Colour vision in the passeriform bird,Leiothrix lutea: correlation of visual pigment absorbance and oil droplet transmission with spectral sensitivity

The visual receptors in the retina of the passeriform bird Leiothrix lutea were examined microspectro-photometrically. The rods had a maximum absorbance close to 500 nm. Four spectrally different classes of single cone were identified with typical combinations of photopigments and oil droplets: a long-wave sensitive cone with a photopigment P568 and a droplet with a cut-off wavelength at 564 nm, a middle-wave sensitive cone with a P499 and a droplet with a cut-off at 506 nm, a short-wave sensitive cone with a P454 and a droplet with maximum absorbance below 410nm and an ultraviolet sensitive cone with a P355 and a transparent droplet. Double cones possessed a P568 in both the principal and accessory members. A pale droplet with variable absorbance (maximal at about 420 nm) was associated with the principal member whereas the ellipsoid region of the accessory member contained only low concentrations of carotenoid. The effective spectral sensitivities of the different cone classes were calculated from the characteristic combinations of oil droplets and photopigments and corrected for the absorbance of the ocular media. Comparison of these results with the behavioural spectral sensitivity function of Leiothrix lutea suggests that the increment threshold photopic spectral sensitivity of this avian species is mediated by the 4 single cone classes modified by neural opponent mechanisms.Abbreviations LWS long wave sensitive - MWS middle wave sensitive - SWS short wave sensitive (cones)     

Modelling oil droplet absorption spectra and spectral sensitivities of bird cone photoreceptors

Birds have four spectrally distinct types of single cones that they use for colour vision. It is often desirable to be able to model the spectral sensitivities of the different cone types, which vary considerably between species. However, although there are several mathematical models available for describing the spectral absorption of visual pigments, there is no model describing the spectral absorption of the coloured oil droplets found in three of the four single cone types. In this paper, we describe such a model and illustrate its use in estimating the spectral sensitivities of single cones. Furthermore, we show that the spectral locations of the wavelengths of maximum absorbance (_max) of the short- (SWS), medium- (MWS) and long- (LWS) wavelength-sensitive visual pigments and the cut-off wavelengths (_cut) of their respective C-, Y- and R-type oil droplets can be predicted from the _max of the ultraviolet- (UVS)/violet- (VS) sensitive visual pigment.     

Spectral sensitivities of photoreceptors and lamina monopolar cells in the dragonfly,Hemicordulia tau

Summary Five spectral types of photoreceptors with peak sensitivities at 330 nm, 410 nm, 460 nm, 525 nm and 630 nm were recorded from the ventral eye of the dragonfly, Hemicordulia tau. Often the 525 nm photoreceptors presented broader, and the 630 nm photoreceptors narrower, spectral sensitivities than would be excepted of a photopigment with the same peak sensitivity. Four types of lamina monopolar cells (cell types 1–4) were recognised from their dark-adapted spectral sensitivities and their anatomy. The anatomical identification allows tentative assignation to the monopolar cell classification from Sympetrum rubicundulum obtained using Golgi staining (Meinertzhagen and Armett-Kibel 1982). When dark-adapted, the monopolar cells had peak spectral sensitivities that were similar to single photoreceptors or appeared to pool receptor outputs, but in some cases spectral sensitivity changed markedly upon adaptation to white and to chromatic light, in one case (cell type 2) apparently switching off a UV-sensitive input.     

