Circadian Feeding and Locomotor Pigeons and House Sparrows
Rhythms
in
1 and Michael Menaker Christopher C. Chabot Department of Biology, University of Virginia, Charlottesville, Virginia 22903 Abstract Feeding and locomotor activities were measured simultaneously in homing pigeons (Columba livia) and house sparrows (Passer domesticus). Feeding, as well as locomotor activity, was found to be regulated by a circadian clock in both of these species. Implantation of melatonin-filled capsules or exposure to constant light abolished feeding and locomotor rhythms in both species. Removal of the pineal gland from pigeons did not abolish either rhythm, whereas pinealectomy abolished both feeding and locomotor rhythms in house sparrows. Although feeding rhythms were generally more robust than locomotor rhythms in both of these species, different feeding and locomotor free-running periods were not observed within any individual pigeon or house sparrow. These results are consistent with the hypothesis that each of these species has a single pacemaker that regulates the timing of feeding and locomotor activity, but they do not rule out the possibility that separate clocks regulate these behaviors.
Key words rhythms, behavior, feeding, locomotion, light, pineal, birds, melatonin, oscillator, circadian
One of the central issues in the field of circadian biology concerns the regulation of multiple circadian outputs, such as feeding and locomotor activity. Although multiple outputs may conceivably be regulated by a single oscillatory system, there is some evidence that separate oscillators control different outputs in humans (Aschoff and Wever, 1976), rodents (Pittendrigh and Daan, 1976; Stephan et al., 1979), and birds (Ganshirt et al., 1984). In birds it is unclear whether the circadian system that regulates locomotor rhythms also regulates other behavioral rhythms. While much is known about the regulation of locomotor rhythms, other rhythmic outputs, such as feeding, have not been well characterized. In birds, circadian rhythms of feeding activity have only been measured in house sparrows, starlings, and pigeons. Studies in which either surgical or environmental manipulations were performed suggest that the three species differ in their responses to similar treatments. For example, following pinealectomy (PX) the feeding rhythm is abolished in house sparrows (Gwinner, 1989), but not in starlings (Gwinner et al., 1987). In pigeons it has been claimed that feeding rhythms do not persist in bright constant light (LL) (Yamada et al., 1988). In starlings the regulation of feeding rhythms may be fundamentally different from the regulation of locomotor rhythms (Ganshirt et al., 1984).
1. Present
address,
College, Plymouth,
which all correspondence should be New Hampshire 03264.
to
sent:
Department
of Natural
Sciences, Plymouth State
287
We have begun to address the question of circadian regulation of feeding in homing pigeons and house sparrows by monitoring both feeding and locomotor activity simultaneously and exposing these birds to conditions known to affect locomotor rhythms. The purpose of the present series of experiments was to make a systematic attempt to determine whether feeding activity in pigeons and house sparrows is under circadian control, and if so, to determine whether procedures known to affect locomotor rhythms in these species affect
feeding rhythms
in
a
similar
manner.
MATERIALS AND METHODS
EXPERIMENTAL BIRDS AND HOUSING CONDITIONS The homing pigeons (Columba livia; males and females, 400-600 g) used in this experiment were obtained from suppliers in Waco, TX (Louis Nicosia) and Eugene, OR (University of Oregon), and maintained either outdoors under natural lighting conditions or indoors under an artificial light-dark (LD) cycle of 12 hr light and 12 hr darkness (LD 12:12) prior to experimentation. House sparrows (Passer domesticus; males and females, 20-30 g) were wild-caught in Eugene, OR and maintained indoors under LD 12:12 conditions prior to experimentation. During the study, pigeons were individually housed in tilt-bottom cages (35 cm x 38 cm x 26 cm) suspended over a pan filled with bedding (Bed-O-Cob, The Andersons, Maumee, OH) within light-tight wooden boxes. House sparrows were also individually housed during the study in cages lacking a tilt bottom, as previously described
(Menaker, 1965). The light-tight boxes containing pigeons and sparrows were kept in a dark, temperaturecontrolled (23°C) room in which white noise (93 dBA) was continuously present (Menaker and Eskin, 1966). Lighting was provided in the experimental cages with a 4-W &dquo;cool white&dquo; fluorescent bulb (Ken Rad F4T5/cw). Light levels were measured with a Luna Pro light meter (Gossen, Germany). Food and water were available ad libitum at opposite ends of the cages and were replaced at approximately weekly intervals. Bedding was replaced at approximately biweekly intervals. An infrared viewer (FJW Optical Systems, Elgin, IL) was used to attend to birds held in constant darkness (DD). Birds were always allowed at least 10 days in an LD 12:12 cycle when first placed in the cage (light intensity during L was approximately 150 lux). Locomotor activity was monitored with two microswitches connected to the tilt bottom for pigeons and with one microswitch connected to one of two perches for sparrows (approximately 50% of the sparrows were housed in cages with a microswitch attached to the perch next to the food; the microswitch was attached to the other perch in the other 50%). Feeding activity was monitored for both species with an infrared emitter-detector pair mounted across a food access hole. Thus, birds were always exposed to constant levels of infrared light from the infrared emitter. All sparrow behavioral data were collected on an event recorder (Esterline-Angus, Indianapolis, IN); pigeon data were collected either on an event recorder or on a computer data acquisition system (Data Quest, Data-Sciences, Inc., Roseville, MN; EZ Paste software, M. Vogelbaum, Charlottesville,
VA).
