Body core temperature of rats subjected to daily exercise limited to a fixed time

 Several timed daily environmental cues alter the pattern of nycthemeral variations in body core temperature in rodents. The present study investigated the effect of timed exercise on variations of daily body core temperature. Male rats were housed in cages with a running wheel at an ambient temperature of 24° C with a 12:12 h light/dark cycle. Timed daily exercise rats (TEX) were allowed access to the wheel for 6 h in the last half of the dark phase, freely exercising rats (FEX) could run at any time, and sedentary rats (NEX) were not allowed to run. After a 3-week exercise period, all animals were denied access to the wheel. The intraabdominal temperatures (T _ab) and spontaneous activities of rats were measured for 6 days after the exercise period. The T _ab values of the TEX rats were significantly higher than those of the other two groups only in the last half of the dark phase, while T _ab in the FEX and NEX rats showed no significant difference. The specific T _ab changes in the TEX rats lasted for 2 days after the exercise period. Spontaneous activity levels were higher in the TEX rats than the FEX and NEX rats in the last half of the dark phase for 1 day after the exercise period. The results suggest that daily exercise limited to a fixed time per day modifies nycthemeral variations of body core temperature in rats so that the temperature increases during the period when the animals had previously exercised. Such a rise in body core temperature is partly attributed to an increase in the spontaneous activity level. Received: 13 November 1996 / Accepted: 8 January 1997     

Correlation between urinary pregnanediol glucuronide and basal body temperature in female orangutans,Pongo pygmaeus

Changes in basal body temperature (BBT) in relation to the menstrual cycle were investigated in three adult female orangutans (Pongo pygmaeus). In particular, the relationships of BBT to urinary estrone conjugates (EC) and to pregnanediol glucuronide (PDG) were examined using two of the females during two cycles each. Radiotelemetry transmitters were implanted peritoneally to record core body temperatures. Radio signals were received approximately every 2 min, 24 h per day. Because temperatures during the period 0300–0400 h were most stable (i.e., were less likely to be affected by confounding variables such as activity), a mean of these values was used to calculate daily BBT. BBT showed a highly significant positive correlation with PDG but not with EC. Menstrual phases were associated with declining or trough levels of BBT. Although changes in BBT were not sufficiently distinct to predict or to preclsely identify the time of ovulation, the strong association between BBT and PDG suggests that radiotelemetry of BBT may be useful in monitoring ovarian cycles, especially the luteal phase, in this species. © 1994 Wiley-Liss, Inc.     

The costs of keeping cool in a warming world: implications of high temperatures for foraging,thermoregulation and body condition of an arid‐zone bird

Recent mass mortalities of bats, birds and even humans highlight the substantial threats that rising global temperatures pose for endotherms. Although less dramatic, sublethal fitness costs of high temperatures may be considerable and result in changing population demographics. Endothermic animals exposed to high environmental temperatures can adjust their behaviour (e.g. reducing activity) or physiology (e.g. elevating rates of evaporative water loss) to maintain body temperatures within tolerable limits. The fitness consequences of these adjustments, in terms of the ability to balance water and energy budgets and therefore maintain body condition, are poorly known. We investigated the effects of daily maximum temperature on foraging and thermoregulatory behaviour as well as maintenance of body condition in a wild, habituated population of Southern Pied Babblers Turdoides bicolor. These birds inhabit a hot, arid area of southern Africa where they commonly experience environmental temperatures exceeding optimal body temperatures. Repeated measurements of individual behaviour and body mass were taken across days varying in maximum air temperature. Contrary to expectations, foraging effort was unaffected by daily maximum temperature. Foraging efficiency, however, was lower on hotter days and this was reflected in a drop in body mass on hotter days. When maximum air temperatures exceeded 35.5 °C, individuals no longer gained sufficient weight to counter typical overnight weight loss. This reduction in foraging efficiency is likely driven, in part, by a trade‐off with the need to engage in heat‐dissipation behaviours. When we controlled for temperature, individuals that actively dissipated heat while continuing to forage experienced a dramatic decrease in their foraging efficiency. This study demonstrates the value of investigations of temperature‐dependent behaviour in the context of impacts on body condition, and suggests that increasingly high temperatures will have negative implications for the fitness of these arid‐zone birds.     

