Squids and octopuses are cephalopods, members that fall under the molluscan class Cephalopoda. But these aquatic invertebrates do not have shells. Their blood is blue due to the presence of copper in it, and they also have three hearts each. But octopuses and squids differ in their physical characteristics, habitat, and behaviour.
An octopus has a round head, while a squid’s head is triangular in shape. Octopuses do not have any bone in their body, while squids possess a stiff structure known as a pen that acts as a flexible backbone. Octopuses do not have fins, while squids have two on their heads. Both have eight arms, but squids have two specialized tentacles in addition which are used to catch prey.
While octopuses live in the ocean floor, squids live in the open sea at various depths depending on the species. Octopuses feed on crustaceans on the sea bottom, while squids feed on shrimps and fishes. Usually, squids are larger than octopuses.
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