The ommatidium of the dorsal eye of Cloeon as a specialization for photoreisomerization

1976 ◽  
Vol 193 (1110) ◽  
pp. 17-29 ◽  
Keyword(s):  
Large Scale ◽  
Light Adaptation ◽  
Clear Zone ◽  
Angular Sensitivity ◽  
Cell Column ◽  
Screening Pigment ◽  
Double Function ◽  
Corneal Lens ◽  
Visible Wavelengths ◽  
Light Guides

The turbanate dorsal eyes of Cloeon have thin biconvex corneal facets, large crystalline cones, and long retinula cells which cross the clear zone. There is no large-scale movement of screening pigment upon adaptation. The combination of anatomical features suggests that the eye operates with high visual acuity because the corneal lens is focused on the tip of the cone, from which light is guided by the retinula cell column across the clear zone. By this means the eye could function near the diffraction limit. The suggestion that the main visual path is by light guides has some experimental support from examination of embedded shoes of the eye, but leaves no function for the clear zone, as there is negligible movement of pigment upon light adaptation. A clue to the function of the clear zone is provided by the unique appearance of a distal collection of rhabdom microvilli which are formed by all seven retinula cells around the tip of the crystalline cone. This distal rhabdom necessarily acts as a filter for light which crosses the clear zone. It is suggested that this light is utilized in the photoregeneration of the visual pigment after the effective visible wavelengths have been reduced. Filtering at this level could prevent unfocused regenerative rays, which cross the clear zone, from interfering with the angular sensitivity of the receptors. In other clear zone eyes, screening pigment around the cone tip could similarly serve a double function by acting as the aperture of the light guide and at the same time transmitting photoregenerative rays which cross the clear zone outside the light guides.

Movement on dark–light adaptation in beetle eyes of the neuropteran type

1971 ◽  
Vol 179 (1054) ◽  
pp. 73-85 ◽  
Keyword(s):  
Outer Layer ◽  
Light Adaptation ◽  
Pigment Cells ◽  
Retinula Cell ◽  
Clear Zone ◽  
Dark Light ◽  
Light Guides

Beetles of several species belonging to the families Carabidae, Dytiscidae, Gyrinidae and Hydrophilidae have an eye of the neuropteran type which is characterized as follows. In the dark-adapted state a long column formed by retinula cells (in these families numbering seven) stretches from the cone tip to the rhabdom layer. In the light a crystalline tract, formed from the outer layer of the cone, extends about 100 µ m from the cone and is surrounded by pigment cells. Scarabaeid beetles examined are similar but lack the distal rhabdomere always found in the above groups. All have a basal retinula cell with rhabdomere. In the scarabaeids the retinula cell columns have a content of solids greater than the surrounding cells, suggesting that they act as light guides across the clear zone.

Design of graded-index lenses in the superposition eyes of scarab beetles

1981 ◽  
Vol 294 (1075) ◽  
pp. 589-632 ◽  
Keyword(s):  
Refractive Index ◽  
Focal Plane ◽  
Focal Point ◽  
Image Plane ◽  
Optic Axis ◽  
Clear Zone ◽  
Crystalline Cone ◽  
Screening Pigment ◽  
Corneal Lens ◽  
Intermediate Image

