Buzz
Octopuses are known for their blue blood, three hearts, and their role in eerie maritime myths. We've compiled a list of some of the lesser-known, strange, and truly astonishing facts that showcase these remarkable creatures, making them some of the most captivating mollusks to ever encounter.
For clarity's sake, the proper plural of 'octopus' is 'octopuses,' or 'octopodes' if you prefer the Greek form, since 'octopus' itself is derived from Greek. In this article, we will be using the English plural form.
10. They Can Hunt Outside of Water
Octopuses possess gills, which means they require water to breathe. Nonetheless, many species have been observed leaving the water temporarily to hunt for crabs stranded on land, and some have even managed to escape from their tanks and traverse rooms to feast on fish in other tanks. There are even reports of octopuses returning to the ocean after escaping! One famous case involves Inky, an octopus from New Zealand, who managed to slip out of his tank and crawl across the floor to find a drainpipe that led him back to the ocean. But how do octopuses manage to survive on land when they cannot breathe air?
Octopuses utilize a process known as passive diffusion, which enables them to absorb oxygen through the water on their skin as long as it remains wet, instead of relying on their gills. This allows them to temporarily leave their aquatic environments for activities like hunting, or in the case of Inky, escaping captivity. Speaking of Inky, he isn't the only octopus to make headlines with such bold acts.
In 2010, a determined octopus named Sid, who resided in Dunedin’s Portobello Aquarium (also in New Zealand), attempted multiple escapes. He once concealed himself in a drain for five days before being discovered, and on another occasion, he was found making a dash across the floor toward the door. After several other escape attempts, Sid was eventually released. A previous resident of Sid's tank, an octopus named Harry, had also managed an escape in a similar manner a decade earlier, only to be found halfway up the steps of the nearby University of Otago’s Marine Laboratory. “They can be very intelligent,” remarked the manager of the NZ Marine Studies Center. “Once they realize there’s an escape route, stopping them is no easy feat.”
9. They Use Weapons, Carry Portable Fortresses, and Create Barricades
Some species of octopus have been seen carrying objects like snail and clam shells, and even human trash such as old beer bottles. They use these items as mobile homes, often traveling long distances with large objects tucked under their arms as they move along the seafloor. If a predator threatens, they can swiftly retreat inside their shell home or construct a protective barrier if using two halves of coconut or clam shells. Octopuses also use these portable shelters to lay in wait for prey. Those that prefer more permanent homes often block their lair's entrance with stones, shells, and sticks. In both the wild and captivity, they have been observed spending hours searching for just the right materials to fortify their barricades.
As if octopuses weren't already fascinating enough, certain species have been seen using weapons, which makes sense when you consider their soft, squishy bodies and the fact that many sea creatures are eager to eat them. While some octopuses throw shells at one another, others take a much more extreme approach. Large female seven-arm octopuses (which can grow up to 4 meters [13 ft] long) have been observed holding egg-yolk jellyfish in their arms, letting the jellyfish’s sticky, stinging tentacles hang beneath them. Although scientists aren’t entirely sure of the octopuses' reasoning, it’s believed they first consume the nutrient-rich parts of the jellyfish and then swim along, using the tentacles for defense or even to capture additional food they might not otherwise be able to catch.
Blanket octopuses also utilize stinging tentacles as a defense mechanism, but they do so in a different way. The tiny males of the species, along with females under 7 centimeters (2.7 in) in length, have been observed using highly venomous Portuguese man o’ war tentacles as weapons. They acquire these tentacles by ripping them off the man o’ war and then attaching them to the suckers on each of their four dorsal arms.
8. They Have Extremely Strange ‘Penises’
Octopuses exhibit striking sexual dimorphism, with one of the most notable examples being the seven-arm octopus. As mentioned earlier, the female can grow up to 4 meters (13 feet), while the male typically reaches only about 30 centimeters (12 inches)! To handle this significant size difference, the tiny males develop a massive hectocotylus (a specialized arm used to deliver sperm). The hectocotylus of the male argonaut (also known as the paper nautilus) can grow up to 2 centimeters (0.8 inches) long, which may not sound like much, but it’s actually twice the length of the male’s entire body, considering the octopus itself only grows to about 1 centimeter (0.4 inches) long. The term 'hectocotylus' means 'worm of 100 suckers.' In 1829, the French naturalist Georges Cuvier discovered one of these specialized arms inside a female octopus and mistakenly identified it as a parasitic worm, which is how the appendage earned its unusual name.
At the end of the hectocotylus is a structure called the ligula, which serves to transfer spermatophores into the female’s oviduct. In some octopus species, the ligula contains erectile tissue, which swells in a similar way to mammalian copulatory organs when sexually aroused, making octopuses the only known soft-bodied animals capable of experiencing erections.
While some octopus species simply need to place their specialized arm into the female’s gill slot and leave it there for hours while depositing a sperm packet, smaller males often take a much more extreme approach. Some tiny males are required to detach their hectocotylus and give it to the female, or in other cases, the arm swims to her on its own, attaches to her body, and crawls into her mantle cavity, where she can store it until she’s ready to fertilize her eggs. Some females even store multiple hectocotyli at once, resulting in a brood fathered by multiple males.