288
EXPERIMENT l: CIRCADIAN CONTROL OF FEEDING AND THE ROLE OF THE PINEAL GLAND
Pigeons and sparrows were divided into two groups: pineal-intact (pigeons, n 11; sparrows, n 8; sparrows, n 4). Two of the six pineal-intact 6) and PX birds (pigeons, n described received sham PX as (Gaston and Menaker, 1968). Intact sparrows previously birds were used to determine whether the feeding activity of normal pigeons and sparrows was rhythmic in DD and to determine whether the feeding and locomotor rhythms in DD would exhibit similar period and length of daily activity bout (alpha). Intact pigeons and sparrows were first entrained to an LD cycle and then placed in DD until the experiment was terminated, after 45-150 days for pigeons and 60-120 days for sparrows. Since no differences were seen between sham-operated and intact birds, the data were pooled. Pigeons and sparrows were PX to determine the role of the pineal in the maintenance of circadian rhythmicity and to test for differential effects of PX on locomotor and feeding rhythms. PX was performed according to one of the following methods: 1. Four pigeons were PX as described by Ebihara et al. (1984). 2. In four other pigeons the procedure was changed. Under anesthesia (60 mg/kg Ketamine followed by 10 mg/kg Nembutal), a skull cap (1.0 cm diameter) was removed from directly above the sagittal sinus, and the sinus was ligated rostrally and retracted to expose the pineal stalk. The stalk was detached from its connection with the brain by pulling upwards. A portion of the sinus, with the pineal body and stalk attached, was then excised. The excised tissue was examined under a dissecting microscope to confirm visually that the entire pineal gland and stalk was removed. Because there were no apparent differences in the responses of the pigeons to the two PX procedures, the PX pigeon data were pooled for analysis. 3. Sparrows were PX as previously described (Gaston and Menaker, 1968). After entrainment to an LD cycle for at least 10 days, the PX pigeons and sparrows were placed in DD for the remainder of the experiment. =
=
=
=
EXPERIMENT 2 : THE EFFECTS OF MELATONIN IMPLANTS ON FEEDING AND LOCOMOTOR RHYTHMS Melatonin-filled silastic implants (1.0-cm length of Dow Coming No. 602-235, 1.47 mm inner diameter and 1.96 mm outer diameter) were prepared as described by Turek et al. (1976). The melatonin release rate from these capsules was demonstrated to be directly proportional to capsule length in house sparrows (Turek et al., 1976; 4wg/day/5-mm length of capsule). Intact pigeons (n 4) and sparrows (n 4) were entrained to an LD cycle and then placed in DD (pigeons, 25-35 days; sparrows, 75-100 days). The birds, freerunning under these DD conditions, were removed from their cages into the light, and melatonin-filled silastic capsules were placed in the peritoneal cavity as previously described (Turek et al., 1976). Two pigeons received 11capsules, one received 8, and one received 6. The doses for these pigeons, based on the rate determined for house sparrows (Turek et al., 1976), were 88, 64, and 48 pLg/day, respectively. The four house sparrows each received one 5-mm capsule (dose 4 p,g/day; Turek et al., 1976). After recovery the pigeons and =
=
289
sparrows were returned to their cages in DD. Several weeks later, all pigeons and two of four sparrows were again removed from their cages, and the melatonin capsules were removed. After recovery, the birds were replaced in their cages in DD until the experiment was terminated several weeks later. The implants were allowed to remain in situ in the other two sparrows until the experiment was terminated 120 days later.
EXPERIMENT 3 : THE EFFECTS OF LL ON FEEDING AND LOCOMOTOR RHYTHMS
Intact pigeons (n 4) and sparrows (n 9) were entrained to LD for at least 10 days and then were placed in one of several intensities of LL (measured at head height). From 2 to 9 weeks later, after a stable response to the initial intensity of LL was achieved, the intensity was changed; it was decreased if the initial response was arrhythmic feeding and locomotor behavior, or increased if the response was rhythmic behavior. From 3 to 5 weeks later, after the behaviors had once again stabilized, the intensity was either increased or decreased, depending on the observed activity patterns as in the previous set of treatments. In total, three pigeons were subjected to three different intensities of LL (0.5, 0.7, and 0.17 lux), and one pigeon was subjected to four different intensities of LL (0.17, 0.35, 0.7, and 1.0 lux). Two intact sparrows were treated in a manner similar to that described above, while the remaining seven sparrows were each exposed to only one LL intensity (range 0.17-150 =
=
lux).
DATA ANALYSIS
The period, alpha, and phase difference between the daily onsets and/or ends of locomotor and feeding rhythms were measured for all of the free-running locomotor and feeding activities that exhibited clear onsets or ends. The period was determined from the slope of a best eye-fitted line drawn through the onsets or ends of the activities. In pigeons the ends of activity were used, whereas in sparrows the onsets of activity were used, since these were usually observed to be more consistent in the respective species. The difference in time between the eye-fitted lines drawn for feeding and locomotor activity for individual birds was recorded as the phase angle difference. A positive phase difference indicates that locomotor activity ended after feeding activity (pigeons) or began before feeding activity (sparrows). Alphas of feeding and locomotor activity were calculated by drawing best eyefitted lines through the onsets and the ends of activity and determining the amount of time between the two lines. Means and standard error of the means (SEM) were calculated separately for period, phase differences, and alphas of all four (intact, PX, melatonin implants, and LL) experimental groups. Differences between periods and alphas of feeding and locomotor rhythms were analyzed using paired and unpaired Student’st tests as appropriate. Values were considered significantly different if p < 0.05. The locomotor rhythm was disrupted (the clarity of the rhythm was decreased sufficiently to preclude analysis) in two out of the eight PX pigeons, and feeding and locomotor rhythms were abolished (rhythmicity could not be visually discerned) in all four PX sparrows. Therefore, neither the feeding nor locomotor records of these PX pigeons or sparrows were included in the quantitative analyses. 290
RESULTS
EXPERIMENT 1: INTACT AND PX PIGEONS AND SPARROWS IN LD AND DD The
feeding and locomotor activities of both intact and PX pigeons and sparrows entrained to an LD 12:12 cycle, with nearly all of both activities taking place in the light portion of the cycle. In both intact sparrows and pigeons, feeding and locomotor rhythms free-ran in DD with similar periods (Figure 1, Table 1). In two of the eight PX pigeons, the locomotor
rhythms of locomotor and feeding activity from an intact pigeon (top panels) and sparrow (bottom panels). The pigeon and sparrow were in LD cycles for the first several days of these records (lights-on, up arrows; lights-off, down arrows) and in DD (horizontal arrows) for the remainder of the experiment. The records are double-plotted to facilitate visual inspection of the data. The sparrow data were collected from a microswitch attached to the perch across the cage from the feeding perch. Pigeon locomotor data for days 39-49 were lost because of a data acquisition hardware problem. FIGURE 1. Circadian
291
TABLE 1. Characteristics
Rhythms During
or
(Means ± SEM; in Hours) of Free-Running Feeding and Locomotor
Following
Four Different Treatments
Note. n’s for subgroups are m parentheses. Phase angle numbers represent the average daily amount of time (hours) that locomotor activity began before (sparrows) or ended after (pigeons) feedmg activity. LL data are pooled from all mtensities in which clear feeding and locomotor activity was observed. Data for melatomn-implanted birds are from feeding and locomotor rhythms after melatonm implants were removed. Statistical differences (p < 0.05) between feeding and locomotion means are indicated by different letters.
rhythm was disrupted (but rhythmic) in DD, whereas their feeding activity was clearly rhythmic (data not shown). Although the feeding and locomotor rhythms from the PX pigeon shown in Figure 2 are less clear (robust) than the data from the intact one shown in Figure 1, these results were not consistently observed. Several of the behavioral records from PX pigeons were clearer than the behavioral records from two of the intact pigeons. In all four sparrows, both feeding and locomotor rhythms were abolished by PX (Fig. 2). There were no significant differences between the feeding and locomotor free-running periods in intact sparrows, intact pigeons, or PX pigeons. The locomotor activity alpha was significantly larger than the feeding activity alpha in DD for both intact and PX pigeons, and the phase angle difference between the two behavioral rhythms was positive in both (Table 1). In intact sparrows, feeding and locomotor alphas were not statistically different. The effects of several different experimental conditions on feeding and locomotor rhythms in pigeons and house sparrows
are
summarized in Table 2.
