Serotonin or electrical optic nerve stimulation increases the photosensitivity of the Aplysia eye

• 1.1. Exposure of isolated Aplysia eyes to serotonin (10⁻⁷ M) produces large and long-lasting (hours) increases in the ERG recorded from the surface of the eye.
• 2.2. Dopamine, octopamine, or acetylcholine do not mimic the effect of 5-HT on the ERG.
• 3.3. Brief electrical optic nerve stimulation (2 Hz, 2 min) also increases the ERG and this effect also lasts a long period of time (0.5–2 hr).
• 4.4. Our results suggest that serotonin increases the response of photoreceptor cells to light and that efferent optic nerve activity may modulate photosensitivity through release of serotonin in the eye.

     

Effects of efferent activity on entrainment of the Aplysia eye

• 1.1. The effects of efferent optic nerve activity on the speed of entrainment of the ocular oscillators in Aplysia were investigated by severing one optic nerve in 21 animals and evaluating reentrainment rates to a light cycle phase advanced 10hr in relation to a prior light schedule.
• 2.2. Reentrainment to this phase advanced light cycle was essentially complete in both the intact and denervated eyes within 3 days; and there was no indication that the time course of entrainment was significantly different in the two eyes.
• 3.3. The phase angle of the rhythm of neurally isolated eyes, however, consistently phase led the intact eyes by approx 1 hr. Thus, the results indicate that while efferent activity does not significantly effect the speed of entrainment, it appears to influence steady-state phase angle.

     

Effect of polarized light on the ERG circadian rhythm in crayfish

• 1.1. Crayfish subjected to constant darkness and temperature displayed an electroretinographic circadian rhythm with both non-polarized and polarized light stimuli.
• 2.2. In the ERG circadian rhythm associated with polarized light there was an observed reduction in period and increment in both amplitude and activity: rest ratio.
• 3.3. The change from non-polarized to polarized light also produced phase advances or delays in the ERG circadian rhythm depending on the circadian time when the change was introduced.
• 4.4. Separate recording of HI and HII ERG components showed that HII is always less conspicuous and more easily saturable than HI circadian rhythm.
• 5.5. These results support that: (a) the detection of polarized light contributes to extend the differences between night and day; (b) the two structures involved in the generation of HI and HII ERG components, i.e. the rhabdom and the retinular cell, operate as two independent elements of the circadian system responsible of ERG circadian rhythm.

     

Erg circadian rhythm in the course of ontogeny in crayfish

• 1.1. The objective of the present work was to study the ontogeny of the ERG circadian rhythm in crayfish.
• 2.2. Long-term recordings of ERG and shielding retinal pigments position measured from the instar, the second instar, the third instar and the adult crayfish were obtained.
• 3.3. In the youngest animals (1–8 days old) an ultradian rhythm (15min-4hr periods) in the ERG amplitude was detected.
• 4.4. Older animals showed a progressive increment in the period length before they exhibited a circadian pattern. This last appeared, the first time, in 30-day-old animals and showed noticeable differences in the adult crayfish. At the same time, the crayfish began to show photomotor reflex. Later on (140-day-old crayfish) the circadian rhythm attained its final parameters.
• 5.5. The SD was used as a measure of lability in periods. The 4 hr ultradian rhythm and the 22.4 hr circadian rhythm showed the lowest SD indicating that they are the most precise period values.
• 6.6. Our results support the idea that the ERG circadian rhythm results from the coupling among high frequency (ultradian) oscillators, particularly those of 4 hr periods and that the coupling depends on the action of neurosecretions released from the sinus gland.

     

The development of thermoregulation in the marsupial brushtail possum Trichosurus vulpecula

• 1.1. The adult possums showed a circadian rhythm of body temperature with a peak in temperature around midnight and a nadir at noon.
• 2.2. The young possum within the pouch displayed a circadian rhythm with the highest temperatures during the day and the lowest in the early evening.
• 3.3. Although the body temperature of the young possum exceeded that of the mother occasionally, for the major part of the 24 hr the body temperature of the young was lower than that of the mother.
• 4.4. The young possum could maintain a steady body temperature between 140 and 167 days post partum. A circadian rhythm of temperature was observed between 157–190 days post partum.
• 5.5. All adipose tissue examined with the light and electron microscope had the morphology of white adipose tissue.

