SQUID DISSECTION

Biology Lab – Unit 6

 

The purpose of the earthworm dissection is to provide you with basic dissection experience, as well as to begin an introduction into gross anatomy to be coordinated with your lecture notes.

 

Scientific Classification: Squid belong to the order Teuthoidea of the class Cephalopoda. The common squid of the east North Atlantic coast belongs to the family Loliginidae and is classified as Loligo vulgaris.

 

Objectives:

 

• Describe the appearance of various organs found in the squid.

• Name the organs that make up various systems of the squid.

 

Materials:

 

Dissecting kit and pins, gloves, forceps, lab apron, scissors, paper towel, scalpel, water, dissecting probe, preserved squid, hand lens, dissection tray.

 

Purpose:

 

In this lab, you will dissect a squid in order to observe the external and internal structures of squid anatomy.

 

Background:

 

The squid is one of the most highly developed invertebrates. Some of the animals 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 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.

 

· 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 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 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 a major food source for many fishes, birds and marine mammals.

 

· 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.

 

· 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.

 

Procedure:

 

1. Put on gloves and a lab apron if possible.

 

2. Place squid in the dissecting tray & rinse off the excess preservative. Identify the dorsal side and the ventral side. Turn the squid dorsal side up, as shown in the diagrams.

 

3. Use a hand lens as you observe all parts of the squid, externally and internally.

 

4. Using the attached diagrams, dissect the squid to reveal and explore the various structures and organs.

 

5. Dispose of your materials according to the directions from your teacher.

 

6. Clean up your work area and wash your hands before returning to class.

 

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More detailed information and color photos of the dissection can be found at:

http://biog-101-104.bio.cornell.edu/BioG101_104/tutorials/animals/squid.html

 

The following images are designed to help you review materials you studied in the laboratory. The graphic names and numbers below correspond with circled numbers on your handout.

 

External Morphology

 

dorsal_view

1. This is the squids's dorsal surface.

2. This is the squids's mantle.

3. This is the fin portion of the mantle.

4. This is the collar portion of the mantle.

5. This is an eye.

6. This is one of ten arms.

7.This is one of a pair of tentacles.

 

 

ventral_view

1. This is the squid's ventral surface.

2. This is the squids's mantle.

3. This is the fin portion of the mantle.

4. This is the collar portion of the mantle.

5. This is an eye.

6. This is one of ten arms.

7. This is one of a pair of tentacles.

8. This is the squid's funnel; the equivalent of the clam's excurrent siphon.

9. This is an incision that was made in preparation for injecting the circulatory system of the squid.

 

Funnel Area

 

funnel

1. This is the collar area of the squid's mantle.

2. This is the squid's funnel.

3. This is the squid's eye.

4. The arrows point to the two funnel retractor muscles.

5. The arrow points to the squid's rectum. The two small flaps are called rectal papillae.

6. The left arrow points to one of a pair of cartilaginous ridges in the mantle that fits into grooves on the funnel (right arrow).

 

Internal Anatomy

 

buccal_mass

Note: in the image, the funnel has been removed and the head area bissected to expose the buccal mass.

 

1. The arrow points to a sucker on one of the squid's arms.

2. This is a part of the buccal membrane.

3. This is the buccal mass, a muscular organ with chitinous teeth and a radula for masticating prey to prepare it for digestion.

4. The arrow points to tissues associated with the squid's salivary glands.

5. The arrow points to the esophagus. The tissue surrounding the esophagus is associated with the liver.

male

1. This is the funnel area of the head.

2. The arrow points to the right gill.

3. The arrow points to the left funnel retractor muscle.

4. The arrow points to the squid's rectum.

5. The arrow points to one of the squid's branchial hearts. They receive deoxygenated blood from the precavae and the posterior vena cavae and pump it through the gills.

6. The arrow points to one of the squid's precavae. These vessels containing the kidneys, receive deoxygenated blood from the head area via the anterior vena cava and direct it to the branchial hearts.

7. The arrow points to one of the squid's posterior vena cavae. These vessels receive deoxygenated blood from the mantle area and direct it to the branchial hearts.

8. The arrow points to the squid's caecum, a large chamber receiving masticated food from the stomach. Much of the digestion occurs here.

9. The arrow points to the squid's single testis. Usually, it is partially covered by the caecum.

 

female

1. This is the funnel area of the head.

2. This is the squid's rectum. It is terminated by two ear-like flaps.

3. This is the left funnel retractor muscle.

4. The arrow points to one of the squid's gills.

5. The arrow points to the ink sac. This melanin-containing sac is dorsal to the intestine an empties into it.

6. The arrow points to the squid's pair of nidamental glands. They secrete material that becomes the egg casings.

7. The arrow points to the squid's left branchial heart. They receive blood from the vena cavae and pump it through the gills.

8. This is the squid's ovary. It occupies much of this part of the mantle cavity and covers the caecum.

9. The arrow points to the squid's stomach.