Here’s Everything You Need To Know About Octopus Arms

From being able to regenerate an entirely new arm in just 2-4 months to having mini-brains in each arm to being able to smell, taste, and sense light, octopus arms are just one more topic we can all geek out about! With arms making up most of an octopus’s body and being useful for just about everything, it’s time we take a good look at what these eight arms are truly capable of.

Ocean Octopus GIF by OctoNation - Find & Share on GIPHY

Does an octopus have arms or tentacles?

So… which one is it?

When it comes to the cephalopod community, these words tend to get thrown around and used interchangeably. 

Let us set the record straight here and now: Octopuses have 8 ARMS and ZERO tentacles

This is not the case for all cephalopods, but when you’re talking about an octopus specifically, the word tentacles should not be uttered on your lips. Octopuses have 8 arms, which have suckers along the entire appendage, with most species having two rows per arm. 

What’s the difference?

Octopus arms are thicker near the base, getting smaller and eventually tapering off at the ends. Arms differ from tentacles, which only have suckers at the end! 

Maori Octopus By: Matt Testoni

What does an octopus do with its arms?

Arms and suckers make up most of an octopus’s squishy body and are extremely important body parts. Arms and their suckers are used for:

  • Movement
  • Pushing
  • Pulling
  • Grasping
  • Camouflage
  • Mimicry
  • Fighting
  • Mating
  • Capturing prey
  • And, tasting! 

They are extremely muscular AND flexible with no rigid bones restricting their movements.

When it comes down to it, octopuses are a really smart ball of muscles and neurons.   

Maori Octopus By: Matt Testoni

Are all octopus arms the same size and length?

While octopuses across the oceans are living their best octo-armed life (see what I did there 😉), arm lengths and sizes vary greatly between species. 

Our mighty Giant Pacific Octopus arm spans (from arm tip to arm tip) can be up to 16 feet (4.9 meters) – that’s about the length of an average car! 

The adorable Banded String-Arm Octopus (Ameloctopus litoralis) has exceptionally long arms that are 10x its body length! 

The 7-Armed Octopus (Haliphron atlanticus) is there to throw everything into chaos. More on this species later and how it gets its name.  

How many suckers are on each arm?

Each of these incredible arms has 280 suckers per arm (~2,240 suckers total)

Note: Check out this blog post and learn everything there is to know about octopus suckers! 

Close up of Octopus Suckers

Here’s everything you need to know about octopus arms 

With so many of you asking us questions on our Facebook and Instagram posts, we wanted to share some more fun facts about the octopus arms and everything they can do! 

Did you know octopuses can regenerate their arms?

*Spoiler Alert* Remember in ‘My Octopus Teacher’ when our beloved main character, the Common Octopus, got her arm bitten off by a shark? She retreated away for a couple of months, but then popped back on the scene with all 8 arms.

That’s all thanks to the amazing power of regeneration

When an octopus sustains an arm wound, they don’t get a scab or scar as we would. Instead, a layer of cells called epithelium (the same cells that make up our skin layer) covers the wound and beneath this, the regeneration process begins.

A study reported that the first sign of regeneration came in the form of a tiny knob on the arm edge, 3 days after injury. After 11 days, they observed a protrusion which turned into a hook-like structure by day 17. By day 55, a complete structure (mini arm) was visible and by day 130, the new arm tip had fully regenerated. 

Presto- A brand spanking new arm complete with suckers and chromatophores!

🐙 Octopus Fun Fact

Getting wounded is not the only reason an octopus might need their regeneration superpowers. 

The Banded String-Arm Octopus is missing an ink sac; so to get away from or confuse predators, they will “drop” one of their arms. This arm will wiggle around for up to 5 hours as if to say “come eat me!” 

Scientists call this defense tactic “arm dropping” and they’ve come across some String-Armed Octopuses managing just fine with only 2 arms! 

This species can regenerate their arms in a quick 6-8 weeks.

Octopuses have a decentralized nervous system with 2/3 of their neurons are located in their arms— I always imagined that a young octopus had to get acclimated to being pulled various directions by it's arms being that octopus arms can make decisions without having to consult with the main brain. Imagine being on the couch 🛋 and telling your arm go find the remote because you’re trying to concentrate on your show. I came acorss this video by Lawrence Scheele that showed a banded string arm octopus seemingly being pulled in various directions— also you can see this lil’octo is regrowing back two arms lost in a fight. I love octopuses so much! Endlessly fascinating. 🤩🥰🤩

Posted by Warren K Carlyle IV on Tuesday, September 17, 2019
By: Lawrence Scheele

Those are some brainy arms! 

An octopus has 500 million neurons, but more than half are found OUTSIDE the main, central brain. 

Where do they keep these other neurons that amount to 60% of their brainpower? They are clustered in each of their arms!

Each arm essentially has its own mini-brain. These satellite brains can communicate with one another without needing to report back to the central brain. 

Maori Octopus By: Matt Testoni

Could you imagine fixing yourself a meal and completing a puzzle all while not having to take your eyes off the TV?

Behavioral neuroscientist Dominic Sivitilli explains it like this…

“The octopus’ arms have a neural ring that bypasses the brain, so the arms can send information to each other without the brain being aware of it. So while the brain isn’t quite sure where the arms are in space, the arms know where each other are and this allows the arms to coordinate during actions like crawling.”

If arms are moving together, the big brain is at work making that happen. One arm doing its own thing looks like it has a mind of its own because it literally has a mind of its own!

On the hunt for more food

The Shallow Water Octopus is often observed poking their arms into holes and crevices to look for food along the reefs they inhabit. This is called “speculative bottom searching” where they will snake their arms out searching every nook and cranny for food. 