Superposition-image quality in the clear-zone eye depends in the first instance on the optical characteristics of the lens elements in each ommatidium. The optical design strategy of the two lens elements, a thick corneal facet and an underlying crystalline cone, in the scarab eye is reported. The formation of a good superposition image at the rhabdom layer in the eye demands that the lens elements be precisely arrayed, virtually free of optical aberrations, and that each lens pair function as an afocal (telescopic) lens system with an internal intermediate focal plane. The optical properties of the corneal facet were examined by a variety of means. The isolated corneas of most scarab species focused good quality images of a distant object. Cardinal-point analysis of the intact corneal lens revealed that the back focal point of the lens lies just proximal to the inner corneal surface, many micrometres distal to the rhabdom layer, and the position of the principal planes suggested that the corneal lens had internal lens-cylinder properties. This was confirmed by the examination of the focusing power of transverse lens slices of known thickness; the power of the corneal lens slice was a function of its thickness. Interference refractometry of corneal sections revealed that the facet is a graded-refractive-index (g.r.i.) lens in the great majority of more than 40 scarab species examined. The position of the back focal point is achieved in a thick corneal lens by (i) the presence of a g.r.i. lens, best developed in the proximal corneal region, where it consists of a g.r.i. lens cylinder capped by a g.r.i. lens hemisphere, and (ii) the loss of front facet curvature in the homogeneous distal corneal region. In situ , the back focal point lies deep within the crystalline cone. Since the quality of the superposition image depends on the exact location of the intermediate-image plane in the crystalline cone, this position was determined from a comparative analysis of cone shape, experimental observations, and theoretical modelling of the cone. Four observations, namely the presence of a waist in the crystalline cone of many species, the back focal distance of the isolated cornea when the refractive index (r.i.) of the medium in the back focal space approximated that situ, the presence of screening pigment around specific regions of the crystalline cone and the position of the intermediate-image plane in the exocone of a passalid beetle eye, all suggested that the intermediate focus lies in the waist region. The proximal region of the crystalline cone was modelled on the basis of its known g.r.i. lens properties. The model used comprised a radial g.r.i. lens cylinder with a parabolic profile in r.i., terminating in a g.r.i. lens hemiellipsoid. Dimensions and r.i. distribution in the model were based on values from real cones. The model cone focused an incident parallel beam to a point within the cone corresponding to the waist region in real cones. For beams at angles as great as 20° to the optic axis, aberrations in the model cone are small, and restricted to the most peripheral rays. A homogeneous hemiellipse of similar dimensions has severe aberrations for beams at an angle to the optic axis. The model predicts that the ommatidial optics are diffraction-limited; the spread of rays leaving the proximal cone tip due to diffraction at the small exit aperture of the cone (for all aperture diameters) is broader than that due to lens aberrations. Consequently, tolerance exists to optical imperfections in the lens components and their spacing. A tolerance in the position of the intermediate focal plane of + 2-3 pm was calculated. Lens design is strongly correlated with the daily activity pattern of the scarab species under consideration. The corneal facets of nocturnal and crepuscular species are wide with little individual facet curvature; such ‘glacial’ corneas are completely transparent. The crystalline cone is large and well developed. In diurnal species, the corneal facets are narrower, with strong individual curvature, and the corneal lens cylinders are often lined with a brown screening pigment. The crystalline cones of diurnal scarabs are frequently strongly waisted or greatly reduced in size. Pigment surrounding the cone waist serves as a field stop limiting the angular acceptance of the ommatidial optics. The waist limits the number of ommatidia that can contribute to the superposition image and therefore determines the maximum aperture of the eye. This aperture is greatest in nocturnal species with little or no waist constriction in the crystalline cone. Most scarab clear-zone eyes are of the eucone type (separate crystalline cone). However, in the Passalidae and bolboceratine and pleocomine Geotrupidae, the crystalline cone is replaced by a corneal g.r.i. lens extension, the exocone, that serves as an optical analogue of the crystalline cone.

Diurnal changes in retinula cell sensitivities and receptive fields (two-dimensional angular sensitivity functions) in the apposition eyes of Ligia exotica (Crustacea, Isopoda)

2001 ◽  
Vol 204 (2) ◽  
pp. 239-248 ◽  
Author(s):  
T. Hariyama ◽  
V.B. Meyer-Rochow ◽  
T. Kawauchi ◽  
Y. Takaku ◽  
Y. Tsukahara
Keyword(s):  
Receptive Fields ◽  
Resolving Power ◽  
Pigment Cells ◽  
Diurnal Changes ◽  
Two Dimensional ◽  
Angular Sensitivity ◽  
Pigment Granules ◽  
Screening Pigment ◽  
The Difference ◽  
Night And Day

