Effects of long scotophase and cold acclimation on heat production in two diurnal rodents

Heat production {Mathematical expression} of two diurnal rodents, Rhabdomys pumilio and Lemniscomys griselda was measured in long scotophase-LS (8L: 16D; 25°C) acclimated and long scotophase and cold - LSAC (8L: 16D; 6°C) acclimated animals and compared to a control group (12L: 12D; 25°C). LS increased {Mathematical expression} in both species. Further acclimation of LSAC increased {Mathematical expression} in R. pumilio and decreased {Mathematical expression} in L. griselda. LS increased body temperature (Tb) in L. griselda only. LS increased overall thermal conductance in both species. LSAC caused a further increase in this parameter in R. pumilio. A singificant (P<0.001) increase in the magnitude of maximal nonshivering thermogenesis (NST) was observed in both species due to LS acclimation. LSAC did not change this maximal NST but increased its obligatory part (minimal {Mathematical expression}, P<0.05, in L. griselda, and P<0.001, in R. pumilio). The results of this study show that winter acclimatization of heat production mechanisms, in both species, may be due to extension of scotophase. © 1982 Springer-Verlag.