Horseshoe crabs. (Photo by Chris Engel from Pixabay via Courthouse News) CHARLESTON, S.C. (CN) — Environmental advocates asked a federal judge Friday to block the planned blood harvest of thousands of horseshoe crabs in a South Carolina wildlife refuge. The conservation groups, Defenders of Wildlife and Southern Environmental Law Center, say in a motion for a preliminary injunction that a pharmaceutical company’s practice of harvesting horseshoe crabs as they come ashore to lay their eggs each spring in the Cape Romain National Wildlife Refuge is detrimental to the ecosystem. “This harvest of horseshoe crabs is illegal and should not be allowed to continue one more year,” Catherine Wannamaker, a senior attorney at the Southern Environmental Law Center, said in a statement.