Squid are cephalopods in the superorder Decapodiformes with elongated bodies, large eyes, eight arms, and two tentacles. Like all other cephalopods, squid has a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen made of chitin. They play an important role in the open water food web.

The two long tentacles are used to grab prey and the eight arms to hold and control it. The beak then cuts the food into suitable size chunks for swallowing. Squid are rapid swimmers, moving by jet propulsion, and largely locate their prey by sight. They are among the most intelligent invertebrates, with groups of Humboldt squid observed hunting cooperatively. They are preyed on by sharks, other fish, sea birds, seals, and cetaceans, particularly sperm whales. 

Squid form a major food resource and are used in cuisines around the world, notably in Japan where it is eaten as ika sōmen, sliced into vermicelli-like strips; as sashimi; and as tempura.
 

Shellfish

Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of mollusks, crustaceans, and echinoderms. 

Although most kinds of shellfish are harvested from saltwater environments, some are found in freshwater. Shellfish are among the most common food allergens.