Phylum Arthropoda, Subphylum Chelicerata

• Chelicerae are pointed appendages which are used to grasp food

• Subphylum Chelicerata includes sea spiders (class Pycnogonida) and arachnids (class Arachnida)!

Horseshoe Crabs

• Horseshoe crabs belong to class Merostomata (“thigh mouth”)

• Appendages used for feeding at one end, and for swimming/locomotion at the other

• Critically important in coastal marine food webs– Why?

© Steffen Foerster Photography/ShutterStock, Inc.

Horseshoe crabs

• Oldest record of horseshoe crab fossils date back 450 million years ago

• Horseshoe crab blood contains hemocyanin to carry oxygen; blue

• Blood contains amebocytes which release a clotting factor when exposed to bacteria– Used to detect

contamination in medications

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