Increased food intake after starvation enhances sleep in Drosophila melanogaster

Feeding and sleep are highly conserved,interconnected behaviors essential for survival.Starvation has been shown to potently suppress sleep across species;however,whether satiety promotes sleep is still unclear.Here we use the fruit fly,Drosophila melanogaster,as a model organism to address the interaction between feeding and sleep.We first monitored the sleep of flies that had been starved for 24 h and found that sleep amount increased in the first 4 h after flies were given food.Increased sleep after starvation was due to an increase in sleep bout number and average sleep bout length.Mutants of translin or adipokinetic hormone,which fail to suppress sleep during starvation,still exhibited a sleep increase after starvation,suggesting that sleep increase after starvation is not a consequence of sleep loss during starvation.We also found that feeding activity and food consumption were higher in the first 10-30 min after starvation.Restricting food consumption in starved flies to 30 min was sufficient to increase sleep for 1 h.Although flies ingested a comparable amount of food at differing sucrose concentrations,sleep increase after starvation on a lower sucrose concentration was undetectable.Taken together,our results suggest that increased food intake after starvation enhances sleep and reveals a novel relationship between feeding and sleep.     

The Drosophila takeout gene is a novel molecular link between circadian rhythms and feeding behavior

We report the characterization of a novel Drosophila circadian clock-regulated output gene, takeout (to). The to amino acid sequence shows similarity to two ligand binding proteins, including juvenile hormone binding protein. to mRNA is expressed in the head and the cardia, crop, and antennae-structures related to feeding. to expression is induced by starvation, which is blocked in all arrhythmic central clock mutants, suggesting a direct molecular link between the circadian clock and the feeding/starvation response. A to mutant has aberrant locomotor activity and dies rapidly in response to starvation, indicating a link between locomotor activity, survival, and food status. We propose that to participates in a novel circadian output pathway that conveys temporal and food status information to feeding-relevant metabolisms and activities.     

The effect of fasting and refeeding on temperature preference,activity and growth of roach, <Emphasis Type="Italic">Rutilus rutilus</Emphasis>

Most fish species are regularly subjected to periods of starvation during which a reduction of energy turnover might be favourable for the animal. This reduction of energy flux may be achieved by changes in thermal behaviour and/or swimming activity. We investigated such behavioural changes during starvation and subsequent refeeding in roach, Rutilus rutilus, with respect to energetic benefits and growth maximisation. Roach, acclimated to a wide range of temperatures (4, 12, 20, 24, 27 and 30 °C), were fed to excess, subjected to 3 weeks of starvation and subsequently refed in order to determine the temperature dependence of feeding rates, growth rates and conversion efficiency (K₁) under control conditions and during compensatory growth. When exposed to a thermal gradient, control animals preferentially selected a temperature of 26.8ǂ.9 °C, which is in the range of the optimal temperatures for feeding, growth and conversion efficiency. Starving fish showed a distinct circadian pattern of the mean selected temperature (MST). They migrated to cooler water in the dark (MST_dark=22.8ǃ.1 °C) but returned to warmer water during daytime. This behaviour may be regarded as a trade-off between the potentially higher food density in warmer water areas and the energetic benefit of selecting cooler water patches. The circadian pattern of MST was gradually abandoned upon refeeding and control values were reached again after 3 weeks. Energetically more effective than behavioural hypothermia was the reduction of swimming activity. During starvation, activity peaks were slightly lower than under control conditions and mean daily activity decreased by about 50%. Swimming velocity, however, was not affected by feeding regime. After a period of starvation fish showed compensatory growth at all temperatures, even below 12 °C, where these animals normally do not grow. This suggests that after a period of starvation the critical temperature for growth shifts to lower values.     

