Circadian Pattern of Wheel‐Running Activity of a South American Subterranean Rodent (Ctenomys cf knightii)

Abstract

Circadian rhythms are regarded as essentially ubiquitous features of animal behavior and are thought to confer important adaptive advantages. However, although circadian systems of rodents have been among the most extensively studied, most comparative biology is restricted to a few related species. In this study, the circadian organization of locomotor activity was studied in the subterranean, solitary north Argentinean rodent, Ctenomys knightii. The genus, Ctenomys, commonly known as Tuco-tucos, comprises more than 50 known species over a range that extends from 12 degrees S latitude into Patagonia, and includes at least one social species. The genus, therefore, is ideal for comparative and ecological studies of circadian rhythms. Ctenomys knightii is the first of these to be studied for its circadian behavior. All animals were wild caught but adapted quickly to laboratory conditions, with clear and precise activity-rest rhythms in a light-dark (LD) cycle and strongly nocturnal wheel running behavior. In constant dark (DD), the rhythm expression persisted with free-running periods always longer than 24 h. Upon reinstatement of the LD cycle, rhythms resynchronized rapidly with large phase advances in 7/8 animals. In constant light (LL), six animals had free-running periods shorter than in DD, and 4/8 showed evidence of "splitting." We conclude that under laboratory conditions, in wheel-running cages, this species shows a clear nocturnal rhythmic organization controlled by an endogenous circadian oscillator that is entrained to 24 h LD cycles, predominantly by light-induced advances, and shows the same interindividual variable responses to constant light as reported in other non-subterranean species. These data are the first step toward understanding the chronobiology of the largest genus of subterranean rodents.

Life in a dark biosphere: a review of circadian physiology in “arrhythmic” environments

“…One such animal is the South American solitary burrowing rodent, Ctenomys knightii , commonly known as the Tuco-tuco. These rodents show circadian rhythms of activity both in laboratory conditions (Valentinuzzi et al 2009) and when brought into the lab directly from the field (Tomotani et al 2012), again demonstrating the presence of a circadian system in a subterranean animal. However, even pulses of light can entrain circadian clocks (Carr and Whitmore 2005), and light-sampling behaviour, even to less than 3.5 % of the total light period, is a sufficient entraining signal for nocturnal rodents (Decoursey 1986; Decoursey and Menon 1991).…”

Sincronização fótica e não fótica dos ritmos circadianos em roedores subterrâneos (Ctenomys aff. knighti) e roedores modelo de laboratório (Mus musculus)

“…Freshly captured animals express rhythms in constant conditions, with periods very close to 24 hours, which strongly indicate aftereffects of a previous entrainment (Tomotani et al, 2012). We have also confirmed that the tuco-tucos' circadian rhythms can be synchronized in the laboratory by artificial light/dark cycles, via entrainment of a circadian oscillator (Valentinuzzi et al, 2009). However, the participation of light information for entrainment in the field remained to be confirmed.…”

“…Our initial laboratory studies with this tuco-tuco species revealed marked daily rhythms of activity in the running wheel (Figure 1.2), with wheel revolutions concentrated in the dark phase (Valentinuzzi et al, 2009). The rhythm persisted in constant lighting conditions and was synchronized to artificial daily light/dark cycles.…”

“…From day 5 onwards, the animal was kept in constant darkness and the activity-rest rhythm persisted, suggesting that the rhythm was generated by an endogenous clock. Modified from (Valentinuzzi et al, 2009). …”

Ritmos circadianos em Gracilaria birdiae (Rhodophyta): oscilação do desempenho fotossintético e caracterização enzimática da nitrato redutase

“…Não somente em organismos fotossintetizantes, mas para qualquer modelo tal conceito é essencial, um exemplo são as análises do comportamento de camundongos em rodas de exercício que registram ao longo de meses a frequência da atividade dos animais submetidos a diversas condições. (CASIRAGHI et al, 2012;VALENTINUZZI et al, 2009), utilizando o menor esforço possível do observador.…”