The circadian locomotor rhythm of Hemideina thoracica (Orthoptera; Stenopelmatidae): the circadian clock as a population of interacting oscillators

ABSTRACT. The behaviour of the circadian locomotor rhythm of the New Zealand weta, Hemideina thoracica (White), supports the model that the underlying pacemaker consists of a population of weakly coupled oscillators. Certain patterns of locomotor activity, previously demonstrated almost exclusively in vertebrates, are presented here as evidence for the above hypothesis. They include after-effects of various pre-treatments, rhythm-splitting and spontaneous changes in the rhythm. After-effects, which describe the unstable behaviour of free-running circadian rhythms following particular experimental perturbations, have been observed in Hemideina following single light pulses, constant dim light, and laboratory and natural entrainment. Period changes occurred in the activity rhythm after single light pulses of 8-h and 12-h duration (25 lx). Constant dim light (0.1 lx) increased the free-running period (τ) of the activity rhythm, but the after-effect of constant dim light was either an increase or a decrease in τ. After-effects upon both τ and the active phase length of the activity rhythm were found following non-24-h light entrainment cycles with 8-h and 12-h light phases of 25 lx. Qualitative measurements of these after-effects upon τ are presented which reveal a relationship between both the direction and amount of change in τ, and the difference between entrainment cycle length (T) and pre-entrainment free-running period. The after-effect of natural entrainment was an initial short-period free-run (τ < 24h) lasting 5–10 days, generally followed by a rapid period lengthening to τ= 25–26 h. Support for the population model was provided by spontaneous dampening, recovery, and period changes of the rhythm, together with the disruption of the active phase following critical light perturbations, and rhythm-splitting. These Hemideina results are compared with the simulations of the Coupled Stochastic System of Enright (1980).     

Changes in circadian parameters of humbug damselfish,Dascyllus aruanus according to lunar phase shifts in Micronesia

The objectives of this study were to test the nighttime effects of the lunar phase on circadian rhythm in the humbug damselfish, Dascyllus aruanus. We measured moonlight intensities at eight different phases across the lunar cycle. At each lunar phase, the circadian rhythm was evaluated by measuring the clock genes cryptochrome 1 and period 2. In addition, we measured arylalkylamine N-acetyltransferase 2 (AANAT2), melatonin and melatonin receptor 1 (MT-R1). The moonlight intensity was highest at full moon and lowest during the waning crescent. Clock gene expression was highest during the full moon compared to the other phases. By contrast, the plasma concentrations of AANAT2 and melatonin and the MT-R1 mRNA expression were highest during the full moon phase. Our results suggest that moonlight affects circadian rhythm patterns in the humbug damselfish. There is a need to investigate potential other physiological effects of lunar phase shifts.     

The development of circadian rhythm of human body temperature

Abstract

Daily periodic changes of body temperature were examined in 138 subjects ranging in age between 5 days and 44 years. Whereas the circadian rhythm of human body temperature was not discerned in newborn babies, body temperatures were higher during daytime than during nighttime in infants over one month. Temperature rhythm similar to that of adults, with respect to phase, was observed in the age groups of ten to eleven months and over, earlier than previously reported. The amplitude in circadian oscillation was, however, significantly larger in children between 7 months and 7 years of age than in adults. Thus, it is concluded that the adult type of circadian rhythm of human body temperature is fully established with respect to phase and amplitude after 7 years of age.     

Evidence of a diurnal rhythm in implicit reward learning

Many aspects of hedonic behavior, including self-administration of natural and drug rewards, as well as human positive affect, follow a diurnal cycle that peaks during the species-specific active period. This variation has been linked to circadian modulation of the mesolimbic dopamine system, and is hypothesized to serve an adaptive function by driving an organism to engage with the environment during times where the opportunity for obtaining rewards is high. However, relatively little is known about whether more complex facets of hedonic behavior – in particular, reward learning – follow the same diurnal cycle. The current study aimed to address this gap by examining evidence for diurnal variation in reward learning on a well-validated probabilistic reward learning task (PRT). PRT data from a large normative sample (N = 516) of non-clinical individuals, recruited across eight studies, were examined for the current study. The PRT uses an asymmetrical reinforcement ratio to induce a behavioral response bias, and reward learning was operationalized as the strength of this response bias across blocks of the task. Results revealed significant diurnal variation in reward learning, however in contrast to patterns previously observed in other aspects of hedonic behavior, reward learning was lowest in the middle of the day. Although a diurnal pattern was also observed on a measure of more general task performance (discriminability), this did not account for the variation observed in reward learning. Taken together, these findings point to a distinct diurnal pattern in reward learning that differs from that observed in other aspects of hedonic behavior. The results of this study have important implications for our understanding of clinical disorders characterized by both circadian and reward learning disturbances, and future research is needed to confirm whether this diurnal variation has a truly circadian origin.     

