For people who live near or walk along the Delaware Bay beaches, the horseshoe crab is a familiar site. In fact, the Delaware Bay is the largest spawning ground in the world for horseshoe crabs. Up and down the coast–from Rehoboth Beach to Lewes, Dewey Beach to Bethany Beach, this prehistoric-looking creature is not only interesting to look at, it also plays a critical role in protecting your health.
The horseshoe crab (Limulus polyphemus) is not a crab at all; it belongs to the phylum of arthropods and has its own class called Merostomata, which means “legs attached to the mouth.” Horseshoe crabs are most closely related to creatures called trilobites that lived 544 million years ago.
Horseshoe crabs are important for human health
Although the origins of the horseshoe crab may be prehistoric, they have come into their own in modern times. The crabs have a bluish blood that has proven important in the pharmaceutical industry. An extract of the blood is used to help ensure that products of the drug and medical device industries (e.g., intravenous drugs, vaccines, medical devices) are free of bacterial contamination.
The eyes of the horseshoe crab—of which it has ten—have been the subject of intensive research, including that of Dr. H. Keffer Hartline, who received a Nobel Prize in Physiology or Medicine for his research with the horseshoe crab showing how the retina helps the brain to interpret visual clues. Hartline’s work has helped scientists better understand diseases that affect the vision of humans, including retinitis pigmentosa, which can eventually result in blindness.
During the winter months, beachcombers can see the remains of horseshoe crabs washed up on the beaches. Then in May and June, you may see the creatures in action, as the crabs spawn and the females lay their eggs—up to as many as 20,000—which serve as a ready food supply for migrating shore birds.
Those horseshoe crabs that get past the birds’ eager beaks may go on to eventually become adults and possible candidates for the “bleeding” process. The crabs are collected either by hand in shallow water or with a dredge in deeper waters. The crabs are then transported to a lab, where up to one-third of the animal’s blood is removed, and they are then released alive back to the wild.
Efforts are being made to protect the horseshoe crabs, whose populations are declining because of overfishing, use of the crabs as bait, and loss of habitat. A loss of the horseshoe crab would be tragic—for the creatures themselves, the birds that depend on them for food, and for the health of people everywhere.