Telling the difference between cuttlefish and squid isn’t easy. These appear quite similar at first glance. Upon closer inspection of these mollusks.
Cuttlefish and squid are both in the cephalopod class in the phylum Mollusca. A phylum is simply a level of classification. The octopus and nautilus are also part of the cephalopod class.
We’ve always had a fascination with creatures like cuttlefish and squid. Even Aristotle pondered the mystery of these cephalopods of the deep.
In this article, I’ll compare cuttlefish with squid to show you the similarities and differences between the two.
What is a Cephalopod?
Cephalopods are highly intelligent marine animals. These creatures have a history spanning almost 485 million years. It’s interesting to note that there are more extinct cephalopods than living ones.
Ancient cephalopods had sturdy shells for protection. Over time, they lost their outer coverings. They began to rely on new capabilities, like flexibility, intelligence, and strength, to protect themselves. Today, we can see that in cuttlefish and squid.
Cephalopods also developed greater camouflage skills and are experts at hiding. They are the perfect spies.
Three main features make a cephalopod. First, they have blue-colored blood. Second, they use propulsion systems for rapid movement. Third, they have either arms or tentacles (more on this below).
Let’s take a closer look at the characteristics of cuttlefish and squid.
The squid has eight arms and two longer tentacles. Their body shape is described as fusiform, which means torpedo-like. The inner shell of a squid is described as a lightweight “pen” and provides structure.
The head of a squid is called a mantle. They use jet propulsion and two small fins atop this mantle to swiftly move through the water and catch their prey. Some can even fly.
There are over 300 species of squid. The Giant Squid is the largest cephalopod. It can grow to 40 feet and weigh as much as a ton in just five short years.
Squid grow incredibly fast and don’t live long. They live in a variety of places like coral reefs, open ocean waters, or deep on the ocean floor. They use their arms and tentacles to walk.
Squid have incredible bioluminescent abilities. Bioluminescence is a chemical process that produces light from an organ called a photophore. A chemical reaction in this area causes light to shine from inside the organ similar to fireflies.
They use this as a kind of counterillumination. Squid use it to ward off predators lurking below or to confuse prey.
Cuttlefish also have eight arms and two tentacles. The two tentacles are retractable and can triple in size when extended.
There are more than 100 species. They have a flattened body with fins that run along the outer edge.
They have a large cuttlebone made of calcium that provides structure to their bodies. The cuttlebone is oval and porous. It helps cuttlefish hover while searching for prey along the ocean floor.
The largest cuttlefish in the world is an Australian Giant Cuttlefish. It can grow to be 20 inches in length and weighs more than 20 pounds.
The Flamboyant and Dwarf Cuttlefishes are the smallest on the planet, measuring only 3 inches and weighing only a few ounces.
They are famous for the psychedelic color display they use to communicate with each other. Cuttlefish have the most sizable brain-to-body ratio because of this communication style.
These colors come from the 20 million chromatophores that cover the skin of a cuttlefish. Chromatophores are cell pigments that connect to tiny muscles. It uses those muscles to control its coloring in any situation.
Arm or Tentacle?
The word cephalopod means “head feet” in Greek. It refers to the body structure of cephalopods. It is a large head with “feet” that extend directly from the head.
Now, these “feet” are really called arms or tentacles, but what’s the difference?
Arms have suction cups along their whole length like the limbs of an octopus. Tentacles only have suction cups on the tip of the limb. Sometimes those suction cups can have teeth like those of a squid.
Cephalopods can have arms or tentacles or even have both. Cuttlefish and squid are both examples of cephalopods that have arms and tentacles.
Comparing Cuttlefish and Squid
You can already see that cuttlefish and squid are quite similar but also have some major differences.
Let’s take a closer look.
Some of the similarities between cuttlefish and squid include:
- They are from the cephalopod class.
- Both have eight arms and two longer tentacles.
- Cuttlefish and squid have fins along their mantle.
- They use propulsion systems to quickly maneuver in any direction.
- Cuttlefish and squid have amazing camouflage capabilities.
- Their main enemies are humans and large marine animals.
Many of these similarities exist simply because they are mollusks from the same cephalopod class.
The main differences between cuttlefish and squid are:
- Cuttlefish have flat, oval bodies, and squids have elongated rodlike bodies.
- Squid are significantly larger and heavier than cuttlefish.
- The shape of their internal shells is different – a squid has pen-like cartilage that looks like a feather while cuttlefish have an oval cuttlebone that looks like a spoon.
- Squid use bioluminescence, and cuttlefish use chromatophores.
- Cuttlefish only live for 1-2 years whereas squids live for 3-5.
- Squid live all over the ocean in any number of locations; cuttlefish live in shallow tropical waters.
Squid and cuttlefish are similar in many ways but differ in terms of their protection and communication methods, body shape, and overall size.
Cephalopods are fascinating creatures that evolved over millions of years. They are the most intelligent ocean animals on the planet. In fact, cuttlefish and squid are so clever they can solve mazes.
There is still much to be discovered about cuttlefish and squid. These are mysterious creatures, producing light and color displays that leave you in awe. Their intelligence is unrivaled.
After making this comparison between cuttlefish and squid, I hope their similarities and differences are clear to see.