Effects of light pulses on the locomotor activity rhythm of Orchestia montagui (Amphipoda,Talitridae)

Animals of the amphipod Orchestia montagui are kept in constant darkness with two short light pulses. One pulse is applied at the beginning of subjective night (around the dusk) and the other one at the end of subjective night (around the dawn). The pulse duration is estimated in the order of one or two hours around the dusk as well as the dawn. The locomotor activity rhythm was monitored in individual animals in summer under constant temperature. Results revealed that whatever the experimental conditions, under continuous or interrupted darkness by pulses, two endogenous components have been highlighted. In fact, Periodogram analysis showed the presence of ultradian and circadian periods around 12 and 24 h, respectively. The shortest circadian period and the most important inter-individual variability was observed under pulse of 2 h around the dusk with mean value equal to τ_DD+pulse = 24h38′ ± 4h34′. The activity profiles are in majority unimodal. Moreover, the most activity peak showed a slipping of its location from the middle of subjective night under constant darkness to the middle of subjective day under pulse. Globally, the locomotor activity rhythm of O. montagui was better defined under pulses and specimens were significantly more active under continuous darkness. Moreover, a great variability around the activity time was observed especially with pulse of 1 h.     

INTERNAL DESYNCHRONIZATION OF THE CIRCADIAN ACTIVITY AND FEEDING RHYTHM IN AN OWL MONKEY (AOTUS LEMURINUS GRISEIMEMBRA): A CASE STUDY

In the free-running circadian locomotor activity rhythm of a 7-year-old male owl monkey (Aotus lemurinus griseimembra) kept under constant light and climatic conditions (LL 0.2 lux, 25°C ± 1°C, 60 ± 5% relative humidity [RH]), a second rhythm component developed that showed strong relative coordination with the free-running activity rhythm of 24.4h and a 24h rhythm. The simultaneously recorded feeding activity rhythm strongly resembled this rhythm component. Therefore, it seems justified to infer that there was an internal desynchronization between the two behavioral rhythms or their circadian pacemakers, that is, between the light-entrainable oscillator located in the suprachiasmatic nuclei (SCN) and a food-entrainable oscillator located outside the SCN. This internal desynchronization may have been induced and/or maintained by a zeitgeber effect of the (irregular) 24h feeding schedule on the food-entrainable oscillator. The weak relative coordination shown by the activity rhythm indicates a much weaker coupling of the light-entrainable oscillator to the food-entrainable oscillator than vice versa. (Chronobiology International, 17(2), 147–153, 2000)     

Light and dark rations and the photic entrainment of circadian locomotor activity patterns in the South American Silver Catfish (Rhamdia quelen,Quoy & Gaimard, 1824)

The aim of this study was to evaluate the daily rhythm of locomotor activity in Rhamdia quelen (R. quelen). A total of 30 fish were enrolled in the study and were equally divided in 10 groups and maintained in 100 liters tanks. The locomotor activity was measured in fish maintained under the LD 12:12 photoperiod regime; thereafter, the LD cycle was reversed to DL in order to study the resynchronization and to explore the endogenous pacemaker. Subsequently, the fish were subjected to constant conditions of light to test whether or not locomotor rhythms are regulated by the endogenous circadian clock. The effect of increasing light length and intensity was studied on daily rhythm of locomotor activity of fish. Our results showed that the R. quelen is a strictly diurnal species, the rhythm of locomotory activity resynchronized quickly after inverting the LD cycle and persist under free course LL, suggesting a circadian origin. The light showed a significant masking effect often blocking the expression of the biological rhythm. The strictly diurnal behavior is controlled directly by the photoperiod and maintained even under very dim light (30 lux).     

Studies on Halimeda IV. An endogenous rhythm of chloroplast migration in the siphonous green alga,H. distorta 1

