Knowledge from the underground: How subterranean rodents shed light on circadian disruption

FLORES DANILO EFL; VALENTINUZZI VS; ODA GA

Colonia

Simposio; XV Latin American Symposium on Chronobiology-LASC; 2019

Universidad de la Republica-Uruguay

Non-model organisms can bring new insights into biological phenomena. The subterranean rodent tuco-tuco (Ctenomys aff. knighti) from the Monte Desert, Argentina, lives in dark underground tunnels, partially isolated from environmental changes in the aboveground. In view of this peculiar mode of life, we have studied the photic synchronization of tuco-tucos? circadian rhythms. First, we recorded the animals? daily temporal patterns of light exposure in the field. Then, to understand the consequences of the complex light exposure patterns, we employed computer simulations of a model circadian oscillator. The oscillator was subjected to variations of the observed light exposure patterns, consisting of a single 1-hour daily pulse, presented once a day at a random time. Although we were interested in photic entrainment, results revealed an unexpected way to induce circadian disruption. If the single daily pulse is distributed within long time windows (>14 hours), the model predicts two possible outcomes depending on light intensity. Weaker light pulses in these conditions let the oscillator free run with a consolidated rhythm, while stronger light pulses disrupted the structure of the rhythm. In both cases, the stability of the rhythm was broken, as revealed by near-zero serial correlation in day-to-day period values. These light schedules could inspire novel experimental protocols in the research on circadian disruption. For instance, daily pulses at random times could be applied in experiments with in vivo recordings of tissue bioluminescence rhythms, which require little external light. This work illustrates how fresh knowledge can be built from studying non-model organisms. Funding: FAPESP processes 2017/16242-4, 2019/04451-3, 2017/19680-2.