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SAMANTHA CHENG (CONSERVATION BIOLOGIST, CENTER FOR BIODIVERSITY AND CONSERVATION): Hi, I’m Sam Cheng, I am a biodiversity scientist at the American Museum of Natural History. And I study cephalopods.

What do you need to know about these amazing creatures that include octopus and squids? Let’s start with the ABCs.

A is for Arms. Octopus have 8 arms, not tentacles like a lot of people think. Arms have suckers all the way up, whereas tentacles just have them at the ends.

B is for Belemnites. These extinct cephalopods looked kind of like squid, but they had a hard shell. They lived from about 230 million years ago to 70 million years ago.

C is for Cephalopod, of course. Cephalopod means “head-foot” in Greek, because of the way cephalopods’ heads attach directly to their arms. The basic layout of a cephalopod has two eyes, a mantle, a funnel or a siphon, and at least eight arms.

D is for Decapodiformes. This is a group of cephalopods that includes squids, cuttlefish, and those extinct belemnites. “Deca” means “ten”, which makes sense, since these critters have eight arms and two tentacles.

E is for External Shell. Ancient cephalopods used to have an external shell around their body. Today, modern cephalopods don’t have that shell except for nautilus and allonautilus.

F is for the Flamboyant Cuttlefish. This super charismatic cephalopod has flattened arms, and super bright colors to warn potential predators that it’s actually poisonous and they shouldn’t eat it.

G is for Gladius. This is an internal shell that some cephalopods have. It gets its name from an ancient Roman short sword that it kind of resembles. An example of a gladius is the cuttlebone of a cuttlefish.

H is for Hectocotylus. This is a specialized arm in male cephalopods that’s designed for delivering packets of sperm.

I is for the Ink that cephalopods release for self-defense. They can either release ink in a big cloud like a smoke bomb, so they can jet away undetected; or they can release their ink in a smaller cloud so that it distracts the predator and it’ll attack it instead.

J is for Jet Propulsion. Cephalopods move by sucking water in through their mantle, and shooting it out of their siphon. They use this to do things like make quick getaways and to capture their pray.

K is for the Kraken. This legendary sea monster terrorized sailors. And it’s thought that it was inspired by the real life giant squid, which can grow up to 40 feet long.

L is for Lirae, which is the little ridges that you can see on the outside of shells, including some cephalopods like the nautilus.

M is for Midden. Some octopus species like to eat their food in a shelter, like under some rocks. And they discard leftover bits of their pray around the entrance. Over time this builds up, and this pile of debris is called a midden. And it’s also sometimes called the Octopus’s Garden.

N is for Nautilus. Nautilus are considered to be living fossils because they’ve been around for over 500 million years. They have a hard outer shell and lots and lots of little cirri instead of arms and tentacles. Even though nautilus have been around for so long, they are actually at risk of extinction today because of over collection of their shells.

O is for some fun facts about octopuses. They have three hearts, they are masters of camouflage, and the correct plural form of octopus is octopuses, not octopi. Sorry.

P is for Photophores. Some cephalopods have a special light organ that’s bioluminescent. Species like the firefly squid can even do light displays with this organ that can be used to communicate with potential mates and distract predators.

Q is for Quiet. Because Cephalopods don’t make a lot of noise.

R is for Rostrum, which is the incredibly hard beak that squid and octopus use to kill and eat their pray.

S is for Siphuncle. This is a tube in cuttlefish and nautilus that help it maintain its buoyancy in the water.

T is for Teuthology, the study of cephalopods. Today, you are all teuthologists.

U is for Umbilicus, which is the hollow space that you sometimes see at the center of the whorls of a nautilus’s shell. Umbilicus is also the official term for our belly buttons.

V is for Vertebrae. Just kidding, cephalopods don’t have any.

W is for Wonderpuss. This is a species of small-bodied octopus that lives in the Indo-Pacific Ocean. It’s known for its ability to mimic other sea animals.

X is for Xanthophore. This is a type of cell that helps cephalopods change the color of their skin to camouflage with their surroundings. This is actually a type of chromatophore cell, which are cells that contain pigment or help reflect light.

Y is for “Why ” Why are we doing this? Because cephalopods are cool.

Z is for Zebra Display. Which is what some squid and cuttlefish use to attract a mate or hunt for pray. For example, the giant Australian cuttlefish displays a rapidly changing zebra pattern on its skin to intimidate other males while it’s courting a female.

There you have it, the ABCs of cephalopods. And this is just the tip of the iceberg of the intriguing knowledge we have of these amazing animals that are important parts of our oceans and of our lives.