Abstract

Halimeda has been found particularly suitable for studies of long‐distance chloroplast migration by virtue of its coenocytic structure and calcium carbonate skeleton. A circadian rhythm of chloroplast migration in Halimeda distorta was monitored by videography of segment surface pigmentation. In normal 12 h light/12 h dark treatments synchronised with dawn and dusk, the segments were green all day, began to become pale immediately the light was turned off, and then remained almost white for most of the night until beginning to re‐green a few hours before dawn. As a result of that, they were already quite green by the time the light was turned on. In continuous darkness a similar cycle, albeit with reducing amplitude and a period of about 23 hours, was maintained for at least 7 days. However, this cycle differed significantly from the normal one in that the segments did not remain green after the light was not switched on at dawn, but rather began to pale immediately thereafter. Conversely, in continuous light the segments did not become pale at any time. Thus, the rhythmical re‐emergence of the chloroplasts before dawn and their subsequent withdrawal appears to be controlled by an endogenous rhythm which is independent of light. However, light does completely, but reversibly, inhibit the chloroplast withdrawal component of the cycle. This behaviour of the chloroplasts in Halimeda is very similar to that in the related alga, Caulerpa, but it is quite different from that in another extensively Studied but unrelated siphonous green alga, Acetabularia, in which the circadian rhythm of chloroplast migration is maintained in continuous light.     

Temporal Organization in Locomotor Activity of the Hypogean Loach, Nemacheilus Evezardi, and its Epigean Ancestor

Locomotor activity rhythm in the hypogean population of Nemacheilus evezardi was recorded first under light-to-dark (LD) 12 : 12 h cycle and then DD. The results were compared with that of its epigean counterpart held under comparable regimes. In LD 12 : 12, while hypogean loach exhibited a distinct bimodality in its locomotor activity rhythm, it was altogether absent in the case of epigean population. In hypogean loach, dark-to-light transition peak in LD was observed to free-run under DD. The same was not discernible in case of epigean loach. The locomotor activity rhythm in epigean fish was noticed to free-run in DD either from the dawn peak or dusk peak in LD. It is hypothesized that the hypogean fish still possesses a functional oscillator underlying its overt circadian rhythm in locomotor activity. The ecophysiological significance of these findings is yet to be fully understood.     

Towards a Characterization of the Locomotor Activity Rhythm of the Supralittoral Isopod Tylos europaeus

Freshly collected samples of Tylos europaeus from Korba beach (northeast of Tunisia) were housed in an environmental cabinet at controlled temperature (18°C?±?.5°C) and photoperiod. Locomotor activity was recorded under two photoperiodic regimens by infrared actography every 20?min by multichannel data loggers. One regimen simulated the natural light-dark cycle on the day of collection, whereas the second imposed a state of continuous darkness on all individuals. Under entraining conditions, the animals displayed rhythmic activity, in phase with the period of darkness, whereas in continuous darkness these isopods exhibited a strong endogenous rhythm with circadian and semidiurnal components at mean periods of τ (h:min)?=?25:09?±?01:02?h and τ?=?12:32?±?00:26?h, respectively. Under free-running conditions, this endogenous rhythm showed significant intraspecific variability. (Author correspondence: bohli.dhouha@gmail.com)     

Light Synchronization of the Daily Spawning Rhythms of Gilthead Sea bream (Sparus aurata L) Kept under Different Photoperiod and after Shifting the LD Cycle

Reproduction in most fish is typically a seasonal process, as spawning takes place usually at a given time of the year, depending on the reproduction strategy of the species, to ensure maximal survival of offspring. Nevertheless, fish reproduction cannot be considered an exclusively annual phenomenon, because spawning may also show daily rhythmicity. In this study, we investigated the existence of a daily spawning rhythm in gilthead seabream (Sparus aurata L) exposed to different light‐dark (LD) cycles and at different times of the year using an automatic and programmable egg collector. Floatability and fertilization rates were analyzed at different times throughout the 24 h. The results showed a daily spawning rhythm with spanning occurring from 14:30 to 21:30 h, with the acrophase (peak time) being 18:29 and 18:08 h in fish exposed to an artificial photoperiod of 9L∶15D in winter and in spring, respectively. Nevertheless, in fish exposed to a natural photoperiod of 12L∶12D in spring, the acrophase of the rhythm was recorded later, at 21:28 h. The average fertilization rate was 87%, and no significant differences were found between the different hours of spawning. Moreover, when the LD cycle (9L∶15D) was shifted by 12 h, the daily spawning rhythm gradually re‐synchronized, resuming a stable phase‐relationship after 4–5 transient days, which is characteristic of a endogenous circadian rhythm. Our results clearly demonstrated the existence of a 24 h period of spawning in gilthead sea bream, with a peak anticipating the forthcoming night, and its capacity to gradually re‐synchronize after a 12 h shift in the LD cycle, pointing to the endogenous nature of this rhythm. These findings will be valuable for better understanding the reproductive physiology of this species and for optimizing the protocols of egg collection and larvae production in aquaculture. (Author correspondence: javisan@um.es)     

