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Upside-down jellyfish. Credit: Peter Holderness / Caltech

Even jellyfish need their beauty sleep, according to a study conducted at CalTech and published Thursday in Current Biology. Jellyfish don't have brains, just a diffuse webbing of cells called a 'nerve net.' But despite their seemingly simple nervous system, they enter an inactive period each night. And when jellyfish don't catch enough Z's, they lag behind the next day — just like humans do.

Why it matters: It's (essentially) impossible to test if all animals sleep. But if "sleep is conserved from jellyfish all the way to humans, which are almost the furthest evolutionary distance you can go in animals," it would suggest sleep has ancient origins, Claire Bedbrook, one of the authors of the study, tells Axios. Not only does this mean sleep probably only evolved once long ago, it also "really highlights how important sleep is for animals," she adds.

There are three major characteristics that need to be exhibited for something to be defined as sleep:

  • A regularly occurring period of inactivity.
  • During that period, the animal needs to respond slower to a stimulus — sort of like drowsiness when humans first wake up.
  • Finally, the sleep needs to be necessary to the animal's survival.

What they did: The researchers designed a series of experiments to test each of these criteria.

  • Reduced activity: They observed the jellyfish for 6 days, and found that they pulsed 32% more slowly at night.
  • Stimuli response: As their name suggests, upside-down jellyfish spend most of their time upside-down on the sea floor. When the researchers moved them to the top of the tank, they quickly returned to the bottom. But if they were dropped into the column at night, they took longer to re-orient.
  • Skipping sleep: How do you keep a jellyfish awake? Squirt it with water, apparently. The scientists scheduled a pump that sent a pulse of water towards the jellyfish every 20 minutes. After a constant night of harassment, they were 17% less active the next day.

What's next: Jellyfish sleep, but do they dream? What does their sleep look like neurologically? Do the same genes that regulate sleep in humans regulate them in jellyfish? The researchers hope others will look into these questions.

One last thought: When we think about sleep research, we usually think about brain scans and REM cycles. But this study suggests that at its core, a nightly slumber is fundamental and necessary. "If sleep is found in such a simple and basic animal, maybe the function is simple and basic as well," says Michael Abrams, another author on the study. Though of course, he notes, jellyfish aren't actually simple. They've been evolving just as long as humans have.

Go deeper

Kaine, Collins' censure resolution seeks to bar Trump from holding office again

Sen. Tim Kaine (center) and Sen. Susan Collins (right). Photo: Andrew Harnik/Pool via Getty Images

Sens. Tim Kaine (D-Va.) and Susan Collins (R-Maine) are forging ahead with a draft proposal to censure former President Trump, and are considering introducing the resolution on the Senate floor next week.

Why it matters: Senators are looking for a way to condemn Trump on the record as it becomes increasingly unlikely Democrats will obtain the 17 Republican votes needed to gain a conviction, Axios Alayna Treene writes. "I think it’s important for the Senate's leadership to understand that there are alternatives," Kaine told CNN on Wednesday.

Stark reminder for America's corporate leaders

Rosalind "Roz" Brewer is about to become only the second Black woman to permanently lead a Fortune 500 company. She starts as Walgreens CEO on March 15.

Why it matters: It's a stark reminder of how far corporate America's top decision-makers have to go during an unprecedented push by politicians, employees and even a stock exchange to diversify their top ranks.

Ina Fried, author of Login
Updated 4 hours ago - Technology

Apple's quarterly sales top $100 billion for first time

Credit: Apple

Spurred by strong sales of the latest iPhones, Apple reported it took in a record $111 billion in revenue for the three months ended Dec. 31, as the company crushed expectations.

Why it matters: The move showed even a pandemic didn't dull demand for Apple's latest smartphones.

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