A novel eye in 'eyeless' shrimp from hydrothermal vents of the Mid-Atlantic Ridge

Rimicaris exoculata is a shrimp that swarms over high-temperature (350 degrees C) sulphide chimneys at Mid-Atlantic Ridge hydrothermal fields (3,600 m). This shrimp lacks an externally differentiated eye, having instead a pair of large organs within the cephalothorax immediately beneath the dorsal surface of the transparent carapace, connected by large nerve tracts to the supraesophageal ganglion. These organs contain a visual pigment with an absorption spectrum characteristic of rhodopsin. Ultrastructural evidence for degraded rhabdomeral material suggests the presence of photoreceptors. No image-forming optics are associated with the organs. We interpret these organs as being eyes adapted for detection of low-level illumination and suggest that they evolved in response to a source of radiation associated with the environment of hydrothermal vents.     

The visibility of 350 degrees C black-body radiation by the shrimp Rimicaris exoculata and man

The eye of the 'eyeless' shrimp Rimicaris exoculata is unusual in having no image-forming optics and a high concentration of rhodopsin. The shrimps swarm around 350 degrees C hydrothermal 'black smoker' vents in the Mid-Atlantic Ridge. There is no other known source of visible light in the shrimp's environment. The spectral sensitivity of rhodopsin is well matched to typical spectra of bioluminescence of organisms found at lesser depths, but other animals detect such emissions without the unusual features of the R. exoculata eye. These two features are most easily understood as an adaptation for the detection of extremely faint sources of light. Physical calculations presented here indicate that the shrimp could see the black-body radiation of the 350 degrees C vents, even though these sources are practically invisible to the human eye. This would be useful to the shrimp as it feeds on sulphide-loving bacteria very near to the vents but must avoid the lethal 350 degrees C vents themselves.     

红光下染料敏化重铬酸盐明胶形成的全息图

重铬酸盐明胶(DCG)是一种重要的全息记录材料,它有高的衍射率和低的噪声,其衍射率之高几乎可接近理论值。它的主要缺点是光敏性差,对波长大于540nm的尤基本上不感光,加入一些染料可使其感光区扩大到红光(633nm)。本文讨论了用亚甲基兰敏化重铬酸盐明胶扩大到红光区的方法,用He—Ne激光得到衍射率为80%的全息图。     

Retinal receptors in rodents maximally sensitive to ultraviolet light

High sensitivity to near-ultraviolet light is a fundamental feature of vision in many invertebrates. Among vertebrates there are some amphibians, birds and fishes that are also sensitive to near-ultraviolet wavelengths. This sensitivity can be achieved through a class of cone photoreceptor containing an ultraviolet-sensitive pigment. Although these receptors were thought not to exist in the eyes of mammals, we now report that some rodents have a retinal mechanism that is maximally sensitive to ultraviolet light.     

Larval dispersal potential of the tubeworm Riftia pachyptila at deep-sea hydrothermal vents

Hydrothermal vents are ephemeral because of frequent volcanic and tectonic activities associated with crust formation. Although the larvae of hydrothermal vent fauna can rapidly colonize new vent sites separated by tens to hundreds of kilometres, the mechanisms by which these larvae disperse and recruit are not understood. Here we integrate physiological, developmental and hydrodynamic data to estimate the dispersal potential of larvae of the giant tubeworm Riftia pachyptila. At in situ temperatures and pressures (2 degrees C and 250 atm), we estimate that the metabolic lifespan for a larva of R. pachyptila averages 38 days. In the measured flow regime at a fast-spreading ridge axis (9 degrees 50' N; East Pacific Rise), this lifespan results in potential along-ridge dispersal distances that rarely exceed 100 km. This limited dispersal results not from the physiological performance of the embryos and larvae, but instead from transport limitations imposed by periodic reversals in along-ridge flows and sustained episodes of across-ridge flow. The lifespan presented for these larvae can now be used to predict dispersal under current regimes at other hydrothermal vent sites.     

