ANIMALS - Do Octopuses Feel Pain?

The past couple posts have described some pretty severe experiments on octopuses, including: showing how octopus arms can grow back after inflicted damage and how even severed octopus arms can react to stimuli. (For the record, animals in the studies were anesthetized and euthanized, respectively.) Without getting too far into the woods (or reefs) of animal treatment ethics, the question remains: How much pain and distress can these relatively short-lived invertebrates experience?
http://blogs.scientificamerican.com/octopus-chronicles/2013/08/30/do-o