Arms! Tentacles! What’s the difference? Which cephalopod has what!? When it comes to cephalopod appendages, especially octopus, tentacles seem to be that all-encompassing umbrella term that gets used when describing those long, flexible appendages. We are here to answer the ultimate question: Does an octopus have arms or tentacles? Let’s break it down!
Okay, let’s cut straight to the chase.
Does an octopus have arms or tentacles? Time for the big reveal of who has what!
- Octopuses have 8 arms and no tentacles
- Cuttlefishes have 8 arms and 2 tentacles
- Squids have 8 arms and 2 tentacles
- Nautiluses have no arms and around 90 suckerless tentacles
Yup, now it’s out there!
Having 8 arms, octopuses can be referred to as octopods while cuttlefishes and squids, having a total of 10 arms, are referred to as decapods.
How do cephalopods arms and tentacles function?
Arms and tentacles are boneless limbs composed of muscles, nerves, and a skin layer to cover it all.
Cephalopod arms and tentacles have a nerve cord running through the center surrounded by 4 types of muscle!
Instead of having the support of a skeletal bone structure like we do, cephalopods rely on muscular hydrostats to keep them in tip-top cephalopod form.
A muscular hydrostat is made up of densely packed muscle groups that are arranged in a cylinder-like structure. This allows the arm or tentacle to bend, elongate, shorten, twist, and stiffen.
Sounds complicated… Think of arms and tentacles like your own tongue!
It’s mostly muscles that make licking an ice cream cone possible. With no bones in the way, the arms and tentacles can move in any direction and have nearly unlimited degrees of freedom.
🐙 Octopus Fun Fact
Along with the human tongue, elephant trunks, leeches, and most worms all have a muscular hydrostat system!
Guess how much this octopus weighs (Answer tomorrow!) 🎥: RoneyDivesA young giant pacific octopus was brought to Shaw Centre for the Salish Sea for care this summer at only 5lbs/2.27kg – it’s set to be released after 6 months on December 15th!🤯🐙 Giant Pacific Octopus facts!🐙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!🐙 Giant pacific octopus have about 280 suckers per arm (~2,240 suckers total)🐙 Not only can an octopus see you…they can recognize who you are! A research study on Giant Pacific Octopuses at the Seattle Aquarium showed that their behavior, breathing, and colors changed depending on whose face they recognized.🐙 While most warm water species live 12-18 months, the Giant pacific octopus lives 3-5 years in cooler water 42.8–53.6 °F (6–12 °C)🐙 Some cephalopods increase their weight from less than an ounce to 11-22 lb in 6-12 months! To put this into perspective, it takes humans 24 months to grow this large! Giant Pacific octopuses can consume 2–4% and gain 1–2% of their body weight each day!🐙 Average weight of a giant pacific is 90lbs / 40.8kg – the largest authenticated weight was 156lbs/70.7kg.Where are our giant pacific octopus fans at?🥰🐙🥰OH HEY New Members! We LOVE that you're here!Make sure you grab your octopus activity guide/ coloring book at [www.OctopusFun.com](http://www.octopusfun.com/?fbclid=IwAR2oyXpAWKW-lJ3AkmVkZUjPkctGHMfTvbNuZYxOSm6i_QndrXTzbpWfjbU) !Here are some quick questions for you as ya get settled in…1) Where in the world are you joining us from?2) When did your fascination for octopus begin?3) Feel free to share your favorite octopus photos/art down below4) Have any friends who share your love for octopus? Feel free to invite them! They won't be automatically added to the group– it'll ask them if they're interested in checking us out!Chat soon Nation!Without further ado, here are the new members!Luke Johnson,Sean Fong Tze Hin,JoWee Adams,Rodrigo López,Miranda Fox,Marlena Theresa,Gina Amatucci,Lauri Malmquist,Ekaterina Petrova,Aniko Kovacs,Javier Cruz,Chrysti Ramirez,Jessie