Horseshoe Crabs Abound In Jamaica Bay
Horseshoe Crabs Abound In Jamaica Bay
by Don Riepe, Jamaica Bay Guardian
This past week in cooperation with Gateway National Recreation Area, the American Littoral Society led its 3rd horseshoe crab walk of the season at the Jamaica Bay Wildlife Refuge. The horseshoe crab is not a crab at all but a modern prehistoric arachnid (i.e. related to spiders and scorpions) whose fossil records date back over 300 million years. Currently, four species exist worldwide. One species (Limulus polyphemus) populates the Atlantic coast from Maine to the Yucatan peninsula in Mexico with the largest concentrations found in Delaware Bay. The other three species are found in the Indian and Pacific Oceans. My first encounter with this marine animal was as as a child swimming in the polluted waters of Jamaica Bay. I remember being both fascinated and afraid of this harmless but fearsome-looking creature and thinking that its telson, or tail, was a "poison stinger". Since then I’ve learned that, aside from being an interesting curiosity, this "crab" has great medical and ecological value.
In the 1960’s, it was discovered that the material inside the white blood cells of the horseshoe crab could detect endotoxins and would clot when exposed to minute traces of gram-negative bacteria. This material, Limulus Amebocyte Lysate (LAL), is used in the pharmaceutical industry as the most sensitive and cost-effective test for finding endotoxins in intravenous solutions. Although found everywhere in nature and harmless to humans, endotoxins become toxic when entering the blood stream. Additionally, the crab’s large compound eyes and accessible optic nerve have been used in scientific research for over 50 years.
Each spring, the horseshoe crabs come ashore to lay their eggs at the high tide line. The eggs provide a much-needed food resource for migrating shorebirds arriving in New York City from their winter homes in Central and South America. Some birds such as black-bellied plovers and red knots may have traveled several thousand miles across the ocean, making their first landfall in the estuaries of New York and New Jersey. Besides shorebirds, the egg feast attracts many laughing gulls, glossy ibis and even Canada geese , whose goslings feed on animal matter as well as vegetation. Snowy egrets join in too, not to feed on the eggs, but on the mummichogs and other killifish that are taking part in this bountiful melee. Larger predators such as herring and great black-backed gulls will frequently take advantage of overturned horseshoe crabs and peck out their gills, leaving the beachfront strewn with dead and dying crabs. Despite this onslaught, the crabs keep coming ashore, determined to carry out the reproductive urge as they have done for millions of years before the advent of Homo sapiens.
It is humans, however, that pose the greatest threat. In earlier times, native Americans used the horseshoe crab for food and the shell for bailing water out of their canoes. They also used the long, pointed tail for spearing fish. None of these uses threatened the horseshoe crab’s existence. Today, however, using very efficient trawling techniques, the harvest of great numbers of horseshoe crabs for use as eel and conch bait has decimated their crab population in some areas. The continued nibbling of shorelines by development has eliminated some of the crab’s breeding areas.
Hopefully, legislation and harvest quotas will provide the necessary protection to ensure that this amazing ritual will continue for future generations to enjoy. For more information about where and when to go see the horseshoe crabs, call the Littoral Society (718) 318-9344. Check their website for more info: www.alsnyc.org.