Daily body temperature rhythm in subterranean rodents (Ctrenomys Knightii)

TACHINARDI PATRICIA SA; ODA GISELI A,; VALENTINUZZI VS; BICUDO JEW

Natal, RN, Brazil

Simposio; X Latin American Symposium on Chronobiology; 2009

Universidade Federal do Rio Grande do Norte-Brasil

Most environments show a clear daily temperature cycle. This poses a particular challenge to homoeothermic animals, which maintain their body temperature within narrow limits independently of the external temperature. It is believed that a considerable part of the rhythmic patterns of thermoregulatory strategies are temporal adaptations to face this situation. Most mammals show clear daily rhythms of heat production and heat loss. The relationship between these rhythms determines phase and amplitude of the animal’s daily core body temperature rhythm, which has been shown to be endogenous, entrained by light/dark cycles and independent of the circadian rest/activity rhythm. The adaptative value of this rhythm is particularly intriguing when it comes to animals that live in environments with relatively constant temperature, such as subterranean mammals. In order to try to elucidate some important issues related to the rhythmicity in such animals, the objective of this project is to investigate whether there is a body temperature rhythm in a South-American subterranean rodent species, and proceed to its characterization comparing rhythm parameters to the ones obtained for other subterranean and non-subterranean rodents. The species to be studied belongs to the genus Ctenomys, the largest genus of non-subterranean rodents in the world, and inhabits the Argentinean province of La Rioja. Previous studies have shown that these animals have a clear rest/activity rhythm, which persisted under constant conditions and were entrainable to light/dark cycles. Although they can be seen during both day and night in the field, they are clearly nocturnal in the laboratory. The animals will be kept individually in cages equipped with running wheels and will have temperature data loggers implanted in the intraperitoneal cavity. The running wheel’s revolutions will be registered to monitor activity. Firstly the animals will be exposed to a light/dark cycle (LD 12:12) to verify the existence of a daily body temperature rhythm. Then the animals will be transferred to constant darkness to verify if the rhythm persists and free-run in such conditions, which would mean it is endogenous. Data will be collected under two different and constant temperatures. The data obtained will be statistically analyzed and compared to the ones obtained for non-subterranean mammals of the same body size, since some characteristics of the body temperature rhythm have been shown to be a function of body size. These experiments are the first step of a future laboratory and field project that will try to clarify aspects of the body temperature rhythmicity in subterranean rodents.