Wolff,Aurora Chung Kurland,Ling Ding,Mariangela Rodriguez,Ayzak Zauren,Harriet Davies,Christine Mongelli,Matt Wittich,Shea Carpenter,Heather Myna,Gonzalo Alonso,Vera Elumn,Debra Jones Lambert,Bjorn Angelica,Sarah Mills,Jody Scott-Grindheim,Alexis Fink,Darrian Phillips,Amanda Corvus,Alejandro Vanegas,Darija Ilic,Suzanne Culp Raygan,Sebastian Ossa Saldarriaga,Andrew Kushner,Valentina Bruno,Diana McCoy,Christian,Fish Nuggets,Darla Featherston,Katz Odland,Manon Sander,Rebekah Todd,Igor Diamandi,Christina Staats Ricker,Daniela Gracia,Heather-Jean Nelson,Elmi Hassanmal,Jovi Nothanks,Charlie Rutan,Joe Dietz,Kalie Simnitt,Mia Zanoni,שלומית אורשינא קניגסברג,Emily Vail,Junior Salientes,Kathy Dowdall,Victoria Schmidt,Robin Rains Galascione,Cristian Alexander Kohn,Leona Kelly,Regina Bahr,Denny Horner,Vee Zarate,Krizler C Tanalgo,Linda Lewis,Clau Blackwork,Mauricio EcoVeg Zamora,Joni Tanskanen,Thomas Ohene Effah Journals,Dawid Bechcicki,Gennesaret Sikl,Tasos Moumoulidis,Jarred T Davis,Robert Rymarczuk,Sara Alcaraz,Krissy Watts,Fiona Hulme,Christa Patton,Diana Gonzalez,Marla Savoie,Carol Groom Woodson,John Connolly,Katelyn Vipperman,Emily Yacoub,Sue Austin,Robert Schmidt,Leslie FJ,Patrick Rivers,Ben Boyce,MayDay Myers,Paula Mallory,Lately Lisa,John Atwell,Erick Flores,Салтанат Сагадиевна Болатбаева,Devon Frala,Eric Bowman,Peter James,Laura Chasowy,Nancy Chun,Janice Ng,İbrahim Ertuğrul,Denise Charneski,Ed Perez,Karen Barry,Susan Corlies,Martins Walters,Laura Shirley,Angel Ore,Victoria Gillotti,Claudel Roy
Posted by Octonation – The Largest Octopus Fan Club on Tuesday, December 15, 2020See AlsoWhat's the difference between arms and tentacles?Ten Wild Facts About Octopuses: They Have Three Hearts, Big Brains and Blue Blood
Nerves play a BIG role in cephalopod arms as well!
Each sucker is surrounded by a nerve ring, connected to a bundle of nerves, which in turn is connected to the main nerve cord in each arm.
With many satellite or mini-brains, cephalopods are able to process certain information from its arm without consulting the main (central) brain. Like if you were watching TV, your hand could search for the remote or grab the popcorn without you even having to think about it!
What’s the difference between an octopus arm and a tentacle?
The biggest difference between arms and tentacles is their sucker placement!
In general, octopus arms have suckers along the entire length with most octopuses having two rows of suckers running down their arms.
Unless of course, you’re the fabulous and unique Glass Octopus who only has one row of widely spaced suckers for each arm that look like cute little dollops of whipped cream.
By contrast, tentacles are smooth with no or reduced suckers and have a wider end (aka distal club) full of suckers. In some species, these suckers have tiny hooks inside them, helping cuttlefish and squid latch onto their prey.
The exception to this is the Nautilus, which has 90 suckerless tentacles with adhesive ridges to help them trap and secure food.
The Chambered Nautilus: A Living Link With the PastThe noble nautilus has a knack for navigating at night—a superb sense of smell serves this seafarer well as the only cephalopod still surviving with a shell!
Posted by Monterey Bay Aquarium on Sunday, October 9, 2016
🐙 Octopus Fun Fact
Suckers on octopus arms are way more sensitive than those at the end of a squid tentacle. Octopus suckers have 10,000 chemotactile receptors vs. only around 100 on each tentacle sucker.
Check out this blog post and learn everything there is to know about octopus suckers!
What does an octopus use their arms for?
If you think about each of these cephalopod’s lifestyles, their arm/tentacle configuration starts to make perfect sense.
Many octopuses live on reefs where they use their 8 arms to:
- Crawl around
- Hang on surfaces
- Search the many nooks and crannies for prey!