Unconventional ultraviolet sensitivity spectra of Ascalaphus (Insecta,Neuroptera)

The spectral sensitivity of 21 eye preparations of Ascalaphus (Libelluloides) macaronius (Insecta, Neuroptera) has been re-measured using an up-to-date spectral scan method. 1. Dorso-frontal and ventro-lateral eyes have different spectral characteristics with peaks of sensitivity at 329 ± 8 nm (n = 15) and 343 ± 4 nm (n = 5) (P = 0.002), respectively. 2. The absorbance of the visual pigment layer, K, determined from the shape of the spectral sensitivity curves is 1.3 ± 1.8(n = 15) for dorso-frontal eyes and – 1.0 ± 0.3(n = 5) for ventrolateral eyes, thus implying higher selfscreening in the dorso-frontal eyes and narrowing of the spectral sensitivity curves as regards to a template visual pigment in ventro-lateral eyes. 3. Plotting K versus spectral sensitivity peak wavelength _max revealed an inverse correlation between these variables with K = 42.5 – 0.126 _max at r = 0.88(n = 19). 4. Extracts of ommochromes and carotenoids (Figs. 4 to 6) do not allow to account for the above diversity of optical properties of the Ascalaphus eye (Fig. 7).Abbreviations SSC spectral sensitivity curve - DF dorso-frontal eye - UV ultraviolet - VL ventro-lateral eye     

Spectral sensitivities of photoreceptors and their role in colour discrimination in the green-backed firecrown hummingbird (<Emphasis Type="Italic">Sephanoides sephaniodes</Emphasis>)

We studied the photopic spectral sensitivity in the green-backed firecrown, Sephanoides sephaniodes, a South American hummingbird, and its possible ecological relationship with preferred flowers and body colouration. Avian colour vision is in general tetrachromatic with at least four types of cones, which vary in sensitivity from the near ultraviolet (UV) to the red wavelength range. Hummingbirds represent an important family of birds, yet little is known about their eye sensitivity, especially about the role of photoreceptors and their oil droplet complements. The photopic electroretinogram shows a main sensitivity peak at 560 nm and a secondary peak in the UV, and may be explained by the presence of four single cones (lambda (max) at ~370, 440, 508 and 560 nm), and a double cone (lambda (max) at 560 nm) screened by oil droplets. The flowers preferred by the firecrown are those in which the red-green wavelength region predominates and have higher contrast than other flowers. The crown plumage of males is highly iridescent in the red wavelength range (peak at 650 nm) and UV; when plotted in a high-dimensional tetrachromatic space, it falls in a "red + UV" purple hue line, suggesting a potential significant communication signal for sexual differentiation.     

Unexpectedly low UV-sensitivity in a bird,the budgerigar

Photoreceptor adaptation ensures appropriate visual responses during changing light conditions and contributes to colour constancy. We used behavioural tests to compare UV-sensitivity of budgerigars after adaptation to UV-rich and UV-poor backgrounds. In the latter case, we found lower UV-sensitivity than expected, which could be the result of photon-shot noise corrupting cone signal robustness or nonlinear background adaptation. We suggest that nonlinear adaptation may be necessary for allowing cones to discriminate UV-rich signals, such as bird plumage colours, against UV-poor natural backgrounds.     

Spectral sensitivity of the accessory optic system of the pigeon

When an animal is moving relative to its surroundings it can nevertheless stabilize the image on the retina, at least partially, by means of the large-field optomotor response. In the animal species investigated so far, this response has been found to be colour-blind as indicated by grey-matching tests, and to involve only photoreceptors sensitive in the long-wavelength region of the spectrum. Here we show that this rule also applies to pigeons, i.e. birds, a group not previously studied in this regard. Accepted: 4 February 1998     

千岛湖陆桥岛屿鸟类集团对栖息地片段化的敏感性及其季节变化

为探究千岛湖陆桥岛屿不同鸟类集团对栖息地片段化敏感性的差异和季节变化,于2009年4月—2012年1月鸟类繁殖季(4、5、6月)和冬季(11、12、1月)对千岛湖41个陆桥岛屿鸟类集团进行了研究。结果表明,冬季杂食鸟对片段化敏感性高于食虫鸟,繁殖季时二者无显著差异,繁殖季和冬季时下层鸟对片段化敏感性均高于林冠鸟,冬季留鸟对片段化敏感性高于候鸟,繁殖季则无显著差异。杂食鸟和留鸟对片段化敏感性存在季节差异,而食虫鸟、林冠鸟、下层鸟和候鸟对片段化敏感性均无季节差异。不同鸟类集团对栖息地片段化敏感性的差异和季节变化规律,有助于人们在栖息地管理和保护区设计时采取更有针对性的鸟类保护措施。     

