RATE OF METABOLISM IN THE SMALLEST SIMIAN PRIMATE, THE PYGMY MARMOSET(CEBUELLA-PYGMAEA)

Rate of metabolism was measured with six adult pygmy marmosets (Cebuel la pygmaea) at regulated ambient temperatures ranging between 20 degre es C and 35 degrees C. A novel combined nest box and metabolic chamber was designed to allow nighttime measurements on immobile animals in t heir home cage without disturbance. The basal rate of metabolism (BMR) was 98 ml O-2 h(-1), representing 74% of the value expected from the equation of McNab [Quarterly Review of Biology 63:25-54, 1988] relativ e to body mass. The thermoneutral zone was approximately 27-34 degrees C. Below the lower critical temperature (27-28 degrees C), thermal co nductance (12.9 ml O-2 h(-1) degrees C-1) was close to the predicted v alue. Body temperature ranged between 34.9 degrees C and 35.5 degrees C at night. When two animals rested together overnight in the nest box , the lower critical temperature was slightly lowered, and individual energy expenditure at 20-21 degrees C was reduced by about 34%. The ba sal rate of metabolism of C. pygmaea is much lower than reported in an earlier study based on daytime measurements but agrees with values re ported from a more recent study conducted at night with a classical me tabolic chamber. In order to compare the BMR of C. pygmaea with that o f other primates, 23 species were included in a comparative study taki ng into account both phylogeny and body mass (independent contrasts ap proach). The scaling exponent of BMR to body mass obtained was indisti nguishable from that published for eutherian mammals in general. Cebue lla and Callithrix exhibit the lowest basal rates known for simians. T his trait may possibly be linked to the natural diet, which includes a large proportion of gums that are difficult to digest, but additional metabolic studies on primates are needed for further examination of i ts adaptive significance. (C) 1997 Wiley-Liss, Inc.