| Range: |
Waters off the eastern coast of North America |
| Habitat: |
Oceans, estuaries, beaches |
| Conservation Status: |
Near threatened |
| Scientific Name: |
Limulus polyphemus |
The horseshoe crab is a living fossil. It has been on the Earth some 220 million years, longer than dinosaurs. And it survives today almost identical to its ancient ancestors.
It's thought to have evolved from the now-extinct trilobites, which dominated the oceans of the world in prehistoric times.
Despite the name, the four species of horseshoe crabs aren't crabs at all. They are hard-shelled marine arthropods more closely related to spiders than crustaceans. Like all arthropods, they have segmented bodies, jointed legs, and a hard exoskeleton (outer covering). Horseshoes are in a class of their own -- Merostomata -- which means "legs attached to the mouth."
Most horseshoes spend most of the year in deep water. They feed at night, primarily on mollusks and annelid worms. Every spring they migrate to the shallows, emerging from the sea to mate along the beaches on moonlit nights, when the tide is high. They can walk on land on their five pairs of legs, as well as swim on their backs by moving their abdominal plates. Adults can grow up to two feet long.
This particular species of horseshoe crab is common along the east coast of North America (the others live in the seas surrounding tropical Asia). Its eggs are an important source of food for migratory birds, some fish, and numerous sea turtles.
|
