The main difference between squid and octopus is that an octopus doesn’t have stiff bones in its body, allowing it to squeeze through the smallest gaps. A squid has a flexible backbone called a pen, which runs through the animal’s whole body and stabilizes it while swimming.
It can be tough to differentiate between a squid and an octopus because of their similar appearances. Plus, both belong to the class Cephalopoda, live in the ocean, and have bilateral body symmetry, making distinguishing between them even more challenging.
Despite these similarities, squid and octopus have their physical distinctions, unique behavior, and habitat preference.
Table of Contents
Difference Between Squid and Octopus
| Squid | vs | Octopus |
| Order Teuthida, Phylum Mollusca, Superorder Decapodiformes | Classification | Order Octopoda, Phylum Mollusca, Superorder Octopodiformes |
| Coleidea | Subclass | Coleidea |
| Animalia | Kingdom | Animalia |
| 300 | Species varieties | 298 |
| Squids (two or more species), squid (collective) | Plural | Octopods, octopuses, octopi |
| Prefers to live in alone and groups | Prefers to live in | Solitary creatures |
| Both surface and great depths of sea waters, saltwater | Found in | Saltwater, shallow and deep open ocean waters |
| Have two fins | Fins | None |
| Triangle head with eight arms and two extra long tentacles. | Appearance | Round head with eight long arms. No shell. |
| Blue | Blood | Blue |
| 9 months to 5 years (can live up to 15 years) | Lifespan | 1 to 3 years (can live up to 5 years) |
| Prefers to eat shrimp and fish | Preferred diet | Bottom-dwelling crustaceans like worms, clams, etc, |
| 1cm to 20cm in length | Size | 1cm to 5cm in length |
| Squids use their long tentacles to grab prey, break the meat with their beak, and consume it in chunks. | Hunting Technique | Use the piercing method to release a paralyzing venom on the prey. Then they use their saliva to loosen the meat. |
| Squids mate in large groups and attach eggs to seaweed, seabed, and rocks. They let the eggs float without guarding. | Reproduction | Male releases the sperm to the female body through a special arm called a hectocotylus. Female lays the eggs on the roof of her den and guards them until they hatch. |
What is a Squid?
Anatomy
A squid is a soft-bodied mollusk that lives in the ocean. Squids have triangular heads, eight arms, long bodies, two long tentacles, two fins on the head, and a bony plate called a pen.
Biological Classification
There are almost 300 species of squids, and they are cephalopods. The personality of squids depends on their species. For example, the Humboldt squid is very aggressive and may attack even the largest marine animals.
Size
Squid sizes vary depending on the species. They can grow from 2 ft. to 60 ft. long. The Sepiolid is the tiniest squid and grows smaller than half of an inch.
Life Span
On average, squids can live anywhere between 1 to 5 years. Often, both squids and octopi die soon after mating, so they usually live until they reach their reproductive age. But this isn’t true in every case, and some scientists claim that few squid species can live up to 15 years.
Locomotion
Squids swim by jet propulsion. They suck water into a muscular sac in the mantle cavity, circling their bodies. Then they quickly expel it out of a narrow siphon. Squids can swim in any direction and change their route in no time.
The fins help squids propel themselves when swimming at a low speed. The fins wrap around the body when the squid swims faster and stabilize the squid when it swims slowly.
Habitat
Squids live in various parts of the open sea. They can be found in shallow waters and the deepest ocean parts.
Diet
Squids love to feed on shrimps and small fish. They usually don’t prefer any other animals.
Hunting
Squids catch their prey using their two extra-long tentacles. They then tear the pieces of flesh and eat the meat using their beaks.
What is an Octopus?
Anatomy
An octopus has a round head, eight arms, and one or two rows of suckers, but there are no hooks or rings on the suckers. Octopus suckers are the circular disk-like tools octopi use to grab onto objects using suction. They can hold up to 35 lbs.
Biological Classification
Like squids, octopi are also cephalopods. It means they are head-footed and lack actual feet. Octopi don’t have hard shells, so scientists classify them as invertebrates and mollusks. There are almost 298 species of octopus which is nearly the same as squids.
Size
An octopus can grow anywhere from less than an inch to nearly 30 feet. This makes even the most enormous octopus smaller than a giant squid. Octopus can camouflage by changing its shape, color, and skin texture.
Life Span
Some octopi live only for six months, but their average lifespan is 1 to 3 years. Like squids, octopi also die after giving birth, so their lifespan is relatively shorter.
Locomotion
Octopi also swim through jet propulsion. They use the same method as squids and can move in any direction. Most octopi don’t have fins like squid do. However, some deep water octopi may have fins.
Habitat
Octopi live in the dens of the seafloor level, in both shallow and deep waters. You can find octopi living among the bottles or garbage that have found their way to the ocean floor.
Diet
Octopus prefers to eat crustaceans such as clams, crabs, and whelks. But the larger octopus species also eat fish and shrimps.
Hunting
Octopi use their ringed arms to catch their prey and then pierce a paralyzing venom in their body, making the prey unable to move. The octopus then releases salivary enzymes that loosen the meat from the hard part.
