Jellyfish can sleep without brain

Scientists reveal Jellyfish can sleep without brain

Jellyfish has been construed to be one of Earth’s first and most primitive animal and latest study on the activities of these ancient animals reveal that even they need sleep that too without a brain. Sleep is a complex activity that includes REM (Rapid Eye Movement) which is the time when we dream. Performing this action without a brain is something that seemed impossible up until now.

According to a demonstration held by scientists on Thursday, a primitive type of jellyfish called Cassiopea goes to sleep every night. Apart from this, sleep has been confirmed in other invertebrates such as worms and fruit flies. The Jellyfish is the most evolutionarily primitive ancient animal that is subjected to sleep at night.

Ravi Nath, a biologist from the California Institute of Technology, explained, sleep is one of the most ancient behaviors amidst animal kingdom which is deeply rooted within their lineage. The results of the study suggest that even those animals which lack a centralized nervous system require sleep for sustaining life.

When we take a look at the origin of Jellyfish, it has swum the oceans of Earth for at least 600 million years now. Upon comparison, Dinosaurs appeared roughly 230 million years ago, and humans started walking the Earth only 300,000 years ago. It makes the Jellyfish such a primitive creature which raises hundreds of questions about the origin of sleep and its purpose.

The study was published in the journal Current Biology and was lead by Nath who further stated that it is not yet known to us whether sleep is just limited to animals or goes deep into the microbial community.

Sleep is a task which is genetically encoded into our behavior. Genes and neural circuits interact to generate the state of sleep. It can be hard to demonstrate the sleep behavior in the microbial community, but it is highly possible that the sleep state we know of may have been co-opted from the period of passiveness in organisms as diverse as plants, bacteria, and fungi.

Although they lack brain, spine or central nervous system, Jellyfish are among the first animals to have developed neurons/ nerve cells. Cassiopeia thrives in the bright, shallow, tropical waters of the Pacific and Western Atlantic oceans. They survive by eating plankton and measure about 1-2 inches (2.5-5 cm) in diameter. They have been named the upside-down jellyfish as they lie on the sea floor in an inverted position inside the water with their tentacles facing upward.

The results of this study have been concluded in the Jellyfish via three important sleep criteria which are, periods of decreased activity which is called behavioral quiescence, a reduced response to external stimuli and an increased sleep drive after being sleep deprived. The study did not include whether the Jellyfish are subjected to dreaming or not.

Last year, NASA scientists have taken a breathtaking image of jellyfish-shaped Nebula using Chandra X-ray Observatory In the image we can clearly see a gigantic yellow coloured jellyfish floating in the dark sky along with millions of twinkling stars.