Circadian emergence and movement of captive juvenile tuatara (Sphenodon spp.)

Abstract

Knowledge of the circadian behaviour of young tuatara (Sphenodon spp.) is relatively scarce because tuatara are difficult to observe in the wild. We document diurnal, nocturnal and crepuscular emergence and movements (half‐body movement, walking and running) of three groups of captive juvenile tuatara (2‐ and 3‐year‐old Sphenodon guntheri, and 5‐year‐old S. punctatus). Juvenile tuatara emerge predominantly at night, but move around above ground, mainly during the day and around sunset. Differences in emergence andmove‐ment scores between the three study groups were evident, probably linked with age, species or housing conditions, which were inevitably coupled in our study. We found that 2‐year‐old tuatara in captive conditions emerged less frequently than, but once above ground, moved more than 3‐ and 5‐year‐olds in semi‐captive conditions. Activities in semi‐captive conditions were not correlated with temperature, light or humidity. We conclude that young tuatara may be primarily adapted to nocturnal activity, but thermal restrictions and possible hardwired adaptations to avoid predators and conspecifics may make day‐time movements safer.     

The use of PIT telemetry to study movements of ammocoetes and metamorphosing sea lampreys in river beds

Passive integrated transponder (PIT) tags were surgically implanted in 118 sea lamprey Petromyzon marinus ammocoetes which were left to recover in the laboratory for 2 months. During this period 55 individuals started to metamorphose. In the late summer of 2002 the tagged animals were released in a small tributary of the River Mondego, Portugal, and were regularly monitored for a period of 2 months using a portable PIT tag reader. The distribution of the released animals changed from an initial uniform pattern to a random distribution, and then to an aggregated pattern. At the end of the first week 60% of the tagged sea lampreys had already left the study area, indicating their dynamic behaviour. Ammocoetes were more active than metamorphosing sea lampreys, and downstream movements were more frequent when compared to the upstream ones, which were usually a short distance. In order to determine the influence of the dark‐light cycle in the diel activity rhythms, 10 tagged sea lamprey ammocoetes were released in a tank (2000 l capacity) and their position monitored twice a day, for a period of 1 month. Ammocoetes locomotor activity appeared to be conditioned by circadian rhythms, and they were particularly active during darkness.     

Rhythmic cortisol secretion in the equine: Analysis and physiological mechanisms

Abstract

Four Thoroughbred mares (no. 1–4) were maintained under constant temperature (24°C) and controlled light (L/D:12/12 with lights on at 06.00 hr) conditions. They were fed and watered ad libitum with fresh feed and water given at 09.00 hr. After a 45‐day pre‐conditioning period, blood samples were obtained by veinipuncture at 4‐hr intervals for 14 days to determine circadian and day‐to‐day variation. The horses exhibited a circadian rhythm with maximum values attained at about 12.00 hr, however, there are periods of days in which no rhythm is distinguishable. Ultradian rhythms with mean periods of 105 to 128 and 24 to 31 min are superimposed upon the circadian rhythm. The individual rhythms are quite variable from horse to horse and within the same horse. During periods of decline in plasma cortisol with metabolic half‐lives of approximately 70 min, secretion of cortisol was very low or had ceased. During periods of increasing plasma concentration, secretion was occurring at a faster rate than degradation. Rapid decreases in plasma concentration (metabolic half‐life of approximately 30 min) was accompanied by a rise in specific activity indicating cortisol with a high specific activity was entering the plasma pool from other storage pools.     

Circadian and light-induced conductance changes in putative pacemaker cells of Bulla gouldiana

