THE JOURNAL OF EXPERIMENTAL ZOOLOGY 261~331-339(1992)

Secondary Sex Characteristics and Related Physiological Values in Male Fallow Deer (Dama dama L.) and Their Relationships to Changes in the Annual Cycle of Daylengths: Frequency Alterations to 4- and 3-Month Photoperiodic Cycles, and Subsequent Re-SynchronisationUnder Natural Conditions H. SCHNARE I . Zoological Institute, Georg-August-University Gottingen, D -3400 Gottingen, Germany ABSTRACT

Five adult male fallow deer were maintained in a barn with artificial light control. In a previous experiment, three 6-month photoperiodic cycles entrained morphogenetic and associated physiological values that revealed typical relationships to the antler cycle. Presented here, the light cycle was accelerated to three 4- and one 3-month photoperiods in the same group. Each artificial photoperiod generally resulted not only in a n almost complete antler cycle but also in a n entire cycle of seasonal fluctuations in neck girth. Increases in plasma levels of alkaline phosphatase (AP), total-, LDL- and HDL-cholesterol, were generally entrained and the maxima revealed positive correlations with antler formation, but the relationships slightly diverged. In neck girth and creatinine, positive correlations to the hard antler period as well as to each other prevailed but diverged. In the 3-month photoperiodic cycle, these relationships were out of synchrony. In the second 4-month cycle, two bucks “missed” shedding and subsequent casting, but commenced antler growth in the following cycle with a n in-time shedding. The possibility of desynchronisation of physiological conditions and the question of a n endogenous circannual mechanism interacting with daylight are discussed. At the end of the 3-month cycle, experimental indoor and natural outdoor casting was coincident so the group was transferred to outside conditions for re-synchronisation. After spending altogether 36 months in frequency altered photoperiods, the represented values were neither synchronized nor revealed their typical relationships to the antler cycle, except of AP and neck volume. In the second cycle of re-synchronisation, all parameters, except of creatinine, appeared to be resynchronized.

It is well known that adult male Cervinae living in temperate and arctic climates exhibit a pronounced annual cycle of secondary sex characteristics such as t h e antler and neck cycle, which depend on annual changes of androgen levels (Lincoln, ’71).This periodicity and its annual recurrence are affected by seasonal fluctuations of day length (Jaszewski, ’54;GOSS, ’69, ’83;Schnare, ’86),called the annual cycle of daylengths or photoperiod. For adult male fallow deer living in optimal social relationships within the herd, the individual timing of single phases in the antler cycle, such as like casting, antler formation, shedding, and the period of hard antlers-as well as the onset of neck muscle hypertrophy can be very precisely predicted 0 1992 WILEY-LISS, INC.

(Fischer, ’85). The fertile period is almost consistent with the hard antler period, and the androgendependent neck muscle hypertrophy coincides with the r u t (Schnare and Fischer, ’87a,b). Our previous research on male fallow deer investigating secondary sex characteristics as well as several connected blood parameters, such as the activity of alkaline phosphatase (AP), total-cholesterol (TC), low- and high-density lipoprotein cholesterol (LDLC

Received July 17,1990; revision accepted July 2,1991. Address reprint requests to Dr. Harald Schnare, Trappenhardt 8, D3546 Voehl, Germany.

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and HDL-C), and creatinine, demonstrated an annual periodicity under natural conditions (Eiben and Fischer, '83; Fischer and Schnare, '86) and even under experimental 6-month photoperiodic cycles (Schnare and Fischer, '87a,b). The time course maxima of AP, TC, LDL-C, and HDL-C were distinctly related to the period of antler growth, whereas the maxima of creatinine as well as of the neck cycle were related to the period of hard antlers. The purpose of this subsequent study was to examine whether threefold followedby fourfold accelerations of the annual cycle of daylengths will influence the annual periodicity of morphogenetic parameters and related physiological values in the same group of male fallow deer previously investigated under 6-month photoperiodic cycles by Schnare and Fischer ('87a). For the first time, a group of adult large mammals were subjected over a period of years without interruption to various experimentally accelerated photoperiods in an artificial environment, after which they were resynchronized under natural conditions.