The structural organization of the retinula cells in the eye of Ligia exotica changes diurnally. At night, the microvilli elongate, losing the regular and parallel alignment characteristic of the day condition. Crystalline cones and distal rhabdom tips are not pushed into each other during the day, but at night the rhabdoms protrude into the crystalline cones by up to 5 microm. Screening pigment granules in the retinula cells disperse during the night, but migrate radially towards the vicinity of the rhabdom during the day. No such displacements of the pigment granules of either distal or proximal screening pigment cells were observed. The sensitivity of the eye, monitored by electroretinogram (ERG) recordings, changes diurnally: values at midnight are, on average, 10 times those occurring during the day. However, intracellular recordings from single retinula cells (50 during the day and 50 at night) indicate that the difference between night and day sensitivities is only 2.5-fold. Two-dimensional angular sensitivity curves, indicative of a single unit's spatial sensitivity, had considerably less regular outlines at night than during the day. If based on the 50 % sensitivity level, day and night eyes possessed receptive fields of almost identical width (approximately 2 degrees), but if sensitivities below the 50 % limit were included, then receptive fields at night were significantly more extensive. We suggest that the morphological adaptations and diurnal changes in chromophore content seen in the apposition eye of L. exotica allow this animal to improve its photon capture at night while preserving at least some of the spatial resolving power characteristic of the light-adapted state. This would explain why this animal is capable of performing complex escape behaviours in the presence of predators both in bright and in very dim light.

Changes of Acuity during Light and Dark Adaptation in the Dragonfly Compound Eye

1990 ◽  
Vol 45 (1-2) ◽  
pp. 137-142 ◽  
Author(s):  
Eric J. Warrant ◽  
Robert B. Pinter
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Compound Eye ◽  
Sensitivity Function ◽  
The State ◽  
Intracellular Recordings ◽  
Acceptance Angle ◽  
Angular Sensitivity ◽  
Rapid Reduction

Abstract Intracellular recordings of angular sensitivity from the photoreceptors of Aeschnid dragonflies (Hemianax papuensis and Aeschna brevistyla) are used to determine the magnitude and time course of acuity changes following alterations of the state of light or dark adaptation. Acuity is defined on the basis of the acceptance angle, Δρ (the half-width of the angular-sensitivity function). The maximally light-adapted value of Δρ is half the dark-adapted value, indicating greater acuity during light adaptation. Following a change from light to dark adaptation, Δρ increases slowly, requiring at least 3 min to reach its dark-adapted value. In contrast, the reverse change (dark to light) induces a rapid reduction of Δρ , and at maximal adapting luminances, this reduction takes place in less than 10 sec.

Light guides in the dorsal eye of the male mayfly

1982 ◽  
Vol 216 (1202) ◽  
pp. 25-51 ◽  
Keyword(s):  
Ultraviolet Light ◽  
Compound Eye ◽  
Lucifer Yellow ◽  
Single Units ◽  
Polarization Sensitivity ◽  
Clear Zone ◽  
Tight Coupling ◽  
Acceptance Angle ◽  
Yellow Light ◽  
Light Guides

(i) The dorsal eyes are sensitive to ultraviolet light, which is focused by the corneal lens into crystalline cones in the region where these taper progressively to columns across the clear zone. The action of these columns as light guides can be observed in fixed eyes embedded in polymerized resin. In life the light guide part of the column is surrounded by watery non-cellular haemolymph. (ii) Shadowing the eye surface with a thin wire (three facets wide) while recording from individual receptor units shows that ultraviolet light reaches each receptor by its own facet as in an apposition eye, and not, as in a superposition eye, by a group of many facets. (iii) As shown by the dye Lucifer Yellow injected from a microelectrode, the electrophysiological unit consists of all seven retinula cells in the rhabdom region. Consistent with this tight coupling of retinula cells there is no polarization sensitivity. The peak spectral sensitivity of all single units is at 345-365 nm in the ultraviolet. The acceptance angle is 2.0–2.5°. The sensitivity at the spectral peak to a point source on the optical axis of the unit is poor compared to that in other insects tested with the same equipment. (iv) The acceptance angles (∆ ρ ) in the dorsal eye are at the theoretical minimum for the facet diameter and wavelength from diffraction theory. Ultraviolet vision, therefore, has made possible a reduction in facet size but the interommatidial angle ∆ ϕ is greater than expected from the optimum sampling theory of the diffraction limited compound eye. In fact ∆ ρ ≈ ∆ ϕ ≈ 2°. (v) The dorsal eye is effectively a foveal region with greater sampling density and narrower receptive fields but less overlap of fields than the lateral eye. (vi) The square cones and yellow screening pigment strongly suggest that there is superposition by reflexion of yellow light that spreads between ommatidia across the clear zone. This yellow light might photoreisomerize the visual pigment. Attempts to prove this theory during the recording from single units have so far failed but no better function for the clear zone has been suggested.

