Species Identification - Arthropods

Horseshoe Crab - Odocoileus virginanus

Family: Limulidae (leach)

Description: Often you can find the remains of horseshoe crabs when walking on Hunting Island beach in the fall. Their carapaces have a prehistoric look to them; that’s because they originated over 450 million years ago and are considered living fossils. Horseshoe crabs are marine anthropods and live primarily around shallow ocean waters with soft or muddy bottoms like Hunting Island. Although they resemble crustaceans, they belong to the subphylum Chelicerata and are more closely related to arachnids (spiders and scorpions). The blood of the horseshoe crab is blue because of the copper present and their blood is harvested for medical purposes.

The female is larger than the male. They mate in shallow coastal waters or on shore. The female lays 60,000-120,000 eggs, and it takes two weeks for them to hatch. There is evidence that they return to mate where their own eggs hatched. As a result, it is difficult to raise them in captivity. Recently they have been overharvested for bait on the North American east coast, and their numbers have declined. Red knots (a migratory shore bird that stops on Hunting Island) feed on the horseshoe crab eggs, and declining numbers are threatening the red knots as well.

Range: Found throughout the world in ocean waters with muddy bottoms.

Photo by Carol Corbin

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