I've posted news stories in the past about octopuses opening jars in one form or another. Here's a story from Feb. 8th about a recent experiment that observes an octopus discerning between jars with food and empty jars. The article is found on Ananova:
http://www.ananova.com/news/story/sm_748630.html
http://www.ananova.com/news/story/sm_748630.html