Devil Fish or Gentle Giant?

by Gail Wellenstein, Kitsap Beach Naturalist

The octopus is an unlikely creature, living a solitary life out of view in the ocean with a body structure so completely different from any land animal that it is easy to think of them as alien creatures. They have been feared for centuries, called Devil Fish and Kraken, and in 1940 the collapse of the Tacoma Narrows Bridge was linked to a giant octopus that was rumored to be living among the sunken remains. 

Kakantu, Giant Pacific Octopus, at Port Townsend Marine Science Center. Photo credit: Gail Wellenstein

The largest of the octopus species is our very own Giant Pacific Octopus, living in the northern Pacific from Korea to Mexico. Their tentacle span is between 7 and 14 feet when full grown and they can weigh as much as 50 pounds with a rare outlier coming in at 200 pounds and 20 feet. What is truly incredible is that they achieve this size over three to five years, at the end of which they mate and die.

The Giant Pacific is orange to reddish brown with two independently moving large eyes and on the undersurface below is their mouth, surrounded by eight flexible arms. On the other side of their head is a balloon-like mantle which houses their internal organs and their gills. The octopus inhales water through a cavity at the base of the mantle, passes it over the gills and releases it via a flexible tube called a siphon, also used for jet propulsion and other tasks.

The mouth of the octopus contains a parrot-like beak used to break apart shellfish. They have a tongue-like radula to drill holes into harder shells and can inject venom into prey to immobilize it. The beak is the largest hard part of this invertebrate, so a 50-pound octopus can go through an opening that is the size of a lemon. A large octopus was filmed poaching a crab pot, initially trying to catch the crabs by inserting a few tentacles; when that failed, he moved his entire body through the opening, ate the crabs and exited via the entrance.

The octopus brain is shaped like a donut, encircling the mouth, and sending a large nerve cord down each arm. These eight nerve cords connect to each other in a separate ring below the brain. Each arm can function independently and send signals to the other arms, bypassing the primary brain altogether. Suckers and skin are loaded with receptors that detect chemicals, light, and pressure, image tasting and smelling an object just by touching it. The suckers are able to hold 30 pounds each giving them an ability to pull an object 100 times its weight.

Octopus are masters of camouflage. They use their skin and eyes to sense the contours of the environment and change the texture of their skin to match the area around it. Millions of tiny elastic pigment sacs expand or contract via muscles to instantly change the skin color while specialized skin cells reflect light to create a white appearance. What is perplexing about this camouflage trick is that an octopus is color blind; they rely on light-sensitive proteins in their skin that essentially allow their skin to “see” independently. These color and texture changes can also signal mood; I’ve watched Kakantu flash red when excited and look nearly white when relaxed.

How do you tell the gender of an octopus? Find the third arm on the right and look at the tip. If there are suckers all the way to the end, it is female; if there is an absence of suckers near the end, and a groove, it is male. The male moves sperm packets from inside the mantle, down the arm and to this groove. It then inserts the end of this tentacle into the mantle of the female, delivering the sperm packets. This is best done at arm’s length as the female has been known to attack the male. When mating is accomplished, the males will die, while the females suspend up to 100,000 eggs in their rocky den, circulating water and keeping predators away without eating for an average of six months. Shortly after hatching the female dies and the rice-sized young rise to the surface and join the horde of zooplankton where they will drift for one to three months, feeding on other zooplankton. Only one percent survive this phase and the lucky ones then settle on the ocean floor where they will grow rapidly to become a dominant predator on the seafloor.