EFFECT OF DIFFERENT LIGHTING CONDITIONS ON FEEDING ACTIVITY AND EYE ADAPTATION OF POST LARVAE PENAEUS VANNAMEI

2015 ◽  
Vol 77 (33) ◽  
Author(s):  
Noorsyarinah Sanudin ◽  
Audrey Daning Tuzan ◽  
Gunzo Kawamura ◽  
Annita Seok Kian Yong
Keyword(s):  
Feeding Activity ◽  
Light Condition ◽  
Larval Feeding ◽  
Penaeus Vannamei ◽  
Dark Condition ◽  
Clear Zone ◽  
Lighting Conditions ◽  
Pigment Granules ◽  
Screening Pigment ◽  
Dark Conditions

This study was conducted to investigate the effect of light and dark conditions on feeding activity and eye adaptations of post larvae (PL5, PL10, PL20 and PL30) Penaeus vannamei fed with frozen Artemia. Shrimp PL were placed individually in beakers and after acclimatization under the light or dark condition, PL were left to ingest known number of Artemia for 30 minutes. Thereafter, each PL was subsequently anesthetized by putting an ice cube into the beakers followed by adding few drops of paraformaldehyde. The results showed that the PL5 ingested significantly more frozen Artemia under light condition compared to dark condition (P<0.05). The eye structures of PL5 comprises of crystalline cone, rhabdom and fasciculated zone. However, it was incomplete due to the lack of clear zone and no migration of the screening pigment granules was observed under light and dark conditions. On the contrary, the number of frozen Artemia ingested by the latter stages PL10, PL20 and PL30 showed no significant differences (P>0.05) under both light conditions and these PL have complete eye structures with define clear zone. The width of clear zone was found to increase proportionally with the growth of the PL. Besides that, the screening pigment granules were able to migrate under light and dark conditions. The ability of the PL10, PL20 and PL30 to ingest almost similar numbers of Artemia under light and dark conditions suggests that different lighting conditions did not affect the feeding activity of the PL and other sensory organs may play roles in detecting food, while PL5 need light to improve their feeding activity. Based on these results, we suggest that in aquaculture practice, during the rearing of early stage of PL (<PL5), a brighter environment or light should be provided to enhance larval feeding activities. Whereas, later stages of PL (>PL10) can be cultured under any light condition.

The ommatidium of the lacewing Chrysopa (Neuroptera)

1976 ◽  
Vol 192 (1108) ◽  
pp. 259-271 ◽  
Keyword(s):  
Signal To Noise Ratio ◽  
Visual Fields ◽  
Neural Mechanism ◽  
Retinula Cell ◽  
Cell Nuclei ◽  
Clear Zone ◽  
Parallel Beam ◽  
Cell Column ◽  
Spatial Frequencies ◽  
Different Levels

The eye is a clear zone eye with extensive movement of retinula cells on adaptation to light. The ommatidium has three types of rhabdomere, at different levels, so that the eye necessarily abstracts at least three kinds of information simultaneously from the incoming rays. In the lightadapted state light can enter each ommatidium only via a crystalline tract that is surrounded by dense pigment grains. A small distal rhabdomere (cell 7) always lies at the end of this tract. In the dark-adapted eye the retinula cell nuclei and distal rhabdomere move to the cone tip and the crystalline tract is drawn into the cone. There is then a region of the retinula cell column, between cone tip and proximal rhabdoms, across which there is no structure that could act as a light guide. A key question, therefore, is how the light is focused across this clear zone in the darkadapted state. As shown by the wide angular distribution of eyeshine when a parallel beam is incident on the dark-adapted eye, rays are poorly focused upon the columns of the large rhabdoms. The wide visual fields of receptors 1-6 in the dark-adapted eye, inferred from the observation of eyeshine, are seen as a way of narrowing the bandwidth of spatial frequencies, so that only the largest objects in the visual field contribute to motion-detection. This would improve the signal-to-noise ratio, not in the receptors themselves, but in the neural mechanism, by simplifying the incoming signal.

