Neither apposition nor superposition: the compound eyes of the Chestnut Leafminer Cameraria ohridella

The two lemon-shaped compound eyes of the moth Cameraria ohridella measure in dorsal–ventral direction 263.0 μm in male and 238.9 μm in female individuals. In anterior–posterior direction no significant differences were found between the sexes, eye length being about 194.6 μm. The eyes of males consist of ca. 417 hexagonal facets, while those of females contain 367. In both sexes facet diameters are approximately 11.5 μm. Despite the size differences of the eyes in the two sexes, ultrastructurally they are identical and both possess ommatidia of 80 μm mean length. The ultrastructure of the eye is described and compared with that of other compound eyes of Lepidoptera. Anatomically the eyes represent a type intermediate between apposition and refractive superposition kind. A distal rhabdom is present in the space that in the eyes of larger moths with superposition optics is occupied by the so-called clear zone. A tracheal tapetum and longitudinal screening pigment migrations, typical of superposition but not apposition eyes are present despite the lack of a clear zone. Thus, our results support an earlier calculated minimal theoretical limit for superposition eyes.     

Geometrical optics of a galatheid compound eye

The eyes of galatheid squat lobsters (Munida rugosa) are shown to be of the reflecting superposition type. In the dark-adapted state corneal lenses focus light at the level of the rhabdoms and light from more than 1000 facets is redirected to the superposition focus by the reflecting surfaces of the crystalline cones. When the eye is light adapted, apposition optics are used. In this state paraxial light is focused by the corneal lens and the parabolic proximal end of the cone onto the distal end of a rhabdomeric lightguide. The latter transmits light across the clear zone to the rhabdom layer. In the dorsal part of the eye the individual ommatidia become progressively shorter until the cones and rhabdoms are no longer separated by a clear zone. Although formerly considered to be developing ommatidia, they are shown to be retained specifically for scanning the downwelling irradiance.Abbreviations RI refractive index - SEM scanning electron microscope     

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.     

Diurnal and circadian rhythm in compound eye of cricket (Gryllus bimaculatus): changes in structure and photon capture efficiency

Day-night changes in rhabdom size of compound eyes were investigated in three groups of crickets (Gryllus bimaculatus): nymphs and adult males and females. In both adults and nymphs, the rhabdoms were larger at night than during a day. In adults, the mean rhabdom occupation ratios (RORs) of ommatidial retinulae at midnight were about two times greater than the values at midday. This change contributes to control of the photon capture efficiency (PCE) of the eye according to photic environment. The RORs of adult males at midnight were higher than those of both adult females and nymphs. This suggests that the PCE of the compound eye of adult males is the greatest of all groups. Under constant darkness, day-night changes in ROR were detected only in adult males, but neither in adult females nor in nymphs. On the other hand, no day-night changes were detected in any experimental group under constant light. These results suggest that the change in rhabdom size between day and night is an adaptation to the photic environment that is controlled mainly by the light-dark (day-night) cycle. However, the change in male adults is induced by an endogenous circadian clock.     

黑翅土白蚁有翅成虫复眼的形态结构

采用组织切片法光镜下观察黑翅土白蚁Odontotermes formosanus(Shiraki)有翅成虫的复眼形态结构及光、暗适应条件下色素颗粒移动的规律。结果如下:(1)头正前方观,复眼外部形态略呈圆形。(2)有翅成虫复眼类型属于并列像眼,每只复眼约由360个小眼组成。(3)每个小眼是由1套屈光器(1个角膜和1个晶锥)、小网膜色素细胞、视杆和基细胞等几部分组成。小网膜色素细胞内均含有丰富的色素颗粒。(4)在光适应条件状态下,屈光器及视杆周围的色素颗粒主要分布在视杆部位的上侧,暗度适应条件状态时则较均匀地分布于视杆两侧上下;性别对色素颗粒分布无明显影响。     

亲土苔蛾成虫复眼超微结构

【目的】重叠型眼在昆虫复眼演化中起着重要作用。本研究旨在阐明夜出型亲土苔蛾Manulea affineola复眼类型及结构特征,以期填补灯蛾亚科昆虫复眼研究的空白,扩充夜出型昆虫复眼的特征数据,为探讨重叠型眼的变异趋势及复眼演化提供依据。【方法】运用光学和透射电子显微技术观察亲土苔蛾成虫复眼的超微结构。【结果】亲土苔蛾成虫复眼具有一个透明区,由6个次级色素细胞的透明胞质构成。小眼具8个视网膜细胞,其中1个视网膜细胞较短,仅位于小眼基部。在透明区内,7个视网膜细胞聚集成一束,其远端与晶体束末端相接,但并不形成视杆。在透明区下方,这7个视网膜细胞形成一个中心融合的视杆。在复眼背缘区的小眼的视杆具有近似矩形的横截面,而其余小眼的视杆具多分支状截面。【结论】亲土苔蛾成虫复眼属于重叠型眼;复眼背缘区的矩形视杆很可能与昆虫的偏振敏感性有关。     

