Long-term exposure to extreme illumination regimes alters behavioral responses to light in the cockroach, Periplaneta americana L.

The natural lighting conditions vary depending on latitude, niche, and time of day, and animals are evolutionarily adapted to them. Artificial lighting, along with global warming, drives population ranges toward high latitudes, which creates fast-changing environments for the biota. The American cockroach Periplaneta americana L. is a synanthropic species with a nocturnal lifestyle, rarely exposed to light. Three-month-long exposure to constant light or constant darkness compared to the control 12:12 h day and night cycle, causes behavioral changes explained by two main factors: adaptation of the visual system and circadian rhythm disruption. State of complete immobility, an indicator of the inactive phase of a 24 h rhythm, appeared in groups kept under constant light regimes and tested in the dark, as well as in those subjected to experimental lighting with low-intensity green light. Exposure to such light caused different behavioral changes in groups kept under different light regimes, reflecting the cockroaches' internal levels of arousal, stress, and light adaptation of their photoreceptor organs. Thus, altered lighting conditions impose significant challenges on different aspects of insect physiology and behavior.