Daily and circadian rhythms in the activity of mixed function oxidases system in rats of different age

Abstract

An age‐associated alterations in daily and circadian changes of cytochrome P‐450‐linked monooxygenases system activity were studied using 1‐, 6‐ and 12‐months old male Wistar rats, in winter and in spring season. Cytochrome P‐450 and NADPH‐cytochrome P‐450 reductase showed 12h rhythm in all investigated age groups of animals. Cytochrome b₅ and NADH‐cytochrome b₅ reductase were characterized by a 12h daily rhythm in 1‐month old rats, but in older ones 24h circadian rhythm was found. There was not significant changes of the rhythm pattern in the activity of investigated MFO system ingredients in rats of different age, between spring and winter.     

Light control of the circadian activity rhythm in mouse‐eared bats (Myotis myotis Borkh. 1797)

Abstract

The aim of this study was to analyse the effect of light respectively illumination cycles on the activity rhythm of the insectivorous bat Myotis myotis (M.m.). A new electronic registration system devised for this purpose can be applied almost universally in recording the activity of terrestrial animals.

M.m. is a strictly dark‐active species with a bimodal activity pattern of bigeminus character. Under constant conditions, M.m. reveals a free running circadian activity rhythm. Its period length varies between 22.6 and 27.8 h and is positively correlated with the intensity of illumination. The range of entrainment of the circadian activity rhythm of M.m. is unusually wide. Accordingly, M.m. resynchronizes very quickly after phase shifts of the Zeitgeber LD. Activity maxima in the range of 10^‐4 lx occur in LD 12:12 with constant illumination in L and varied illumination in D as well as in LL with varying intensity.

It is to be discussed whether the wide variability of different parameters in the circadian system of M.m. compared with those of other Chiroptera can be interpreted as an adaptation to ecological factors.     

Clock control of foraging in the isopod Scyphax ornatus Dana

Abstract

The terrestrial sand beach isopod Scyphax ornatus Dana exhibits circadian and circa-semilunar activity rhythms when kept in constant conditions in the laboratory. The circadian rhythm restricts activity to the subjective night and can be synchronised to artificial light cycles. The circa-semilunar rhythm is expressed as a cyclic variation in overall activity level, with isopods alternately active on 6–8 consecutive nights and then inactive on the next 6–8 nights. The circa-semilunar rhythm matches a fortnightly cycle in food availability on the isopods’ home beach, but does not appear to be causally related to the lunar cycle, the spring/neap tidal cycle, or to moulting. This and other evidence suggests that the ecologicalrole of the endogenous circa-semilunar rhythm is to allow Scyphax, within the protection of their burrows, to predict nightly foraging opportunities; a new role for such a long-period rhythm.     

Thalassomyxa australis rhythmicity II. No entrainment by light‐dark‐cycles and temperature cycles?

Abstract

The rhythmic change between an active phase and a resting phase of the plasmodial rhizopod Thalassomyxa australis sustained on the diatome Amphiprora, is not synchronized by a 12: 12 h light‐dark‐cycle. Likewise, 12: 12 h temperature cycles of 8°C difference such as 23°/15°C, 25°/17°C, 27°/19°C are not entraining this rhythm.     

Circadian Pattern of Wheel‐Running Activity of a South American Subterranean Rodent (Ctenomys cf knightii)

Circadian rhythms are regarded as essentially ubiquitous features of animal behavior and are thought to confer important adaptive advantages. However, although circadian systems of rodents have been among the most extensively studied, most comparative biology is restricted to a few related species. In this study, the circadian organization of locomotor activity was studied in the subterranean, solitary north Argentinean rodent, Ctenomys knightii. The genus, Ctenomys, commonly known as Tuco‐tucos, comprises more than 50 known species over a range that extends from 12°S latitude into Patagonia, and includes at least one social species. The genus, therefore, is ideal for comparative and ecological studies of circadian rhythms. Ctenomys knightii is the first of these to be studied for its circadian behavior. All animals were wild caught but adapted quickly to laboratory conditions, with clear and precise activity‐rest rhythms in a light‐dark (LD) cycle and strongly nocturnal wheel running behavior. In constant dark (DD), the rhythm expression persisted with free‐running periods always longer than 24 h. Upon reinstatement of the LD cycle, rhythms resynchronized rapidly with large phase advances in 7/8 animals. In constant light (LL), six animals had free‐running periods shorter than in DD, and 4/8 showed evidence of “splitting.” We conclude that under laboratory conditions, in wheel‐running cages, this species shows a clear nocturnal rhythmic organization controlled by an endogenous circadian oscillator that is entrained to 24 h LD cycles, predominantly by light‐induced advances, and shows the same interindividual variable responses to constant light as reported in other non‐subterranean species. These data are the first step toward understanding the chronobiology of the largest genus of subterranean rodents.     

