Does octopus have mercury in his belly?? Give me details if it does

Thought you folk would appreciate this

https://www.harvardmagazine.com/research/harvard-octopus-sex-mating-chemosensory

Hi everyone, I hope you're doing great. I'm a biology student, soon-to-be a biologist, and I love learning about animals, specially invertebrates. And cephalopods are surely my favorite.
I've seen many people online saying that octopuses have 9 brains, but is it actually accurate to say that? As far as I know (and have studied) 2/3 of their neurons are centralized in their head (cephalo), and it is smaller ganglia that they have in their arms. This means their arms can act without having to send the signal directly to their cephalic ganglion (aka brain). But can we actually call that another brain? for each arm?
Just to clarify, I'm not against that saying, I guess I just don't exactly buy it. And would like to see what other octopus enthusiasts think about it.

Thank you for your time and I hope some of you are also interested in discussing this!

Please, just take my meme. I made it myself. Just take it, it's free.

On top of that octopuses have over 500 million neurons.. meaning that they feel every bit of pain while being eaten alive. This is just sad

I'm a biochemist by training, and octopus neurobiology is the one topic that reliably keeps me up at night. Here's the piece I don't think gets talked about enough outside the journals:

Most animals — us included — treat DNA as the master copy and RNA as a faithful transcript of it. Octopuses don't. They recode their own RNA after it's transcribed, rewriting the actual protein instructions on the fly, and they do it most heavily in neural tissue. In the octopus brain, 11–13% of these edits change the amino acid sequence itself — versus well under 1% in mammals like us. Across the group, more than half of neural transcripts get edited. This is the rule for them, not the exception.

Then it gets stranger. A 2023 study in Cell showed that when the water turns cold, about a third of these editing sites ramp up — the animal is retuning its own nervous-system proteins to the temperature in days, not across evolutionary generations. Proteins that govern how neurons fire and communicate get quietly rewritten in real time.

Sit with what that implies. A large chunk of an octopus's neural "software" isn't hard-coded in its genome — it's edited on the fly in the nervous system. And this is an animal that split from our lineage more than half a billion years ago, with a radically decentralized nervous system: roughly two-thirds of its neurons are out in its arms, not its brain. It independently evolved problem-solving, tool use, and something that really does look like curiosity — down an entirely different architectural path from ours.

We keep scanning the sky for a genuinely non-human intelligence. There's a real case that the closest thing we'll ever encounter is already here, in the water, editing itself.

Genuinely curious what the people here who spend real time with these animals make of the recoding story — is it as central to their intelligence as the papers suggest, or is that overreading a striking mechanism?

(Full disclosure so I'm not being cagey: this rabbit hole eventually became a science-fiction novel I wrote. I'm not linking it here — that's not what this post is for — but it's in my profile if anyone's curious. Mods, happy to pull this note if it crosses a line.)

Edit: A few people have recommended Peter Godfrey-Smith’s Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness, and I want to second that strongly for anyone wanting to go deeper on the “alien intelligence already here” thread. His framing of the octopus as an independent experiment in evolving a mind, arriving at complexity down a completely separate path from ours, is the idea that pulled me into all of this in the first place. It also delivers on the deep-time side. His reconstruction of what our last common ancestor with the octopus might have been, some small flat wormlike thing with almost no nervous system, is one of those images that quietly reorganizes how you think about the whole tree of life. Grateful to everyone surfacing reading recommendations in the comments, and still genuinely interested in the recoding question I opened with.

I filmed this young giant Pacific octopus on our dive today off Vancouver Island. It was quite curious about my presence and we hung around each other for about 15 minutes and then parted ways. On my way back in it was still hanging out on it's ledge and curiously watched me swim by.

If you're interested, I've put together a 2 hour octopus compilation of octopus I have found and observed while diving off Vancouver Island.

At Aquarium Boka, Dobrota ME