Eye structure and optics in the pelagic shrimp Acetes sibogae (Decapoda, Natantia, Sergestidae) in relation to light-dark adaptation and natural history

1986 ◽  
Vol 313 (1160) ◽  
pp. 251-270 ◽  
Keyword(s):  
Natural History ◽  
Basement Membrane ◽  
Focal Length ◽  
Pigment Cells ◽  
Retinula Cell ◽  
Maximum Diameter ◽  
Membrane Turnover ◽  
Image Brightness ◽  
Crystalline Cone ◽  
Cone Cells

The structure and optics of the compound eyes of the neritic sergestid shrimp, Acetes sibogae , are described. The eyes are nearly spherical and heavily pigmented. The facets are square, indicating that the eye operates by the recently recognized mechanism of reflecting superposition. The most distal portion of each ommatidium is the corneal lens, which is secreted by two underlying corneagenous cells. These two cells surround the crystalline cone and cone stalk and the four cells of which they are composed and extend proximally at least as far as the distal rhabdom. Near the base of the cone stalk the extensions of the corneagenous cells swell and enclose spheres which bear on their surfaces small particles similar to ribosomes in appearance. Beneath the corneagenous cells lie four crystalline cone cells, parts of which differentiate to form the crystalline cone and cone stalk. The latter structures are compound, one quarter of each being contributed by each crystalline cone cell. Distally the crystalline cone cells send a small projection, which is surrounded by the corneagenous cells, to the cornea. Proximal extensions of each of the four parts of the cone stalk extend between the retinula cells and meet within the basement membrane. Between the base of the cone stalk and the regularly layered rhabdom lies the distal rhabdom. It is surrounded by a cell that we have termed retinula cell eight (R8), by analogy with other crustacean systems, and consists of unordered microvilli projecting from the cell membrane into the extracellular space above the layered rhabdom. In addition to R 8, which contributes only to the distal rhabdom, seven other retinula cells contribute to the proximal rhabdom, which consists of alternating ordered layers of orthogonally arranged microvilli. Four of these retinula cells are arranged orthogonally and extend far distally along the crystalline tract. The other three do not extend as far distally and alternate with the first four in their position around the axis of the ommatidium. R8 is located still further proximally at the level of the distal rhabdom. All seven of the retinula cells which contribute to the proximal rhabdom contain proximal pigment and extend through the basement membrane. The basement membrane consists of a meshwork grid with each intersection supporting a rhabdom so at this point the retinula cell axons project into different squares of the meshwork. Tapetal pigment cells are present in the vicinity of the basement membrane and extend downward to the lamina. The granules of tapetal pigment are covered or exposed by movements of the proximal pigment and also change their intracellular distribution depending on illumination. In addition to the proximal (retinula cell) pigment and the tapetal pigment the eye contains four types of distal pigment. Moving inward from the cornea these are the distal yellow pigment (DYP) which surrounds the entire eye; the distal reflecting pigment (DRP), which forms a thin layer and is continuous with the tapetal pigment at the edge of the eye; and the black distal pigment and the mirror pigment (MP) both contained within distal pigment cells (DPC). In the light-adapted state the proximal pigment moves distally, surrounding the rhabdoms, and the tapetal pigment granules move proximally so that they are mainly found beneath the basement membrane. Movements of the distal pigments are less clearcut, but they all appear to move somewhat proximally in the light-adapted state. Multivesicular bodies are more abundant in the retinula cells shortly after dawn, and are possibly related to membrane turnover. Interommatidial angle, as measured on both fixed and fresh material, varied from 2.8 to 3.8° in different parts of the eye. The crystalline cones were found to have a uniform refractive index radially, which, combined with their square shape, indicates that they function by reflecting superposition. Total internal reflection from the sides of the cones is adequate to explain the maximum diameter of the eyeshine from the dark-adapted eye at night without the need for additional mirrors. Nevertheless, from its organization and appearance the mirror pigment could act as a reflector in the dark-adapted eye. Also, the size of the glow patch indicates that there would be a gain of nearly two log units in image brightness in going from the light-adapted to the dark-adapted state. Each corneal facet was found to act as a weak converging lens, with a focal length of approximately 300 μm. The eye structure of Acetes is discussed in relation to that of other shrimp and to the natural history of Acetes .