Sexual Dimorphism in the Compound Eye of Rhagophthalmus ohbai (Coleoptera: Rhagophthalmidae): I. Morphology and Ultrastructure

The eyes of the winged males and larvi-form, wingless females of the firefly Rhagophthalmus ohbai differ from each other in several respects. Compared with the eyes of the males, those of the females contain fewer (35 versus ca. 3500) and smaller (20 μm versus 24-31 μm) facets and anatomically they are of the apposition type. Their main function appears to be to detect light intensity changes from day to nighttime; resolving power of the female eye must be poor and e-vector discrimination would be absent. The eyes of the males consist of a smaller, dorsal region of ca. 500 om-matidia of about 250 μm length and a larger, ventral region of ca. 2000 ommatidia of about 640 urn length. The microvilli of the dorsal eye region are somewhat wider than those of the ventral region (55 nm versus 45 nm) and are less regularly arranged. A tapetal reflecting layer is only present in the dorsal eye region. The small clear-zone between dioptric apparatus and retina in the dorsal eye region would not allow as good a superposition image to be produced as in the ventral eye region with its 5 times wider clear-zone. The regular orientations of the microvilli in the rhabdoms and the lack of a proper tapetum in the ventral eye region suggest that e-vector discrimination should be possible.     

An apposition‐like compound eye with a layered rhabdom in the small diving beetle Agabus japonicus (Coleoptera,Dytiscidae)

The fine structure of the compound eyes of the adult diving beetle Agabus japonicus is described with light, scanning, and transmission electron microscopy. The eye of A. japonicus is mango‐shaped and consists of about 985 ommatidia. Each ommatidium is composed of a corneal facet lens, an eucone type of crystalline cone, a fused layered rhabdom with a basal rhabdomere, seven retinula cells (including six distal cells and one basal cell), two primary pigment cells and an undetermined number of secondary pigment cells that are restricted to the distalmost region of the eye. A clear‐zone, separating dioptric apparatus from photoreceptive structures, is not developed and the eye thus resembles an apposition eye. The cross‐sectional areas of the rhabdoms are relatively large indicative of enhanced light‐sensitivity. The distal and central region of the rhabdom is layered with interdigitating microvilli suggesting polarization sensitivity. According to the features mentioned above, we suggest that 1) the eye, seemingly of the apposition type, occurs in a taxon for which the clear‐zone (superposition) eye is characteristic; 2) the eye possesses adaptations to function in a dim‐light environment; 3) the eye may be sensitive to underwater polarized light or linearly water‐reflected polarized light. J. Morphol. 275:1273–1283, 2014. © 2014 Wiley Periodicals, Inc.     

Localization of the pupil trigger in insect superposition eyes

Summary In the superposition eyes of the sphingid moth Deilephila and the neuropteran Ascalaphus, adjustment to different intensities is subserved by longitudinal migrations of screening pigment in specialized pigment cells. Using ophthalmoscopic techniques we have localized the light-sensitive trigger that controls pigment position.In both species, local illumination of a small spot anywhere within the eye glow of a dark-adapted eye evokes local light adaptation in the ommatidia whose facets receive the light. Details of the response pattern demonstrate that a distal light-sensitive trigger is located axially in the ommatidium, just beneath the crystalline cone, and extends with less sensitivity deep into the clear zone. The distal trigger in Deilephila was shown to be predominantly UV sensitive, and a UV-absorbing structure, presumably the distal trigger, was observed near the proximal tip of the crystalline cone.In Ascalaphus we also found another trigger located more proximally, which causes local pigment reaction in the ommatidia whose rhabdoms are illuminated (the centre of the eye glow). The light-sensitive trigger for this response appears to be the rhabdom itself.     

Interspecific variations in the morphology and ultrastructure of the rhabdoms of oplophorid shrimps

Interspecific variations in rhabdom structure between various oplophorid shrimps are described and the differences are related to the light environment at different depths within the mesopelagic zone. The ultrastructure of the distal rhabdom in these species is described for the first time. Quantitative measurements show that the proportion of the rhabdom layer occupied by the distal rhabdom varies from 3.5-25% in the dorsoventral plane of the eye of Systellaspis debilis. The distal rhabdom occupies less than 1% of the rhabdoms in the eye of Acanthephyra pelagica, where it can only be seen by using the electron microscope. It is suggested that the rhabdoms of those species that remain within the photic zone (such as S. debilis) are adapted to maximize contrast, whereas in those whose depth ranges extend into the aphotic zone (such as A. pelagica) they are adapted for maximum sensitivity.     