Diel food utilization by woundfin,Plagopterus argentissimus,in Virgin River,Arizona

Synopsis Woundfin, Plagopterus argentissimus, fed predominantly on simuliid larvae during the day, and shifted to the larger Hydropsyche spp. at night. Ephemeropteran larvae were eaten nearly uniformly throughout the 24 hour period. Mean weight of food consumed varied from 20–40 mg per individual (0.7–2.5% body weight) throughout the 24 h period. Our estimated daily ration of about 8% body weight, at temperatures that varied between 15–25°C, is based upon our measure of mean gut contents over a 24h period, combined with intestinal evacuation rates suggested for other cyprinids in the literature. The relatively continuous feeding pattern suggests a foraging strategy that would minimize competition with other species for food during June, a period of minimum annual food abundance in Virgin River.     

Effects of temperature on food ingestion rate and absorption,retention, and equilibrium burden of phosphorus in an aquatic snail,Goniobasis clavaeformis Lea *

The effects of sublethal temperatures on feeding rates and phosphorus dynamics of a freshwater snail, Goniobasis clavaeformis Lea, were determined and feeding rates were measured at four temperatures. The food source was aufwuchs labelled with radioactive phosphorus. A model was developed to elucidate the results of this type of study. Food ingestion rate increased with increasing temperature up to 14°C and then decreased at temperatures above 14°C. The elimination rate of absorbed phosphorus increased with increasing temperature throughout the entire range of experimental temperatures, 10-19.3°C. Mean retention times of absorbed phosphorus i n Goniobasis were estimated to be 34, 24, 10, and 6 days at 10, 13.8, 15, and 193°C, respectively. Mean retention time of unabsorbed ³²P in the gut of this species as a function of temperature followed the same temperature relationship as that of ingestion rate. The absorption efficiency of phosphorus was estimated to be constant at about 39% for ail experimental temperatures, although the data suggest that the absorption ePRciency may have been related inversely to the rate of gut clearance or directly to the residence time of food in the gut. The equilibrium body load of phosphorus at each experimental temperature was estimated based on concentrations of stable phosphorus in the food source and the kinetics of ³²P in Goniobasis. The equilibrium body burden of phosphorus in Goniobasis increased with increasing temperatures up to a maximum at 11–12°C and then decreased at temperatures above 12°C.     

Daily torpor in the Djungarian hamster (Phodopus sungorus): interactions with food intake,activity, and social behaviour

Summary In Djungarian hamsters,Phodopus sungorus, daily torpor occurs spontaneously in winter in the presence of abundant food, but individuals show different tendencies to enter torpor. The results show that in hamsters fed rodent chow ad libitum individual torpor frequencies were negatively correlated with both food consumption and the amount of nocturnal locomotor activity. Provision of cafeteria diet at ambient temperatures below thermoneutrality significantly lowered torpor frequencies and induced body weight gains. However, in hamsters fed seeds with a high fat or carbohydrate content (i.e., sunflower seeds or wheat, respectively) neither a decrease of torpor frequencies nor an increase of body weights was observed. The results suggest that in Djungarian hamsters, daily torpor is an intrinsic component of energy balance control and is functionally linked to individual physiological adjustments of food consumption and foraging activity. In addition, the employment of daily torpor can be affected by social interactions, since the long-term pattern of alternations between torpor and normothermia was found to be synchronized in breeding pairs caged together.Abbreviations T _a ambient temperature - DIT diet-induced thermogenesis     

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.     

Diel rhythmicity of an echinostome cercaria (Cercaria beaveri Pandey & Agrawal, 1977)

We have observed the rhythmic pattern of echinostome cercariae, infecting Lymnea stagnalis Linnaeus, 1758 in a freshwater body located near Barabanki. There is high cercarial shedding (74%) during dark phase (18.30–06.30 h), which is statistically significant (F = 861.04, p < 0.001). Sesonal pattern of rhythmicity shows maximum yield in summer months (April, May and June) and low yeild in February and July. Periodicity of 2 h shows their high shedding in dark phase (12.30–14.30 h). We also observed the effect of temperature at four different temperatures (10°, 15°, 20° and 25°) and their shedding was found to be high at 20 °C and low at 10 °C. Probably, in an effort to approach their intermediate hosts, they acquire this pattern of rhythmicity.     

