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Squid Dissection Lab
Can you identify a squid’s structures and their functions?
Squid are made of smaller parts which are organized by shape and purpose. These layers of organization include cells, tissues, organs, organ systems, and
the whole organism. Squid Background The squid is one of the most highly developed invertebrates. Some of the animal’s structures show the ways in which
the squid has adapted to life in the ocean. Its streamlined body and “jet propulsion,” which occurs as the squid squeezes water out of its body through its
siphon, make the squid a fast, active predator. This animal also has a very good defense mechanism. Squid produce a dark ink that they use to escape
from predators. When a squid is startled, the ink is released through the anus, and the cloud of inky water confuses the predator while the squid swims
away.
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! Squid have a
soft body which has a special covering called the mantle, which encloses all of the body organs such as heart, stomach, and gills. Squid have ten arms, which
are wrapped around the head. Eight are short and heavy, and lined with suction cups. The ninth and tenth are twice the length of the others, and are called
tentacles. Suction cups are only on the flat pads at the end of the tentacles. 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 to the mouth so it can be swallowed whole. Squid are an important part of the ocean food web. Squid are a major food source for many fishes, birds
and marine mammals. They are also gaining popularity as a food source for humans around the world. Overfishing is a growing concern because there are
no regulations on squid harvesting. Squid are seined commercially at their spawning grounds. About 6,000 metric tons are taken yearly for human food and
bait. After mating, a female squid will produce 10-50 elongated egg strings, which contain hundreds of eggs each. 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. Southern California squid populations spawn mainly in the winter (December to March).
Materials
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goggles
whole squid (Loligo opalescens)
dissection scissors & utensils
dissection tray
 paper towels
Objective
• To learn the complementary nature of the squid structures and its functions (purpose)
• To understand the role that dissection plays
• To develop a sense of responsibility and respect for the animal that you are using as
a learning tool.
Virtual Dissection
Want to prepare for the lab by completing a virtual dissection first?
Check out this link: http://www.biologycorner.com/worksheets/squid_virtual.html
External Anatomy
Read and complete each step below. When you have COMPLETED the step, check the box!
1. Locate the water jet. The water jet is found on the ventral side of the squid.
2. Find the two large eyes on the side of the head.
3. The tentacles (long) and arms (short) are attached to the head of the squid.
4. Each arm has sucker disks, count the number of sucker discs on one arm: ______
5. Squid have 8 arms and 2 tentacles. Find the arms and describe how the suctions cups are arranged. Are they found on all eight arms? Describe.
6. Are they found on both tentacles? Describe.
7. How does the anatomy of the suction cups help with the physiology of the suction cups? (How does the way the suction cup looks help with the way it
functions?)
8. Measure one of the arms and one of the tentacles. Record this measurement in centimeters. Arm: _________ Tentacles: ________
9. What is the anatomical difference between an arm and a tentacle?
10. Open up the arms and remove any that are in your way. Deep in the middle of the arms is the mouth and a beak-like jaw. These are located in a bulbous
structure called the buccal bulb. Use forceps to remove the bulb and then the jaw (beak).
11. Draw the beak in the box.
12. After examining it describe what you saw and how it moved.
13. Locate the body, which is covered by the mantle, and locate the two fins.
14. The fins are important for stabilizing and steering the squid. Measure the width of a fin in centimeters and record it.
15. List two locomotives (things that transport people) that have the similar anatomy as these fins. Fin: _________
16. Chromatophores are the cells that can change color. They are used to communicate with other squid. Find the chromatophores and record their
color(s). Color: _________
Internal Anatomy
1. Procedure: Turn the squid ventral side up. 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. Be sure and KEEP THE SCISSORS LIFTED so as not to cut into the internal organs of the squid. 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. The muscular mass that surrounded the beak can be pulled up
(and out) to show the tube that is the esophagus.
3. To find the stomach, follow the esophagus toward the posterior.
4. 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.
5. Locate the gills, these are feathery structures that may be hidden under other things, there are two of them.
6. Describe what the gills look like.
7. Follow the gills toward the interior to find an enlarged structure at their base: this is the gill heart.
8. All the way toward the fin is a whitish or yellowish structure: this is the gonad. The male gonad is generally white, the female gonad is usually more yellow
to clear. Is your squid male or female? ____________________
9. Find the siphon. It looks like the open end of a balloon. This tube squirts out water so that
the squid moves like a jet. Open the siphon and measure the diameter of the siphon in
centimeters. Siphon: _________
10. Flip the squid around so the mantle and chromatophores are showing.
11. The hard shell-like structure that lies along the backside of the squid is the pen. See if
you can remove the pen in one piece. The pen serves to stabilize the squid while it
swims (like our backbone).
12. This is the evolutionary remains of a shell. Cut out the pen. Describe what the pen looks
like.
13. Measure the pen and record its length in centimeters. Pen: _________
14. Find the ink sac, this is a small dark sac near the water jet. Remove the ink sac and use
your dissecting needle to break the pouch. Squeeze a bit of the ink out and try and write
your name in the box to the right by dipping the pen into the ink sac.
15. How does the ink compare to the ink in your pen? Use the internal anatomy descriptions
to help you label the squid diagram!
Post-Lab Questions
1. What characteristics do mollusks share?
2. What other organisms are in the same phylum?
3. What makes squids unique from other mollusks?
4. What organ systems and organs does a squid have that a human also has?
5. Explain what organs and organ systems and how they are similar and different.