EXPERIMENT 2 : MELATONIN IMPLANTS
Constant release of large doses of melatonin from silastic implants abolished rhythmicity initially in all pigeons and sparrows subjected to this treatment in DD (Fig. 3). In all four pigeons and two of the four sparrows, the rhythms were abolished for as long as the capsules remained implanted. When the capsules were removed, rhythmicity was immediately restored to both behaviors in these individuals. Thereafter, both feeding and locomotor rhythms in individuals exhibited virtually identical free-running periods with stable phase relationships 292
FIGURE 2. Circadian rhythms of locomotor and feeding activity from a PX and sparrow were PX several weeks before the records shown here were collected from a microswitch attached to the feeding perch.
pigeon
pigeon and sparrow. began. The sparrow
The data
until the experiment was terminated several weeks later (Fig. 3, upper panel). After melatonin implant removal, the average locomotor activity alpha was longer than the average feeding activity alpha in pigeons, although the differences were not significant (p 0.051). A similar trend was observed in sparrows (Table 1). In two of the four sparrows that received melatonin implants, both feeding and locomotor rhythms were abolished after implantation for several days, but clear rhythms became apparent within a few days for one individual and after several weeks for another. Whereas in one of these sparrows there was only one free-running component in each behavior (data not shown), in the other sparrow two components were apparent (Fig. 3, lower panel). The periods of feeding and locomotor rhythms observed in these melatonin-implanted individuals and the two sparrows from which the capsules were =
removed
were
virtually
identical.
EXPERIMENT 3 : INTACT PIGEONS AND SPARROWS IN LL
Figure 4, both feeding and exposed to LL. This occurred In
locomotor rhythms in three of the four
are
shown to have
persisted
pigeons tested; however, in
in
a
one
pigeon pigeon, 293
3
0 M
~°
.~ ~ = ’E (J 0 . . . ~ 0 8 ~
O U X -0 p, N > g8°S~S
-Ë~~~ -..~~~ ~~ ~ fl
£ §b§b~
~SECQ
294
FIGURE 3. Effect of melatonin-filled silastic implants on the free-running rhythm of locomotor and feeding activity of an intact pigeon and sparrow. Top panels: On day 41, eleven 1.0-cm melatoninfilled silastic capsules were implanted intraperitoneally, and the pigeon was placed back in DD (arrows). Several weeks later, the capsules were removed (arrows), and the bird was maintained in DD for the remainder of the experiment. Bottom panels: On day 17, one 5.0-mm capsule was implanted, and the sparrow was placed back into DD (arrows). The sparrow data were collected from a microswitch attached to the feeding perch.
295
FIGURE 4. Circadian rhythms of locomotor and feeding activity of an intact pigeon and sparrow m LL. Top panels: The first LL intensity was 0.5 lux (arrows); it was then increased to 0.7 lux for 4 weeks and was finally decreased to 0.17 lux. Bottom panels: LL intensity 150 lux. The sparrow data were collected from a microswitch attached to the feedmg perch. =
clear feeding and locomotor rhythms did not persist at any LL intensity tested (0.7, 0.25, or 0.17 lux). In the other three pigeons, both rhythms were disrupted when the LL intensity was increased sufficiently (Figure 4). In those free-running patterns that were discernible, the average periods of the feeding and of the locomotor rhythms were similar (Table 1). Although the average locomotor alpha was slightly longer than the average feeding alpha, the differences were not statistically different. The average phase differences between locomotor and feeding activity in pigeons in LL versus DD were not statistically distinguishable. Significant effects of LL intensity on free-running pigeon feeding and locomotor periods were not observed, perhaps because of the small number of experimental subjects. In sparrows, both feeding and locomotor rhythms were generally abolished at higher LL intensities and clear at lower intensities. However, the behavioral rhythms of one individual exposed to bright LL, though initially abolished, were clearly evident after a few weeks (Fig. 4). Exposure to any of the LL intensities used in these experiments did not appear to differentially affect feeding and locomotor rhythms in sparrows. The average phase differences between locomotor and feeding activity in sparrows in LL versus DD were not statistically distinguishable.
296
The average
significantly
periods of feeding and locomotor rhythms of sparrows observed in LL shorter than those of sparrows in DD (Table 1).
were
DISCUSSION Our results indicate that feeding activity in homing pigeons and house sparrows maintains rhythmicity in constant conditions with a period slightly different from 24 hr, and is therefore regulated by a circadian oscillatory system. Perturbations known to disrupt locomotor and circulating melatonin rhythms in birds-PX (Gaston and Menaker, 1968; Norris, 1981; Foa and Menaker, 1988), exposure to LL (Oshima et al., 1989b), and implantation of melatonin capsules (Turek et al., 1976; Oshima et al., 1989a)-also disrupt the circadian rhythms of feeding activity. These results suggest that melatonin, demonstrated to be important in the maintenance of locomotor rhythmicity in birds (Chabot, 1990), is also involved in the maintenance of circadian feeding rhythms in pigeons and sparrows. Feeding and locomotor rhythmicities appear nearly identical in pigeons and sparrows that are intact, melatonin-implanted, or subjected to LL. It is interesting to note that even under conditions sufficient to split the activities into two rhythmic components, the patterns of feeding and locomotor activities appear virtually identical (Fig. 3). The spatial organization of the recording cages used in this study required that the birds activate a locomotor microswitch at least once in order to feed and drink. The physical arrangement raises the question of the independence of feeding and locomotor activity measurements. However, significant differences between feeding and locomotor activity were observed in pigeons (Table 1); and in sparrows, while dozens of perch hops were usually recorded during feeding bouts, only one was necessary in order for them to feed. Starlings tested in similar experimental cages do exhibit clear differences in the circadian control of these two behaviors (Ganshirt et al., 1984; Subbaraj and Gwinner, 1985; Gwinner et al., 1987). These results suggest both that our experimental set-up was sufficient to delineate circadian differences between these two behaviors, and that the temporal correlation between feeding and locomotor activities in sparrows was not a result of the geometry of the cage. Our data and Gwinner’s (1989) demonstrate that PX abolishes both of these rhythms in sparrows. In pigeons, both feeding and locomotor rhythms can be entrained in PX individuals and restored in PX/bilaterally enucleated individuals by physiological amounts of melatonin infused in normal temporal patterns (Chabot, 1990; Chabot and Menaker, 1992). Thus, in pigeons and sparrows, these behaviors may be controlled by the same circadian oscillatory system. The circadian rhythm of body temperature may also be controlled by the same system; in pigeons, Oshima et al. (1989a) have shown that PX and/or bilateral enucleation affected temperature and locomotor rhythms similarly, and Binkley et al. (1971) have shown that PX abolishes both of these rhythms in sparrows. Alternatively, there may be separate, strongly coupled oscillatory systems that control individual circadian outputs in pigeons and sparrows. Although there are no data that require such an interpretation, this possibility may be very difficult to rule out experimentally. Our results do show some differences between feeding and locomotor rhythms in pigeons. Under free-running conditions in both LL and DD, locomotor activity began before, and ended after, feeding activity. Although PX did not affect the clarity of feeding rhythms in any of the eight pigeons subjected to this procedure, locomotor rhythmicity was disrupted
297
in two of these eight birds. In addition, the feeding rhythm for any given pigeon or sparrow was often clearer than its locomotor rhythm. Although these differences in some of the qualities of the two free-running rhythms were consistent, the periods of the two rhythms were always nearly identical in both species. These results suggest to us that the differences are reflections of differences in the output pathways to the two behaviors from a single circadian pacemaker. In pigeons and starlings (and perhaps sparrows), feeding rhythms are more robust and resistant to perturbations than are locomotor rhythms. Feeding rhythms persist in both PX pigeons (Fig. 2) and PX starlings (Gwinner et al., 1987), whereas locomotor rhythms are abolished in some individuals of either species. In starlings, PX (Gwinner et al., 1987) and exposure to LL (Ganshirt et al., 1984) have been found to have different effects on locomotor and feeding rhythms. Also in starlings, testosterone implants differentially affect the daily activity bout length (alpha) of feeding and locomotor rhythms (Subbaraj and Gwinner, 1985). Although either PX or LL disrupts locomotor rhythmicity under some circumstances, neither is able to abolish feeding rhythmicity in starlings. Gwinner et al. (1987) have suggested that one circadian system may control both behaviors, but that the coupling of the locomotor behavior may be weaker than the coupling of the feeding behavior to the circadian system. This hypothesis is supported by observations that the feeding and locomotor rhythms were never dissociated; that is, they never free-ran with different periods. Our data in pigeons and sparrows are consistent with this hypothesis. On the basis of our present findings and those of Gwinner et al. (1987), we propose that the difference in coupling strength is small in sparrows, slightly greater in pigeons, and even greater in starlings.
ACKNOWLEDGMENTS
This research was supported by National Institutes of Health Grant No. HD13162 to Michael Menaker. Our sincere thanks are given to Heather Chabot, Christopher Colwell, and Denms Liu for helping to capture house sparrows, and to Christopher Colwell and Nancy Wayne for cntical review of this paper.
REFERENCES
ASCHOFF, J., and R. WEVER (1976) Human circadian : rhythms: A multi-oscillator system. Fed. Proc. 35 2336-2343.
Arrhythmic perch hopping and rhythmic feeding in constant light: Separate circadian oscillators? J. Comp. Physiol. 154: 669-674.
BINKLEY, S., E. KLUTH, and M. MENAKER (1971) Pineal
GWINNER, E. (1989) Melatonin in the circadian system
function in sparrows: Circadian rhythms and body temperature. Science 174: 311-314. CHABOT, C. C. ( 1990) Melatonin Regulation of Feeding and Locomotor Rhythms in the Pigeon, Columba livia, PhD dissertation, University of Virginia. CHABOT, C. C., and M. MENAKER (1992) Effects of physiological cycles of infused melatonin on circadian rhythmicity in pigeons. J. Comp. Physiol. A 170: 615-622. FOÀ, A., and M. MENAKER (1988) Blood melatonin rhythms in the pigeon. J. Comp. Physiol. 164: 2530. GASTON, S., and M. MENAKER (1968) Pineal function: The biological clock in the sparrow? Science 160: 1125-1127. GANSHIRT, G., S. DAAN, and M. P. GERKEMA (1984)
of birds: Model of internal resonance. In Circadian Clocks and Ecology, T. Hiroshige and K. Honma, eds., pp. 127-145, Hokkaido University Press, Sap-
298
poro,
Japan.
GWINNER, E., R. SUBBARAJ, C. K. BLUHM, and M. GERKEMA (1987) Differential effects of pinealectomy circadian rhythms of feeding and perch hopping in the European starling. J. Biol. Rhythms 2: 109129. MENAKER, M. (1965) Circadian rhythms and photoperiodism in Passer domesticus. In Circadian Clocks, J. Aschoff, ed., pp. 385-395, North-Holland, Amsterdam. MENAKER, M., and A. ESKIN (1966) Entrainment of circadian rhythms by sound in Passer domesticus. Science 157: 1058-1061. on
NORRIS, C. J. (1981) Circulating Levels of Melatonin in the House Sparrow, Passer domesticus, MA thesis, of Texas. OSHIMA, I., H. YAMADA, M. GOTO, K. SOTO, and S. EBIHARA (1989a) Pineal and retinal melatonin is involved in the control of circadian locomotor activity and body temperature rhythms in the pigeon. J. Comp. Physiol. 166: 217-226. OSHIMA, I., H. YAMADA, K. SATO, and S. EBIHARA (1989b) The role of melatonin in the circadian system of the pigeon, Columba livca. In Circadian Clocks and Ecology, T. Hiroshige and K. Honma, eds., pp. 118-127, Hokkaido University Press, Sapporo, Japan. PITTENDRIGH, C. S., and S. DAAN (1976) A functional analysis of circadian pacemakers in nocturnal rodents: V. Pacemaker structure: A clock for all seasons. J Comp. Physiol. 106: 333-355.
University
STEPHAN, F. K., J. M. SWANN, and C. L. SISK (1979) of 24-hr feeding schedules in rats with lesions of the suprachiasmatic nucleus. Behav. Neural Biol. 25: 346-363. SUBBARAJ, R., and E. GWINNER (1985) Differential effects of testosterone on the circadian rhythms of locomotor activity and feeding in the European starling. Naturwissenschaften 72: 663-664. TUREK, F. W., J. P. MCMILLAN, and M. MENAKER (1976) Melatonin: Effects on the circadian locomotor rhythm : 1441-1443. of sparrows. Science 194 YAMADA, H., I. OSHIMA, K. SATO, and S. EBIHARA (1988) Loss of circadian rhythms of locomotor activity, food intake, and plasma melatonin concentration induced by constant bright light in the pigeon. ( Columba livia). J. Comp. Physiol. 163: 459-463.
