They discover an animal without a brain that, despite it, sleeps

It is necessary to have a head for many things, but not to rest properly. The living proof is Cassiopea, an inverted jellyfish who, despite not having a central nervous system like fish, mice and humans, is capable of getting a little head.

"It's the first time it's been proven that an animal with no sesera sleeps," said Paul Sternberg, a researcher at the Caltech Institute in California and co-author of the discovery of Cassiopea, an inverted jellyfish with this surprising ability - is understood, but the one of making it lacking of brain.

This is not a trivial find. Scientists have spent years debating whether animals sleep to consolidate memory, to allow cells to recover from waking rest or for some other reason that we have not yet elucidated. But there was another more basic question still in the air that Cassiopeia has brought to the surface: do all animals sleep? The vertebrates, yes. Different thing is the invertebrates.

Some of them, like the fruit fly, have found evidence that they do indeed rest. Jellyfish and sponges, with a fairly rustic primary nervous system, were in doubt. Until now.

The thing took a turn when a student from Sternberg's laboratory named Ravi Nath set out to clear the unknowns. Neither short nor lazy, he spoke with Lea Goentoro to film the tanks he has in his laboratory with dozens of these jellyfish of tropical origin for six days and six consecutive nights. And he found that the pulses of contraction-relaxation of his gelatinous bodies were different during the night and during the day. At night, the activity was reduced: from 58 beats per minute to 39. Everything was pointing to that they slept.

But Nath did not settle for that. To eliminate any chink of doubt, he set in motion an original experiment. He introduced a platform into the tank to climb to the jellyfish, which usually rest on the ocean floor. And he observed their reaction to eliminate the platform and leave them in what they interpret as 'open sea'.

If they do this day's work, they quickly swim until they recover their position in the bottom. At night they also react like this, but three times slower, as if they were groguis, something typical of an animal that sleeps.

The third test was even harder: they tried what would happen if they were 'bothered' during the night constantly. And they observed that the next day they were less active: they showed all the signs of having spent a sleepless night.

If there were doubts about what was before, whether the brain or the dream, with this study have been cleared. On the evolutionary tree, rest clearly appeared before the nervous system had a full-fledged 'control center'. However, there are still important issues to be resolved. For example, do neurons need sleep? What's more, do you need more than one cell? Do protozoa and bacteria sleep? And the plants? The questions remain, for the moment, on the table.