Daily rhythm of metabolic rate in the tuco-tuco (Ctenomys aff. knighti), a subterranean rodent

TACHINARDI P; TØIEN O; BUCK LC; ODA GA; VALENTINUZZI VS

Mendoza

Congreso; XII Latin American Symposium on Chronobiology-LASC; 2013

Tuco-tucos (Ctenomys aff. knighti) are subterranean rodents which occur in Northwest Argentina. They are nocturnal in the lab, showing daily activity and body temperature (Tb) rhythms. However, in the field they are observed aboveground during the daylight hours on a daily basis. It has been suggested that this switch in phase of activity  between field and lab might be related to differences in energy requirements of these two conditions. To approach this hypothesis, we began to study the energetics of C. aff. knighti by characterizing their daily metabolic rate (MR) rhythm in the lab. We measured O2 consumption (using flow-through respirometry), Tb and motor activity in 4 adults housed individually. Animals were fed ad lib and kept under LD12:12 (L=200 lux) and at 23±1oC. In the 3 days prior to respirometry measures we kept animals in unsealed cages with running wheels. In the following 3 days we placed them in sealed respirometry chambers without wheels. Then we inserted wheels in the sealed chambers for 3 days. Finally, animals were removed from the respirometry chambers and Tb and activity were recorded for 2 more days. MR range was 0.63-2.09 mLO2 g-1 h-1 1 in a 140g-individual and 0.34-2.79 mLO2 g-1 h-1 in a 200g-animal. The other animals displayed MR within these ranges. Surprisingly, 3 tuco-tucos changed their previous nocturnal pattern when placed in the respirometry chamber. One became diurnal while 2 became crepuscular. These animals also did not run on the wheel.  Interestingly, the only individual which ran on the wheel remained nocturnal. MR followed the same rhythmic pattern as activity and Tb in all animals. Further studies will be conducted to investigate the variability in rhythmic patterns upon housing in the respirometry chamber.