Ontogeny of the Locomotor Activity Rhythm in the Common Marmoset (Callithrix jacchus)

The ontogeny of locomotor activity rhythm in the common marmoset was studied in three animals, observed during infant and juvenile stages, and in adult age. Animals were kept with their families in outdoor cages under natural temperature, humidity and light cycles. Data were collected from sunrise to sunset, three consecutive days a week, at 5 min intervals randomly distributed in the clock hours, and were recorded as the total of arbitrary cage sections traveled by the animal each interval. Animal 3 was observed continuously one day a week in order to detect less than 2 h period harmonic components. Animals' weekly data series were analyzed by Fourier analysis and Siegel's test to detect significant harmonic components. Results showed a main 24 h period com ponent for all records and a secondary 8 h period component in at least 34% of animal's week data series. The power content of the 24 h component showed an increase with age, reaching some stability near the 16th week of life suggesting that this component is mature at the end of the animal's infant stage. However, for the 8 h component an oscillating pattern was observed following the environmental annual temperature cycle; this may indicate a seasonal modulation of daily locomotor activity profiles.     

Ontogeny of the Locomotor Activity Rhythm in the Common Marmoset (Callithrix jacchus)

The ontogeny of locomotor activity rhythm in the common marmoset was studied in three animals, observed during infant and juvenile stages, and in adult age. Animals were kept with their families in outdoor cages under natural temperature, humidity and light cycles. Data were collected from sunrise to sunset, three consecutive days a week, at 5 min intervals randomly distributed in the clock hours, and were recorded as the total of arbitrary cage sections traveled by the animal each interval. Animal 3 was observed continuously one day a week in order to detect less than 2 h period harmonic components. Animals' weekly data series were analyzed by Fourier analysis and Siegel's test to detect significant harmonic components. Results showed a main 24 h period com ponent for all records and a secondary 8 h period component in at least 34% of animal's week data series. The power content of the 24 h component showed an increase with age, reaching some stability near the 16th week of life suggesting that this component is mature at the end of the animal's infant stage. However, for the 8 h component an oscillating pattern was observed following the environmental annual temperature cycle; this may indicate a seasonal modulation of daily locomotor activity profiles.     

Seasonality of the endogenous activity rhythm in Talitrus saltator (Montagu) from a sandy beach in northeastern Tunisia

The endogenous activity of the sandhopper Talitrus saltator (Montagu) has been investigated in a population from a relatively exposed beach in northeast Tunisia. The animals were found to exhibit a nocturnal circadian rhythm of locomotor activity, with no evidence of a circatidal component. The rhythm was monitored in individual animals over the four seasons, under constant laboratory conditions and seasonal variation in free-running period; the signal-to-noise ratio and waveform of the rhythm have been investigated, as well as the incidence of rhythmic animals in the population. The variation in these rhythm parameters is considered in relation to changes in environmental conditions prevailing at the site of collection.     

In situ studies on heart rate and locomotor activity in the freshwater crayfish, Astacus astacus (L.) in relation to natural fluctuations in temperature and light intensity

1. By the aid of a computer technique, the in situ variations in heart rate and locomotor activity were recorded continuously for 7 days in sixteen individuals of the crayfish, Astacus astacus (Linnaeus 1758), in association with natural changes in water temperature and light intensity.
2. All sixteen crayfish investigated were found to express circadian rhythmicity in heart rate with a periodicity of ≈ 24 h. For 88% of the animals investigated, rhythmicity was significant ( P < 0.05). Ninety‐three per cent of the crayfish showed circadian rhythmicity in locomotor activity with a 24 ± 2 h periodicity and, for 67% of the animals, this rhythmicity was significant ( P < 0.05). In general, the expression of circadian rhythms was associated with nocturnal behaviour, heart rates and locomotor activity levels being higher at night than by day.
3. A positive correlation was observed between heart rate and locomotor activity. Temperature and light intensity exerted positive and negative influences on heart rate in A. astacus , respectively.
4. In the first experiment, 84% of the variation in heart rate could be explained by the changes in locomotor activity, temperature and light intensity. In the second experiment 35% of the variation in the heart rate was explained using these parameters.     