The Annual Activity Pattern of Djungarian Hamsters (Phodopus sungorus) Is Affected by Wheel‐Running Activity

Djungarian hamsters (Phodopus sungorus) exhibit pronounced winter acclimatization with changes in body mass, gonads, fur, and thermogenic capacity induced by decreasing daylength. To determine whether the annual activity pattern reflects the crucial role of the photoperiod for the hamsters' seasonality, animals with and without access to a running wheel (RW) were exposed to natural lighting conditions (～52°N) and ambient temperatures. Registration of locomotion in hamsters with a RW revealed a clear activity pattern closely related to dusk and dawn throughout the year. In contrast, animals without RW access showed a less stable phase relationship between the activity and the day‐night cycle in autumn and winter. During these seasons, the activity phase either exceeded the dark phase or even became indistinguishable from the rest phase. This correlated not only with increased locomotion during the light phase but also over the whole 24 h period, especially in autumn. In RW hamsters, a similar but attenuated trend was found that possibly reflects foraging due to increased food hoarding before winter. The more stable correlation between activity time and night length in RW hamsters might be explained by a suppressing effect of light on wheel‐running behavior (negative masking) and/or a stabilizing effect of running exercise on rhythmicity. In a further experiment, the phase‐reference points lights‐off and lights‐on within artificial light‐dark (LD) cycles were compared to sunset and sunrise in an intermediate ratio of light and dark and in long days. With respect to the defined phase‐reference points of the zeitgeber, the phase relation between activity and the LD cycle was similar in natural and corresponding artificial lighting conditions, and dependent on the LD ratio.     

Thermoregulatory behaviour in Tropidurus torquatus (Squamata, Tropiduridae) from Brazilian coastal populations: an estimate of passive and active thermoregulation in lizards

Geographical variation in the degree of thermoregulatory behaviour of the lizard Tropidurus torquatus was studied in 10 restinga populations along approximately 1500 km of Brazilian coast. An index of thermoregulation was estimated using the difference between body and environmental (air and substrate) temperatures and the percentage of negative values for these differences (proportion of body temperatures lower than environmental temperatures). In most populations, the lizards primarily used active thermoregulation, through behavioural means, and mainly in relation to substrate temperatures. Along the restingas, the degree of active thermoregulation increased as a function of the increase in the local environmental temperatures along the restingas. Behavioural thermoregulation of T. torquatus helps the lizards to maintain their body temperatures within an optimal range in which to perform their normal daily activities.     

Thermal ecology of allopatric lizards (Sphenomorphus) in southeast Australia

Summary The Sphenomorphus quoyi species complex (Lacertilia: Scincidae) of southeast Australia consists of three lizard species, distributed as continuous but largely allopatric populations, and a fourth species which has a disjunct distribution at high altitudes within the range of the other three. The four species have similar Voluntary temperatures (range of body temperatures within which normal activity occurs) despite the fact that they occupy different geographical areas.Altitudinal zonation is shown in the distribution pattern of the four species with S. quoyi and S. tympanum (warm temperate) restricted to the lower altitudes. The level of the mean daily minimum and maximum temperatures are different in each of the four species distribution areas. Similarly, the area occupied by each species is characterized by different daily sunlit and shade surface temperatures and different duration of ground surface subzero temperatures. Floristic composition of the four areas and the basking sites utilized by each species are also dissimilar.The lower temperature tolerances and the acclimation range of the Critical Minimum temperatures of S. quoyi and S. tympanum (warm temperate) exclude these species from the higher altitudes with the relatively lower environmental temperature levels. The Critical temperatures of the species which are found at high altitudes, do not explain why sympatry is not found with the lowland species.     

