A female Horseshoe Crab can lay as many as 90,000 eggs each season, usually in clusters of 4,000 – 5,000 at at time. However, only about 10 of those individual embryos will ever become adults. Before they get a chance to hatch, fish, sea turtles, and birds feed on the eggs.
Horseshoe Crabs are actually not crabs. They are more closely related to spiders.
Horseshoe Crabs have been around for 450 million years, predating the dinosaurs by more than 200 million years.
Horseshoe crabs have blue blood because it is copper rather than iron based.
The blood of Horseshoe Crabs contains a protein that will clot upon exposure with bacterial endotoxin. In this way, preparations such as insulin or antibiotics can be tested for contamination before being used in people.
If you find a Horseshoe Crab upside down on the beach, pick them up like a bowl and turn them over. Never pick them up by their tails.
Horseshoe crab eggs are an important food source for migratory birds such as the Red Knot.