Spectral responses and chromatic processing in the dragonfly lamina

The dragonfly Hemicordulia tau has five spectral classes of photoreceptor which drive five lamina monopolars, m1-m5. The monopolars encode spectral information. Here, spectral coding by m2, m4 and m5 are described. m2 is the most sensitive to dim light. m4 and m5 are less sensitive than m2, and so we call them photopic cells. The effects of selective adaptation of receptor inputs to m4 and m5 are unusual. For example, in m4 adaptation of the green receptor suppresses the UV input, but green sensitivity is unaffected, while green adaptation of m5 increases its green sensitivity. In m5 the dark adapted spectral tuning resembles the 520 nm receptor, but on adaptation to 430 nm light this narrows markedly. Adaptation either of green or of UV receptor input to m2 and m4 modifies the time course of responses both to green and to UV, implying that changes in the time courses of monopolar responses with adaptation state do not directly reflect receptor responses (Fig. 2). Finally, the antagonistic surround of m2 is UV sensitive, and of m4 green sensitive (Fig. 3).Abbreviations LMC large monopolar cell - LVF long visual fibre - rf receptive field - SVF short visual fibre     

Visual modelling suggests a weak relationship between the evolution of ultraviolet vision and plumage coloration in birds

Birds have sophisticated colour vision mediated by four cone types that cover a wide visual spectrum including ultraviolet (UV) wavelengths. Many birds have modest UV sensitivity provided by violet‐sensitive (VS) cones with sensitivity maxima between 400 and 425 nm. However, some birds have evolved higher UV sensitivity and a larger visual spectrum given by UV‐sensitive (UVS) cones maximally sensitive at 360–370 nm. The reasons for VS–UVS transitions and their relationship to visual ecology remain unclear. It has been hypothesized that the evolution of UVS‐cone vision is linked to plumage colours so that visual sensitivity and feather coloration are ‘matched’. This leads to the specific prediction that UVS‐cone vision enhances the discrimination of plumage colours of UVS birds while such an advantage is absent or less pronounced for VS‐bird coloration. We test this hypothesis using knowledge of the complex distribution of UVS cones among birds combined with mathematical modelling of colour discrimination during different viewing conditions. We find no support for the hypothesis, which, combined with previous studies, suggests only a weak relationship between UVS‐cone vision and plumage colour evolution. Instead, we suggest that UVS‐cone vision generally favours colour discrimination, which creates a nonspecific selection pressure for the evolution of UVS cones.     

Spectral sensitivity of the photonegative reaction of the blood-sucking bug Triatoma infestans (Heteroptera: Reduviidae)

We studied the spectral sensitivity of the visual system of the blood-sucking bug Triatoma infestans, one of the main vectors of Chagas Disease in South America. We quantified the photonegative reaction of this insect in a rectangular arena, half of which was kept dark and the other half illuminated with various intensities of different monochromatic lights (or broadband stimuli for λ>665 nm). As a behavioral parameter of the photonegative response, we measured the time each insect spent in the dark half of the arena. We found that low intensity levels (under 0.06 μW/cm²) of monochromatic lights of 397, 458, 499, and 555 nm evoked a statistically significant (i.e., different from that of control groups) photonegative reaction. Insects were less sensitive to monochromatic lights of 357 nm (UV) and 621 nm (dark orange), and to broadband stimuli in the red part of the spectrum (665–695 nm). These findings indicate that the visual system of T. infestans is sensitive to broader regions of the spectrum than those previously reported.     

