Sleep. A seemingly basic function continues to perplex scientists as they cannot comprehend the reason why organisms would leave themselves completely vulnerable to their surroundings for a considerable amount of the day. However, recent findings surrounding jellyfish suggest that sleep is a function more primitive than previously thought to be.
Researchers conducted an experiment on the Cassiopea jellyfish to show a period of reduced activity in addition to a lower response rate to stimuli. The researchers needed to prove that during a state of quiescence, the jellyfish also had slower reaction times to catalysts in its environment. Such a behavioral pattern would also require a higher urge to sleep the longer the jellyfish was awake. In other words, a longer day would result in more sleep.
As the jellyfish slept, the researchers would attempt to wake the jellyfish by dropping in snacks of shrimp and oyster roe into the tank. When they dropped the food in at night, they found that the jellyfish would awake from its slumber and resume its daytime activities. The researchers additionally discovered that when the jellyfish was forced to stay awake throughout the night, it had a 17% decrease in productivity the next day.
This study proves that sleep is a much older biological function than researchers had previously thought. In the words of Thomas Bosch, an evolutionary biologist in Germany, “the simplicity of these organisms is a door opener to understand why sleep evolved and what it does.” Lastly, if sleep can be traced back to these ancient jellyfish, we are left wondering how old sleep is and how it evolved into what it is now.
Isabella Drzala ’19
Arnold, Carrie. “Jellyfish caught snoozing give clues to origin of sleep.” Nature, 21 Sept. 2017, www.nature.com/news/jellyfish-caught-snoozing-give-clues-to-origin-of-sleep-1.22654.