Distinguishing Octopus, Squid, and Cuttlefish
The octopus might be an easily distinguishable fellow for most. Those signature 8 tentacles and that bright red body makes it easily recognizable even among its mollusk peers, though some still confuse it for squid. Squid and cuttlefish, on the other hand, seem to have similar attributes that make distinguishing each from the other more difficult from afar. When examined more closely, however, they have their own differences that makes it easy to tell which is which.
This article will examine the differences between these three cephalopods, and how you can tell them apart.
Body Structure
All three are in Class Cephalopoda which sits in the Phylum Mollusca, which is just a fancy way of saying that they are cephalopods, a subgroup of mollusks. They are also invertebrates and, unlike most mollusks, have no shell. Another distinguishing feature that they all have is the presence of tentacles on their bodies, or at least some form of it.
These features make them seem like similar creatures at first, but once we get to the nitty gritty bits of it, maybe not so.
Octopuses are known the most for having eight tentacles. Each tentacle has two rows of suction cups which are ring-shaped. This helps them to grasp surfaces while also giving them a sense of touch.
They also use these tentacles to hunt prey. To do this, they drop onto them from above and use the suction of their tentacles to pull the prey into their mouth. These tentacles also have taste sensors, so if one is feeling your body with its tentacles, it is actually also tasting you. Not really a good image to think about, I feel.
Octopuses in media are also commonly depicted as red, which is true. But they also have a wider range of colors. Take for instance, the blue ringed octopus, whose body looks more yellowish with blue rings covering its body, as to help it blend with its surroundings.
Contrary to its appearance, squids only have two tentacles. The many appendages you see are actually called arms. It is only the two longest arms that are referred to as tentacles. The suckers on a squid’s tentacles are usually arranged in clusters at the end of the tentacle, but other species may have their suckers with a different appearance.
The tentacles of the squid are used to grab its prey, while delivering it to its mouth. Along the way, its 8 arms are then used to help hold the prey to minimize its potential to escape. Its mouth has a beak that cuts food into suitable chunks for swallowing. It is actually quite strong, as it can break open shells!
Their appearance is quite cylindrical and elongated. They also have a tight shell-like structure inside their body called a pen. To move, they suck in water and quickly expel it out through a narrow siphon, propelling the squid forward. This process is called jet propulsion.
The raw squid you see in the market may be white with some purple splotches, but there are many species all over the world with different kinds of adaptations, such as having the ability to change color to hide itself in the water and being able to shoot ink at predators to cloud the water and get away. Some even use bioluminescence to create light!
Like squids, cuttlefish have eight arms and two tentacles. They serve the same role as they do with squids. The tentacles have suckers which grasp the prey, while the arms bring them to its mouth.
One of the easiest ways to separate cuttlefish from squid is to simply look at their eyes. While both cephalopods have large eyes, cuttlefish are distinct as their eyes have W-shaped pupils.
Cuttlefish also have an internal shell-like structure like the squid called the cuttlebone. It helps provide the cuttlefish with buoyancy. If you think that’s too disgusting for simply differentiating between the squid, you can check their speed underwater. Squid can swim amazingly fast thanks to their propulsion technique, while cuttlefish are not going to be winning any medals in the Olympics anytime soon. They are not fast and swim by undulating long fins on the side of its body.
Finally, when the shapes of their bodies are compared, cuttlefish look more flattened compared to squids.
Habitat
Octopuses are quite widespread and can be found across all oceans across the world. They are commonly found in coral reefs and the ocean floor, but some species prefer being close to the surface.
Octopuses are quite adaptable. They can create their own dens, or squeeze into crevices to hide. They may even choose to fit in empty shells or even bottles! These are not permanent abodes, however, as octopuses tend to move on to find another shelter after around two weeks has passed.
Squid are also quite widespread around the world. Many of them prefer hiding deep under water, at least 1000 feet below the surface.
They are also highly adaptable and move to where their prey moves and can move on even if their natural habitat is destroyed.
Cuttlefish are also adaptable to their environment, and can be found in deep, shallow, cold, or tropical waters across the world. They can even be found as deep as 2000 feet! However, they are also known to spend their time hiding in deep water during winter months before moving to shallower depths once spring and summer arrive.
Diet
Octopuses are generally known to have a meaty diet, and they will consume fish, sharks, and even shellfish and other octopuses. Some octopuses poison clams by drilling through their shells and injecting them with poison to make their muscles relax, allowing the octopus to pry them open and eat the occupant.
To kill a shark, some species of octopus use their arms to immobilize the shark. Sharks, needing to be in constant motion all the time to absorb oxygen in their gills, will suffocate if this happens. Once the shark dies of suffocation, the octopus can proceed to eat it.
They can even choose to hunt birds if given the chance. Seagulls, for instance, are a prime target if they dip too close to the water, allowing the octopus to pull it down to the water.
Squids have to be a bit fussier. Their size makes it so they can’t exactly hunt sharks (and are instead prime prey for them), but their advantage lies on speed. Thanks to being fast swimmers, squids can chase after many small fish, crabs, and shrimp to eat. Sometimes they will eat other small squids, but this is only if food is scarce.
Young Cuttlefish mostly eat small shrimp, crustaceans, and even larvae after hatching.
After growing, their diet changes, and they will start hunting fish, crabs, and other mollusks. Unfortunately for eight-armed friend, octopus is part of the menu for cuttlefish.
To hunt, they use camouflage to sneak up on prey. When an easy target presents itself, the cuttlefish immediately grabs onto the prey with ease and starts lifting it to its mouth. Some prey, like crabs, are buried under the sand, and the cuttlefish scares them into the open water by shooting out a jet of water at them. This leaves them wide open to being caught by the cuttlefish.
Finishing Up
These cephalopods are quite impressive and different in nature, even when they seem similar at first. Their methods of hunting differ, and even their types of prey differ.
You would think octopus are the best hunters for chasing down sharks until you find out that cuttlefish eat octopus. Then you find out that sharks eat cuttlefish.
It’s just the circle of life.