The ocular circadian rhythm of compound action potential frequency in Bulla gouldiana is driven by rhythmic changes in the membrane potential of putative circadian pacemaker cells. Changes in the membrane potential of these neurons is required for light-induced phase shifts of the rhythm. We have tested the proposition that these changes in membrane potential reflect underlying changes in ionic conductances. We have found that: 1. Membrane conductance in the dark is highest during the subjective night when the cells are hyperpolarized, decreases as the cells depolarize spontaneously near projected dawn and is lowest during the subjective day. The changes in membrane potential and conductance follow a similar time course. 2. Long pulses of light delivered to eyes during their subjective night produce a characteristic response: There is initially a large, phasic depolarization accompanied by a burst of CAPs; this is followed by a repolarizing phase during which CAP activity is reduced to zero; and finally a tonic depolarization develops that is accompanied by a resumption of CAP activity at a steady rate. 3. During the subjective night, the tonic depolarization is accompanied by a decrease in conductance compared to the previous dark value. However, light pulses of similar duration delivered to eyes during their subjective day causes tonic depolarizations and increased CAP activity, but no measurable change in conductance. 4. Membrane responses to light are sensitive to agents that reduce Ca2+ flux. Light pulses during the subjective night produce a phasic depolarization, but the repolarization phase is eliminated in low Ca2+/EGTA seawater and is reduced in 5 mM Ni2+.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Circadian rhythms in human erythrocytes in vitro not confirmed

Abstract

Human erythrocytes, white and resealed erythrocyte ghosts, and hemolysates were analysed for the occurrence of circadian and ultradian rhythms in vitro. Although the experimental conditions were extensively varied, we did not find any indication for the existence of rhythmicity. These results are at variance with the reports by others.     

Biological and psychological rhythms: An integrative approach to rhythm disturbances in autistic disorder

Biological rhythms are crucial phenomena that are perfect examples of the adaptation of organisms to their environment. A considerable amount of work has described different types of biological rhythms (from circadian to ultradian), individual differences in their patterns and the complexity of their regulation. In particular, the regulation and maturation of the sleep–wake cycle have been thoroughly studied. Its desynchronization, both endogenous and exogenous, is now well understood, as are its consequences for cognitive impairments and health problems. From a completely different perspective, psychoanalysts have shown a growing interest in the rhythms of psychic life. This interest extends beyond the original focus of psychoanalysis on dreams and the sleep–wake cycle, incorporating central theoretical and practical psychoanalytic issues related to the core functioning of the psychic life: the rhythmic structures of drive dynamics, intersubjective developmental processes and psychic containment functions. Psychopathological and biological approaches to the study of infantile autism reveal the importance of specific biological and psychological rhythmic disturbances in this disorder. Considering data and hypotheses from both perspectives, this paper proposes an integrative approach to the study of these rhythmic disturbances and offers an etiopathogenic hypothesis based on this integrative approach.     

Ultradian Rhythms in Desmodium

The leaves of Desmodium gyrans (L.F.) DC show circadian movements in the terminal and ultradian movements of the lateral leaflets. The movements are due to swelling and shrinking of motor cells in special organs. The anatomy of these pulvini is described for the lateral leaflets. Data from electrophysiological recordings using microelectrodes inserted into the lateral pulvini, together with treatments that affect the proton pumps and ion channels, have been used to develop a physiological model of the ultradian leaflet movement. It explains the oscillations in the motor cells as being due to a change between a pump state and depolarization. During the pump state, ions are taken up, causing water influx and swelling of the motor cells. Depolarization causes loss of ions and water efflux (the motor cells shrink). The roles of calcium and the phosphatidyl inositol signal chain are discussed on the basis of experiments using chemical agents that affect these processes. Since calcium oscillations are known to occur in organisms in both time and space, an attempt has been made to simulate the situation in Desmodium pulvini by a model of specially coupled oscillators. Effects of different other treatments of the lateral pulvini are discussed. Oscillations in the minute range seem to be more common and some might be related to turgor regulation and ion uptake comparable to the situation in Desmodium. The ultradian control of the lateral pulvini and the circadian control of the terminal pulvini are apparently based on different mechanisms.     

Activity rhythms of enzymes in human red blood cell suspensions

Abstract

We have established the presence of a rhythm in the activity of 4 enzymes in in‐vitro cell suspensions of human red blood cells. Glucose 6‐phosphate dehydrogenase and glutamate oxaloacetate transaminase demonstrated semicircadian patterns of activity, while acid phosphatese and acetylcholine esterase exhibited circadian activity rhythms. The ratios between the highest to lowest activities varied from 2:1 to 10:1 among the various enzymes. The affinity of glucose 6 phosphate dehydrogenase to its substrate and coenzyme remained constant throughout the cycle. No evidence was obtained for the presence of a soluble inhibitor at the lower levels of the activity. Sonication of hemolysates with low glucose 6 phosphate dehydrogense activity yielded additional activity comparable to that of the peak activity. Sonication of hemolysates from the time of the peak activity did not change the original activity. The observations point to a role of the cell membrane in the biological clock.     

