What has 3 hearts, moves through jet propulsion, can morph into a new shape, change colour in less than a second, and is regarded as one of the most intelligent creatures out there? If you’re guessing some sort of super hero, I would argue that you are correct. More scientifically, however, the answer is one of the 600+ species of octopus found in oceans around the world.
First, let’s address the question I get asked more often than any others. The plural is octopi, right? Well, kind of, but not really. The word octopus is often assumed to be of Latin origin, of which words are made plural by changing the us ending to an i – octopi. However, the word actually stems from the Greek ὀκτώπους (oktṓpous) meaning “eight footed”. The Greek plural would then be octopodes. However, since the word octopus has long been an English word, it is pluralized by English standards with an es, so octopuses is the grammatically correct plural. Ultimately though, we English speakers aren’t so fussed by things like rules and standards, so you can use any of the above and be considered technically correct in most circles.
Ok, now that that’s sorted. The animals we call octopuses belong to the order Octopoda. From there they are divided into two groups, the Cirriata, or finned, deep sea octopuses and the Incirriata which have no or almost no remneants of hard shell left from their molluskan heritage. Within the Incirrata are the Octopodidae family and Octopus genus which contains about 300 species of the most familiar octopus we commonly think of.
Within the genus Octopus, there is great variation, but some characteristics remain constant. All octopus have 3 hearts: 1 primary that pumps blood to the visceral organs and 2 brachial (or gill) hearts. Each brachial heart pumps blood across its adjacent gill to exchange the maximum amount of oxygen into the blood. The quick transfer of oxygenated blood makes them able to perform great bursts of speed. Though generally, they crawl over the bottom of the sea at a leisurely pace, when necessary they can take a large amount of water into their mantles (body area above the legs) and squeeze it out a much smaller siphon to create a jet propulsion effect that can get them out of harm’s way in the blink of an eye.
Octopus, like all cephalopods, have fantastic vision. Their eyes are actually better than ours! They can see polarized light and light from a broader spectrum than we humans can. Some species even use infrared light to communicate with each other. However, some species are colour blind. This is especially amazing considering how vast their ability to quickly camouflage is.
Octopus can instantly change themselves to blend into their surroundings, including their body shape and skin texture. Different species have differing abilities of camouflage potential, but those who live in complex, diverse environments tend to be better masters of disguise than those living in more visually monotonous areas. They use three different colour changing cells to do this: chromatophores, iridiphores, and leucophores. Chromatophores are pigment filled cells that are surrounded by a circular network of muscles and neurons to expand and contract the desired colour at will. Iridiphores are of similar structure, but they reflect light, making them iridescent and metallic looking. Leucophores are flattened, branched cells that scatter incoming light, generally appearing white, but since they reflect the predominant wavelength of light, could also appear blue or red in those lights, helping the octopus blend in under any light conditions.
Like most cephalopods, octopuses are semelparous, meaning they only reproduce once in their life before dying. The male delivers sperm packets called spermatophores to the female by placing his specially adapted third right arm (hectocotylus) into her mantle. The hectocotylus lacks suckers on the lower portion of the arm, instead having a kid of coin-purse shaped end to hold the spermatophores. Depending on the species, the male may have to go through a complex mating ritual before being allowed to transfer his genetic material over. After all, this is the only mating the female will do, so she has to choose the genetic partner of her offspring wisely.
Maybe generations of picky mating are why octopuses are generally regarded for their wisdom, or at least their intelligence. Nearly everyone has heard some urban legend of an octopus in an aquarium, breaking out and getting up to some mischief and finding their way back into the correct aquarium all before they can be discovered. You’ve probably also heard stories of octopus hassling divers. Like the octopus who watches a diver use his knife and takes note of where it was, only to surprise him one dive by taking the knife out of its sheath and playing with it. Or the octopus that steals a diver’s underwater camera and swims off with it.
They are sneaky little critters, but people are also trying to harness their creativity. There’s an octopus in Tacoma that paints from his aquarium. Additionally, there are thousands studies showing the capacity of octopus to learn and remember specific tasks or stimuli, which is higher than any other invertebrate and even higher than some vertebrates. Octopuses use tools, plan out tasks, and can be excellent mimics of other animal’s behaviour. They are fascinating and curious animals who we have so much more to learn from.
Octopuses are always a highlight of a dive because of their charismatic nature and big, watchful eyes. They have so many qualities to make them a favourite amongst land and sea lovers alike. Make a new octopus friend on your next dive, but don’t take it personally when you can’t find him/her again. They are probably watching you from the shadows, and judging you.
‘Essential Octopus Facts’ was written by Roya
Related Article from Dive Compare: Mimicry and Camouflage