Anticipation
299
Rhythms
in
1 and Michael Menaker Christopher C. Chabot Department of Biology, University of Virginia, Charlottesville, Virginia 22903 Abstract Feeding and locomotor activities were measured simultaneously in homing pigeons (Columba livia) and house sparrows (Passer domesticus). Feeding, as well as locomotor activity, was found to be regulated by a circadian clock in both of these species. Implantation of melatonin-filled capsules or exposure to constant light abolished feeding and locomotor rhythms in both species. Removal of the pineal gland from pigeons did not abolish either rhythm, whereas pinealectomy abolished both feeding and locomotor rhythms in house sparrows. Although feeding rhythms were generally more robust than locomotor rhythms in both of these species, different feeding and locomotor free-running periods were not observed within any individual pigeon or house sparrow. These results are consistent with the hypothesis that each of these species has a single pacemaker that regulates the timing of feeding and locomotor activity, but they do not rule out the possibility that separate clocks regulate these behaviors.
Key words rhythms, behavior, feeding, locomotion, light, pineal, birds, melatonin, oscillator, circadian
One of the central issues in the field of circadian biology concerns the regulation of multiple circadian outputs, such as feeding and locomotor activity. Although multiple outputs may conceivably be regulated by a single oscillatory system, there is some evidence that separate oscillators control different outputs in humans (Aschoff and Wever, 1976), rodents (Pittendrigh and Daan, 1976; Stephan et al., 1979), and birds (Ganshirt et al., 1984). In birds it is unclear whether the circadian system that regulates locomotor rhythms also regulates other behavioral rhythms. While much is known about the regulation of locomotor rhythms, other rhythmic outputs, such as feeding, have not been well characterized. In birds, circadian rhythms of feeding activity have only been measured in house sparrows, starlings, and pigeons. Studies in which either surgical or environmental manipulations were performed suggest that the three species differ in their responses to similar treatments. For example, following pinealectomy (PX) the feeding rhythm is abolished in house sparrows (Gwinner, 1989), but not in starlings (Gwinner et al., 1987). In pigeons it has been claimed that feeding rhythms do not persist in bright constant light (LL) (Yamada et al., 1988). In starlings the regulation of feeding rhythms may be fundamentally different from the regulation of locomotor rhythms (Ganshirt et al., 1984).
1. Present
address,
College, Plymouth,
which all correspondence should be New Hampshire 03264.
to
sent:
Department
of Natural
Sciences, Plymouth State
287
We have begun to address the question of circadian regulation of feeding in homing pigeons and house sparrows by monitoring both feeding and locomotor activity simultaneously and exposing these birds to conditions known to affect locomotor rhythms. The purpose of the present series of experiments was to make a systematic attempt to determine whether feeding activity in pigeons and house sparrows is under circadian control, and if so, to determine whether procedures known to affect locomotor rhythms in these species affect
feeding rhythms
in
a
similar
manner.
MATERIALS AND METHODS
EXPERIMENTAL BIRDS AND HOUSING CONDITIONS The homing pigeons (Columba livia; males and females, 400-600 g) used in this experiment were obtained from suppliers in Waco, TX (Louis Nicosia) and Eugene, OR (University of Oregon), and maintained either outdoors under natural lighting conditions or indoors under an artificial light-dark (LD) cycle of 12 hr light and 12 hr darkness (LD 12:12) prior to experimentation. House sparrows (Passer domesticus; males and females, 20-30 g) were wild-caught in Eugene, OR and maintained indoors under LD 12:12 conditions prior to experimentation. During the study, pigeons were individually housed in tilt-bottom cages (35 cm x 38 cm x 26 cm) suspended over a pan filled with bedding (Bed-O-Cob, The Andersons, Maumee, OH) within light-tight wooden boxes. House sparrows were also individually housed during the study in cages lacking a tilt bottom, as previously described
(Menaker, 1965). The light-tight boxes containing pigeons and sparrows were kept in a dark, temperaturecontrolled (23°C) room in which white noise (93 dBA) was continuously present (Menaker and Eskin, 1966). Lighting was provided in the experimental cages with a 4-W &dquo;cool white&dquo; fluorescent bulb (Ken Rad F4T5/cw). Light levels were measured with a Luna Pro light meter (Gossen, Germany). Food and water were available ad libitum at opposite ends of the cages and were replaced at approximately weekly intervals. Bedding was replaced at approximately biweekly intervals. An infrared viewer (FJW Optical Systems, Elgin, IL) was used to attend to birds held in constant darkness (DD). Birds were always allowed at least 10 days in an LD 12:12 cycle when first placed in the cage (light intensity during L was approximately 150 lux). Locomotor activity was monitored with two microswitches connected to the tilt bottom for pigeons and with one microswitch connected to one of two perches for sparrows (approximately 50% of the sparrows were housed in cages with a microswitch attached to the perch next to the food; the microswitch was attached to the other perch in the other 50%). Feeding activity was monitored for both species with an infrared emitter-detector pair mounted across a food access hole. Thus, birds were always exposed to constant levels of infrared light from the infrared emitter. All sparrow behavioral data were collected on an event recorder (Esterline-Angus, Indianapolis, IN); pigeon data were collected either on an event recorder or on a computer data acquisition system (Data Quest, Data-Sciences, Inc., Roseville, MN; EZ Paste software, M. Vogelbaum, Charlottesville,
VA).
