Enelgy Metabolism, Nocturnal Torpor, and Respiration. Frequency in a Green Hermit (Phaethornis guy). KarI-L. Schuchmann and Roland Prinzinger. Torpor ...
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Psychol. 88: 1-20. • GATES,G. R., D. R. PERRY& R. B. COLES(1975): Cochlear microphonics in the adult domestic fowl (Gallus dornesticus). Comp. Biochem. Physiol. 51A: 251--252. • GOERDEL-LEtcH,A., & J. SCHWARTZKOPFF(1984): The auditory threshold of the pigeon (Columba livia) by heartrate conditioning. Naturwiss. 71: 98--99. • Hou, S. M., M. A. BOONE& J. T. LONG, (1973): An electrophysiological study on the hearing and vocalization in Gallus dornesticus. Poultry Sci. 52: 159--164. • SACHS,M. B., J. M. SINNOTT& R. D. HIENZ (1978): Behavioural and physiological studies of hearing in birds. Fed. Proc. 37: 2329--2334. • SAUNDEI,,S,J. C., G. R. GATES& R. B. COLES(1974): Brain-stem evoked responses as an index of hearing thresholds in one-day-old chicks and ducklings. J. Comp. Physiol. 86: 426-431. Anschrift der Verfasser: Lehrstuhl fiir Allgemeine Zoologie und Neurobiologie, Ruhr-Universit,it, Postfach 10 21 48, 4630 Bochum 1.
j. Orn. 129, 198&S. 469-472 Enelgy Metabolism, Nocturnal Torpor, and Respiration Frequency in a Green Hermit (Phaethornis guy) KarI-L. Schuchmann and Roland Prinzinger Torpor, a regulated reduction of body temperature (Tb) and energy metabolism (M), has been documented for various hummingbird taxa, both in their native habitat (FRENCH& HO1)GES 1959, CARPENTER1974, 1976) and under laboratory conditions (LAsIEwSKI1963, LASIEWSKIet al. 1967, HAINSWORTH& WOLF 1972, HAINSWORTHet al. 1977, WITHERS1977, KR(~GERet al. 1982, SCHUCHMANNet al. 1983, PRINZINGERet al. 1986). Until now, torpor in hummingbirds has only been documented for members of the subfamily Trochilinae Here we report on metabolism, torpor and respiration frequency (F) in a Green Hermit (Phaethornis guy), a member of the subfamily Phaethornithinae M a t e r i a l and M e t h o d s Green Hermits ( ~ = 5.30 + 0.2 g, n = 3) were collected in Ecuador (upper Rio Napo region), transported to Frankfurt, FRG, by air, and kept in our laboratory in a large aviary (2.0x3.0x2.5 m) at a mean ambient temperature (T~) of 22°C with a light-dark cycle of 12 : 12 h (light phase from 07.00 to 19.00). Two individuals died during their annual molt, leaving only one to be tested. This male molted in captivity and was in good health condition during the experiments. It was kept in a plexiglas chamber (29x23 x 13 cm, volume 8.7 1). The flow rate (open system) was 30 1 h -1, STPD. The metabolic rate (M, J g-I h-i) was calculated from 1 ml 02 = 20 J (based on the observed mean respiration quotient). We used a HARTMANN& BRAUNCaldos 4T CO2 analyzer (accuracy +5 %) and a HARTMANN& BRAUNMagnos 2T oxygen analyzer (accuracy +2 %). F was recorded constantly at a Ta of 20 °C with a highsensitivity pressure transducer (0--35 mbar, BELL& HOWELLmodel L 4104) inserted in the
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[ J' Orn. L 129 respiration chamber. This permitted calculation of tidal volume, assuming a constant O2 extraction of 5 % and an air-oxygen concentration of 21%. Food (artificial nectar produced by Biotropic, Baden-Baden, FRG) was available ad libitum in the metabolism chamber. TI, was not recorded since the hermit was very sensitive to any kind of handling (for further details see Kt~OGERet al. 1982). After a two-day acclimatization period at 25 °C in the metabolism chamber, the hermit was exposed to sequential 24 h temperature regimes of 15 o, 20 °, 25 o, 28 o and 35°C. Results was somewhat lower than predicted values of hummingbirds based on the correlations M (kJ h -1) = 0.708xW (g)0.54 for day-time levels (T~: 25°C) and M = 0.212xW °76 for nighttime levels including torpor (Fig. 1; cf. PRINZINGEt~et al. 1981).