Urban noise and the cultural evolution of bird songs

In urban environments, anthropogenic noise can interfere with animal communication. Here we study the influence of urban noise on the cultural evolution of bird songs. We studied three adjacent dialects of white-crowned sparrow songs over a 30-year time span. Urban noise, which is louder at low frequencies, increased during our study period and therefore should have created a selection pressure for songs with higher frequencies. We found that the minimum frequency of songs increased both within and between dialects during the 30-year time span. For example, the dialect with the highest minimum frequency is in the process of replacing another dialect that has lower frequency songs. Songs with the highest minimum frequency were favoured in this environment and should have the most effective transmission properties. We suggest that one mechanism that influences how dialects, and cultural traits in general, are selected and transmitted from one generation to the next is the dialect''s ability to be effectively communicated in the local environment.     

Spectral gradients of downwelling light in a fluvial lake (Lake Saint-Pierre, St-Lawrence River)

Large fluvial lakes are understudied with respect to their underwaterlight climates. Fluvial lakes pose unique challenges for photobiologistsinterested in the interactions amongst light climate, nutrients and microbialcommunity structure and biodiversity. This is because fluvial lakes are typifiedby highly dynamic flow regimes often incorporating different inflows anddischarges each characterized by their own unique physico-chemical composition.These compositional characteristics include the concentrations of chromophoricdissolved organic matter (CDOM), suspended solids, and pigments such aschlorophyll. Together these factors contribute to the distribution andcomposition of the water masses that make up fluvial lakes. These water masses,in turn, flow over lakebeds that are typically complex in their morphometry andfeature extensive macrophyte beds, further enhancing the habitat heterogeneityof these ecosystems. We here report on the spectral attenuation of ultravioletradiation (UVR = 280–400 nm) and photosyntheticallyactive radiation (PAR = 400–700 nm) in the three mainwater masses of Lake Saint-Pierre and evaluate the relative contribution ofCDOM, and particulate organic material to UVR attenuation. We demonstrate thatUVR penetrates 18 to 30% of the water column (1% penetration depth) in the LakeSaint-Pierre ecosystem, and show how the underwater spectral UVR varies withinthe three water masses.     

Photoreceptor spectral sensitivity of the compound eyes of black soldier fly (Hermetia illucens) informing the design of LED-based illumination to enhance indoor reproduction

Mating in the black soldier fly (BSF) is a visually mediated behaviour that under natural conditions occurs in full sunlight. Artificial light conditions promoting mating by BSF were designed based on the spectral characteristics of the compound eye retina. Electrophysiological measurements revealed that BSF ommatidia contained UV-, blue- and green-sensitive photoreceptor cells, allowing trichromatic vision. An illumination system for indoor breeding based on UV, blue and green LEDs was designed and its efficiency was compared with illumination by fluorescent tubes which have been successfully used to sustain a BSF colony for five years. Illumination by LEDs and the fluorescent tubes yielded equal numbers of egg clutches, however, the LED illumination resulted in significantly more larvae. The possibilities to optimize the current LED illumination system to better approximate the skylight illuminant and potentially optimize the larval yield are discussed.     

Spectral sensitivity of the compound eyes in two day-active fireflies (Coleoptera: Lampyridae: Lucidota)

Summary The electroretinographic visual spectral sensitivity functions in day-active fireflies Lucidota luteicollis and Lucidota atra show a broad green sensitivity and a shoulder in the near-ultraviolet region of the spectrum (Figs. 1, 2) as is commonly found among day-active insects. The nomogram for P530 visual pigment matches the spectral sensitivity curves in the green. The adult L. luteicollis retains its larval bioluminescent light organ which has a peak emission at 562 nm. The _max of the ERG spectral sensitivity does not match the bioluminescent peak (Fig. 1B) as it does in twilight- and dark-active fireflies. Some relevant behavioural observations with respect to mating are presented.     