Rhythmicity in the emergence of Cercaria tondoni sp., a gymnocephalus cercaria from Lymnea stagnalis (Linnaeus, 1758)

Emerging pattern of Cercaria tondoni sp., a distome (possessing a ventral sucker lying some distance from the posterior end and approximately at anterior third of the body) belonging to gymnocephalus group (having an oval body and tail devoid of stylets or spines), shows a daily rhythm, being greater during the light phase (0630:1830?h) – similar to that found in a freshwater snail Lymnea stagnalis, Linnaeus, 1758. The peak time of emergence 1230–1430?h has been measured, and there is a high risk for invertebrate or vertebrate hosts and other diurnal animals to acquire infection during this period. However 20% of total shedding in a population of cercariae has also been recorded during the dark phase (0630–1830?h) but there was no significant rhythmicity within this period. An attempt has been made to record cercarial emergence throughout the year, which is of great importance for human welfare. It was observed that the months of April, May, and June are those where frequency of emergence was highest. Implications of this rhythmicity are considered.     

Daily Behavioral Rhythmicity and Organization of the Suprachiasmatic Nuclei in the Diurnal Rodent,Lemniscomys barbarus

Wheel‐running activity was recorded in Lemniscomys barbarus exposed to different lighting conditions. This rodent shows rhythmic locomotor activity under natural twilight‐light/dark (LD) as well as squared‐LD cycles. A mean of 77% of the activity occurred during the light phase. Under different controlled photoperiods, the quantity of daily locomotor activity was relatively stable except for a lower level in the shortest photoperiod tested (LD 06∶18). The duration of the active phase tended to increase with the duration of the light phase, especially in the longer photoperiods. Whatever the lighting conditions, Lemniscomys barbarus started running before lights‐on and stopped after lights‐off. The phase angle of activity offset relative to lights‐off was stable in each squared‐photoperiod, whereas the phase angle of activity onset relative to lights‐on was significantly the highest under the shortest photoperiods. Recording of activity under constant lighting conditions showed that the daily rhythm of locomotor activity is fundamentally circadian. The endogenous period was slightly<24 h (mean=23.8 h) in permanent darkness and>24 h (mean=24.5 h) in continuous light. Re‐entrainment of the locomotor activity rhythm after a 6 h phase advance or delay requires only four days on average. Moreover, the phase‐responses curve to a 30 min light pulse (200 lux) in Lemniscomys barbarus kept in constant dark reveals large phase shifts according to circadian times (CT). With CT0 being defined as the onset of daily activity, maximum phase delay and advance shifts were observed at CT11 (Δ Ψ=‐5.7 h±2.3 h) and CT21 (Δ Ψ =4.9±1.2 h), respectively. Interestingly, the phase‐response curve to light did not show any dead zone. Immunohistochemical staining of the suprachiasmatic nuclei indicates that arginine vasopressin‐immunoreactive cell bodies and fibers delimited a dorsal subregion that extends laterally and medially. The ventral subregion is rich in vasoactive intestinal peptide‐immunoreactive neurones overlapping a smaller area containing gastrin‐releasing peptide‐expressing cells and receives numerous fibers labeled with neuropeptide Y antibody. The results of this study clearly demonstrate that Lemniscomys barbarus is a diurnal species highly sensitive to the shifting effects of light. Overall, this rodent can be considered a new and interesting model for circadian rhythm neurobiology.     

Winter body temperature patterns in free-ranging Cape ground squirrel, Xerus inauris: no evidence for torpor

The body temperature (T _b) of Cape ground squirrels (Xerus inauris, Sciuridae) living in their natural environment during winter has not yet been investigated. In this study we measured abdominal T _b of eight free-ranging Cape ground squirrels over 27 consecutive days during the austral winter. Mean daily T _b was relatively stable at 37.0 ± 0.2°C (range 33.4 to 40.2°C) despite a marked variation in globe temperature (T _g) (range −7 to 37°C). Lactating females (n = 2) consistently had a significantly higher mean T _b (0.7°C) than non-lactating females (n = 3) and males. There was a pronounced nychthemeral rhythm with a mean active phase T _b of 38.1 ± 0.1°C and a mean inactive phase T _b of 36.3 ± 0.3°C for non-lactating individuals. Mean daily amplitude of T _b rhythm was 3.8 ± 0.2°C. T _b during the active phase closely followed T _g and mean active phase T _b was significantly correlated with mean active phase T _g (r ² = 0.3–0.9; P < 0.01). There was no evidence for daily torpor or pronounced hypothermia during the inactive phase, and mean minimum inactive phase T _b was 35.7 ± 0.3°C for non-lactating individuals. Several alternatives (including nocturnal huddling, an aseasonal breeding pattern and abundant winter food resources) as to why Cape ground squirrels do not employ nocturnal hypothermia are discussed.     

