I'm not sure about squid, octpi and cuttlefish but I learned recently that jellyfish have no brain.

 

Quote

https://oceanconservancy.org/blog/2023/08/03/do-jellyfish-have-brains/

Instead of a brain, a sea jelly has a set of nerves commonly referred to as a nerve net or nerve ring. This nerve net helps them detect shifts in their environment, including temperature, gravity, water salinity, oxygen concentration, vibrations and currents

 

On 10/13/2023 at 1:14 PM, studiot said:

I'm not sure about squid, octpi and cuttlefish but I learned recently that jellyfish have no brain.

 

 

Squid have brains as do cuttlefish but an octopus has nine brains. 

That’s fairly awesome. And here I only have two