Jellyfishin'

No Brain? No Blood? No Problem!

Jellyfish. No blood. No brain. No problem! Photo by Jeffrey Hamilton

So, how exactly are jellyfish even alive? They have no brain. No circulatory system. And no heart.

This was a question Little Bean and I struggled to answer the other day all because she squished a tiny ant. And that ant squish came about because she had to do some homework her grandma teacher had given her.

I swear if the two of us were left to our own devices we’d never emerge from the rabbit holes we find ourselves in.

Here’s how it went. She sat down with me at the kitchen table to do some spelling and workbook homework. But there was a tiny ant which she instinctively squished onto her workbook and the squish left a tiny dot of blood.

“Daddy, look, blood! How can something so tiny have blood?”

“All creatures have blood,” I said, but saying that out loud didn’t sound right. She beat me to it.

“What about a jellyfish?” she asked.

“Uh,” I said. I’ve discovered as she gets older I’m saying ‘Uh’ far more often.

We asked Alexa if Jellyfish have blood. Nope. Can’t have blood without a circulatory system. No heart either. No brain.

“How can it be alive without that stuff,” she asked.

“Uh,” I said again.

Turns out jellyfish are alive because the one thing they DO have is complex nervous system. It’s just not centralized like it would be with a brain, so in some ways they have a pretty big advantage over us big brains.

We’ll let an ocean scientist over at PBS explain it.

“Jellies are like the original computer networks, with little servers all along the margin of their body that they use cooperatively,” says Rebecca Helm, a researcher at Woods Hole Oceanographic Institute. “They have a net of cooperative nerve bundles that talk to each other and some pockets of centralized nerves, but no master controller. That’s nice when, say, a sea turtle bites off part of the bell. That isn’t the end of everything, because jellyfish can lose some of those servers.”

Got that?

Anyway, she finished her homework, which mostly had to do with using a list of spelling words in sentences. Jellyfish was not one of those words but I encouraged Little Bean to give her grandma a lesson on the nervous system of the jellyfish next time she sees her. We could all learn a little something!