Big questions often come from little people and there are so many times that I have been asked by children why I reference the limbs of an octopus as “arms” and not “tentacles”.
Arms have suckers down the full length of the appendage. Tentacles only have suckers near the tip. Thereby, all eight octopus appendages are arms while squid have two tentacles and eight arms. Further, the purpose of tentacles is generally limited to feeding where arms have more functions. Octopuses use their limbs for feeding, locomotion, reproduction (if male*), defence, etc!
Oh and why are they called “arms” vs. “legs”? Because octopuses’ appendages have more purposes than just locomotion.
There are scientists who have put forward that some octopus species use two of the limbs mostly for locomotion whereby they would have two “legs” and six “arms” but let’s avoid that debate!
While we are on the topic of semantics and cephalopods, and anticipating that there will be those who question my use of the plural form of “octopus”, please note the origin of the word octopus is Greek, not Latin. Thereby “octopuses” or “octopods” is truly more correct than “octopi”. From a strict linguistic perspective, the most correct is “octopods” but I choose not to use that. I think if I were to say “octopods” it would distract what I am trying to communicate that is more important that grammar. I might also come across as pretentious and have fewer human friends 🐙.
There, don’t you feel much better armed to speak for our awe-inspiring eight-legged neighbours? Or, are you up in arms?
*Related blog: Giant Pacific Octopuses – How Do They Mate?