Mussel Dissection Life Science, Mr. Ditolla

Mollusks Many mollusks such as oysters, clams, and snails have hard outer shells. Other mollusks such as squids and octopuses have rodlike supports within their bodies. Most mollusks live in the sea or in freshwater, but some species are found on land. Whether they have a shell or not, all mollusks have a soft body.

Shell The mussel shell is made up of two sides, each side is called a valve. The valves are hinged together on one side of the mussel, but can open along the other side. When the shell is closed, the valves are held together by two powerful muscles. You cannot open the shell with your scissors so I will come around and open it with a knife by cutting through both muscles. valve

Shell Structure Using the picture below, identify the parts of the shell on your mussel. umbo growth ring hinge

Locate the thin mantle layer on the inner surface of each valve. This layer develops the shell and coats the shell’s inner surface. The space within the folds of the mantle layer is the mantle cavity. mantle mantle cavity

Locate the gills. The mussel breathes with its gills by removing oxygen from the water. gill

Locate the muscle that I had to cut through to open your mussel shell. This muscle contracts to close the shell. Some mussels have one of these muscles, others have two. muscle

Using the tweezers, remove the mantle layer from one of the valves. Notice the smooth, fine-grained inner surface of the valve. This shell lining is called the mother-of-pearl. remove this layer mother-of -pearl

A pearl is formed when a piece of sand or other irritant gets stuck in the mantle layer and irritates the mussel. The mussel then coats the irritant with mother-of-pearl, creating a pearl. mantle layer pearl

Locate the two siphons. Water enters the mantle cavity through one siphon and passes out through the other siphon. Mussels are filter feeders and filter out food from the water as it is channeled through by the siphons. siphon

Locate the large, muscular foot. When the mussel is alive the foot extends out through the shell and grips the stream bottom to slowly move the mussel along. foot Locate the body mass located under the foot. body mass

Cut open the body mass and locate the digestive gland, which helps digest food, and the gonads, which produce egg and sperm cells.

Like other invertebrates, mussels do not have a back- bone. Mussels belong to the Mollusk phylum. All mollusks have a soft body. Most mollusks have a shell, and most mollusks have a muscular foot. Wipe your tools off, throw your mussel away, wipe out your tray, and wash you hands with soap and water. Answer the following questions on a separate piece of paper.

Questions and Conclusions: 1. Name three mollusks that have hard, outer shells. 2. Name two mollusks that don’t have shells. 3. Do any mollusks live on land? 4. All mollusks have a soft __________. 5. What is each side of the shell called? 6. What do the muscles in the shell do ? 7. What does the mantle layer do? 8. What is the mantle cavity? 9. How do mussels breath? 10. What is the mother-of-pearl? 11. How are pearls formed? *more questions on next slide

12. What do the siphons do? 13. How do mussels obtain food? 14. What is the function of the foot? 15. What structure is located under the foot? 16. What organs are located inside the body mass? 17. What is the function of the digestive glands? 18. What do the gonads do? 19. Why are mussels classified as invertebrates? 20. What phylum do mussels belong to? 21. Most mollusks have a __________ and a muscular _________. 22. All mollusks have a _______ body.