Have you seen the movie Pirates of the Caribbean? If so, do you remember the terrifying tentacle-faced villain, Davy Jones? His famous face and beard must have reminded you of one of the most unique and fascinating marine animals — the octopus! With their rounded heads, bulbous bodies, bulging eyes, and, most significantly, eight long arms flowing like a skirt, it is hard not to imagine that octopuses could be visitors from another planet. But there’s more to these creatures than just having multiple arms — they are actually intelligent and highly evolved too!
With new species being discovered every year, the variety in octopus shape, size, and colour is truly astonishing! The smallest known is the Octopus wolfi, so small that it can comfortably sit on a human fingertip. Commonly known as the star-sucker pygmy octopus, it is 2.5 cm long, and weighs less than a gram. On the opposite side of the pole is the giant Pacific octopus. Females of this species have a remarkable 5 metre or 16-foot-long arm span, and a weight of 70 kg! Their habitats are also diverse. While most species prefer shallow areas, several are adapted to the extreme depths of the ocean, like the glass octopus that can thrive at a depth of around 1,000 metre (over 3,000 feet!). Glass octopuses are transparent but just like any other octopus, they too have the tendency to change colours. In fact, octopuses can not only do this, they are also known to change their patterns with surroundings to camouflage, tactics used to escape predators. What is astounding is that all octopuses are actually colourblind, which makes their abilities extraordinary to scientists studying them.
Octopuses can do things that most other sea animals cannot, and scientists have proven that these creatures are incredibly smart. In aquariums, octopuses have figured out how to unscrew jars, open boxes, and get food! (Remember Hank from Finding Dory?) In another study conducted in New Zealand, it was observed that an octopus can even learn to recognise human faces! One of the octopuses began to recognise a staff member, and squirted water at her every time she walked past the tank. In the wild waters, as many as 20 Amphioctopus marginatus, commonly known as coconut octopuses, have been observed carrying around empty coconut shells and seashells to use as portable armour, shielding themselves when predators approach.
There’s a lot to know about this intriguing species. Read on to explore more fascinating facts about the octopus!
- Don’t require bones to move
Octopuses are invertebrates (animals without a skeleton) made up of 90% muscle. Their completely boneless, squishy body allows them to perform amazing tricks like expanding to intimidate predators or squeezing their entire bodies through small crevices. The only hard part of their body is their mouth, which looks just like a parrot’s beak. It is hidden at the centre of where all eight arms meet, and is perfectly useful for cracking open the hard shells of their crustacean prey.
2. Three hearts beating fast!
The inside of an octopus’s body is just as complex as the outside. They do not have just one heart, they have three! There are two branchial hearts that drive deoxygenated blood directly to the gills, and the third heart is the systemic heart, which circulates the oxygen rich blood throughout the body.
3. Brimming with blue blood
Remember the cartoon series Oswald? It was named after a blue coloured, kind octopus playing the lead role. Turns out, octopuses are truly blue from the inside! Their arteries and veins circulate blue coloured blood throughout their body.
In the deep ocean, both the temperature and the oxygen concentration is low, and octopuses require a lot of energy to move their muscular bodies. This results in a high metabolic rate along with a significant need of oxygen. In order to meet such a high demand of oxygen, their blood has uniquely adapted. Unlike human blood, which relies on iron-based haemoglobin, octopus blood uses a copper-based protein called hemocyanin, which also turns their blood blue! It is observed that hemocyanin is far more efficient at transporting oxygen in such cold and low-oxygen environments, which is crucial for the octopus to survive.
4. The power of nine brains
Octopuses belong to the group cephalopods, a Greek term that translates to “head-foot”. This name holds true for an octopus as its arms are attached directly at the bottom of its head, with no true body form in between.
Octopuses are widely considered to be the most intelligent invertebrates on Earth, but their brainpower isn’t concentrated in one place. This is because unlike other animals, they have a total of nine brains! They have one main, doughnut-shaped central brain that surrounds their oesophagus, accompanied by large clusters of neurons that act like ‘mini brains’ located in each of their eight arms. These mini-brains control the specific, localised movements of the arms, allowing them to react to their environment independently.
5. Arms that can ‘taste’ and ‘think’
Each arm is lined with around 40 million neurons, giving each of them a significant local control. Further, each arm has the ability to actually taste the chemical signals given off by bacteria to figure out if a meal is safe to eat!