MATERIAL AND METHODS Our previously reported investigation started in May 1984 when five male fallow deer were close t o casting their first antlers. These bucks, living under three experimental 6-month photoperiodic cycles, were confined in a lighttight barn. Detailed informations are given by Schnare and Fischer ('87a) and Schnare ('90a).

In the present study, the same deer were followed through different experimental photoperiods beginning in late December 1985.Threefold acceleration of the annual cycle of daylengths was achieved by omitting every other 2 days on the digital timer so that the full cycle of daylength changes elapsed within 4 months instead of 12; consequently, the artificial year lasted 122 instead of 366 days of the leap-year 1984. The 3-month cycle was achieved by omitting every other 3 days, so that the experimental cycle lasted 91.5 days. Neck girth was measured twice, around the larynx and 10 cm caudad, and neck volume was calculated from the formula of a truncated cone. Mean values and correlation analysis were calculated from four bucks of identical age (born 1982)and one buck, born in 1983, except in neck parameters, where the younger one had to be excluded because of age-dependence. In Table 1correlation analyses are listed, and they are demonstrated in Figure 5. Data obtained during the antler growth period and the period of hard antlers were pooled and Student's t-test for unpaired data was employed for testing the differencebetween the two groups. P-values less than 0.01 were considered as significant. At the end of June 1986, the digital timer was out of order for one or two Sundays so the bucks have had a longer daily light period at least once. A contingent influence of this irregularity is not discussed here, because the parameters subse-

TABLE 1. Correlation coefficients(rj o f blood values and neck girth in male fallow deer ( n = 5j maintained on three 6-month, three 4-month, one 3-month, and two 12-month photoperiodic cycles. &month'

Values' AP/TC APJLDL-C AP/HDL-C TC/LDL-C TC/HDL-C LDL-C/HDL-C Crea/NG APJCrea AP/NG TC/NG TCiCrea LDL-C/Crea LDL-C/NG HDL-CJCrea HDL-C/NG

3 cycles r (n) 0.76 (30) 0.57 (30) 0.77 (30) 0.91 (30) 0.82 (30) 0.68 (30) 0.74 (19) - 0.56 (30) -0.79 (19) -0.78 (19) - 0.43 (30) - 0.32 (30) - 0.69 (19) -0.31 (30) -0.67 (19)

4-month photoperiodic cycles 3 cycles r (n) 0.68 (26) 0.24 (26) 0.65 (26) 0.61 (26) 0.79 (26) 0.25 (26) 0.72 (26) 0.25 (26) - 0.37 (26) - 0.57 (26) - 0.43 (26) 0.04 (26) - 0.15 (26) - 0.56 (26) - 0.76 (26)

3-month 1cycle r (n)

0.24 (7) - 0.54 (7) - 0.38 (7)

0.87 (7) 0.67 (7) 0.42 (7) - 0.25 (7) 0.67 (7) 0.28 (7) - 0.88 (7) 0.11 (7) 0.08 (7) - 0.91 (7) - 0.48 (7) - 0.50 (7)

re-synchronisation cycle 8 r (n)

cycle 9 r (n)

0.77 (13) 0.68 (13) 0.33 (13) 0.80 (13) 0.75 (13) 0.38 (13) - 0.03 (13) -0.07 (13) - 0.68 (13) - 0.56 (13) -0.31 (13) -0.10 (13) - 0.17 (13) - 0.40 (13) - 0.49 (13)

0.7303) 0.96(8) 0.54(8) 0.57(8) 0.92(8) 0.35 (8) - 0.61 (8) 0.24(8) - 0.23(8) - 0.51 (8)

0.25(8) 0.20(8) - 0.13 (8) -0.03(8) - 0.48(8)

'Schnare and Fischer, '87a. 'AP activity of alkaline phosphatase, TC: total-cholesterol, LDLC and HDL-C: low- and high density lipoprotein cholesterol, Crea; creatinine, NG: neck girth.

