In a sea of the weird and mysterious, one creature has inspired legions of sea monsters from the legendary Kraken to the Cthluhu (ku-thoo-loo). With its long sucker-studded arms, bulging eyes and eerily malleable body, the octopus beguiles as much as it bewilders. But there’s more to this whip-smart cephalopod.
First of all, here’s a look at the octopus’ anatomy:
1. Three hearts
As alien as it sounds, the octopus has not one but three hearts. One of the hearts, called the central heart, pumps blood throughout the animal’s body to keep circulation flowing for the organs. The other two, called lateral hearts, receive deoxygenated blood from the body and pump it through the gills for respiration and gas exchange, and back to the central heart.
Fun fact: The octopus’ central heart stops beating when it swims. This is why it prefers to crawl than swim because swimming is more exhausting.
2. Blue blooded
Like their cephalopod relatives such as squids and cuttlefish, the blue pigment in the octopus’ blood is derived from a copper-rich protein called Haemocyanin, which carries oxygen from the lungs to the bloodstream and then to the cells of their body.
Being more efficient at transporting oxygen than hemoglobin, this copper-rich blood helps them cope with the low oxygen levels in the depths of the ocean.
Fun fact: An octopus’s blood is only blue when it is oxygenated; by the time it gets back to the lateral hearts, the deoxygenated blood is essentially clear.
3. Camouflaging shape-shifter
The octopus is boneless and has few hard body parts. Apart from its eyes and parrot-like beak, the rest of its body is infinitely malleable. So much so that it can thread itself through a hole not much larger than the diameter of its eyeball. This ability to squeeze into almost any nook and cranny allows them to evade predators in the wild.
In 2016, an octopus named Inky escaped from the national aquarium in New Zealand by breaking out of its tank, slithering down a 50-metre drainpipe and disappearing into the sea. Click here for details of his brazen escape.
The octopus also employs active camouflage (sometimes called adaptive colouration) where they change their body colour rapidly to blend in with their environment.
Fun fact: The octopus can also control the texture of its skin to match that of surrounding rocks, sand or algae. The secret lies in the network of finely controlled muscles beneath its skin that can create bumps, ridges or even spikey horns.
4. Bizarre mating ritual
The female octopus is often larger and hungrier than the male, so there is always a chance that instead of mating, the female will kill and eat him.
To survive the mating process and pass on his genes, most male octopuses mate at arm’s length – by inserting their spermatophores (packets of sperm) directly into a tubular funnel that the female uses to breathe.
As for the females, they can lay up to 400,000 eggs, which they obsessively guard and tend to. She will hardly leave or eat during this period of time which can last between two to 10 months before the eggs hatch.
Shortly after the eggs are hatched, she usually dies from starvation and exhaustion. The tiny baby octopuses are then left to fend for themselves.
Fun fact: The male octopus often dies within a few months after mating.
5. Armed with intelligence
A highly intelligent marine animal, the octopus has one of the largest brain to body size ratios for an invertebrate, and a very well-developed central nervous system. Its eight arms contain close to 500 million neurons to touch, taste, explore and grip its prey (roughly the same as a dog’s but most of the neurons are found its arms which allows the arms to act independently from the brain).
Like humans, the octopus has short- and long-term memory, which makes them pretty good at solving puzzles and mazes. Here at S.E.A. Aquarium, we introduce environmental enrichment for Ollie, our Giant Pacific Octopus. We add foreign objects like toys, puzzles and bottled food (where he learns to unscrew the lid to retrieve the food within), so as to maintain healthy activity levels for him.