by Ann Marie Froehle

Purpose

Background

Materials / Equipment needs

Lab Procedure

Class Management Ideas

Student Lab Pages

Post Lab

 

PURPOSE

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BACKGROUND:

All Mollusks have a similar body plan, which is divided into three main parts: the foot, visceral mass and mantle.  The foot is usually used for movement; the visceral mass contains most of the internal organs; the mantle is a heavy fold used to secrete the shell.

Three of the classes studied in this lab include:

1. Class Pelecypoda - meaning "hatchet-foot".  These are bivalves, which are mollusks with two shells that are hinged at the mid-dorsal line and drawn tightly together by powerful adductor muscles. They have hatchet shaped bodies (actually called a foot) which they use for digging and anchoring, and are filter feeders.  They include clams, scallops and oysters.

2.  Class Gastropoda – meaning "belly-foot".  These are univalves, which is usually coiled creating a place of retreat for the animal when in danger.  They move along  with a rippling effect on their elongated belly (actually it's their foot).  They have a sharp radula used for grazing on plants or tearing at animal flesh.  Most species are marine, but there are also many freshwater and terrestrial species.  They exhibit torsion, which is a twisting of the body up to 180°, which results in the anus placed above the head!

3.  Class Cephalopoda – meaning "head-foot".  The shell is either reduced and internal (squid) or absent (octopus).  There is one type possessing a shell called the chambered nautilus.   They use tentacles for movement like creeping on the ocean floor and also to capture prey.  In the middle of these tentacles is a powerful beaklike jaw to bite prey.  They are also known for their ability to shoot ink in self-defense, and escape with their jet propulsion movement.

Pictures and information about mollusks (hit OK on the first screen)

 
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MATERIALS / EQUIPMENT NEEDS:

Purchase these items the day before, fresh is best!

• Clams / mussels - 1 - 2 per student; unopened.

• Bay Scallops - the larger ones cook very nicely

• Squid -  entire bodies, or just the tubes will work; depending how you thick you cut the rings, determine about 10 - 12 rings per tube.

• Octopus - see information below on which to order / buy.

• Oysters - due to expense, one or two per lab table

• handlens for observations

For cooking:

• Olive oil or butter
• garlic or some type of seasoning
• onions
• hot plate
• sieve / colander
• various cooking pans, cooking utensils
• paper plates, plastic forks
• crackers (optional)
• sauce (optional)
 

LAB PROCEDURE

Mussels

1.  Obtain and rinse 1 or 2 unopened clams / mussels per student.  (If they are opened they are inedible!)  Pick off the beards.
2.  Add salt to boiling water and put the unopened shells to cook.
3.  After the shell has opened in the boiling water, let cook about 1-2 more minutes.
4.  Drain immediately.  Be careful and use a sieve in case the mussels slide out of their shells.
5.  Serve with the shell.  The students will need to look at both halves of the shell.

Actual Fish Market recipe
 
 

 Scallops

1.  Obtain fresh scallops from the fish department.  Frozen work well also, but I prefer
fresh!  They don't keep very long!
2.  Sauté garlic and fresh chopped onions in olive oil or butter.  (I like butter, so do my thighs!)
3.  Add the scallops and sauté until they become an opaque or white color – about 2 – 3 minutes depending on the quantity.
4.  Serve.  I usually serve on a soda cracker or with some cocktail sauce.

Ohana scallop recipe
 

Squid

1.  You can purchase hollowed or full squid tubes from a fish department.  Due to time and ease, I usually prefer hollowed.  Frozen squid tastes great, but fresh is best!  SAVE ONE OR TWO HOLE TUBES (WITH TENTACLES) FOR STUDENT OBSERVATION!
2. Cut the tubes horizontally to create rings.  They rings will open as they cook.
3. Sauté onion and garlic in olive oil and butter.  Add the squid until they just turn white.  No longer - overcooking will result in a rubbery texture.  Stir constantly, this will take about 2 minutes.
4.  Serve, as you did with scallops.

Octopus

 Fresh octopus can be expensive and hard to find (especially in Minnesota), so ask a local grocery store fish department early and perhaps they can order it.  A Japanese or Sushi restaurant is also a good place to shop (and tastes really good!). Sushi style fresh octopus tastes delicious when served raw.  If this poses a problem, you may want to cook it in the same manner as the squid.  Because of the high price, I often order only one whole octopus for student observations without tasting!  I cut the tentacles in cross-section so they can see the suction cups.  They can also touch the beak, siphon and entire tentacle.

More info on octopus information

Oysters

 Fresh oysters can also be very pricey, and therefore a comparison observation can be used.  Buy at least one for each table of students.  Mussels and oysters make for interesting contrast due to the fact that they are both seen in the natural shells.  At the end of the lab, pry one open to check for pearls!  (in 10 years, kids anxiously check, and have yet to find one)

CLASS MANAGEMENT IDEAS

• Arrange students in groups or at tables so they can try things together and observe shells as a         group.  They have a great time watching each other!
• Prepare the mollusks in the order listed on the student pages, this will prevent confusion.
• Never make a student try something, but do require the non-tasting questions to be answered.
• Have water or soda on hand just in case the taste is more than expected!
• Serve with crackers, sauce or bread.
• Stress vocabulary in the background information.
• Have students sauté the seafood!  They love wearing an apron, and actually do a very good job!
• To conclude the lab, issue the POST LAB.  This could be a quiz or just a check!

