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Open Versus Closed Circulatory System: Dissection of the Crayfish and Earthworm

Shana McAlexander
Product Developer

earthworm dissection

Earthworm anatomy.
Click diagram to enlarge.

crayfish anatomyCrayfish anatomy.
Click diagram to enlarge.

This activity introduces students to the anatomy and physiology of an open circulatory system and a closed circulatory system through dissections of a crayfish and an earthworm. Each dissection takes about 15 to 20 min in this activity designed for high-school-level students.



Use this activity only in accordance with established laboratory safety practices, including appropriate personal protective equipment (PPE). Perform dissections on dissecting trays or pans to contain specimens and fluids. Be careful when using sharp instruments such as scalpels, forceps, teasing needles, and scissors. Have students wash their hands after handling any specimens.


There are 2 broad types of circulatory systems, open and closed. An open system is characterized by a tube or sac-like heart that pumps a circulatory fluid called hemolymph to different regions of the organism. Hemolymph contains both blood and lymph, a fluid that bathes the cells. In a closed circulatory system, blood remains separate from lymph. The heart pumps blood and plasma through large vessels to progressively smaller ones where materials such as oxygen and nutrients diffuse into the tissues of the body and waste gets transported out.

Teacher preparation

  • Make a copy of the dissection guides for each student or student group.
  • Set up dissection stations for each group. Each student should have appropriate PPE: gloves, lab aprons, and safety glasses or goggles. Each group should have dissection guides, a crayfish, an earthworm, dissection tray, tools, and pins.

Teacher procedure

  1. Discuss the differences between open and closed circulatory systems and hand out copies of the dissection guides to each student or student group. Discuss basic anatomical terms such as dorsal, ventral, anterior, and posterior.
  2. Instruct your students to dissect the specimens according to the instructions in the Carolina™ Crayfish Dissection Guide and the Carolina™ Earthworm Dissection Guide. For further dissection details and illustrations, I recommend purchasing the Crayfish Dissection BioKit® and Earthworm Dissection BioKit®.