A comparison of electrophysiologically determined spectral responses in 35 species of Lepidoptera

Spectral responses from the compound eyes of 35 lepidopteran species representing 14 families were investigated electrophysiologically using ERG recordings. The light-stimuli used overed the range of 383–700 nm wavelengths. All species show three or four maxima in their spectral sensitivity curves. Two of these peaks were usually associated with ultraviolet and blue light (383 and 460 nm, respectively). The other maxima occurred in the 500–620 nm region. In Nymphalidae the highest peak was found in response to 560–580 nm stimuli. Of all wavelengths tested, these are the longest wavelengths to produce principal peak sensitivities.Pieridae and Lycaenidae have maxima in the UV region which represent significantly higher sensitivities than the secondary peaks to stimuli of longer wavelengths.Satyridae, Danaidae, Hesperiidae and diurnal moths except Epicopeia (Epicopeidae) generally have similar sensitivity curves with principal peaks between 500 and 520 nm.In Papilionid species except Graphium (max = 560 nm) high maxima occur in the UV and blue (460 nm) region.Noctural Sphingid moths possess the highest peak sensitivity at 540 nm. All other noctural moths tested have three or four maxima.     

Photoreceptor visual fields, ommatidial array, and receptor axon projections in the polarisation-sensitive dorsal rim area of the cricket compound eye

We made intracellular recordings from the photoreceptors of the polarisation-sensitive dorsal rim area of the cricket compound eye combined with dye marking. By measuring visual field sizes and optical axes in different parts of the dorsal rim area, we assessed the optical properties of the ommatidia. Due to the large angular sensitivities (median about 20°) and the high sampling frequency (about 1 per degree), the visual fields overlap extensively, such that a given portion of the sky is viewed simultaneously by a large number of ommatidia. By comparing the dye markings in the retina and in the optic lobe, the axon projections of the retinula cells were examined. Receptors R1, R2, R5 and R6 project to the lamina, whereas R7 projects to the medulla. The microvilli orientation of the two projection types differ by 90° indicating the two analyser channels that give antagonistic input to polarisation-sensitive interneurons. Using the retinal marking pattern as an indicator for the quality of the intracellular recordings, the polarisation sensitivity of the photoreceptors was re-examined. The polarisation sensitivity of recordings from dye-coupled cells was much lower (median: 4.5) than that of recordings in which only one cell was marked (median: 9.8), indicating that artefactual electrical coupling between photoreceptors can significantly deteriorate polarisation sensitivity. The physiological value of polarisation sensitivity in the cricket dorsal rim area is thus typically about 10. Accepted: 4 November 1999     

An exceptionally well-preserved Eocene dolichopodid fly eye: function and evolutionary significance

The exceptionally preserved eyes of an Eocene dolichopodid fly contained in Baltic amber show remarkable detail, including features at micrometre and submicrometre levels. Based on this material, we establish that it is likely that the neural superposition compound eye existed as far back as 45 Ma. The ommatidia have an open rhabdom with a trapezoidal arrangement of seven rhabdomeres. Such a structure is uniquely characteristic of the neural superposition compound eye of present-day flies. Optical analysis reveals that the fossil eyes had a sophisticated and efficient optical system.     

Properties of pupil mechanisms in owl-fly Ascalaphus macaronius (Neuroptera)

Regulation of light flux by pupil mechanisms in the UV-sensitive superposition eye of owl-fly Ascalaphus macaronius (Neuroptera) was studied with a fast reflection microspectrophotometric technique. The spectral sensitivity of pupil reaction, which was calculated on the basis of changes of transient amplitude reflection, was almost identical with the one of Deilephila eye. This indicates that in spite of different life styles and spectral sensitivities of photoreceptors, pupil closing is triggered by the same photosensitive structure in both eyes. By measuring the spectra of reflected light from the Ascalaphus eye between 400 and 700 nm after different dark periods following light stimulation, it was established that the restoration of reflection was much faster in the red than in the blue spectral range. Based on this, we propose that two different pupil mechanisms with different spectral absorption characteristics are involved in light-flux regulation. Fast-reacting pupil is probably represented by screening pigment migration in the secondary pigment cells and a slow blue-absorbing system by the activity in primary pigment cells. The importance of two different pupils for the photoregeneration of visual pigment is discussed. Accepted: 1 October 1998     

Visual navigation in starfish: first evidence for the use of vision and eyes in starfish