Circadian rhythms in honeybees: entrainment by feeding cycles

ABSTRACT. Colonies of the South African honeybee race Apis mellifera capensis (Escholtz) were maintained under constant conditions of illumination (200 lux), temperature (25±lC) and relative humidity (65±3%). Activity was measured at the hive entrance. After ad libitum feeding for at least 5 days, food was presented for only 2 h/day either for 1 week (series 1) or for 2 weeks (series 2). In the last part of each experiment, food was again available all the time. Colonies which showed free-running circadian activity rhythms (with periods ranging from 22.6 to 24.8 h) during ad libitum feeding were submitted to feeding cycles with inter-feeding intervals (T) of 22, 23, 24 and 25 h. In most of these experiments the rhythms were synchronized by the feeding schedule, resulting in a stable phase-angle difference between onset of activity and onset of food availability. The duration of this anticipatory activity was positively correlated with T. When ad libitum feeding was resumed, the period of the rhythm induced by the feeding schedule persisted for a few days. Thereafter, the rhythm was free-running again with a period close to that observed in the first part of the experiment. The conclusion is drawn that, under the influence of periodic feeding, the activity of honeybee colonies has the characteristics of an entrained circadian system.     

Oxygen uptake of growth hormone transgenic coho salmon during starvation and feeding

Oxygen uptake of growth hormone transgenic coho salmon Oncorhynchus kisutch was measured in individual fish with a closed-system respirometer and was compared with that of similar-sized non-transgenic control coho salmon during starvation and when fed a fixed ration or to satiation. Transgenic and control fish did not differ in their standard oxygen uptake after 4 days of starvation, although control fish had a higher routine oxygen uptake, scope for spontaneous activity and initial acclimation oxygen uptake. During feeding, transgenic fish ate significantly more than control fish, and had an overall oxygen uptake that was 1·7 times greater than control fish. When fish that had eaten the same per cent body mass were compared, transgenic fish had an oxygen uptake that was 1·4 times greater than control fish. Differences in oxygen uptake in growth hormone transgenic coho salmon and non-transgenic fish appear to be due to the effects of feeding, acclimation and activity level, and not to a difference in basal metabolism.     

Seasonal variations in the activity budget of Japanese macaques in the coniferous forest of Yakushima: effects of food and temperature

Seasonal variations in the activity budget of Japanese macaques in the coniferous forest of Yakushima were studied over the course of 1 year. On an annual basis, they spent 38% of the daytime feeding, 16% traveling, 14% in social interactions, and 32% engaged in resting. The effects of temperature and food-related factors (i.e., food distribution, feeding speed, and food abundance) on the seasonal variations of activity budget were examined by stepwise multiple regression analysis. When the temperature was low, the macaques decreased traveling and feeding time, in accordance with the prediction that endothermal animals save energy under severe thermoregulatory cost. When the feeding speed of available foods was slow, they spent more time feeding. When high-quality foods were abundant, they decreased feeding time. These macaques did not respond to fluctuations in food distribution. The present results indicate the importance of temperature, in addition to food-related factors, as a determinant of activity budgets.     

Development of gluconeogenesis from dihydroxyacetone in rat hepatocytes during a feeding cycle and starvation.

Pyruvate kinase activity and the rates of gluconeogenesis and glycolysis in rat hepatocytes were evaluated by production of glucose and lactate + pyruvate from dihydroxyacetone during a feeding cycle or progressive starvation. In fed rats, during daylight (low food intake) and until darkness, gluconeogenesis progressively increased and glycolysis decreased slightly, but gluconeogenesis never exceeded glycolysis. During nocturnal feeding, gluconeogenesis and glycolysis returned to their morning rates. After 8 h starvation, an equal proportion of dihydroxyacetone was converted into glucose and into lactate + pyruvate. When glycogen was depleted (11 h of starvation), gluconeogenesis was maximal and glycolysis minimal. In fed and starved rats, the concentration of fructose 1,6-bisphosphate was the same. The activity ratio of pyruvate kinase (ratio of velocity at 0.5 mM-phosphoenolpyruvate to the maximum catalytic activity obtained with 4mM-phosphoenolpyruvate) was high in crude extracts of cells incubated with dihydroxyacetone and low in (NH4)2SO4-treated extracts, but remained unchanged during the whole experiment. There was no correlation between the rates of gluconeogenesis and glycolysis from dihydroxyacetone and the activity ratio of pyruvate kinase.     

