Light-induced and circadian changes in the compound eye of the haematophagous bug Triatoma infestans (Hemiptera: Reduviidae)

2002 ◽  
Vol 205 (2) ◽  
pp. 201-210
Author(s):  
Carolina E. Reisenman ◽  
Teresita C. Insausti ◽  
Claudio R. Lazzari
Keyword(s):  
Compound Eye ◽  
Proximal Region ◽  
Triatoma Infestans ◽  
Pigment Cells ◽  
Constant Darkness ◽  
Light Conditions ◽  
Dynamic Changes ◽  
Circadian Oscillators ◽  
Direct Light ◽  
Open Rhabdom

SUMMARY We analysed dynamic changes in the ommatidial structure of the compound eyes of Triatoma infestans. This nocturnal insect possesses open-rhabdom eyes, in which a ring of six rhabdomeres from retinula cells 1–6 (R1–6) surrounds a central pair of rhabdomeres from retinula cells 7 and 8 (R7–8). Screening pigments are located in all the photoreceptors and in the primary (PPC) and secondary (SPC) pigment cells. During the day, pigments within R1–6 and the PPCs form a small ‘pupil’ above the rhabdom and pigments within R7–8 are clustered around the central rhabdomere, allowing light to reach only the central rhabdomere. At night, the ‘pupil’ widens, and pigments inside R7–8 concentrate in the proximal region of the cells, allowing light to reach the peripheral rhabdomeres. In addition, the distance between the cornea and the rhabdom decreases. These rhythmic changes adapt the sensitivity of the eye by controlling the amount of light reaching and travelling within the rhabdom. Furthermore, the rhythm persists under conditions of constant darkness (DD), i.e. it is controlled by an endogenous oscillator. Remarkably, there are differences in pigment movements between the retinula cells of a single ommatidium. The migration of pigments in R1–6 is regulated by a circadian input, while that in R7–8 is regulated by both direct light and circadian inputs. The rhythm vanishes under constant-light conditions (LL). In this species, the circadian rhythm of photonegative behaviour persists in both DD and LL conditions, suggesting that these two rhythms, in retinal morphology and visual behaviour, may be generated by different circadian oscillators.

Localization of the clock controlling circadian rhythms in the first neuropile of the optic lobe in the housefly

2001 ◽  
Vol 204 (19) ◽  
pp. 3303-3310
Author(s):  
Monika Bałys ◽  
Elżbieta Pyza
Keyword(s):  
Circadian Rhythms ◽  
Musca Domestica ◽  
Compound Eye ◽  
Optic Lobe ◽  
Continuous Light ◽  
Constant Darkness ◽  
Cross Sectional ◽  
Circadian Oscillators ◽  
L1 And L2 ◽  
The Brain

SUMMARYThe visual system of a fly expresses several circadian rhythms that have been detected in the photoreceptors of the compound eye and in the first neuropile, the lamina, of the underlying optic lobe. In the lamina, axons of two classes of interneuron, L1 and L2, exhibit cyclical size changes, swelling by day and shrinking by night. These rhythmic size changes may be generated by circadian oscillators located inside and/or outside the optic lobe. To localize such oscillators, we have examined changes in the axonal cross-sectional areas of L1 and L2 within the lamina of the housefly (Musca domestica) under conditions of 12 h of light and 12 h of darkness (LD12:12), constant darkness (DD) or continuous light (LL) 24 h after the medulla was severed from the rest of the brain. After the lesion, the axon size changes of L1 and L2 were maintained only in LD conditions, but were weaker than in control flies. In DD and LL conditions, they were eliminated. This indicates that circadian rhythms in the lamina of a fly are generated central to the lamina and medulla neuropiles of the optic lobe. Cyclical changes of light and darkness in LD conditions are still able, however, to induce a weak daily rhythm in the axon sizes of L1 and L2.

Fine structure of the compound eye of the black fly Simulium vittatum (Diptera: Simuliidae)

1987 ◽  
Vol 65 (6) ◽  
pp. 1454-1469 ◽  
Author(s):  
Gail E. O'Grady ◽  
Susan B. McIver
Keyword(s):  
Fine Structure ◽  
Compound Eye ◽  
Sensory Receptor ◽  
Dorsal Region ◽  
Male And Female ◽  
Simulium Vittatum ◽  
Transmission Electron ◽  
Accessory Pigment ◽  
Open Rhabdom ◽  
Retinular Cells