Most known starfish species possess a compound eye at the tip of each arm, which, except for the lack of true optics, resembles an arthropod compound eye. Although these compound eyes have been known for about two centuries, no visually guided behaviour has ever been directly associated with their presence. There are indications that they are involved in negative phototaxis but this may also be governed by extraocular photoreceptors. Here, we show that the eyes of the coral-reef-associated starfish Linckia laevigata are slow and colour blind. The eyes are capable of true image formation although with low spatial resolution. Further, our behavioural experiments reveal that only specimens with intact eyes can navigate back to their reef habitat when displaced, demonstrating that this is a visually guided behaviour. This is, to our knowledge, the first report of a function of starfish compound eyes. We also show that the spectral sensitivity optimizes the contrast between the reef and the open ocean. Our results provide an example of an eye supporting only low-resolution vision, which is believed to be an essential stage in eye evolution, preceding the high-resolution vision required for detecting prey, predators and conspecifics.     

The sophisticated visual system of a tiny Cambrian crustacean: analysis of a stalked fossil compound eye

Fossilized compound eyes from the Cambrian, isolated and three-dimensionally preserved, provide remarkable insights into the lifestyle and habitat of their owners. The tiny stalked compound eyes described here probably possessed too few facets to form a proper image, but they represent a sophisticated system for detecting moving objects. The eyes are preserved as almost solid, mace-shaped blocks of phosphate, in which the original positions of the rhabdoms in one specimen are retained as deep cavities. Analysis of the optical axes reveals four visual areas, each with different properties in acuity of vision. They are surveyed by lenses directed forwards, laterally, backwards and inwards, respectively. The most intriguing of these is the putatively inwardly orientated zone, where the optical axes, like those orientated to the front, interfere with axes of the other eye of the contralateral side. The result is a three-dimensional visual net that covers not only the front, but extends also far laterally to either side. Thus, a moving object could be perceived by a two-dimensional coordinate (which is formed by two axes of those facets, one of the left and one of the right eye, which are orientated towards the moving object) in a wide three-dimensional space. This compound eye system enables small arthropods equipped with an eye of low acuity to estimate velocity, size or distance of possible food items efficiently. The eyes are interpreted as having been derived from individuals of the early crustacean Henningsmoenicaris scutula pointing to the existence of highly efficiently developed eyes in the early evolutionary lineage leading towards the modern Crustacea.     

Dual Sensitivities of Cells in Wolf Spider Eyes at Ultraviolet and Visible Wavelengths of Light

Intracellular recordings have been made from visual cells in principal and secondary eyes of in vitro wolf spider preparations. The responses of all cells to all wavelengths of light were graded depolarizations; no hyperpolarizations or nerve discharges were seen. Cells in a secondary eye, the anterior lateral eye, had a maximum sensitivity in the visible at 510 nm and a secondary maximum, or shoulder, of sensitivity in the near ultraviolet at 380 nm. Cells in principal eyes, the anterior median eyes, all responded maximally both in the visible at 510 nm and in the ultraviolet at 360–370 nm or less. However, there was no typical ratio of ultraviolet to visible sensitivities; the differences in log sensitivities (log UV/VIS) varied from 3.3 to -0.5. Each principal eye had a population of cells with different ratios. These populations varied with the time of the year, possibly due to changes in light upon the animals. Chromatic adaptations of cells in anterior median (but not anterior lateral) eyes resulted in small, selective changes in spectral sensitivities, and there was some facilitation of responses from cells repeatedly stimulated. It is concluded that cells of secondary eyes contain only a visual pigment absorbing maximally in the visible, while cells of principal eyes probably contain variable amounts of both this pigment and one absorbing in the ultraviolet as well.     

Boltzmann relation reliability in optical temperature sensing based on upconversion studies of Er3+/Yb3+ co-doped PZT ceramics

The fluorescence intensity ratio (FIR) of two thermally coupled levels with temperature follows the Boltzmann equation and shows an exponential nature to the temperature that is purely dependent on the energy difference between the levels. Despite the identical energy difference between the thermally coupled levels, researchers have observed varying sensitivities for various samples. In this article, the FIR and sensitivities were calculated using the Boltzmann equation by changing various parameters such as energy difference (ΔE) and the value of the constant C. The results were compared with various reports for Er³⁺/Yb³⁺ ions. After analysis, a new polynomial fit equation was used to determine the temperature sensitivities for the Er³⁺/Yb³⁺ co-doped PbZrTiO₃ phosphor in lieu of the conventional Boltzmann equation. The polynomial fit equation eliminated the dependency of the sensitivity on the inverse of the FIR factor and a flat sensitivity curve was obtained with temperature.     