Circadian Assessment of Lipids in the Hyperphagic Obese Rat Compared with Lean Litter-Mates

Time and feeding influences on cholesterol, triglyceride, glucose and insulin levels, and serum cholinesterase activity were assessed in a genetically-hyperlipidemic hyperphagic obese rat model, and compared with its lean litter-mate. Following a 28-day acclimation to a 12-hr light/dark cycle, blood samples were obtained every 2 hr from rats via tail bleed for a 24-hr period. Synchronization with other animal studies was established by endogenous serum Cortisol levels [acrophase 18-20 hr after light onset (HALO) in both groups]. Triglycerides cholesterol, insulin and glucose levels were significantly elevated in obese versus lean rats. Obese rats were observed to feed throughout the 24-hr cycle, whereas lean litter-mates ate only during the dark cycle. No circadian rhythmicity was found in glucose levels with either rat group. Insulin levels were not correlated. Although triglyceride levels peaks at 13 HALO in lean rats, no pattern was observed in obese rats. Cholesterol levels were unchanged with time in either group. Cholinesterase activity followed a circadian rhythm in the lean, but not obese, rats with an acrophase estimated at 8 HALO. In contrast to previous reports, enzyme activity was not correlated with triglyceride levels in either rat group. Circadian similarities in insulin levels between rat groups suggest changes in insulin metabolism and/or secretion which are likely to be independent of feeding or activity. Conversely, triglyceride levels remained elevated throughout the 24-hr period in obese rats, whereas significant increases were observed in lean rats during the dark active cycle. These data suggest that triglyceride levels, and not insulin and cholesterol levels, are most likely dependent on feeding patterns.     

Circadian Assessment of Lipids in the Hyperphagic Obese Rat Compared with Lean Litter-Mates

Time and feeding influences on cholesterol, triglyceride, glucose and insulin levels, and serum cholinesterase activity were assessed in a genetically-hyperlipidemic hyperphagic obese rat model, and compared with its lean litter-mate. Following a 28-day acclimation to a 12-hr light/dark cycle, blood samples were obtained every 2 hr from rats via tail bleed for a 24-hr period. Synchronization with other animal studies was established by endogenous serum Cortisol levels [acrophase 18–20 hr after light onset (HALO) in both groups]. Triglycerides cholesterol, insulin and glucose levels were significantly elevated in obese versus lean rats. Obese rats were observed to feed throughout the 24-hr cycle, whereas lean litter-mates ate only during the dark cycle. No circadian rhythmicity was found in glucose levels with either rat group. Insulin levels were not correlated. Although triglyceride levels peaks at 13 HALO in lean rats, no pattern was observed in obese rats. Cholesterol levels were unchanged with time in either group. Cholinesterase activity followed a circadian rhythm in the lean, but not obese, rats with an acrophase estimated at 8 HALO. In contrast to previous reports, enzyme activity was not correlated with triglyceride levels in either rat group. Circadian similarities in insulin levels between rat groups suggest changes in insulin metabolism and/or secretion which are likely to be independent of feeding or activity. Conversely, triglyceride levels remained elevated throughout the 24-hr period in obese rats, whereas significant increases were observed in lean rats during the dark active cycle. These data suggest that triglyceride levels, and not insulin and cholesterol levels, are most likely dependent on feeding patterns.     

