For those of you that have seen Finding Dory I’m sure you’re all gushing about how
awesome Hank the octopus is, he can camouflage like a champion and he helps to rescue Dory and return her to the ocean. He does at one point though call himself a “septopus”, which is an octopus with seven arms, because he lost one a long time ago. I’m sorry to tell you that Hank was wrong, yes an octopus can lose an arm but they have a wondrous ability to also be able to grow it back. Somewhat like a sea star except that the missing arm won’t grow a whole new octopus.
Since watching the film I decided to do some googling on septopuses to confirm my understanding that they don’t really exist and in my searching I found out about a weird, little octopus called the Seven-Arm octopus, Haliphron atlanticus, a real life septopus!
But again through further digging this idea was busted too. The Seven-Arm Octopus only appears to have seven arms; it does in fact have eight. One of their arms is reduced to just being a type of sac hidden under the eye so that it is not easily visible and the animal looks like a septopus. And this phenomenon only happens in the males of the species, the girls have their full eight arms on display. This reduced arm is called a hectocotylus which is a specially modified arm that males use for mating. The male actually detaches his hectocotylus during mating and the female takes it so he does end up as a septopus.
This octopus species wasn’t found until 2002 when it was accidently caught off New Zealand by a fishing trawler. It is one of the largest species of octopus measuring up to 3.5m in total length and 75kg. Not much is known about this massive species. The seven-armed octopus lives far from shore, in deep waters.