Rhythmic 24 h Variation of Core Body Temperature and Locomotor Activity in a Subterranean Rodent (Ctenomys aff. knighti), the Tuco-Tuco

The tuco-tuco Ctenomys aff. knighti is a subterranean rodent which inhabits a semi-arid area in Northwestern Argentina. Although they live in underground burrows where environmental cycles are attenuated, they display robust, 24 h locomotor activity rhythms that are synchronized by light/dark cycles, both in laboratory and field conditions. The underground environment also poses energetic challenges (e.g. high-energy demands of digging, hypoxia, high humidity, low food availability) that have motivated thermoregulation studies in several subterranean rodent species. By using chronobiological protocols, the present work aims to contribute towards these studies by exploring day-night variations of thermoregulatory functions in tuco-tucos, starting with body temperature and its temporal relationship to locomotor activity. Animals showed daily, 24 h body temperature rhythms that persisted even in constant darkness and temperature, synchronizing to a daily light/dark cycle, with highest values occurring during darkness hours. The range of oscillation of body temperature was slightly lower than those reported for similar-sized and dark-active rodents. Most rhythmic parameters, such as period and phase, did not change upon removal of the running wheel. Body temperature and locomotor activity rhythms were robustly associated in time. The former persisted even after removal of the acute effects of intense activity on body temperature by a statistical method. Finally, regression gradients between body temperature and activity were higher in the beginning of the night, suggesting day-night variation in thermal conductance and heat production. Consideration of these day-night variations in thermoregulatory processes is beneficial for further studies on thermoregulation and energetics of subterranean rodents.     

Locomotor Activity Rhythm in Free-ranging Common Marmosets (Callithrix jacchus)

Locomotor activity rhythm in the common marmoset has been well described and characterized in captivity, but there is no information about rhythmic aspects of this behavior in free-ranging conditions. To investigate if the locomotor activity rhythm in free-ranging common marmosets is similar to that found in captive common marmosets, we observed reproductive animals from two groups that inhabited at the Experimental Forestry Station, in northeastern Brazil (6°5'S, 35°12'W). From December 1992 to October 1993 we recorded the frequency of locomotor activity by focal animal sampling. The records of locomotor activity were submitted to spectral analysis and to the Cosinor test. Common marmosets showed an average duration of the active phase of 11:37 h ± 13.8 min. Similar to recorded in captive common marmosets, circadian rhythmicity was found with peaks in the morning, and in the afternoon, characterizing a bimodal pattern with peaks separated by 8 hours. The presence of a rhythmic pattern in the locomotor activity in free-ranging and captive common marmosets suggests that this pattern is not determined by the environmental conditions in captivity, but it has a endogenous component that play an important role for adaptation of this species to different conditions.     

Behavioural Rhythms of Land Snails in the Field

Circadian and circannual behavioural rhythms of Helix are described in the field. Laboratory studies demonstrate the existence of an endogenous component for these rhythms. The effects of the environmental factors on the snail activities are multiple: light/dark and cold/warm cycles synchronise the behavioural rhythms; a masking effect is observed when it rains since the animals are active throughout the 24 h day; high temperature and low relative humidity cause a complete cessation of activities. In addition, social interactions between and within species can modulate the shape of the rhythms driven by the biological clock.     

