As the name suggests, World Octopus Day celebrates one of the most distinctive creatures living on the planet today; the octopus.

Found worldwide in the shallow waters of tropical, subtropical, and temperate areas, the common octopus is a fascinating creature.

Common Octopus

Similar to a squid, the common octopus is classified as a mollusk, which is a soft-bodied invertebrate with a shell. It has no skeletal structure but does possess a skull, which protects its brain. It also has a sharp beak and a toothed tongue called a radula, which it uses to pry open and drill into the shells of prey, like crabs and clams. Once it breaks into the shells, it may also inject a paralyzing poison into its prey.

Common Octopus
Common Octopus

Three hearts, nine brains and blue blood

An octopus has three hearts, nine brains, and blue blood. Two hearts pump blood to the gills, while a third circulates it to the rest of the body.

The nervous system includes a central brain and a large ganglion at the base of each arm which controls movement.

To survive in the deep ocean, octopuses evolved a copper rather than iron-based blood called hemocyanin, which turns its blood blue. This copper base is more efficient at transporting oxygen then hemoglobin when water temperature is very low and not much oxygen is around.

Six arms and two legs

While it was commonly believed that the octopus’s appendages were all arms, recent studies by marine experts have shown that two of the limbs act more as legs, allowing it to walk across the sea floor and push off when swimming. The octopus also has the useful ability to regenerate a tentacle if it loses one.

Defense tactics

Its first—and most amazing—line of defense is its ability to hide in plain sight. Using a network of pigment cells and specialized muscles in its skin, the common octopus can almost instantaneously match the colors, patterns, and even textures of its surroundings. Predators such as sharks, eels, and dolphins swim by without even noticing it.

Octopus camouflage
Camouflaged – Photograph course of Barcroft Media

When discovered, it will release a cloud of black ink to obscure its attacker’s view, giving it time to swim away. The ink even contains a substance that dulls a predator’s sense of smell, making the fleeing octopus harder to track.

Octopus sprays ink to escape predators
Spraying ink to escape predators

Sense taste

The octopus’ suction cups are equipped with chemoreceptors so it can taste what it is touching.

A common octopus has more than 200 suckers on each arm,
More than 200 suckers on each arm,

Fast swimmers

An octopus can reach speeds as high as 40 km/h (25 mph) by expelling water through it’s mantle. They cannot maintain this speed for long.

Octopus swimming
Swims by expelling water through it’s mantle

Biggest and smallest

The Giant Pacific Octopus grows bigger and lives longer than any other species. The size record is held by a specimen that was 30 feet (9.1 meters) across and weighed more than 600 pounds (272 kilograms). Averages are more like 16 feet (5 meters) and 110 lbs (50 kilograms).

Giant Pacific Octopus
Giant Pacific Octopus

Octopus Wolfi is the world’s smallest octopus, at a length of less than an inch and weighing less than a gram. It is found in relatively shallow waters, between 10 and 100 feet, in the western Pacific.

Octopus Wolfi
Octopus Wolfi

So how will you celebrate World Octopus Day? Get out your snorkelling gear and see if you can spot one in the local bays? Take a trip to a sea life centre? Or simply learn more about these fascinating creatures.

As for the culinary delights…well that’s another story!