Sexy Saturday - Horseshoe Crabs

It's almost time for the horseshoe crabs again.  In the cold winter months, they go to deeper water and bury in the mud, waiting for spring. (Like the rest of us!)  As we start diving regularly again, we always see mating pairs of horseshoe crabs scooting around on the bottom. Here is their story;
The American Horseshoe Crab (Limulus polyphemus) is not actually related to a crab at all.  They are more closely related to scorpions, ticks and land spiders.  They are however, one of the longest surving species, with a design basically unchanged in 250 million years.  Their hard curved shell makes it difficult for predators to turn them over and they can adapt to big changes in temperature and salinity. A horseshoe crab can go without eating for almost a year if necessary.
Each spring during a new moon or full moon high tide, male horseshoe crabs start migrating in toward the shoreline.  Once the females start to arrive, the males release a pheromone into the water to attract them and use their compound eyes to spot a potential mate.  Once a female has been selected, the smaller male uses a glove-like claw to attach to her shell.  The female then drags the male in toward the beach.  Every few feet on shore, the female digs and deposits as many as 20,000 eggs.  The male fertilizes the eggs as he is pulled over the nest.
A female may lay as many as 90,000 eggs each season, but with very high predatory rates only about 10 percent survive to adulthood.  The eggs of the horseshoe crab are an important source of food for migratory shorebirds, and many species of fish feed on larvae or recently molted juvenilles.
For more information, NOAA has a whole website devoted to the the horseshoe crab. http://www.http//www.ceoe.udel.edu/horseshoecrab/