Members of the Class Cephalopoda within the Phyla Mollusca, about 300 species of octopus are found in Temperate and Tropical seas across the globe. Having first evolved during the Carboniferous Period (some 300 million years ago), they now inhabit a wide range of ocean habitats, favoring coral reefs and rocky areas near islands, shelfs or seamounts.
While some grow to 5 feet in length and weigh up to 25 pounds, most species are much smaller; on the other hand, the Giant Pacific octopus may reach 30 feet in length and weigh up to 600 pounds. All feed primarily on a host of marine crustaceans and mollusks and evade predation themselves by the use of camouflage, by swiftly retreating to a protective crevice within rock or coral and by releasing a cloud of ink that temporarily blinds and confuses the predator; should one of its eight arms be snared by an enemy, the octopus is able to regrow another. Venomous saliva, employed to stun prey, is seldom used for self-protection; however, the bite of the blue-ringed octopus, a small Australian species, can be fatal to humans.
Though most species of octopus live for less than two years (males die after spawning and females after protecting her eggs until they hatch), they are known to be relatively intelligent creatures, capable of using crude tools and demonstrating the ability to learn and memorize behaviors that enhance their survival.