An octopus, also called a cephalopod, is an invertebrate creature with eight tentacles. On each of these tentacles are suction cups that the octopus uses for gripping its prey and to move. The animal comes in a variety of sizes; like most marine animals, children enjoy learning about the octopus.
An octopus is considered a mollusk and has a soft body with no bones. It has two eyes, one on each side of the bag-shaped head. While the eyesight of the octopus is good, it cannot hear. An octopus also has three hearts. One heart pumps blood through the body while the other two pump the blood through the gills. The only hard part of an octopus is a parrot-shaped beak it uses for eating. Most octopuses are about 4.3 feet long and weigh as much as 22 pounds. The Pacific Octopus is the largest species and can grow more than 16 feet long.
The octopus is native to bodies of salt water. Though they can be found in any ocean, those that live in warm water are generally smaller, while those in cold water grow to a larger size. They typically gather around rocky environments such as coasts with a lot of stone or coral reefs, and like to live in holes or the crevices that form in rocks. Some species even build an area around their den for protection.
Like most ocean creatures, the octopus feeds on what is around it, such as shellfish, crayfish, mollusks and crab. They catch the food with their tentacles, and insert their beak into the shell. A poison found in octopus saliva is injected into the shellfish, and the octopus sucks out the flesh using the beak. It hunts mostly at night, and also uses ink to disorient its prey before it attacks.
An octopus uses a variety of methods to defend itself against predators. It can bend its body to squeeze through and hide under rocks, blend into the natural environment, swim away or use ink to dull a predator's senses so it can get away. The ink substance can also blind a predator temporarily, which makes it a good protective mechanism. If a predator catches an octopus, cutting off one of the tentacles, the tentacle can grow back eventually. Some of its enemies are sharks, morays and conger eels.