Download the arms hold the food while the squid bites it into swallowable

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Name ___________________________________________
Period _______
Squid Dissection
arms - eight short limbs, each of which has two rows of suction cups on the lower side; the arms
hold the food while the squid bites it into swallowable pieces.
beak and mouth - the parrot-like beak on the mouth is used for biting food into small pieces. The
beak and mouth are surrounded by the bases of the arms and tentacles.
hooks or sucker rings - the ends of the tentacles, which have toothed suckers.
eye - an organ used to see; squids have two, very large eyes (they are large in proportion to the
size of the body).
tentacles - the two, long tentacles are used for obtaining prey; they have toothed suckers only
near the tip.
fins - two flaps on the mantle that are used to stabilize the squid during swimming.
head - the small part of the body between the mantle and the arms; the head contains the eyes,
the brain, and the muscular buccal mass (which crushes the food).
mantle - the large part of the squid in front of the head; inside the mantle are the stomach, gills,
ink sac, pen, reproductive organs, and many digestive organs.
siphon - a tube-like organ on the lower side of the head; it expels water forcefully, enabling the
squid to propel itself through the sea.
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Squid Dissection
Squid are members of the phylum Mollusca and of the class Cephalopoda.
Cephalopoda is the most morphologically and behaviorally complex class in phylum
Mollusca. Cephalopoda means "head foot" and this group has the most
complex brain of any invertebrate. In this lab you will have the
opportunity to dissect a squid and learn why it is such a successful
invertebrate!
All squid have a soft body with a covering called the mantle, which encloses all of the body organs
such as the heart, stomach, and gills. Squid can be as small as a thumbnail or as large as a house.
The giant squid can measure 60 feet in length and weigh three tons! Squid feed on small
crustaceans, fish, marine worms, and even their own kind. They use their tentacles to quickly catch
their prey, which is pulled in by the arms and down to the radula, or beak, which uses a tongue-like
action to get food into the mouth so that it can be swallowed whole.
External Anatomy:
1. Locate the funnel (also called the siphon or water jet). The funnel is found on the ventral side of
the squid. Cephalopods shoot water out of the funnel to propel themselves through the water.
2. The tentacles and arms are attached to the head of the squid. Tentacles are longer than arms
and are used to catch prey. Locate and compare the two.
3. Find the two large eyes on the head of the squid. Cephalopods have highly developed eyes for
hunting prey.
4. Locate the body, which is covered by the mantle, and fin.
5. Spread apart the tentacles and use a probe to feel inside the mouth. The beak (also called
radula or jaws) can be felt inside the mouth.
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External Anatomy Questions
1. How many arms does your squid have? How many tentacles?
2. Based on the structure of the arms and the tentacles, describe how their purposes differ.
What do the arms do and what do the tentacles do?
3. Draw arrows on the squid below to indicate the direction that water comes out of the funnel and
the direction that the squid moves.
4. Name two external features that are adaptations for the squid’s predatory life. How do these
adaptations help the squid?
1.
2.
5. Do you remember the general traits of mollusks we discussed in lecture? Name two traits that
the squid shares with other mollusks.
a.
b.
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Squid Internal Anatomy
Procedure: Some specimens may be cut already. If so, move on toward the examination of the
specimen. If not, while working on the ventral side of the squid, pull the mantle up with the
scissors where the water jet is, it should be loose and easy to pull up. Use scissors to cut from the
water jet to the fins. Open the mantle to expose the structures inside. The vessels of the
circulatory system have been injected with pink latex. You may want to use dissecting pins to hold
the mantle open so that you can observe the internal anatomy. Identify as many structures as
possible. Some may be missing from a previous dissection.
1. Find the inksac, this is a small dark sac near the water jet. The inksac is located on the liver and
empties out the funnel. The squid will squirt a cloud of ink to get away from predators.
2. To find the stomach, follow the esophagus through the beak toward the posterior. Try cutting
open the stomach to see if your squid had a last meal.
3. The anus empties into the water jet, use scissors to cut the water jet down the center so you
can see the small opening of the anus.
4. Locate the gills, these are feathery structures that may be hidden under other things, there is
a pair of gills on each side of the animal.
5. Follow the gills toward the interior to find an enlarged structure at their base, this is the gill
heart. The gill heart pumps oxygenated blood throughout the lungs and the body.
6. Find the hard point at the end (posterior region) of the fin and gently grip it with forceps pulling
away from the squid. In this way you should be able to remove in one piece the pen. If you’d like,
you can gently pierce the inksac and write with the pen. The pen aids in structural support.
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Internal Anatomy Questions
1. Name two ways the cephalopods are more advanced than the other classes of mollusks.
2. What is the function of the ink sak?
3. What is the function of the pen? What would happen if the squid didn’t have a pen?
4. How does the function of the cephalopod siphon compare with that of the clam’s siphon?
5. How does the siphon action of the squid control the direction and speed of the animal’s
movement?
6. The squid circulatory system if of the closed type and the clam has an open circulatory system.
How do these two circulatory systems differ?
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