捕食风险对不同饥饿状态下艾虎取食行为的影响

在室内条件下,将大鵟作为艾虎的天敌动物,通过双通道选择实验确定6 只成体艾虎在3 个捕食风险水平和4 种饥饿状态条件下的取食行为,探讨艾虎在取食过程中对饥饿风险与捕食风险的权衡策略。研究结果表明:在无捕食风险存在时,艾虎被剥夺食物0 d 和1 d 后对食物量不同的两个斑块中的取食量和利用频次均无明显不同(P > 0. 05),但对高食物量斑块的利用时间均明显高于低食物量斑块的(P <0.05),而艾虎被剥夺食物2 d和3 d后对高食物量斑块中的取食量和利用时间均明显高于低食物量斑块中的(P < 0.05),但在利用频次上均无明显差异(P > 0.05)。在面临低风险时,艾虎在4 种饥饿状态下均只利用无天敌动物存在的低食物量斑块,而基本不利用有天敌动物存在的高食物量斑块。在面临高风险时,艾虎不得不利用有天敌动物存在的食物斑块,被剥夺食物0 d 时艾虎对无风险、无食物量斑块的利用时间基本相同于对高风险、有食物量斑块的利用时间(P>0.05),而被剥夺食物1d、2 d 和3 d 后艾虎对高风险、有食物量斑块的利用时间明显高于无风险、无食物量斑块的(P< 0. 05)。在相同风险条件下,随着饥饿程度增加,艾虎在斑块中的取食量均明显增加(P< 0.05),而对斑块的利用时间和利用频次明显降低(P<0.05)。在相同的饥饿状态下,不同风险水平时,艾虎在斑块中的取食量无明显的差异(P>0.05),但在低风险和高风险时对斑块的利用时间和频次均明显低于无风险时的(P <0.05)。以上结果说明艾虎能够根据食物摄取率和自身的能量需求在捕食风险和饥饿风险之间做出权衡,当饥饿风险小于捕食风险时,艾虎趋于躲避捕食风险,当饥饿风险大于捕食风险时,艾虎趋于面对捕食风险,所采用的取食策略是减少活动时间和能量消耗,最大程度地提高单位时间内获得的能量。     

Food-Entrained Feeding and Locomotor Circadian Rhythms in Rats Under Different Lighting Conditions

It has been suggested that two endogenous timekeeping systems, a light-entrainable pacemaker (LEP) and a food-entrainable pacemaker (FEP), control circadian rhythms. To understand the function and interaction between these two mechanisms better, we studied two behavioral circadian rhythmicities, feeding and locomotor activity, in rats exposed to two conflicting zeitgebers, food restriction and light-dark cycles. For this, the food approaches and wheel-running activity of rats kept under light-dark (LD) 12:12, constant darkness (DD), or constant light (LL) conditions and subjected to different scheduled feeding patterns were continuously recorded. To facilitate comparison of the results obtained under the different lighting conditions, the period of the feeding cycles was set in all three cases about Ih less than the light-entrained or free-running circadian rhythms. The results showed that, depending on the lighting conditions, some components of the feeding and wheel-running circadian rhythms could be entrained by food pulses, while others retained their free-running or light-entrained state. Under LD, food pulses had little influence on the light-entrained feeding and loco-motor rhythms. Under DD, relative coordination between free-running and food-associated rhythms may appear. In both cases, the feeding activity associated with the food pulses could be divided into a prominent phase-dependent peak of activity within the period of food availability and another afterward. Wheel-running activity mainly followed the food pulses. Under LL conditions, the food-entrained activity consisted mainly of feeding and wheel-running anticipatory activity. The results provide new evidence that lighting conditions influence the establishment and persistence of food-entrained circadian rhythms in rats. The existence of two coupled pacemakers, LEP and FEP, or a multioscillatory LEP may both explain our experimental results.     

Food-Entrained Feeding and Locomotor Circadian Rhythms in Rats Under Different Lighting Conditions

