How to Dissect Earthworms
- 1). Study the diagram of the internal and external features of an earthworm.
- 2). Place the earthworm in the dissection pan and observe its external features. Locate the annelid's anterior (head) and posterior (tail). The clitellum, an obvious swelling on adult worms, will be closer to the anterior. The anterior also can be distinguished as being thicker than the tail. Count the segments along the body and notice their pores and tiny hairs called setae.
- 3). Flip the worm over so that the bottom, or dorsal side, is facing up. Make a shallow incision with a scalpel starting at the anterior and stopping at the midpoint of the body.
- 4). Use forceps to gently open each side of the epidermis (skin) that was cut. Pin the skin to the dissection tray.
- 5). Repeat the process with the second half of the worm's body.
- 6). Identify the various internal organs such as the esophagus, gizzard, crop, five hearts, intestine, ovaries, testes and ventral nerve cord. Use the diagrams to help identify the organs.
- 7). Draw sketches of the earthworm's exterior and interior. Label all parts and, with the help of your text book, describe the role each feature plays.
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