Outstanding Octopus Facts: The Blanket Octopus

When most people think about octopuses, they generally picture a Pacific Giant, or something smaller, like a two-spot octopus. What people don’t realize is that there are swimming in the oceans and some don’t fit the standard image. The blanket octopus is the perfect octopus.

On paper, the blanket octopus seems like a perfectly ordinary octopus. They live in the ocean where they favor waters. They eat crabs and oysters and other things that most octopus dine on. They’re a solitary animal. They have eight arms that they use for a variety of tasks. They’re clever. The males die after mating and the females die almost as soon as their eggs hatch.

That’s on paper. One look at a blanket octopus and it quickly become apparent that this is anything but a normal.

The first thing that makes the blanket octopus unusual is that instead of sticking to the sea bed and remaining in a relatively localized area, blanket octopus prefer to float out on the open waters, this makes sightings of them very unusual since they rarely come into contact with divers.

Another thing that sets the blanket octopus apart from her fellow octopuses is that while she does have eight arms, membrane connects her . The webbing serves a few different purposes. When she wants to look bigger, she unfurls it with the hope that the sudden change in her appearance intimidates anything that’s thinking about snacking on her.

When unfurling her blanket doesn’t do the trick, she’ll disconnect part of it, letting it drift on the current, distracting the predator that’s stalking her so that she can make a hasty get away, or the predator becomes entangled in the webbing, which not only allows the blanket octopus to escape their clutches, but to also explore the possibility of making the animal that wanted to eat her, into it’s very own dinner.

What is a Blanket Octopus?

The term blanket octopus is actually the common name for a group of octopuses that bear the formal name, termoctopus, which contains four different species. They are:

  • Common blanket octopus (T. violaceus) AKA violet blanket octopus
  • Gelatinous blanket octopus (T. gelatus)
  • Palmate octopus (T. gracilis)
  • T. robsoni

What makes blanket octopuses stand out is that between their dorsal and dorsolateral tentacles is webbing that connects the two tentacles together. The other interesting thing about these tentacles is that while other species have tentacles that are uniform in length (unless the animal has lost one in an accident and is in the process of regrowing it.)

What’s the “Blanket” for?

It’s impossible to say exactly why blanket octopuses developed the webbing, but there’s no getting around the fact that they put it to good use.

The first thing the blanket octopus does is unfurl her webbing whenever she needs to look bigger, something that most commonly happens when there’s a large, hungry predator in the vicinity. And if that predator isn’t intimidated by her newly improved size, she’ll detach a part of the webbing, using it as a kind of decoy, creating a moment of confusion that allows her to slip away to somewhere safer.

Battling Portuguese Man O’ Wars

As a rule, most sea animals give any Portuguese Man O’ War they come across a wide berth. The last thing they want to do is come into contact with any of it’s long, trailing tentacles which pack a poisonous punch. The blanket octopus is the exception to the rule. Not only is she immune to it’s sting, but she has the skills needed to steal some of the deadly tentacles and use them as a weapon. Since the poison stays viable for a long time after it’s been removed from the Portuguese Man O’ War, the blanket octopus’s choice is good. She can use the tentacle to either defend herself from other predators or to help shock and kill prey.

Dimorphism in Blanket Octopus

Taken at face value, the blanket octopus is a remarkable creature, but science really discovered something that makes it even more … bizarre. Researchers were startled when they discovered that what they’d always assumed were two different species was actually the same species of blanket octopus. But you have to forgive them for their error. It’s easy to understand how they managed to make the mistake.

You see, female blanket octopus are huge. As an adult, they’re about 6 feet in size. The males are a whole different story. They’re smaller. A lot smaller. The average size of the full grown male blanket octopus is about 0.9 inches long. That’s about a 40,000 times size difference. No one understands why the two sexes are so radically different, but we do know that it’s the most extreme case of sexual dimorphism ever to have been discovered in nature.

If blanket octopus mated the same way most mammals do, the size difference would cause some serious issues. But they don’t.

When it’s time to mate, the male breaks off his third arm and gives it to the female who saves it until she’s ready to fertilize her eggs. For both octopus, it’s a fatal relationship. The male dies almost immediately after detaching his arm. The female lives long enough to care for her eggs and than she passes away.

bermudabiology “Blanket Octopus and Portuguese Man O War.” Bermuda Biology. Web. Accessed 3 November 2017. https://bermudabiology.wordpress.com/2015/04/22/blanket-octopus-and-portuguese-man-o-war/

Pickerell, John. “Walnut-Size Male Octopus Seen Alive for the First Time.” National Geographic. 12 February 2003 Web. https://news.nationalgeographic.com/news/2003/02/0212_030212_walnutoctopus.html



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