FREQUENCY ALTERATIONS IN PHOTOPERIODIC CYCLES IN MALE FALLOW DEER

quently did not show any immediate alteration; antler formation was in progress, and, moreover, this incident happened with increasing day lengths.

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Secondary sex characteristics Antler cycle and neck muscle hypertrophy Figure 1 presents the seven cycles of frequency accelerated photoperiods as well as the two cycles of re-synchronisation and indicates the overall ranges of antler formation in days (C) corresponding to the outside photoperiodic conditions (A). In (B) the time courses of seasonal neck muscle hypertrophy in four bucks of identical age is compared with a n individual one year younger, and it is obvious t h a t in each cycle t h e younger buck never reached the value of the older ones. Each artificial photoperiod resulted in a complete antler cycle from casting to casting and consequently accelerated the seasonal, androgen-dependent neck volume hypertrophy with its typical positive relationship to the hard antler period. However, with one exception in cycle 5 , where two bucks “missed” the expected dates of shedding and subsequent casting. But along with the others, both, now called “runaways,”were synchronized again at the expected dates of shedding in cycle 6. This incidence did not affect the neck cycle.

In the 36 months of experimental examination, three 6-month, three 4-month, and one 3-month photoperiodic cycles were simulated. These seven abbreviated “years” are called cycles 1to 7. Cycles 1to 3 are reported previously (Schnare and Fischer, ’87a). In the present study, cycles 4 to 9 are represented. Cycles 4,5, and 6 are 4-month photoperiodic cycles; cycle 7 is one 3-month “photoperiod.” At the end of the 3-month cycle, both experimental indoor and normal outdoor casting was coincident (compare A-C in Fig. 1).However, casting in the experimental deer had shifted almost 50%from the normal schedule during increasing to decreasing daylengths. Therefore, the opportunity presented itself to transfer the group from experimental to natural outdoor photoperiodic conditions. The objective was to explore if and to what extent adult male fallow deer are able to synchronize their life rhythm after they had spent almost 3 years in several different frequency altered photoperiods. The imme- A P and antler formation diately following 20 months of re-synchronisation The AP activity exhibited a distinct “annual” periodicity related to each artificial photoperiodic cycle are demonstrated, too (cycles 8 and 9).

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Fig. 1. Antler formation in fallow deer (n = 4). A. Corresponding natural photoperiodic conditions. B. Seasonal neck muscle hypertrophy (neck volume) in four bucks of identical age compared with an individual one year younger (-). C. Main-

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tained on three 6-month (Schnare and Fischer, ’87a), three 4-month, one 3-month photoperiodic cycles, and after transfer to outside natural conditions (re-synchronisation). h: hours of daylight (52”N.lat.).

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5 came up to a mean antler weight of 1820 2 339 g in cycle 6. There was no correlation among the rates of antler growth and artificial photoperiods. JFMAMJJASONOJFMAMJJASONOJFMAMJJASONO

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TC, LDL-C, and HDL-C In the foregoing 6-month photoperiodic cycles, all three values exhibited a distinct “annual” periodicity and a significant increase during the antler growth period; their maxima revealed a positive correlation with antler formation as well as between themselves (Schnare and Fischer, ’87a). Now, in 4and 3-month photoperiodic cycles, these relationships diverge, but positive correlations in these three values are still in existence (Table 1;see Fig. 5 ) and the maxima revealed partial relationships with antler formation as well as between themselves (Fig. 3C,D,E). In cycle 4 the increase during antler formation was significant in TC and LDL-C but not

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Fig. 2. Antler formation in fallow deer (n = 5 ) .A. Corresponding natural conditions (“runaways”(n = 2). B. Maintained on three 4-month and one 3-month photoperiodic cycles, and after transfer to outside natural conditions (cycles 8 and 9). C. Activity of alkaline phosphatase (AP: mean i SD). D. Antler weight (mean ? SD). h: hours of daylight.

