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American (Atlantic) Horseshoe Crab

Limulus polyphemus


  • Jointed carapace (shell) with three sections including a broad “U” shaped head region
  • Spines on rear abdominal region for protection from predators
  • Harmless telson, or tail, used to right them when overturned
  • Ten eyes scattered all over the body including two large compound eyes on top of head section of carapace
  • Has several light receptors near the tail in addition to eyes
  • Five pairs of legs on bottom and no antennae
  • Gills underneath carapace resemble pages in a book
  • Mature adult males first leg is shaped like a hook

Similar Species

Genetically, they are more closely related to spiders and scorpions than to true crabs


Up to 1 foot in carapace width; males are typically one-third the size of females


Atlantic Ocean and Gulf of Mexico; nest on sandy beaches with low wave action.


Known to gather in large nesting aggregations, or groups, on beaches. Horseshoe crabs nest year-round in Florida, with peak spawning occurring in the spring and fall. 

Feeds on various invertebrates

Additional Information

Their eggs are an essential source of food for migratory shorebirds and some fish.

Considered “living fossils” since they haven’t changed much in the past 450 million years.

Recreational harvest: Prohibited
Horseshoe crab research