It has been suggested that two endogenous timekeeping systems, a light-entrainable pacemaker (LEP) and a food-entrainable pacemaker (FEP), control circadian rhythms. To understand the function and interaction between these two mechanisms better, we studied two behavioral circadian rhythmicities, feeding and locomotor activity, in rats exposed to two conflicting zeitgebers, food restriction and light-dark cycles. For this, the food approaches and wheel-running activity of rats kept under light-dark (LD) 12:12, constant darkness (DD), or constant light (LL) conditions and subjected to different scheduled feeding patterns were continuously recorded. To facilitate comparison of the results obtained under the different lighting conditions, the period of the feeding cycles was set in all three cases about Ih less than the light-entrained or free-running circadian rhythms. The results showed that, depending on the lighting conditions, some components of the feeding and wheel-running circadian rhythms could be entrained by food pulses, while others retained their free-running or light-entrained state. Under LD, food pulses had little influence on the light-entrained feeding and loco-motor rhythms. Under DD, relative coordination between free-running and food-associated rhythms may appear. In both cases, the feeding activity associated with the food pulses could be divided into a prominent phase-dependent peak of activity within the period of food availability and another afterward. Wheel-running activity mainly followed the food pulses. Under LL conditions, the food-entrained activity consisted mainly of feeding and wheel-running anticipatory activity. The results provide new evidence that lighting conditions influence the establishment and persistence of food-entrained circadian rhythms in rats. The existence of two coupled pacemakers, LEP and FEP, or a multioscillatory LEP may both explain our experimental results.     

Relative value of light and food as synchronizers of liver phosphorylase circadian rhythm.

The role played by light and feeding schedules on the circadian rhythm of glycogen content and phosphorylase activity of the liver has been studied. In one experiment, mice were subjected to a regimem of constant darkness during 21 days and compared with mice kept in 12 hrs of light alternating with 12 hrs of darkness. Both groups received food and water ad libitum. Liver glycogen content as well as phosphorylase activity showed, with slight differences, similar circadian variations. In a second experiment, mice under similar lighting conditions (LD 12:12), with water access ad libitum, were divided into two groups; one was offered food ad libitum while the other group recieved food from 0700 to 1800 only. This experiment allowed up to compare two different schedules of food intake; ad libitum, normal schedule (from 1800 to 0600) and reversed schedule (from 0700 to 1800). A complete reversal of the circadian rhythm was observed after 21 days in the group with the reverted feeding schedule. We conclude that food can function as the primary synchronizer in spite of the lighting regimen.     

Feeding history effects on feeding responses of Rhagoletis indifferens (Dipt., Tephritidae) to GF-120 and Nulure

Abstract:  Effects of feeding history on feeding responses of western cherry fruit fly, Rhagoletis indifferens Curran, to the commercial protein baits GF-120 and Nulure were determined in the laboratory. Flies were kept on 5% sucrose alone or yeast extract and sucrose (Y + S) for 3–7 or 14–16 days and exposed to 24-h-old GF-120 or Nulure drops on artificial leaves. Numbers and durations of feeding events on leaves and durations of non-feeding events were recorded over 1-h periods. Experiments were also conducted to determine effects of Y + S feeding sequences on responses to Nulure, of starvation after sucrose or Y + S feeding on responses to Nulure, and of feeding history on mortality after exposure to GF-120 and Nulure. Protein-deprived flies consistently fed more times on GF-120 and Nulure than protein-fed flies and fed longer. One day of exposure to Y + S or 16 h of starvation after exposure to sucrose caused greater feeding on Nulure than 7 days of exposure to Y + S or 16 h of starvation after exposure to Y + S. Durations of non-feeding events on leaves with sucrose or bait were similar in protein-deprived and -fed flies. Responses of 4- to 6-day-old flies kept on sucrose to 0- and 24-h-old GF-120 or Nulure were similar. More flies kept on sucrose were paralysed or dead at 6–32 h after exposure to GF-120 or Nulure with spinosad than flies kept on Y + S. Results show that complete or long periods of protein deprivation and starvation after sucrose feeding increased feeding responses to GF-120 and Nulure. The general lack of differences in durations of non-feeding events on leaves with sucrose or GF-120 or Nulure in protein-deprived and -fed flies suggests that most protein-deprived flies found baits through chance encounters following normal movement.     