288
EXPERIMENT l: CIRCADIAN CONTROL OF FEEDING AND THE ROLE OF THE PINEAL GLAND
Pigeons and sparrows were divided into two groups: pineal-intact (pigeons, n 11; sparrows, n 8; sparrows, n 4). Two of the six pineal-intact 6) and PX birds (pigeons, n described received sham PX as (Gaston and Menaker, 1968). Intact sparrows previously birds were used to determine whether the feeding activity of normal pigeons and sparrows was rhythmic in DD and to determine whether the feeding and locomotor rhythms in DD would exhibit similar period and length of daily activity bout (alpha). Intact pigeons and sparrows were first entrained to an LD cycle and then placed in DD until the experiment was terminated, after 45-150 days for pigeons and 60-120 days for sparrows. Since no differences were seen between sham-operated and intact birds, the data were pooled. Pigeons and sparrows were PX to determine the role of the pineal in the maintenance of circadian rhythmicity and to test for differential effects of PX on locomotor and feeding rhythms. PX was performed according to one of the following methods: 1. Four pigeons were PX as described by Ebihara et al. (1984). 2. In four other pigeons the procedure was changed. Under anesthesia (60 mg/kg Ketamine followed by 10 mg/kg Nembutal), a skull cap (1.0 cm diameter) was removed from directly above the sagittal sinus, and the sinus was ligated rostrally and retracted to expose the pineal stalk. The stalk was detached from its connection with the brain by pulling upwards. A portion of the sinus, with the pineal body and stalk attached, was then excised. The excised tissue was examined under a dissecting microscope to confirm visually that the entire pineal gland and stalk was removed. Because there were no apparent differences in the responses of the pigeons to the two PX procedures, the PX pigeon data were pooled for analysis. 3. Sparrows were PX as previously described (Gaston and Menaker, 1968). After entrainment to an LD cycle for at least 10 days, the PX pigeons and sparrows were placed in DD for the remainder of the experiment. =
=
=
=
EXPERIMENT 2 : THE EFFECTS OF MELATONIN IMPLANTS ON FEEDING AND LOCOMOTOR RHYTHMS Melatonin-filled silastic implants (1.0-cm length of Dow Coming No. 602-235, 1.47 mm inner diameter and 1.96 mm outer diameter) were prepared as described by Turek et al. (1976). The melatonin release rate from these capsules was demonstrated to be directly proportional to capsule length in house sparrows (Turek et al., 1976; 4wg/day/5-mm length of capsule). Intact pigeons (n 4) and sparrows (n 4) were entrained to an LD cycle and then placed in DD (pigeons, 25-35 days; sparrows, 75-100 days). The birds, freerunning under these DD conditions, were removed from their cages into the light, and melatonin-filled silastic capsules were placed in the peritoneal cavity as previously described (Turek et al., 1976). Two pigeons received 11capsules, one received 8, and one received 6. The doses for these pigeons, based on the rate determined for house sparrows (Turek et al., 1976), were 88, 64, and 48 pLg/day, respectively. The four house sparrows each received one 5-mm capsule (dose 4 p,g/day; Turek et al., 1976). After recovery the pigeons and =
=
289
sparrows were returned to their cages in DD. Several weeks later, all pigeons and two of four sparrows were again removed from their cages, and the melatonin capsules were removed. After recovery, the birds were replaced in their cages in DD until the experiment was terminated several weeks later. The implants were allowed to remain in situ in the other two sparrows until the experiment was terminated 120 days later.
EXPERIMENT 3 : THE EFFECTS OF LL ON FEEDING AND LOCOMOTOR RHYTHMS
Intact pigeons (n 4) and sparrows (n 9) were entrained to LD for at least 10 days and then were placed in one of several intensities of LL (measured at head height). From 2 to 9 weeks later, after a stable response to the initial intensity of LL was achieved, the intensity was changed; it was decreased if the initial response was arrhythmic feeding and locomotor behavior, or increased if the response was rhythmic behavior. From 3 to 5 weeks later, after the behaviors had once again stabilized, the intensity was either increased or decreased, depending on the observed activity patterns as in the previous set of treatments. In total, three pigeons were subjected to three different intensities of LL (0.5, 0.7, and 0.17 lux), and one pigeon was subjected to four different intensities of LL (0.17, 0.35, 0.7, and 1.0 lux). Two intact sparrows were treated in a manner similar to that described above, while the remaining seven sparrows were each exposed to only one LL intensity (range 0.17-150 =
=
lux).
DATA ANALYSIS
The period, alpha, and phase difference between the daily onsets and/or ends of locomotor and feeding rhythms were measured for all of the free-running locomotor and feeding activities that exhibited clear onsets or ends. The period was determined from the slope of a best eye-fitted line drawn through the onsets or ends of the activities. In pigeons the ends of activity were used, whereas in sparrows the onsets of activity were used, since these were usually observed to be more consistent in the respective species. The difference in time between the eye-fitted lines drawn for feeding and locomotor activity for individual birds was recorded as the phase angle difference. A positive phase difference indicates that locomotor activity ended after feeding activity (pigeons) or began before feeding activity (sparrows). Alphas of feeding and locomotor activity were calculated by drawing best eyefitted lines through the onsets and the ends of activity and determining the amount of time between the two lines. Means and standard error of the means (SEM) were calculated separately for period, phase differences, and alphas of all four (intact, PX, melatonin implants, and LL) experimental groups. Differences between periods and alphas of feeding and locomotor rhythms were analyzed using paired and unpaired Student’st tests as appropriate. Values were considered significantly different if p < 0.05. The locomotor rhythm was disrupted (the clarity of the rhythm was decreased sufficiently to preclude analysis) in two out of the eight PX pigeons, and feeding and locomotor rhythms were abolished (rhythmicity could not be visually discerned) in all four PX sparrows. Therefore, neither the feeding nor locomotor records of these PX pigeons or sparrows were included in the quantitative analyses. 290
RESULTS
EXPERIMENT 1: INTACT AND PX PIGEONS AND SPARROWS IN LD AND DD The
feeding and locomotor activities of both intact and PX pigeons and sparrows entrained to an LD 12:12 cycle, with nearly all of both activities taking place in the light portion of the cycle. In both intact sparrows and pigeons, feeding and locomotor rhythms free-ran in DD with similar periods (Figure 1, Table 1). In two of the eight PX pigeons, the locomotor
rhythms of locomotor and feeding activity from an intact pigeon (top panels) and sparrow (bottom panels). The pigeon and sparrow were in LD cycles for the first several days of these records (lights-on, up arrows; lights-off, down arrows) and in DD (horizontal arrows) for the remainder of the experiment. The records are double-plotted to facilitate visual inspection of the data. The sparrow data were collected from a microswitch attached to the perch across the cage from the feeding perch. Pigeon locomotor data for days 39-49 were lost because of a data acquisition hardware problem. FIGURE 1. Circadian
291
TABLE 1. Characteristics
Rhythms During
or
(Means ± SEM; in Hours) of Free-Running Feeding and Locomotor
Following
Four Different Treatments
Note. n’s for subgroups are m parentheses. Phase angle numbers represent the average daily amount of time (hours) that locomotor activity began before (sparrows) or ended after (pigeons) feedmg activity. LL data are pooled from all mtensities in which clear feeding and locomotor activity was observed. Data for melatomn-implanted birds are from feeding and locomotor rhythms after melatonm implants were removed. Statistical differences (p < 0.05) between feeding and locomotion means are indicated by different letters.
rhythm was disrupted (but rhythmic) in DD, whereas their feeding activity was clearly rhythmic (data not shown). Although the feeding and locomotor rhythms from the PX pigeon shown in Figure 2 are less clear (robust) than the data from the intact one shown in Figure 1, these results were not consistently observed. Several of the behavioral records from PX pigeons were clearer than the behavioral records from two of the intact pigeons. In all four sparrows, both feeding and locomotor rhythms were abolished by PX (Fig. 2). There were no significant differences between the feeding and locomotor free-running periods in intact sparrows, intact pigeons, or PX pigeons. The locomotor activity alpha was significantly larger than the feeding activity alpha in DD for both intact and PX pigeons, and the phase angle difference between the two behavioral rhythms was positive in both (Table 1). In intact sparrows, feeding and locomotor alphas were not statistically different. The effects of several different experimental conditions on feeding and locomotor rhythms in pigeons and house sparrows
are
summarized in Table 2.
