Circadian rhythm of light sensitivity in the beetle <Emphasis Type="Italic">Coccinella septempunctata</Emphasis> (Coleoptera,Coccinellidae): Effects of illumination and temperature

Beetles Coccinella septempunctata L. are active only during daylight. It is demonstrated that sensitivity to light, the photopreferendum, and locomotor activity are regulated by endogenous circadian oscillators. The percentage of beetles that became active during the first 10 min after light-on was determined. Sensitivity to light (100, 1000 or 7000 lx) reached the maximum in the daytime (period of activity) and the minimum at night (resting period) irrespective of temperature (17 or 26°C). Illumination and temperature serve as modifying factors for the pattern and amplitude of the circadian rhythm of light sensitivity.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly,Delia antiqua

The influence of pupal diapause on adult eclosion rhythm of Delia antiqua was investigated. When non-diapause and diapause pupae were exposed to various photoperiods at 15, 20 and 25 °C, both of them emerged as adults close to the light-on time, but the phase of eclosion varied with photoperiod and temperature. Moreover, there was a significant difference in the eclosion time between non-diapause and diapause pupae; the eclosion peak of diapause pupae was earlier than that of non-diapause pupae. When non-diapause and diapause pupae were transferred to constant darkness (DD) after having experienced LD 12:12 at 15, 20 and 25 °C, both showed circadian rhythmicity in eclosion. Although the free-running period (τ) decreased slightly as temperature increased in both non-diapause and diapause pupae, the latter tended to show shorter τ than the former. This observation suggests that the observed difference in eclosion time in LD cycles between non-diapause and diapause pupae is due to differences in τ.     

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.     

Die Steuerung einer gezeitenparallelen Schlüpfrhythmik nach dem Sanduhr-Prinzip

Summary The arctic population of the intertidal midge Clunio marinus (location: Tromsö, Norway) shows a tidal rhythm of emergence (period: 12.4 hours) in midsummer. The emergence time exactly coincides with the initial exposure of the habitat during the ebb.When the animals were bred in a 24 hour light-dark cycle involving 16 hours of light, emergence occurred mainly 10–11 hours after light-on. When the animals were subsequently placed under constant light, no rhythm could be detected. When constant light was interrupted by a single period of 6 hours of darkness, only one peak of emergence was evoked, again 10–11 hours after light-on. Similar results were observed when in constant darkness a single period of 6 hours of lower temperature was offered.The mechanism of control differs from that of a southern population (location: St. Jean-de-Luz, France) which has a circadian clock mechanism and shows a free-running rhythm of emergence in constant light. It is postulated that the tidal rhythm of the Tromsö population is controlled by an hour-glass mechanism which starts its run of at least 10–11 hours during the preceding ebb.     

Pineal melatonin rhythms in the lizard Anolis carolinensis: I. Response to light and temperature cycles

Both light and temperature can influence the pineal's synthesis of the indoleamine melatonin. An investigation of the effects of light and temperature cycles on the pineal melatonin rhythm (PMR) showed the following: (1) Both daily light cycles and daily temperature cycles could entrain the PMR; melatonin levels peaked during the dark phase of a light-dark cycle or the cool phase of a temperature cycle. (2) The PMR could be entrained by a temperature cycle as low as 2 degrees C in amplitude in lizards held in constant light or constant darkness. (3) The length of the photoperiod or thermoperiod affected the phase, amplitude, or duration of the PMR. (4) When presented together, the effects of light and temperature cycles on the PMR depended on the phase relationship between the light and temperature cycles, as well as on the strength of the entraining stimuli, such as the amplitude of the temperature cycle. (5) Exposure to a constant cold temperature (10 degrees C) eliminated the PMR, yet a rhythm could still be expressed under a 24-hr temperature cycle (32 degrees C/10 degrees C), and the rhythm peaked during the 10 degrees C phase of the cycle. (6) A 6-hr dark pulse presented during the day did not elicit a premature rise in melatonin levels. These studies show how environmental stimuli can control the pineal rhythm of melatonin synthesis and secretion. Previous studies have supported a model in which the lizard's pineal acts as a circadian pacemaker within a multioscillator circadian system, and have implicated melatonin as a hormone by which the pineal may communicate with the rest of the system. The lizard pineal, therefore, may act as a photo- and thermoendocrine transducer translating light and temperature information into an internal cue in the form of the PMR. The PMR, in turn, may control the phase and period of circadian clocks located elsewhere, insuring that the right internal events occur at the right time of day.     

