On a recent expedition to explore the seamounts in the southern Indian Ocean by scientists, a new species of large squid was discovered. A specimen of the new species, which can grow up to 30 inches long, belongs to the deep-sea Chiroteuthid family, which are known for being radically bioluminescent (naturally glowing.) Don’t confuse this squid with the squidworm, a creature also just discovered that is so unusual that it requires a brand new genus.
This lovely squid find sparked a common question regarding squids and octopi (or octopuses, both plural forms are correct.) How do the two marine creatures differ?
Both tentacled types have a ton in common. They both live in salt water and are related to snails. They both move by jet propulsion and have hard beaks that are used to rip away the flesh of their prey. Neither animal produces poison that can harm humans. (The blue ringed octopus is an exception.) Expelling ink is a shared defense against predators.
And both creatures, amazingly, have blue blood.
(Speaking of blood and the ocean, researchers also recently announced the discovery of a critter called the “Dracula fish.” Learn the reason behind the grim name, here.)
While both species are related to mollusks, octopuses have no remnant of a shell. On the other hand, squids have a pen, a stiff structure that acts like a flexible backbone.
Squids and octopuses both have eight arms lined with suckers. But squids have two additional, prey-capturing tentacles that can be compared to implements from a horror film.
Their diets are also different. Octopuses feast on bottom-dwelling crustaceans, while squids eat fishes and shrimps. And, while squids live in schools in the open ocean, octopuses reside alone in sea floor dens.
squids ever daydream?
Strictly speaking, “octopi” is not a correct plural for octopus. The “us” at the end of “octopus” is not the Latin masculine ending that would pluralize as “i”. It is acutally part of “pus”, Greek for foot, the word “octopus” a Latin/Greek conglomoration meaning 8-foot(ed). Thus the formal options for pluralizing the word would be “octpuses” and “octopodes”. While “octopi” is so common a usage as to be properly regarded as correct, I would think a dictionary site should make note of the mistaken folk etymology.
[...] box of whole squid for bait frozen — once was just a few dollars. — We’d take it home, thaw it, and [...]
OMG I love you guys! This was the most fascinating blog entry by far! I love learning about new additions to the animal kingdom, it makes me feel like the world around us is expanding! I love love love marine biology since it is such an active field, there are so many critters being discovered every day! Thank you soooo much and now I am off to research the dracula fish and squidworm now, I am so intrigued!
Most interesting and informative article. Actually, the word ‘interesting’ understates it.
It’s octopi, not octopuses.
Your article taking me back to remember “Paul” the oracle octopus died on Oct 26, 2010. May be for another comparison between large squid and octopus that should be taken into account is octopus got 9 brains.
Sad to know that octopus life span is not long which is two and a half years. How’s about large squid?
um so i cant understand youre wordds. thay our to big for me too now. wy cant you just make them so i can understand? wats a crustacean?
DONT JUGE ME!
What? I thought squids have nine arms. Man, they are too much the same.
I suppose squids are a lot smarter because they live in schools.
LOL
Octopi and squid aren’t relanted to molluscs, they ARE molluscs. And the creation of a new genus in the discovery of a new animal isn’t all that unusual, especially with new deep-sea technology. And just what was so “vicious” about difference between squid and octopi?
That is nice to know…………………………..
Very interesting. Funny how people do that.
Intriguing article! Fascinating and informative. Good work.
Squid also have round pupils but octopii have rectangular pupils, which, by the way, are oriented by autotonical reflex to a consistent horizon, relative to the body position.
Yuk, but so ingenious.
Is this the part where someone points out that because “octopus” is Greek, not Latin, the appropriate plural would be more like “octopedi”?
What amazing creatures God has made.
If you follow your own link for octopi you will see that is not the correct plural form. Octopus is from a Greek root, not Latin.
Sincerely,
The Grammar Police
Funny, I always knew there was a difference between the two but I never knew what it was. Cool info!
Who cares! all i know is that there both great fried and in salads.
evolution in plain view… amazing!!
I cannot subscribe to the irrelevance of this article. Aside from some informational falsities (octopuses/octopeds [both, from a zoological standpoint are acceptable] have commonly been known to eat fish, shrimp, small sea turtles, and other cephalopods…not just crustaceans) and grammatical impurities, I can’t help but fortify Aleksei’s comment by saying that hundreds to thousands of new genera and species are discovered each year. You said yourself, there have been other cases of bioluminescent cephalopods (for example the Colossal Squid, Vampyroteuthis infernalis, and the Sparkling Enope Squid), so why does this case grab special attention. To respond to cyberquill, octopuses are actually smarter. They have showed intelligence on a analytical and problem-solving scale. Some species are also known to be negatively thermotaxic (they shy away from heat)
hoping to get promoted from squid to dolphin
octopus lives alone underground, squids live in school in the open ocean, sea mammals live by family with mystique communication.
Octopi and squid would not deem themselves low enough as to rely on God for their genesis.
What was also not mentioned in this article is the differences in “temperment” between the two animals. Squids are often quite “aggressive” by nature; whereas Octopuses are generally renowned for their shyness & passivity.
(By the way, kudos to “Rudolf” for the insightful information regarding the ‘proper’ pluralization of the name “octopus.”)
