The Insane Biology of: The Octopus

In many ways, the octopus is as close to alien life as we may ever see. Few creatures in

the world are as remarkable and bizarre. A part of a class of animals called cephalopods,

they are among the most intelligent and most mobile of all the invertebrates. They live

in every ocean in the world, in the deep sea, in kelp forests, in coral reefs, along rocky

shorelines. And they are as diverse as the habitats they live in. They can be massive,

or absolutely tiny. Some species are venomous, and some are just downright strange. In any

given moment, they can appear spikey, or they can appear smooth. They are so different from

us, that most of their 500 million neurons are not in their brain, but in their arms,

which can smell and taste, and even think. And so intelligent that their cognitive ability

matches that of many large-brained vertebrates.

They have left scientists stunned about how a creature so far from us on the evolutionary

tree could evolve such complex behaviors, their intelligence emerging in an entirely

novel and independent way from our own.

So how did the octopus become so biologically complicated - an island of complexity in the

sea of invertebrate animals? Just how intelligent are they, and how can studying them reveal

information about our own minds?

Cephalopods have been around for a long time. Fossil records show that they evolved over

500 million years ago - long before any fish, reptiles, or mammals appeared on earth. The

early ancestor of the octopus was quite small and had a shell, which it used to protect

itself as it crawled along the ocean bottom. Cephalopods are, after all, members of the

mollusk phylum. A group of creatures that are usually slow and simple, with soft bodies

and a hard protective shell - like snails, clams, and oysters. But around 140 million

years ago, the lineage that produced the octopus lost their shells, making them nimble, agile

creatures, but in the process also made them rather vulnerable. Survival of these soft

bodied creatures for so many millions of years therefore seems unlikely in a sea full of

dangerous, hungry predators. But this vulnerability and selective pressure may be precisely what

has allowed the octopus to become the remarkable creature we know today.

Because an octopus has almost no hard parts at all, except its beak, it can squeeze through

any hole as long as it’s larger than its eyeball. This allows the octopus to hide in

very small crevices - a certain evolutionary advantage when escaping large predators like

sharks or dolphins. But, the soft-bodied octopus evolved an even more clever way of evading

detection: they are masters of disguise.

Watching this clip of an octopus, you can see just how quickly and drastically it can

change colors. In slow motion reverse, you see the color change spread across its body.

The 3D texture of the skin also changes, to match the surrounding seaweed and coral. In

the blink of an eye, it has almost completely blended in with its surroundings. Cephalopod

camouflage is among the most dynamic in the animal kingdom, and relies on a system of

extremely sophisticated tissues.

Chromatophores are organs that are speckled across the skin of the octopus, like freckles.

They contain tiny pigment filled sacs, like little balloons full of different color dye,

which can be black, red or yellow. The pigment sacs are surrounded by radial muscles, which

can stretch the sac to reveal the pigment’s color. Just like balloons full of dye, when

stretched, their pigment color appears bright and vibrant. Depending on which sets of sacs

an octopus opens or closes, it can produce patterns such as bands, stripes, or spots

- helping to turn itself into a rock, a coral, or kelp in an instant.

But if the octopus needs to produce colors outside of black, red, and yellow, it uses

another layer of reflective structures in their skin called iridophores. They are stacks

of very thin cells that lay beneath the chromatophores. They contain a protein called reflectin that

bounces certain wavelengths of light back out. They are responsible for the metallic