How Do Squids Squirt Ink?

Squids are mollusks that eat meat and belong to the same animal kingdom class as the octopus. Squids closely resemble octopuses in that they both have large heads and eight arms that contain suction cups that help them move. Squids, like octopuses, secrete an inky, black mucous from their bodies to disorient animals that may seek to eat them. This inky discharge helps the squid survive in its habitat.

  1. Anatomy

    • Squids have long upper bodies called mantles that contain its mouth, tongue and beak. Within their upper bodies, squids have a stomach, esophagus, anus and siphon that allows them to produce jets of water from their bodies to propel themselves through the ocean.

      Two tentacles and eight hooked and suction-cupped arms are attached to the mantle and help the squid grab and draw prey into its mouth. Also attached to the mantle is an elongated mucous sac that produces the ink.

    Ink Sac

    • The elongated ink sac is located near the siphon and anus of the squid. The ink produced within the sac is composed of melanin, the same color pigments that determine skin color and darken to produce freckles and tans in humans. Melanin gives the inky discharge its dark color, but it is mucous created by the squid's ink sac that lubricates the melanin in order to produce the liquid secretion.

    Function

    • The inky secretion is produced and expelled from the body to help squids disorient and escape from predatory sea life. The ink creates a dark cloud in the water that predators cannot see through. The predator will become confused or scared and retreat while the squid is free to make a covered getaway. The ink also may irritate the eyes or skin of some predators.

    Expulsion

    • When a squid senses trouble from predators, it will secrete the ink, then immediately propel a jet of water from its siphon to disperse it and make the ink cloud larger. This propulsion of water and ink is achieved by intentional muscle contractions, much like humans purposefully contract their muscles to move various body parts, such as the arms and legs.

    Considerations

    • Some squids can produce a substance from their bodies that is poisonous to paralyze their predators or prey. However, this substance is not the ink produced in the squid's ink sac, as this ink is edible and many humans consume the ink as part of many exotic dishes.