     

Ontogeny of a circadian rhythm in the glycaemic response of Gallus domesticus to glucagon

• 1.1. A circadian rhythm in the glucagon-mediated glycogenolytic response was absent in the newly-hatched chick but was present in the bird aged 1 week.
• 2.2. The peak glucose concentration was 38% higher in the afternoon in 1-week-old birds and 50% in 2-week-old birds.
• 3.3. The circadian rhythm was not present in 1-week-old birds subjected to constant illumination from hatching.
• 4.4. Starving the bird reduced the response to glucagon, irrespective of the time of day.

     

Melatonin: A coupling device between oscillators in the circadian system of the ruin lizard Podarcis sicula

• 1.1. Chronic administration of melatonin (in silastic capsules) lengthened the free-running period of the locomotor rhythm and shortened the circadian activity time in Podarcis sicula held in constant temperature and darkness.
• 2.2. Lizards displaying a bimodal pattern of activity invariably became unimodal after melatonin administration.
• 3.3. The results support the hypothesis that melatonin acts as a coupling device between circadian oscillators driving the locomotor rhythm in Podarcis sicula.

     

Circadian organization in white suckers Catostomus commersoni: The role of the pineal organ

• 1.1. Pinealectomy of the white sucker, Catostomus commersoni, had significant effects on the free-running circadian rhythm of locomotor activity. With fish kept under constant darkness pinealectomy resulted in a significant alteration in period length and decrease in the precision of circadian activity.
• 2.2. In a number of cases circadian activity was split into two components that free-ran independently.
• 3.3. The pineal organ is suggested to function in the coupling of a multi-oscillator system making up circadian organization in this fish.

     

Synchrony of dolphin eye movements and their power density spectra

• 1.1. In the laboratory, eye movements in the horizontal and vertical planes of a normal human and two adult dolphins, Tursiops truncatus, were analyzed and compared. Several of the visual conditions included structured, unstructured and moving stimulus fields.
• 2.2. Power spectral density analyses of the dolphin eye movements showed maximal power around 0.1 Hz, lower than the human counterpart.
• 3.3. Coefficients of determination (r²) and correlation coefficients (r) derived from autocorrelation and crosscorrelation of dolphin eye signals produced typically small values scattered randomly around zero.
• 4.4. From 51,200 correlations, the greatest r² value indicated that movements of one dolphin eye predict no more than 30% of the movement variance of the fellow eye.
• 5.5. Although dolphin eyes are mobile at lower fundamental frequencies than in humans, there is a low level of synchrony between the two eyes.

     

Differences in temperature sensitivity of the orcadian systems of homoiothermic and heterothermic neotropical bats

• 1.Comparative studies of two neotropical chiropteran species—one homoiothermic (Phyllostomus discolor, Phyllostomidae) and one heterothermic (Molossus ater, Molossidae)—show that their activity rhythms are differently affected by the ambient temperature (AT).
• 2.1. Whereas the period of the free-running circadian rhythm of Molossus at 20°C.is much different from that at 30°C, and is positively correlated with AT (Fig. 2), no temperature-dependent changes in the period of Phyltostomus were observed (Fig. 4).
• 3.2. Correspondingly, trapezoidal temperature cycles 10°C in amplitude do not entrain the free-running rhythm of the homoiothermic bat, whereas they act as a Zeitgeber for Molossus ater. Even forM. ater, however, the Zeitgeber strength of such temperature cycles is relatively slight.
• 4.3. These results are inconsistent with a hypothesis of Bünning (1977) concerning the phylogenetic adaptation of temperature sensitivity of circadian rhythms of warm-blooded animals. They are consistent both with the hypothesis that heterothermic species in general have circadian systems with appreciable temperature sensitivity, and with the proposal that the more plastic circadian systems are in general more strongly influenced by AT than rigid systems.

     

Analysis of the circadian rhythm in energy metabolism of rat liver

• 1.1. To study the temporal organization of energy metabolism in rat liver the steady state concentrations of key intermediates of carbohydrate and phosphorus metabolism were determined during 24 hr.
• 2.2. The circadian rhythm in energy metabolism of rat liver has been analysed by four different approaches. It was shown that neither apparent PEP synthesis nor crossover theorem were acceptable for the elucidation of the temporal organization of multi-enzyme systems.
• 3.3. Correlations analysis explained the temporal organization of energy metabolism most satisfactorily.
• 4.4. Based on the results of this analysis it was suggested that circadian regulation of energy metabolism in liver was realized at the level of the citric acid cycle.

