Longitudinal Study of the Annual Variation of Daily Wheel-Running Activity and Body Temperature Rhythms in Subterranean Rodents (Ctenomys sp.), under Controlled Laboratory Conditions.

• Grant number: 22/04032-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2022
• End date: May 31, 2023
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Gisele Akemi Oda
• Grantee: André Luciano Giovanni Giraud Gil Conti Chiara
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Annual biological rhythms are in general synchronized by the annual variation of photoperiod (daily ratio between the length of day and night). Little is known about the existence of annual rhythmicity and synchronization mechanisms in organisms that live in extreme photic environments such as caves, underground tunnels and abyssal regions. It is possible that, for these organisms, other factors such as seasonal variation in environmental temperature and food availability may play more central roles in synchronization. Recently, our group has verified seasonal variation of the daily activity patterns of the tuco-tuco, a subterranean rodent endemic to South America (Ctenomys aff. knighti), in semi-natural enclosures. Under these conditions, the duration of individual recordings was limited to one or two months per individual, and cross-sectional sampling was necessary to assess the rhythmic patterns that covered the seasons. In the last five years, we have continuously recorded the locomotor wheel-running activity and body temperature (Tb) of tuco-tucos kept in the laboratory under annual photoperiod variation perceived by the natural light/dark cycle through the window, while maintaining a temperature of 22oC and ad libitum food. The objective of this project is to analyze the rhythmic parameters of longitudinal series of individuals recorded continuously for 2 to 3 years, as well as the body mass, to verify the hypothesis that there will be annual variation of the following parameters: beginning and duration of daily activity, maximum, minimum and average values, as well as amplitude of the daily rhythm of Tb and that the annual photoperiod variation is sufficient for synchronization while the other factors remain constant. In addition, an analysis will be made of the inter-individual variation of these parameters and of the differences between males and females, taking into account the annual variation of the levels of reproductive hormones that are being analyzed in a parallel project.