What is the most intelligent invertebrate?

So an oyster may recoil when squirted with lemon juice, for instance, because of nociception.But with such a simple nervous system,it's unlikely to experience
the conscious part of pain.Other invertebrate animals are more complicated, though,like the octopus,which has a sophisticated brain and is thought to be one of the most intelligent invertebrate animals.Yet, in many countries, people continue the practice of eating live octopus.We also boil live crawfish, shrimp, and crabs
even though we don't really know how they're affected either.This poses an ethical problem.