and a significant increase in levels during the antler growth period (Fig. 2C). In cycle 5 , the AP level decreased in both “runaways” 3 weeks after the expected date of shedding and increased again in cycle 6 while the “normal” three bucks grew their new sets of antlers. Both were synchronized again along with the others while shedding in cycle 6. After conversion to the outside photoperiod, the increase in AP was significant during antler formation in both cycles of re-synchronisation. Overall duration of antler formation (compare Fig. 1C) with mean antler weight (Fig. 2D) lasted 71 days with 459 t 91 g, respectively, in cycle 4 (growth rate 6,5 g/d), 67 days with 617 & 177 g in cycle 5 (9,2 g/d), 61 days with 713 & 237 g i n cycle 6 (11,7 g/d), and 66 days with 565 ? 145 g in cycle 7 (8,6 gld); the following two periods of antler formation under natural conditions lasted 139 and 133 days. The two bucks that “missed” shedding and casting in cycle

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Fig. 3. Antler formation in fallow deer (n = 5). A. Corresponding natural conditions (‘‘runaways”). B. Maintained on three 4-month and one 3-month photoperiodic cycles, and after transfer to outside natural conditions (cycles 8 and 9). C. Totalcholesterol (TC). D. LDL-cholesterol (LDL-C). E. HDL-cholesterol (HDL-C) (mean 2 SD). h: hours of daylight.

FREQUENCY ALTERATIONS IN PHOTOPERIODIC CYCLES IN MALE FALLOW DEER

in HDL-C; in cycle 5 the increase was not significant in any of them; in cycle 6 the increase was significant in TC and HDL-C, but not in LDL-C; and in cycle 7 the increase was not significant in any of these values. In the first cycle of re-synchronisation (cycle 81, all values were neither synchronized with each other nor did they reveal their typical relationships to the period of antler formation at all. In cycle 9 these parameters were synchronizedagain. In cycle 5 the levels of these values decreased in both “runaways” 3 weeks after the expected date of shedding and increased again in cycle 6 while the “normal” three bucks grew their new antlers. Both “runaways” were synchronized again while shedding in cycle 6.

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Neck girth and creatinine In the foregoing 6-month photoperiodic cycles, these parameters exhibited a distinct “annual”periodicity and a significant increase during the hard antler period. Both revealed positive correlations with each other (Schnare and Fischer, ’87a). In 4-month photoperiodic cycles, the positive correlation in both parameters was still in existance (Table 1; see Fig. 51, and the maxima revealed a partial correlation to the hard antler period (Fig. 4C,D). However, only in cycles 4 and 6 was the difference between antler formation and hard antlers significant in neck girth; creatinine was significant only in cycle 6. In cycle 7 there was only a slight increase in neck girth during the hard antler period, whereas the time course of creatinine was out of all proportion with no positive correlation to neck girth and with a contrary significant increase during antler formation. After transfer to the outside natural photoperiod, both parameters were neither synchronized with each other nor did creatinine reveal the typical relationship to the period of hard antlers in cycle 8 and 9. In cycle 8 neck girth increased to a normal and expected level after minor fluctuations during the period in velvet and was fully resynchronized in cycle 9. In neck volume (Fig. lB), the younger individual revealed a similar time course like the older ones, but on a lower level.

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Fig. 4. Antler formation in fallow deer (n = 5). A. Corresponding natural conditions; individual one year younger. B. Maintained on three 4-month and one 3-month photoperiodic cycles, and after transfer to outside natural conditions (cycles 8 and 9).C. Creatinine (n = 5). D. Neck girth (n = 4) (mean t_ SD). h: hours of daylight.

