External Anatomy: Observation and InvestigationMaterials:
This activity uses:
ProcedureAn oyster is composed of shells called valves. When working with the oyster, be careful — some edges of the valves can be very sharp (Figure 1). The oyster is more pointed at one end. This is the anterior end — called the umbo (Figure 2). The umbo is the oldest part of the oyster. The posterior end is the larger, curved end — called the bill (Figure 3). The height of the oyster is the distance from the umbo to the bill (Figure 4).
Observe the size of the two valves and how they fit together (Figure 5). 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 (Figure 6). 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.
Separate the two valves to expose the internal surfaces (Figure 7). On the inside 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 (Figure 8). Take A Closer Look On the inside of surface of the right valve you may see a small indentation no bigger than the head of pin. (Figure 9). This indentation is the scar from the Quenstedt muscle.
Flip the two valves over to expose the external surfaces of the valves (Figure 10). The oyster reef is home to a number of different organisms. How those organisms utilize the oyster reef can have a lasting impression on an oyster.
Common examples of artifacts left behind:
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