Review of diel rhythmic activities in physiological functions of scorpions

In this study I review the subject of biological rhythms in scorpions. This will include only some of the diel rhythmic endogenous physiological functions and not the locomotory rhythmicity, which will be dealt separately. Most studies reported here were conducted on 13 scorpion species that were studied in 39 different studies. Most of these (66.7%) were studies on a single species (Heterometrus fulvipes). Being a scorpionid, it sits and waits near its burrow not being very active, especially the females. The fact that experimenting was carried out irrespective of species diversity, gender, ecological or physiological conditions, and was usually done on animals kept in captivity for some time before the experimenting had started, is a major drawback to this kind of study. Although the main conclusion appears to be that enzymes reached their peak activity at 20.00 h, there are some exceptions showing otherwise that need further study in order to explain them.     

Circadian rhythms and feeding time in fishes

Synopsis Although several studies have described effects of meal frequency and timing of meals on growth performance and body composition of different species of fishes, the mechanisms by which such variables influence the energy partitioning processes is not known. They may interact with the natural feeding rhythm of the fish, or with various behavioural and physiological parameters that exhibit circadian-like patterns; however, in most cases, the endogenous character of such rhythms is not clear. The time of feeding, perse, can act as a Zeitgeber and override the effect of the light/dark alternation. Fish that are fed always at the same time of day show typical pre-feeding activity. Blood levels of some nutrients and hormones also show peaks or troughs at the time of feeding, but whether these are pre-feeding or post-prandial events is not clear. These results from fish are compared with similar studies with mammals. The existence and location of an endogenous multi-oscillator system is also discussed.     

Temporal Patterns of Reported Single-Vehicle Car and Truck Accidents in Texas, U.S.A. During 1980-1983

Reported single car and truck accidents due specifically to driver 'fatigue' for the 4-year span of 1980-1983 were analyzed for 24-hr, 7-d and 1-yr patterns. Three types of data were examined: (1) accidents in rural Texas, (2) accidents only in San Antonio, the fourth largest city in Texas and (3) accident ratio (number of accidents per time interval divided by traffic volume for the interval) in this city.

A statistically significant seasonal variation of relatively low amplitude with peaks in May and July was detected only for accidents in rural areas. High-amplitude periodicities of 7 d were evident in all the data sets, with a peak on the weekend. A very prominent 24-hr pattern was detected as well, with the acrophase determined by single cosinor around 0300. A slight secondary peak in accidents, around 1500, was evident in the data from the rural areas. This secondary peak represented a 12-hr rhythm in addition to the 24-hr. Overall, features of the temporal patterns in accidents over 24 hr and over the year in urban and rural areas differed only slightly. Accident ratios yielded results similar to accident frequencies. However, with regard to the rural data, the shape of the 24-hr temporal pattern varied with driver age; older drivers exhibited a flatter curve with a more pronounced afternoon rather than early morning (around 0300) peak.     

Contributions Made to Chronobiology by Studies of Fiddler Crab Rhythms

One of the classic organisms used in chronobiological research is the fiddler crab (genus Uca), an animal unique in that it displays both circadian and tidal (i.e., circalunidian) rhythms. The pioneering work on this animal helped produce the early evidence for many of the standard properties now recognized for all circadian rhythms: near temperature independence of the period, phase lability and setability, the light and temperature sensitivity rhythms expressed by phase response curves, and the persistence of rhythms in organs isolated from a multicellular animal. Importantly, results arising from studies of this crab–and a few other organisms–resulted in the development of the exogenous timing hypothesis. While philosophically sound, the lack of supporting evidence for this hypothesis has resulted in it being discarded by most chronobiologists; but while still in its prime, it drew great interest, and therefore grant support, to the field in general, stimulated a great deal of research that otherwise might not have been performed, and resulted in the discovery of environmental stimuli previously unsuspected to influence organisms. As could be expected, continuing work with this crab, using modern approaches and statistical techniques, has modified earlier findings and interpretations, has revealed new properties, and has resulted in the creation of new hypotheses. The review and update is a synthesis of 45 years of this work.     

