Photoperiodic after-effects on Ctenomys aff. knight: activity phase duration (α) and free-running period (τ) following artificial photoperiods

IMPROTA GC; VALENTINUZZI VS; ODA GA

Simposio; XVI Latin American Symposium on Chronobiology-LASC; 2021

Entrainment is achieved by zeitgebers setting period and phase of circadian oscillators. Even after release into constant conditions, endogenous rhythms exhibit long-term effects of the previous entrainment, the so-called after-effects. The photoperiod (ratio between photophase and scotophase) is one of the zeitgeber?s properties retained in after-effects of photic entrainment, causing long-lasting effects in free-running period (τ) and activity duration (α). Our group conducts chronobiological studies on a neotropical species of subterranean rodent, known as Anillaco tuco-tucos (Ctenomys aff. knighti). Despite their subterranean habits, these rodents have demonstrated daily rhythms entrained to LD, both in the field and laboratory. Previous work also indicated seasonality in daily activity rhythms, indicating potential for measuring photoperiod. We asked if photoperiod aftereffects would be displayed by tuco-tucos. Our analysis aimed, specifically, on voluntary running-wheel activity α and τ in animals kept in DD (24 ºC±2, ad libitum food), after being exposed to one artificial photoperiod (long photophase: LD 21:3, LD 18:6 LD 15:9; short photophase: LD 9:15, LD 6:18, LD 3:21; L=1000 lux). Our results indicate that the mean α for short photophase category (13.7±2.1 h) and long photophase category (11.8±1.8 h) differed significantly. τ was about 24h or longer in most individuals, shorter τ occurred only on 15,15% of observations and usually on the long photophase category.