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Fig. 1. Diurnal cycles of energy metabolism in a Green Hermit at various ambient temperatures (Ta). The black bar represents the inactive period (night). The tested individual died when exposed to a T~ of 35°C for 20 hours (symbol). When the light was switched off (19.00), M reached values suggesting torpor (below 50 J
g-I h-i) within an hour, and torpor was confirmed by visual observation. The lowest M (9 j g-1 h-i) ~5 % mean day-time levels) was recorded three hours after the beginning of the nocturnal resting phase at a T~ of 15 °C. Except at a Ta of 35 °C, torpor was maintained for approximately eight hours (Fig. 1). About three hours before light, M increased to a mean of 60 J g-1 h-i, and about one hour before light, M increased to about 190 J g-1 h - i M in torpor showed a linear relationship to Ta (M = --27.2 + 2.2 T~, r = 0.92, Fig. 2). During the photophase, F was 2.33 + 0.18 s -1 (total measurements n = 105), and at night (non-torpid) 0.6 + 0.2 s -1 (1 night, n = 15) at a T~ of 20°C. Mean 02 consumption per
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Fig. 2. Energy metabolism (M) in torpor as a function of ambient temperature (Ta) for a Green Hermit. Torpor metabolism values are means _+SD at each Ta tested. At the usual daily Ta in the hermit's habitat (27°C), the bird's energy savings in torpor compared to normal M are up to 60 %, i. ~, torpor M is 40 % of mean day-time M.
breath was 8.2 ~tl (tidal volume 163 ~l) during the active period and 4.9 ~tl (tidal volume 98 ~tl) during the inactive period. The W at 15 °, 20 °, 25 °, and 28°C was 5.3 _+ 0.2 g. At a Ta of 35 °C a loss of W of 0.4 g (7. 5 %) was observed. Discussion As shown for various members of the subfamily Trochilinae, M is regulated at different levels correlated with Ta, and torpor occurs for about 70 % of the dark period (Ki~OGE~et al. 1982). It has been suggested that torpor in hummingbirds only occurs at low energy reserves (HArNswORTHet al. 1977), but KROGEt~et al. (1982) found that torpor occurs regularly and not only with energy deficiencies. The absence of torpor observed in some hummingbirds (HAINSWORTHet al. 1977) may be explained by seasonal demands (~ g., moult, migration). The tropical environment of the Green Hermit provides a relatively high, stable Ta (27 °C + 3). Thus, the greatest savings of overnight energy expenditure would approximate 60 % without increased M in torpor. However, as demonstrated by PRINZINC~Ret al. (1986), hummingbirds increase M in torpor below a Ta of 15 °C (not tested for the Green Hermit). Thus, it still has to be proven that hermits have regulatory patterns similar to non-hermits. Respiratory frequency and tidal volume of the Green Hermit are in concordance with previous findings in trochilids (PRINZINGER• SCHUCHMANN1985, PRINZINGER~X~JACKEL1986). The respiration and energy metabolism data reported here for the Green Hermit suggest an absence of marked differences in these parameters between the subfamilies Phaethornithinae and Trochilinae.
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This researchwas supported by a DFG grant (Pr 202/2-2). The paper benefitedgreatly from comments by L. BAPTISTA,A. BRICE, F. R. HAINSWORTH,E. KIETZMANN,D. POWERS,and W. W. WEATHERS.
Zusammenfassung Beim Griinen Schattenkolibri (Phaethornis guy) lag die Relation zwischen Energiestoffwechsel (M) und Umgebungstemperatur (Ta) geringfiigig unter den nach der K6rpermasse (W) zu erwartenden Werten. Am Tage (Ta: 25°C) betrug die Korrelation M (kJ h -1 ) = 0,708xW (g)0,s4, nachts (einschliefflich der Torporwerte) M = 0,212xW °'76. Tiefster Torporwert war 9 J g-1 h-1 (nachts, 15°C). M im Torpor verlief linear zur Umgebungstemperatur (M = --27,2 + 2,2 Ta, r = 0,92), Die Atemfrequenz in der Photophase betrug 2,33 +_ 0,18 s -1 (n = 105), nachts (Torpor unberiicksichtigt) 0,6 + 0,2 s-1 (n = 15). Die Oz-Aufnahme pro Atemzug betrug 8,2 ~tl in der aktiven und 4,9 ~tl in der inaktiven Phase Die Mef~werte zeigen, dalg Phaethornis guy, ein Vertreter der Unterfamilie Phaethornithinae, sich in Energiestoffwechsel, Torpor und Atemfrequenz von den bisher untersuchten Trochilinae nicht unterscheidet. Literature CARPENTER, E L. (1974): Torpor in an Andean hummingbird. Its ecological significance. Science 183: 545--547. • CARPENTER,E L. (1976): Ecology and evolution of an An&an hummingbird (Oreotrochilus estella). Univ. Calif. Publ. Zool., 106. • FRENCH,N. R., & R. W. HODGES(1959): Torpidity in cave-roosting hummingbirds. Condor 61: 223. • HAINSWORTH, E R., & L. L. WOLF (1970): Regulation of oxygen consumption and body temperature during torpor in a hummingbird Eulampis jugularis. Science 168: 368--369. • HAINSWORTH,E R., B. G. COLLINS& L. L. WOLF(1977): The function of torpor in hummingbirds. Physiol. Zool. 50: 215-222. • KROGER, K., R. PRINZINGER& K.-L. SCHUCHMANN (1982): Torpor and metabolism in hummingbirds. Comp. Biochem. Physiol. 73A: 679--689. • LASIEWSKI,R. C. (1963): Oxygen consumption of torpid, resting, active and flying hummingbirds. Physiol. Zool. 36: 122-140. • LASlEWSKI,R. C., W. W. WEATHERS& M. H. BERNSTEIN(1967): Physiological responses of the Giant Hummingbird, Patagona gigas. Comp. Biochem. Physiol. 23A: 797--813. • PRINZINGER~ R.~ K. KROGER& K.-L. SCHUCHMANN (1981): Metabolism-weight relationship in 17 hummingbird species at different temperatures during day and night. Experientia 37: 1307--1308. • PRINZINGER,R., & K.-L. SCHUCHMANN (1985): Respiration frequency and tidal volume in resting hummingbirds during daytime J. Orn. 126: 107-108. • PRINZ1NGER~R.~ & S. JACKEL(1986): Energy metabolism, respiration frequency and 02 consumption per breathing act in 11 different sunbird species during day and night. Experientia 42: 1002--1003. • PRINZINGER,R., I. LOBBEN& S. JACKEL(1986): Vergleichende Untersuchungen zum Energiestoffwechsel bei Kolibris und Nektarv6geln. J. Orn. 127: 303-313. • SCHUCHMANN~K.-L., K. KROGER& R. PRINZINGER(1983): Torpor in hummingbirds. Bonn. zool. Beitr. 34: 273--277. • WITHERS, W. (1977): Respiration, metabolism and heat exchange of euthermic and torpid poorwills and hummingbirds. PhysioL Rev. 57: 43--52. • WOLF, L. L., & E R. HAINSWORTH(1972): Environmental influence on regulated body temperature in torpid hummingbirds. Comp. Biochem. Physiol. 41A: 167-- 173. Authors' addresses: (K.-L. S.), Zoologisches Forschungsinstitut und Museum A. Koenig, Adenauerallee 150--164, D-5300 Bonn 1; (R. P.), Zoologisches Institut der Universit~it, AG Stoffwechselphysiologie, Siesmayerstr. 70, D-6000 Frankfurt/M. 1.
