Giant Pacific Octopus

Description

The giant Pacific octopus (Enteroctopus dofleini) is the world’s largest octopus. An average adult giant Pacific octopus weighs around 35pounds and has an arm span of approximately 15 feet. The record for the largest giant Pacific octopus is 300 pounds and had an arm span of 32 feet but there is said to have been one that weighed approximately 600 pounds. They are found in cold, oxygen-rich waters from Baja California to Alaska and Russia, Japan, and Korea. They are typically found in the intertidal zone but can be found at depths of 2,000 m. The tentacles are covered in suction cups and they average about 2,200 suctions per individual. Giant Pacific Octopuses are red/pink in color but they have the ability to change the color and texture of their skin to blend in to their surroundings. They have a very strong beak which is the only hard part of their body. The octopus can fit through any opening that they can get their beak through. The giant Pacific octopus has an average lifespan of 3-5 years and they spend most of their lives alone.

Reproduction

Giant Pacific octopuses are semelparous which means they only reproduce once before dying. The male octopus inserts a sperm sac called a spermatophore into the female’s mantle where she stores it until it is needed. The females can lay 100,000 to 400,000 eggs which she guards until they hatch. The females stop eating after laying eggs because they care for the eggs so intensively. The eggs hatch after about 6 months and the female dies shortly after the eggs hatch due to starvation. The octopus hatchlings are about the size of a grain of rice and they drift around eating plankton for a few months. It takes the young octopus about a year to reach a couple pounds.

Feeding Behavior

The giant Pacific octopus mainly feeds on crabs, clams, fish, mussels, and other crustaceans. They are also known to feed on small sharks such as the spiny dogfish. The shells and other remains of their prey are left in piles called middens outside of their dens. Octopuses try to pry apart the shells of their prey first but if this technique is too difficult they use a drilling technique to access the contents inside the shell. A third, but less used technique is to chip the edge of the shells with their beak. The octopus uses its radula to drill a hole into the shell and then it injects a toxin that is used to paralyze the prey. The octopus is then able to extract the contents that are in the shells.

Intelligence

Octopuses are the most intelligent invertebrates and have the ability to open bottles and solve simple puzzles. Octopuses also have the ability to recognize individual humans. They can memorize visual patterns and differentiate between abstract shapes as well as learning by observing other octopuses. In one study, eight wild giant Pacific octopuses were placed in individual tanks in an aquarium and the same person always fed each octopus. One other person also irritated each octopus by touching the octopus with a bristly stick. The two people fed and irritated the octopuses for 10 days and recorded the reactions each time. There were four responses that were differing between the feeder and irritator. The responses were movement, respiration rate, direction of funnel, and presence or absence of an eyebar. They found that the octopuses would move toward the feeders and away from the irritators and they would display eyebars more often to irritators than to feeders. The octopuses also had higher respiration rates for irritators and tended to aim their funnels and water jets toward irritators and away from feeders. This study shows that octopuses can remember how individual people treat them and they can recognize humans.

Works Cited

Anderson, R. C., & Mather, J. A. (2007). The packaging problem: Bivalve prey selection and prey entry techniques of the octopus Enteroctopus dofleini. Journal of Comparative Psychology, 121(3), 300-305.

Brady, Megan, et al. “Giant Pacific Octopus Behavior and Enrichment.” International Zoo News,

John, R. (2009). "Super Suckers: The Giant Pacific Octopus and Other Cephalopods of the Pacific Coast" by James A. Cosgrove and Neil McDaniel. 2009. [book review]. The Canadian Field-Naturalist, 123(1), 78.

Roland C. Anderson , Jennifer A. Mather , Mathieu Q. Monette & Stephanie R. M. Zimsen (2010) Octopuses (Enteroctopus dofleini) Recognize Individual Humans, Journal of Applied Animal Welfare Science, 13:3, 261-272, DOI: 10.1080/10888705.2010.483892

Scheel, D, and L Bisson. Movement Patterns of Giant Pacific Octopuses, Enteroctopus Dofleini (Wülker, 1910). ac-els-cdn-com.proxy.lib.iastate.edu/S0022098112000354/1-s2.0-S0022098112000354-main.pdf?_tid=5d4a8354-d46d-11e7-8a69-00000aacb362&acdnat=1511895364_23c86d3f9d46d09af20f7d83988eedf5.