Ultrastructure of the eyes of the grass shrimp,Palaemonetes pugio

Summary The cone cells and corneagenous cells possess extensive networks of smooth tubular endoplasmic reticulum that may be involved in optical reflectance and light-adaptational responses, respectively. The extracellular basal lamina of the basement membrane is confluent with glial cell capillary walls and may prove to be a viaduct for the transmission of hemolymph-borne substances to the retina or of retinal degradation products to the hemolymph. In addition to dense pigment granules, the distal pigment cells are shown for the first time to contain migratory reflecting platelets that are usually polymorphic in light-adapted eyes but are rectangular in dark-adapted eyes. In the latter these plates become aligned against the crystalline cones and presumably contribute to the reflection superposition optics of the grass shrimp. Dark-adapted retinular cells possess well-developed perirhabdomal cisternae, oblong or ovoid mitochondria, generally vesicular rough endoplasmic reticulum, and occasional, spherical, calcium-like intrarhabdomal inclusions. Light-adapted retinular cells possess poorly developed perirhabdomal cisternae, lamelliform rough endoplasmic reticulum, and condensed mitochondria frequently associated with lipid droplets and pigment granules. The cytoplasmic boundaries of the reflecting pigment cells expand into the extracellular spaces between individual ommatidial retinular cells during dark adaptation and recede to the interommatidial extracellular spaces during light adaptation. Cytoplasmic microfilament bundles found only at the bases of partially light-adapted rhabdomeric microvilli may be involved in microvillar shortening.     

Ultrastructure and migration of screening pigments in the retina of Pieris rapae L. (Lepidoptera,Pieridae)

Summary The retinal morphology of the butterfly, Pieris rapae L., was investigated using light and electron microscopy with special emphasis on the morphology and distribution of its screening pigments. Pigment migration in pigment and retinula cells was analysed after light-dark adaptation and after different selective chromatic adaptations. The primary pigment cells with white to yellow-green pigments symmetrically surround the cone process and the distal half of the crystalline cone, whilst the six secondary pigment cells, around each ommatidium, contain dark brown pigment granules. The nine retinula cells in one ommatidium can be categorised into four types. Receptor cells 1–4, which have microvilli in the distal half of the ommatidium only, contain numerous dark brown pigment granules. On the basis of the pigment content and morphology of their pigment granules, two distal groups of cells, cells 1, 2 and cells 3, 4 can be distinguished. The four diagonally arranged cells (5–8), with rhabdomeric structures and pigments in the proximal half of the cells, contain small red pigment granules of irregular shape. The ninth cell, which has only a small number of microvilli, lacks pigment. Chromatic adaptation experiments in which the location of retinula cell pigment granules was used as a criterium reveal two UV-receptors (cells 1 and 2), two green receptors (cells 3 and 4) and four cells (5–8) containing the red screening pigment, with a yellow-green sensitivity.     

The Ultrastructure of the Compound Eye of Two Species of Marine Ostracodes (Crustacea: Ostracoda: Cypridinidae)

Ultrastructurally, the compound eyes of the luminescent marine ostracodes Vargula graminkola and V. tsujii are similar. These ostracodes have two lateral compound eyes, with relatively few ommatidia (13 and 20 respectively). They exhibit apposition type compound eyes as seen in many other arthropods. Each ommatidium includes: a flat, ectodermal cuticular covering, corneagen cells, two long cone cells that give rise to a large conspicuous crystalline cone, retinular cells, pigment cells, a microvillar rhabdom and proximal axonal neurons. The axons merge to form an optic nerve that extends into the brain through a short, muscular stalk that is surrounded externally by a cuticle. The number of retinular cells is typically six per ommatidium in V. graminicola and eight per ommatidium in V. tsujii. Screening pigment cells surround each ommatidium forming a layer that is about 5–15 pigment granules thick. In addition to pigment cells, the cytoplasm of the retinular cells includes numerous screening pigment granules. In light/dark adaptation, there are no obvious morphological differences in the orientation of the rhabdom or in the organization of the screening pigments. Both Vargula species studied are nocturnally active and bioluminescent suggesting that these eyes are capable receptors of the bright conspecific luminescence.     

