The Odd, Odd Octopus

You know octopuses are strange creatures. They've always been part of our nightmares and scary stories, but that's mainly because they look so odd. The more you know about them, the stranger they seem.

Eight Limbs

Tell me, O Octopus, I begs
Is those things arms, or is they legs?
I marvel at thee, Octopus;
If I were thou, I'd call me Us.
-Ogden Nash

We've only recently found the answer to this question. Octopuses have two legs and six arms. Good luck telling them apart, but the octopus knows! They tend to push off surfaces and crawl with the two limbs furthest back, and use the others to feed. The research originally meant to find if octopuses were right- or left-handed. They are neither, but many tend to use the third arm from the front, on both sides, for many tasks.

Muscles

This post was inspired by a conversation with my daughter about anatomy, in which  she posited that without bones, we wouldn't be able to move. The octopus has no skeletal system and still moves quite well. They crawl along surfaces with their legs and arms and swim by moving with wave action or by spurting water from its mantle cavity, which is used for respiration, but can also propel an octopus at up to 20 miles per hour in larger species. The octopus' intricate muscular system plays a part in its other odd features: flexibility, suckers and camouflage ability. (image credit: Erica Simone)

Flexibility

There are advantages to having no skeleton. An octopus can squeeze through any opening larger than its beak, its only inflexible part. This allows an octopus to nestle inside crevices of any shape, as long at the volume is sufficient.

Camouflage

An octopus can change color at a moment's notice. Faster than that, actually. Tiny pigment sacs called chromatophores with up to five colors lie beneath the skin. Rings of muscle control the release of pigment to match the terrain an octopus covers, or when it decides it must blend in with the background to fool predators. Can you spot the octopus in the left picture? Watch the video.

Suckers

Each sucker on an octopus tentacle has a ring of muscle that contracts when it must stick to a surface, creating a vacuum inside the seal. If a predator tries to pull it away, a "piston-like structure" inside pulls up and boosts the vacuum seal.

Beak

The only hard part of an octopus is its beak, which it uses for eating and defense. Until recently, scientists wondered how they used this one hard organ without hurting the other soft organs. Recovered beaks are composed of hard chitin, but beaks on a living squid have been observed to be very different. The chitin shows a gradual shift from unbreakably hard at the tip to softer material where it attaches to the muscles of the mouth. This gradation is believed to be present in an octopus' beak as well as squid.

Ink

In addition to its many other defenses, an octopus produces ink made of natural red melanin. It appears a dark brown when concentrated. A squirt of ink can help camouflage an animal, or distract a predator while the octopus escapes. The ink also contains tyrosinase, which irritates a predator's eyes. The few octopus species that don't produce ink tend to live in deep water, where visibility is already low.

Intelligence

Octopuses are highly intelligent and can learn new tasks even as adults. The learning power of an octopus is only restricted by its short life span, which ranges from six months to a few years. They often manipulate their environment in ways that suggest playing in addition to regular life tasks. In captivity, they play with toys such a Rubik's cube, and even have preferences like Louis, who is attached to a Mr. Potato Head.

Some octopus species are stranger than others. The blue-ringed octopus carries enough venom to kill ten people.  The deep-sea finned octopus glows with a blue-green light. With 300 different species, they are the masters of survival in many ways.