Junctional structures in the crystalline cone of the crayfish compound eye

1976 ◽  
Vol 173 (3) ◽  
Author(s):  
JoanL.M. Roach
Keyword(s):  
Compound Eye ◽  
Crystalline Cone

scholarly journals Some aspects of vision in the lobster, Homarus vulgaris, in relation to the structure of its eye

1963 ◽  
Vol 43 (3) ◽  
pp. 683-699 ◽  
Author(s):  
Elizabeth M. Kampa ◽  
Bernard C. Abbott ◽  
Brian P. Boden
Keyword(s):  
Compound Eye ◽  
Crystalline Cone ◽  
Cone Cells ◽  
Retinular Cells

The compound eye of the lobster H. vulgaris has a single lobe; its ommatidia are uniform except in length. Each ommatidium consists of a corneal facet, two corneagenous cells, four cone cells, a four-part crystalline cone, an elongate cone stalk, seven retinular cells and a four-part rhabdom. Growth between the zoaeal and adult stages is primarily a lengthening of the cone stalk.

The compound eye as an indicator of age and shrinkage in Antarctic krill

1995 ◽  
Vol 7 (4) ◽  
pp. 387-392 ◽  
Author(s):  
S. Sun ◽  
William De La Mare ◽  
Stephen Nicol
Keyword(s):  
Body Length ◽  
Antarctic Krill ◽  
Compound Eye ◽  
Natural Populations ◽  
Late Summer ◽  
Euphausia Superba ◽  
The Body ◽  
Laboratory Population ◽  
Number Count ◽  
Crystalline Cone

Laboratory studies have shown that Antarctic krill (Euphausia superba) shrink if maintained in conditions of low food availability. Recent studies have also demonstrated that E. superba individuals may be shrinking in the field during winter. If krill shrink during the winter, conclusions reached by length-frequency analysis may be unreliable because smaller animals may not necessarily be younger animals. In this study, the correlation between the body-length and the crystalline cone number of the compound eye was examined. Samples collected in the late summer show an apparent linear relationship between crystalline cone number and body-length. From a laboratory population, it appears that when krill shrink the crystalline cone number remains relatively unchanged. If crystalline cone number is little affected by shrinking, then the crystalline cone number may be a more reliable indicator of age than body-length alone. The ratio of crystalline cone number to body-length offers a method for detecting the effect of shrinking in natural populations of krill. On the basis of the crystalline cone number count, it appears from a field collection in early spring that E. superba do shrink during winter.

Daily changes in the compound eye of a beetle ( Macrogyrus )

1983 ◽  
Vol 217 (1208) ◽  
pp. 265-285 ◽  
Keyword(s):  
Point Source ◽  
Light Adaptation ◽  
Compound Eye ◽  
Lucifer Yellow ◽  
Dense Layer ◽  
Clear Zone ◽  
Acceptance Angle ◽  
Crystalline Cone ◽  
Graded Index ◽  
Peak Sensitivity

(i) Graded index lenses in the cornea and the crystalline cone form the optical system in each ommatidium. (ii) By night the crystalline cone has a blunt ellipsoidal proximal end which contributes to the formation of a superposition image across the clear zone. By day the cone is a tapering point that is extended as a light guide through a dense layer of pigment. (iii) The action of extending the cone and moving the pigment towards the clear zone from between the cones occurs as the retinula-cell column contracts. (iv) Modelling of the ommatidial lens system shows how the superposition image is formed in the night eye, and suggests that axial rays are not well focused on the crystalline tract in the day eye. (v) All cells had peak sensitivity in the green near 552 nm. (vi) In the dark-adapted day eye, fields are ∆ ρ (acceptance angle) = 3.4–6.6°, narrowing to 2.8° minimum upon light adaptation. Sensitivity to a point source on axis is reduced during the day: the dark-adapted day eye requires 200 times more light to give the same response as the dark-adapted night eye. There is a further attenuation of about 100 upon light adaptation of the day eye. (vii) The superposition image of the night eye produces fields of width ∆ ρ = 12-15° at 50% sensitivity as recorded electrophysiologically, and therefore the image of a point source covers several rhabdoms. (viii) In recordings from single units in the night eye two bumps (effective photon captures) are counted when the intensity is such that one photon falls on the area of one facet, with parallel axial illumination at the peak of the spectral sensitivity, 552 nm. (ix) Marking of cells with Lucifer Yellow suggests that about four to six receptor units per ommatidium are involved, giving a sensitivity of eight to twelve bumps for the ommatidium at this intensity. (x) Locust apposition eyes, with facets twice the area of those in Macrogyrus eyes, give at best 0.5 bumps with the same intensity, so that the actual superposition gain is 32–48. (xi) All marked cells were of the proximal rhabdom layer; cells 1 and 8 have not been investigated.