Photic entrainment of daily rhythm pattern of locomotor activity in sea bass (Dicentrarcus labrax)

The aim of this study was to evaluate the circadian rhythm of daily locomotor activity in sea bass exposed to three different artificial lighting regimes including 12/12, 24/0, and 0/24 L/D periods, and scheduled daytime feeding. Daily rhythm of locomotor activity during 12/12 L/D was observed, whereas locomotor activity recorded during 24/0 and 0/24 L/D resulted arrhythmic. Statistical differences in mesor values among the photoperiods and between light and dark phases of each photoperiod were found. During the 12/12 and 0/24 L/D, the fish were active mostly during the light phase. During 24/0 L/D, a phase inversion occurred. The results showed that photoperiod is a dominant synchronizer in sea bass, and that the appetite in this fish follows daily rhythms which does not match the imposed feeding schedule, suggesting the absence or the lability of internal process that couples feeding cycles and biological rhythms.     

Effect of temperature on circadian rhythm controlling the crepuscular activity of the burying beetle Nicrophorus quadripunctatus Kraatz (Coleoptera: Silphidae)

Locomotor activity rhythm was examined at various temperatures under a 16 h light : 8 h dark photoperiod (LD 16:8) or LD 12:12 using adults of the burying beetle Nicrophorus quadripunctatus. At 20°C, the locomotor activity of the beetles showed a bimodal daily pattern with two peaks around lights on and lights off under both photoperiods. This bimodal activity rhythm persisted under constant darkness; therefore, the activity of adult N. quadripunctatus is controlled by a circadian clock. Adults showed a bimodal activity pattern for temperatures ranging from 15 to 25°C. The evening peak of the daily activity was earlier at lower temperatures. These findings suggest that in the field, N. quadripunctatus shows crepuscular activity, and is active earlier in the afternoon in cooler seasons. In this species, therefore, temperature appears to play an important role in the determination of daily activity patterns.     

Evidence for a Plastic Dual Circadian Rhythm in the Oyster Crassostrea gigas

Although a significant body of literature has been devoted to the chronobiology of aquatic animals, how biological rhythms function in molluscan bivalves has been poorly studied. The first objective of this study was to determine whether an endogenous circadian rhythm does exist in the oyster, Crassostrea gigas. The second objective was to characterize it in terms of robustness. To answer these questions, the valve activity of 15 oysters was continuously recorded for 2 mo in the laboratory under different entrainment and free-running regimes using a high-frequency noninvasive valvometer. The present work demonstrates the presence of a circadian rhythm in the oyster Crassostrea gigas. First, oysters were entrained by 12?L:12 D conditions. Then, free-running conditions (D:D and L:L) indicated that the most frequently observed period ranged from 20 to 28?h, the circadian range. That endogenous circadian rhythm was characterized as weak. Indeed, the period (τ) of the individual animals exhibited high plasticity in D:D and L:L, and the animals immediately followed a 4-h phase advance or delay. Additionally, C. gigas appeared as a dual organism: all oysters were nocturnal at the beginning of the laboratory experiment (January), whereas they were diurnal at the end (March). That shift was progressive. Comparison with a full-year in situ record showed the same behavioral duality as observed in the laboratory: the animals were nocturnal in autumn–winter and diurnal in spring–summer. The significant advantage of a plastic and dual circadian rhythm in terms of adaptability in a highly changing environment is discussed. (Author correspondence: d.tran@epoc.u-bordeaux1.fr)     

Entrainment to Light of Circadian Activity Rhythms in Tench (Tinca tinca)

