health status. Hence, throat colour in male European green lizards is a multiple honest signal.

Widespread cryptic dichromatism and ultraviolet reflectance in the largest radiation of Neotropical songbirds: Implications of accounting for avian vision in the study of plumage evolution

Avian coloration has played a central role in the study of sexual selection and other aspects of animal behavior. However, only recently have analyses of avian coloration been able to incorporate avian visual abilities. Although several studies have broadly sampled species for evidence of plumage coloration visible to birds but invisible to humans, few studies have quantified these data for all species in a single taxonomic group. We quantify ultraviolet (UV) plumage reflectance and document cryptic sexual dichromatism in the largest radiation of Neotropical songbirds, the cardinals and tanagers. Ultraviolet reflectance was common in the patches measured, with almost half of the species reflecting >20% of light in the UV range in at least one patch. High UV-reflecting patches, including 73 of the 91 patches that were found to be primarily UV colored, belonged to species in either Passerina or 2 of 13 major clades of tanagers. This indicates that high UV reflectance is not randomly distributed across the phytogeny. Sexual dichromatism was much more widespread in the group than previously thought. From a human visual perspective, about half the species in the group are sexually dichromatic; but from an avian visual perspective, 97% of species are dichromatic. We compared the implications of using human-perceived versus avian-perceived sexual dichromatism by mapping these traits onto tanager phytogenies. Quantifying dichromatism using an avian visual model provided a more accurate and detailed history of plumage coloration change across evolutionary history.

Temperature, but not available energy, affects the expression of a sexually selected ultraviolet (UV) colour trait in male European green lizards.

BackgroundColour signals are widely used in intraspecific communication and often linked to individual fitness. The development of some pigment-based (e.g. carotenoids) colours is often environment-dependent and costly for the signaller, however, for structural colours (e.g. ultraviolet [UV]) this topic is poorly understood, especially in terrestrial ectothermic vertebrates.Methodology/Principal FindingsIn a factorial experiment, we studied how available energy and time at elevated body temperature affects the annual expression of the nuptial throat colour patch in male European green lizards (Lacerta viridis) after hibernation and before mating season. In this species, there is a female preference for males with high throat UV reflectance, and males with high UV reflectance are more likely to win fights. We found that (i) while food shortage decreased lizards' body condition, it did not affect colour development, and (ii) the available time for maintaining high body temperature affected the development of UV colour without affecting body condition or other colour traits.Conclusions/SignificanceOur results demonstrate that the expression of a sexually selected structural colour signal depends on the time at elevated body temperature affecting physiological performance but not on available energy gained from food per se in an ectothermic vertebrate. We suggest that the effect of high ambient temperature on UV colour in male L. viridis makes it an honest signal, because success in acquiring thermally favourable territories and/or effective behavioural thermoregulation can both be linked to individual quality.

Female European green lizards (Lacerta viridis) prefer males with high ultraviolet throat reflectance

The role of ultraviolet (UV) signals in intraspecific communication has been identified in a number of vertebrate taxa. In lizards, the signalling role of UV has only been shown in male–male competition and male mate choice. Here, we investigated whether male UV colour can be a basis of female association preference in European green lizards (Lacerta viridis), a species where males develop blue nuptial throat colouration with high UV reflectance. We experimentally manipulated the UV colour of male pairs, where the members of the pair did not differ significantly in body length, body weight, head size, throat UV chroma and brightness or throat blue chroma and brightness measured prior to colour manipulation. By providing these pairs of males to females (only visual stimuli could be perceived by the females), we assessed the role of UV in female association preference irrespective of other potentially important visual traits. We found that unmated but receptive females preferred males of higher UV reflectance. Our results show for the first time that UV colour can be an important male signal in female preference in reptiles.

UV plumage color is an honest signal of quality in male budgerigars

AbstractElaborate and colorful feathers are important traits in female mate choice in birds. Plumage coloration can result from pigments deposited in feathers such as carotenoids and melanins, or can be caused by nano‐scale reflective tissues (structurally based coloration), usually producing ultraviolet (UV) coloration. Structural colorations remain the least studied of the three most important feather colorations. Previous studies have found a female preference for UV color in the budgerigar, Melopsittacus undulatus, but it is not clear what information this ornament conveys, nor what is the possible cost associated with its production. We investigated possible correlations between immune response and plumage color of wild‐type (green) male budgerigars. In particular we measured the wing web swelling resulting from injection of phytohaemagglutinin (PHA). We did not detect any correlation between the sedimentation rate and morphological and color variables. We found that UV chroma is the best predictor for the cutaneous immune activity. Indeed, male budgerigars with high UV reflectance in the breast feathers showed stronger immune responses. These results are consistent with the idea that UV colors are special signals conveying information about a bird's condition.

