The Octopus: The word octopus means "eight feet." Octopuses are solitary, eight-armed animals that live on the ocean floor. There are over 100 different species of octopuses. The Giant Octopus is the biggest octopus. This huge mollusk is up to 23 ft (7 m) from arm tip to arm tip, weighing up to 400 pounds (182 kg). The smallest is the Californian octopus, which is only 3/8 inch (1 cm) long.
Anatomy: An octopus has a soft body and eight arms. Each arm has two rows of suction cups. If it loses an arm, it will eventually regrow another arm. It has blue blood. An octopus has an eye on each side of its head and has very good eyesight. An octopus cannot hear.
Diet: Octopuses eat small crabs and scallops, plus some snails, fish, turtles, crustaceans (like shrimp), and other octopuses. They catch prey with their arms, then kill it by biting it with their tough beak, paralyzing the prey with a nerve poison, and softening the flesh. They then suck out the flesh. Octopuses hunt mostly at night. Only the Australian Blue-ringed octopus has a poison strong enough to kill a person.
Protection: Octopuses live in dens, spaces under rocks, crevices on the sea floor, or holes they dig under large rocks. Octopuses pile rocks to block the front of their den. The den protects them from predators (like moray eels) and provides a place to lay eggs and care for them (a mother octopus doesn't eat during the entire 1 to 2 months she is caring for her eggs). In order to escape predators, octopuses can squirt black ink into the water, allowing the octopus to escape. Another defense that octopuses have is changing their skin color to blend into the background, camouflaging themselves. The octopus swims by spewing water from its body, a type of jet propulsion.