It turns out that octopuses can experience “heartache”

And the fact that these ‘messages’ within the nerve circuits are cancelled by the anaesthetic clearly indicates the animal’s ability to feel the affective component of pain, i.e. excitement, mental pain, in addition to physical pain.

The results of this experiment raise ethical questions about how one should behave when keeping and researching cephalopods. Experts believe that the nervous system of octopuses and other molluscs actually has much greater potential than previously thought.