completed yolk in a follicle, and because of the lag period,still have 4 days for courtship and mating before laying herfirst egg. However, we have no evidence, that the lagperiod varies according to environmental conditions orbehavior, or that it is restricted to species that begin yolkformation prior to the stimulation of mating behavior.

• The time between arrival and laying varied from 8 to 14days, with a mean of 10.3 ± 1.55. When added to the sea icesojourn of at least 1 day and the 3 to 4 days that elapsedbetween laying of the first and second eggs, the total timethat females spent away from the sea in their initial visit tothe colony was 13-22 days.

This research was supported by National Science Foundationgrant DPP 81-00159.

ReferencesAinley, D. C., and LaResche, R. E. 1973. The effects of weather and ice

conditions on breeding in Adelie penguins. Condor, 75, 235-238.Astheimer, L., Roudybush, T. E., and Grau, C. R. 1980. Timing and

energy requirements of egg synthesis in Cassin's auklet. Pacific SeabirdGroup Bulletin, 6(2), 29. (Abstract)

Grau, C. R. 1976. Ring structure of avian egg yolk. Poultry Science, 55,418-422.

Grau, C. R. 1982. Egg formation in Fiordland crested penguins (Eudyptespachyrhynchus). Condor, 84, 172-177.

Grau, C. R., and Wilson, G. 1980. Yolk formation in Adélie penguin eggs.Christchurch, New Zealand: University of Canterbury, Departmentof Zoology, Research Unit.

Hirsch K. V., and Grau, C. R. 1981. Yolk formation and oviposition incaptive emus. Condor, 83, 381-382.

Circadian rhythms in the bodytemperature of Adélie penguins

BRUCE M. HALPRYN, PAUL C. TIRRELL, and DAVID E. MURRISH

Department of Biological SciencesState University of New York-Binghamton

Binghamton, New York 13901

Many behavioral, physiological, and biochemical characteris-tics of organisms are not constant in time, but rather exhibitpronounced variation. Variations that occur with a dailyperiodicity are called circadian rhythms. The term circadian isused because when there is no temporal information from theenvironment, the natural period of such rhythms normally isstill approximately 24 hours. In nature, 24-hour environmentalcues serve to reset the "biological clock." This process, known asentrainment, ensures that the period of these rhythms is exactly24.0 hours, thereby permitting a constant phase relationshipwith solar time. The light-dark cycle experienced by an organ-ism is one of the most potent synchronizers for circadianrhythms. In Antarctica, the natural lighting varies from contin-uous light during the austral summer to continuous darknessduring the winter. This situation raises interesting questionsregarding the 24-hour rhythms of organisms that live in theselatitudes.

We examined the natural circadian rhythm of body tempera-ture of Adélie penguins, Pygoscelis adeliae, during the australsummer of 1981-82. During the study there was no time ofcomplete darkness, but there were some hours of twilight eachnight. The lighting intensity at these latitudes in January variesfrom greater than 50,000 lux during sunlight days to less than1,000 lux during twilight (Gallardo and Piezzi 1973). Light inten-sity and quality during the study varied considerably duringthe day because of cloud cover.

Six Adélie penguins were captured in the vicinity of PalmerStation. Each bird was anesthetized with halothane, and a bodytemperature transmitter (AVM Instruments, Inc.) was im-

39.0

C.)

wccI-

38.5CL.

wI->.

0ca

3801 _III I Ad I I I08:00 12:0016:0020:0000:0004:00 08:00

TIME OF DAY

Figure 1. Rhythm In body temperature of a representative Adéilepenguin. Each point is the average of data at each time for an 8-dayperiod.

planted in its abdominal cavity. Lidocaine was used as a localanesthetic. After recovery, the penguins were confined in out-door cages that were partially protected from the weather. Read-ings of body temperature were taken at half-hour intervalsthroughout the 5-10-day study period.

A representative body temperature rhythm of an Adélie pen-guin is shown in figure 1. The temperature values are averagesof temperatures at identical times of day over 8 days. For thisbird, the acrophase of the body temperature rhythm—that is,the high point of the cycle—occurred at 1400 hours. The acro-phase for all the penguins was between 1400 and 1700 hours.The nadir, or low point, for each bird occurred approximately 12hours later. The day-night temperature difference for all thebirds averaged 1.00 ± 0.3°C.

