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Squid vs Octopus: What’s the Difference?

Kyle W by Kyle W Updated on June 15, 2021. In

Squid vs Octopus

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Can you categorically differentiate between a squid and an octopus? Don’t worry; you would be forgiven for confusing one for the other. This is mostly because squids and octopuses have similar physical attributes from that prominent head to those tentacles and even their swimming mannerisms. That, however, does not mean that they are one and the same.

Let’s take a look at some of the similarities and differences that can help you differentiate between the two.

Also Read: Flounder vs Halibut – All You Need to Know

Biological Classification

One of the main reasons why squids and octopuses look so similar is because they belong to the same family of marine mollusks called cephalopoda. This makes them cousins. Apart from squids and octopuses, the cephalopoda also includes snails and nautilus.

The largest member of this family is the giant squid, while the smallest is the pygmy squid. All of them have symmetrical bodies, prominent heads, no vertebrae, and tentacles or arms. Unlike their cousins, the snails and the nautilus, squids, and octopuses evolved and no longer require the use of a hard shell for body protection. In its stead, they developed a host of other adaptations such as the ability to camouflage, strong, flexible arms, and heightened intelligence to survive and thrive.

There are about 300 species of octopuses and another 300 species of squid in the world’s oceans, and they all have some resemblance to one another.

Squid vs Octopus

Now that we know they come from the same family, let’s take a look at some of the features that can help you to more readily distinguish between the two:

The Anatomy

Yes, squids and octopuses have some similarities, but you can immediately tell that they are different animals just by looking at them. For example:

  • Octopuses have round heads and eight tentacles or arms that jut out from its body like the spokes on your bike, while squids have triangular heads and eight tentacles that extend from the rear of their bodies.
  • Squids also have longer bodies, two extra-long tentacles, and a bone plate, which is a vestigial remnant of what used to be a mollusk shell.
  • Squids tend to have two fins on their heads. For the most part, octopuses don’t have such fins at all except for a few deep-water species such as the Dumbo octopus, which incidentally was named the Dumbo octopus because it has a couple of ear-like fins that resemble the ears of Dumbo (Disney’s cartoon elephant) sticking out from its head.
  • Both animals have suckers on their tentacles, with the biggest difference here being that the two extra-long tentacles extending from the body of squids have sucker rings with teeth and specialized hooks.
  • Both animals have copper in their heads, which helps transport oxygen throughout their bodies. It’s this copper that makes their blood blue (in both animals).
  • Both have squirt ink

Body Sizes

Due to pop culture and horror films involving monster octopuses, most people believe that octopuses are the bigger of the two. The truth is that; octopuses tend to grow from 1 centimeter to about 9 meters. While the pygmy squid might be the smallest in this family (growing to an average of 2 centimeters), squids, in general, tend to be much bigger than octopuses, with an average body size of around 60 centimeters to almost 20 meters long.

Habitat

Octopuses tend to be solitary animals that prefer living on the seafloor. This, however, doesn’t mean that they are necessarily deep-sea creatures, as you can find some octopuses in shallow waters or in dens that are on the seafloor of shallow waters. Squids, on the other hand, tend to live in schools or solitary lives.

Some squid species live in schools when younger then become solitary creatures when fully grown. Unlike octopuses, squid prefers living in the open ocean when they can hunt for other fish. They can be found in shallower waters to the darker depths of the sea.

Octopus on the seafloor

Since these two creatures have almost similar anatomies, their hunting behavior and techniques both resemble one another as well as vary to some degree:

Squid Hunting Techniques

Since squid tends to swim in the open ocean mostly, their hunting techniques involve heavy use of their tentacles. They make good use of the two extra-long tentacles with suckers and teeth to reach out and grab shrimp and other fish, which they then eat in chunks.

Octopus Hunting Techniques

Very much like their cousins, the squid, octopuses also use their tentacles to grab and hold onto prey, but that’s about as far as their similarities go. The biggest difference is that instead of using sucker rings and teeth (which they don’t have), they grab and inject their prey with poison, paralyzing the prey.

Once completely helpless, octopuses slather their prey with saliva, which dissolves and loosens the meat before using their mouths and beaks to rip and tear the meat from said prey. They prefer to hunt for bottom-dwelling crustaceans because their soft bodies are vulnerable to predation.

Lifespan of Squid vs Octopus

This is yet another key difference between octopuses and squids. Considering how small these two species can get, they both have decent lifespans, with octopuses living anywhere between 1 to 3 years on average and squids having a life expectancy of about nine months to about five years.

Reproduction Similarities

Perhaps the biggest similarity between the two, both creatures tend to die after mating. Octopuses are semelparous animals that only reproduce once and then perish. In octopuses, as soon as the female lays a clutch of eggs, she simply stops eating and slowly wastes away. She dies by the time the eggs hatch. Also, in a rather macabre twist, female octopuses tend to kill and eat their mates.

Squids also do the same thing except for kill and eat their mates. Male squids do die shortly after mating, and female squids also die once she releases her eggs.

Also Read: Best Tasting Freshwater Fish to Eat

While they both taste delicious depending on how you cook them, squids and octopuses do have a few differences despite coming from the same family.

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