Ceruidae are primarily responsible for annual fluctuations in plasma AP-activity (Graham et al., ’62; Drescher-Kaden,’74;Morris and Bubenik, ’83;Chao et al., ’84; Eiben et al., ’84; Sempere et al., ’86). In male fallow deer a close relationship between AP activity and antler formation in 6-month photoperiodic cycles was reported by Schnare and Fischer (’87a),which was very similar to observations under natural conditions (Eiben and Fischer, ’83). The onset of antler growth varied with the frequency of the photoperiod rhythm, an observation that is similar to results from photoperiodicmanipulations DISCUSSION in sika deer (Ceruus nippon) reported by Goss (’69). Considering that AP is the main enyzme of osteo- Although 6-month, 4-month, and 3-month photoblasts and that AP activity reflects bone growth and periodic cycles generally entrained the seasonal bone rebuilding, respectively, the increasing activ- cycles of morphogenetic and related physiological ity was not unexpected in frequency accelerated pho- parameters as well as the testicular cycle (Gosch toperiods. Previously it could be demonstrated by and Fischer, ,891, the changes tended to occur later several authors that growing antlers in adult male than normal with a relatively constant phase shift-

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Fig. 5. Correlation coefficients (r)of blood values and neck girth in male fallow deer maintained on three 6-month (f = 2/a, Schnare and Fischer, ’87a), three 4-month (f = 3/a), and one 3-month (f = 4/a) photoperiodic cycles, and after conversion to natural conditions (f = l/a: re-synchronisation, cycles and 9); f = cycles per year (a). For abbreviations, see Table 1.

ing similar to observations reported by Goss (’69) and Pollock (’75). The onset of antler formation followed this shifting from normally increasing to decreasing day lengths subsequent to the summer solstice. In cycles 1to 3 (the previous 6-month photoperiodic cycles), the end of antler formation with rubbing off of the velvet occurred with decreasingdaylengthsjust prior to the winter solstice, but in cycles 5 to 7 (the currently reported 4-and 3-monthphotoperiodic cycles), shedding occurred with increasing daylengths. Normally, shedding occurs with decreasing daylength just ahead of the autumnal equinox (Chapman and Chapman, ’75, Schnare, ’86). It is apparent, however, that the interval after the vernal equinox in normal and accelerated cycles last about 6 weeks before the actual onset of antler growth took place. The constancy of this lag shifted the period of antler formation to increas-

ingly later phases of the light cycle when photoperiods were accelerated more and more, until it occupied almost the opposite portion of the light course. In the 3-month photoperiodic cycle, antler growth did not begin until it would have ended under natural conditions. Similar observationsare reported by Goss (’69).Corresponding to that, the problematic nature of phase angle shifting and biorhythmics concerning photoperiodic manipulations in deer is discussed by Schnare (’90a).This shifting entrained the AP activity, which consequently was confined by casting and shedding in each cycle of our photoperiodic manipulations, with one exception: in cycle 5 , two bucks “missed” the expected date of shedding, did not cast their antlers in accord with the others, and were not synchronized before shedding in cycle 6. What might prevent these “runaways” from in-time shedding? Casting and shedding are controlled by decreasing and increasing activity of the reproductive system, whereas photoperiodicity regulates different stages of the testicular cycle. Normally, increasing testosterone levels are found during the time of shedding (Fischer and Rolf, ’87), which determine the onset and maintenance of hard antlers as well as neck muscle hypertrophy as secondary sex characteristics (Lincoln, ’71; Lincoln et al., ’72;Lund-Larsen, ’77).In cycle 5 , by taking the measurement of the neck circumference,a decrease was found instead of an expected increase at this time. Neck girths in both “runaways” slightly decreased to a minimum, in the course of which all five bucks were synchronized again. The probability is that the androgen level did not come up to a certain threshold to induce an in-time shedding. Different thresholds of target organs for androgens were postulated by Lincoln (’71). It is remarkable that castrated bucks do not rub velvet and that indicates the necessity of androgens in this progress. However, the cause of rubbing behavior is not yet known, but based on current knowledge (Bubenik, ’831, it might be hypothesized that rubbing off of the velvet is induced by stimulation of CNS centres by androgens or androgen metabolites, which in boreal Cervidae rapidly rise at the end of summer. In cycle 5, shedding occurred at the end of “winter” instead of “summer,”so one might hypothesize that the endogenous rhythm and exogenous Zeitgeber should have come into conflict with each other. It was hypothesized (Eiben and Fischer, ’84; Fischer and Schnare, ’86) that in adult male Cervidae a great amount of cholesterol is required during antler formation, which provides the cell

