Horseshoe Crab
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Horseshoe crab are a familiar sight to anyone who visits Atlantic Coast beaches. Despite the name, most visitors quickly learn that they are not crabs, rather, they belong to a small separate class of animals (Merostomata) in the arthropod phyla.
Four Limulus species exist, Limulus polyphemus, or the Atlantic Horseshoe crab resides along the East Coast of the United States. Three additional species live along the coastal areas of Southeast Asia.
Although they have physiologically evolved over the course of their existence, scientists suggest that Horseshoe Crabs have retained the same general physical attributes and lifestyle for close to 450 million years.
Consider the fact that once a Horseshoe Crab rested on a beach and saw a dragonfly with a three foot wing span fly by, or saw a dinosaur walk by. Today dinosaurs exist only as fossilized exhibits and dragonflies exist with three inch wingspans. Still, the Horseshoe Crab live on.
Its longevity can be attributed to a variety of factors, including a simple design and adaptable lifestyle. Their hard shell or carapace protects them from predators. They have always lived shallow waters and have been able to adapt to their changing environment, such as water temperature and salinity levels. In extreme circumstances, their mobility allowed them to relocate to more suitable habitats and their physiology allowed them to go without food for extended periods of time.
When they do eat, their diet consists of a variety of benthic animals such as worms and mollusks.
Populations came under stress due to a variety of factors including their use in the medical industry and their use as bait for the whelk and eel fisheries. In the early 2000s, a Horseshoe Crab sanctuary was established close to the Delaware Bay estuary to promote their conservation.
© 2009 Patricia A. Michaels