Evidence for time-of-day dependent effect of neurotoxic dorsomedial hypothalamic lesions on food anticipatory circadian rhythms in rats

The dorsomedial hypothalamus (DMH) is a site of circadian clock gene and immediate early gene expression inducible by daytime restricted feeding schedules that entrain food anticipatory circadian rhythms in rats and mice. The role of the DMH in the expression of anticipatory rhythms has been evaluated using different lesion methods. Partial lesions created with the neurotoxin ibotenic acid (IBO) have been reported to attenuate food anticipatory rhythms, while complete lesions made with radiofrequency current leave anticipatory rhythms largely intact. We tested a hypothesis that the DMH and fibers of passage spared by IBO lesions play a time-of-day dependent role in the expression of food anticipatory rhythms. Rats received intra-DMH microinjections of IBO and activity and body temperature (T(b)) rhythms were recorded by telemetry during ad-lib food access, total food deprivation and scheduled feeding, with food provided for 4-h/day for 20 days in the middle of the light period and then for 20 days late in the dark period. During ad-lib food access, rats with DMH lesions exhibited a lower amplitude and mean level of light-dark entrained activity and T(b) rhythms. During the daytime feeding schedule, all rats exhibited food anticipatory activity and T(b) rhythms that persisted during 2 days without food in constant dark. In some rats with partial or total DMH ablation, the magnitude of the anticipatory rhythm was weak relative to most intact rats. When mealtime was shifted to the late night, the magnitude of the food anticipatory activity rhythms in these cases was restored to levels characteristic of intact rats. These results confirm that rats can anticipate scheduled daytime or nighttime meals without the DMH. Improved anticipation at night suggests a modulatory role for the DMH in the expression of food anticipatory activity rhythms during the daily light period, when nocturnal rodents normally sleep.     

Effects of diet and starvation on digestive enzyme activity and feeding behavior of the marine copepod Calanus pacificus

In this paper we look at the response of Calanus pacificus overa period of several weeks to both starvation and diet as reflectedby survival rates, feeding rates and digestive enzyme activities.Phytoplankton species used as food were the diatom Thalassiosiraweissflogii, two dinoflagellates, Gymnodinium simplex and Scrippsiellatrochoidea, and the chlorophyte Dunaliella tertiolecta. In general,C.pacificus appeared to be resistant to starvation for periodsup to 1 week. Survival remained high for at least 6 days ofstarvation, while maximum feeding rates remained constant forseveral days and then declined by 50% after a week of starvation.When initial digestive enzyme activities were low, they didnot change appreciably during the experiments. However, activitylevels dropped rapidly during starvation experiments in whichthey were initially high. Other evidence indicates that starvationmay induce changes in the digestive system before it affectsingestion rates or survival. In general, long-term changes indigestive enzyme activity under different dietary regimes weregradual. An exception to this pattern was S. trochoidea, whosepresence in the diet induced a precipitous, though reversible,decline in digestive enzyme activity, a phenomena possibly relatedto the toxic reaction to this species reported by other researchers.A positive induction of digestive enzymes occurred over a time-scaleof 1–5 days in response to a change in diet. The absenceof laminarin in the diet of C.pacificus for nearly 3 weeks (whenfeeding on G.simplex), during which time laminarinase activitydeclined by {small tilde}50%, did not adversely affect subsequentassimilation of a laminarin-rich food (T. weissflogii).     

Foraging in the ant Camponotus mus: nectar-intake rate and crop filling depend on colony starvation

The effects of colony starvation on the dynamics of nectar collection were studied in individual workers of the ant Camponotus mus. A laboratory colony was first deprived of carbohydrates for 15days, and thereafter fed daily ad libitum with diluted honey until satiation. During these two successive experimental phases, the probability of feeding, crop filling and fluid-intake rates were recorded daily for individual foragers collecting a 10% (w/w) sucrose solution. The feeding responses of individuals varied with the nutritional state of the colony. When the colony was deprived of sugar, acceptance of the sucrose solution was higher than under satiation. Feeding time increased with increasing starvation. During deprivation workers fed nearly continuously on the solution, whereas a number of feeding interruptions occurred under satiation. Crop filling also increased with increasing starvation, and showed a marked decrease when the colony was satiated. Fluid-intake rate during the deprivation phase was roughly twice that during the satiation phase. This matched well with the difference in sucking frequency recorded during ingestion in satiated and starved workers, which was also higher during starvation. Results indicate that the responsiveness of foragers, determined by the nutritional state of the colony, influenced both foraging decisions and the dynamics of fluid intake.     