FREQUENCY ALTERATIONS IN PHOTOPERIODIC CYCLES IN MALE FALLOW DEER

building material for antler production. The authors reported a distinct annual periodicity in plasma levels of TC, LDL-C, and HDL-C with obvious positive relationships to the antler formation. Although 6-month photoperiodic cycles produced a corresponding frequency acceleration of these values, the changes tended to occur about 1month later than normal, similar to observations in secondary sex characteristics, antler formation, and A P activity. In 4-month photoperiodic cycles, this relatively constant shift was still in existence, although progressive, which even now generally illustrated the close relationship to antler formation. In the 3-month cycle and in the first cycle of re-synchronisation, these values were neither synchronized with each other nor did they reveal their typical relations to the period of antler production. There was already a tendency in the 4-month cycles, but positive correlations and significances commenced to diverge. Morris and Bubenik (’83)hypothesized that photoperiodic cues, possibly along with hormonal and neural factors, may influence plasma cholesterol levels. They also discussed the influence of feeding patterns. Although fallow deer in captivity generally retain their normal cycles with regard to feed intake and body weight, even in accelerated “years” when fed ad libitum, we must keep in mind that in herbivorous mammals, e.g., Ceruidae, almost exclusively endogenously synthesized cholesterol is available (Noble, ’81). It is rather possible that androgen factors influence plasma cholesterol levels. In cycle 5 , when the two bucks “missed” the expected date of shedding, the levels of TC and its carrier proteins LDL and HDL still were significantly higher 3 weeks subsequent to the actual date of shedding, then significantly decreased to a minimum, and increased again in cycle 6 to significantly higher values while the “normal” three bucks grew their new sets of antlers. What happened t o the physiology when these “runaways” did not rub off the velvet? We do not know, but it is remarkable that the time courses of both “runaways” generally were similar to the others but on a significantly higher level. We must bear in mind that the velvet was not shed and that there was no rubbing behavior at all. As mentioned above, there is much to be said for a certain unattained androgen threshold, below which shedding is impossible. We tended t o refer to these “runaways” as “physiologicalcastrates.” In fact, the outward appearance of the antlers showed some distinctive signs of a hypogonadic animal (Taylor et al., ’641,e.g., the velvet dried almost completely but was not shed,

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and the antlers remained unpolished. Moreover,they commenced to grow in cycle 6. Besides, we noticed rather atypical bony appositions (“nodes”)on the surface of the antlers in both “runaways” after shedding, and the testicular cycle was obviously abnormal (Gosch, pers. comm.). These antlers were not comparable to the peruke antlers of the roe deer (Capreolus capreolus) (Bubenik, A., ’66; Bubenik and Weber-Schilling, ’86). Since the “runaways” resumed antler growth despite their dried velvet at the end of cycle 5 , judging by appearances, the new skin was formed mainly at the antler tips, which was responsible for a linear expansion of the antlers in cycle 6. Lincoln (’71)included the neck muscles of male Ceruidae among the secondary sex organs, because of their susceptibility to changes in plasma testosterone levels, which initiate and maintain neck muscle hypertrophy as long as present (Lincoln et al., ’72). Castrated red deer (Ceruus elaphus) had neck circumferences similar t o those of intact animals during the sexual quiescant period (Lincoln, ’71). In adult male fallow deer, a marked increase in neck volume during the sexually active period is followed by a slow decrease after the rut, consistent with the long-lasting period of fertility, to a minimum during antler formation (Schnare and Fischer, ’37b). In Figure 6 the time courses of neck volume in juvenile and adult fallow deer under natural photoperiods are compared. Hence it appears that neck volume increases during the first 20 months of life and that there is no positive correlation to the formation of the first antlers, called spikes. While growing the second set of antlers, a significant decrease in neck volume is followed by a marked increase to the rut and a maximum during the period of hard antlers similar to the commencement of the first postnatal testicular activity (Fig. 6A). Figure 6 (B) demonstrates neck cycles of three individual adult bucks at different stages of life over 3 years. This shows the age-dependenceof neck muscle hypertrophy and illustrates the positive relationship between rut and maximum neck volume. It is obvious that there is a nexus between testicular activity (rut) and neck muscle hypertrophy. Creatinine, a substance known to be derived from muscles, revealed a positive correlation to seasonal variations in neck muscle volume, even in 6-month photoperiodic cycles (Schnare and Fischer, ’87a). Both parameters exhibited a distinct “annua1”periodicity and a significant increase during hard antler periods. In 4-month photoperiodic cycles, this positive correlation was still in existence, but the tendency