Octopus use their arms for:
- Grasping
- Movement
- Grooming
- Defense
- Mating
- Chemo-sensing
- Tactile sensing
- Throwing things at one another when they get annoyed
On the other hand, squid and cuttlefish spend much of their time suspended in the water column and use their tentacles primarily for hunting.
Since squids love a delicious shrimp dinner, they need to be quick if they have any chance of catching them. They will strike prey with tentacles that can elongate up to 80% of their original length in a matter of milliseconds.
Once caught, their tentacles retract and their arms take over for prey handling.
🐙 Octopus Fun Fact
The Vampire Squid has 8 arms and 2 highly modified tentacles. Instead of the status quo tentacles, they have two thin, retractable sensory filaments lined with hair-like structures, which they use to feel out their surroundings.
Super handy to have a highly sensitive fishing line that can sense food or danger when you live in the black depth of the ocean!
They can regenerate?!?
Cephalopods rejoice!
Both arms AND tentacles can completely regenerate in a matter of months!
The regeneration time frame depends on multiple things including:
A study on tentacle regeneration in the Common Cuttlefish (Sepia officinalis) showed that their regeneration process is the same as that in an arm; however, the sucker regrowth is delayed.
While injuries to arms and tentacles can occur, cephalopods can also voluntarily “drop” an appendage. This is known as autotomy.
It’s common for some species of male cephalopods, like the Dumbo Octopus and Blanket Octopus, to break off their specialized mating arm (hectocotylus) and give it to the female when they mate.
The Deep Sea Squid (Octopoteuthis deletron) takes this nifty trick to a whole new level with “attack autotomy”.
It has bioluminescent arms, which can break off and continue to wiggle as they float away. This keeps a predator distracted while the squid slinks away unscathed.
Turns out these glowing arm parts can also stay attached to their attacker!
Squid discovered in 2005 with a unique skill!This Squid's superpower is using the tips of it's tentacles to mimic the appearece of a small harmless squid! ➡️ Monterey Bay Aquarium Research Institute (MBARI)’s footage of deep-sea squid has revealed a crazy hunting process: Instead of trapping prey with suckered-tentacles like most squid, This species seems to lure prey by mimicking a smaller version of itself with a sucker-free tentacle that ‘swims’ around as bait. 🤯When it’s finished & ready to move – it retracts and pulls the lure tentacle towards its body. Grimalditeuthis bonpland is a squid named after the Grimaldi family. Prince Albert I was an amateur teuthologist who pioneered the study of deep sea squids by collecting what he called the 'precious regurgitations' (read: squid & other deep sea animals) of sperm whalesDid you know this species existed??!!! 🤯🦑🤓 (Species name: Grimalditeuthis bonpland)🎶: global genius productions – when I look back
Posted by Octonation – The Largest Octopus Fan Club on Wednesday, September 16, 2020
Unlike octopus arms, which have a specific “break” point, these squids can break off their arms just above where they are grabbed. This saves as much of their arm as possible with less arm to regrow ultimately saving them precious regrowth energy.
So, does an octopus have arms or tentacles? Finally answered!
And there you have it! Consider yourself well versed in tentacles and arms which belong to the appropriate cephalopod…at least for now.
Considering the ocean is less explored than the moon, I wouldn’t be surprised if somewhere out there lurks a 3 armed, 10 tentacled octopus or a 10 armed, no tentacled squid just waiting to be discovered throwing everything we know to be true right out the window.
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 theOctoNation Facebook group, OctopusFanClub.com! Make sure to follow us onFacebookandInstagramto keep up to date with the conservation, education, and ongoing research of cephalopods.
More Posts To Read:
- Do Octopus Bite?
- Does Octlantis Exist?
- “How The Octopus Lost Its Shell” (Octopus Comic)
- What’s The Difference Between Cuttlefish vs. Octopus?
- Breaking News – There are now THREE new species of Nautilus!
Corinne Klein
Corinne is a biologist with 10 years of experience in the fields of marine and wildlife biology. She has a Master’s degree in marine science from the University of Auckland and throughout her career has worked on multiple international marine conservation projects as an environmental consultant. She is an avid scuba diver, underwater photographer, and loves to share random facts about sea creatures with anyone who will listen. Based in Japan, Corinne currently works in medical research and scientific freelance writing!