The fine structure of the ommatidia in light- and dark-adapted eyes of male and female Simulium vittatum Zetterstedt was investigated using scanning and transmission electron microscopy. The male eye is divided into distinct dorsal and ventral regions. The facets in the dorsal region are approximately two times larger than those in the ventral one, which are similar in size to the ones in the female eye. All ommatidia of S. vittatum examined consist of two general regions: a distal dioptric apparatus with bordering primary and accessory pigment and Semper cells, and a sensory receptor layer. Each ommatidium in the female eye and ventral eye of the male has eight retinular cells (R cells): six peripheral (R1–6) and two central (R7, R8). R7 occurs distally and R8 basally. Strikingly, the ommatidia in the dorsal eye of the male lack the R7 cell. In all ommatidia, rhabdomeres on the inner surface of the peripheral R cells are separate throughout their length, creating an open rhabdom. A greater diameter of corneal facets, elongated peripheral R cells, and perhaps the lack of the R7 cell are specializations of the dorsal region of the eye that help the male to detect small, rapidly moving females against the skylight as they fly above the swarm of males. Differences observed between light- and dark-adapted eyes of male and female S. vittatum were the same and were associated with the internal components of the peripheral R cells.

A Peculiar Kind of Pigment Cell in the Compound Eye of Lepisma saccharina L. (Thysanura)

1973 ◽  
Vol 4 (2) ◽  
pp. 87-90 ◽  
Author(s):  
Rolf Elofsson
Keyword(s):  
Basal Lamina ◽  
Light Microscope ◽  
Compound Eye ◽  
Pigment Cell ◽  
Pigment Cells ◽  
Pigment Granules ◽  
A Cell ◽  
Lepisma Saccharina

AbstractThe ultrastructure of the primary pigment cells of the compound eye of Lepisma saccharina is described. The cells are four in number. The pigment granules are contained in fingerlike protrusions from the pigment cells. These protrusions project into the enlarged basal lamina surrounding the ommatidial top. The large basal lamina could have given the impression of a cell (called corneagen) in the light microscope.

The morphology of the dorsal eye of the hydrothermal vent shrimp, Rimicaris exoculata

1995 ◽  
Vol 12 (5) ◽  
pp. 861-875 ◽  
Author(s):  
Patrick J. O'Neill ◽  
Robert N. Jinks ◽  
Erik D. Herzog ◽  
Barbara-Anne Battelle ◽  
Leonard Kass ◽  
...  
Keyword(s):  
Hydrothermal Vent ◽  
Hydrothermal Vents ◽  
Compound Eye ◽  
Thick Layer ◽  
Dorsal Surface ◽  
Volume Density ◽  
Pigment Cells ◽  
Body Volume ◽  
Rimicaris Exoculata ◽  
Screening Pigment

AbstractThe bresiliid shrimp, Rimicaris exoculata, lives in large masses on the sides of hydrothermal vent chimneys at two sites on the Mid-Atlantic Ridge. Although essentially no daylight penetrates to depths of 3500 m, very dim light is emitted from the hydrothermal vents themselves. To exploit this light, R. exoculata has evolved a modified compound eye on its dorsal surface that occupies about 0.5% of the animal's body volume. The eye's morphology suggests that it is extremely sensitive to light. The cornea of the dorsal eye is smooth with no dioptric apparatus. The retina consists of two wing-shaped lobes that are fused across the midline anteriorly. The rhabdomeral segments of the 7000 ommatidia form a compact layer of photosensitive membrane with an entrance aperture of more than 26 mm2. Within this layer, the volume density of rhabdom is more than 70%. Below the rhabdomeral segments, a thick layer of white diffusing cells scatters light upward into the photoreceptors. The arhabdomeral segments of the five to seven photoreceptors of each ommatidium are mere strands of cytoplasm that expand to accommodate the photoreceptor nuclei. The rhabdom is comprised of well-organized arrays of microvilli, each with a cytoskeletal core. The rhabdomeral segment cytoplasm contains mitochondria, but little else. The perikaryon contains a band of mitochondria, but has only small amounts of endoplasmic reticulum. There is no ultrastructural indication of photosensitive membrane cycling in these photoreceptors. Vestigial screening pigment cells and screening pigment granules within the photoreceptors are both restricted to the inner surface of the layer of the white diffusing cells. Below the retina, photoreceptor axons converge in a fan-shaped array to enter the dorsal surface of the brain. The eye's size and structure are consistent with a role for vision in shrimp living at abyssal hydrothermal vents.

scholarly journals Photoperiod-Induced Neuroplasticity in the Circadian System

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Alessandra Porcu ◽  
Malini Riddle ◽  
Davide Dulcis ◽  
David K. Welsh
Keyword(s):  
Seasonal Changes ◽  
Phase Distribution ◽  
Light Exposure ◽  
Brain Regions ◽  
Day Length ◽  
Light Conditions ◽  
Seasonal Adaptation ◽  
Circadian Oscillators ◽  
Plastic Changes ◽  
Mood And Cognition

Seasonal changes in light exposure have profound effects on behavioral and physiological functions in many species, including effects on mood and cognitive function in humans. The mammalian brain’s master circadian clock, the suprachiasmatic nucleus (SCN), transmits information about external light conditions to other brain regions, including some implicated in mood and cognition. Although the detailed mechanisms are not yet known, the SCN undergoes highly plastic changes at the cellular and network levels under different light conditions. We therefore propose that the SCN may be an essential mediator of the effects of seasonal changes of day length on mental health. In this review, we explore various forms of neuroplasticity that occur in the SCN and other brain regions to facilitate seasonal adaptation, particularly altered phase distribution of cellular circadian oscillators in the SCN and changes in hypothalamic neurotransmitter expression.

