Octopus

A bottom-dwelling animal, the octopus makes its home in a hole or rock crevice in shallow water. Sometimes it digs a gravel nest or forms a protective area with a pile of rocks. By day, the octopus spends most of its time hidden in its lair. When it hunts, if propels itself by swimming or crawling along on its tentacles. Its large, lidded eyes are adapted to focus in dim underwater light.

The octopus does most of its hunting at night. It emerges from it rocky lair to seek crabs, crayfish, and mollusks, which are its favorite foods. The octopus catches most of its prey by stealth. Having changed color to blend in with its surroundings, the well-camouflaged octopus waits for prey to pass by and then seizes it with its long arms. The arms are powerful and flexible, with two rows of suckers that help it grip its slippery prey. The octopus then stuns its victim with a secretion of nerve poison. To stalk lobsters and other dangerous prey, the octopus squirts ink into the water to form a screen. Hiding behind the dark cloud, it creeps up on its victim and grabs it from behind. If the octopus's prey is hard-shelled, the octopus punctures the shell by drilling with its tongue, which is covered in small, sharp teeth.

The octopus's predators include moray and conger eels, dolphins, and sharks. Whenever possible, the octopus will escape from its predators by shooting a jet of water through its body to create a burst of speed. Often, however, the octopus avoids detection completely. It can change its body color and texture so perfectly that it can virtually disappear. The colored pigment in its skin can be concentrated or diluted, forming stripes and patterns that blend into the environment. The octopus's ink sac also helps it avoid attack. It releases a disorienting black cloud that is accompanied by another secretion to dull the attacker's sense of smell.

When octopuses mate, the male sends waves of spermatophores down one of its arms---the hectocotylus---into the female to fertilize her eggs. For about a week afterward, the female lays clusters of grapelike eggs inside her nest. She will not leave her nest in the month to 6 weeks that it takes for the eggs to hatch. Because female octopuses do not eat while they are guarding their eggs, it is not uncommon for them to die of starvation. The eggs hatch into larvae that look like tiny versions of their parents. They come to rest on the seabed, where they mature quickly.