An Ode to the Octopus

Octopuses are fascinating animals, and there’s seemingly no end to the list of their intriguing—and sometimes downright strange—characteristics. From independently operating arms and suckers to their inking technique to an alien-like circulatory system, here are some of our favorite facts about these magnificent mollusks.

Sticky Suckers

The eight arms (not tentacles!) of an octopus are amazing appendages. Two-thirds of an octopus’s neurons can be found in its arms—which means that these limbs can operate without help from the central brain, allowing for some seriously impressive multitasking.

Each of an octopus’s eight arms is lined with rows of strong suckers, which change their shape and contract to create powerful suction. Like their arms, these suckers operate independently of one another. They can taste and smell, and they stick to practically every object they contact.

So, with eight different arms that have a mind of their own and hundreds of suckers that stick to everything in sight, how does an octopus avoid entangling itself in an eight-armed knot? It turns out that there’s a fairly simply answer. Research suggests that the secret lies in an octopus’s skin, which appears to produce a chemical signal that overrides the suction reflexes of its suckers. What’s more, scientists believe that these chemical signals may even be unique to each individual octopus.

All About Ink

You probably know that octopuses—as well as squids and cuttlefish, other members of the cephalopod class—can expel a cloud of black ink as a defense mechanism, but did you know that this ink contains the same pigment that’s found in human hair, skin and eyes? This pigment is called melanin and gives the ink its black color. It’s a main component of cephalopod ink, along with a sticky mucus that affects the thickness of the ink.

An octopus can eject this ink cloud to not only evade and confuse predators, but to harm them as well. The ink contains a compound called tyrosinase, which can irritate a predator’s eyes as well as interfere with its sense of smell.

Ink is created and stored in a specialized structure called an ink sac, and it’s expelled from the octopus’s body via the siphon, a tube-like structure at the base of its mantle that plays another key role in an octopus’s defensive strategy. When an octopus is ready to jet away from a potential predator, it fills its cavity with water and then forcefully expels the water out of its siphon. Much like a rocket ship launching into space, this force propels the octopus away from its predator—while also leaving an inky black cloud of confusion in its wake.

Blue Blood and Three Hearts

Like humans, octopuses have a protein in their blood that carries oxygen and provides a distinctive color. In humans, it’s hemoglobin, and it turns our blood red; in octopuses, the protein is called hemocyanin, and it turns their blood a distinctive blue. Hemocyanin is a copper-rich protein that is more effective at transporting oxygen in an environment like the deep ocean, where temperatures and oxygen concentrations are very low.

This blue blood is pumped through not one, not two, but three hearts in an octopus. There are two branchial hearts, which pump blood through an octopus’s gills. The blue blood then enters the systemic heart, which circulates the newly oxygenated blood through the body. If this sounds familiar, it’s because these three hearts work together to perform the function that our one heart does: The branchial hearts function much like the right side of our hearts, which passes blood through our lungs, and the systemic heart much like the left side of our hearts.