Synchronization of subterranean rodent’s activity rhythm by light/dark cycles: lunar modulation

- TOMOTANI BM; VALENTINUZZI VS; ODA GA

Natal, RN, Brazil

Simposio; X Latin American Symposium on Chronobiology; 2009

Universidade Federal do Rio Grande do Norte-Brasil

Organisms express endogenous rhythms that confer physiological and behavioral anticipation for the challenges presented by a cyclic environment. For the efficiency of this temporal adaptation, the organism´s biological oscillators must be synchronized to the environmental cycles, allowing the events to happen  at  the most appropriate time of day. The laboratory verification of a Phase Response Curve is important to understand how these cycles are able to synchronize the rythms. Additionally, field studies combined with  laboratory studies are essential in order to better understand these processes. Subterranean rodents are interesting biological systems for  synchronization studies, for they are less exposed to light/dark cycles (the main Zeitgeber for most organisms). The subterranean rodent Ctenomys knighti, currently being studied in laboratory, will also be studied in its natural habitat. The purpose  is to determine, if and how, the activity/rest rythm is synchronized by light/dark cycles in the laboratory and natural conditions, and, additionally, if  lunar cycles modulate the rhythmic expression of this species. The experiments will be conducted at  the Centro Regional de Investigaciones Científicas y Transferência Tecnológica (CRILAR - CONICET) in Anillaco, La Rioja, Argentina. In  laboratory, the Phase Response Curve  will be obtained by giving 15 minutes light pulses (200 lux) in 16 animals in constant dark  at 8 different phases. We have preliminary data that suggest   that  C. knightii may have a PRC with phase delays, phase advances or no phase shift depending on the phase the pulse was given. These data suggest  that the light/dark cycle is, in fact, a Zeitgeber for these animals. In the field, in a 10.000m2 study area animals living in their burrow systems will be captured,, receive actigraphs with light detectors and liberated immediately in their burrows. Temporal profiles of exposure to light as well as the activity/rest rhythm will be detected and stored continuously by the device during intervals of 15 to 20 days. This information, together with the Phase Response Curve, will be used to better understand if and how synchronization by light/dark cycles occurs in this specie. Some studies report that nocturnal rodents are less active in full-moon nights compared to new-moon nights. In this sense, the field information obtained here will be used also to investigate if the lunar cycle modulate the rhythmicity of these subterranean rodents. This will be done comparing the light exposure and above-ground ativity in different moon phases.