Experiment shows that sleeping jellyfish without brain

Sleep works to remove brain wasteResearch results such as reporting that sleep is closely related to rest and recovery of the brain is known from previous studies, while on the other hand "Why do living things need sleep?" Strict reasons are still being studied in 2017. Meanwhile, the graduate students announced the results of the research that "there is a sleep in jellyfish without a brain and the brain is not necessary to sleep."

The Jellyfish Cassiopea Exhibits a Sleep-like State: Current Biology
http://www.cell.com/current-biology/fulltext/S0960-9822(17)31023-0

Brainless jellyfish could reveal why we sleep - The Washington Post
https://www.washingtonpost.com/news/speaking-of-science/wp/2017/09/21/scientists-just-discovered-the-first-animal-without-a-brain-that-sleeps/

Michael Abrams, Claire Bedbrook, and Ravi Nath, who are graduate students of California Institute of Technology, conducted this research. Researching about neurobiology When I was walking while there was Mr. Bedbrook, Abrams and Nath encountered discussing "Jellyfish sleeps", so this research started. Three graduate students did not tell the professor who is a supervisor about what they are doing, they said they were conducting jellyfish experiments in the laboratory at night. "No matter what you think, when starting a funny thing, Abrams says that it is good to take the data first before talking to someone."


"Why do animals sleep?" Is not yet revealed by science. In the case of wild animals, if one is hit by a predator while sleeping it is the end of one volume. There is also the possibility of missing the chance of getting food by sleeping on an empty stomach,Natural selection theoryIn terms of sleep, there is no other advantage than sleeping. However, even though many creatures still need to sleep, sleep is important for living things. If it is unnecessary for an organism to sleep, organisms should have stopped sleeping a long time ago, but in the research done so far, many of the living creatures that were deprived of sleep will die Is shown. And from the results of these experiments, sleep has been considered to have the purpose of resting the brain.

On the other hand, Abrams et al. Chose this experimental subject as an object of experiment, a primitive creature that does not have a brain, but is nervous about the nets of the net. It absorbs food from the holes in the tentacles rather than the mouth and sometimes generates energy by photosynthesis.

Abrams and others confirmed in three experiments whether Sakasakura is sleeping or not.

First, Abrams observed the activity status of jellyfish during daytime and nighttime. We observed 23 jellyfish over 6 days and counted the movements of opening and closing the part of the umbrella, which was 1155 times per 20 minutes in the daytime, 781 times less by 30% at night. On the other hand, even though it was nighttime, when jellyfish was put in jellyfish tanks, the jellyfish became active, and it was concluded that "jellyfish at night is inactive but not paralyzed or coma" It was.


Next, when you carry out experiments to put the removable bottom in the tank and raise or lower the bottom, the jellyfish will swim soon in the daytime and return to the bottom, but in the night it takes about 5 seconds strange shape As I awoke suddenly after drifting in, I started swimming towards the bottom. Furthermore, when I poked jellyfish every 20 minutes at night, I disturbed sleep, as if I was asleep, as if I was drifting under the water in the daytime the next day, so that I could see a deeper sleep on the next night It seems to have become.

After a series of experiments, Abrams et al. Reported the experimental results to Professor Paul Sternberg, a biologist, Professor Sternberg offered a room to continue the experiment. "Jellyfish is a creature we thought of as having a" primitive nervous system "and the results of this experiment are very important," says Professor Sternberg.

Allan Pack, a representative of the Center for Sleep and Circadian Neurobiology at the University of Pennsylvania, says, "Other living things observed so far also showed a state of sleep," and the findings itself Although it is not surprising to clarify the state of sleep of jellyfish, it is important to clarify the state of sleep of "jellyfish" to show "the foundation of sleep", and "the behavior of conservation of physical strength in relatively early creatures in the history of life" It is important to show what it is ". Understanding why a jellyfish that has only a nerve net only needs sleep can lead to elucidation of the function of sleep in humans.