7. Reproduction Often Leads to Death
For octopuses, reproduction is rarely a joyful affair, often ending in the death of both the male and the female. Some female octopuses have been observed strangling and then cannibalizing the male after mating. Males who manage to survive the mating process without being consumed often enter a state called senescence. During this time, they stop eating, lose weight rapidly, and their skin loses its color. White lesions appear on their bodies, which never heal. Eventually, the male loses coordination and may either be eaten by a predator or crawl onto the beach to die.
For the female, death is a more prolonged process. After finding a secure spot to lay her eggs (some species lay hundreds of thousands at once), she tirelessly guards them, cleaning and caring for them. This process can take months, and during this time, she refuses to eat, causing her body to begin digesting itself as she slowly starves to death.
One species of deep-sea octopus holds the record for the longest brooding period of any known animal on Earth. In May 2007, researchers at the Monterey Bay Aquarium Research Institute observed this octopus clinging to a rocky outcrop in the Monterey Canyon, about 1,400 meters (4,600 ft) beneath the ocean surface. Over a span of four and a half years, the researchers visited her brooding site several times, watching her grow increasingly pale and worn out while tending to her eggs. The last time they saw her was in September 2011, and when they returned after that, only the empty egg cases remained.
When the eggs finally hatch, the female uses jets of water from her gills to propel the baby octopuses into the ocean. After this, she succumbs to senescence and the effects of starvation, aimlessly swimming around until her death or being eaten.
6. They Hold a Legal Status Once Reserved Only for Vertebrates
While it may seem obvious to many that animals have some form of consciousness (albeit likely very different from ours), science has only recently caught up. In July 2012, octopuses became the first invertebrates to be acknowledged in The Cambridge Declaration on Consciousness. This document recognizes animals that possess the neurological substrates necessary for consciousness.
In 2013, cephalopods became the first invertebrates to receive legal protection under the European Union’s ‘Protection of Animals Used for Scientific Purposes’ directive. For centuries, cephalopods, especially octopuses and squid, had been subjects of extensive animal experimentation, but their welfare was largely overlooked in EU regulations. This new directive ensures the same legal protection for them that had previously been reserved only for vertebrates.
Under the new guidelines, any experimental procedure that could cause pain, suffering, distress, or lasting harm to any live cephalopod, whether adult or juvenile, must be regulated. Capturing live cephalopods in the wild must be done in a manner that avoids causing pain or distress, and once in captivity, the lighting must mimic natural conditions, including simulated dawn and dusk. Cephalopods must be monitored daily for signs of pain, suffering, or distress. General anesthesia is mandatory for all experimental procedures, and any necessary euthanasia must be carried out as humanely as possible. These regulations followed a scientific panel's conclusion that there is credible evidence of cephalopods' capacity to experience pain, suffering, distress, and lasting harm.
5. They Can Sense Early Signs of Volcanic Eruptions
To the north of Sicily lies Stromboli, a small island home to one of the world’s most active volcanoes. Mt. Stromboli erupts every 20–30 minutes and has done so for thousands of years. The surrounding marine life is constantly at risk from debris caused by the eruptions, but the octopuses living in the area always manage to avoid danger just before each eruption. Marine biologists studying their timing discovered that octopuses can detect infrasound, which is sound below the threshold of human hearing. By hearing the early signs of an impending eruption, octopuses can escape to safety before it begins. They later return to feast on the marine life that has been injured by falling rocks and debris.
For a long time, scientists believed octopuses were deaf, but recent studies show they hear so well that noise above a certain frequency can harm them, sometimes fatally. In a controlled experiment, octopuses were exposed to a pitch sweep from 50 to 400 hertz at a volume equivalent to a balloon popping. This sound was played over two hours in short bursts. Over the next four days, the test subjects were examined, and researchers found significant damage to their statocysts. The sensory epithelium showed large holes, which increased in size over time. Additionally, nerve fibers, hair cells, and plasma membranes were found to be ruptured, all due to the noise exposure.
Michel Andre, the bioacoustics expert behind the study, stated, "If the relatively low intensity, short exposure used in our study can cause such severe acoustic trauma, then the impact of continuous, high intensity noise pollution in the oceans would be considerable. For instance, we can predict that since the statocyst is responsible for balance and spatial orientation, any noise-induced damage to this structure could significantly impair the cephalopod’s ability to hunt, avoid predators, and even reproduce."
4. Their Limbs Are Truly Extraordinary
Let’s clear up a common misconception: octopuses don’t actually have tentacles. The long, flexible appendages often depicted in certain types of adult anime are, in fact, called "arms." Unlike squid and cuttlefish, which possess two tentacles alongside their eight arms, octopuses have just eight arms. While tentacles may seem similar to arms, they only have a few suckers at the tip, while an arm features suckers running the entire length. Typically, an octopus arm contains 200 to 300 suckers, with each sucker able to operate independently, or they can coordinate to feel, smell, and even taste their surroundings.
