The most obvious difference between most cephalopods and other mollusks is the apparent lack of a shell. Octopuses do not have shells at all, while squids have a small internal shell. read more
Octopuses appear to be aware that they exist. but I don't know if they are aware that they are aware. These animals have a very different brain structure than mammals. Its main part is in the form of a ring around its digestive tract but a good proportion of it is distributed along its tentacles. read more
By the end of its life, an octopus will weigh one-third as much as all the food it has eaten [source: The Economist]. The common octopus only lives an average of three to five years, though, so it doesn't have much time to waste. Once the octopus reaches adulthood, it will eventually get the urge to mate. read more