The retina of Ephestia (Lepidoptera)

1971 ◽  
Vol 179 (1055) ◽  
pp. 87-95 ◽  
Keyword(s):  
Refractive Index ◽  
Basement Membrane ◽  
Basal Cell ◽  
Light Guide ◽  
High Refractive Index ◽  
Pigment Cells ◽  
Retinula Cell ◽  
Accessory Cells ◽  
Long Rod ◽  
Pyralid Moth

The ommatidium of the pyralid moth Ephestia has ten similar retinula cells and one basal cell (with rhabdomere). A long rod of rhabdom material of high refractive index, contributed by all ten retinula cells, runs up the centre of the column of ten retinula cells and ends at the crystalline tract in the light-adapted eye. Considerable movements of cells occur on adaptation. In the dark-adapted eye the retinula cell columns stretch from the cone tip to the rhabdom layer, with no crystalline tract. In the light-adapted eye a crystalline tract, surrounded by principal pigment cells, extends from the cone. The retinula cell columns appear histologically as if they contain more protein than the surrounding accessory cells. This has an optical significance in providing a further light guide outside the rhabdom extension. A layer of bacteria-like bodies lies between the extensive tapetum of trachea and the basement membrane.

In vivo biosynthesis and turnover of glomerular basement membrane in diabetic rats

1982 ◽  
Vol 242 (4) ◽  
pp. F385-F389
Author(s):  
M. P. Cohen ◽  
M. L. Surma ◽  
V. Y. Wu
Keyword(s):  
Basement Membrane ◽  
Glomerular Basement Membrane ◽  
Diabetic Rats ◽  
Basement Membranes ◽  
Membrane Turnover ◽  
Proline Incorporation ◽  
Basement Membrane Collagen ◽  
Osmotic Lysis ◽  
Specific Activities

Glomerular basement membrane (GBM) was labeled in vivo by the injection of tracer amounts of tritiated proline into normal and streptozotocin-diabetic rats. Basement membrane biosynthesis and turnover were determined from the specific activities of proline and hydroxyproline in samples purified following osmotic lysis of glomeruli isolated 4 h to 12 days after injection. Peak radiolabeling of normal and diabetic GBM occurred within 24-48 h and 48-72 h, respectively, and, when corrected for differences in the serum proline specific activities, [3H]proline incorporation was greater in diabetic than in normal samples. In contrast to the subsequent time-dependent progressive decline in radiolabeling in basement membranes from normal animals, specific activities of proline and hydroxyproline in diabetic glomerular basement membrane did not change significantly over the same period of observation. Renal cortical mass and glomerular basement membrane collagen content were preserved in diabetic animals despite loss of body weight. The findings are compatible with prolongation of glomerular basement membrane turnover in experimental diabetes, and suggest that diminished degradation contributes to the accumulation of glomerular basement membrane that is characteristic of chronic diabetes.

The Morphology of the Pecten Oculi and the Conus Papillaris

1968 ◽  
Vol 26 ◽  
pp. 170-171
Author(s):  
R. F. Dunn
Keyword(s):  
Basement Membrane ◽  
Pigment Cell ◽  
Pigment Cells ◽  
Capillary Endothelium ◽  
House Finch ◽  
Osmiophilic Granules ◽  
Pecten Oculi ◽  
Tissue Space ◽  
Endothelial Basement Membrane ◽  
Connective Tissue Space

In this study, the pecten of the house finch, and the conus of the gecko, Eublipharis, were utilized. The structure of the house finch pecten resembled that of the pigeon. The capillary endothelium is characterized by an extensive luminal and abluminal system of plasma membrane plications (Fig. 1, LP and AP). The luminal ridges vary in length from 1.3 - 2.9μ, and are 40-90 mμ in width. The luminal and abluminal plications are separated by the narrow, rather dense endothelial cytoplasm which contains free ribosomes and dense mitochondria in addition to granular cytomembranes. The abluminal ridges are generally shorter, and rest on a basement membrane. Many of the pecten surface capillaries are separated from the vitreous by only a short distance of about 1μ. In other regions the capillaries are surrounded by pigmented cells, which contain smooth surfaced, very osmiophilic granules up to 1.6μ in diameter, a few smaller, irregularly shaped granules and the usual compliment of cytoplasmic organelles (Fig. 2).In sharp contrast to the pecten, the endothelium of the conus is relatively smooth and lacks any surface foldings as well as any fenestrations (Fig. 3). The endothelial basement membrane is separated from that of the pigment cell by a variable extracellular connective tissue space containing many collagen fibrils. The pigment cells contain melanin granules similar to those of the pecten (Fig.4).