To characterize the periodicity in the data, spectral analysiswas used. The data were analyzed by a computer program thatfits cosine functions to the raw data. Using a least squarestechnique, the periods with the maximum amplitude were de-

182 ANTARCTIC JOURNAL

U

w

I--j

0101622283440PERIOD, HOURS

Figure 2. Spectral analysis of body temperature data within a rangeof 10 to 40 hours from an Adélie penguin.

termined (Sulzman in press). Figure 2 shows the results ofperiod spectral analysis for the same bird as in figure 1.Theamplitude periods we examined between 10 and 40 hours areplotted in half-hour increments. The major peak in this bird is at24 hours. All birds examined had significant (P > .001)periodicity in the 24-hour range.

Adélie penguins clearly demonstrate a 24-hour rhythm inbody temperature. Research also has established that these

antarctic birds have at least one other rhythm and do not pos-sess some others. For example, Derksen (1977) found that dur-ing the time Adélie penguins were incubating their eggs, therewas a circadian rhythm of activity in the colony as a whole,though this rhythm was not evident in individual penguins.Another common diurnal rhythm found in birds, melatoninsynthesis, could not be demonstrated in Adélie penguins (Ben-elbaz, Piezzi, and Lynch 1976). In a related species, the gentoopenguin (P. papua), serotinin levels in the pineal gland are high-er at 2400 than at 1200 hours (Gallardo and Piezzi 1973). Morestudies on antarctic penguins are needed to establish withcertainty the effects of the extreme photo-periods on the phys-iological circadian rhythms of these birds.

This work was supported in part by National Science Founda-tion grant DPP 80-19988 and the National Aeronautics and SpaceAdministration's Graduate Student Research Fellowship Pro-gram. Authors Halpryn and Tirrell were in the field duringJanuary and February 1982.

References

Benelbaz, G. A., Piezzi, R. S., and Lynch, H. J. 1976. Hydroxyindole-O-methyltransferase (i-noMT) and melatonin in the pineal gland of theantarctic penguins, Pygoscelis adeliae and P. papua. General and Com-parative Endocrinology, 30, 43-46.

Derksen, D. V. 1977. A quantitative analysis of the incubation behaviorof the Adélie penguin. Auk, 94, 552-566.

Gallardo, M. G. P., and Piezzi, R. S. 1973. Serotonin content in thepineal gland of the antarctic penguin (Pygoscelis papua). General andComparative Endocrinology, 21, 468-471.

Sulzman, F. In press. Microcomputer monitoring of circadian rhythms.Computers in Biology and Medicine.

Winter ecology of Weddell seals atWhite Island

RANDALL DAVIS, MICHAEL CASTELLINI, MARCUS HORNING,

MARIA DAVIS, and GERALD KOOYMAN

Physiological Research LaboratoryScripps Institution of OceanographyUniversity of California-San Diego

La Jolla, California 92093

ROBERT MAUE

Physiology/PharmacologyUniversity of California-San Diego Medical School

La Jolla, California 92093

R. Davis, M. Davis, M Castellini, and M. Horning maintaineda field camp at the northwest end of White Island during the1981 austral winter (February through December). White Island

is located about 25 kilometers southeast of McMurdo Stationand is accessible by tracked vehicle throughout the year. Thepurpose of the study was to obtain information about the divingbehavior of Weddell seals and their winter environment.

The camp consisted of two 5- x 6-meter huts, which servedas living quarters, and a Jamesway garage, which housed thetracked vehicle (a Spryte) and two diesel electric generators(figure 1). An ice hole beneath one of the huts and penetrating 15meters of ice was maintained throughout the winter. It was usedfor oceanographic measurements, biological sampling, and hy-drophone recordings.

At every opportunity the field team made trips along thenorthern shore of White Island to deploy and recover timedepth recorders and depth histogram recorders (Kooyman,Billups, and Farwell in press). The time depth recorders couldrecord information for a 10-day period, and the depth histogramrecorders, for a 25-day period. However, some recorders werenot recovered for up to 7 months.

Five instruments were deployed and recovered during theearly winter (late February to April); total time monitored was67 days. Three mid-winter (June to August) records were ob-tained, covering 40 days. In addition, three records were ob-

1982 REVIEW 183