Spectral sensitivity of human cone photoreceptors

The brain computes visual colour by analysing the relative excitations of three types of retinal cones. Each cone excitation is governed by a spectral sensitivity function which relates the amplitude of the neural response to wavelength at constant light intensity. The spectral sensitivities of human cones are not well characterized. We report measuring the sensitivities by recording electrical responses of human cones to stimuli of different wavelengths. Spectral sensitivities of 'green' and 'red' cones, determined over the entire visible region, show peaks near 530 and 560 nm respectively, and are remarkably similar to those of the old-world monkey Macaca fascicularis. They satisfactorily predict the photopic luminosity function, a measure of the sensitivity of cone-mediated human vision to light of different wavelengths. The kinetics of the light responses of human cones also appeared similar to those of macaque cones: the time to peak response to a dim flash was 50-100 ms and there was a characteristic undershoot during recovery.     

Imperfect optics may be the eye's defence against chromatic blur

The optics of the eye cause different wavelengths of light to be differentially focused at the retina. This phenomenon is due to longitudinal chromatic aberration, a wavelength-dependent change in refractive power. Retinal image quality may consequently vary for the different classes of cone photoreceptors, cells tuned to absorb bands of different wavelengths. For instance, it has been assumed that when the eye is focused for mid-spectral wavelengths near the peak sensitivities of long- (L) and middle- (M) wavelength-sensitive cones, short-wavelength (bluish) light is so blurred that it cannot contribute to and may even impair spatial vision. These optical effects have been proposed to explain the function of the macular pigment, which selectively absorbs short-wavelength light, and the sparsity of short-wavelength-sensitive (S) cones. However, such explanations have ignored the effect of monochromatic wave aberrations present in real eyes. Here we show that, when these effects are taken into account, short wavelengths are not as blurred as previously thought, that the potential image quality for S cones is comparable to that for L and M cones, and that macular pigment has no significant function in improving the retinal image.     

Opsin expression: new mechanism for modulating colour vision

Each cone photoreceptor in the retina responds to light in a limited range of wavelengths, giving it a spectral phenotype. This phenotype is determined by the most prevalent of the photoreceptor's visual-pigment proteins (opsins) and is assumed to remain unchanged during an animal's lifetime. Here we show that in the Pacific pink salmon, Oncorhynchus gorbuscha, single cones can switch their spectral phenotype from ultraviolet to blue by regulating the production of the appropriate opsins as the fish grow older. This photoreceptor plasticity may operate to modulate colour vision as the salmon's lifestyle changes.     

Light-avoidance-mediating photoreceptors tile the Drosophila larval body wall

Photoreceptors for visual perception, phototaxis or light avoidance are typically clustered in eyes or related structures such as the Bolwig organ of Drosophila larvae. Unexpectedly, we found that the class IV dendritic arborization neurons of Drosophila melanogaster larvae respond to ultraviolet, violet and blue light, and are major mediators of light avoidance, particularly at high intensities. These class IV dendritic arborization neurons, which are present in every body segment, have dendrites tiling the larval body wall nearly completely without redundancy. Dendritic illumination activates class IV dendritic arborization neurons. These novel photoreceptors use phototransduction machinery distinct from other photoreceptors in Drosophila and enable larvae to sense light exposure over their entire bodies and move out of danger.     

Wavelength sensitivity in blindsight

Blindsight--the residual visual functions observed in visualfield defects resulting from destruction of part of the primary visual cortex (striate cortex) even though visual stimuli presented in the field defect are not consciously perceived--has generated new insights into the nature of consciousness and the role of the extrastriate pathways in visual processing. Some patients can detect and localize unseen stimuli when they are required to guess. Discrimination of movement, flicker and orientation may also be present, but residual colour discrimination is controversial. Negative results imply that only the pathways from eye to striate cortex can transmit information about colour in primates. By measuring sensitivity to light of different wavelengths in patients with blindsight we show that spectral sensitivity in the blind fields is surprisingly high, with a reduction of only 1 log unit or less across the visible spectrum. It is also essentially normal in form, whether the patients are adapted to light or dark. The shift in peak sensitivity from medium to shorter wavelengths in adaptation to the dark (the Purkinje shift) and the presence of discontinuities in the light-adapted curve together show that blindsight involves both rod and cone contributions, and that some colour opponency remains. As colour opponency requires input from primate beta retinal ganglion cells, two-thirds of which degenerate transneurally after a striate cortical lesion in juvenile monkeys, our results show that the surviving subpopulation of primate beta cells is functional.     

