Horseshoe crabs

An Atlantic horseshoe crab moves across the sand on Pickering beach, a national horseshoe crab sanctuary in Little Creek, Delaware, May 20, 2008. The Atlantic horseshoe crab, part of the Atlantic coast ecosystem and an ancient species more than 350million years old, return from deeper water each May and June to lay their eggs on these beaches at the new and full moon tides. During spawning the crabs form clusters along the water’s edge with as many as 12 sattelite males grouped around one female. The females burrow into the sand to lay masses of green eggs which are fetilized by the males. The eggs provide essential food for as many as one million migrating shore birds that use horseshoe crab eggs as their primay food source on their northward migration. REUTERS/Mike Segar (UNITED STATES) – PM1E45S0SJ101