Effects of a seven-day continuous infusion of ropivacaine on circadian rhythms in the rat

The present study was conducted to evaluate the effect of a 7 d continuous infusion of ropivacaine on the 24 h rhythms of body temperature, heart rate, and locomotor activity. After an initial 7 d baseline, rats were randomly divided into two groups of 4 rats each to receive ropivacaine or saline via an osmotic pump for 7 consecutive days. The pumps were removed thereafter and observed during a 7 d recovery span. The studied circadian rhythms were measured by radiotelemetry throughout each of the 7 d periods. An additional group of 4 rats was studied under the same experimental conditions to assess the plasma levels of ropivacaine on days 3 and 8 following pump implantation. Our results indicate that ropivacaine does not induce loss of the circadian rhythms of body temperature, heart rate, or locomotor activity; a prominent period of 24 h was found for all variables in all animals, before, during, and after ropivacaine treatment. However, ropivacaine treatment did modify some characteristics of the rhythms; it increased the MESOR (24 h mean) of the heart rate and locomotor activity rhythms and advanced the acrophase (peak time) of the locomotor activity circadian rhythm. The present study indicates that the circadian rhythms of heart rate and locomotor activity are modified after continuous infusion of ropivacaine, which is of particular interest, given the potential cardiotoxicity of this local anesthetic agent.     

Seasonal variations in circadian rhythms coincide with a phase of sensitivity to short photoperiods in the European hamster

European hamsters (Cricetus cricetus) show pronounced seasonal changes in their physiology and behavior. The present study provides a detailed analysis of the temporal relationship between seasonal cycles of reproduction and body mass and seasonal changes of two circadian parameters, i.e., locomotor activity and 6-sulphatoxymelatonin (aMT6s) excretion, in individual animals kept under natural light conditions. Our results demonstrate a characteristic pattern of locomotor activity and aMT6s excretion observed around the summer solstice, i.e., from mid-May to mid-July. During this time, locomotor activity was characterized by a high level of activity and an early activity onset, while the nightly elevation of melatonin was reduced to baseline levels. These seasonal changes in aMT6s excretion and locomotor activity were only loosely related to changes in the reproductive status of the animals, but correlated well with a period of the annual cycle during which the animals were sensitive to short days. They may therefore reflect a specific state of the circadian pacemaker system within the SCN and can thus be a valuable tool to further characterize molecular and physiological mechanisms of photoperiodic time measurements in European hamsters.     

Locomotor activity rhythm of Talitrus saltator (Crustacea,Amphipoda) on a progradating sandy beach

In the Maremma Natural Park (Grosseto, Italy), the Collelungo beach exhibits a clear morphodynamics gradient, resulting in a severe erosion to a gradual accretion along the shoreline. Here, three sub-populations of the sandhopper Talitrus saltator (Montagu) (Crustacea, Amphipoda) were studied to highlight eventual intra- and inter-population variation of the endogenous locomotor rhythm. Individual activity recordings were carried out for 21 days in constant darkness and controlled temperature and humidity conditions. The variation of the free-running period was analysed at individual and sub-population levels, and the dependence on intrinsic (individual features) and extrinsic (habitat of origin and season) factors was analysed. A seasonal variation was highlighted, related to the seasonal spontaneous activity of the species. In summer and autumn, a significant correlation between the behavioural variation in the sub-populations (period and definition of the period) and beach physical parameters (slope and width) defined the dependence of the behavioural gradient on the environmental gradient. The observed relationship may represent an adaptation to the local coastline dynamics, suggesting the importance of a plastic behaviour as adaptive response to a variable environment.     

Diurnal flight behavior of Ichneumonoidea (Insecta: Hymenoptera) related to environmental factors in a tropical dry forest

The biology and behavior of insects are strongly influenced by environmental conditions such as temperature and precipitation. Because some of these factors present a within day variation, they may be causing variations on insect diurnal flight activity, but scant information exists on the issue. The aim of this work was to describe the patterns on diurnal variation of the abundance of Ichneumonoidea and their relation with relative humidity, temperature, light intensity, and wind speed. The study site was a tropical dry forest at Ría Lagartos Biosphere Reserve, Mexico; where correlations between environmental factors (relative humidity, temperature, light, and wind speed) and abundance of Ichneumonidae and Braconidae (Hymenoptera: Ichneumonoidea) were estimated. The best regression model for explaining abundance variation was selected using the second order Akaike Information Criterion. The optimum values of temperature, humidity, and light for flight activity of both families were also estimated. Ichneumonid and braconid abundances were significantly correlated to relative humidity, temperature, and light intensity; ichneumonid also showed significant correlations to wind speed. The second order Akaike Information Criterion suggests that in tropical dry conditions, relative humidity is more important that temperature for Ichneumonoidea diurnal activity. Ichneumonid wasps selected toward intermediate values of relative humidity, temperature and the lowest wind speeds; while Braconidae selected for low values of relative humidity. For light intensity, braconids presented a positive selection for moderately high values.     