零球差与负球差的非球面人工晶体植入术后视觉质量临床研究

目的对植入两种不同球差非球面人工晶体白内障患者术后矫正视力、对比敏感度、波前像差进行了对比研究,评价两组非球面人工晶体植入术后视觉质量,进而指导白内障患者选择人工晶体.方法选取行白内障超声乳化摘除术联合非球面人工晶体植入术的白内障患者40人(64只眼),植入AKreos Ao Iol(零球差非球面人工晶体)16例(30眼)列入AO组;植入Acryof IQ Iol(负球差非球面人工晶体)24例(34眼)列入IQ组.随诊3个月,对两组患者术后矫正视力、对比敏感度、波前像差应用SPSS 16.0统计学软件进行统计分析.结果两组术后3个月最佳矫正远视力无统计学意义,IQ组近视力优于AO近视力.在明视、暗视环境下和暗视合并周边眩光环境下对比敏感度,两组无差异.在波前像差检查中发现,AO组总球差(0.04±0.03)高于IQ组(0.15±0.06),垂直慧差IQ组(-0.13±0.06)高于AO组(-0.21±0.07).结论零球差非球面人工晶体保留部分角膜球差,有助于提高远视的视觉质量,而负球差非球面人工晶体保留部分垂直慧差,有助于近视的视觉质量.     

Ultraviolet vision in a bat

Most mammals, with the exception of primates, have dichromatic vision and correspondingly limited colour perception. Ultraviolet vision was discovered in mammals only a decade ago, and in the few rodents and marsupials where it has been found, ultraviolet light is detected by an independent photoreceptor. Bats orient primarily by echolocation, but they also use vision. Here we show that a phyllostomid flower bat, Glossophaga soricina, is colour-blind but sensitive to ultraviolet light down to a wavelength of 310 nm. Behavioural experiments revealed a spectral-sensitivity function with maxima at 510 nm (green) and above 365 nm (ultraviolet). A test for colour vision was negative. Chromatic adaptation had the same threshold-elevating effects on ultraviolet and visible test lights, indicating that the same photoreceptor is responsible for both response peaks (ultraviolet and green). Thus, excitation of the beta-band of the visual pigment is the most likely cause of ultraviolet sensitivity. This is a mechanism for ultraviolet vision that has not previously been demonstrated in intact mammalian visual systems.     

Human inspired lighting control in robot systems with the intention of glare avoidance

This paper presents some human-inspired strategies for lighting control in a robot system for best scene interpretation,where the main intention is to avoid possible glares or highlights occurring in images. It firstly compares the characteristics of human eyes and robot eyes. Then some evaluation criteria are addressed to assess the lighting conditions. A bio-inspired method is adopted to avoid the visual glare which is caused by either direct illumination from large light sources or indirect illumination reflected by smooth surfaces. Appropriate methods are proposed to optimize the pose and optical parameters of the light source and the vision camera.     

通风孔对压电麦克风低频响应的影响研究

根据压电麦克风的工作原理建立压电传感器的集总元件等效声电模型,分析通风孔结构对压电麦克风灵敏度的影响。通过有限元建模,研究通风孔的几何尺寸对压电麦克风低频输出的影响。通风孔位于硅基的位置不影响麦克风的低频输出。通风孔的横截面积一定时,长度越长,低频响应越快。通风孔的长度一定时,横截面积越小,低频响应越好。如果要达到相同的低频位移输出,通风孔的横截面积比为2倍时,长度比应为4倍。     

Sensory adaptation. Tunable colour vision in a mantis shrimp

Systems of colour vision are normally identical in all members of a species, but a single design may not be adequate for species living in a diverse range of light environments. Here we show that in the mantis shrimp Haptosquilla trispinosa, which occupies a range of depths in the ocean, long-wavelength colour receptors are individually tuned to the local light environment. The spectral sensitivity of specific classes of photoreceptor is adjusted by filters that vary between individuals.     

Polymorphism in red photopigment underlies variation in colour matching.