The dorsal eye of the mayfly Atalophlebia (Ephemeroptera)

1978 ◽  
Vol 200 (1139) ◽  
pp. 137-150 ◽  
Keyword(s):  
Visual Pigment ◽  
Current Flow ◽  
Yellow Pigment ◽  
The Other ◽  
Retinula Cell ◽  
Clear Zone ◽  
Large Size ◽  
Sharp Focus ◽  
Pigment Distribution ◽  
Light Guides

The dorsal eye of Atalophlebia has two unusual features, the sensitivity only to ultraviolet (u. v.) light, and the candelabra-shaped rhabdom. In addition, the crystalline cone is surrounded to its tip by a yellow pigment, and the tip tapers gradually as a dense fibre. These details, particularly the pigment distribution, indicate that a superposition image cannot be formed by u. v. light. Also, there is no refracting or reflecting structure that could form a sharp superposition image. Instead, it is suggested that u. v. rays are sharply focused on the cone tip and conducted by the retinula cell columns acting as light guides across the clear zone. Light of longer wavelength, on the other hand, is partially focused through the yellow pigment, and, although it is not seen by the insect, it is available to photoregenerate the visual pigment. This method of boosting sensitivity is appropriate for a pure u. v. eye and does not require a sharp focus of the regenerative rays, although the clear zone is an essential part of the mechanism. The rhabdom has an extraordinary shape like a flat 5-armed candelabra in cross section, with five posteriorly directed arms which are formed by six retinula cells. There is also a 7th retinula cell without a rhabdomere. This cell penetrates laterally the rhabdom of the other six, and also forms a sheath around half of its own ommatidium and half of the the adjacent ommatidium. The exceptional relations between this cell, and the other six, together with the orientated candelabra pattern of the rhabdom, and the large size of the 7th retinula axon, is interpreted as a way of enhancing the current flow down the 7th axon which runs direct to the medulla, bypassing the lamina.

Light Guides for Tunnels

1996 ◽  
Vol 1553 (1) ◽  
pp. 81-85
Author(s):  
Jeffrey P. Sheldon ◽  
Paul J. Lutkevich
Keyword(s):  
Design Process ◽  
Large Scale ◽  
Careful Study ◽  
Light Guides

The use of light guides has been limited to accent or specialty lighting and generally has been considered impractical for large-scale applications. After careful study, 2 mi of light guides were installed in Boston's Callahan Tunnel. The 2-year study and design process is reviewed, and the system's performance after a year of operation is assessed.

Alternatives to superposition images in clear-zone compound eyes

1971 ◽  
Vol 179 (1055) ◽  
pp. 97-124 ◽  
Keyword(s):  
Scattered Light ◽  
Retinula Cell ◽  
Compound Eyes ◽  
Clear Zone ◽  
Light Effect ◽  
Angular Sensitivity ◽  
Dim Light ◽  
Optical Pathway ◽  
Receptor Layer

The clear zone between the cones and the receptor layer in dark -adapted eyes of insects that are active in dim light has formerly been explained as a space to allow formation of a superposition image. Although erect images have been seen in Ephestia (Lepidoptera) and Hydrophilus (Coleoptera), new experiments show that they are accompanied by scattered light and that the angular sensitivity of individual receptors must be wide in the dark-adapted state. Alternatives to the superposition theory are examined, and it is concluded that in eyes with crystalline cones the clear zone (in general, in the numerous shapes and sizes of eyes of nocturnally active insects) enables light entering by many facets to sum upon individual receptors on the far side of the clear zone. In addition to the scattered light effect, light is carried across the clear zone in crystalline tracts or retinula cell columns, which provide a separate optical pathway for each ommatidium also in the light-adapted state.

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