Mrs. Taylor
Marine Science
LAB: SQUID DISSECTION
BACKGROUND INFO:
The squid is one of the most highly developed invertebrates. It is in the phylum Mollusca,
which is derived from the Latin word meaning “soft body”. It belongs to the class Cephalopoda,
meaning “head-footed”, because its head is pushed down toward the foot. This class also includes
the octopus, cuttlefish and ancient nautilus.
All mollusks have a soft body with a special covering called the mantle, which encloses all
of the body organs such as heart, stomach and gills. Squid have a large mantle, eight arms with
two longer feeding tentacles all with suckers, a beak and mouth, a siphon, a large head (with a
brain), two large eyes, and three hearts. The tentacles are long and retractable and have suckers
only at the tips. Their large eyes are very similar in structure to people's eyes. The shell has been
reduced to a chitinous pen that is embedded in the upper surface of the mantle.
Squid breathe using gills. They move by squirting water from the mantle through the
siphon, using a type of movement called jet propulsion. They can move both backward and forward
just by changing the direction of the water flow through siphon.
Some of the animal’s structures explored in this lesson illustrate the ways in which the
squid has adapted to life in the ocean. Its streamlined body and jet propulsion make the squid a
fast, active predator. This animal also has a very good defense mechanism.
Squid can change the color of their skin to mimic their environment and hide from
predators. When in danger, squid release a cloud of dark ink from their inc sac in order to
confuse their attacker and allow the squid to escape.
These fast-moving carnivores 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. The esophagus runs
through the brain, so the food must be in small pieces before swallowing. Squid feed on small
crustaceans, fish, marine worms, and even their own kind!
Squid reproduce sexually by releasing eggs into the water. After mating, a female squid
will produce 10-50 elongated egg strings, which contain hundreds of eggs in each string. In many
species, the parents will soon die after leaving the spawning ground. The egg strings are attached
to the ocean floor, are left to develop on their own, and hatch approximately ten days later.
Squid are an important part of the ocean food web. Squid are a major food source for
many fishes, birds and marine mammals. Squid are gaining popularity as a food source for humans
around the world (calamari). However, over-fishing is a growing concern because there are no
regulations on squid harvesting.
Squid can be as small as a thumbnail, or as large as a house. The giant squid,
Architeuthis
, can measure 60 ft. in length and weigh three tons! Southern California squid
populations spawn mainly in the winter (December to March). Squid are seined commercially at
their spawning grounds. About 6,000 metric tons are taken yearly for human food and bait.
