DNA damage modulates sleep drive in basal cnidarians with divergent chronotypes

Area of Science:

• * Zoology and Comparative Physiology
• * Evolutionary Biology
• * Neuroscience

Background:

• * Sleep is a fundamental biological process observed across diverse animal taxa, from simple invertebrates to humans.
• * The evolutionary origins and adaptive benefits of sleep in basal animal lineages with simple nervous systems remain poorly understood.
• * Investigating sleep in cnidarians, such as jellyfish and sea anemones, offers insights into the early evolution of this behavior.

Purpose of the Study:

• * To empirically define and characterize sleep in the upside-down jellyfish (Cassiopea andromeda) and the starlet sea anemone (Nematostella vectensis).
• * To explore the environmental and homeostatic factors regulating sleep patterns in these basal invertebrates.
• * To investigate the relationship between sleep, neuronal DNA damage, and genome stability in cnidarians.

Main Methods:

• * Behavioral observation and analysis were used to establish criteria for defining sleep in C. andromeda and N. vectensis.
• * Experiments involved manipulating light cycles, homeostatic pressures, and exposure to mutagens and UV radiation.
• * Neuronal DNA damage and sleep pressure were quantified under various conditions, including sleep deprivation and spontaneous/induced sleep.

Main Results:

• * Sleep in C. andromeda was primarily driven by light and homeostasis, occurring nocturnally and during midday naps.
• * N. vectensis exhibited sleep regulated by both circadian rhythms and homeostatic processes, with increased sleep at dawn.
• * Sleep deprivation, UV radiation, and mutagens elevated neuronal DNA damage and sleep pressure; conversely, sleep promoted genome stability in both species.

Conclusions:

• * Sleep appears to be an ancient, conserved behavior crucial for maintaining genome stability and mitigating cellular stress in simple nervous systems.
• * The findings suggest that the need to repair DNA damage and cope with cellular stress may have been a key driver in the evolution of sleep.
• * Studying sleep in basal invertebrates like cnidarians provides valuable insights into the fundamental functions and evolutionary history of sleep.