|Pacific Giant Octopus|
|Enteroctopus dofleini: The world's largest octopus|
The pacific giant octopus Enteroctopus dofleini is larger than any other species of octopus with an average weight of 60kg. and recorded specimens weighing as much as 270kg with a radius of 9.6m. These giant octopus have a mantel, which looks like a bag, and contains the eyes, brain, reproductive organs and digestive organs. The average mantel size is 50-60 cm long. There are four sets of arms extending from the mantel. Each pair of arms are covered with 280 suckers, except for males third right arm which is specialized to transfer sperm to the female. Each of the arms is equipped with thousands of chemical receptors, which allow the octopus to use these arms to sense the world around them. The pacific giant octopus is made up of almost entirely of muscle, except for its beak, located at the center of their arms; this allows the octopus to squeeze itself through openings the size of its beak or larger. E. dofleini are usually reddish in color, with white suckers, however, they can change both color and texture as a way to communicate, express their mood, or for camouflage.
Habitat and Distribution
E. dofleini can be found from the Baja California to the Aleutian Islands and as far as Japan. They are found most typically and abundantly in the coastal regions of the north pacific. There have been higher population densities found near large kelp forests. The pacific giant octopus prefer habitats with soft sediment with sand, mud or gravel containing large boulders or rock outcroppings where they can make dens. They are usually found in tidal pools to depths of 110m, although can be found much deeper at depths of as much as1500m. They are commonly found in dens or liars under rocks and boulders. E. dofleini is an endothermic species whose metabolism is affected by temperature. The ideal temperature for the pacific giant octopus is between 7 to 9.5 degrees celsius.
E. dofleini are considered generalists and foragers. After the giant octopus obtains its prey, it returns to its den to consume it, discarding the remains in a pile in front of the dens entrance; this pile is called a “middens”. From examinations of middens can be determined that the main diet of E. dofleini consists of primarily clams, crabs, fish, and squid. The giant octopus has developed specific techniques to successfully hunt their pray, including laying still and camouflaged to ambush, stalking their prey slowly, or out chasing prey. When the pray is armored, the giant octopus either pulls apart the shell with their strong arms, crushes the shell with its powerful beak, or drills through the shell with an organ called the salivary papilla, which is located in the mouth. The salivary papilla is round and covered with many sharp teeth. Once a hole has been drilled, E. dofleini injects a toxic saliva which paralyzes the prey and starts to digest it.
The pacific giant octopus will breed throughout the year, although the main spawning is in the winter. E. dofleini reach sexual maturity between 3-5 years of age. Males will mate with multiple females, but females will mate with only one male, once in her life. Mating can take from 2-3 hours. The male octopus’ third right arm, called the hectocotylized arm, is specialized for the transfer of sperm to the female. Males use the hectocotylized arm to grab two spermatophores (sacs of sperm) from under their mantel and transfer them into the females oviduct located under her mantle. The sac then breaks, releasing millions of spermatozoa. The female lays an average of 50,000 eggs, but clutch sizes range from 20,000 to 100,000eggs. The small rice shaped eggs are dangled from the ceiling of her den in clusters of 200 to 300 eggs in each cluster. The females keep guard over the eggs, cleaning and aerating them. Hatching takes approximately 150 days but can take up to a year, depending on the water temperature. Embryos take longer to develop in colder waters. The Mother E. dofleini dies shortly after the hatch.
The pacific giant octopus is an independent from birth. After hatching, E. dofleini swims to the surface and spends the next 4-12 weeks as plankton drifting in the oceans currents. When the young are approximately the weight of 4 grams, they settle on the bottom looking for rock dens, where they can hide and grow. The average life span of E. dofleini in the wild is 3-5 years; the same has been observed in captivity. Behavior: The Pacific giant octopus is a solitary animal, spending most of its time in its den. Most E. dofleini have a small home range, generally traveling withi a 5 km radius from their den to search for food. E. dofleini are considered very intelligent and curious, and they are excellent problem solvers. They have a large brain to body ratio, with thousands of chemical sensory receptors on their arms which they use to taste and smell. They have very acute vision and in captivity are known as extreme escape artists.
- Anderson, R., J. Mather. 2007. The packaging problem: bivalve prey selection and prey entry techniques of the octopus Enteroctopus dofleini. Journal of Comparative Psychology, 121/3: 300-305. - Anderson, R., J. Wood, R. Byrne. 2002. Octopus senescence: the beginning of the end. Journal of Applied Animal Welfare Science, 5/4: 275-283. - Kubodera, T. 1991. Distribution and abundance of the early stages of octopus, Octopus dofleini wulker, 1910 in the north Pacific. Bulletin of Marine Science, 49: 235-243. - Scheel, D. 2002. Characteristics of habitats used by Enteroctopus dofleini in Prince William Sound and Cook Inlet, Alaska. Marine Ecology, 23/5: 185-206. -Scheel, D., A. Lauster, T. Vincent. 2007. Habitat ecology on Enteroctopus dofleini from middens and live prey surveys in Prince William Sound, Alaska. Pp. 434-458 in N. Landman, R. Davis, R. Mapes, eds. Cephalopods Present and Past: New Insights and Fresh Perspectives. Dordrecht, The Netherlands: Springer. - Schwab, I. 1987. A well armed predator. British Journal of Ophthalmology, 87/7: 812. Cosgrove, J.A. 1987. Aspects of the Natural History of Octopus dofleini, the Giant Pacific Octopus. M.Sc. Thesis. Department of Biology, University of Victoria (Canada), 101 pp. -Artwork by Nicholas S. Louis