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Source: The Journal News

Horseshoe crab quest: Rye students help track survivors of the Ice Age


Posted: June 17, 2013
Originally Published: June 16, 2013

In horseshoe-crab parlance, she was middle-aged, she was alone and she had issues.

“This is a two, female and single,” said biology professor Jennifer H. Mattei, standing in the shallows of Milton Harbor in Rye. “Put down some spine damage.”

In her hands was a dinner-plate-sized horseshoe crab, the latest in some 70,000 crabs she and colleagues have pulled from Long Island Sound during 12 years of research.

Two referred to its age: about 15 or 16 years old, well past a final shell-shedding when she was about 10 and not into old age yet — which for such creatures can be 20 or more years. Single meant no male clung to her back, ready to fertilize the thousands of eggs she may want to lay. Plus, some of the spines along her abdomen were broken.

As the horseshoe crab population fluctuates, Mattei of Sacred Heart University in Fairfield, Conn., and other researchers are trying to better understand their numbers and their role in a web that includes fish, long-distance-migrating shorebirds and life-saving biomedical research.

Horseshoe crabs, primitive creatures more closely related to spiders than true crabs, are nothing if not romantic. Peak mating takes place on spring nights, during high tides associated with new and full moons, and to the sound of gently lapping waves, as females deposit their eggs in a nest scraped out at the water line. Such behavior also makes them accessible to scientists.

Horseshoe crabs have roamed the sea bottom since before the dinosaurs appeared. They have survived the Ice Age and several mass extinctions, crawling eon after eon to the edge of a bay or a sheltered beach to reproduce. The crabs eat almost anything – worms, small fish, crustaceans — and can endure a wide range of water temperatures and salinity.

“They’re such generalists,” said Fordham University professor Mark Botton, who co-chairs an international working group on their conservation. “They’re not locked into any one thing.”

Females are bigger than males. Other than that, one horseshoe crab pretty much looks like another — except for those adorned by Mattei and her helpers with white, plastic discs. About 20 Rye Country Day students were helping attach the silver-dollar-sized “crab tags” on each animal’s shell on a recent day at the Marshlands Conservancy. Each tag carries a six-digit identification number and a phone number to call if you find the creature.

“You just twist until the stop goes in,” said Mattei, who lives in Armonk. “It’s like ear piercings. He doesn’t have nerves there toward the end. He didn’t even bleed.”

Over the years, information has come in on about 12 percent of the tags. Most of Mattei’s charges have stayed in the Sound, scuttling along the New York-Connecticut shore or over to Long Island. A few ended up in Rhode Island.

“We have been able to establish the population in Long Island Sound is one big population. They interbreed, they move around, but they stay in the Sound,” Mattei said.

There are four species of horseshoe crabs in the world. Limulus polyphemus is found from southern Maine to Florida and then jumps across to the Yucatan peninsula. The others are in India, southeast Asia and Japan.

Accurate population data is hard to come by as research groups have assessed their numbers differently. Mattei considers the Sound to harbor several million. The population is “not declining, but it’s not increasing,” she said.

A 2009 federal review noted “declining abundance in New York and New England.”

“The horseshoe crab used to be prevalent up and down the eastern seaboard, however development, pollution and overharvesting have severely impaired their populations and habitat,” according to a 2010 report by Citizens Campaign for the Environment.

The crabs are both economically and environmentally important, Mattei said. Millions of shorebirds feast on their billions of eggs during migrations from South America to the Arctic. The crabs also are caught commercially as bait for eel and whelk fisheries — both of which are predominantly sold overseas — and for the pharmaceutical industry, which uses their blood to test vaccines and other drugs for contamination.

The commercial catch is regulated by the states and the federal government. New York’s quota for its spring catch this year is 136,500 crabs.

Of the eight crabs Mattei grabbed at the Marshlands, at least half were couples intent on procreating. By the end of June, most horseshoe crabs will retreat back into the Sound’s waters to wait for another spring.

“So long, little buddy,” junior Andrew Starker of Purchase said as he placed a newly tagged crab back in the water.