Because of their well connected nervous system throughout their body, the arms don’t need instructions from the main brain. Interestingly, in an event where the octopus arm is severed, the detached arm can move and react to stimuli for at least an hour while the octopus works on regenerating its lost arm.
6. One of the best camouflage artists
The octopus is sure to win a game of hide and seek, because they possess amazing shape-shifting and cloaking abilities! Right under their skin, they have hundreds of thousands of specialised pigment cells called chromatophores. In a fraction of a second, these sacs adjust their colours to flawlessly blend with their background! But it is not just about colour. Some species, like the common octopus, can also alter muscular bumps on their skin called papillae, to perfectly mimic the physical texture of rocks, kelp, or coral.
7. A dangerous cloud of ink
When threatened, an octopus has the ability to release a puff of black ink through its tubular organ called siphon. This cloud can distract, confuse, and even paralyse predators. The ink is a mixture of mucus and melanin. Melanin is the same dark pigment found in our hair, skin, and eyes. The ink also contains tyrosinase, a chemical that severely disrupts the predator’s senses of smell and taste. The sticky mucus can even clog a chasing fish’s gills, suffocating it. However, this brilliant defence comes with a risk! If the octopus doesn’t escape its own ink cloud quickly, its toxicity can impair its own respiratory system, leading to fatality.
8. Short lifespan of octopus
Octopuses usually have a short lifespan. Some species, like the common octopus and the blue-ringed octopus, live for only 12 to 18 months, while others like the giant Pacific octopus can live for 3 to 5 years! However, unlike many other animals, octopuses reproduce only once in their lives and then die, biologically known as semelparity.
After mating, male octopuses die relatively quickly, while the females die as soon as their eggs hatch. Death is an inevitable stage once the octopus has reproduced. The organ controlling this process is the optic gland. Located near the eye, this pair of endocrine organs releases chemical signals and brings about hormonal changes that inactivate the digestive glands, and completely suppress their appetite, ultimately causing death by starvation.
With mother octopuses, it is a whole other story. Once she lays her eggs, the optic gland begins secreting chemicals and inhibits her digestion and salivation. This diverts her energy towards incubating her eggs, and protecting them from bacteria and predators.
During this entire incubation period, she gives up food entirely, starving herself for months, or even years. Graneledone boreopacifica, a deep ocean octopus species, starves herself for around four years. Ultimately, her body releases self-destructive hormones that end her life just as her offspring hatch!
Those were indeed some intriguing insights about the octopus. But why should we even be interested in knowing about an eight-armed underwater animal anyway?
Octopuses are considered a keystone species because they undertake multiple responsibilities. They keep the ocean’s ecosystem balanced by playing a crucial role in the food web, and preying on small animals like crabs and fish to control their populations, while simultaneously serving as an important meal for larger marine animals like sharks and seals.
They construct safe havens like dens and burrows, which once abandoned, can be used for shelter by small fish and other marine life too. Even after they die, the octopus carcass can produce energy and nutrients that help aquatic species, while their bodies on the ocean floor can store carbon which eventually regulates the climate of our planet!
However, these creatures are facing serious threats due to the rapidly changing ocean temperatures. A rise in ocean temperature can severely affect the biological progress of young octopuses, increasing their mortality rate by 30%! According to a study, even a 3-degree Celsius increase in water temperature impacts their eggs and prompts them to hatch prematurely, further decreasing their probability of survival.
But the unnaturally changing climate is not the only battle they are fighting. Human activities are also causing pollution and unsustainable fishing practices, which are equally massive barriers to their survival. The common octopus, Octopus vulgaris, which is considered to be a culinary delicacy, is facing severe declines due to overfishing. On the other hand, polluted waters that are known to be a chronic issue for coral reefs and seagrass are also impacting octopuses. They are highly sensitive species that are struggling with their ability to reproduce.
Octopuses are remarkably intelligent creatures. They have problem-solving skills and strong senses to touch and taste their environment. They’re incredibly sensitive to physical and emotional pain as well. Curiosity has led many scientists and conservationists to discover mysteries of this enigmatic species. They came together to declare October 8 as World Octopus Day, with the date and month rightly chosen to honour this marine animal with eight brainy legs!
We owe octopuses and all other marine wildlife an unthreatened life and a healthy home. With sustainable practices, strict policies, and proper management programmes, the oceans can remain a thriving, balanced habitat for the wildlife swimming and crawling under water!
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Feature Image: Canva