The visual ecology of pupillary action in superposition eyes

The two most common mechanisms of pupillary screening-pigment migration in arthropod superposition eyes are the cone and longitudinal pigment migration mechanisms. The dynamics of each were investigated by optical modelling and by determining experimentally the relationship between eye glow brightness and screening pigment position within the eyes of two representative insect species: the noctuid moth Agrotis infusa and the dung beetle Copris elphenor. During dark adaptation, in both mechanisms, the screening pigment is contracted distally to expose the proximal half of each crystalline cone. During light adaptation the pigment migrates proximally and reduces light flux in the retina. In the longitudinal mechanism, pigment migrates into the clear zone of the eye. In the cone mechanism, pigment never enters the clear zone and is instead restricted to the proximal half of each crystalline cone: a migrating sleeve of pigment creates a small aperture at the end of the crystalline cone, the area of which depends on the degree of light adaptation. According to the model, the cone mechanism provides a limited range of light attenuation (ca. 0.6 log units) for which both good spatial resolution and accuracy of control are maintained, and within this range attenuation is controlled very finely. Beyond this range, whilst attenuation is still possible, diffraction at the pigment aperture and increasing coarseness of control worsen visual performance significantly. In contrast, the longitudinal mechanism provides a much larger useful range of light attenuation (up to several log units) and maintains reasonable fineness of attenuation control over the entire range (although not as fine as the cone mechanism). The experimental results support the model. An extensive survey of arthropods with superposition eyes reveals that the cone mechanism is almost exclusively possessed by those animals experiencing a narrow range of light intensities, and the longitudinal mechanism by those experiencing a wide range.Dedicated to Professor Rolf Elofsson on the occasion of his retirement from the Chair of Zoology in Lund     

Punctal plugs versus artificial tears for treating dry eye: a comparative observation of their effects on contrast sensitivity

This study aimed to compare the effects of treatment with punctal plugs versus artificial tears on visual function and tear film stability for dry eye. A total of 56 consecutive eyes of 28 dry eye patients observed at our clinic from May to October in 2009 were divided into two groups. One group (32 eyes of 16 patients) was treated with artificial tears, and punctal plugs were used in the other group (24 eyes of 12 patients). A questionnaire was used in these patients before treatment and was repeated 2 weeks after treatment. Fluorescent staining for tear film break-up time (BUT), the Schirmer test I (STI), and contrast sensitivity was performed at the same time. The questionnaire indicated that all patients complained about the uncomfortable symptoms associated with dry eye. These symptoms were relieved after the application of artificial tears or punctal plugs, and there was no significant difference between these two groups. We found that the corneal fluorescent staining disappeared after treatment. The BUT was improved significantly after treatment in both groups, but the improvement was greater in patients who received punctal plugs than those that received artificial tears. There was no remarkable change in the STI in the artificial tears group, but a significant change was observed in the punctal plugs group. The contrast sensitivities were greatly improved in simulated daylight, night, and glare disability conditions after treatment with artificial tears and punctal plugs. However, the changes in contrast sensitivity did not significantly differ between groups. Both artificial tears and punctal plugs relieved dry eye symptoms, repaired corneal lesions, enhanced tear film stability, and improved contrast sensitivity. Punctal plugs could improve tear film stability and elongate the BUT better than artificial tears.     

Imaging depth extension of optical coherence tomography in rabbit eyes using optical clearing agents

Optical coherence tomography has become an indispensable diagnostic tool in ophthalmology for imaging the retina and the anterior segment of the eye. However, the imaging depth of optical coherence tomography is limited by light attenuation in tissues due to optical scattering and absorption. In this study of rabbit eye both ex vivo and in vivo, optical coherence tomography imaging depth of the anterior and posterior segments of the eye was extended by using optical clearing agents to reduce multiple scattering. The sclera, the iris, and the ciliary body were clearly visualized by direct application of glycerol at an incision on the conjunctiva, and the posterior boundary of sclera and even the deeper tissues were detected by submerging the posterior segment of eye in glycerol solution ex vivo or by retro-bulbar injection of glycerol in vivo. The ex vivo rabbit eyes recovered to their original state in 60 s after saline-wash treatment, and normal optical coherence tomography images of the posterior segment of the sample eyes proved the self-recovery of in vivo performance. Signal intensities of optical coherence tomography images obtained before and after glycerol treatment were compared to analysis of the effect of optical clearing. To the best of our knowledge, this is the first study for imaging depth extension of optical coherence tomography in both the anterior and posterior segments of eye by using optical clearing agents.     

