Loligo shows a typical squid body form. The body is formed by a long tapering tube-shaped mantle. The fins vary in size and placement amongst different species. The mantle forms a casing that protects the internal organs and from which the head protrudes. Strong muscles expand the mantle, drawing water into the mantle and over the gills. The muscles contract and send the water through a narrow muscular funnel. This funnel can be aimed forward or backward by the squid and gives it extraordinary manueverability. The adaptations required for this quick escape system are one of the reasons squid have been so valuable to science and is further explored in our section on neurobiology.

The eyes are large and complex, giving the squid very sharp vision. Squids have ten limbs, only two of which are appropriately called tentacles. These are longer and can be extended out past the other eight arms to capture prey. Cuttlefish have a similar arrangment of eight arms and two tentalces ten while octopods only posess eight arms.

The arms and tentacles of cephalopods possess rows of suckers that give the animal the ability to hold on to both prey and substrate. These suckers are found on the ventral (underside) surface of the arm. Octopus use the suckers on their arms to hold fast to rocks and plants. The suckers provide such a strong hold that it is impossible to remove a large octopus from a surface to which it has a solid hold. Octopus also "walk" along the bottom by attaching and releasing their suckers as they move fluidly over the bottom.

In Loligo, the arms contain suckers over their entire length. The tentacles contain suckers only on the ends of the tentacle where the limb expands to form a pad. When pursuing prey, Loligo and many other cephalopods will rapidly extend the tentacles to snare their victim, capturing it with the suckered portion of the tentacle.

Each sucker can be controlled individually by the brain. Most species of cephalopods possess suckers that are attached to the arm or tentacle by a stalk. The sucker itself is a cup-shaped bowl of muscle. Many suckers are lined with small teeth or hooks that provide a greater hold on slippery prey like fish. The suckers and accompanying teeth vary greatly in size and shape amongst squid and in some species the teeth are very large and the suckers greatly reduced. Some species have retractable claws like a cat.

Cephalopods feed with a tongue-like radula and a large pair of powerful beaklike jaws located in the buccal cavity at the center of the arms. The beak can bite and tear off bits of tissue that are then pulled into the cavity by the radula. Some species of cephalopods have glands that empty into this cavity and at least some of these secrete venoms and/or digestive enzymes.