The Circadian Rhythm of Body Temperature of the Horse

Rectal temperature of 10 female adult horses was recorded every 2 h for 10 consecutive days under a natural winter photoperiod (9 h of light and 15 h of darkness per day). A robust daily rhythm of body temperature was observed in all animals. The rhythm had a mean level of 38.3°C and a range of excursion of 1.0°C. Temperature started its daily ascent at dawn each day and reached a maximum 14 hours later. Body temperature of 5 of the horses was studied for 10 more days under constant illumination. The rhythm persisted under this condition, although with a slightly longer period of 24.2 h, which confirms the endogenous nature of the rhythm. Despite the fact that the body size of the horse is several orders of magnitude greater than that of rodents, the various parameters of the body temperature rhythm of the horse are similar to those of several species of rodents previously studied.     

Circadian and circatidal locomotory rhythms in the intertidal beetle Thalassotrechus barbarae (Horn): Carabidae

Thalassotrechus barbarae (Horn) is a member of the intertidal crevice fauna. It forages and mates at night outside the crevice but only during periods of low water. Exogenous stimuli probably inhibit emergence and activity when conditions are not favourable but the main timing of activity is endogenously controlled. Under a LD 15:9 regime (270 lux, tungsten light) the insects were active only during the dark period. Under constant conditions (15–16 °C, 0.05 lux) the beetles showed a circatidal and circadian rhythm of locomotory activity. The circadian rhythm, which has an estimated period of 23.9 h, is quite stable, persisting for at least 7 days. The circatidal rhythm persists for 3 days suggesting that it is subordinate to the dominant circadian rhythm; it probably modifies the latter by inhibiting activity during periods of nocturnal high tides. A possible Zeitgeber for the circatidal rhythm is water movement which, like the probable stimulus entraining the circadian rhythm (light), is capable of being perceived by the eyes of this insect.     

Seasonal changes in entrainment cues for the circadian rhythm of the supratidal amphipod Talorchestia longicornis

The supratidal amphipod Talorchestia longicornis Say has a circadian rhythm in activity, in which it is active on the substrate surface at night and inactive in burrows during the day. The present study determined: (1) the circadian rhythms in individual versus groups of amphipods; (2) the range of temperature cycles that entrain the circadian rhythm; (3) entrainment by high-temperature cycles versus light?:?dark cycles, and (4) seasonal substrate temperature cycles. The circadian rhythm was determined by monitoring temporal changes in surface activity using a video system. Individual and groups of amphipods have similar circadian rhythms. Entrainment occurred only to temperature cycles that included temperatures below 20°C (10–20, 15–20, 17–19, 15–25°C) but not to temperatures above 20°C (20–25, 20–30°C), and required only a 2°C temperature cycle (17–19°C). Diel substrate temperatures were above 20°C in the summer and below 20°C during the winter. Upon simultaneous exposure to a diel high-temperature cycle (20–30°C) and a light?:?dark cycle phased differently, amphipods entrained to the light?:?dark cycle. Past studies found that a temperature cycle below 20°C overrode the light?:?dark cycle for entrainment. The functional significance of this change in entrainment cues may be that while buried during the winter, the activity rhythm remains in phase with the day?:?night cycle by the substrate temperature cycles. During the summer, T. longicornis switches to the light?:?dark cycle for entrainment, perhaps as a mechanism to phase activity precisely to the short summer nights.     

Effect of photoperiod and thermoperiod on the eclosion rhythm ofTrichogramma evanescens

The dynamics of adult eclosion inTrichogramma evanescens Westw. were studied under (1) constant light and temperature of 20 °C, (2) photoperiods L12:D12 and L16:D8 at 20 °C, (3) thermoperiod 4 h 27 °/20 h 20 °C at constant light, (4) joint action of photo- and thermoperiod. The emergence was arhythmic in constant light combined with constant temperature, while a sharp monophasic rhythm was observed with the isolated action of photo- or thermoperiod. The ‘light-on’ and ‘temperature step-up’ signals were shown to act in one direction. When both signals were combined, they manifested themselveses competing entraining stimuli which, in turn, revealed an apparent individual variation in relative reactivity to the light and temperature signals. Some perspectives which follow from these observations are discussed.     