Genetic variation of human senses within the normal range probably exists but usually cannot be investigated in detail for lack of appropriate methods. The study of subtle perceptual differences in red-green colour vision is feasible since both photopigment genotypes and psychophysical phenotypes can be assessed by sophisticated techniques. Red-green colour vision in humans is mediated by two different visual pigments: red (long-wavelength sensitive) and green (middle-wavelength sensitive). The apoproteins of these highly homologous photopigments are encoded by genes on the X chromosome. Colour matches of males with normal colour vision fall into two main groups that appear to be transmitted by X-linked inheritance. This difference in colour matching is likely to reflect small variations in the absorption maxima of visual pigments, suggesting the presence of two common variants of the red and/or green visual pigments that differ in spectral positioning. We report that a common single amino-acid polymorphism (62% Ser, 38% Ala) at residue 180 of the X-linked red visual pigment explains the finding of two major groups in the distribution of colour matching among males with normal colour vision.     

Functions of the ON and OFF channels of the visual system

In the mammalian eye, the ON-centre and OFF-centre retinal ganglion cells form two major pathways projecting to central visual structures from the retina. These two pathways originate at the bipolar cell level: one class of bipolar cells becomes hyperpolarized in response to light, as do all photoreceptor cells, and the other class becomes depolarized on exposure to light, thereby inverting the receptor signal. It has recently become possible to examine the functional role of the ON-pathway in vision by selectively blocking it at the bipolar cell level using the glutamate neurotransmitter analogue 2-amino-4-phosphonobutyrate (APB)1. APB application to monkey, cat and rabbit retinas abolishes ON responses in retinal ganglion cells, the lateral geniculate nucleus and the visual cortex but has no effect on the centre-surround antagonism of OFF cells or the orientation and direction selectivities in the cortex2-5. These and related findings6-11 suggest that the ON and OFF pathways remain largely separate through the lateral geniculate nucleus and that in the cortex, contrary to some hypotheses, they are not directly involved in mechanisms giving rise to orientation and direction selectivities. We have examined the roles of the ON and OFF channels in vision in rhesus monkeys trained to do visual detection and discrimination tasks. We report here that the ON channel is reversibly blocked by injection of APB into the vitreous. Detection of light increment but not of light decrement is severely impaired, and there is a pronounced loss in contrast sensitivity. The perception of shape, colour, flicker, movement and stereo images is only mildly impaired, but longer times are required for their discrimination. Our results suggest that two reasons that the mammalian visual system has both ON and OFF channels is to yield equal sensitivity and rapid information transfer for both incremental and decremental light stimuli and to facilitate high contrast sensitivity.     

An accessory chromophore in red vision

In the absence of a red-sensitive visual pigment, some deep-sea fish use a chlorophyll derivative in their green-sensitive rod cells in order to see deep-red light. Here we show that living rods extracted from a salamander can also accumulate an exogenous chlorophyll derivative, chlorin e6, that renders them as sensitive to red light as they are to green. This vision enhancement by an unbleachable chlorophyll derivative might therefore be a general phenomenon in vertebrate photoreception.     

细形山地涡虫（PhagocataVivida）眼的超微结构研究

本文报道了细形山地涡虫（扁形动物门、涡虫纲、三肠目）眼的超微结构，该动物的眼由色素杯和感受器细胞构成。色素杯为眼的遮光装置，由一层色素细胞构成。在色素杯周围有大量的肌纤维和神经纤维。感受器细胞为双极神经元，由细胞体、轴突和高度特化的树突构成。     

Transformation and control of ultra-short pulses in dispersion-engineered photonic crystal fibres

Photonic crystal fibres (PCFs) offer greatly enhanced design freedom compared to standard optical fibres. For example, they allow precise control of the chromatic dispersion (CD) profile--the frequency dependence of propagation speed--over a broad wavelength range. This permits studies of nonlinear pulse propagation in previously inaccessible parameter regimes. Here we report on spectral broadening of 100-fs pulses in PCFs with anomalously flat CD profiles. Maps of the spectral and spatio-temporal behaviour as a function of power show that dramatic conversion (to both longer and shorter wavelengths) can occur in remarkably short lengths of fibre, depending on the magnitude and shape of the CD profile. Because the PCFs used are single-mode at all wavelengths, the light always emerges in a fundamental guided mode. Excellent agreement is obtained between the experimental results and numerical solutions of the nonlinear wave equation, indicating that the underlying processes can be reliably modelled. These results show how, through appropriate choice of CD, nonlinearities can be efficiently harnessed to generate laser light at new wavelengths.