title: Entrainment of circadian rhythms to irregular light/dark cycles: a subterranean perspective.
abstract: Synchronization of biological rhythms to the 24-hour day/night has long been studied with model organisms, under artificial light/dark cycles in the laboratory. The commonly used rectangular light/dark cycles, comprising hours of continuous light and darkness, may not be representative of the natural light exposure for most species, including humans. Subterranean rodents live in dark underground tunnels and offer a unique opportunity to investigate extreme mechanisms of photic entrainment in the wild. Here, we show automated field recordings of the daily light exposure patterns in a South American subterranean rodent, the tuco-tuco (Ctenomys aff. knighti ). In the laboratory, we exposed tuco-tucos to a simplified version of this natural light exposure pattern, to determine the minimum light timing information that is necessary for synchronization. As predicted from our previous studies using mathematical modeling, the activity rhythm of tuco-tucos synchronized to this mostly simplified light/dark regimen consisting of a single light pulse per day, occurring at randomly scattered times within a day length interval. Our integrated semi-natural, lab and computer simulation findings indicate that photic entrainment of circadian oscillators is robust, even in face of artificially reduced exposure and increased phase instability of the synchronizing stimuli.
authors.affiliation: Institute of Biosciences, Department of Physiology, University of São Paulo; São Paulo, São Paulo, 05508-900; Brazil.
authors.forename: Danilo E F L
authors.initials: DE
authors.lastname: Flôres
authors.affiliation: Institute of Biosciences, Department of Physiology, University of São Paulo; São Paulo, São Paulo, 05508-900; Brazil.
authors.forename: Milene G
authors.initials: MG
authors.lastname: Jannetti
authors.affiliation: Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR), Provincia de La Rioja, UNLaR, SEGEMAR, UNCa, CONICET. Entre Ríos y Mendoza s/n, (5301) Anillaco, La Rioja, Argentina.
authors.forename: Veronica S
authors.initials: VS
authors.lastname: Valentinuzzi
authors.affiliation: Institute of Biosciences, Department of Physiology, University of São Paulo; São Paulo, São Paulo, 05508-900; Brazil.
authors.forename: Gisele A
authors.initials: GA
authors.lastname: Oda
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003624:Darkness; D008027:Light; D012377:Rodentia / Q000502:physiology*; D012621:Seasons