The female digs a shallow nest in the sand and lays up to 20,000 small, olive-green eggs. Next she drags the male over top to fertilize the eggs. Then they cover the eggs with sand and return to the water. Fedding on tiny worms, clams and dead fish, the miniature adult crabs continue to grow and molt until they reach sexual maturity at age nine or ten. Adult females measure up to two feet long and can weigh 10 pounds.
Males are one-third the size of females.
While it is not known how long a horseshoe crab can live, a few have survived 15 years in aquarium habitats. You can Take a close look at horsehoe crab.