Opening an oyster.

Oyster Anatomy Laboratory

Internal Anatomy: Observation and Investigation


For Lab:

  • Oyster knife
  • Sturdy gloves
  • Dissecting kit
  • Artificial saltwater (10-15ppt)
  • Computer access

Per Lab Group:

  • Live oysters
  • Shallow glass or plastic dishes (min 2” depth)
  • Probes
  • Forceps
  • Computer access
  • Internal Anatomy Handout (1 per student)
  • Stereomicroscopes (optional)
  • Large magnifying glasses (optional)

Navigate with the arrows below.


For centuries people have been devising ways to get the "meat" out of the oyster. These techniques are referred to as "shucking."

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

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

See hinge method.


Orient the oyster 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.

Quenstedt Muscle

Take A Closer Look: Examine the surface of the oyster body. If you carefully shucked the oyster you may be able to see the small Quenstedt muscle. This muscle is proposed to be a foot (pedal) remnant from the larval form of the oyster. It was named after a German geologist and paleontologist Friedrich August von Quenstedt.


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.


If available, use a stereomicroscope or magnifying glass to observe the tentacles around the edge of the mantle.

What is one function of the tentacles?

To what stimuli do you suppose they are responsive?

Viewing the Gills

Carefully fold back the mantle on the ventral side.


Locate the two points of attachment for the gills.
Click buttons to view images.

Gills Anterior point of attachment Posterior point of attachment.

How many pairs of gills are there?

What are the functions of the gills?

Adductor Muscle

The adductor muscle is composed of two types of fibers - translucent and white and is located toward the posterior end of the oyster. The weight of this muscle accounts for 20-40 percent of the soft tissue weight of an oyster! You know about its strength if you have ever tried to open a live oyster.

Locate the adductor muscle.

Digestive System: Labial Palps

Next follow the pathway of the digestive system. An oyster's digestive system consists of labial palps, mouth, esophogus, stomach, digestive gland, intestine, rectum, and anus.

There are two labial palps, one associated with each gill. Each are bilobed, ciliated and function to sort and transfer food from the gills to the mouth and remove inedible particles and organisms known as pseudofeces.

Locate the labial palps.

Digestive System: Digestive Gland

Food is then passed from the mouth through a short esophogus to the stomach. The stomach is surrounded by the digestive gland that is the site for enzyme production and intracellular digestion.

Locate the digestive gland.

Digestive System: Rectum and Anus

From the stomach undigested and digested materials are passed to the intestines where absorption of nutrients and further processing of wastes occurs. Waste products are passed onto the rectum exiting out the anus.

Locate the rectum and anus

oyster on a half shell

Oyster Anatomy

Locate the following structures by mousing-over the titles below:

  • Mantle
  • Gills
  • Labial Palps
  • Digestive Gland
  • Rectum & Anus
  • Heart
  • Adductor Muscle
  • All

Hinge Method

  • Step 1: Place the oyster left value down on a hard surface with the umbo pointing toward you. Firmly hold down the oyster with a gloved hand.
  • Step 2: Insert the oyster knife in the hinge of the oyster.

Hinge Method

  • Step 3: Rotate the knife until the pressure pops the hinge.

Hinge Method

  • Step 4: 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.

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

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