Can An Octopus Regrow An Arm?

Octopuses = food for a lot of animals in the ocean, and that’s one of the reasons they have so many awesome strategies for defending themselves. From their ability to change color to their ability to drop an arm in a pinch, an octopus has quite the list of options to choose from when it needs to make a quick escape. But does dropping an arm mean spending the rest of its life as a septopus?! Continue to read to find the answer to your question: Can an octopus regrow an arm?

Octopus arm growing back via Dr. Chelsea Bennice

What’s arm regeneration?

An octopus that loses an arm is not doomed to stay a septopus, because its arm will regenerate! But, first things first. Why might an octopus lose an arm, to begin with?

If a predator, such as a shark, grabs an octopus’s arm, the octopus can shed its limb and swim away (mostly) intact. Octopuses share this ability to drop limbs, called autotomy, with some sea stars, lizards, and amphibians, among other animals.

Once it sheds an arm, the octopus’s body gets to work building a new one. Cells called hemocytes flood the place where the arm was lost, and then regenerating fibers start growing into what will become a brand-new, fully functioning arm! 

This study took a close look at the process of arm regeneration in a Common Octopus (Octopus vulgaris).

Three days after the loss of its arm, the octopus in the study had a little knob where its old arm was lost. After 11 days, there was a “protrusion”, and after 17 days, a little hook-like thing appeared at the end of it.

After 55 days, scientists could spot a tiny version of the arm, and then after 130 days, a new, complete arm had regrown!

🐙 Octopus Fun Fact

All eight of an octopus’s appendages are arms, not tentacles, and there IS a difference! One of the biggest differences is that arms are lined by suckers, while tentacles usually have suckers just at the ends.

underside of octopus arms deposit photos

But what about the nervous system?

Of course, an octopus arm is not just an arm … it’s like a mini-brain and an arm all wrapped up in one sucker-lined package. An octopus’s arms are packed with neurons. When an octopus regenerates a lost arm, it rebuilds its nervous system as well.

🐙 Octopus Fun Fact

Octopus arms can make decisions, thanks to an octopus’s unique “bottom-up” decision-making process, which is quite different from humans’ “brain-down” method of making decisions.

Perhaps it’s not surprising, then, to learn that a severed octopus arm continues to move around after it’s disconnected from the animal’s central brain. The severed arm may even continue to look for food

Now you know the ARMazing truth

Lose an arm, grow an arm—if you’re an octopus, limb regeneration is a normal part of life! If you enjoyed this post, check out our in-depth blog on octopus arms!

If you want to educate yourself some more about all sorts of different cephalopods, take a look at our encyclopedia. Or, what we call it, our Octopedia!

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