Psychophysical measure of visual luminance contrast during a daily rhythm

ABSTRACT

This study evaluated visual sensitivity to luminance contrast during a daily period. Twenty-eight young male adults (M = 24.85; SD = 2.4) with normal color vision and 20/20 visual acuity participated in this study. The circadian pattern was assessed using the Karolinska Sleepiness Scale (KSS), the Pittsburgh Sleep Quality Index (PSQI), and a sleep diary. To measure the luminance contrast, we used version 11.0 of the Metropsis software with sine-element frequency stimuli for spatial frequencies of 0.2, 0.6, 1, 3.1, 6.1, 8.8, 13.2, and 15.6 cycles per degree of visual angle (cpd). The stimuli were presented on a 19-inch color cathode ray tube (CRT) video monitor with a resolution of 1024 × 786 pixels, an update rate of 100 Hz, and a photopic luminance of 39.6 cd/m2. There was a significant difference in KSS on the weekdays [χ2₍₂₎ = 20.27; p = .001] and in the luminance contrast for frequencies of 13.2 cpd [χ2₍₂₎ = 8.27; p = .001] and 15.6 cpd [χ2₍₂₎ = 13.72; p = .041]. The results showed greater stability of the measurement during the afternoon and a reduction in the visual sensitivity in the high spatial frequencies during the night.     

Daily rhythms of locomotor activity and the influence of a light and dark cycle on gut microbiota species in tambaqui (Colossoma macropomum)

This study aimed to assess the daily rhythms of locomotor activity and to quantify bacteria populations in the tambaqui digestive tract during light and dark periods. Photoelectric cells and a recording computational system were used to quantify the locomotor activity, and the existing Gram-positive and Gram-negative bacteria populations were evaluating during the daytime and night-time periods. The results showed a typical pattern for nocturnal locomotor activity (91%), and lower percentages of Gram-positive 6?×?10³, 24% and Gram-negative cocci (approximately 38%) were observed during the same periods compared with the diurnal period (76 and 62%, respectively). Additionally, lower percentages of Gram-positive (42%) and Gram-negative (44%) Bacillus were observed during the same periods compared with the diurnal period (29?×?10⁶ CFU/g, 58% and 23?×?10⁶ CFU/g (56%), respectively). These data should be considered when animals are subjected to high stress loads for more appropriate management strategies and collaborating with future studies of what is the best schedule to vaccinate or provide probiotics to fish.     

Lack of a circadian rhythm in the ability of the gametocytes of Plasmodium falciparum to infect Anopheles gambiae

Batches of Anopheles gambiae were fed once during the day or once or twice during the night on 12 carriers naturally infected with gametocytes of P. falciparum. No overall difference was noted in the oocyst numbers in batches of mosquitoes fed during the night as compared to the daytime.     

Lighting requirements of nocturnal primates in captivity: A chronobiological approach

From the results of chronobiological studies in 11 Aotus lemurinus (trivirgatus) griseimembra, 3 Galago garnettii, 5 Galago senegalensis, and 6 Microcebus murinus, inferences can be made on the most suitable lighting conditions for nocturnal primates kept in captivity. In each species studied light controls the daily periodic course of activity in a dual way. First, the light-dark (LD) cycle acts as the main Zeitgeber, entraining the endogenous circadian timing system (CTS) to the environmental periodicity. Second, the prevailing light intensity has a direct species-specific inhibiting or enhancing effect, masking the level of activity predetermined by the CTS. Marked inhibition of activity is caused especially by low light intensities during dark-time (D-time), which can also lead to drastically reduced food intake (e.g., in Aotus). Therefore, high-amplitude LD cycles should be applied which guarantee a stable external and internal synchronization of the various circadian rhythms of the organism, with a D-illumination intensity high enough to prevent light-induced impairments of the behavior of the animals. Up to now LD cycles of 12:12 h (100–1,000:0.5–0.01 lx; ≥5,000°K) have proved to be most suitable. Only in Microcebus should the D-illumination be reduced to about 10^?4 lx. Moreover, it must be considered that species with a photoperiodically controlled reproduction cycle require specific alterations of the L-time:D-time ratio.     

