Size: Up to 20 inches (51 cm).
Range: In western Atlantic from Maine to Yucatán Peninsula.
The largest population of horseshoe crabs in the world lives in the United States, in the Delaware Bay. The horseshoe crab is one of the Earth's oldest creatures, appearing over 100 million years before the dinosaurs! While called "crabs," they are more closely related to spiders and scorpions. Although the horseshoe crab's sword-like tail may look dangerous, this animal is harmless. In fact, the health of the horseshoe crab is critical to the health of both the coastal ecosystem and humans.
Horseshoe crabs are important because their eggs provide food for migrating shorebirds, which stop along the Delaware Bay shores each spring to rest and feed on the protein-rich eggs before resuming their flight north to breeding and nesting grounds. Some birds double and even triple their weight on horseshoe crab eggs.
The horseshoe crab is also invaluable to human health. If you or someone you love has ever been hospitalized, it's likely that the horseshoe crab played a role in your recovery. A clotting factor in the crab's blood, which can be removed without harming the crab, is used to detect bacteria in human blood, in intravenous drugs, and even in prosthetics such as heart valves prior to implantation.
Chitin, a polymer in the crab's shell, is used to make non-allergenic sutures and wound-healing bandages. Human eye research also has been advanced by studies of the horseshoe crab's large compound eyes and optical nerve. This research has resulted in several Nobel prizes.
To learn more about horseshoe crabs, check out the Horseshoe Crab bulletin and Horseshoe Crab Model in our Sea Grant publications catalog. If your group or organization is interested in volunteering for the annual horseshoe crab census along Delaware Bay, you can learn more about it here.
Faculty Research: Dr. Nancy Targett
The horseshoe crab lived at the time of the dinosaurs. Yet sharp declines in its population make some fear it may share the same fate as its prehistoric friends. The horseshoe crab's decline is attributed to factors ranging from the loss of sandy beaches the animal needs to lay its eggs, to overharvesting, particularly of females, for use as eel and conch bait.
Currently, horseshoe crabs, used as bait, support multimillion-dollar conch and American eel fisheries. In Delaware Bay alone, watermen derive 20 - 50% of their total fishing income from conch or eel harvests.
In research funded by the University of Delaware Sea Grant College Program, Dr. Nancy Targett, a marine biologist and associate dean at the College of Marine and Earth Studies , has been working to minimize fishing pressure on the horseshoe crab through biochemistry. Through some molecular detective work, she and graduate student Kirstin Ferrari recently identified the compound in horseshoe crabs that makes them so irresistible to eels and conch. The scientists now are working to incorporate the compound into an artificial bait for testing by local fishermen.
"Our goal is to develop an artificial horseshoe crab bait that will work as well as the traditional one," she says. "The result should be a win-win situation for fishermen and the horseshoe crab, resulting in more horseshoe crabs for spawning and sustainable uses in medicine."
For More Information:
See the video clip "Taking Pressure Off the Horseshoe Crab."
See "Scientists Closing in on Artificial Bait Substitute for Horseshoe Crab," University of Delaware Sea Grant Reporter, Special Issue 2000.
Also see "Can We Sustain the Horseshoe Crab Resource in Delaware Bay without Collapsing Local Fisheries?" an editorial written by Kirstin Ferrari and Nancy Targett, which appeared in major newspapers throughout Delaware in June 2000.