The dioptric system of the eye of Cybister (Dytiscidae: Coleoptera)

1973 ◽  
Vol 183 (1071) ◽  
pp. 159-178 ◽  
Keyword(s):  
Refractive Index ◽  
Ray Tracing ◽  
Compound Eye ◽  
High Sensitivity ◽  
Proximal Part ◽  
Focal Region ◽  
Clear Zone ◽  
Acceptance Angle ◽  
Crystalline Cone ◽  
Fuzzy Image

1. The compound eye of Cybister is anatomically similar to that of Dytiscus and Hydrophilus . 2. The cornea and crystalline cone in the compound eye of Cybister (Dytiscidae) are composed of layers of unequal refractive index. With the exception of the outer 10 µ m of the cornea (where they are horizontal) the layers are arranged concentrically around a region of highest refractive index on the axis. 3. The refractive index of the cornea decreases from the central layer (1.724) to the periphery (1.561). The corresponding values for the crystalline cone are 1.435 and 1.366. The refractive index of the area between cornea and cone is 1.343; that of the clear zone is 1.341, and that of the proximal rhabdom is 1.361. 4. Parallel rays entering a facet converge to a focal region which extends from the proximal part of the cornea to the distal part of the cone. Rays cross the clear zone in a direction which depends on the angle to the axis and position on the facet. Up to an angle of 32° to the axis the rays are mainly bent back into the quadrant of origin so that rays entering many facets converge to a second focal region beyond the clear zone. These findings are consistent with the report of a first inverted although fuzzy image in the cone and a second image (Exner 1891). 5. Ray diagrams were constructed for three different positions of the distal pigment. If the cone tip is completely exposed, the receptor acceptance angle is 46°. With the pigment in the typical dark-adapted position the field of view is 38° wide. A light-adapted ommatidium would have an admission function about 18° wide according to ray tracing, but this could be reduced by the properties of the crystalline tract down which the light must pass. 6. It is concluded from the ray tracing that acuity is poor, but summation across the clear zone could confer a high sensitivity for the dark-adapted eye.

Computer Reconstruction of the Cellular Architecture of the Daphnia Magna Optic Ganglion

1975 ◽  
Vol 33 ◽  
pp. 284-285
Author(s):  
E. R. Macagno ◽  
C. Levinthal
Keyword(s):  
Daphnia Magna ◽  
Genetic Background ◽  
Compound Eye ◽  
Synaptic Connectivity ◽  
Serial Sections ◽  
Cross Sectional ◽  
Small Crustacean ◽  
Optic Ganglion ◽  
Structural Invariance ◽  
High Degree

The optic ganglion of Daphnia Magna, a small crustacean that reproduces parthenogenetically contains about three hundred neurons: 110 neurons in the Lamina or anterior region and about 190 neurons in the Medulla or posterior region. The ganglion lies in the midplane of the organism and shows a high degree of left-right symmetry in its structures. The Lamina neurons form the first projection of the visual output from 176 retinula cells in the compound eye. In order to answer questions about structural invariance under constant genetic background, we have begun to reconstruct in detail the morphology and synaptic connectivity of various neurons in this ganglion from electron micrographs of serial sections (1). The ganglion is sectioned in a dorso-ventra1 direction so as to minimize the cross-sectional area photographed in each section. This area is about 60 μm x 120 μm, and hence most of the ganglion fit in a single 70 mm micrograph at the lowest magnification (685x) available on our Zeiss EM9-S.

Actin and α-tubulin immuno-EM labelings reveal differences in intra versus interphotoreceptor matrix

1990 ◽  
Vol 48 (3) ◽  
pp. 466-467
Author(s):  
Matti Järvilehto ◽  
Riitta Harjula
Keyword(s):  
Compound Eye ◽  
Frozen Section ◽  
Smooth Muscle Actin ◽  
Photoreceptor Cells ◽  
Immune Serum ◽  
Cell Organelles ◽  
Calliphora Erythrocephala ◽  
Optical Axes ◽  
Interphotoreceptor Matrix ◽  
Similar Kind

The photoreceptor cells in the compound eyes of higher diptera are clustered in groups (ommatidia) of eight receptor cells. The cells from six adjacent ommatidia are organized into optical units, neuro-ommatia sharing the same visual field. In those ommatidia the optical axes of the photopigment containing structures (rhabdomeres) are parallel. The rhabdomeres of the photoreceptor cells are separated from each other by an interstitial i.e innerommatidial space (IOS). In the photoreceptor cell body, besides of the normal cell organelles, a cellular matrix is a structurally apparent component. Similar kind of reticular formation is also found in the IOS containing some unidentified filamentary substance, of which composition and functional significance for optical properties of vision is the aim of this report.The prefixed (2% PA + 0.2% GA in 0.1-n phosphate buffer, pH 7.4, for 1h), frozen section blocks of the compound eye of the blowfly (Calliphora erythrocephala) were prepared by immuno-cryo-techniques. The ultrathin cryosections were incubated with antibodies of monoclonal α-tubulin and polyclonal smooth muscle actin. Control labelings of excess of antigen, non-immune serum and non-present antibody were perforated.

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