The physical and morphological properties of the pigment screen in the compound eye of a shrimp (Crustacea)

Summary The pigment cells of the compound eye of the shrimps (Crangon crangon andC. allmani) were studied by electron microscopy (SEM and TEM) and microspectrophotometry. The compound eyes of these species contain light-absorbing and -reflecting pigments contained in granules, located in 5 different cells. The light absorbing pigment granules (light screen) are situated in (1) the distal pigment cells, (2) the retinular cells, (3) the basal pigment cells. The reflecting pigment granules are located in (4) the distal, and (5) the proximal reflecting pigment cells. Another innominate cell type investing the ommatidia contains vacuoles without pigment content. The innominate cell type, and the basal absorbing pigment cell (3) listed above, have not earlier been reported for a crustacean species. Measurements of the spectral absorption on sliced and squashed ommatidia show that all components of the light screen have an increased absorption in the wavelength regions 400–450 nm and 530–570 nm, probably due to xanthommatin and ommin. The spectral absorbancy of the reflecting pigment cells were not determined. Similar cells in other species are known to contain pteridines.We thank Prof. Dr. Langer, Bochum, Germany, for his kind help. The work was supported by funds from the Karolinska Institutet to Doc. G. Struwe, and grant NFR No. 2760-007 to Doc. R. Elofsson.     

Cytoskeleton of retinular cells from the stomatopod,Gonodactylus oerstedii: possible roles in pigment granule migration

Retinular cells of the compound eyes of stomatopods (mantis shrimps) contain screening pigment granules that migrate radially in response to light. To clarify the role of the cytoskeleton in these movements, we have performed light microscopy and ultrastructural analyses of cytoskeletal organelles in retinular cells. Rhodamine phalloidin staining indicates that filamentous actin is a component of microvillar rhabdomeres and zonula adherens between retinular cells. Ultrastructural studies reveal three populations of microtubules in retinular cells that differ in their orientations and labilities to fixation. Two of these populations are oriented longitudinally in cells: the soma microtubules, found primarily in a column in the cell soma, and the more labile palisade microtubules, which extend alongside the palisade vacuole near the rhabdomere. The third, most labile microtubule population, and filaments 9–30 nm in diameter, are oriented radially in retinular cells, some within cytoplasmic bridges that span the palisade. The radial microtubules and filaments are appropriately oriented for participating in pigment granule migration. Determination of microtubule polarities in retinular cells by decoration with endogenous tubulin indicates that palisade and soma microtubules contain subpopulations having opposite polarity orientations, as has been observed in neuronal dendrites. In contrast, neighboring pigment cells contain microtubules uniformly oriented with minus ends towards the nucleus, as has been observed in most cell types studied.     

棉铃虫幼虫小网膜细胞对光暗的反应

用透射电镜观察了棉铃虫Heliothis armigers(Hübnner)5龄幼虫小网膜细胞内一些细胞器的昼夜变化.其中色素颗粒,内质网,多泡体和多片层体变化特别显著.天亮3小时后,细胞内出现大量多泡体,多片层体和形态介于两者之间的细胞器.它们的数量随光照时间的延长而下降.天亮10小时后,大部分在细胞内消失.从天黑后2小时至天亮前2小时的细胞内含有大量的由滑而内质网构成的髓样体.天亮后它们在细胞内消失.昼夜交替还导致细胞内屏蔽色素颗粒周期性的水平和垂直移动.结合现有资料,我们对上述现象的意义进行了探讨.     