Local induction of patterning and programmed cell death in the developing Drosophila retina

Development ◽  
1998 ◽  
Vol 125 (12) ◽  
pp. 2327-2335 ◽  
Author(s):  
D.T. Miller ◽  
R.L. Cagan
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Egf Receptor ◽  
Pigment Cells ◽  
Cell Fates ◽  
Adult Retina ◽  
Ras Pathway ◽  
Cell Ablation ◽  
Cone Cells ◽  
Local Cell

Local cell signaling can pattern the nervous system by directing cell fates, including programmed cell death. In the developing Drosophila retina, programmed cell death is used to remove excess cells between ommatidia. Cell ablation revealed the source and position of signals required for regulating the pattern of programmed cell death among these interommatidial cells. Two types of signals regulate this patterning event. Notch-mediated signals between interommatidial precursors result in removal of unneeded cells. Cone cells and primary pigment cells oppose this signal by supplying a ‘life’-promoting activity; evidence is provided that this signal occurs through localized activation of the EGF Receptor/Ras pathway. Together, these signals refine the highly regular pattern observed in the adult retina.

On the Function of the Interstitium of the Testis

1949 ◽  
Vol s3-90 (11) ◽  
pp. 265-280
Author(s):  
A. J. MARSHALL
Keyword(s):  
Connective Tissue ◽  
Leydig Cell ◽  
Leydig Cells ◽  
Secretory Component ◽  
Endocrine Function ◽  
Pigment Cells ◽  
Maximum Diameter ◽  
Breeding Area ◽  
Anatomical Basis ◽  
Tissue Cells

1. An investigation of the seasonal cycle of the interstitium of the testes of birds, based on sixty-four individuals of varying age, has been carried out on the fulmar petrel, Fulmaris glacialis (L.). 2. The following cells (see diagram, p. 268) occur: (i) Fibroblasts of the sheaths of tubules, blood-vessels, and of groups of Leydig cells. (ii) Pigment cells. (iii) Juvenile Leydig cells (generally containing lipoid droplets). (iv) Lipoid Leydig cells. (v) Fuchsinophil Leydig cells. (vi) Areolar connective-tissue cells. 3. In the young bird the juvenile cell develops into the lipoid Leydig cell at a time when the testis-tubules also indicate approaching sexual maturity. In the adult, the interstitium generally consists for the most part of lipoid Leydig cells. These exhibit mitochondria when the soluble lipoids are removed by embedding in wax. At the height of spermatogenesis, and at the beginning of epithelial breakdown and tubule-regression, most of the Leydig cells have lost much of their lipoids and some of them exhibit increasing amounts of fuchsinophil substances, as described by Benoit. A fuchsinophil cell thus appears. 4. The Lipoid cell at all seasons shows a positive Schultz reaction (for cholesterol), which corresponds in intensity to the amount of sudanophil material present. It has not been possible to demonstrate cholesterol in the fuchsinophil cell. 5. At the time when the tubules are at their maximum diameter and their degeneration is under way, mitochondria are at the greatest abundance in the Leydig cell. At this period a new generation of Leydig cells arises in the interstitium. These cells quickly become meagrely sudanophil and resemble the sudanophil juvenile cells of the immature bird. They are Schultz positive. The tubules collapse; the new Leydig generation fills the empty interstitium. They exhibit profuse mitochondria, gain in lipoid content and so the interstitium is regenerated. 6. The exhausted tubules undergo a fatty metamorphosis at the time of their collapse; at the period when the interstitium has little lipoid the tubules are full of it. Beneath this fat (also Schultz positive) arises a new tubule-epithelium. The tubules as well as the interstitium are regenerated while the young of the next generation are still in the nests. An anatomical basis for an internal physiological rhythm may thus have been shown. 7. The new interstitial cells are already heavily lipoidal and the new tubule epithelium contains spermatogonia when the petrels move seaward away from the breeding cliffs in the autumn. They return to the breeding area in November and December. Thus testis regeneration, and movement both away from and back to the breeding area, occurs while the days are getting shorter. 8. From the time the birds appear on the breeding cliffs (and apparently since the autumn) there is an increase in lipoid cells along with heightened sexuality as revealed by the ripening tubule-products. These supplementary lipoid Leydig cells seem to develop from the small non-sudanophil areolar connective-tissue cells which are prominent in the adult interstitium. 9. Whilst it is not denied that the fuchsinophil cell (‘secretory cell’ of Sluiter and van Oordt) may have an endocrine function, the present results suggest that the lipoid Leydig cell is the primary secretory component of the avian testis. When the interstitium, after reproduction, passes once more to a lipoidal phase, it is not losing its secretory function as Sluiter and van Oordt infer, but is regenerating in readiness for the next season's breeding activities.

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.

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.

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