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[Oyster Anatomy Laboratory]

Materials:

Aquarium and supplies
  (see Aquarium Set-Up)
Live oysters and paired oyster valves
Dissecting tray or metal pie pan
Oyster knife

 

Sturdy gloves
Stereomicroscope
Large magnifying glass
Dissecting kit
Paper towels

    

Procedure

Internal Anatomy: Observation and Investigation

If your salivary juices are not flowing by now, then get your creative juices working. For centuries people have been devising ways to get the "meat" out of the oyster. These techniques are referred to as "shucking."

.
 11. Describe or sketch different methods you might use to shuck an oyster.

If you would like to open your own oyster try the method below, otherwise have your teacher shuck the oyster for you.

Hinge Method

Step 1: With your gloved hand, firmly hold the posterior end of the oyster against a hard surface. Make sure that the right valve is facing up. Using an oyster knife with a short blade, insert it into the hinge (Figure 8).

Step 2: Rotate the knife until the pressure pops the hinge (Figure 9).

Step 3: Move the knife around the upper edge of the right valve until the adductor muscle is felt -- sever it. Place the right valve off to the side (Figure 10).

CAUTION: Never hold the oyster in your hand while shucking it.

Orient your specimen so that the anterior end is pointed away from you. The dorsal and ventral sides of the oyster are determined by the internal anatomy. The dorsal side of the oyster is on your left, which is the location of the rectum and anus. The ventral side of the oyster is on your right, which is the location of the gills and mouth (Figure 11).

The mantle is a thin layer of tissue that lines the inner part of each valve. It contains glands that extract elements from the water and convert them to compounds that make up each valve. Calcium carbonate makes up about 98 percent of each valve, this is the same material used to make chalk.

[mantle video]

 View a 6 second video (1.6 MB, requires the free Quicktime plug-in which can be downloaded at: http://www.apple.com/quicktime/download/).

Using a stereomicroscope observe the tentacles around the edge of the mantle (Figure 12).

[tentacle video]

 View a 10 second video (2.7 MB, requires the free Quicktime plug-in which can be downloaded at: http://www.apple.com/quicktime/download/).

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12. What is one function of the tentacles?
Capturing food     Locomotion     Sensory reception     Defense mechanism     Clear your answer

.
13. To what stimuli do you suppose they are responsive?
Light     Vibration     Salinity     Temperature
All of these     None of these     Clear your answer

Carefully fold back or cut the mantle on the ventral side.
Figure 13 - Sliding a probe underneath the mantle.
Figure 14 - Lifting the mantle.

Directly underneath the mantle are the gills. The gills are the largest organ of the oyster (Figure 15). Each gill consists of two folds of tissue. There are two points of attachment.
Figure 16 - one of the two points of attachement.
Figure 17 - The other point of attachment.

[gill video]

 View a 10 second video (2.7 MB, requires the free Quicktime plug-in which can be downloaded at: http://www.apple.com/quicktime/download/).

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14. How many gills are there?
2     4     6     Clear your answer

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15. What are the functions of the gills?
digestion     gas exchange     producing new shell     moving water    
digestion & gas exchange     gas exchange & moving water     moving water & producing new shell     Clear your answer

.
 16. Locate the two points of attachment for the gills.

The water which crosses the gills merges into the epibranchial chambers, then into the cloacal chamber which leads to the environment. Identify these structures by lifting the mantle at the posterior end and pulling it back over the adductor muscle.

The adductor muscle, which contains two types of fibers comprising the translucent and white portions, is located toward the posterior end and is below the visceral mass. The weight of this muscle accounts for 20-40 percent of the soft tissue weight of the oyster! You know about its strength if you tried to open a living specimen (Figure 18).

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 17. Locate the adductor muscle.

For the next parts of the laboratory it is desirable to remove the right (top) mantle. Cut carefully around the adductor muscle and at the point of attachment to the body and remove it (if you need help, go back to the instructions and look at Figure 13 and Figure 14).

The heart lies in the pericardial cavity anterior to the adductor muscle.
Figure 19a - The heart in the pericardium.
Figure 19b - Exposing the heart.
Figure 19c - The heart with the pericardial covering removed.
Figure 19d - Close-up of the heart.

.
 18. Locate the heart.

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19. How many atria are present?
1     2     3     Clear your answer

.
20. How many ventricles are present?
1     2     3     Clear your answer

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21. Do oysters have an open or closed circulatory system?
Open system - An open circulatory consists of veins, arteries and sinuses or open cavities.
Closed system - A closed circulatory consists of veins, arteries and capillaries.
open     closed     Clear your answer

Bonus: How does the oyster heart and circulatory system compare to your heart and circulatory system?

With the mantle removed follow the pathway of the digestive organs.
Figure 20 - Locating the digestive gland.
Figure 21 - Locating the labial palps, mouth, rectum and anus.

.
 22. Locate the following structures (Figure 22):
  • Labial Palps
  • Mouth
  • Esophogus
  • Stomach
  • Digestive Gland
  • Intestine
  • Rectum
  • Anus

[Introduction] [External Laboratory] [Internal Laboratory] [Aquarium Set-up] [Glossary]
[Bibliography] [Teacher Resources 5E] [Acknowledgements]

This page was last updated on April 20, 2000

This page is part of the Maryland Sea Grant Oyster web site.

For more information, report problems or provide comments,
please contact:

Maryland Sea Grant
0112 Skinner Hall
College Park, MD 20742
Phone: (301) 405-6379
Email: mdsg@mdsg.umd.edu
Web: www.mdsg.umd.edu

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