Fine structural description of the compound eye of the Madagascar 'hissing cockroach'Gromphadorhina portentosa (Dictyoptera: Blaberidae)

The compound eyes of the wingless adults of the Madagascar ‘hissing cockroach’Gromphadorhina portentosa Sachum, 1853 were examined by light and electron microscopy. Each eye contains 2 400‐2 500 mostly hexagonal facets. However, irregularities affecting both shape and size of the ommatidia are relatively common, especially towards the margins of the eye. An individual ommatidium of this eucone type of apposition eye contains eight retinula cells, which give rise to a centrally‐fused, tiered rhabdom. The distal end of the latter is funnel‐shaped and accommodates the proximal end of the cone in its midst. Further below, the rhabdom (then formed by the rhabdomeres of four retinula cells) assumes a squarish profile with microvilli aligned in two directions at right‐angle to each other. Cross sections through the proximal regions of the rhabdom display triangular rhabdom outlines and microvilli (belonging to 3‐4 retinula cells different from those involved in the squarish more distal rhabdom) that run in three directions inclined to one another by 120°. Overall the organization of the eye conforms to the orthopteroid pattern and particularly closely resembles that of the American cockroach Periplaneta americana. However, since G. portentosa possesses fewer ommatidia, this could be a consequence of its inability to fly. On the other hand, the large size of the facets and the voluminous rhabdoms suggest considerable absolute sensitivity and an ability to detect the plane of linearly polarized light. Based on the pattern of microvillus orientations in combination with the crepuscular lifestyle G. portentosa leads and the habitat it occurs in, the prediction is made that this insect uses its green receptors for e‐vector discrimination in the environment of down‐welling light that reaches the forest floor.     

Degeneration of the compound eye of the termite Neotermes jouteli (Isoptera) in darkness during the phase of reproduction

Summary Long-term light deprivation of the royal pair of Neotermes jouteli during the phase of reproduction leads to a dramatic change in the organization within the compound eye. In a swarming alate, investigated with scanning and transmission electron microscopy, the eye consists of about 200 ommatidia. No differences between male and female eyes are observed. Each ommatidium is composed of a biconvex cornea, a cone of the eucone type, and a rhabdom which is located directly beneath the Semper cells. The rhabdom consists of eight rhabdomeres which are fused along the ommatidial axis. In the central part of the compound eye the rhabdom measures roughly 20 m in length. Concealed life of the imagines causes a dismantling of the cone and the rhabdom until complete destruction. This is accompanied by an increase in the number of pigment granules and a decrease in the number of mitochondria.     

Visual behaviour and the structure of dark and light-adapted larval and adult eyes of the New Zealand glowworm Arachnocampa luminosa (Mycetophilidae: Diptera)

Both larval and adult New Zealand cave glowworms exhibit reactions to light; their photoreceptors must, therefore, be regarded as functional. The two principal stemmata of the larva possess large biconvex lenses and voluminous rhabdoms. Approximately 12 retinula cells are present. In light-adapted larvae the diameter of the rhabdom is 8 μm and that of an individual microvillus is 49.5 nm. Dark-adapted eyes have rhabdoms that measure 14 μm in cross section and microvilli with an average diameter of 54 nm. The compound eye of the adult comprises approximately 750 ommatidia, each with a facet diameter of 27–28 μm. A facet is surrounded by 1–6 interommatidial hairs which are up to 30 μm long. The interommatidial angle is 5.5°. Cones, consisting of 4 crystalline cone cells, are of the ‘acone’ type. Pigment granules in the primary pigment cells are twice as large as those of the retinula cells which measure 0.6–0.75 μm in diameter. The rhabdom is basically of the dipteran type, i.e. six open peripheral rhabdomeres surround 2 central rhabdomers arranged in a tandem position. The microvilli of cells 1–6 and cell 8 have diameters ranging from 68 to 73 nm, but those of the distally-located central rhabdomere 7 are 20% larger. This is irrespective of whether the eye is dark or light-adapted. In the latter the cones are long and narrow, the screening pigment granules closely surround the rhabdomeres, and the rhabdom is less voluminous than that of the dark-adapted eye.     

Circadian Structural Changes in the Retina of Lycosa tarentula (Araneae: Lycosidae)

Daily structural changes of the rhabdoms are described in the four eye types of a lycosid spider submitted to laboratory conditions: LD 12:12 (light on at 08.00, 100 lux). From a study of animals submitted to constant darkness during fourteen days, rhabdom turnover was shown to be circadian. Each type of retina exhibits its own rhythmic turnover of rhabdoms. Anterior-lateral, posterior-median and lateral eyes are mostly diurnal; anterior-median retinae comprise 300 receptors with mainly nocturnal functioning and 150 receptors with mainly diurnal functioning. A correlation was found between rhythms of locomotor activity, other activity, and rhabdom turnover in L. tarentula suggesting that the same pacemaker controls these different rhythms.     