Adaptive Mechanisms in the compound eye of Squilla mantis (Crustacea,Stomatopoda)

Summary Light and dark adaptations were studied in the eye of Squilla mantis. Light adaptation is characterized by (1) a proximal shift of the distal pigment sheath (DPS) surrounding the proximal portion of the crystalline cone above its zone of contact with the rhabdom; (2) flattening of the distal pigment sheath; (3) lengthening of the crystalline cone correlated with shortening of the rhabdom; (4) a migration of screening pigment granules in retinula cells in the protoplasmic bridges crossing the perirhabdomal space. In animals kept in constant darkness, longitudinal displacements of the distal pigment sheath were found to be subject to a circadian rhythm characterized by a maximal light adaptation state at about 5 p.m. and a minimal one at 5 a.m. Screening pigment granule translocation in retinula cells does not show such rhythmic activity.Abbreviations a, b maximal incidence angles in L.A., and D.A., respectively - Cc crystalline cone - Dps distal pigment sheath - I extreme incident light beam - Prs perirhabdomal space - Rh rhabdom - Rp reflecting pigment This research has been supported by grant 3.012-76 of the Swiss National Science Foundation     

钙离子浓度对暗适应时的中华绒螯蟹光感受器超微结构的影响

用透射电镜研究了暗适应时中华绒螯蟹的光感受器超微结构与外界钙离子浓度的关系,结果显示出与培育在生理溶液中的光感受器相比,细胞外钙离子浓度升高,使得感杆束的直径急剧缩小,感杆束周围胞质增厚,胞饮泡增加,膜下猪泡囊极度减小。胞质中多囊体的数量和直径减小,而板模体和溶酶体的数量增加,同时细胞内的色素颗粒增多。分布在小网膜细胞的远端。细胞的结构表现为类似光适应状态,与之相反,细胞外钙离子浓度降低时小眼的感     

The fine structure of the lateral ocellus of the dobsonfly larva

The lateral ocelli of the dobsonfly (Protohermes grandis, Neuroptera) larva have been examined with light and electron microscopy. The larva has six ocelli on both sides of the head, each containing a single corneal lens. A conical crystalline body, of some 10–20 cells is situated immediately posterior to the lens. From 100 to 300 elongated retinular cells are arranged perpendicular to the crystalline body except at the innermost surface of the lens, where they are absent. The distal process of each retinular cell is enclosed by a tube-like rhabdom formed by the close association of microvilli from the same and adjacent distal processes. The distal process contains many mitochondria, multivesicular bodies, microtubles and pigment granules. In the dark-adapted ocellus the pigment granules are concentrated near the nucleus which lies under the rhabdomic layer. The granules diffuse toward the rhabdomic microvilli during light adaptation. Each retinular cell has a single axon, which extends from the ocellus as an ocellar nerve fiber into the optic lobe, where it frequently synapses upon second order neurons. In addition to these afferent synapses, there are two other synaptic combinations: (1) a feedback synapse from a second order neuron to a retinular axon, and (2) a synapse between second order neurons. These results suggest that photic signals reach the more proximal part of the brain via second order neurons after some degree of integration in the optic lobe.     

Insect pupil mechanisms

Summary The hypothesis that the glow observable in dark adapted butterfly eyes is extinguished upon light adaptation by the action of migrating retinula cell pigment granules (Stavenga, 1975a) has been investigated. Experimental procedures applying optical methods to intact, living animals were similar to those used previously to investigate the migration of retinula cell pigment granules in Hymenoptera (Stavenga and Kuiper, 1977). The data obtained from nymphalid butterflies and Hymenoptera show close parallels, favouring the pigment migration hypothesis.The retinula cell pigment granules control the light flux in the butterfly rhabdom and hence are part of a pupil mechanism. The range of action of this pupil mechanism is about 3 log units of light intensity. The speed of pupil closure is slowed down with longer dark adaptation times. The way in which pupil processes can be distinguished from photochemical processes of the visual pigment is discussed.     