Get Off Me GIF by OctoNation® The Largest Octopus Fan Club! - Find & Share on GIPHY

Having brains in each arm means that octopuses can successfully hunt in areas that they cannot see. Like Tesla has self-driving cars, these octopus arms come programmed to search for snacks! 

Pair this with their sucker’s ability to taste and smell what they touch and it starts to make sense why two-thirds of an octopus’ brainpower is located in their arms. 

🐙 Octopus Fun Fact

They can sense light with their arms! A study showed that when the light was shined on an octopus’s arm (without the octopus being able to see its arm), it would pull away 84% of the time.

This unique octopus has a special super power!

What did you find most Interesting about this species? 🎥: snorkeldownunderUpon further Inspection, it appears the spaghetti monster is in fact, adorable! hahaThe Banded String-arm Octopus (Ameloctopus litoralis) uses its exceptionally long arms (10x its body length – 30cm) to look for snacks in the in­ter­tidal sand, mud or reef flats in the muddy coastal wa­ters.⁣What It's doing now is called “speculative bottom searching” This is where a string-arm octopus will snake their arms out and the suckers & arms will autonomously search every nook and cranny for food!Yup, like Tesla has self driving cars – these stringy arms come programmed to search for snackz! 🧠Oh and get this…The string-armed octopus has a pretty unique super power —unlike other octopus species, they don’t have an ink sak to blast predators with ink while they make a gettaway!They will instead detach their spaghetti thin arms to confuse predators as they make their getaway.This ‘dropped’ arm or predator bait will wiggle around for up to 5 hours as if to say "come eat me!" Scientists call this defense tactic – "arm dropping" & they’ve come across some string-armed octopuses managing just fine with only 2 arms! (Arms can regenerate in 6-8 weeks)🚨 If ya read this far, what did you find the most interesting!? Also if you’ve gotta better nickname for the banded string arm, we’d like to hear it!🤯To us— the fact that their mantle is so spaghetti like is pretty wild considering it constrains all their squishy vulnerable organs (hearts, stomach, gills, etc)

Posted by Octonation – The Largest Octopus Fan Club on Sunday, December 5, 2021
By: Lawrence Scheele

Octopus mating arm: Is that a real thing? 

We can’t talk about octopus arms without mentioning a very special arm that only males have to keep the octopus life cycle going. The hectocotylus

This arm is specialized with grooves to store sperm, ready to transfer it to the female when mating. When it’s go-time, the male will insert his hectocotylus into the female’s mantle and deposit his spermatophore (sperm packets). 

Remember the 7-Armed Octopus? The third right arm of males is hectocotylized- the arm develops in an inconspicuous pouch under their right eye giving males the appearance of only having seven arms. 

This octopus won’t just deposit his sperm, he will break off his mating arm and give it to the female so she can fertilize her eggs.

Which fact surprises you the most? 📸: MBARI1️⃣ Seven-arm octopuses are one of the two largest, if not the largest, known species of octopus. Can you picture this octopus growing up to 11 feet (3.5m) and weighing in at 165 pounds (75kg) — UM…WHAT? 🤯2️⃣ The 7-Arm #Octopus actually has 8 arms (surprise) But the male takes extra care in protecting his eighth arm — the mating arm, used to deliver sperm to a female. Wildly enough, this special arm develops in an inconspicuous sack/pouch under their right eye. A small male will drift along until he meets a giant female, up to 20 times bigger than he is. Then he’ll break off his mating arm and give it to her so she can fertilize her eggs!3️⃣ The life span of 7-arm octopuses remains unknown at this time, however, it may have a relatively long life span to reach its large size (for instance giant octopuses live 3 to 5 years!)4️⃣ In 30 years the Monterey Bay Aquarium deepwater research submersible has only seen this species five times total! 5️⃣ Their depth range is thought to be between 0 m and 6,787 m (4.22 miles deep!) Yup…just casually hanging hanging out from freezing to warm water temperatures ❄️🐙🔥 6️⃣ They’re in the same family as the blanket octopus (Argonautoidea) remember how the blanket octopus uses the stinging tentacles of the man-o-war like nunchucks against predators? Well guess what— the 7 arm octo does the same!7️⃣ The 7-arm Octopus participates in the largest migration on earth in biomass and number of animals participating. It is called diel vertical migration and it’s an upwards migration in the evening and a downwards migration in the morning. We think they might come up during the night to get snacks & go back down during the evening to avoid predators!If ya read this far comment 🐙🤓 & let us know if ya learned anything 🧠 🏷 #science #nature #biology #marinelife #redsea #egypt #stonefish #octopuses #cephalopods #reef #underwater #diving #oceanconservation #sea #biodiversity #marinebiology #ocean #animals #fish #octopus #natgeo #nationalgeographic #natgeoyourshot #STEM #scuba #scubadiving #underwaterphotography #myoctopusteacher

Posted by Octonation – The Largest Octopus Fan Club on Thursday, September 2, 2021
7-Armed Octopus By: Monterey Bay Aquarium Research Institute

The Blanket Octopus and the Dumbo Octopus do this too! 

Being a deep-sea octopus and not knowing when they might come across a male, the female octopuses will hoard the hectocotylus using the sperm from their collected male arms when they see fit and making sure they are good for making babies.

Octopus Arms: Stop Squidding Around!

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!

Connect with other octopus lovers via the OctoNation Facebook group, OctopusFanClub.com! Make sure to follow us on Facebook and Instagram to keep up to date with the conservation, education, and ongoing research of cephalopods.

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