Urban bird declines and the fear of cats

The role of domestic cats Felis catus in the troubling, on-going decline of many urban bird populations in the UK is controversial. Debate, in the UK and elsewhere, has centred on the level of avian mortality directly imposed by cats, and on whether this is principally compensatory (the 'doomed surplus' hypothesis) or additive (the 'hapless survivor' hypothesis). However, it is well established that predators also have indirect, sub-lethal effects on their prey where life-history responses to predation risk affect birth and death rates. Here, using a simple model combining cat predation on birds with a sub-lethal (fear) effect of cat density on bird fecundity, we show that these sub-lethal effects may be substantial for urban songbirds. When cat densities are as high as has been recorded in the UK, and even when predation mortality is low (e.g. <1%), a small reduction in fecundity due to sub-lethal effects (e.g. <1 offspring year⁻¹ cat⁻¹) can result in marked decreases in bird abundances (up to 95%). Thus, low predation rates in urban areas do not necessarily equate with a correspondingly low impact of cats on birds. Sub-lethal effects may depress bird populations to such an extent that low predation rates simply reflect low prey numbers.     

微山湖鸟类多样性特征及其影响因子

2010年10月至2011年9月期间,使用样线法对微山湖鸟类多样性进行研究.共发现鸟类132种,隶属13目39科,其中留鸟39种,夏候鸟33种,冬候鸟14种,旅鸟46种,分别占全部种类的29.6％、25.0％、10.6％和34.85％;国家二级保护鸟类有12种,省级重点保护鸟类16种,另外50种和16种鸟类分别列入中日、中澳候鸟保护协定.灰鹤、乌雕、沙鵖和白顶鵖4种鸟类在南四湖首次记录.根据微山湖的地理和植被状况,将研究区域划分为水域、次生林、农田和居民区4生境,不同生境中鸟类群落的Shannon-Wiener指数高低为沼泽水域＞次生林＞农田＞居民区,Pielou指数高低为沼泽水域＞农田＞次生林＞居民区.次生林和农田鸟类群落的相似性指数最高,沼泽水域与居民区的相似性最低.春季末期鸟类多样性指数和均匀性指数最高,秋季末期最低.冬季鸟类种类最多、密度最大,春初鸟类种类最少、密度最小.距居民区的距离、距公路的距离、植被盖度、人工池塘数目、水面积比例和深水面积比例等对鸟类多样性影响显著.     

长江师范学院校园夏季鸟类群落与多样性分析

2008年3～7月采用样线法对长江师范学院李渡校园鸟类组成和种群数量进行了调查,共记录鸟类6目21科28种,数量1633只,物种多样性指数为3．9204,均匀性指数为1．1765,其中国家“三有”名录鸟类25种,CITES名录鸟类1种。鸟类区系以东洋界成分为主。对不同生境鸟类多样性的分析结果表明：（1）乔灌林鸟类多样性指数和均匀性指数最高,水域鸟类多样性指数最低,建筑区均匀性指数最低;（2）乔灌林与竹林的相似性指数最高,竹林与水域的相似性最低。     

UV photoreceptors in the compound eye of Daphnia magna (Crustacea,Branchiopoda). A fourth spectral class in single ommatidia

Summary The spectral sensitivities of individually stimulated ommatidia in the compound eye of Daphnia magna were measured using a fast spectral scan voltage-clamp technique with extracellular recording. Chromatic adaptation was used to reveal the contributions of individual spectral classes of photoreceptors to the ommatidial sensitivity. Ommatidia in the dorsal and ventral regions of the compound eye were tested. Four spectral classes of photoreceptors were found in each ommatidium, among them a previously undetected class with peak sensitivity in the ultraviolet. The wavelengths of peak sensitivity were at 348, 434, 525, and 608 nm for the dorsal ommatidia. The three longer wavelength classes agreed well with those found previously by intracellular recording (Schehr 1984). Only small differences in wavelength and magnitude of peak sensitivity were found between the four classes in the dorsal versus ventral ommatidia.