Superposition optics and the time of flight in onitine dung beetles

Dung beetles fly to fresh dung, with vision essential for flight navigation. The daily period of flight varies among different species: some beetles fly only in sunlight, others only when ambient light levels change rapidly during dusk or dawn and others in the constant dark of night. Measurements of the optical properties of the lenses, eye geometry and photoreceptor dimensions were used in a computer ray-tracing model to determine the optical performance of the superposition eyes of nine species of onitine dung beetles. Eye sensitivity to light is determined mainly by body size, by the refractive-index parameters and size of the crystalline cones, and by the photoreceptor dimensions. Based on the optics of the ommatidial lenses and absorption of light in the retina, the most sensitive eyes, found in the crepuscular-nocturnal beetles, are 85 times or nearly two log units more sensitive than the eyes of the diurnal beetles. Three possible criteria are considered to determine the best position for the retina: maximum amount of light absorbed in the target rhabdom; maximum amount of light falling on the target rhabdom (best focus); and maximum resolution. The structure and physiological optics of the superposition compound eyes of an onitine dung beetle are matched to the range of light intensities at which it flies. Accepted: 4 February 1998     

柚木野螟成虫复眼外部形态和超微结构观察

【目的】柚木野螟Eutectona machaeralis主要取食危害珍贵树种柚木。本研究旨在观察研究柚木野螟成虫复眼的形态、组织结构和超微结构,分析其复眼结构特征,为更好了解该物种复杂的视觉行为与感光、趋光机制的关系奠定基础。【方法】运用光学显微镜以及扫描和透射电子显微镜技术观察了柚木野螟成虫复眼的形态、组织结构和超微结构。【结果】柚木野螟成虫复眼着生于头部触角基部,呈椭球形,属对称性复眼。雌、雄成虫复眼分别有2 300~2 755和1 950~2 316个小眼。小眼呈正六边形,表面密被角膜乳突,间隙偶有感觉毛。每个小眼由1个角膜、4个晶锥细胞、1对初级色素细胞,6个次级色素细胞、不同水平面分布的12个视网膜细胞和基膜等组成。沿小眼纵轴11个视网膜细胞的向心侧细胞膜特化成细丝状微绒毛,形成放射状排列的视小杆,组合呈融合型视杆;第12个视网膜细胞位于小眼基部。基膜上方,视网膜细胞和次级色素细胞末端膨大,以轴突形式穿过基底膜。【结论】柚木野螟复眼为典型的重叠像眼,雌、雄成虫小眼排列方式及内部结构无明显差异,但雌、雄虫小眼数量和大小具有明显的性二型现象。     

The posterior median eyes of the dinopid spider Menneus

Summary The posterior median (pm) eyes of the dinopid spider Menneus unifasciatus L. Koch are described and compared with the pm eyes of Dinopis, which are highly specialised for night vision. The lenses of Menneus have F-numbers of 0.72 compared to 0.58 in Dinopis, the distance between receptors is ca. 4.0 m compared to 20–22 m for Dinopis, and image quality is matched to receptor spacing. The lens of Menneus is simple, while that of Dinopis comprises two components of different refractive indices (Blest and Land 1977). Receptive segments of the pm eyes of Dinopis are hexagonal in transverse section and those of adjacent cells are tightly contiguous, allowing the possibility of both optical and electrical coupling (Blest 1978). Receptive segments of Menneus are separated from each other by glial processes containing little pigment, and each segment possesses two rhabdomeres on opposite faces of the cell. Rhabdomere volumes undergo a daily cycle similar to that described for Dinopis, but of relatively minor extent. It is shown that the pm eye of Dinopis could have evolved from that of Menneus by a simple series of transformations, and that a gain of two logarithmic units of sensitivity can be attributed to changes in optical design alone.The authors thank Professor D.T. Anderson, F.R.S. for use of field facilities at the Crommelin Biological Field Station of Sydney University at Warrah, Pearl Beach, N.S.W. and Andrew and Sally Austin and Sally Stowe for help in the field. We are indebted to Rod Whitty and the Electron Microscopy Unit for advice and support throughout these studies. Chris Snoek prepared Fig. 1B-D     

复眼透镜光学信息保密编码及译码的研究——Ⅰ.昆虫复眼成像特性及编、译码技术原理

本文根据光学并列型和光学重叠型两类昆虫复眼的屈光系统,具有分解和综合二维图像的光学特性,提出了一种新的用复眼透镜实现二维图像光学信息编码和译码的技术原理.利用复眼透镜和一个特制的随机抽样编码的掩模板,可将一幅有序的二维图像(或者文献、资料等)编码形成为一幅无序的,具有良好保密性能的分解编码像,而且,还能将此编码像反演综合再现出原始图像.它不仅实现了对二维图像信息的多通道并行处理,而且还具有传输量大、速度快、保密性强等优点.我们利用此种复眼透镜光学信息编、译码的技术原理,对二维图像的光学信息进行了分解编码记录及综合译码再现.     

