Squid are ten-armed marine cephalopods that can be found in all the oceans of the world in a wide range of sizes, from extremely small to colossal. A large number of distinct families are found under the order Teuthoidea, which encompasses all animals known by this name. Thanks to their widespread distribution, they play a role in many cuisines, usually in the form of fried or sauteed dishes. They are also the subject of study by marine biologists.
Classically, the squid has an elongated body, marked at one end with two fins used to stabilize it while it swims. It has ten arms, including two longer tentacles that are used for grasping and manipulating food. The body is covered with a mantle, a flexible layer of tissue that protects the delicate inner organs. Inside the mantle is the pen of the squid, a hard protrusion that is all that remains of the creature's shelled ancestors.
Propulsion is the primary mode of movement for these animals. They push water through their central cavities to create a jet of water, and can move quite rapidly using this technique. Like their relatives the octopi, squid are extremely intelligent, and some species are capable of using logic on par with mammals on land. Both males and females also have an ink sac, which can be used to squirt ink as a defense measure, allowing the creature to escape from predators.
Like many animals that live in the ocean environment, some species are capable of withstanding immense pressure, and can be found quite deep in the ocean. Giant squid in particular stick to the depths of the ocean, and may live out their entire lives in the dark of the deepest areas. Some have been estimated to reach lengths of up to 80 feet (25 meters), although living specimens of that length are difficult to recover. Periodically, a giant squid washes ashore or is caught in a fishing net, offering biologists an opportunity to study it.
Squid are carnivores, and they are also highly sought after as a food source. Humans eat them in a wide variety of sizes, especially since every part of the animal except for the pen is edible. The flesh is slightly chewy and sweet, although it will be rubbery if it is prepared poorly. In nations that border the ocean, the creature is a common ingredient in an assortment of dishes, from calamari to Thai squid salad.