Adult emergence rhythm of the egg-parasitoid Telenomus busseolae

The adult emergence rhythm of Telenomus busseolae, an egg parasitoid of Sesamia nonagrioides, was examined when parasitoids were exposed to different light-dark regimes. Most of the adult parasitoids emerged throughout the whole period of the photoperiodic cycle. Peak male emergence occurred 2–5 hours earlier than that of females. Adult emergence was asynchronous in continuous darkness or light. However, regimes of alternative light and dark phases such as L4:D20, L8:D16, L12:D12, L16:D8 and L20:D4 h generated a population rhythm with a period length of 24 hours. The peak of the emergence activity moves from the scotophase to the middle of the photophase with an increase of the photophase from 4 to 20 h. Rhythmical activity of adults was synchronised within 2 cycles when immature stages of parasitoid grow under continuous light conditions (LL) and then transferred to L12:D12. Moreover, emergence rhythm persisted and continued in a free-run with a period length of less than 24 hours by transferring a rhythmic culture from L12:D12 h to LL or RR (continuous red light) conditions, indicating the existence of a circadian rhythm. The ecological implications of the expression rhythm relate to better survival of the parasitoids.     

Photoperiodic Control of Flowering in Dark-Grown Seedlings of Pharbitis nil Choisy : The Effect of Skeleton and Continuous Light Photoperiods

The control of night-break timing was studied in dark-grown seedlings of Pharbitis nil (Choisy cv. Violet) following a single continuous or skeleton photoperiod. There was a rhythmic response to a red (R) interruption of an inductive dark period, and the phasing of the rhythm was influenced by the preceding light treatment.

Following a continuous white light photoperiod of 6 hours or less, the points of maximum inhibition of flowering were constant in real time. Following a continuous photoperiod of more than 6 hours, maximum inhibition occurred at 9 and 32.5 hours after the end of the light period. The amplitude of the rhythm during the second circadian cycle was much reduced following prolonged photoperiods.

Following a skeleton photoperiod, the time of maximum sensitivity to a R interruption was always related to the second pulse of the skeleton, R₂, with the first point of maximum inhibition of flowering occurring after 12 to 18 hours and the second after 39 hours. Without a second R pulse, the time of maximum sensitivity to a R interruption was related to the initial R₁ pulse. A `light-off' or dusk signal was not mimicked by a R pulse ending a skeleton photoperiod; such a pulse only generated a `light-on' signal and initiated a new rhythm.

It is concluded that the timing of sensitivity to a R interruption of an inductive dark period in Pharbitis nil is controlled by a single circadian rhythm initiated by a light-on signal. After 6 hours in continuous white light, the phase of this rhythm is determined by the transition to darkness. Following an extended photoperiod, the timing characteristics were those of an hourglass; this seemed to be due to an effect on the coupling or expression of a single circadian timer during the second and subsequent cycles, rather than to the operation of a different timing mechanism.

In addition to the effects on timing, the photoperiod affected the magnitude of the flowering response.

     

Annual oscillation of preferred temperature in the freshwater snail Lymnaea auricularia: effect of light and temperature

The thermal preference of the freshwater snail Lymnaea auriculria (Gastropoda: Pulmonata), measured 49 times over 3 years, oscillated around a mean of 19·3°C, with an amplitude of 13·4°C. This oscillation was significantly phase-linked to both the natural photoperiod and natural ambient temperature. Lymnaea hatched and maintained in constant conditions of temperature (21°C) and photoperiod (12 h) over 2 years showed a constant thermal preference of 19·8±1·4°C. The preference was maintained between 19·5 and 20·4°C when the snails were kept at 5, 15, 20 and 27°C and in photoperiods of 8 and 16 h. In a changing artificial photoperiod which followed an annual cycle, the preference fluctuated about a mean of 19·3°C with an amplitude of 3·9°C. When the photoperiod was constant but the temperature oscillated the preference remained constant. Thus the circannual cycle seems to be an exogenous oscillation entrained by the photoperiod.     