The effects of feedback lighting on the circadian drinking rhythm in the diurnal new world primate Saimiri sciureus

Feedback lighting provides illumination primarily during the subjective night (i.e., the photosensitive portion of the circadian cycle) in response to a given behavior. This technique has previously been used to test the nonparametric model of entrainment in nocturnal rodents. In three species (Rattus norvegicus, Mesocricetus auratus, and Mus musculus), the free-running period of the locomotor activity rhythm was similar whether the animals were exposed to continuous light or discrete light pulses occurring essentially only during the subjective night (i.e., feedback lighting). In the current experiments, feedback lighting was presented to squirrel monkeys so that light fell predominantly during the subjective night. Feedback lighting was linked to the drinking behavior in this diurnal primate so that when the animal drank, the lights went out. Despite the seemingly adverse predicament, the monkeys maintained regular circadian drinking rhythms. Furthermore, just as the period of the free-running activity rhythms of nocturnal rodents exposed to continuous light or feedback lighting were similar, the period of the drinking rhythms of the squirrel monkeys in continuous light and feedback lighting were comparable (25.6 +/- 0.1 and 25.9 +/- 0.1 hours, respectively), despite a substantial decrease in the total amount of light exposure associated with feedback lighting. The free-running period of monkeys exposed to continuous dark (24.5 +/- 0.1 hours) was significantly shorter than either of the two lighting conditions (P < 0.001). The results presented for the drinking rhythm were confirmed by examination of the temperature and activity rhythms. Therefore, discrete light pulses given predominately during the subjective night are capable of simulating the effects of continuous light on the free-running period of the circadian rhythms of a diurnal primate. The response of squirrel monkeys to feedback lighting thus lends further support for the model and suggests that the major entrainment mechanisms are similar in nocturnal rodents and diurnal primates.     

Internal coupling of five functions of rabbits exhibiting a bimodal circadian rhythm

Abstract

By means of a microcomputer‐assisted, electronic recording system five physiological, circadian rhythms of the rabbit were monitored: locomotor activity, hard faeces excretion, food intake, urine excretion and water intake.

During 120 days of continuous light conditions (30 lx) the animals exhibited a free‐running circadian rhythm. After the fading out of aftereffects of the preceding light: dark schedule on day 51 ± 11 the animals ran free with an individually distinct period length of > 24.0 h (τ: 24.48 ± 0.10 (SD) h). Spectral analysis of coherent data of 50–84 days showed that in addition to the circadian period persistent ultradian periods of 6.1, 8.2 and 12.3 h were present. Within each individual the five functions proved to be tightly coupled during the free‐run, during the time of reentrainment and when entrained with the LD 12:12. While during LD 12:12 the animals exhibited a bimodal rhythm, during the free‐run the rhythm was unimodal in all five functions. In one animal a “splitting”; of the free‐running period occurred. Both components ran free with different period length. They fused again after 38 days. The “splitting”; was reflected in all five functions of this animal.

The behavioural characteristics of meal duration and ‐frequency, duration of activity and ‐intervals, of water intake and urination did not show significant differences during the conditions of LD 12:12 and LL.

The results support Pittendrigh's model of two systems of oscillators, selectively susceptible to the transitions of dark : light and light : dark. Our results suggest that in the rabbit the five functions are governed in common by both oscillator‐systems.     

Peat moss Sphagnum riparium follows a circatrigintan growth rhythm in situ: A case report

In situ growth of Sphagnum riparium Ångstr. shoots were monitored during the 2015 and 2016 growing seasons in Karelia, Russia. It was established that shoot growth rates fluctuated with a period of around 30 days, that is, showed a circatrigintan rhythm. Such rhythms from mosses have not been previously reported. Correlation of growth rates with the percentage of the illuminated portion of the Moon was statistically significant (p<0.01) in both years. Shoot growth rates were reliably higher around the new Moon compared to the full Moon. This phenomenon may be due either to causality or to a pure coincidence of processes with similar rhythms.     

The influence of timeshift on circadian rhythm of sensitivity to X-irradiation in mice

For two groups of male C3H mice an eastbound transmeridional flight was simulated by inducing a time shift of the L:D schedule of 8 hr. The assumed flight brought about a maximal reduction of the daily light and dark span, respectively. A third group remained unshifted. At seven different times during the following day, subgroups of the time shifted mice as well as of the group with unchange schedule were exposed to whole body X-irradiation. Mortality and body temperature of each animal were registered for 30 days following exposure and were regarded as indicators of radiation response. Radioresistance was found to be highest during the second half of the daily light span, confirming earlier reports by other authors. Weil defined effects of the time shift and a corresponding shift of the acrophase of radioresistance could be demonstrated. There was no significant difference between the two time shifted groups, but there was a consistent slight trend towards an advantage for the group whose L:D shift resulted in a maximally reduced dark span.     

