Jellyfish sleep about as much as humans do – and nap like us too

Jellyfish exhibit sleep-like behavior, with patterns resembling those of humans. Researchers from Bar-Ilan University in Israel have studied the sleep patterns of jellyfish to shed light on the evolution of sleep in marine organisms.

Unlike mammals, jellyfish belong to a group of brainless animals called cnidarians. Understanding their sleep patterns can provide insights into why sleep first evolved in these creatures with simple neural networks.

The study focused on Cassiopea andromeda, an upside-down jellyfish species. Observations revealed that these jellyfish exhibit periods of activity during the day and reduced activity at night, indicating a sleep-like state. They sleep for about 8 hours a day, with a short nap in the afternoon.

Disrupting the jellyfish’s sleep by pulsing water at them resulted in increased sleep duration the following day, similar to how sleep-deprived humans compensate for lost sleep. The researchers also found that DNA damage accumulates in jellyfish neurons while they are awake, but sleep appears to reduce this damage, suggesting a neuroprotective role of sleep.

Further experiments on the starlet sea anemone (Nematostella vectensis) showed similar sleep patterns, indicating that sea anemones also exhibit sleep-like behavior. This study provides valuable insights into the sleep patterns of marine organisms and the potential benefits of sleep in maintaining neural health.

Overall, the research highlights the importance of studying sleep in a wide range of organisms to unravel the mysteries of sleep evolution and its biological significance across different species.