Eyes as optical alarm systems in fan worms and ark clams

1994 ◽  
Vol 346 (1316) ◽  
pp. 195-212 ◽  
Keyword(s):  
Visual Motion ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
False Alarms ◽  
Compound Eyes ◽  
Receptor Cells ◽  
Alarm Systems ◽  
Large Numbers ◽  
Mantle Edge ◽  
Higher Sensitivity

Eye structure and optics were investigated in two sabellid polychaetes ( Sabella melanostigma, Dasychone conspersa ) and three arcacean bivalves ( Arca zebra, Barbatia cancellaria, Anadara notabilis ). The polychaetes have numerous compound eyes arranged in pairs along the branchial tentacles. Each ommatidium is composed of three cells: one receptor cell forming a ciliary receptive segment, and two pigment cells forming an extracellular lens (crystalline cone). The ark clams Area and Barbatia possess large numbers of compound eyes arranged along the mantle edge. The ommatidia of these eyes are composed of one or two ciliary receptor cells surrounded by several layers of pigment cells. There are no lenses in the ommatidia of the clam eyes. All three species of ark clam also have many pigment-cup eyes on the mantle edge. The cup eyes lack lenses, and the cavity of the cup is filled with rhabdomeric microvilli from the receptor cells. The crystalline cones in the sabellid compound eyes are powerful lenses that reduce the field of view of the receptor cells to slightly more than 10°. The lensless ommatidia of Barbatia have much larger fields of view (« 30°). This difference correlates with a behavioural response to much finer moving stripes in the fan worms. A comparison of compound eyes and cup eyes in Barbatia reveals a poor resolution in both, but a much higher sensitivity is estimated for the cup eyes. The tentacular eyes of fan worms and the mantle eyes of ark clams trigger protective responses: retraction into the tube and shell closure, respectively. The responses are triggered by visual motion and the eyes work as burglar alarms rather than imaging eyes. For this purpose, the compound eyes may seem to occur in affluent numbers: 240 eyes with a total of 12 000 ommatidia in Sabella and 300 eyes with a total of 39 000 ommatidia in Barbatia . The number of ommatidia that simultaneously monitors any direction in space is, on average, 43 in Sabella and 755 in Barbatia . The large number of eyes is explained as a visual strategy which provides a robust alarm system designed to reliably detect predators without causing false alarms. The literature on tentacular eyes of fan worms and mantle eyes of bivalves is reviewed, and the evolutionary origin of these independently-acquired visual organs is discussed. I suggest the possibility that hyperpolarizing photoreceptor cells (shadow detectors) evolved from chemoreceptors that were inhibited by light.

Differentiation Processes of the Ocellar Retina of the Honeybee (Apis Mellifera L.)

1990 ◽  
Vol 48 (3) ◽  
pp. 430-431
Author(s):  
Maria Anna Pabst
Keyword(s):  
Apis Mellifera ◽  
Distal Part ◽  
Cell Layer ◽  
Single Layer ◽  
Photoreceptor Cells ◽  
Distal Segment ◽  
Compound Eyes ◽  
Thin Sections ◽  
Ultrastructural Studies ◽  
Adult Worker

In addition to the compound eyes, honeybees have three dorsal ocelli on the vertex of the head. Each ocellus has about 800 elongated photoreceptor cells. They are paired and the distal segment of each pair bears densely packed microvilli forming together a platelike fused rhabdom. Beneath a common cuticular lens a single layer of corneagenous cells is present.Ultrastructural studies were made of the retina of praepupae, different pupal stages and adult worker bees by thin sections and freeze-etch preparations. In praepupae the ocellar anlage consists of a conical group of epidermal cells that differentiate to photoreceptor cells, glial cells and corneagenous cells. Some photoreceptor cells are already paired and show disarrayed microvilli with circularly ordered filaments inside. In ocelli of 2-day-old pupae, when a retinogenous and a lentinogenous cell layer can be clearly distinguished, cell membranes of the distal part of two photoreceptor cells begin to interdigitate with each other and so start to form the definitive microvilli. At the beginning the microvilli often occupy the whole width of the developing rhabdom (Fig. 1).

scholarly journals INHERITED RETINAL DYSTROPHY IN THE RAT

1962 ◽  
Vol 14 (1) ◽  
pp. 73-109 ◽  
Author(s):  
John E. Dowling ◽  
Richard L. Sidman
Keyword(s):  
Pigment Epithelium ◽  
Light And Electron Microscopy ◽  
Retinal Dystrophy ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Membrane Thickness ◽  
Outer Segments ◽  
Progressive Loss ◽  
Retinal Rods ◽  
Microscopy Data