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).     

Photocontrol of Dark Circadian Rhythms in Stomata of Phaseolus vulgaris L

Stomatal diffusion resistance in primary leaves of Phaseolus vulgaris L. which had been grown in light:dark cycles followed a marked circadian rhythm when the plants were transferred to continuous darkness. Reentrainment of the rhythm required more than one inductive change in photoperiod. The phasing of the rhythm of dark stomatal opening was contolled primarily by the light-on (dawn) signal, whereas the rhythm of dark closure was related to the light-off (dusk) signal. The evidence points to a dual control of the circadian clock in which a product of photosynthesis plays a major role. No evidence for phytochrome involvement in the phasing of the rhythm was found. An influence of phytochrome on the amplitude of the stomatal rhythm was observed in which removal of phytochrome-far-red absorbing form caused rapid damping.     

Parametric and nonparametric entrainment of circadian locomotor rhythm in the Japanese honeybee Apis cerana japonica

The circadian rhythm of locomotor activity in the Japanese honeybee Apis cerana japonica was studied to determine the involvement of parametric and/or nonparametric entrainment. The rhythm was entrained to a skeleton photoperiod in which a 1-h first light pulse was imposed in the morning along with a second light pulse in the evening, as well as to a complete photoperiodic regime (LD 12:12). However, the timing of peak activity relative to the lights-off in the evening in the skeleton photoperiod was earlier than that in the complete photoperiod. A single daily light pulse in the evening entrained the rhythm, whereas a daily light pulse in the morning allowed free-running as in constant darkness. The free-running period (τ) of locomotor activity in constant light became longer as the light intensity increased. A Winfree's type I phase response curve of the locomotor activity rhythm was obtained using a single 1-h light pulse. The results suggest that both parametric and nonparametric entrainment are involved in the circadian rhythm of individual locomotor activity in this honeybee.     

Effects of Temperature,Photoperiod, and Light Intensity on the Eclosion Rhythm of the High-Altitude Himalayan Strain of Drosophila ananassae

Eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae from Badrinath (altitude 5123 m) was temperature-dependent and at 21°C, it was entrained by cycles of 12 h light: 12 h darkness (LD 12:12) and free-ran in constant darkness, however, it was arrhythmic at 13°C or 17°C under identical experimental conditions (Khare, P. V., Barnabas, R. J., Kanojiya, M., Kulkarni, A. D., Joshi, D. S. (). Temperature dependent eclosion rhythmicity in the high altitude Himalayan strains of Drosophila ananassae. Chronobiol. Int. 19:1041–1052). The present studies were designed to see whether or not these strains could be entrained at 13°C, 17°C, and 21°C by two types of LD cycles in which the photoperiod at 100 lux intensity varied from 6 h to 18 h, and the light intensity of LD 14:10 cycles varied from 0.001 lux to 1000 lux. All LD cycles entrained this strain at 21°C but not at 13°C or 17°C. These results demonstrate that the entrainment of eclosion rhythm depends on the ambient temperature and not on the photoperiod or light intensity of LD cycles. Thus the temperature has taken precedence over the light in the entrainment process of eclosion rhythm of the high altitude Himalayan strain of D. ananassae. This may be the result of natural selection in response to the environmental temperature at Badrinath that resembles that of the sub-Arctic region but the photoperiod or light intensity are of the subtropical region.     

Effects of temperature on the development and circannual control of pupation in the carpenter moth, <Emphasis Type="Italic">Cossus insularis</Emphasis> (Lepidoptera: Cossidae), reared on an artificial diet

The effects of temperature on larval development and the timing of pupation in the carpenter moth, Cossus insularis (Staudinger) (Lepidoptera: Cossidae) were examined by artificial rearing under different temperatures and the same photoperiod (15L:9D). Although C. insularis pupated and emerged at 20, 25, and 30 °C, the pupation rate was lower at 20 °C than at 25 and 30 °C. These results suggest that the optimum temperature range for preadult development is 25–30 °C. The duration of larval development was about 260 days for the first pupation group at 25 and 30 °C, and at least 600 days at 20 °C. Therefore, the C. insularis generation time was 2 years or more, as the total effective temperature for development from hatching to the pupal stage was unlikely to be reached within 1 year in Tokushima Prefecture. The second group pupated at 25 °C, about 200 days after the first group. This periodicity of pupation was likely due to the free-running period of the circannual rhythm. Furthermore, although only the first group pupated at 30 °C, the peak was almost synchronous with the first group at 25 °C. These results indicate that the timing of the first pupation group in C. insularis is temperature compensated. Therefore we propose that the presence of an endogenous rhythm during the development of C. insularis is evidence for a circannual rhythm related to the timing of pupation.     

