By Nancy King
Nancy is a member of the TONMO.com staff -- you can discuss octopuses and more with her in our Cephalopod Care forums.
What is an octopus? It's a sea creature found in all oceans of the world, even in the cold waters of the Arctic and Antarctica. It lives in deep or shallow water and can range in size from very tiny (pygmy octopus) to man-sized (Giant Pacific Octopus). All octopuses have eight muscular but flexible arms ("octo" means eight) with rows of suckers to help them hold their prey or just get around. Octopuses have no bones, so never ask to see the skeleton of an octopus! This enables them to squeeze through very small spaces. The main part of the octopus' body is called the mantle. Its two eyes are located there, and a siphon, which is a tube for expelling water. Underneath, in the center of all the arms, is the beak for killing prey and eating.
Octopuses belong to a group known as Cephalopods; other members of this group are cuttlefish, squid and nautilus - all are types of mollusks, like the familiar snail.
Octopuses live in a variety of conditions in the ocean, from very deep water to coral reefs or even along the shore. Some are adept at leaving the water for a time and hunting along the water's edge, in tide pools. People sometimes think that octopuses can barely move once out of the water. These hunting octopuses travel along very well, collecting good things to eat and stuffing them in their mantle to carry back to their den, where they will have a fine dinner.
Many species of octopus prefer a diet of crustaceans (shrimp, crabs) but also eat fish and some will use their beak to drill open shells such as mollusks. They will even eat other octopuses.
Octopuses have a toxin in their saliva to immobilize their prey. A very few species carry a special toxin powerful enough to kill humans (blue-ringed octopus), but in general octopuses are not a threat to us. In fact, some seem curious about us and can be very friendly. Divers in the Pacific Northwest interact (play) with octopuses frequently.
Octopuses have a remarkable ability to disguise themselves by changing the color and texture of their skin. This helps them remain hidden and is the main method of defense for most octopuses. Octopuses also have a sack of "ink" and can produce a brown or black ink cloud that confuses and irritates their enemy while the octopus escapes in another direction. It uses its siphon to "jet propel" itself away.
Octopuses live anywhere from 6 months (pygmy) to 3-5 years (Giant Pacific Octopus) to possibly a few years longer in colder waters. At the end of her life, the octopus mother lays eggs, which she guards and cares for in her den. She begins to waste away and eventually dies, usually soon after the eggs hatch. There are two types of octopus eggs - some octopuses produce very small eggs, and the hatchlings are tiny and exist as a type of plankton until they eventually grow larger and sink to the ocean bottom to begin their life as octopuses. The larger eggs produce larger hatchlings that look like tiny octopuses.
Octopuses are sometimes kept as pets and are the most successfully kept cephalopod. They need to be kept in a "species tank", a salt-water aquarium devoted to one octopus. Although most of these octopuses are "wild caught", there are people trying (with some success) to breed octopuses to sell as pets. The most popular species seems to be O. bimaculoides, a small California octopus that lives near the shore and is active during the day. Other types of octopuses found in peoples' homes are O. vulgaris, various pygmy species, and the "Bali octopus". Often the pet dealers do not know what species they're selling and may offer them as "brown octopuses", "tropical octopuses," or "transparent octopuses."
--originally published May. 16, 2003
Cephapolod Care book by TONMO.com Staff members Nancy King and Colin Dunlop: