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| Vol. 18, No. 34 | June 10, 1999 |
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| Vol. 18, No. 34 | June 10, 1999 |
The largest population of horseshoe crabs in the world lives in Delaware Bay. This ancient animal plays a critical role in the bay's ecology and in human medicine.
There is concern, however, that the Delaware Bay's horseshoe crab population is declining, and Delaware Sea Grant scientists are working to stem the tide. To check on the status of this important creature, volunteers have registered for a horseshoe crab census to be conducted on June 11, 13, 15 and 30.
Bill Hall, Delaware Sea Grant Program, helps organize the regional census of the Delaware Bay's spawning horseshoe crab population. Now in its 10th year, the census is conducted on selected bay beaches each spring by volunteers from Delaware and New Jersey.
"Delaware Bay is the world's population center for horseshoe crabs, but during the past few years, we've noted a significant downturn in the animal's population, from 1.2 million spawning females down to about 400,000," Hall said.
"Scientists believe the decline is due to over fishing of the crab for eel and conch bait and to the loss of the sandy beaches it needs for spawning," he noted. "The census is designed to help resource managers and scientists gain a better understanding of the horseshoe crab's status and what we can do to guard our 'golden goose.' "
It's well known that dog and cat lovers continually debate about which animal is a human's best friend. But ask Hall and he will tell you that the hands-down winner is the horseshoe crab.
"Horseshoe crabs are critical to the welfare of migrating shorebirds that stop along the Delaware Bay each spring to fuel up for the flight north to Arctic nesting grounds. Some of these birds double and even triple their weight by feasting on horseshoe crab eggs," Hall said.
"Yet, the horseshoe crab is just as important to humans as it is to wildlife," he added. "This animal's blood contains a unique clotting agent that the pharmaceutical industry uses to test intravenous drugs for bacteria. No IV drug reaches your hospital pharmacy without its horseshoe crab test. So, if you or someone you love has ever been hospitalized, you owe a lot to the horseshoe crab." 
-Tracy Bryant
Horseshoe crab facts
Although called a "crab," it is actually closely related to spiders and scorpions. It is also one of the Earth's oldest creatures, having appeared here 100 million years before the dinosaurs.
Scientists have learned a lot about the human eye by studying the horseshoe crab's large compound eyes. The horseshoe crab also has numerous smaller eyes called photoreceptors on its top shell and along its tail. Sensitive to light, they help synchronize the crab's internal clock with daily cycles of light and darkness. The sword-like tail, called the telson, isn't poisonous as some people believe. When the crab has been overturned, it simply uses its tail as a lever to flip itself.