Green‐brown polymorphism in alpine grasshoppers affects body temperature

1. Ectothermic animals depend on external heat sources for pursuing their daily activities. However, reaching sufficiently high temperature can be limiting at high altitudes, where nights are cold and seasons short. We focus on the role of a green‐brown color polymorphism in grasshoppers from alpine habitats. The green‐brown polymorphism is phylogenetically and spatially widespread among Orthopterans and the eco‐evolutionary processes that contribute to its maintenance have not yet been identified.
2. We here test whether green and brown individuals heat up to different temperatures under field conditions. If they do, this would suggest that thermoregulatory capacity might contribute to the maintenance of the green‐brown polymorphism.
3. We recorded thorax temperatures of individuals sampled and measured under field conditions. Overall, thorax temperatures ranged 1.7–42.1°C. Heat up during morning hours was particularly rapid, and temperatures stabilized between 31 and 36°C during the warm parts of the day. Female body temperatures were significantly higher than body temperatures of males by an average of 2.4°C. We also found that brown morphs were warmer by 1.5°C on average, a pattern that was particularly supported in the polymorphic club‐legged grasshopper Gomphocerus sibiricus and the meadow grasshopper Pseudochorthippus parallelus.
4. The difference in body temperature between morphs might lead to fitness differences that can contribute to the maintenance of the color polymorphism in combination with other components, such as crypsis, that functionally trade‐off with the ability to heat up. The data may be of more general relevance to the maintenance of a high prevalence polymorphism in Orthopteran insects.

     

Daily rhythm of body and auricle temperature in goats kept at two different ambient temperatures

In fluctuating environmental temperature, homeotherms are able to maintain stable their body temperature, which however reveals a rhythmic daily pattern as described in literature. Because of the importance of body temperature rhythmicity in the knowledge of thermal homeostasis and as a means to facilitate the study of biological rhythmicity in general, the aim of our study was to assess the influence of two different ambient temperature on the daily rhythmicity of body and auricle temperature in goat (Capra hircus). For our study 6 female adult Maltese goats (18 month old), not pregnant and clinically healthy were used. On each subject body and auricle temperature was recorded during two different periods, of 7 days each, every 3 hours for 24 hours from 07.00 to 04.00, at different environmental temperature (1^st period 18.25 ± 1.48°C, 2^nd period 28.25 ± 2.05°C). The analysis of the obtained result under two ambient temperature indicates the existence of a daily periodicity, with small differences in amplitude and acrophase between the two studied period, both in body and auricle temperature in Maltese breed goat so we can assume that environmental temperature can influence in a significant way the daily pattern of body and auricle temperature.     

Physiological and behavioural responses to seasonal changes in environmental temperature in the Australian spiny crayfish Euastacus sulcatus

The strategies used by ectotherms to minimise the detrimental effects of suboptimal thermal environments on physiological performance are often related to whether they inhabit a terrestrial or aquatic environment. Most terrestrial ectotherms use thermoregulatory strategies to maintain body temperature within an optimal range, while many aquatic ectotherms utilise thermal acclimation to maintain performance over varying seasonal temperatures. This study aimed to elucidate the relative contributions of acclimation and behavioural thermoregulation to maintaining whole-animal performance over varying seasonal temperatures in the semi-terrestrial Lamington spiny crayfish (Euastacus sulcatus). Crayfish activity and surface temperatures were determined by means of radio tracking and behavioural observations. Field studies demonstrated that E. sulcatus is exposed to stable daily temperatures, varying only between seasons from 10°C in late winter to over 20°C in summer. Also, terrestrial behaviour corresponded to a small portion of crayfish time (1.13%), much lower than predicted, indicating that E. sulcatus has limited opportunity for behavioural thermoregulation. We also tested the effect of acclimation to either 10 or 20°C on chela strength and stamina. We found acclimation had a more marked effect on chela stamina than maximum strength measures; however, overall acclimatory capacity was limited in E. sulcatus. Thus, we found that the semi-terrestrial crayfish E. sulcatus used neither thermoregulatory behaviours nor physiological strategies to deal with seasonal changes in environmental temperature.     