     

Analysis of postembryonic development of locomotor activity rhythm by corpora allata implantation in the cricket gryllus bimaculatus

• 1.1. Male crickets Gryllus bimaculatus show a drastic change in circadian rhythm from nymphal diurnality to adult nocturnality, in association with an increase in activity level several days after the imaginai moult.
• 2.2. The corpora allata implantation into male 7th or 8th instar nymphs produced supernumerary instar nymphs in about 30% of the implanted animals, but did not affected the normal development in the remaining animals.
• 3.3. The majority of the supernumerary instar nymphs were diurnal and sexually inactive, although their internal reproductive organs appeared to be fully mature.
• 4.4. The supernumerary instar nymphs became nocturnal with an increase in activity level several days after the imaginai (9th) moult.
• 5.5. The roles of the nervous system in the regulation of the rhythm reversal are discussed.

     

Morphological and electrophysiological characteristics of a dorsal unpaired median neuron of the cricket,Acheta domesticus

• 1.1. The dorsal unpaired median neuron (DUMDL) of the metathoracic dorsal longitudinal flight muscle was studied using cobalt and neutral red staining, various pharmacological agents and extracellular recording of electrical activity.
• 2.2. The soma of DUMDL is posterior in the group of dorsal unpaired median neurons of the metathoracic ganglion; DUMDL does not degenerate following histolysis of its muscle.
• 3.3. Slow, regular spontaneous activity of DUMDL is generated in the isolated metathoracic ganglion and is suppressed following stimulation of DUMDL and by discharges of the flight motor neurons. This spontaneous activity is increased by acetylcholine and eserine and blocked by anticholinesterase agents.
• 4.4. The neurite of DUMDL appears to have several impulse initiation zones characterized by a low safety factor.

     

Effect of eyestalk ablation on oxygen consumption of callinectes similis exposed to salinity changes

• 1.1. The effect of eyestalk ablation on preadults of Callinectes similis exposed to a constant salinity (30%.) and to simulated tidal changes in salinity (30-11 to 30%.) were measured.
• 2.2. In constant salinity, crabs showed a persistent respiratory rhythm, with a maximum oxygen consumption during the day. Under these conditions, ablation significantly increased the respiratory rate but not the rhythm.
• 3.3. In variable salinities, the highest respiratory rates occurred in salinities of 11 and 16%. during the night. In these crabs, ablation of eyestalks and subsequent injection of eyestalk extracts did not alter the respiration rate rhythm.
• 4.4. The circadian rhythm is controlled by the periodicity of environmental changes instead of the influence of eyestalk hormones.
• 5.5. Regulation of metabolism in C. similis associated with osmoregulation involves other neurosecretory organs.

     

Superposition and scattering of visual fields in a compound,double eye—II. Stimulation sequences for different distances in a stomatopod from a bright habitat

• 1.1. The inputs deriving from a point light moving in front of a column of ommatidia are plotted by a computer.
• 2.2. Overlap of visual fields causes one main, central maximum surrounded by smaller maxima intercalated by minima.
• 3.3. With increasing distance of the point from the eye the central maximum increases.
• 4.4. Ommatidia in each half of the eye are stimulated sequentially in two groups. Stimulation sequences are parallel between the two halves of the eye.
• 5.5. We postulate an integrative mechanism for processing the succession of simultaneous inputs and hypothesize that the animal derives information about speed and distance from that mechanism.

