Oyster Anatomy Laboratory

External Anatomy: Observation and Investigation


Materials

This activity uses:

  • A set of valves from an oyster in which the animal has been removed
  • Stereomicroscope (optional)
  • Large magnifying glass (optional)

Navigate with the arrows below.

Procedure

An oyster is composed of shells called valves. When working with the oyster, be careful — some edges of the valves can be very sharp!

How many valves are there?

What general name is given to a mollusk with this many valves?

Anterior

The oyster is more pointed at one end. This is the anterior end — called the umbo. The umbo is the oldest part of the oyster.

Posterior

The posterior end is the larger, curved end — called the bill.

Height

The height of the oyster is the distance from the umbo to the bill.

Determine the height of your oyster (1 in = 2.54 cm).

Side View

Observe the paired valves from the side.

Are the valves different in size?

The shorter of the two valves is the right valve. Notice how the umbo end of the longer valve, the left valve, extends beyond the umbo end of the right valve.

Note: Typically, the right valve of an oyster will be shorter and less concave than the left valve. However, since the size and shape of an oyster can be influenced by its environment, observing the umbo end of the oyster is the most reliable way of differentiating between the right and left valves.

Locate the right and left valves.

Interior View

Separate the two valves to expose the internal surfaces.

On the internal surface of the valves you will observe a dark area. This is the scar from where the oyster's adductor muscle was attached to the valves view.

What is the function of this muscle?

Take A Closer Look

On the internal surface of the right valve you may see a small indentation no bigger than the head of pin.

This indentation is the scar from the Quenstedt muscle.

Exterior View

Flip the two valves over to expose the external surfaces of the valves.

Layers

Oysters build their shells in layers.

view