Light pulse effect on the locomotor activity rhythm of Talitrus saltator (Montagu) (Crustacea,Amphipoda)

The locomotor activity rhythm of the sandhopper Talitrus saltator (Amphipoda Talitridae) was investigated in Madfoun beach. The rhythm was monitored in individual and group animals during 21 days at constant temperature. During the first two weeks, animals were kept under light–dark cycle (d1–d7) and constant darkness (d8–d14). Light pulses of 2 h were applied, at the end of the experimental night, during the first 3 days of the third week (d15–d18). Then, constant darkness was restored for the rest of the experiment (d19–d21). Results revealed that Talitrus saltator individuals as well as groups concentrated their activities in experimental night under light–dark cycle and in the presence of pulses; whereas, a clear drift of activity is observed under constant darkness. Periodogram analysis showed the presence of circadian component whatever the recording type. An ultradian period was revealed in individual recording whatever the regimen, while for groups, this component appeared only under nLD cycle. Furthermore, the locomotor rhythm is more defined under nLD cycle for individuals and in constant darkness for groups.     

Nest Maintenance Activity of <Emphasis Type="Italic">Dinoponera quadriceps</Emphasis> in a Natural Environment

In social insects, task allocation can be more complex than workers merely falling into discrete task groups. Any activity performed by the colony cannot be fully understood in isolation from other activities because they may be interrelated. Investigating activities other than foraging is crucial to understanding the global functioning and organization of ant colonies. This study attempts to characterize the nest maintenance activity of the ponerine queenless ant, Dinoponera quadriceps, in its natural environment to determine the effects of environmental variables on the variations in both seasonal and daily rhythms and to discuss its differences and possible relationships to foraging. Four colonies of D. quadriceps were observed in an area of Atlantic Forest in northeastern Brazil. Data collection was performed over a period of 72 h every three months during an entire annual cycle. Nest maintenance activity in D. quadriceps colonies was observed during both the light and dark phases of the day. There was no significant difference between the day phases in the number of workers involved in this task. On the other hand, D. quadriceps colonies exhibited seasonal variation in nest maintenance activity, peaking in the early rainy season. The seasonal rhythm of nest maintenance was positively correlated with relative humidity and negatively correlated with prey availability and rainfall. Our results indicate the existence of an annual variation in the nest maintenance activity of D. quadriceps associated with environmental variables. However, it occurs equally both at night and day, countering the hypothesis that there is a daily rhythm.     

Circadian Locomotor Activity Under Artificial Light in the Freshwater Crab Pseudothelphusa americana

Long-term recordings of locomotor activity were obtained from intact freshwater crabs, Pseudothelphusa americana in constant darkness (DD), constant light (LL) and different light-dark (LD) protocols. Bimodal rhythms were typically observed in this crab when subjected to DD or LD, with bouts of activity anticipating lights-on and lights-off, respectively. Freerunning circadian rhythms were expressed in both DD and LL for longer than 30 days. In DD, we observed that some animals presented different period lengths for each activity component. During LL, activity was primarily unimodal, however spontaneous splitting of the rhythms were observed in some animals. When activity was recorded under artificial long days, the morning bouts maintained their phase relationship but the evening bouts changed their phase relationship with the Zeitgeber. Our results indicate that, bimodal locomotor activity rhythm in the crab Pseudothelphusa americana is variable among organisms. The characteristics of phase relationship with LD and responses to LL for morning and evening bouts, suggest that, locomotor activity could be driven by multiple oscillators, and that coupling between these oscillators may be regulated by light.     