Octopus arms never get tangled, and the suckers don’t stick to the octopus itself, thanks to a self-recognition chemical secreted by the arms to aid in motor control. This remarkable ability is the first of its kind observed in nature. To explore this phenomenon further, scientists conducted a strange series of experiments where they severed some octopus arms and returned them to the animal. The severed limbs remained active for nearly an hour after being cut, but during that time, they refused to grab the octopus or any of the other severed limbs. Interestingly, the octopus would often avoid grabbing its own severed limbs with its remaining arms, although it sometimes used its beak to latch onto the exposed flesh of a severed limb, as though attempting to lick the wound. In several cases, octopuses ate the severed arms of other octopuses, but almost never their own, suggesting they can recognize their own limbs. However, when the skin was peeled off the arms, the octopus would eat them without any hesitation.
If all of that wasn’t strange enough, octopuses also have an incredible ability to regenerate lost limbs. Within just a day of amputation, the wound will almost completely close. After healing, a small bulge forms at the site, and over the following months, cells and nerves begin to develop into a perfect replica of the original limb.
3. They Possess the Most Incredible Skin in the Animal Kingdom
Octopuses are true experts in the art of disguise. The mimic octopus is capable of transforming its body to mimic the appearance of plants or other marine creatures that predators tend to avoid. Additionally, octopuses utilize their ink in a unique way, creating what is known as a pseudomorph: When threatened, an octopus ejects a stream of thick ink that stretches into the shape of its own twisted arms, confusing its attacker. As the predator is disoriented, the octopus escapes, propelling itself away using water-jet propulsion through its gills.
The most extraordinary camouflage of all, however, lies in the octopus’s skin, which can rapidly change color, pattern, and texture, perfectly blending into its environment. This remarkable skill is made possible by various mechanisms working together, enabling the octopus to vanish against rocks, plants, sand, and even more complex surfaces like coral or algae-coated rocks.
Octopuses are equipped with thousands of color-changing cells, known as chromatophores, just beneath the surface of their skin. Each chromatophore is an elastic sac filled with pigment and connected to muscles that allow the octopus to expand or contract these cells, adjusting the color of its skin. Moreover, octopuses can alter the texture of their skin to match their surroundings, creating papillae—skin protrusions that range from soft bumps to raised, plant-like spikes. These papillae are controlled by three distinct types of muscles.
Interestingly, while scientists believe octopuses are color-blind, their skin contains light-reflecting cells that allow them to mimic the colors around them, even though they cannot perceive those colors with their eyes.
Octopus skin contains light-sensitive molecules known as opsins. While the exact role of these molecules is still unclear, some scientists theorize that they enable octopuses to 'see' through their skin, facilitating rapid color and pattern changes without relying solely on input from their brains.
2. They Have the Ability to Alter Their Own Genes
Octopuses, squid, and cuttlefish—members of a cephalopod group called coleoids—possess the extraordinary ability to reprogram their genetic codes through RNA editing. In certain squid and octopus species, up to 60 percent of RNA transcripts undergo modifications through this process.
Wired provides a straightforward explanation of how this editing works:
Many cephalopods defy the usual rules of how living organisms use DNA information to create proteins. In almost every other animal, RNA serves as a faithful messenger that transmits the genetic message. However, octopuses, squid, and cuttlefish modify their own RNA, altering the instructions that are read to produce proteins.
Biophysicist Eli Eisenberg suggests that the remarkable RNA editing in cephalopods could be the key to their sophisticated behaviors and exceptional intelligence. He theorizes that this process enables cephalopods to adapt their physiological responses to factors like temperature, and claims that this is the first instance of an animal altering its own genetic code to adjust the majority of its proteins, thus facilitating real-time adjustments to its environment.
One theory is that some coleoid species may have traded the advantages of frequent DNA mutation (as seen in traditional evolution) for extensive RNA editing. Kazuko Nishikura, a professor at a biomedical institute in Philadelphia, describes the potential of coleoids using RNA editing to manipulate their nervous systems as 'extraordinary.' She adds, 'We may discover much from the brains of squid and octopuses.'
1. Their Brains Are Truly Extraordinary
'This is probably the closest we will come to meeting an intelligent alien.' — Peter Godfrey-Smith, *Other Minds*.
Octopuses are renowned for their intelligence, as they can solve puzzles, open childproof containers, recognize symbols, and learn from observation. They even show the ability to identify individual humans and express their likes or dislikes toward them. However, the true uniqueness of their brains goes far beyond these remarkable but more commonly known skills.
While the claim that octopuses have nine brains is technically inaccurate, neuroscientists have identified three main parts of the octopus brain, containing over 500 million neurons. The central brain, encircling the esophagus, holds about 50 million neurons. Another 80 million neurons are located in the large optic lobes behind the eyes. The remaining neurons are distributed in clusters known as ganglia. Each of the octopus’s eight arms has its own ganglion, controlling complex movements locally. While the central brain sends commands, the ganglia in each arm independently execute the necessary actions, allowing each arm to function as though it has its own mind.