The present article analyzes locomotor activity rhythms in Tinca tinca. To that end, three different experiments were conducted on 24 animals (20 g body weight) kept in pairs in 60‐liter aquaria fitted with infrared sensors connected to a computer to continuously record fish movements. The first experiment was designed to study the endogenous circadian clock under free‐running conditions [ultradian 40:40 min LD pulses and constant dark (DD)] and after shifting the LD cycle. Our results demonstrate that tench has a strictly nocturnal activity pattern, an endogenous rhythm being evident in 45.8% of the fish analyzed. The second experiment was conducted to test the influence of different photoperiods (LD 6:18, 12:12, 18:6, and 22:2) on locomotor activity, the results showing that even under an extremely long photoperiod, tench activity is restricted to dark hours. The third experiment examined the effect of light intensity on locomotor activity rhythms. When fish were exposed to decreasing light intensities (from 300:0 lux to 30:0, 3:0, and 0.3:0 lux) while maintaining a constant photoperiod (LD 12:12), the highest percentage of locomotor activity was in all cases associated with the hours of complete darkness (0 lux). In short, our results clearly show that (a) tench is a species with a strictly nocturnal behavior, and (b) daily activity rhythms gradually entrain after shifting the LD cycle and persist under free‐running conditions, pointing to their circadian nature. However, light strongly influences activity rhythms, since (c) the length of the active phase is directly controlled by the photophase, and (d) strictly nocturnal behavior persists even under very dim light conditions (0.3 lux). The above findings deepen our knowledge of tench behavior, which may help to optimize the aquacultural management of this species, for example, by adjusting feeding strategies to their nocturnal behavior.     

Azadirachtin affects the circadian rhythm of locomotion in Leucophaea maderae

Abstract

Azadirachtin shortens the period length of the locomotor activity rhythm in the circadian rhythm of Leucophaea maderae and induces splitting of this rhythm in two components in about 40% of the animals. The phase relationship between the two components is 180°. Both shortening of period and splitting are more pronounced in animals possessing longer periods before the injection of azadirachtin.     

Temperature and light effects on the circadian rhythm and locomotory activity of the plains garter snake (Thamnophis radix hayendi)

Abstract

The Locomotory activity of the Plains Garter snake was determined under L/D: 12/12 conditions at five constant temperatures and three light intensities during the light period. The snakes were diurnal at low temperatures with nocturnal activity increasing in various amounts at higher temperatures. The different light intensities had relatively small effects on the activity rhythm.

Activity was recorded under four constant light conditions at five constant temperatures and the characteristics of the free‐running rhythm measured. A comparison of the characteristics of the free‐running rhythm to Aschoff's circadian rule indicates that this snake is an exception to this rule.

Increase light intensity decreased total activity under all conditions. Under a L/D: 12/12 cycle the decrease in activity was more pronounced during the dark period than the light period.

It is suggested that crepuscular or nocturnal activity shown by snakes at high temperatures may be an effect the temperature level has on the biological clock and activity controlling mechanisms rather than temperature selection by the snake.     

Possible Evidence for Shift Work Schedules in the Media Workers of the Ant Species Camponotus compressus

The locomotor activity rhythm of the media workers of the ant species Camponotus compressus was monitored under constant conditions of the laboratory to understand the role of circadian clocks in social organization. The locomotor activity rhythm of most ants entrained to a 24 h light/dark (12:12 h; LD) cycle and free-ran under constant darkness (DD) with circadian periodicities. Under entrained conditions about 75% of media workers displayed nocturnal activity patterns, and the rest showed diurnal activity patterns. In free-running conditions these ants displayed three types of activity patterns (turn-around). The free-running period (τ) of the locomotor activity rhythm of some ants (10 out of 21) showed period lengthening, and those of a few (6 out of 21) showed period shortening, whereas the locomotor activity rhythm of the rest of the ants (5 out of 21) underwent large phase shifts. Interestingly, the pre-turn-around τ of those ants that showed nocturnal activity patterns during earlier LD entrainment was shorter than 24 h, which became greater than 24 h after 6–9 days of free-run in DD. On the other hand, the pre-turn-around τ of those ants, which exhibited diurnal patterns during earlier LD entrainment, was greater than 24 h, which became shorter than 24 h after 6–9 days of free-run in DD. The patterns of activity under LD cycles and the turn-around of activity patterns in DD regime suggest that these ants are shift workers in their respective colonies, and they probably use their circadian clocks for this purpose. Circadian plasticity thus appears to be a general strategy of the media workers of the ant species C. compressus to cope with the challenges arising due to their roles in the colony constantly exposed to a fluctuating environment.