Like all cephalopods, the common octopus is an intelligent active predator (4). They have modified salivary glands that produce venom used to incapacitate prey. It is often easy to identify what a common octopus has been feeding on, as they leave piles of debris known as 'middens' around the entrance of the protective lair in which they live. These middens consist of debris from a range of species and often include mollusc shells and the carapaces of crabs and other crustaceans (5). All cephalopods are good swimmers, and are able to move rapidly by jet propulsion when threatened; water is rapidly expelled through a funnel which causes the octopus to be propelled away rapidly (3). Cephalopods are also able to mask themselves as they escape with a cloud of ink released into the water (2).
I guys, if you want to know more about Octopus and other marine stuff visit my project http://skaphandrus.com/en/marine_species/info/species/Octopus_vulgaris Have a nice day, Hugo Costa, http://skaphandrus.com