The daily lives of dogs are deeply intertwined with human routines, often exposing them to lighting environments that differ from natural daylight cycles. In a recent study published in Chronobiology International, Giannetto and colleagues (2024) examined how circadian clock genes behave in dogs under normal daylight (NDL) and constant light (LL) conditions.
Five female Beagles were monitored under both conditions, with blood samples collected every four hours across a 24-hour cycle. Analysis focused on the expression of key circadian genes, including Clock, Per1–3, and Cry1–2. Under normal daylight, all genes exhibited robust daily rhythmicity. However, under constant light, most rhythms were disrupted—yet crucially, Clock gene expression persisted, peaking near sunrise.
This persistence of Clock activity under constant light suggests that dogs possess an endogenously generated circadian signal that allows partial maintenance of rhythm despite environmental disruption. Such findings are considered preliminary but important, as they demonstrate that peripheral blood sampling can provide valuable insights into canine circadian adaptation without invasive methods.
The research underscores the potential influence of human lifestyles—such as artificial lighting and altered sleep schedules—on dogs’ biological rhythms. Understanding how these internal clocks function could help optimize canine welfare, especially in households where natural light exposure is limited.
Source: Giannetto, C., Arfuso, F., Rizzo, M., Giudice, E., Calapai, F., Guercio, A., Macaluso, G., Giacchino, I., Piccione, G., & Cannella, V. (2024). Persistence of clock gene expression in peripheral blood in dogs maintained under different photoperiod schedules. Chronobiology International, 41, 369–377. Published February 7, 2024.
