Squid Dissection

Objectives:

• To observe the external and internal anatomy of a cephalopod.
• To compare and contrast tentacle designs of a squid and octopus.
• To write your name in squid ink!
• To examine the squid’s eye

External Anatomy:

1. Locate the water jet. The water jet is found on the ventral side of the squid. 

2. The tentacles and arms are attached to the head of the squid. Locate and compare the two.

3. Find the two large eyes on the head of the squid.

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 jaws (or beak) can be felt inside the mouth. (At the end of the lab you may try to remove the jaws if you have time)

Sketch the external view of the squid, label all the parts that are underlined above. You may want to sketch the mouth and jaws separately. Make sure are the labels are clear. 

Questions

1. How many arms does the squid have? How many tentacles?

2. Based on the structure of the arms and the tentacles, describe how you their purposes differ.  What do the arms do and what do the tentacles do?

3. What is the function of the waterjet? If water shoots out the water jet to propel the squid in the water, which direction does the squid swim-head first, or foot first?

4. Name two external features that are adaptations for the squids predatory life.

5. Name two traits that the squid shares with other mollusks.

Internal Anatomy

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.  Open the mantle to expose the structures inside.

1. Find the inksac, this is a small dark sac near the water jet.

2. Find the esophagus, this is best found by looking into the mouth and seeing where it leads, use a probe to poke within the mouth.

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.

4. Locate the gills, these are feathery structures that may be hidden under other things, there are two of them on each side.

5. Follow the gills toward the interior to find an enlarged structure at their base, this is the gill heart

6. All the way toward the fin is a whitish or yellowish structure, this is the gonad.  The male gonad is generally white, the female gonade is usually more yellow to clear.

7. Find the hard point at the end of the fin and gently grips it with forceps pulling away from the squid.  In this way you should be able to remove in one piece the pen.

QUESTIONS

Use the descriptions above to label the squid. Use the underlined words above to help you label. 1.  Is your squid is a male or female?  How can you tell? 2.  How many gills does the squid have? 3.  Where does the ink sac empty into and what is its function? 4.  What is the function of the pen? 5.  How do wastes exit the squid?  (be specific)

Analysis:

1. How many tentacles are there?

2. Look at the suction cups. How many tentacles have them?

3. How many tentacles do not have suction cups?

4. Describe how the pen looks and feels.

5. What do you think is the purpose of the pen?

6. Compare and Contrast the tentacles of the squid and the octopus. List 2 difference and 2 similarities.

7. How is the squid’s eye similar to ours?