The amphipod Gammarus minus has larger eyes in freshwater springs with numerous fish predators

Abstract. Intraspecific variation in eye size in relation to ecological factors has not been well studied. Here, for the first time, we show that larger eyes in a freshwater crustacean may be associated with the presence of predators. In central Pennsylvania (USA), individuals of the amphipod crustacean Gammarus minus have significantly larger eyes in two freshwater springs with numerous fish predators (Cottus cognatus) than in three springs with few or no fish predators. Although we do not know the precise causes of these differences, this study and previous work on cave populations of G. minus suggest that eye size is an evolutionarily malleable trait that may respond to multiple selection pressures, either directly or indirectly. Three plausible explanations for the eye‐size variation observed among our study populations include (1) larger eyes may enable amphipods to better detect and avoid fish predators, (2) fish predation favors nocturnal or shallow interstitial activity that is facilitated by larger, more light‐sensitive eyes, or (3) the presence of fishes is associated with other environmental factors that may favor relatively large eyes. Available evidence suggests that the first hypothesis is the most viable explanation, but further study is required.     

Phototaxis in Drosophila: R1–6 input and interaction among ocellar and compound eye receptors

All 3 photoreceptor types in the compound eye of Drosophila can evoke positive phototaxis. Here we describe input from R1–6 receptors which are very sensitive. Previous reports in this series of studies described input from R7 and R8, the other less sensitive receptors. Here we studied fast-walking phototaxis using extremely dim stimuli. We also studied input from the simple ocellar eyes. Thus, we can now summarize a complete synthesis of inputs and interactions among all compound eye and ocellar receptor types. Receptor-deficient mutants were used to establish receptor-specific input. Two other findings are presented: (1) eye colour pigments affect the spectral sensitivity for phototaxis; and (2) the ocelli interact to facilitate input from the compound eye receptor types. Possible mechanisms of receptor interaction are discussed in the light of these findings of positive input from all photoreceptor types in Drosophila.     

复眼透镜光学信息保密编码及译码的研究——Ⅰ.昆虫复眼成像特性及编、译码技术原理

本文根据光学并列型和光学重叠型两类昆虫复眼的屈光系统,具有分解和综合二维图像的光学特性,提出了一种新的用复眼透镜实现二维图像光学信息编码和译码的技术原理.利用复眼透镜和一个特制的随机抽样编码的掩模板,可将一幅有序的二维图像(或者文献、资料等)编码形成为一幅无序的,具有良好保密性能的分解编码像,而且,还能将此编码像反演综合再现出原始图像.它不仅实现了对二维图像信息的多通道并行处理,而且还具有传输量大、速度快、保密性强等优点.我们利用此种复眼透镜光学信息编、译码的技术原理,对二维图像的光学信息进行了分解编码记录及综合译码再现.     

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     

Photoreceptor spectral sensitivities in terrestrial animals: adaptations for luminance and colour vision

This review outlines how eyes of terrestrial vertebrates and insects meet the competing requirements of coding both spatial and spectral information. There is no unique solution to this problem. Thus, mammals and honeybees use their long-wavelength receptors for both achromatic (luminance) and colour vision, whereas flies and birds probably use separate sets of photoreceptors for the two purposes. In particular, we look at spectral tuning and diversification among 'long-wavelength' receptors (sensitivity maxima at greater than 500 nm), which play a primary role in luminance vision. Data on spectral sensitivities and phylogeny of visual photopigments can be incorporated into theoretical models to suggest how eyes are adapted to coding natural stimuli. Models indicate, for example, that animal colour vision--involving five or fewer broadly tuned receptors--is well matched to most natural spectra. We can also predict that the particular objects of interest and signal-to-noise ratios will affect the optimal eye design. Nonetheless, it remains difficult to account for the adaptive significance of features such as co-expression of photopigments in single receptors, variation in spectral sensitivities of mammalian L-cone pigments and the diversification of long-wavelength receptors that has occurred in several terrestrial lineages.