Variation in the daily rhythm of body temperature of free-living Arabian oryx (Oryx leucoryx): does water limitation drive heterothermy?

Heterothermy, a variability in body temperature beyond the limits of homeothermy, has been advanced as a key adaptation of Arabian oryx (Oryx leucoryx) to their arid-zone life. We measured body temperature using implanted data loggers, for a 1-year period, in five oryx free-living in the deserts of Saudi Arabia. As predicted for adaptive heterothermy, during hot months compared to cooler months, not only were maximum daily body temperatures higher (41.1 ± 0.3 vs. 39.7 ± 0.1°C, P = 0.0002) but minimum daily body temperatures also were lower (36.1 ± 0.3 vs. 36.8 ± 0.2°C, P = 0.04), resulting in a larger daily amplitude of the body temperature rhythm (5.0 ± 0.5 vs. 2.9 ± 0.2°C, P = 0.0007), while mean daily body temperature rose by only 0.4°C. The maximum daily amplitude of the body temperature rhythm reached 7.7°C for two of our oryx during the hot-dry period, the largest amplitude ever recorded for a large mammal. Body temperature variability was influenced not only by ambient temperature but also water availability, with oryx displaying larger daily amplitudes of the body temperature rhythm during warm-dry months compared to warm-wet months (3.6 ± 0.6 vs. 2.3 ± 0.3°C, P = 0.005), even though ambient temperatures were the same. Free-living Arabian oryx therefore employ heterothermy greater than that recorded in any other large mammal, but water limitation, rather than high ambient temperature, seems to be the primary driver of this heterothermy.     

Did chironomid emergence release Daphnia from fish predation and lead to a Daphnia-driven clear-water phase in Lake Towada,Japan?

The emergence of the chironomid pupae into the water column may potentially allow Daphnia to be released from positively size-selective fish predation and indirectly cause a Daphnia-driven clear-water phase in lakes. We studied these processes in Lake Towada, Japan, from April to October 1998. The biomass of the Daphnia longispina population was stable from April through June and increased by 3-fold in mid-July. This coincided well with the onset of the clear-water phase in the lake. The sharp decline of chironomid larvae in the sediment in June suggested that the major emergence occurred. Stomach contents of kokanee (Oncorhynchus nerka) and pond smelt (Hypomesus transpacificus nipponensis) also shifted from D. longispina to the chironomid pupae at that time. However, mean individual body size, mean ovigerous female size and clutch size of D. longispina declined rapidly in mid-June and stayed smaller thereafter compared to those in April–May, suggesting that fish predation was stronger after mid-June. It is probable that lower water temperatures in April–May suppressed fish feeding activity as well as reproduction in D. longispina, which resulted in the stable biomass of D. longispina. The increased water temperatures resulted in the stable biomass of D. longispina. This would lead to a mid-July peak of less predation-sensitive young adults. Therefore, the chironomid emergence seemed neither to release D. longispinafrom fish predation nor to be associated with the clear-water phase in the present study.     

Studies on the Polymorphism of l-Glutamic Acid

The enthalpy differences between the α- and β-crystals of l-glutamic acid were measured and ΔH_α?β of ?75, ?95, 8 and 27±20cal./mol. were obtained at temperatures of 5, 15, 30 and 40°C, respectively. From this result, it was found that the α-form is the more stable form in solid phase at temperatures lower than 30°C and vice versa when higher than 30°C, though the α-form had been found to be the less stable form as the saturating body in the aqueous solution in all range of temperature.