Retinal dystrophies, known in man, dog, mouse, and rat, involve progressive loss of photoreceptor cells with onset during or soon after the developmental period. Functional (electroretinogram), chemical (rhodopsin analyses) and morphological (light and electron microscopy) data obtained in the rat indicated two main processes: (a) overproduction of rhodopsin and an associated abnormal lamellar tissue component, (b) progressive loss of photoreceptor cells. The first abnormality recognized was the appearance of swirling sheets or bundles of extracellular lamellae between normally developing retinal rods and pigment epithelium; membrane thickness and spacing resembled that in normal outer segments. Rhodopsin content reached twice normal values, was present in both rods and extracellular lamellae, and was qualitatively normal, judged by absorption maximum and products of bleaching. Photoreceptors attained virtually adult form and ERG function. Then rod inner segments and nuclei began degenerating; the ERG lost sensitivity and showed selective depression of the a-wave at high luminances. Outer segments and lamellae gradually degenerated and rhodopsin content decreased. No phagocytosis was seen, though pigment cells partially dedifferentiated and many migrated through the outer segment-debris zone toward the retina. Eventually photoreceptor cells and the b-wave of the ERG entirely disappeared. Rats kept in darkness retained electrical activity, rhodopsin content, rod structure, and extracellular lamellae longer than litter mates in light.

The Culture of Small Aggregates of Amphibian Embryonic Cells in vitro

Development ◽  
1963 ◽  
Vol 11 (1) ◽  
pp. 135-154
Author(s):  
K. W. Jones ◽  
T. R. Elsdale
Keyword(s):  
Pigment Cells ◽  
Two Dimensional ◽  
Embryonic Cells ◽  
Common Procedure ◽  
Large Numbers ◽  
Organ Type ◽  
Typical Cell ◽  
Primary Explant ◽  
Migration Of Cells

A Common procedure in amphibian embryology has been to remove portions from embryos and culture these under conditions in which the large numbers of cells retain a close-knit association, favourable to the differentiation of primitive organs in the explant. It has not, in general, been the aim to employ the primary explant as a source of a two-dimensional outgrowth of cells on the substrate, as in typical cell culture procedures. Because of their inherent migratory tendencies, however, outgrowths of pigment cells are readily obtained from explants of the amphibian neural crest, and these have stimulated the interest of a number of investigators (see Wilde, 1961). Holtfreter (1938, 1946) and Finnegan (1953) have also observed the migration of cells from explants of Urodele embryos. Several investigators have employed cell cultures as opposed to organ type cultures in induction studies, Niu & Twitty (1953), Niu (1958), Barth & Barth (1959) and Becker, Tiedemann & Tiedemann (1959).

Dynamic Alarm Systems for Hospitals (D.A.S.H.)

2018 ◽  
Vol 26 (4) ◽  
pp. 14-19 ◽  
Author(s):  
Jasmine M. Greer ◽  
Kendall J. Burdick ◽  
Arman R. Chowdhury ◽  
Joseph J. Schlesinger
Keyword(s):  
Health Care ◽  
Health Care Quality ◽  
Improve Patient Safety ◽  
Environmental Noise ◽  
Care Quality ◽  
False Alarms ◽  
Alarm Fatigue ◽  
Alarm Systems ◽  
Physiological Information ◽  
Improve Patient

Hospital alarms today indicate urgent clinical need, but they are seldom “true.” False alarms are contributing to the ever-increasing issue of alarm fatigue, or desensitization, among doctors and nurses. Alarm fatigue is a high-priority health care concern because of its potential to compromise health care quality and inflict harm on patients. To address this concern, we have engineered Dynamic Alarm Systems for Hospitals (D.A.S.H.), a dynamic alarm system that self-regulates alarm loudness based on the environmental noise level and incorporates differentiable and learnable alarms. D.A.S.H., with its ability to adapt to environmental noise and encode nuanced physiological information, may improve patient safety and attenuate clinician alarm fatigue.