Dats interestin’. Cool info but wat’s da correct plural for octopus?
I love animals!
I agree that this is the best blog by far!!
amazing. Some animal with blue blood.
I’m still finding it annoying that people refuse to use the correct plural for octopus (octopodes or octopuses).
thanks for sharing this info. it helps me a lot.
Cool. You should compare the cuttlefish to those creatures as well
Informative and entertaining. Thanks for the good writing.
Has anyone here read that article on how scientist created life without using anything at all that was ever alive? Ohh…wait, that hasn’t happened. I’m sure that when it does (and it won’t) Sprode will be dancing in the streets.
@Rudolf Lowey-Ball
Thank you!!! Finally, SOMEONE other than me who recognizes that ‘octopi’, in fact, is incorrect. And that was a very informative paragraph on why. Convinced my friend like THAT! *snaps fingers* Thanks!
What about the giant squids deep in the oceans?
I never heard about a giant octopus.
Isn’t that another great difference between them?
I have heard there is a tiny, beach-loving, cephalopod, [size of a baby's little fingernail] that gets under the skin of vacationers {mostly} and are fatal if not discovered & attended to within 24-48 hr. from their entry.
Is this “Bio-Fi?” If not, and my info is factual, “neither is poisonous” must be untrue. Wot?
what would happen if they ran out of ink in a attack
@Mermaid: Your enthusiasm and desire to learn are positively endearing!
@sprode:
@sprode: Applause.
wow… I didn’t Know that Sqids had spines… :0
HEYYYYYYYYYYYYYYYYYYYYYYYYYY
Now I don’t know which is correct, octopodes or octopedi, but I’ll use octopodes because it is consistent with arthropodes and cephalopods. As to the English plural, is it octopuses or octopusses? I’ll vote for the latter as being consistent with the usual rules for plurals.
The plural of octopus is really octopod
Fascinating! I wonder what color the squid glows.
You guys are CRAZY.
I mean, really. Who needs to get all excited about the plural of “OCTOPUS?” Calm down people.
It is difficult to know how and if other creatures and subdtances have feelings.
Are you guys like super-intelligent marine biologists or something? I am a very intelligent individual, but seriously. NO ONE CARES ABOUT THE PLURAL OF OCTOPUS.
I kinda like this comment thing. It’s fun 
By the way, I’m REALLY sorry if I offended anyone. Please leave a comment in response to mine if you truly think someone cares about the correct plural form of octopus. Oh, and the article was great. Especially for marine-biologists (which I am not…)
there are actually three known species of poisonous cephalopods: the Blue-Ringed Octopus, the Pajama-Striped Squid, and the Flamboyant Cuttlefish.
Nope! It’s Octopi (:
I just want to say that this is quite useful and I enjoy reading “the hot word”.
it said fishes. fish is plural for a fish. it doesnt change.
if you click on my name. click on this name.
I used to think squids had six arms; that’s how i remembered the difference. But I thought only fish lived in schools. Squid do too?
I didn’t check all the comments to see whether anybody mentioned either animal as being intelligent. They showed experiments being done with octopuses in both Spanish and Italian coastal waters. These mainly involved their problem-solving skills, and their intelligence is amazing.
So I’m beginning to wonder if squids have the same degree of intelligence, though since they have a stiff backbone (pen), they may have more trouble with these experiments, some of which required total flexibility.
Octomopuses have 6 legs, and 2 arms.
@bubbles
Actually, “fishes” is an acceptable plural of fish, especially if you’re referring to a group comprised of different species.
As for all of you people who get annoyed by “Octopi,” common usage defines language. I seriously doubt that you use the proper Latin pronunciation for our Latin loanwords (you’d sound pretty silly if you did). Don’t make me list all of the preposterous hypocrisies that you’re guilty of.
~Saf
yummy 
good point,Rudolf Lowey-Ball.♥
i love squid!!!!!!!!!!! actully thats my nick name!!!!
squid is my nickname
NEVER HAD AN ENCOUNTER WITH A SQUID BUT IN HAWAII A LITTLE OCTOPUS WOULD COME OUT OF HIS LIL BROWN BOTTLE ON THE OCEAN FLOOR AND HUG MY FOOT SEVERAL TIMES. IF I MOVED HIS LIL BROKEN GLASS DOOR HE REACHED OUT AND CLOSED IT….. I WONDER IF HE IS STILL THERE………… OH NO! ! ! THAT WAS SEVERAL YEARS AGO…. NOW I’M SAD AT HIS LOSS.
the reason they have blue blood is that they originated from the planet vulcan and were deposited here to confound our emotional views of the the world as we know it
It easily one of the most fascinating feature you guys posted.. Two thumbs up to the hardworking staff. The article says it’s “interesting”, I’m thrilled to disagree because it is undestatement,awe-strucking is the perfect word.To say the very least it disturbs the equanimity of my nonchalant mind.
@lingUist geeK-sage(RP):
hardworking enough that they’ve been deleting my comments for the past few days. SO here’s one for you iilii
@Funny Man
Actually, a couple of scientists did it and published their work 58 years ago (1953). Ever heard of the Miller-Urey Experiment?
i always thought they were the same thing…
Plus, octopuses are tastier than squids.