EXPERIMENT 2 : MELATONIN IMPLANTS
Constant release of large doses of melatonin from silastic implants abolished rhythmicity initially in all pigeons and sparrows subjected to this treatment in DD (Fig. 3). In all four pigeons and two of the four sparrows, the rhythms were abolished for as long as the capsules remained implanted. When the capsules were removed, rhythmicity was immediately restored to both behaviors in these individuals. Thereafter, both feeding and locomotor rhythms in individuals exhibited virtually identical free-running periods with stable phase relationships 292
FIGURE 2. Circadian rhythms of locomotor and feeding activity from a PX and sparrow were PX several weeks before the records shown here were collected from a microswitch attached to the feeding perch.
pigeon
pigeon and sparrow. began. The sparrow
The data
until the experiment was terminated several weeks later (Fig. 3, upper panel). After melatonin implant removal, the average locomotor activity alpha was longer than the average feeding activity alpha in pigeons, although the differences were not significant (p 0.051). A similar trend was observed in sparrows (Table 1). In two of the four sparrows that received melatonin implants, both feeding and locomotor rhythms were abolished after implantation for several days, but clear rhythms became apparent within a few days for one individual and after several weeks for another. Whereas in one of these sparrows there was only one free-running component in each behavior (data not shown), in the other sparrow two components were apparent (Fig. 3, lower panel). The periods of feeding and locomotor rhythms observed in these melatonin-implanted individuals and the two sparrows from which the capsules were =
removed
were
virtually
identical.
EXPERIMENT 3 : INTACT PIGEONS AND SPARROWS IN LL
Figure 4, both feeding and exposed to LL. This occurred In
locomotor rhythms in three of the four
are
shown to have
persisted
pigeons tested; however, in
in
a
one
pigeon pigeon, 293
3
0 M
~°
.~ ~ = ’E (J 0 . . . ~ 0 8 ~
O U X -0 p, N > g8°S~S
-Ë~~~ -..~~~ ~~ ~ fl
£ §b§b~
~SECQ
294
FIGURE 3. Effect of melatonin-filled silastic implants on the free-running rhythm of locomotor and feeding activity of an intact pigeon and sparrow. Top panels: On day 41, eleven 1.0-cm melatoninfilled silastic capsules were implanted intraperitoneally, and the pigeon was placed back in DD (arrows). Several weeks later, the capsules were removed (arrows), and the bird was maintained in DD for the remainder of the experiment. Bottom panels: On day 17, one 5.0-mm capsule was implanted, and the sparrow was placed back into DD (arrows). The sparrow data were collected from a microswitch attached to the feeding perch.
295
FIGURE 4. Circadian rhythms of locomotor and feeding activity of an intact pigeon and sparrow m LL. Top panels: The first LL intensity was 0.5 lux (arrows); it was then increased to 0.7 lux for 4 weeks and was finally decreased to 0.17 lux. Bottom panels: LL intensity 150 lux. The sparrow data were collected from a microswitch attached to the feedmg perch. =
clear feeding and locomotor rhythms did not persist at any LL intensity tested (0.7, 0.25, or 0.17 lux). In the other three pigeons, both rhythms were disrupted when the LL intensity was increased sufficiently (Figure 4). In those free-running patterns that were discernible, the average periods of the feeding and of the locomotor rhythms were similar (Table 1). Although the average locomotor alpha was slightly longer than the average feeding alpha, the differences were not statistically different. The average phase differences between locomotor and feeding activity in pigeons in LL versus DD were not statistically distinguishable. Significant effects of LL intensity on free-running pigeon feeding and locomotor periods were not observed, perhaps because of the small number of experimental subjects. In sparrows, both feeding and locomotor rhythms were generally abolished at higher LL intensities and clear at lower intensities. However, the behavioral rhythms of one individual exposed to bright LL, though initially abolished, were clearly evident after a few weeks (Fig. 4). Exposure to any of the LL intensities used in these experiments did not appear to differentially affect feeding and locomotor rhythms in sparrows. The average phase differences between locomotor and feeding activity in sparrows in LL versus DD were not statistically distinguishable.
296
The average
significantly
periods of feeding and locomotor rhythms of sparrows observed in LL shorter than those of sparrows in DD (Table 1).
were
DISCUSSION Our results indicate that feeding activity in homing pigeons and house sparrows maintains rhythmicity in constant conditions with a period slightly different from 24 hr, and is therefore regulated by a circadian oscillatory system. Perturbations known to disrupt locomotor and circulating melatonin rhythms in birds-PX (Gaston and Menaker, 1968; Norris, 1981; Foa and Menaker, 1988), exposure to LL (Oshima et al., 1989b), and implantation of melatonin capsules (Turek et al., 1976; Oshima et al., 1989a)-also disrupt the circadian rhythms of feeding activity. These results suggest that melatonin, demonstrated to be important in the maintenance of locomotor rhythmicity in birds (Chabot, 1990), is also involved in the maintenance of circadian feeding rhythms in pigeons and sparrows. Feeding and locomotor rhythmicities appear nearly identical in pigeons and sparrows that are intact, melatonin-implanted, or subjected to LL. It is interesting to note that even under conditions sufficient to split the activities into two rhythmic components, the patterns of feeding and locomotor activities appear virtually identical (Fig. 3). The spatial organization of the recording cages used in this study required that the birds activate a locomotor microswitch at least once in order to feed and drink. The physical arrangement raises the question of the independence of feeding and locomotor activity measurements. However, significant differences between feeding and locomotor activity were observed in pigeons (Table 1); and in sparrows, while dozens of perch hops were usually recorded during feeding bouts, only one was necessary in order for them to feed. Starlings tested in similar experimental cages do exhibit clear differences in the circadian control of these two behaviors (Ganshirt et al., 1984; Subbaraj and Gwinner, 1985; Gwinner et al., 1987). These results suggest both that our experimental set-up was sufficient to delineate circadian differences between these two behaviors, and that the temporal correlation between feeding and locomotor activities in sparrows was not a result of the geometry of the cage. Our data and Gwinner’s (1989) demonstrate