Emergence rhythm and quality control in the laboratory and mass rearing of <Emphasis Type="Italic">Trichogramma</Emphasis> species (Hymenoptera: Trichogrammatidae)

The laboratory experiments showed that various parameters of the “quality” of Trichogramma telengai Sor. females that emerged from a batch of simultaneously parasitized eggs of the grain moth Sitotroga cerealella Oliv. were significantly dependent on the day and circadian time (i.e., time from light-on) of emergence: the later the females emerged, the smaller were their size, fecundity, and life span. The difference in size and in fecundity between individuals emerged on different days constituted up to 20% and 70% of the mean, correspondingly. Differences between the early (emerged during 2 h after the light-on), middle (emerged from 2 to 3 h after the lighton), and late (emerged from 3 to 6 h after the light-on) fractions of females which emerged on the same day were also significant (about 5% in size and about 25% in fecundity). Based on these results, we conclude that the day and circadian time of emergence should be taken into account in elaboration of the methods of laboratory experiments and of the protocols for Trichogramma quality tests in mass rearing.     

Interacting effect of thermoperiod and photoperiod on the eclosion rhythm in the onion fly, Delia antiqua supports the two-oscillator model

Daily light and temperature cycles entrain adult eclosion rhythms in many insect species, but little is known about their interaction. We studied this problem in the onion fly, Delia antiqua. Pupae were subjected to various combinations of a photoperiod of 12L:12D and thermoperiods. The thermoperiods consisted of 12 h warm phase (W) and 12 h cool phase (C), giving a mean temperature of 25 °C with different temperature steps of 8, 4 and 1 °C. As the phase relation of the two Zeitgebers was varied, the phase of eclosion rhythm was shifted, depending on the phase angle with the light cycle and the amplitude of the temperature cycle. When the temperature step in the thermoperiod was 8 °C (WC 29:21 °C), the eclosion rhythm was entrained mainly to thermoperiod rather than photoperiod. In the regime with a 4 °C temperature step (WC 27:23 °C), both thermoperiod and photoperiod affected eclosion rhythm, and a phase jump of the eclosion rhythm occurred when the warm phase of thermoperiod was delayed 15-18 h from light-on. In regimes with a 1 °C temperature step (WC 25.5:24.5 °C), the eclosion rhythm was completely entrained to photoperiod. The observed interacting effect of light and temperature cycle on the eclosion rhythm in D. antiqua can be explained by the two-oscillator model proposed by Pittendrigh and Bruce (1959).     

Diapause induction in the oblique-banded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae): Role of photoperiod and temperature

Induction of diapause in the larval stage of the oblique-banded leafroller, Choristoneura rosaceana (Harris), was found to be dependent on both photoperiod and temperature. At constant temperatures of 24, 20 and 16°C, short photoperiods induced diapause. The critical photoperiod was between 14–15 h of light per day at 20 and 16°C. At 14 h light: 10 h dark, all larvae expressed diapause. Temperature had a modifying effect, and slightly shifted the larval response to diapause-inducing photoperiods. High constant temperatures of 28°C and above induced diapause in some individuals (< 20%), while fluctuating temperatures of 32 and 16°C in a 12-h cycle resulted in 67% diapause induction, suggesting that diapause could also be induced by fluctuating temperatures, particularly if the higher temperature exceeds 25°C.The first- and the second-instar larvae were the only two stages sensitive to diapause induction. Exposure of adult, egg and third, fourth, and fifth-larval instars to diapause-inducing conditions did not produce diapause. Although diapause was induced in the first or the second instars, it was always expressed in the third or fourth instar.