The 12 Days of Fishmas: And a Giant Pacific Octopus…

Starting Dec. 12, we’ll be blogging the “12 Days of Fishmas.” Each day we’ll feature a different species that you can see during your visit to Birch Aquarium at Scripps. Love this species? Consider our Adopt-A-Fish program and help us keep these animals thriving!

The reddish-brown body of the Giant Pacific Octopus consists of eight arms and a “mantle,” which extends from the head like a bag and has two sets of gills. Each arm has two rows of suckers numbering about 240, for a grand total of about 1,920. Some of the suckers have taste sensors on them, which is useful for finding food in small caves or crevices. The suckers also help octopus arms grip the surface when crawling about the sea floor.

Three Hearts and a Beak

All of the octopus’ internal organs are contained in its mantle, including a brain and three hearts. Their brain is about the size of a walnut, which is on the large side for an invertebrate. Each set of gills has one heart dedicated to pumping blood to it, and the third heart pumps blood to the rest of the body. Due to its high copper content, octopus blood is blue.

The gills allow an octopus to breathe in oxygen and then exhale through a tube called a siphon. If an octopus breathes fast and exhales hard, it can swim backward by jet propulsion.

Clouds of Ink and Camouflage

At the base of the siphon is an ink sac from which an octopus can squirt a cloud of ink to confuse predators while they make a quick escape. The ink not only obscures vision but also smell, and its main ingredient is something they have in common with humans – melanin, the substance that gives color to human hair and skin.

Octopuses can also add a toxin to the ink that paralyzes and/or puts animals to sleep, making it easier to pull snails off rocks or carry crabs back to their den. Their mouths contains a very sharp beak made out of keratin – the same substance that forms the human fingernail – and a tongue covered with sharp teeth called the radula.

Octopuses have special organs in their skin called chromatophores that contain pigments and are controlled by the nervous system. By arranging them in certain color patterns and skin textures, they can camouflage or send messages like warning signals to other animals.

What’s for Dinner?

Octopuses are shy and like to hide under or among rocks during the day. They forage for food at night and usually take the meal back to their dens to eat. The inside of an octopus den is pretty tidy because they throw empty shells, spines, and bones an arms length out their front door. Divers sometimes find their hiding places by this pile of debris, often referred to as an “octopus’s garden.” (And yes, that was the inspiration for the Beatles song!)

An octopus’ diet includes shrimps, crabs, scallops, clams, abalone, moon snails, small octopuses, and fish. Between their suction-cup covered arms, sharp beak, and radula, octopuses have several ways of getting their prey that involve prying, biting, and/or drilling holes in shells. Predators include large and aggressive animals like the moray eel and various sharks.

Life in the Aquarium

Visitors have expressed concern that the Giant Pacific Octopus doesn’t have enough room to move about its tank, but remember that they prefer crevices and caves – corners actually suit them quite well! Octopuses are intelligent creature; they can solve mazes, unscrew jar lids to get to food inside, and even mirror the actions of another octopus in a separate tank. Our aquarists ensure that the octopus has plenty to do.

What IS the plural of “octopus”?

“Octopuses” is the current accepted form in the United States. The Oxford English Dictionary also lists “octopodes” (rare) and “octopi “(disputed). The former is more technically correct since “octopus” is derived from the Greek “oktopous”.

Fishy Facts

  • Because they are generally shy, an octopus is not considered a dangerous animal. In fact, it takes a lot to get them riled up. However, their beak is sharp enough to crush snail shells and the toxin in their saliva can be very painful, so it’s never a good idea to provoke an octopus.
  • Giant Pacific Octopuses can live to the ripe old age of four or five years but not much longer. In fact, they die shortly after mating. Females actually don’t eat while taking care of their eggs and die soon after the eggs hatch.
  • The biggest Giant Pacific Octopus recorded weighed in at 300 pounds and its arms measured 32 feet from tip to tip – the height of a three-story building. However, most of them don’t grow to more than 100 pounds with an arm span of 16 feet. Of course, if you consider that the average Labrador retriever weighs about 70 pounds, that’s still not small either!

Come see our Giant Pacific Octopus this holiday season

Adopt a Giant Pacific Octopus for the Holidays

The Giant Pacific Octopus is just one of the 3,000 fish and invertebrates that thrive at Birch Aquarium at Scripps. By adopting one today , you can be part of the team that provides essential care to these special ocean inhabitants. Find out more about the Aquarium’s Adopt-a-Fish program.

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Scripps Institution of Oceanography UC San Diego