STUDENT LAB PAGES

NAME __________________________
 

BACKGROUND

All Mollusks have a similar body plan, which is divided into three main parts: the foot, visceral mass and mantle.  The foot is usually used for movement; the visceral mass contains most of the internal organs; the mantle is a heavy fold used to secrete the shell.

Three of the classes we will be studying include:
 

1. Class Pelecypoda - meaning "hatchet-foot".  These are bivalves, which are mollusks with two shells that are hinged at the mid-dorsal line and drawn tightly together by powerful adductor muscles. They have hatchet shaped bodies (actually called a foot) which they use for digging and anchoring, and are filter feeders.  They include clams, scallops and oysters.

2.  Class Gastropoda – meaning "belly-foot".  These are univalves, which is usually coiled creating a place of retreat for the animal when in danger.  They move along  with a rippling effect on their elongated belly (actually it's their foot).  They have a sharp radula used for grazing on plants or tearing at animal flesh.  Most species are marine, but there are also many freshwater and terrestrial species.  They exhibit torsion, which is a twisting of the body up to 180°, which results in the anus placed above the head!

3.  Class Cephalopoda – meaning "head-foot".  The shell is either reduced and internal (squid) or absent (octopus).  There is one type possessing a shell called the chambered nautilus.   They use tentacles for movement like creeping on the ocean floor and also to capture prey.  In the middle of these tentacles is a powerful beaklike jaw to bite prey.  They are also known for their ability to shoot ink in self-defense, and escape with their jet propulsion movement.

LAB QUESTIONS AND OBSERVATIONS:

1.  Describe the appearance of the rings.  Are there many, few, large, small, far apart, close?

2.  Where would the oldest rings most likely be found?  (close to the hinge or outer edge?) Explain your reasoning:
 
 

3.  If two rings appeared to be very far apart, what could this mean?  (read previous passage if you're lost)

Closely observe the inside of the mussel.  There is possibly a small piece of flesh that is still attached to the shell.  This is part of the adductor muscle.
 

 4. If "ad" means together, what is the most likely function of the adductor muscle?

 

5.  Think about how the mussel looked before it was cooked.  What effect did the boiling have on the mollusk?
 

6.  Describe the appearance of the horny layer.  Include:  color, how it feels, does it easily flake or scratch off?
 
 

7.  Describe the appearance of the pearly layer.  What types of colors are seen?  Is it brittle or strong?  Does it scratch easily?  How does it look compared to your classmate's shells?
 

 8.  Write several things for which the pearly layer of shells is often used.

Oyster:

 9.  How many "valves" are present? (use the background information for a clue.)________

 10.  Notice the horny layer of this shell.  List at least 2 ways it differs from that of the mussel.
 
 

 11.  Gently try to pry it open.  Is it easy or difficult?  Why?  (refer to mussel section!)

Octopus:

 12.  What color is the mantle?

 13.  Describe the appearance of the mantle.  What type of texture does it have?  Is it an even color?  How thick is it?

Octopus use powerful suction cups located on their arms to aid in capturing prey.  Some, such as the giant squid, even have hooks on their suction cups.  Locate the suction cups on the provided cross-section.
 

14.  Approximately what is the diameter of the suction cup?  What is the depth?
 

15.  Draw the shape of the suction cup in cross section.  Use a diagram to indicate how the suction cup works.
 

Squid:

16.  Taste your portion.  Describe its texture and size.

17.  Now look at the uncut squid.  With the aid of your textbook, draw how you believe the squid moves.  Use arrows, and don't forget to include its tentacles and eyes.
 

Scallops:

18.  Scallops are also part of the Pelecypoda class.  Using your knowledge of this class, how many valves does the scallop have?________

 19.  What is the shape and color of your portion?

 20.  After you eat it, describe the texture and flavor of the scallop.
 

 21.  Using your knowledge of bivalves, what part of the scallop were you eating?

REVIEW:

3.  What is the meaning of the term bivalve?

4.  Name one univalve.

5.  What function does the adductor muscle have?

6.  Which term means belly-foot?

7.  What does the term pelecypoda mean?

8.  What is the meaning of cephalopod?

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POST LAB

Check all statements that are true!

_____ 1.  A belly footed animal is also known as an octopus.

_____ 2.  The adductor muscle is used to keep a pelecypod closed tightly.

_____ 3.  In this lab, only the bivalves had adductor muscles.

_____ 4.  A cephalopod is a filter feeder, not a predatory animal.

_____ 5.  The mantle secretes the shell in mollusks.

_____ 6.  Concentric growth rings are found on cephalopods.

_____ 7.  The prismatic layer is found on the outside of the bivalve's shell.

_____ 8.  The cephalopod has suction cups on its tentacles.

_____ 9.  A univalve is also known as a gastropod.

_____ 10.  Cephalopod means head-footed.

_____ 11.  Gastro means hatchet.

_____ 12.  Pod means belly.

_____ 13.  Mollusk means soft bodied.

_____14.  The three parts of the mollusk are the head, body and foot.

_____ 15.  Univalve would mean: having one shell and exhibits torsion.

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