Using Covariance to Unravel the Effects of Meteorological Factors and Daily and Seasonal Rhythms

Many factors contribute to the activity of animals in the wild. Whilst daily and seasonal rhythms are likely to be present, and to represent underlying biological functions, these will normally be modified by several factors in the environment. Important amongst these are light, temperature, humidity and whether or not it is raining. There is also the problem that the factors might interact, the effect of, say, time of day, being modified by the concomitant temperature. Separating out the effects of these different factors experimentally can be extremely arduous, if not impossible. An alternative approach is to treat the environmental factors as covariants, and then to separate out their effects from the biological ones by statistical means, using Analysis of Covariance, ANCOVA. The potential of this method is illustrated in the current report by a consideration of exits and entries of a colony of bees from their hive. Hourly measurements of this behaviour were taken during the daylight hours for three consecutive days in 11 consecutive months of the year. At the same time, ambient temperature, light intensity, humidity and whether or not it was raining were recorded. ANCOVA enabled the effects of temperature, humidity, light and rainfall upon the exits from the hive and entries back into it to be separated from the effects of time of day and time of the year. The analyses allowed those climatic variables, in addition to time-of-day and time-of-year effects, that influenced behaviour to be identified. Such climatic variables have not been previously isolated, and this might have lead to a misinterpretation of similar results in the past. Having separated out any effects of climatic variables (the covariates), the interaction between time of day and time of the year could then be investigated. Furthermore it has been possible to quantify the effects upon behaviour of each covariate. Rainfall was shown to decrease activity by more than 80%. For the other variables (temperature, humidity and light intensity), the statistical model allowed for the possibility that an increase in the variable initially produced a rise in activity but that this was followed, if the variable continued to rise, by a fall in activity. For light intensity, only a very modest increase in activity was found, and this continued throughout the range of intensities measured. However, for both temperature and humidity, the effects were more marked and showed 'turning points'. That is, activity increased as the ambient temperature rose until activity peaked at about 33-35°C; after which activity began to fall. Similarly, entries into the hive rose with increasing humidity up to a value of 48%, but fell thereafter. By contrast, exits from the hive increased with increasing humidity throughout the range measured. In the biological system tested, this form of analysis has produced valuable information about the way different factors influence activity in a field study. The results strongly suggest that the proposed methodology has a much wider and more general application. The way in which this type of analysis might be elaborated is discussed.     

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.     

Diurnal rhythms in psychological reward functioning in healthy young men: ‘Wanting’, liking,and learning

A range of evidence suggests that human reward functioning is partly driven by the endogenous circadian system, generating 24-hour rhythms in behavioural measures of reward activation. Reward functioning is multifaceted but literature to date is largely limited to measures of self-reported positive mood states. The aim of this study was to advance the field by testing for hypothesised diurnal variation in previously unexplored components of psychological reward: ‘wanting’, liking, and learning using subjective and behavioural measures. Risky decision making (automatic Balloon Analogue Risk Task), affective responsivity to positive images (International Affective Pictures System), uncued self-reported discrete emotions, and learning-contingent reward (Iowa Gambling Task) were measured at 10.00 hours, 14.00 hours, and 19.00 hours in a counterbalanced repeated measures design with 50 healthy male participants (aged 18–30). As hypothesised, risky decision making (unconscious ‘wanting’) and ratings of arousal towards positive images (conscious wanting) exhibited a diurnal waveform with indices highest at 14.00 hours. No diurnal rhythm was observed for liking (pleasure ratings to positive images, discrete uncued positive emotions) or in a learning-contingent reward task. Findings reaffirm that diurnal variation in human reward functioning is most pronounced in the motivational ‘wanting’ components of reward.     