Melatonin-dopamine interactions: from basic neurochemistry to a clinical setting

To review the interaction between melatonin and the dopaminergic system in the hypothalamus and striatum and its potential clinical use in dopamine-related disorders in the central nervous system. Medline-based search on melatonin–dopamine interactions in mammals. Melatonin, the hormone produced by the pineal gland atnight, influences circadian and seasonal rhythms, most notably the sleep–wake cycle and seasonal reproduction. The neurochemical basis of these activities is not understood yet. Inhibition of dopamine release by melatonin has been demonstrated in specific areas of the mammalian central nervous system (hypothalamus, hippocampus, medulla-pons, and retina). Antidopaminergic activities of melatonin have been demonstrated in the striatum. Dopaminergic transmission has a pivotal role in circadian entrainment of the fetus, in coordination of body movement and reproduction. Recent findings indicate that melatonin may modulate dopaminergic pathways involved in movement disorders in humans. In Parkinson patients melatonin may, on the one hand, exacerbate symptoms (because of its putative interference with dopamine release) and, on the other, protect against neurodegeneration (by virtue of its antioxidant properties and its effects on mitochondrial activity). Melatonin appears tobe effective in the treatment of tardive dyskinesia, a severe movement disorder associated with long-term blockade of the postsynaptic dopamine D₂ receptor by antipsychotic drugs in schizophrenic patients. The interaction of melatonin with the dopaminergic system may play a significant role in the nonphotic and photic entrainment of the biological clock as well as in the fine-tuning of motor coordination in the striatum. These interactions and the antioxidant nature of melatonin may be beneficial in the treatment of dopamine-related disorders.     

The diurnal modulation of the circatidal activity rhythm by feeding in the isopod eurydice pulchra

The diurnal modulation of circatidal activity was studied in freshly caught Eurydice pulchra of different feeding states. Apparently fully fed specimens displayed definite circadian modulation, with greatest tidal activity at the time of expected night‐time high tides, and apparently starved animals showed no circadian variation. Circatidal activity was also entrained in the laboratory using cycles of artificial agitation and the subsequent pattern of free‐running rhythmicity was studied. Animals fed prior to entrainment displayed definite diurnal modulation of the pattern of ciractidal swimming activity. Those fed after the entrainment regime, or not at all, displayed no apparent diurnal inequality of tidal activity peaks. No relationship between diurnal inequality and phototactic behaviour of freshly collected specimens was detected.     

The statistical analysis of tidal rhythms: Tests of the relative effectiveness of five methods using model simulations and actual data

Endogenous rhythms in intertidal organisms are often very complex and imprecise. Thus, confusing results are sometimes obtained when applying various interpretive analytical techniques. In an attempt to resolve this problem, ten different models representing typical organismic tidal‐rhythm displays were created and examined with five different inferential statistical techniques. The exercise was designed to test the relative effectiveness of these techniques in detecting the presence of known cycles in the models, and estimating their period lengths. The same comparison was then repeated on sets of animal‐derived data.

All of the five methods had their merits, but, depending on the model being examined, the results from the various methods were not identical. Three of the techniques produce harmonics, making data that contain multiple periods especially difficult to decipher. Often both tidal and circadian periods are displayed by shore dwellers; all five methods were able to find these two periods. But when the difference in circa period length was close, only one technique (array analysis) could make a distinction. This technique was also the only one able to handle data in which the period was not constant. Interestingly, this simplest of methods is probably the best all‐round method of discovery. Many more subtle, but important, differences were also noted, and it is recommended that more than one method always be used to ensure accuracy.     

The contribution of an hourglass timer to the evolution of photoperiodic response in the pitcher-plant mosquito, Wyeomyia smithii

Abstract Photoperiodism, the ability to assess the length of day or night, enables a diverse array of plants, birds, mammals, and arthropods to organize their development and reproduction in concert with the changing seasons in temperate climatic zones. For more than 60 years, the mechanism controlling photoperiodic response has been debated. Photoperiodism may be a simple interval timer, that is, an hourglasslike mechanism that literally measures the length of day or night or, alternatively, may be an overt expression of an underlying circadian oscillator. Herein, we test experimentally whether the rhythmic response in Wyeomyia smithii indicates a causal, necessary relationship between circadian rhythmicity and the evolutionary modification of photoperiodic response over the climatic gradient of North America, or may be explained by a simple interval timer. We show that a day-interval timer is sufficient to predict the photoperiodic response of W. smithii over this broad geographic range and conclude that rhythmic responses observed in classical circadian-based experiments alone cannot be used to infer a causal role for circadian rhythmicity in the evolution of photoperiodic time measurement. More importantly, we argue that the pursuit of circadian rhyth-micity as the central mechanism that measures the duration of night or day has distracted researchers from consideration of the interval-timing processes that may actually be the target of natural selection linking internal photoperiodic time measurement to the external seasonal environment.