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What might happen after conversion to the outside photoperiod? It is conceivable that by distorting the environment to such extremes as represented, the internal physiology was thrown in such disorder that it was nearly impossible for the individual t o re-synchronize again shortly afterward. Possibly, the endogenous rhythm and the exogenous Zeitgeber were still in conflict. Yet if there is an endogenous annual rhythm photoperiodically entrained by the yearly light cycle as the driving oscillation, it would seem to be remarkably flexible. At least the morphogenetic secondary sex characteristics are evidently able to adapt to fluctuations in the driving oscillation to a minimum of about 25% of the length of natural 12-month photoperiod. This is similar to observations reported by Goss ('69) in sika deer. In conclusion, the photoperiod is responsible for the annual fluctuations in the testicular cycle, and by influencing its activity along with hormonal and neural factors, the photoperiod indirectly controls the secondary sex characteristics as well. Finally, the development of the skull, the antler buds, and the roses as well as the outward appearance demonstrated an earlier maturity under accelerated photoperiodic cycles compared to normal conditions. The apparent discrepancy between the calendar and biological ages of the experimental deer is discussed by Schnare ('gob).

ACKNOWLEDGMENTS

This study is part of a doctoral thesis at the I. Zoological Institute, Georg-August-University emerged that the relationships might diverge. In Goettingen. The author thanks the University of the 3-month cycle, there was only a slight increase Goettingen administration for preparing the stall. in neck muscle hypertrophy during the hard ant- I gratefully acknowledge the Niedersaechsisches ler period, whereas the time course of creatinine Ministerium fuer Ernaehrung, Landwirtschaft und was out of all proportion with a contrary signifi- Forsten, Hannover (grant No. 113/477301)as well cant increase during antler formation. After the con- as the Niedersaechsische Jaegerschaft for financial version to the outside natural photoperiod, both support. I am deeply obliged to the Land Niedparameters were neither synchronized nor did they ersachsen for granting a scholarship in frame of reveal the typical relationships to the hard antler NiedersaechsischesGraduiertenfoerderungsgesetz. period; however, neck volume increased during ant- I also thank foreign correspondence clerk Aline Schnare for reading the manuscript. ler formation. As already noted, there is much to be said for a LITERATURE CITED possible internal desynchronisationof testicular facBubenik, A.B. (1966) Das Geweih. Parey, Hamburg. tors. Obviously, the androgen-dependent secondary Bubenik, A.B., and C. Weber-Shilling (1986) Die Periicke der sex characteristics as well as the androgen-influGeweihtrager und das Phanomen des Abwerfens oberhalb der enced physiological values become increasingly Rose. Z. Jagdwiss., 32:158-171. desynchronized when artificial photoperiods are Bubenik, G.A. (1983) The endocrine regulation of the antler cycle. In Antler Development in Cervidae. R.D. Brown, ed. accelerated more and more. Nevertheless, it is Caesar Kleberg Wildlife Research Institute. Kingsville, TX, remarkable that from the outward appearance the pp. 73-107. antler cycle, like the neck cycle, were almost Chapman, D.I., and N.G. Chapman (1975) Fallow Deer. Terence Dalton, Lavenham, Suffolk. entrained by each accelerated light cycle.

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