Classification: Kingdom Animalia,
Phylum: Mollusca,
Class:Cephalopoda,
Order:Teuthoidea,
Families: Loliginidae, Sepiolidae, and Architeuthidae.

Squids live in all the oceans of the world. They  are known as "the ice cream cone of the sea" because of their cone like shape and because they are a favorite food of many ocean dwellers.

Squids belong to the family of cephalopods. The word cephalopod means "head footed," and the animals are so named because the arms surround the mouth. Cephalopods are highly evolved animals in terms of structure and physiology, and the complexity of their behavior is equal to that of fish.

What are Squids?
The Squid is an invertebrate (animal without a backbone) that swims in the oceans. This mollusk is closely related to the octopus. They can change the color of their skin to mimic their environment and hide from predators.

Squid have a soft-body. They move by squirting water from the mantle through the siphon, using a type of jet propulsion. When in danger, squids squirt a cloud of dark ink in order to confuse their attacker and allow the squid to escape. Squid reproduce by releasing eggs into the water. Some squid eggs are free-floating while others are attached to seaweed or to the ocean floor.

What do they look like?
Squids are rarely seen. They hunt smaller sea creatures and larger fish feed on them.

Squid range from 1 to 60 ft (0.3 to 18 m) long. The biggest squid is the Giant Squid (Architeuthis). Squid have a large mantle/head (with a large brain), eight arms with suckers, two longer feeding tentacles, a beak, a large head, two large eyes, and two hearts. Their large eyes are very similar in structure to peoples eyes. They breathe using gills.

What do they eat?
Squid eat fish, crustaceans (like shrimp), and other squid. These fast-moving carnivores (meat-eaters) catch prey with their two feeding tentacles, then hold the prey with the eight arms and bite it into small pieces using a parrot-like beak. With this sharp beak they cut food into bite sized chunks. A file-like radula (rough tongue) rams food down the throat and esophagus. The esophagus runs through the brain directly to the stomach.

Who eats them?
Many animals prey upon squid, including many sharks and other fish, some whales, squid. People also hunt squids for food.

How Do They Move? 
Squids can move very rapidly and that is why they are known as `invertebrate atheletes`. They make use of a jet propulsion technique by sucking in water through the mantle opening. Then the mantle shuts by a  locking mechanism and the mantle muscles contract. Then the squid propels forwards or backwards as water jets out in a funnel  When the squid needs speed, it rapidly contracts the mantle which forces water out the funnel and rapidly propels the squid in the direction opposite to that in which the funnel is pointing. Because the funnel is flexible, squid can actually move backwards or forwards, depending on which direction the funnel is pointed.

Giant Squid
Can you imagine an invertebrate large enough to battle a sperm whale and win? Scars on sperm whales show that that`s just what happens sometimes when they try to eat  the giant squids. These deep dwellers measure upto 20metres (66ft) long, including their tentacles.