A comparative analysis of feeding and hoarding in hamsters and gerbils

Male and female hamsters and gerbils were randomly assigned to one of three groups. The animals were tested under ad lib feeding conditions or food deprived until they had lost either 10% or 20% of their predeprivation body weight. They were given a 30-min. hoarding test for three consecutive days. The results indicated that although food-deprived gerbils ate more than control gerbils, deprivation had no significant effect on the food intake of hamsters. A sex difference was also evident in the food intake of gerbils; males ate more than did females. Although there was a sex and species difference in the amount of hoarding, deprivation had no significant effect on the amount of hoarding. The implications of these results for of different models of hoarding are discussed. These models contrast hoarding as a defensive response in the regulation of body weight or as an anticipatory activity that is influenced by other selection pressures.     

Food availability affects circadian clock-controlled activity and Zugunruhe in the night migratory male blackheaded bunting (Emberiza melanocephala)

This study investigated the functional linkage between food availability and activity behavior in the Palaearctic Indian night migratory blackheaded bunting (Emberiza melanocephala) subjected to artificial light-dark (LD) cycles. Two experiments were performed on photosensitive birds. In the first one, birds were exposed to short days (LD 10/14; Experiment 1A), long days (LD 13/11; Experiment 1B), or increasing daylengths (8 to 13?h light/d; Experiment 1C) and presented with food either for the whole or a restricted duration of the light period. In Experiments 1A and 1B, illumination of the light and dark periods or of the dark period, alone, was changed to assess the influence of the light environment on direct and circadian responses to food cycles. In the second experiment, birds were exposed to LD 12/12 or LD 8/16 with food availability overlapping with the light (light and food presence in phase) or dark period (light and food presence in antiphase). Also, birds were subjected to constant dim light (LL(dim)) to examine the phase of the activity rhythms under synchronizing influence of the food cycles. Similarly, the presentation of food ad libitum (free food; FF) during an experiment examined the effects of the food-restriction regimes on activity rhythms. A continuous measurement of the activity-rest pattern was done to examine both the circadian and direct effects of the food and LD cycles. Measurement of activity at night enabled assessment of the migratory phenotype, premigratory restlessness, or Zugunruhe. The results show that (i) light masked the food effects if they were present together; (ii) birds had a higher anticipatory activity and food intake during restricted feeding conditions; and (iii) food at night alone reduced both the duration and amount of Zugunruhe as compared to food during the day alone. This suggests that food affects both the daily activity and seasonal Zugunruhe, and food cycles act as a synchronizer of circadian rhythms in the absence of dominant natural environmental synchronizers, such as the light-dark cycle.     

Age differences in food intake and dietary selection of wild male Japanese macaques

Age differences in food intake and dietary selection were studied for 8 months among wild male Japanese macaques (Macaca fuscata) under non-predatory situations. Juveniles' feeding time was longer than adult males' in some months, in particular in mating seasons, but did not differ in the other months. Juveniles' feeding speed was slower than that of adult males. However, the age difference in average feeding speed was smaller (90%) than that in expected daily energy expenditure (62–58%). The extent of age difference in feeding speed varied with the food type: the difference was large for fibrous foods, but small for fruits or seeds. As a consequence of the age differences in time spent feeding and feeding speed, the age difference in daily food intake was smaller than expected from metabolic demands. Thus, the hypothesis that juveniles are more vulnerable to starvation than adults was not supported among male Japanese macaques in predator-free Yakushima. Juveniles ate more animal matter, while adult males ate more fibrous foods.