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Horseshoe Crab Study Finds Genetically Healthy Population

Jul 24, 2016 | News

Research on the genetic makeup of horseshoe crabs along the South Carolina coast indicates the population is large, diverse, and healthy.

The study, conducted by the S.C. Department of Natural Resources (SCDNR) with a grant from S.C. Sea Grant Consortium and support from Charles River Laboratories, involved gathering genetic material from horseshoe crabs at 12 sites from Turtle Island south of Hilton Head to Marsh Island north of Charleston.

Researchers clipped tissue samples from the leg tips of more than 2,000 horseshoe crabs. In the lab, they came up with genotypes of 739 of those samples from seven of the beaches.

They found almost no inbreeding, no isolation of any one pattern of genes at any one location, and enough genetic diversity to indicate a large variety of parents producing offspring.

“We had green check marks all the way down the list,” said Tanya Darden, leader of the genetic research team at SCDNR’s Marine Resources Research Institute. “We found no conservation concerns based on genetic diversity.”

Potential overharvest of horseshoe crabs has been a concern along portions of the Atlantic coast, especially in the Northeast where they can be caught for use as bait in the fishing industry. South Carolina, however, allows the capture of horse-shoe crabs only for biomedical use.

A clotting agent in the horseshoe crab’s blood is widely used to determine whether vaccines, intravenous fluids, and artificial joints have been exposed to certain pathogens harmful to people.

Crabs caught by trawlers or by hand from spawning beaches are taken to biomedical labs, where up to 25 percent of their blood is removed before they are released back into their natural habitat. Most of the crabs, from 80-90 percent, survive the process.