龟纹瓢虫成虫的复眼形态及其显微结构

利用光镜、组织切片法观察了龟纹瓢虫Propylaea japonica(Thunberg)成虫的复眼形态及其显微结构。结果如下:(1)头正前方观,复眼外形似半球,且后方稍向内合拢。每个复眼约包括630个小眼。(2)每个小眼是由1套屈光器(1个角膜和1个晶锥)、6至8个小网膜细胞及其特化产生的视杆和基细胞等几部分组成。晶体周围及小网膜色素细胞内均含有丰富的色素颗粒。(3)小眼整体纵切显示,其上、下段色素颗粒分布相对较多,中段分布较少。(4)明、暗适应状态对小眼的色素颗粒分布有影响,性别对其分布无明显影响。明适应状态下,其色素颗粒较均匀地分布于视杆两侧上下,暗适应状态时色素颗粒则主要分布在视杆部位的上侧,显示其具有一定的重叠眼性质;而在相同的明、暗适应状态下其雌、雄成虫复眼的色素颗粒分布间无明显差异。     

灰茶尺蠖成虫复眼的超微结构及其明暗适应中的变化

【目的】明确灰茶尺蠖Ectropis grisescens成虫复眼的超微结构及其明暗适应中的变化,探究其调光机制。【方法】采用超景深显微镜测定了灰茶尺蠖成虫复眼的小眼数量、间角、直径和曲率半径等外部参数,并通过组织切片、光学显微镜和透射电子显微镜等技术观察了复眼的内部超微结构;通过光学显微镜观察了灰茶尺蠖成虫复眼在明暗环境中分别适应2 h后晶锥结构及色素颗粒的位置变化。【结果】灰茶尺蠖成虫复眼呈半球形,雌、雄虫单个复眼分别有2 502±105和3 123±78个小眼。小眼自远端至近端由角膜、晶锥、透明区构成的屈光层和由15个视网膜细胞构成的感光层组成。2个初级色素细胞包裹着晶锥,自角膜近端延伸至视网膜细胞核区的远端;每个小眼外围由6个次级色素细胞围绕,自角膜近端延伸至基膜;在透明区内14个视网膜细胞聚集成束(非感杆束),远端与晶锥束末端连接,在感光层内形成闭合型感杆束,延伸至第15个视网膜细胞(基部视网膜细胞)。在明暗适应时,灰茶尺蠖复眼的晶锥细胞间出现开闭,色素颗粒进行纵向位移,以适应外界的光强度的变化。【结论】灰茶尺蠖成虫复眼属于重叠像眼,感杆束为“14+1”模式;屏蔽色素颗粒的移...     

Adult stemmata of the butterfly Vanessa cardui express UV and green opsin mRNAs

Adult stemmata are distinctive insect photoreceptors located on the posterior surfaces of the optic lobes. They originate as larval eyes that migrate inward during metamorphosis. We used a combination of light microscopy and in situ hybridization to examine their anatomical organization in the butterfly Vanessa cardui and to test for the presence of visual pigments, the light sensitive components of the visual transduction pathway. The bilateral cluster of six internal stemmata is located near the ventral edge of the lamina. They retain the dark screening pigment and overlying crystalline cones of the larval stemmata. We found two opsin mRNAs expressed in the stemmata that are also expressed, respectively, in UV-sensitive and green-sensitive photoreceptor cells in the compound eye. A third mRNA that is expressed in blue-sensitive photoreceptor cells of the compound eye was not expressed in the stemmata. Our results reinforce the idea that the adult stemmata are not merely developmental remnants of larval eyes, but remain functional, possibly as components of the circadian input channel.This work was supported by grants from the National Science Foundation to A.D.B. (IBN-0346765) and R.H.W (IBN-9874493).     