Silicon nanowire grid polarizer for very deep ultraviolet fabricated from a shear-aligned diblock copolymer template

A silicon (Si) nanowire grid ultraviolet (UV) transmission polarizer has been fabricated, and its performance was measured over the visible to deep UV range. A cylinder-forming polystyrene-b-poly(hexylmethacrylate) diblock copolymer was coated onto an amorphous Si layer supported on a fused silica substrate, then shear aligned and employed as a mask for reactive-ion etching, resulting in a Si grid of 33 nm period and multi-centimeter-squared area. Due to the high plasma frequency and UV reflectance of the deposited Si, this nanowire grid was able to polarize light down into the deep UV, including 193 nm.

Absence of status signalling by structurally based ultraviolet plumage in wintering blue tits (Cyanistes caeruleus)

Structurally based ultraviolet (UV)-reflective plumage parts can be important cues in mate choice. However, it remains largely unknown if UV plumage variation can also function as a signal of social status during competitive interactions. In blue tits (Cyanistes caeruleus), the UV-reflective crown plumage functions as a female mate choice cue that probably indicates male quality, as males with higher UV reflectance have been shown to have better chances of over-winter survival. Possibly, the UV crown plumage acts as a status signal in the competition over scarce food sources during winter. To test this idea, we related dominance of individuals at an artificial food source during adverse winter conditions to spectrophotometric measurements of their crown plumage. However, while controlling for the confounding effects of sex, age, and distance from territory, we found no significant effect of crown UV reflectance on dominance. Consistent with this result, we also found no relation between crown UV reflectance and over-winter survival. We conclude that the structurally based UV reflectance of the blue tit crown feathers plays little role in competition between individuals during winter despite its importance as a cue in mate choice.

ULTRAVIOLET BEAK SPOTS IN KING AND EMPEROR PENGUINS

Abstract In seabirds, colors of feathers and external tissues have only recently been studied, and ultraviolet (UV) color has not yet been detected. Using live individuals as well as museum skins, we found UV peaks of reflectance in two large Aptenodytes species, King (A. patagonicus) and Emperor (A. forsteri) Penguins. UV reflectance did not occur on the feathers, claws, or skin of these species, nor did we find UV reflectance in five other genera of penguins (11 species). UV peaks overlapped with spots of color on the lower beak that appeared orange for human observers, and beak spots differed slightly in location between the two species. Adults of both sexes possessed these UV markings, but they were lacking in juveniles, as was the orange color of the beak spot, and auricular patches used for selecting mates. Finally, measurements of free-ranging King Penguins showed that recently paired birds had higher UV reflectance than courting ones, suggesting possible roles of UV beak spots in pairing and as an...

Conspicuous, ultraviolet-rich mouth colours in begging chicks.

There is as yet no clear consensus on the function of vivid mouth colours in begging chicks. A major obstacle to our understanding has been that no studies have measured gape colours independently of human colour perception. Here, we present the first study, to our knowledge, to use UV-VIS spectrometry to quantify the gape colour, background nest colour and nest light environment of eight European passerines. Both mouths and the surrounding flanges show striking and previously unreported peaks of reflectance in the ultraviolet, coupled with high long-wavelength reflectance responsible for the human-visible appearance of the gape. High ultraviolet reflectance is likely to have an important effect on the conspicuousness of nestling mouths, since contrast with the nest background is maximal in the ultraviolet. Furthermore, the dual-peak nature of the spectra suggests that gapes are avian non-spectral colours analogous to human purple.

The enigmatic object 2201 Oljato: Is it an asteroid or an evolved comet?

The study of the near‐Earth object 2201 Oljato has resulted in many surprises in the decade in which it has been examined. Its orbital properties have been associated with meteor showers, and its modeled orbital evolution is chaotic, a property which might indicate a history related to comets. Telescopic observations of its visible and near‐infrared spectral reflectance, broad‐band visible and near‐infrared photometry, infrared radiometric measurements, and radar echoes are reported here from two apparitions, 1979 and 1983. A look at all available observational data shows that this asteroid has a high radiometric albedo, a property not associated with comet nuclei. In certain wavelength regimes it is classified as an S‐type asteroid, in others, an E‐type, but its overall spectral reflectance is not typical of either taxonomic type, and neither type is thought of as cometlike. Unexpectedly high ultraviolet reflectance at the 1979 apparition was suggested to be the result of residual outgassing as in a comet. The UV photometric data are modeled as fluorescent emission from neutral species found in comets. The resulting calculations indicate a plausible value for OH and CN emission at 0.3085 and 0.38 μm relative to the observed range of active comets. Observations to monitor photometric variations and to search for gaseous activity using observational techniques designed specifically for this purpose were planned and executed in October 1992 to verify or refute the interpretations presented here.