The Fine Structure of the Eye of the Leech, Helobdella Stagnalis

1967 ◽  
Vol 2 (3) ◽  
pp. 341-348
Author(s):  
A. W. CLARK
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Photoreceptor Cell ◽  
Receptor Cell ◽  
Pigment Cell ◽  
Cell Mass ◽  
Pigment Cells ◽  
Cell Cytoplasm ◽  
Receptor Cells ◽  
Intracellular Vesicle

The eye of the rhynchobdellid leech, Helobdella stagnalis, has been examined with the electron microscope. The eye is composed of a cup of pigment cells surrounding a compact mass of photo-receptor cells. In addition to pigment granules, the pigment-cell cytoplasm is characterized by mitochondria, a Golgi complex, and profiles of rough-surfaced endoplasmic reticulum. The photoreceptor cell contains a microvillous rhabdomere. The microvilli arise from the membrane of a large intracellular vesicle and obliterate much of its lumen. No connexion between the lumen of the intracellular vesicle and the extracellular space has been observed. The plasmalemma of the photoreceptor cell is folded to form thin pleats of cytoplasm which separate adjacent receptor cells from each other. No glial-like cells have been seen in the receptor cell mass. Directly subjacent to the microvilli and surrounding the intracellular vesicle is a tortuous and predominantly smooth-surfaced endoplasmic reticulum. A pair of centrioles is found near the rhabdomere. The cytoplasm around the nucleus is characterized by smooth- and rough-surfaced elements of endoplasmic reticulum, many mitochondria, and a Golgi complex. Proximally, the receptor cell narrows to form a nerve fibre which joins those from other cells to form the optic nerve.

scholarly journals Studies on microperoxisomes. VII. Pigment epithelial cells and other cell types in the retina of rodents.

1975 ◽  
Vol 65 (2) ◽  
pp. 324-334 ◽  
Author(s):  
P M Leuenberger ◽  
A B Novikoff
Keyword(s):  
Epithelial Cells ◽  
Vascular Endothelial Cells ◽  
Smooth Endoplasmic Reticulum ◽  
Photoreceptor Cells ◽  
Cell Types ◽  
Vascular Endothelial ◽  
Pigment Epithelial ◽  
Large Numbers ◽  
And Storage ◽  
Pigment Epithelial Cells

The pigment epithelial cell of the retina actively participates in two aspects of lipid metabolism: (a) the fatty acid esterification of vitamin A and its storage and transport to the photoreceptors, and (b) the phagocytosis and degradation of the lipoprotein membrane disks shed from the photoreceptor cells. Study of the pigment epithelial cells of adult albino and pigmented rodents has revealed the abundance of an organelle, microperoxisomes, not previously known to exist in this cell type. The metabolism, transport, and storage of lipids are major functions of other cell types which possess large numbers of microperoxisomes associated with a highly developed smooth endoplasmic reticulum. Microperoxisomes were encountered, but relatively rarely, in Müller cells and vascular endothelial cells. A tubular system in photoreceptor terminals is reactive in the cytochemical procedure used to visualize microperoxisomes.

Study on Sensors Used in Security and Alarm Systems for Buildings

2015 ◽  
Vol 220-221 ◽  
pp. 439-444
Author(s):  
Bronius Karaliunas ◽  
Dalia Lukosiene ◽  
Vitalij Kozlovski
Keyword(s):  
Experimental Study ◽  
Support Systems ◽  
False Alarms ◽  
Tracking Systems ◽  
Alarm Systems ◽  
Electromagnetic Disturbances

Recently, a significant increase in demand for high-end offices, public and administrative buildings with the installed reliable security, alarm and automatic fire tracking systems as well as requirements for possessing operating comfortable microclimate support systems have been registered in Lithuania. The failures of such systems and false alarms tend to be rather common due to the deleterious effects of electromagnetic disturbances. Therefore, the work analyzes the reasons and causes for the disorders of the previously mentioned systems and presents the findings of the experimental study on sensors.

Intermediate filaments in the cytoskeletons of fish chromatophores

1984 ◽  
Vol 66 (1) ◽  
pp. 353-366
Author(s):  
D.B. Murphy ◽  
W.A. Grasser
Keyword(s):  
Electron Microscopy ◽  
Intermediate Filaments ◽  
Actin Filaments ◽  
Pigment Granule ◽  
Maximum Size ◽  
Pigment Cells ◽  
Air Interface ◽  
Large Numbers ◽  
Freeze Dried ◽  
Filament Networks

When fish pigment cells (melanophores, erythrophores) are lysed by a modified Kleinschmidt method on a buffer-air interface and examined by electron microscopy, large numbers of intermediate filaments are observed. The intermediate filament networks are distinct from actin and tubulin, and entrap the pigment as determined by stereo viewing of freeze-dried rotary-shadowed specimens. During lysis, under conditions that do not preserve actin filaments or microtubules, the area covered by dispersed pigment granules reaches a maximum size and remains stable for many minutes, suggesting that intermediate filaments are responsible for holding the pigment in position and preventing further cytoplasmic dispersion. These observations demonstrate that fish pigment cells contain large numbers of intermediate filaments and suggest that they may be important for coordinating pigment granule movement.

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