Ultrastructural study of the naupliar eye of the ostracodeVargula graminicola (Crustacea,Ostracoda)

Summary Ostracodes, like other crustaceans, have a simple naupliar eye that is built upon a theme of three eye cups surrounded by a layer of screening pigments. The single naupliar eye of the ostracodeVargula graminicola is situated medially on the dorsal-anterior side of the body and has three fused eye cups, two dorso-lateral and one ventral. Each eye cup has the following components: (1) pigment cells between the eye cups, (2) tapetal cells, (3) retinular cells with (4) microvillar rhabdomeres, and (5) axons extending into the protocerebrum. Typically two retinular cells contribute lateral microvilli to each rhabdom. The two dorso-lateral eye cups have about 40 retinular cells (20 rhabdoms) and the ventral eye cup has about 30 retinular cells (15 rhabdoms). Typical of myodocopid naupliar eyes (as reported from light microscopic studies), no lens cells or cuticular lenses were observed. The presence of tapetal cells identifies theVargula eye as a maxillopod-ostracode type crustacean naupliar eye. It is unlikely that the naupliar eye ofV. graminicola functions in image formation, rather it probably functions in the mediation of simple taxis towards and away from light.     

The Spectral Sensitivities of Single Receptor Cells in the Lateral, Median, and Ventral Eyes of Normal and White-Eyed Limulus

Spectral sensitivity curves can be distorted by screening pigments. We have determined whether this is true for Limulus polyphemus by determining, from receptor potentials recorded using intracellular microelectrodes, spectral sensitivity curves for normal animals and for white-eyed animals (which lack screening pigment). Our results show: (a) In median ocelli, the curve for UV-sensitive receptor cells peaks at 360 nm and does not depend on the presence of screening pigment, (b) The curve for ventral eye photoreceptors is identical to that for retinular cells from the lateral eyes of white-eyed animals and peaks at 520–525 nm. (c) In normal lateral eyes, when the stimulating light passes through screening pigment, the curve indicates relatively more sensitivity in the red region of the spectrum than does the curve for white-eyed animals. Therefore, the screening pigment is probably red-transmitting, (d) In median ocelli, the curve for visible-sensitive cells peaks at 525 nm and is approximately the same whether the ocelli are from normal or white-eyed animals. However, the curve is significantly broader than that for ventral eyes and for lateral eyes from white-eyed animals.     

夜蛾复眼转化速度与光暗适应的时间关系

夜行蛾类的复眼,随光、暗适应时间而逐步转化,这种转化是可逆的.以屏蔽色素分布范围的大小为指标来判断复眼的转化速度得以下结果:1.从亮眼到暗眼:亮眼进入暗适应后其屏蔽色素随暗适应时间的增加而逐步向远心端方向集中.屏蔽色素的移动是减速进行的.暗适应开始后的前3分钟,每分钟移动百分率为10.7,当暗到10—15分钟时每分钟移动百分率为4.6,再暗到60—150分钟时每分钟移动百分率为0.7.屏蔽色素移动的速度个体间差异较大,完成全过程大多数个体需150分钟,少数个体只需60分钟,另有个别个体经过270分钟暗适应仍尚未完成全过程.2.从暗眼到亮眼:暗眼受光后,其屏蔽色素随光适应时间的增加而向近心端方向扩散,色素移动速度随时间的增加而减缓.转化全过程约需60分钟.     

The effect of light-dark adaptation on the ultrastructure ofLimulus lateral eye retinular cells

Summary The fine structure of retinular cells within lateral eyes ofLimulus polyphemus which had been dark or light adapted for 12 h in vivo was studied via electron microscopy. The ommatidium to ommatidium and retinular cell to retinular cell variability observed in light microscope studies was confirmed. The rhabdomeric microvilli were longer and narrower, the area of contiguous microvillar membranes greater, the endoplasmic reticulum less abundant and the mitochondrial granules (? calcium containing) more numerous in well dark adapted than in well light adapted retinular cells (Figs. 1, 3, 4, 7, 8) and membrane whorls or vacuoles were present in the peripheral cytoplasm of very well light adapted retinular cells (Fig. 6). Phagocytotic vesicles, multivesicular bodies and lysosomes were present in the interrhabdomeral cytoplasm of partially light adapted retinular cells (Figs. 1, 2, 3, 10). The number of retinular cell microvilli in contact with the eccentric cell dendrite was smaller in very well light adapted than in well dark adapted ommatidia (Fig. 9). The possible functional significance of these light-dependent structural changes is discussed.This investigation was supported in part by Grant 2 RO1 EY 00236 National Eye Institute, National Institutes of HealthMember of the SFB 160 of the Deutsche Forschungsgemeinschaft     

