Squid eat mainly small fish and crustaceans, while octopuses will eat just about anything they can find, including other squids. Squid are also faster swimmers than octopuses. The main difference between squid and octopus is that squid have two tentacles, while octopus have eight. Over the course of evolution, this may have helped make their cognitive abilities more complex than those of other invertebrate relatives like snails. Main Difference Between Squid and Octopus. They also evolved a unique genetic mechanism, called RNA editing, that lets them diversify the number of proteins in their neurons. They have relatively big brains and millions of neurons in their arms. Today, there are some 800 living species of cephalopods, all of them whip smart. “It became a much more successful strategy to be a really high-metabolism, very rapid-moving animal,” Alastair Tanner, a biologist at the University of Bristol, in England, told The Times in 2017. There was a burst in fish diversity, and predators had to become strong enough to crush shellfish or fast enough to catch their prey. But when cuttlefish, squids and octopuses began to evolve separately - 160 million to 100 million years ago, during the so-called Mesozoic Marine Revolution - life was undergoing a rapid change. Giant squid, Architeuthis dux Steenstrup, collected 24 August 2007 off Cape Foulwind, New Zealand.
In contrast, giant squid weigh up to about 275 kg. Te Papa’s colossal squid tips the scales at a massive 490 kg. Hundreds of millions of years ago, all cephalopods had heavily armored shells. Colossal squid Mesonychoteuthis hamiltoni are slightly shorter than giant squid Architeuthis dux, but have a larger, heavier body.