The octopus is a cephalopod of the order Octopoda. The octopus inhabits many diverse regions of the ocean, especially coral reefs. The term may also be used to refer only to those creatures in the genus Octopus. In the larger sense, there are around 300 recognized octopus species, which is over one-third of the total number of known cephalopod species.
An octopus has eight arms, which trail behind it as it swims. Most octopuses have no internal or external skeleton, allowing them to squeeze through tight places. An octopus has a hard beak, with its mouth at the center point of the arms. Octopuses are highly intelligent, probably the most intelligent of all invertebrates. For defense against predators, they hide, flee quickly, expel ink, or use color-changing camouflage. Octopuses are bilaterally symmetrical, like other cephalopods, with two eyes and four pairs of arms. All octopuses are venomous, but only the small blue-ringed octopuses are deadly to humans
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