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The Horseshoe Crab

A True Blue Blood


Kathleen A. Nolan
Department of Biology, Health Promotion, and Health Care Management
St. Francis College


This case study examines the population dynamics of the horseshoe crab, which is sometimes described as a “living fossil.” Students are shown PowerPoint slides that are interspersed with clicker questions about the biology, life history strategies, and economic importance of this declining species. The paleontology of the horseshoe crab, differences between males and females, reproductive strategies, and the importance to the biomedical industry and fishing industries are discussed. After the presentation, students participate in a stakeholder activity in which they role-play the various players involved in the plight of the horseshoe crab, including scientists, medical workers, bird watchers, hotel owners, eel fishermen, shell fishermen and others. Students are asked to reach a consensus on the best way to manage the population of this species. The case, which takes about 80 minutes of class time to complete, has been used in a variety of courses including ecology, marine biology and a freshman honors seminar course titled “Current Water and Sustainability.”


  • Explain the unusual significance of the evolutionary age of the horseshoe crab, and how its general shape and form have been conserved for 450 million years.
  • Classify the horseshoe crab and explain its life history strategies such as mating and spawning, and understand factors about its development, such as frequent molting.
  • Articulate reasons why people "harvest" horseshoe crabs, and synthesize how this can lead to unsustainability of an ecosystem.
  • Hone presentation, negotiation, analytical, and decision-making skills by role-playing a particular stakeholder
  • Begin to formulate management and policy decisions from various stakeholder perspectives regarding the conservation and economic development of horseshoe crab populations.


Horseshoe crab; ecology; sustainability; fisheries management; Limulus polyphemus; living fossil; stabilomorph; biomedical bleeding; Delaware Bay

Topical Areas

Ethics, Policy Issues, Regulatory Issues, Social Issues

Educational Level

High school, Undergraduate lower division, Undergraduate upper division, General public & informal education, Continuing education


PDF, PowerPoint

Type / Methods

Clicker, Directed, Discussion, Role-Play



Subject Headings

Aquaculture  |   Biology (General)  |   Biomedical Engineering  |   Ecology  |   Economics  |   Environmental Science  |   Evolutionary Biology  |   Interdisciplinary Sciences  |   Marine Science / Oceanography  |   Natural Resource Management  |   Paleontology  |   Science (General)  |   Wildlife Management  |   Zoology  |   Developmental Biology  |  

Date Posted


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The following video(s) are recommended for use in association with this case study.

  • Horseshoe Crabs
    This video depicts a lab in Florida that studies vision in horseshoe crabs. It contains excellent photography of the eggs and how the nests are incubated and cared for. Running time: 4:44 min. Produced by ChangingSeasTV, 2014.
  • Horseshoe Crabs Mate in Massive Beach "Orgy"
    This video shows horseshoe crabs en masse in the Delaware Bay both at night and during the day. Facts about their reproduction are explained, as well as a few shots of their blue blood and its importance. Running time: 3:29 min. Produced by National Geographic, 2014.
  • Horseshoe Crab Research by Dr. Anil Chatterji
    This video depicts harvesting horseshoe crabs with nets and artificial insemination of eggs taken from the females. It also shows how the hemolymph is extracted from the horseshoe crab and how the lysate is made to test pharmaceutical preparations for bacteria. Running time: 5:14 min. Produced by Dr. Bugs Tan, 2011.
  • Crash: A Tale of Two Species | Blue Blood
    This video sets the stage for the case in that it presents all relevant issues associated with the horseshoe crab today. It shows how they are in a “tug-of war” with conflicting stakeholders such as eel fishermen, migrating birds, the biomedical industry and others. Running time: 3:16 min. Produced by PBS, 2008.
  • Rendezvous with Horseshoe Crabs
    A seventh-grade science teacher narrates this video that depicts breeding of horseshoe crabs in Delaware Bay. The teacher also explains the importance of the horseshoe crab eggs to the migrating red knots. Running time: 4:49 min. Produced by WHYY, 2011.