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Squid are 10-armed cephalopods found in both coastal and oceanic waterways. "Cephalopod" means "head footed," because the arms of the squid and others in this family surround the mouth.

Belonging to the order Teuthoidea, squid have managed to remain somewhat of a mystery to scientists and oceanographers. This free swimming mollusk is closely related to the cuttlefish and octopus.

Very little is actually known about the squid and its past. Science tells us that the first mollusk fossils are some 600 millions years old. Highly successful in terms of adaptation and ecology, the squid has transformed parts of its body to allow itself the ability to live in diverse areas of the sea. The octopus and squid are considered to be two of the most advanced animals in the mollusk family.

Squids range in size from less than 3/4 of an inch to more than 65 feet. Two of their 10 arms have developed over time into long slender tentacles, which expand at the ends and hold four rows of suckers. With elongated tubular body and large head, the squid is a simple looking creature. The squid's eyes are located on the sides of its head and are said to be as complex in nature as the human eye. Though vision is poor in most mollusks, squids have eyes with lenses, retinas, and many other features which resemble those of vertebrates, allowing for more accurate vision.

Squids are considered the most highly developed of all invertebrates, due to their sophisticated nervous and circulatory system, and the fact that they carry no external shell, and continue to survive.

Squids prey on fish, which they grab with their suckered tentacles and then pass to shorter arms, which hold the food. The squid's jaw, which is often compared to a parrot's beak, then tears the food apart for eating. Digestion in most cephalopods, including the squid, is rapid.

Much of the mating habits of the squid is yet to be studied. Scientists do know that the male squid has one small arm which is used to plant a packet of sperm in the female's oviduct. In some species of squid, sperm can also be deposited in a vesicle just below the female's mouth. The female squid takes over from there, depositing and fastening eggs to seaweed. Deep-water squid are impregnated in much the same way, but often allow their eggs to free-float.

When in danger, a squid will propel itself away from the source quickly, leaving behind an ink cloud which hinders pursuit. Also known as an aggressive carnivore, the squid moves by means of a sort of jet propulsion, which multiple legs flinging itself through the water.

Because squid vary in size so greatly, each separate species has different predators. The common squid of the Atlantic Ocean is prey to the sperm whale and several other large fish.

Today, the squid population continues to rise, despite avid fishing efforts by the restaurant industry. Squid is considered a delicacy in both Asia and the United States. Scientists and Oceanographers continue to make strides in piecing together the history of the squid.