Free‐running rhythmicity in the life spans of hydranths of the marine cnidarian,Campanularia flexuosa

Abstract

The adrenergic agonists and antagonists, norepinephrine, phenylephrine, iso‐proterenol, phentolamine, and propranolol, were administered to rats in different phases of the diurnal cycle, and their effects on tyrosine aminotransferase activity were studied. All substances tested, regardless whether being typically α‐ or ß ‐adrenergic or whether being agonists or antagonists, elevated tyrosine aminotransferase during the minimum of enzyme activity. The effects at the enzyme maximum, however, were generally more or less depressive. The extent of the depressions by norepinephrine and by propranolol highly depended on the duration of treatment. The hepatic concentration of cyclic AMP did not exhibit a significant rhythmicity. The results do not favour the idea of an adrenergic control of the diurnal rhythm in tyrosine aminotransferase activity.     

Vertical-migration patterns of flagellates in a community of freshwater benthic algae

The population densities of sediment-inhabiting flagellates sampled from a shallow eutrophic lake in April 1986 were investigated at intervals of 1 or 1.5 h over a twenty hour period in the laboratory under natural irradiance and in controlled conditions. In natural irradiance the flagellates exhibited a vertical migration rhythm up onto the sediment surface after dawn and down into the sediment during the afternoon. Details of the timing of the migration movements and period of time flagellates were present on the sediment surface differed between species and five flagellate groups: trachelomonads, green euglenoids, Chamydomonads, chrysophytes and cryptomonads. During daylight, twenty-seven species maintained population maxima at the surface of the sediment on eight occasions. The species composition of these maxima differed and eight species were found to have two maxima on the surface of the sediment at different times of day. Numbers of three species of chrysophycean flagellates and Rhodomonas minuta increased again on the sediment surface after dark. Under continuous irradiance at 10°C, the migration cycle of all five groups of flagellates was affected. Some evidence for an endogenous nature of this rhythm was found for green euglenoids and Chamydomonads. Numbers of chrysophytes, particularly Synura spp. increased in constant light in the surface layers of sediment.Thus a mosaic of vertical migration patterns was described in an epipelic community of algae dominated by five groups of flagellates. The importance of this in the survival strategy and ecology of these sediment-inhabiting algae is discussed.     

A persistent circhoral ultradian rhythm is identified in human core temperature

There have been inconclusive reports of intermittent rhythmic fluctuations in human core temperature, with the fluctuations having a period of about an hour. However, there has been no definitive demonstration of the phenomenon. This is likely due to the intermittency and seeming instability of the events. They have been assumed to be secondary rather than autonomous phenomena, putatively arising from the oscillation between rapid eye movement (REM) and non-REM (NREM) sleep. In this study, we report identification of a clear, persistent circhoral ultradian rhythm in core temperature with a period for this study sample of 64 ± 8 minutes. It appeared simultaneously with an intact circadian core temperature rhythm, persisted despite complex perturbations in core temperature brought about by the sequelae of 40h of sleep deprivation, and could not be attributed to sleep stage alternation or other endogenous or exogenous factors. Analysis of power spectra using the maximum entropy spectral analysis (MESA) method, which can uncover hidden rhythmicities, demonstrated that the apparent intermittency of the rhythm is due to periodic interference of this rhythm by other rhythmic events. The persistence of this oscillation suggests that, in this system as in the endocrine system, circhoral regulation is an integral component of thermoregulatory control. Identifying the source and functional role of this novel rhythm warrants further work.     

Comparative studies of tidal rhythms. VI. Several clocks govern the activity of two species of fiddler crabs

The tide‐associated persistent activity rhythms of the ocypod crabs, Uca pugnax and U. pugilator were observed in constant conditions, some for as long as three months. In some animals the twice/day peaks of activity were found to scan the day at significantly different rates from one another. Individual peaks in some animals split into two fragments. And at times, one peak would fade and then return, or vanish completely. These examples of the independence between tide‐related activity peaks have become the basis for a hypothesis that each peak is controlled by its own clock(s). The basic period of these clocks is “circalunidian”, with periods varying up to about 4–8% on either side of 24.8 hours.