Some behavioral effects of short-term exposure of rats to 2.45 GHz microwave radiation

Rats were tested for neurobehavioral alterations immediately after exposure to 2.45-GHz (CW) microwave radiation at 10 mW/cm2 for 7 h. Behavioral tests used were locomotor activity, startle to an acoustic stimulus and acquisition and retention of a shock-motivated passive avoidance task. Both horizontal and vertical components of locomotor activity were assessed in 5-min epochs for a period of 30 min using photoelectric detectors. Microwave-exposed animals exhibited less activity than sham-exposed animals. This was most evident during the last 10-15 min of the 30-min test session. Twenty identical acoustical stimuli (8 KHz, 110 dB) were delivered to each rat at 40-s intervals. The microwave-exposed animals were less responsive to the stimuli than sham-exposed animals. Microwave exposure had no effect on the retention of a passive avoidance procedure when tested at 1 week after training. Both the locomotor activity and acoustic startle data demonstrate that, under the conditions of this experiment, microwave exposure may alter responsiveness of rats to novel environmental conditions or stimuli.     

The activity and malate inhibition/stimulation of phosphoenolpyruvate-carboxylase in crassulacean-acid-metabolism plants in their natural environment

The effect of environmental conditions, temperature, relative humidity, and light, together with the regulation of PEPC (phosphoenolpyruvate-carboxylase) activity by malate and pH on CAM (crassulacean acid metabolism), was studied in members of the Mesembryanthemaceae in their natural environment, the southern Namib desert. It was found that during a 24 h period the characteristics of PEPC change. Before sunrise the activity is higher when measured at pH 7 than 8. With bright sunlight the activity measured at pH 7 drops to 20% of its pre-sunrise value, the activity only recovers gradually after malate disappearance and stays constant throughout the night. When measured at pH 8, PEPC shows an opposite behavior, i.e., activity increases in bright sunlight and declines as the pH 7 activity increases. A day-night oscillation in the capacity of malate to stimulate or inhibit PEPC was found. During the day malate inhibits about 90% of the PEPC activity at both pH 7 and 8. After sunset there is a sudden decrease in this inhibition and, at pH 8, malate stimulates the activity by 50%. At pH 7 the stimulation was less.Both stomatal conductance and malate formation were found to increase only when the relative humidity at night rose to 80%. Changes in the properties of the PEPC coincided with the exposure to bright sunlight and changes in leaf temperature. The importance of these metabolic and environmental controls on the regulation of CAM in the Mesembryanthemaceae will be discussed.Abbreviations CAM crassulacean acid metabolism - PEP phosphoenolpyruvate - PEPC PEP-carboxylase     

Temperature humidity index scenarios in the Mediterranean basin

The study was undertaken to describe the temperature humidity index (THI) dynamics over the Mediterranean basin for the period 1971–2050. The THI combines temperature and humidity into a single value, and has been widely used to predict the effects of environmental warmth in farm animals. The analysis was based on daily outputs of the temperature and relative humidity from the Max Planck Institute data using the Intergovernmental Panel on Climate Change Special Report Emission Scenario A1B. Data revealed a gradual increase of both annual and seasonal THI during the period under investigation and a strong heterogeneity of the Mediterranean area. In particular, the analysis indicated that Spain, southern France and Italy should be expected to undergo the highest THI increase, which in the last decade under study (2041–2050) will range between 3 and 4 units. However, only during summer months the area presents characteristics indicating risk of thermal (heat) stress for farm animals. In this regard, scenario maps relative to the summer season suggested an enlargement of the areas in the basin where summer THI values will likely cause thermal discomfort in farm animals. In conclusion, the study indicated that the Mediterranean basin is likely to undergo THI changes, which may aggravate the consequences of hot weather on animal welfare, performances, health and survival and may help farmers, nutritionists, veterinarians, and policy-makers to develop appropriate adaptation strategies to limit consequences of climate change for the livestock sector in the Mediterranean countries.     