Analysis of period mRNA cycling in Drosophila head and body tissues indicates that body oscillators behave differently from head oscillators

1994 ◽  
Vol 14 (11) ◽  
pp. 7211-7218
Author(s):  
P E Hardin
Keyword(s):  
Locomotor Activity ◽  
Feedback Loop ◽  
Constant Darkness ◽  
Circadian Pacemaker ◽  
Circadian Oscillators ◽  
Body Tissues ◽  
Pacemaker Function ◽  
Neuronal Tissues ◽  
Per Gene

The period (per) gene is thought to be part of the Drosophila circadian pacemaker. The circadian fluctuations in per RNA and protein that constitute the per feedback loop appear to be required for pacemaker function, and have been measured in head neuronal tissues that are necessary for locomotor activity and eclosion rhythms. The per gene is also expressed in a number of neuronal and nonneuronal body tissues for which no known circadian phenomena have been described. To determine whether per might affect some circadian function in these body tissues, per RNA cycling was examined. These studies show that per RNA cycles in the same phase and amplitude in head and body tissues during light-dark cycles. One exception to this is the lack of per RNA cycling in the ovary, which also appears to be the only tissue in which PER protein is primarily cytoplasmic. In constant darkness, however, the amplitude of per RNA cycling dampens much more quickly in bodies than in heads. Taken together, these results indicate that circadian oscillators are present in head and body tissues in which PER protein is nuclear and that these oscillators behave differently.

scholarly journals INFLUENCE OF LIGHT ON THE GROWTH AND MALIGNANCY OF A TRANSPLANTABLE NEOPLASM OF THE RABBIT

1927 ◽  
Vol 45 (3) ◽  
pp. 483-496 ◽  
Author(s):  
Louise Pearce ◽  
C. M. Van Allen
Keyword(s):  
Experimental Evidence ◽  
Malignant Disease ◽  
External Factor ◽  
Continuous Light ◽  
Ultra Violet ◽  
The Other ◽  
Constant Light ◽  
Constant Darkness ◽  
Light Conditions ◽  
The One

An experiment is reported in which an environment of constant and continuous light excluding the shorter ultra-violet rays, and one of constant darkness, have influenced the course and character of a malignant disease of rabbits induced by a transplantable neoplasm. Under the influence of constant light the level of malignancy was observed to be low; under the influence of constant darkness the level of malignancy was somewhat lower than in the control animals living under ordinary indoor light conditions, but the level was not as low as among the animals constantly illuminated. These observations furnish experimental evidence in support of the idea that there is a correlation between the external factor of light on the one hand and the manifestations of an experimental malignant disease on the other.

Dissociation of motor activity circadian rhythm in rats after exposure to LD cycles of 4-h period

1997 ◽  
Vol 272 (1) ◽  
pp. R95-R102 ◽  
Author(s):  
J. Vilaplana ◽  
T. Cambras ◽  
A. Diez-Noguera
Keyword(s):  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Constant Light ◽  
Constant Darkness ◽  
Circadian Oscillators ◽  
Entrainment Process ◽  
Free Running ◽  
Anticipatory Activity ◽  
Degree Of Coupling

For > 30 days Wistar rats were subjected to six dark pulses per day (T4 cycles; 3 h light, 1 h dark) to study the possibility of dissociating their motor activity rhythm into distinct circadian components. Rats of both sexes were used, one-half of which were pinealectomized to examine the effect of the pineal gland on the entrainment process. Results show that when rats were maintained under T4 a 4-h rhythm in their motor activity was present. Rats showed anticipatory activity to dark phases, suggesting that the motor activity components are actually entrained to the external light/dark (LD) cycles. When rats were left under constant darkness after T4, some motor activity components coming from the dark phases free ran for several days with different circadian periods. This suggests that the motor activity pattern is generated by several circadian oscillators. Moreover, the free-running components of motor activity after T4 were more evident when T4 was applied after exposure to constant light than after exposure to constant darkness. These results support the hypothesis that the circadian system of the rat is formed by several circadian oscillators, whose degree of coupling depends on light conditions. In constant light, bright light may inhibit internal coupling within the system, making it subsequently more susceptible to the T4 cycles. No differences were observed between pinealectomized and sham-operated animals, although females were more sensitive to T4 cycles than males.

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