Download Squid dissection

Name _____________________________ Period ____Date _________________
Squid Dissection
Background information:
Squid are cephalopods which is Greek for ‘head foot’. They have a mantle with 2
fins, 8 arms and 2 tentacles (used for grabbing prey).
They move by jet propulsion, allowing water into their mantle and forcing it out
through their siphon. They use their siphon and fins to make quick changes in
direction.
They have three hearts: one for their body systems and two gill hearts; one
located at the base of each gill pair so that they can pump oxygen to their
muscles quickly, thus enabling them to swim fast.
They feed at night in schools near the surface, eating plankton, fish, other squid,
and crabs.
Their predators are penguins, other squid, eels, toothed whales, seals, jellyfish,
fish, and humans. Giant squid live very deep in the ocean and are eaten by
sperm whales.
For defense, they can squirt out a cloud of ink, change color to match their
surroundings, make a jet propelled escape, maneuver quickly, or bite with their
beak.
Materials:
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1 squid per group
scissors
water and paper towels for clean up
1 dissecting tray per squid
1 dissecting probe
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Procedure:
External Anatomy:
1. Locate the siphon. The siphon is found on the ventral side of the squid
between the two eyes.
2. The tentacles and arms are attached to the head of the squid. Locate and
compare the two. Examine the suckers on the end of the tentacles.
3. Find the two large eyes on the head of the squid.
4. Locate the body, which is covered by the mantle, and fins. The body is
covered by tiny spots known as chromatophores that can change color & allow
the squid to camouflage itself.
5. Spread apart the tentacles and use a probe to locate the mouth at the base of
the tentacles. The beak can be felt inside the mouth and is a dark color.
Label the following parts on the squid diagram below. (siphon, tentacles,
arms, eye, mantle, fins, beak & head)
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Questions
1. How many arms does the squid have? How many tentacles?
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2. Based on the structure of the arms and the tentacles, describe how their
purposes might differ. What do the arms do and what do the tentacles do?
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3. What is the function of the siphon?
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4. If water shoots out the siphon to propel the squid in the water, which
direction does the squid swim; head-first, or tentacles-first?
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5. Name two features that are adaptations for the squid’s predatory life.
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6. Name two traits that the squid shares with other mollusks.
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7. What specialized cells allow squid to blend in with their surroundings?
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Procedure:
Internal Anatomy
1. Turn the squid ventral side up. Lift the mantle up above where the siphon
is; it should be loose and easy to pull up. Use scissors to make one long incision
from the bottom of the mantle, above the siphon, to the tip of the mantle next to
the fins. Open the mantle to expose the structures inside.
2. Find the esophagus, this is best found by looking into the mouth and seeing
where it leads, use a probe to carefully poke into the mouth.
3. To find the stomach, follow the esophagus toward the posterior end of the
squid.
4. Locate the gills, these are feathery structures that may be hidden under other
organs, there are two of them on each side for a total of four.
5. Follow the gills toward the interior to find an enlarged structure at the base of
each gill, this is the gill heart.
6. All the way toward the fin is a whitish or yellowish structure, this is the
reproductive gonad. The male gonad is generally white; the female gonad is
usually more yellow to clear & may contain eggs.
7. Find the hard point at the end 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. The pen is the only remains of an ancient shell found in cephalopod
ancestors. The pen supports the mantle & is a site for muscle attachment.
8. Find the ink sac; this is a small dark, silvery sac near the siphon. BE CAREFUL
AS THE INK WILL STAIN YOUR CLOTHING!
9. (Optional) if you can extract the pen, you may carefully dip it into the ink sac
& write your initials in the box below, be careful because the ink will stain!
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Use the diagram below to assist you in locating the following organs in your
squid: ink sac, fins, gonad, gills, mantle, arms, tentacles, siphon, gill heart
A. cecum
B. fins
C. gonad
D. vena cava
E. gill heart
F. gills
G. ink sac
H. siphon
I. tentacles
J. arms
K. eye
L. intestines
M. penis (male only)
N. mantle
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Questions
1. Is your squid a male or female? How can you tell?
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2. How many gills does the squid have?
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3. How many hearts do squid have?
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4. What is the difference between these hearts?
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5. Squids have evolved and no longer have a true shell. What structure is the
only remains of their shell & what is its purpose?
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