Tuesday, August 2, 2011

Life of North Pacific Giant Octopus

Life of Sea | North Pacific Giant Octopus (Enteroctopus dofleini) | This enormous octopus is included to the genus Enteroctopus. In their natural habitat, you can see them at in a range of depths from shallow waters of less than 5 m, down to depths of 1,500 m. North Pacific giant octopus likes to live in areas with large boulders and rocky reefs, using the crevices in rocks to make dens in which it shelters.  It ranges in coastal waters of the North Pacific Ocean, ranging from California, north to Alaska and the Aleutian Islands, and across to Japan. North Pacific giant octopus usually feeds on bivalves, crabs, and lobster. However, they will eat variety of species. They have also been observed eating fish, sharks, and even birds.

North Pacific giant octopus has a reddish-brown body called mantle. Additionally, it has four pairs of arms, measuring on average about 4.9 m long. The weight for a giant octopus can reach 272 kg, but most weigh about 23-41 kg. Young giant octopus is only the size of a grain of rice. Octopuses have the most complex brain of the invertebrates. Like vertebrates, they also have long term and short-term memories. Octopuses learn to solve problems by trial-and-error and experience. Once the problem is solved, octopuses remember and are able to solve it and similar problems.

Most octopuses hunt at night. It is thought that they scout out promising feeding grounds by sight and then extend their sucker-studded arms to explore the area by touch. Mature female North Pacific giant octopus have 280 suckers on each arm, each sucker containing thousands of chemical receptors. The sensitivity of an octopus's suckers to touch and taste allow it to grope for food in small, dark crevices. When an octopus makes a delectable discovery, it lunges and delivers the prey to its mouth. 

Octopuses use three different techniques to gain entry to hard-shelled prey. They may pull it apart, bite it open with their beak or 'drill' through the shell. Prey that are difficult to pull or bite open are drilled, secretions from the salivary papilla soften the shell of the prey and the softened material is then scraped away with the radula to create a tiny hole in the shell. Through this hole, the octopus secretes a toxin that paralyzes the prey and begins to dissolve the connective tissue. The prey is then pulled apart and consumed.

North Pacific giant octopus lives 3-5 years. When sexually mature, females lay eggs on the inner side of a rocky den and may lay 20,000 to 100,000 eggs over a period of several days. Eggs are tended, cleaned and aerated by females until they hatch. Incubation takes 150 days to 7 or more months, depending on the temperature. Females do not feed while tending eggs and die when the eggs hatch or shortly thereafter. Many of the eggs will die if not tended by the female until hatching.

Dens are an important resource to octopuses during all benthic life stages. Dens are used both as brooding chambers and as refuges from predators, including other octopuses, various fishes, and many marine mammals. Most dens of juvenile giant octopuses are naturally occurring spaces under rocks or in crevices or are an excavated cavity in sand or gravel under a boulder.

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