AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 6 800-R804, Copyright © 1983 by American Physiological Society
Effects of temperature on the circadian rhythm of pig-tailed macaques Macaca nemestrina
H. Tokura and J. Aschoff
Activity rhythms of pig-tailed macaques, Macaca nemestrina, were recorded
under three different conditions: 1) constant illumination (LL) and
constant ambient temperature; 2) light-dark (LD) cycles with 12 h of bright
light and 12 h of dim light (LD 12:12) at constant ambient temperature; 3)
cycles with 12 h of high (32 degrees C) and 12 h of low temperature (17
degrees C) in LL. In constant conditions the period of the free-running
rhythm was positively correlated with light intensity. Ambient temperature
had no systematic effect on the period in LL of 0.45 and 45 lx; when
measured in 100 or 450 lx, the period was consistently longer at 32 than at
17 degrees C. Temperature cycles with a range of 15 degrees C resulted in
entrainment in three adult animals, but not at all tests; two adults and a
couple of young animals were never entrained. Entrainment by temperature
was less accurate than that by LD. The results demonstrate that a
temperature cycle can entrain the circadian activity rhythm of an
homeothermic mammalian species but that it is a very weak zeitgeber
compared with LD cycle.