光和暗对埃及蟾蜍(BUFO REGULARIS)发育中的视网膜的影响(英文)

本文研究了埃及蟾蜍(Bufo regularis Reuss)从早期幼虫到变态结束,光和暗对视网膜的影响。所观察到的对光和暗反应的变化限于色素上皮和光感受细胞。实验动物分四组:1)在亮处固定的对照(CL);2)在暗处固定的对照(CD);3)连续养在暗处的动物(DD);4)连续受光照的动物(LL)。在CD和DD组动物,黑色素颗粒在色素上皮细胞突起(PEP)中的分布限于光感受细胞顶部间之外周区(巩膜方位)。与此相反。在CL和LL组动物,大量黑色素颗粒则分散在视觉细胞外节段和椭球段间色素上皮细胞突起之向心端位置(玻璃体方位)。在这种动物,上皮细胞色素对光和暗反应发生的光机械运动出现在肢芽期以前。新变态小蟾蜍DD组眼球,与其他三组比较起来,色素上皮层相当厚并含有大的脂肪滴。在较晚期,只有DD组动物的一些杆细胞外节段呈现退化现象。其次,这一组中,由于连续缺少光照的结果,眼球之锥细胞数目有明显减少。四组动物的视网膜上也观察到锥细胞的细胞核位置略有不同。     

Colour in the eyes of insects

Many insect species have darkly coloured eyes, but distinct colours or patterns are frequently featured. A number of exemplary cases of flies and butterflies are discussed to illustrate our present knowledge of the physical basis of eye colours, their functional background, and the implications for insect colour vision. The screening pigments in the pigment cells commonly determine the eye colour. The red screening pigments of fly eyes and the dorsal eye regions of dragonflies allow stray light to photochemically restore photoconverted visual pigments. A similar role is played by yellow pigment granules inside the photoreceptor cells which function as a light-controlling pupil. Most insect eyes contain black screening pigments which prevent stray light to produce background noise in the photoreceptors. The eyes of tabanid flies are marked by strong metallic colours, due to multilayers in the corneal facet lenses. The corneal multilayers in the gold-green eyes of the deer fly Chrysops relictus reduce the lens transmission in the orange-green, thus narrowing the sensitivity spectrum of photoreceptors having a green absorbing rhodopsin. The tapetum in the eyes of butterflies probably enhances the spectral sensitivity of proximal long-wavelength photoreceptors. Pigment granules lining the rhabdom fine-tune the sensitivity spectra.     

The ultrastructure of the compound eye of Munida rugosa (Crustacea: Anomura) and pigment migration during light and dark adaptation

The galatheid squat lobster, Munida rugosa, has compound eyes of the reflecting superposition type in which a distal cone cell layer and a proximal rhabdom layer are separated by an extensive clear zone. The eye is shown to have certain unique features. In all other reflecting superposition eyes, the clear zone is traversed by crystalline tracts formed by the cone cells. In M. rugosa a thin distal rhabdom thread, formed by the eighth retinula cell, connects the cones to the proximal fusiform rhabdoms. The cytoplasm of the other retinula cells also crosses the clear zone in a complex pattern. Fully light-adapted ommatidia are optically isolated by limited migrations of distal shielding pigments. A reflecting pigment multilayer lines each cone to facilitate the formation of a superposition image. This also shows a light-induced change which may limit the acceptance angle of the eye during light adaptation.