     

A study of visual pigments in the two antarctic crustaceans Orchomene plebs (Amphipoda) and Glyptonotus antarcticus (Isopoda)

• 1.1. Total chromophore contents as well as the contributions made by 11-cis retinal were determined by high pressure liquid chromatography in light- and dark-adapted eyes of Orchomene plebs and Glyptonotus antarcticus (Amphipoda and Isopoda, respectively).
• 2.2. In O. plebs the highest amount of total chromophore in pmol/eye was found to be 18.5 in 36 hr dark-adapted animals. The lowest amount (11.6 pmol/eye) was recorded in 24 hr light-adapted individuals.
• 3.3. In dark-adapted O. plebs, irrespective of whether dark-adapted for 36 or 60 hr, the percentage of 11-cis retinal was maximally 96.6%. In the light-adapted material it reached 71.2%
• 4.4. In eyes of 20 hr dark-adapted Glyptonotous antarcticus, possibly because of insufficient dark adaptation, a total chromophore content of only 3.2 pmol/eye was found. The percentage of 11-cis retinal was 55.8.
• 5.5. Porphyropsin with its testable 3-dehydroretinal (vitamin A₂-aldehyde) was not encountered in any of our samples.
• 6.6. Calculations of photopigment per gram body weight and a comparison with data from freshwater crayfish show that dark-adapted O. plebs possess approximately 20 times the relative photopigment amount of the crayfish. Absolute sensitivity of the eye of O. plebs is, therefore, expected to be very high.

     

Detection of substrate vibrations by salamanders: Frequency sensitivity of the ear

• 1.1. The sensitivity of salamander ears varies with the frequency of substrate vibration.
• 2.2. The saccule is sensitive to vibrations (20–450 Hz) and appears to perform as a simple harmonic oscillator undergoing forced resonance.
• 3.3. Saccular sensitivity appears related to the normal environment occupied by the salamander, with that of an aquatic animal being more sensitive at low frequencies than that of a terrestrial animal.
• 4.4. Prostrate adult N. viridescens can use the middle ear to transmit vibrations to the inner ear.

     

Laboratory studies on the oxygen consumption of the marine teleost,Lichia amia (Linnaeus, 1758)

• 1.1. The oxygen consumption of the marine teleost, Lichia amia was investigated under controlled laboratory conditions.
• 2.2. The routine oxygen consumption showed a strong circadian rhythm with the fish being mainly active during the light period.
• 3.3. The specific mass exponent (dimension: μg O₂/g/hr) is temperature independent and ranges from 0.27–0.29.
• 4.4. Starving the fish results in a mean decrease in active, routine and standard oxygen consumption of 21%, 24% and 20%, respectively.
• 5.5. Feecling led to an increase in the oxygen consumption of the teleosts, with the mean metabolic rate over the 24 hr that followed, being 58% and 50% higher for fish that had been starved for 162hr and 40 hr, respectively.
• 6.6. Apparent SDA showed some variation and ranged from 6.0 to 35.5%.
• 7.7. The results obtained are generally in agreement with those recorded for other teleosts.

     

Is the orcadian clock of gonyaulax held stationary after a strong pulse of anisomycin?

• 1.1. Gonyaulax polyedra cells were treated with two sequential pulses of a protein synthesis inhibitor (anisomycin) in order to analyse a possible stopping of the circadian clock by the first pulse.
• 2.2. Inhibition of protein synthesis during these pulses and after centrifugation and resuspension of the cells was determined by measuring the incorporation of labelled amino acids.
• 3.3. The effects of the second pulses on the clock were measured as phase shifts of the glow rhythm with respect to a control rhythm that had been subjected to the initial pulse only.
• 4.4. From the observed phase shifts of the second pulses we conclude that the clock is not stopped by the first pulse but is immediately shifted to a different phase.

     

Optical and neural pooling in visual processing in crustacea

• 1.1. Optical pooling is common in crustacean vision, both pooling in the single ommatidium and pooling inputs from many ommatidia by overlapping visual fields.
• 2.2. Optical and neural pooling work together subdividing the eye into different surface regions with different tasks.
• 3.3. Small-fiber and large-fiber systems with corresponding small and large dendritic branching provide a parallel processing system.
• 4.4. Several parallel, integrating channels process that visual information which is needed for high-speed reactions.
• 5.5. Visual fibers receive contributions from other modality inputs like vibration, olfaction or attention neurons. Inputs from mechanoreceptors transmitted over integrating fibers seem to join the signals in the intergrating visual fibers.
• 6.6. The signal for a particular channel is expressed by the pattern of spikes (rather than changes in the mean frequency of spikes) which is modulated by any input variation.
• 7.7. A particular discharge pattern may then be recognized by a command neuron or a muscle ensemble.