The optics of tsetse fly eyes in relation to their behaviour and ecology

Abstract The visual acuity of two species of tsetse flies, Glossina morsitans morsitans Westw. and Glossina pallidipes Aust., was investigated. Male G. morsitans eyes have an acute zone in the forward region, with large hexagonal lenses (mean minimum diameter, D=33, SE±0.7 μm), relatively small interommatidial angle (Δ(φ=1.08^o) and angular receptive field of individual ommatidia (Δp) of not less than 1.14^o. A narrow band of square lenses, with intermediate diameter and Δφ, merges with smaller hexagonal lenses in the periphery (24±0.7 μm), with relatively large interommatidial angle (Δφ=3.7^o) and small angular receptive field (Δp = c. 1.6^o). G.pallidipes eyes are similar, except that the lenses in the acute zone are larger than those of G.morsitans , in proportion to their larger body size. Female eyes are not significantly different from male eyes, except that they have a narrower region of binocular overlap (maximum for males = 24^o, for females = 18^o). The eye parameter (p=DΔφ) in the acute zone of male G.morsitans = 0.62, and in the peripheral zone = 1.56. These relatively high values are consistent with fast flight, visual detection of drift due to low wind speeds, mating chases and discrimination of cryptic host animals at high light intensities. The extended region of binocular overlap in males may serve as an early warning system of the approach of potential females. From our estimates, tsetse flies ought to be able to detect small objects against the sky c. 30 min before sunrise and after sunset, and to use their peripheral vision perhaps 15 min earlier and later than this.     

Circadian Structural Changes in the Retina of Lycosa tarentula (Araneae: Lycosidae)

Daily structural changes of the rhabdoms are described in the four eye types of a lycosid spider submitted to laboratory conditions: LD 12:12 (light on at 08.00, 100 lux). From a study of animals submitted to constant darkness during fourteen days, rhabdom turnover was shown to be circadian. Each type of retina exhibits its own rhythmic turnover of rhabdoms. Anterior-lateral, posterior-median and lateral eyes are mostly diurnal; anterior-median retinae comprise 300 receptors with mainly nocturnal functioning and 150 receptors with mainly diurnal functioning. A correlation was found between rhythms of locomotor activity, other activity, and rhabdom turnover in L. tarentula suggesting that the same pacemaker controls these different rhythms.     

A fibre-optic scalar irradiance microsensor: application for spectral light measurements in sediments

Abstract The manufacturing of a new spherical fibre-optic microsensor is described. The microsensor measures scalar irradiance, i.e. the spherically integrated light at a point in space. The light collector of the probe was a 70-μm diffusing sphere cast on the tip of a 125-μm wide optical fibre tapered down to 15–20 μm diametre. The microsensor had an isotropic (±10%) response from −160° to +160° over the whole spectral range from 400–900 nm in air as well as in water. The microsensor was coupled to a sensitive spectroradiometre and the spectral distribution of scalar irradiance in sediments was measured at 100 μm spatial resolution. Light was available for photosynthesis near the sediment surface at a higher intensity and a different spectral composition than could be expected from the illumination. By the combination of oxygen microelectrodes and the present fibre-optic microsensor it is now possible to study the depth distribution of microbenthic photosynthesis in relation to the available photosynthetically active radiation at ≤ 100 μ m resolution.     

Visual field structure in the Empress Leilia, Asterocampa leilia (Lepidoptera, Nymphalidae): dimensions and regional variation in acuity

Male Empress Leilia butterflies ( Asterocampa leilia) use a sit-and-wait tactic to locate mates. To see how vision might influence male behavior, we studied the morphology, optics, and receptor physiology of their eyes and found the following. (1) Each eye's visual field is approximately hemispherical with at most a 10 degrees overlap in the fields of the eyes. There are no large sexual differences in visual field dimensions. (2) In both sexes, rhabdoms in the frontal and dorsal ommatidia are longer than those in other eye regions. (3) Interommatidial angles are smallest frontally and around the equator of the eye. Minimum interommatidial angles are 0.9-1 degrees in males and 1.3-1.4 degrees in females. (4) Acceptance angles of ommatidia closely match interommatidial angles in the frontal region of the eye. We conclude that vision in these butterflies is mostly monocular and that males have more acute vision than females, especially in the frontal region (large facets, small interommatidial angles, small acceptance angles, long rhabdoms, and a close match between interommatidial angles and acceptance angles). This study also suggests that perched males direct their most acute vision where females are likely to appear but show no eye modifications that appear clearly related to a mate-locating tactic.     

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...