What Is the Difference Between a Squid and an Octopus? A Quick Guide to Telling Them Apart

The octopus is the collective name for animals of the genus Octopus in the family Octopodidae; it is a marine mollusk and does not belong to the fishes. When a squid encounters a powerful enemy, it uses "ink spraying" as a means of escape and seizes the chance to get away, which is why it has names such as "squid" and "inkfish"; its skin contains small pigment sacs that change color and size with shifts in its "mood." Now let us take a look at what the differences between squid and octopus are!

The Difference in Family and Genus Between Squid and Octopus

1. Squid: The squid is a mollusk of the animal kingdom, phylum Mollusca, class Cephalopoda, subclass Neocoleoidea, order Sepiida, suborder Sepiina, family Sepiidae, genus Sepia.

2. Octopus: The octopus is a mollusk of the animal kingdom, phylum Mollusca, class Cephalopoda, subclass Coleoidea, order Octopoda, suborder Incirrata, family Octopodidae, genus Octopus.

The Difference in Arms Between Squid and Octopus

1. Squid: The squid's foot has become specialized into arms and a funnel. It has 10 arms arranged symmetrically on the left and right; the first pair is at the very center of the back, and toward the ventral side come pairs 2 to 5 in order. The fourth pair of arms is especially long, with an expanded, tongue-shaped tip, located at the front of the body and appearing spherical, with the mouth at its tip. There are 10 arms in total: 8 short arms and 2 long tentacles used for catching food, surrounded by a buccal membrane; these are called tentacles, can capture prey, and can be retracted into tentacle pouches.

2. Octopus: The octopus has a short, oval, sac-like body with no fins, and the boundary between head and body is not obvious. On the head are large compound eyes and 8 retractable arms, each bearing two rows of fleshy suckers. It usually crawls with its arms, sometimes swims by stretching and contracting the membrane between the arms, can grip other objects powerfully, and uses the funnel below its head to spray water for rapid backward escape.

The Difference in Feeding Habits Between Squid and Octopus

1. Squid: The squid mainly eats crustaceans, small fish, or other mollusks. Its main enemies are large aquatic animals. The ink in its body is normally stored in the ink sac in its belly; when an enemy attacks, it sprays a stream of ink from the ink sac, dyeing the surrounding seawater pitch black, and then takes the opportunity to flee.

2. Octopus: The octopus feeds on lamellibranchs and crustaceans (shrimp, crabs, etc.), and some species eat plankton. The octopus draws water into its mantle; after breathing, it expels the water from its body through a short funnel-shaped siphon. It mostly crawls along the sea floor using its suckers, but when startled it sprays a stream of water from its siphon, and the jet is so powerful that it moves rapidly in the opposite direction. When in danger, it sprays an ink-like substance as a smoke screen, and some species produce substances that can paralyze an attacker's sensory organs.

The Difference in Intelligence Between Squid and Octopus

1. Squid: The squid has a well-developed nervous system composed of the central nervous system, peripheral nervous system, and sympathetic nervous system, but its brain is not fully developed, and it acts on instinct.

2. Octopus: The octopus has "conceptual thinking" and can solve complex problems on its own; it is precisely this ability that gives it the skill of walking on two arms. Its quite well-developed brain allows it to recognize itself in a mirror.