that PX abolishes both of these rhythms in sparrows. In pigeons, both feeding and locomotor rhythms can be entrained in PX individuals and restored in PX/bilaterally enucleated individuals by physiological amounts of melatonin infused in normal temporal patterns (Chabot, 1990; Chabot and Menaker, 1992). Thus, in pigeons and sparrows, these behaviors may be controlled by the same circadian oscillatory system. The circadian rhythm of body temperature may also be controlled by the same system; in pigeons, Oshima et al. (1989a) have shown that PX and/or bilateral enucleation affected temperature and locomotor rhythms similarly, and Binkley et al. (1971) have shown that PX abolishes both of these rhythms in sparrows. Alternatively, there may be separate, strongly coupled oscillatory systems that control individual circadian outputs in pigeons and sparrows. Although there are no data that require such an interpretation, this possibility may be very difficult to rule out experimentally. Our results do show some differences between feeding and locomotor rhythms in pigeons. Under free-running conditions in both LL and DD, locomotor activity began before, and ended after, feeding activity. Although PX did not affect the clarity of feeding rhythms in any of the eight pigeons subjected to this procedure, locomotor rhythmicity was disrupted
297
in two of these eight birds. In addition, the feeding rhythm for any given pigeon or sparrow was often clearer than its locomotor rhythm. Although these differences in some of the qualities of the two free-running rhythms were consistent, the periods of the two rhythms were always nearly identical in both species. These results suggest to us that the differences are reflections of differences in the output pathways to the two behaviors from a single circadian pacemaker. In pigeons and starlings (and perhaps sparrows), feeding rhythms are more robust and resistant to perturbations than are locomotor rhythms. Feeding rhythms persist in both PX pigeons (Fig. 2) and PX starlings (Gwinner et al., 1987), whereas locomotor rhythms are abolished in some individuals of either species. In starlings, PX (Gwinner et al., 1987) and exposure to LL (Ganshirt et al., 1984) have been found to have different effects on locomotor and feeding rhythms. Also in starlings, testosterone implants differentially affect the daily activity bout length (alpha) of feeding and locomotor rhythms (Subbaraj and Gwinner, 1985). Although either PX or LL disrupts locomotor rhythmicity under some circumstances, neither is able to abolish feeding rhythmicity in starlings. Gwinner et al. (1987) have suggested that one circadian system may control both behaviors, but that the coupling of the locomotor behavior may be weaker than the coupling of the feeding behavior to the circadian system. This hypothesis is supported by observations that the feeding and locomotor rhythms were never dissociated; that is, they never free-ran with different periods. Our data in pigeons and sparrows are consistent with this hypothesis. On the basis of our present findings and those of Gwinner et al. (1987), we propose that the difference in coupling strength is small in sparrows, slightly greater in pigeons, and even greater in starlings.
ACKNOWLEDGMENTS
This research was supported by National Institutes of Health Grant No. HD13162 to Michael Menaker. Our sincere thanks are given to Heather Chabot, Christopher Colwell, and Denms Liu for helping to capture house sparrows, and to Christopher Colwell and Nancy Wayne for cntical review of this paper.
REFERENCES
ASCHOFF, J., and R. WEVER (1976) Human circadian : rhythms: A multi-oscillator system. Fed. Proc. 35 2336-2343.
Arrhythmic perch hopping and rhythmic feeding in constant light: Separate circadian oscillators? J. Comp. Physiol. 154: 669-674.
BINKLEY, S., E. KLUTH, and M. MENAKER (1971) Pineal
GWINNER, E. (1989) Melatonin in the circadian system
function in sparrows: Circadian rhythms and body temperature. Science 174: 311-314. CHABOT, C. C. ( 1990) Melatonin Regulation of Feeding and Locomotor Rhythms in the Pigeon, Columba livia, PhD dissertation, University of Virginia. CHABOT, C. C., and M. MENAKER (1992) Effects of physiological cycles of infused melatonin on circadian rhythmicity in pigeons. J. Comp. Physiol. A 170: 615-622. FOÀ, A., and M. MENAKER (1988) Blood melatonin rhythms in the pigeon. J. Comp. Physiol. 164: 2530. GASTON, S., and M. MENAKER (1968) Pineal function: The biological clock in the sparrow? Science 160: 1125-1127. GANSHIRT, G., S. DAAN, and M. P. GERKEMA (1984)
of birds: Model of internal resonance. In Circadian Clocks and Ecology, T. Hiroshige and K. Honma, eds., pp. 127-145, Hokkaido University Press, Sap-
298
poro,
Japan.
GWINNER, E., R. SUBBARAJ, C. K. BLUHM, and M. GERKEMA (1987) Differential effects of pinealectomy circadian rhythms of feeding and perch hopping in the European starling. J. Biol. Rhythms 2: 109129. MENAKER, M. (1965) Circadian rhythms and photoperiodism in Passer domesticus. In Circadian Clocks, J. Aschoff, ed., pp. 385-395, North-Holland, Amsterdam. MENAKER, M., and A. ESKIN (1966) Entrainment of circadian rhythms by sound in Passer domesticus. Science 157: 1058-1061. on
NORRIS, C. J. (1981) Circulating Levels of Melatonin in the House Sparrow, Passer domesticus, MA thesis, of Texas. OSHIMA, I., H. YAMADA, M. GOTO, K. SOTO, and S. EBIHARA (1989a) Pineal and retinal melatonin is involved in the control of circadian locomotor activity and body temperature rhythms in the pigeon. J. Comp. Physiol. 166: 217-226. OSHIMA, I., H. YAMADA, K. SATO, and S. EBIHARA (1989b) The role of melatonin in the circadian system of the pigeon, Columba livca. In Circadian Clocks and Ecology, T. Hiroshige and K. Honma, eds., pp. 118-127, Hokkaido University Press, Sapporo, Japan. PITTENDRIGH, C. S., and S. DAAN (1976) A functional analysis of circadian pacemakers in nocturnal rodents: V. Pacemaker structure: A clock for all seasons. J Comp. Physiol. 106: 333-355.
University
STEPHAN, F. K., J. M. SWANN, and C. L. SISK (1979) of 24-hr feeding schedules in rats with lesions of the suprachiasmatic nucleus. Behav. Neural Biol. 25: 346-363. SUBBARAJ, R., and E. GWINNER (1985) Differential effects of testosterone on the circadian rhythms of locomotor activity and feeding in the European starling. Naturwissenschaften 72: 663-664. TUREK, F. W., J. P. MCMILLAN, and M. MENAKER (1976) Melatonin: Effects on the circadian locomotor rhythm : 1441-1443. of sparrows. Science 194 YAMADA, H., I. OSHIMA, K. SATO, and S. EBIHARA (1988) Loss of circadian rhythms of locomotor activity, food intake, and plasma melatonin concentration induced by constant bright light in the pigeon. ( Columba livia). J. Comp. Physiol. 163: 459-463.
Anticipation
299