Circadian Locomotor Activity Under Artificial Light in the Freshwater Crab Pseudothelphusa americana

Long-term recordings of locomotor activity were obtained from intact freshwater crabs, Pseudothelphusa americana in constant darkness (DD), constant light (LL) and different light-dark (LD) protocols. Bimodal rhythms were typically observed in this crab when subjected to DD or LD, with bouts of activity anticipating lights-on and lights-off, respectively. Freerunning circadian rhythms were expressed in both DD and LL for longer than 30 days. In DD, we observed that some animals presented different period lengths for each activity component. During LL, activity was primarily unimodal, however spontaneous splitting of the rhythms were observed in some animals. When activity was recorded under artificial long days, the morning bouts maintained their phase relationship but the evening bouts changed their phase relationship with the Zeitgeber. Our results indicate that, bimodal locomotor activity rhythm in the crab Pseudothelphusa americana is variable among organisms. The characteristics of phase relationship with LD and responses to LL for morning and evening bouts, suggest that, locomotor activity could be driven by multiple oscillators, and that coupling between these oscillators may be regulated by light.     

Effects of a Seven‐Day Continuous Infusion of Ropivacaine on Circadian Rhythms in the Rat

The present study was conducted to evaluate the effect of a 7 d continuous infusion of ropivacaine on the 24 h rhythms of body temperature, heart rate, and locomotor activity. After an initial 7 d baseline, rats were randomly divided into two groups of 4 rats each to receive ropivacaine or saline via an osmotic pump for 7 consecutive days. The pumps were removed thereafter and observed during a 7 d recovery span. The studied circadian rhythms were measured by radiotelemetry throughout each of the 7 d periods. An additional group of 4 rats was studied under the same experimental conditions to assess the plasma levels of ropivacaine on days 3 and 8 following pump implantation. Our results indicate that ropivacaine does not induce loss of the circadian rhythms of body temperature, heart rate, or locomotor activity; a prominent period of 24 h was found for all variables in all animals, before, during, and after ropivacaine treatment. However, ropivacaine treatment did modify some characteristics of the rhythms; it increased the MESOR (24 h mean) of the heart rate and locomotor activity rhythms and advanced the acrophase (peak time) of the locomotor activity circadian rhythm. The present study indicates that the circadian rhythms of heart rate and locomotor activity are modified after continuous infusion of ropivacaine, which is of particular interest, given the potential cardiotoxicity of this local anesthetic agent.     

Analysis of the locomotor activity of a nocturnal desert lizard (Reptilia: Gekkonidae: Teratoscincus scincus) under varying moonlight

1. This project seeks to identify determinants of the variation observed in the foraging behavior of predatory animals, especially in moonlight, using a lizard as a model. 2. Moonlight generally enhances the foraging efficiency of nocturnal visual predators and often depresses the locomotor activity of prey animals. Previous evidence has indicated for three different nocturnal species of smallish gecko lizards that they respond to moonlight by increasing their activity. 3. In this study some aspects of the foraging activity of the somewhat larger nocturnal psammophilous Teratoscincus scincus, observed near Repetek and Ashgabat, Turkmenistan, were significantly depressed by moonlight, while several confounding factors (sex, maturity, size, sand temperature, hour, prior handling and observer effect) were taken into account. 4. This behavioral difference may relate to the eye size of the various species. 5. Additionally, a novel method of analyzing foraging behavior shows that in this species the duration of moves increases the duration of subsequent stationary pauses. Measurement of locomotor speed, yielding an average speed of 220% of the maximum aerobic speed, indicates a need for these pauses. Secondarily, pause duration decreases the duration of subsequent moves, precluding escalation of move duration. 6. The results of this and related projects advocate the taking into account of physiological and environmental factors that may affect an animal's foraging behavior.