He even has a picture showing their underbellies, which are soft and not protected.
They look really menacing, but are harmless. Even if they look like they can swiftly attack us humans, they only feed on mollusks and worms. Their long tails act like rudders so they can plow through sand and muck. It also helps them go back belly side down when they get tipped over.
Last Friday at noon, Elise answered the ringing phone and turned to me,"Daddy said to go down RIGHT NOW, as fast as you can! I think he saw a creature!" So, we dropped everything and went down to the beach. There was a pair of them again!
One was smaller than the other and was attached to the bigger one. The female is the bigger one, and the male is the smaller one. During high tides and full moons, they mate and bury their 20,000 eggs in the sand. In some places, there is as much as six males latched on to the female.
We found out later that they are not "helmet" crabs. We thought they were, as they looked like huge helmets. But helmet crabs look like this.
photo from http://www.afsc.noaa.gov/kodiak/images/photo/crabtelekin.jpg
They are called "horseshoe" crabs. They used to be called "horsefoot crabs", as the shell looks like a horse's hoof.
photo from www.wildheartshoofcare.com
When they walk around on their dozen clawed legs, they look like this:
photo from DCWild Gallery
They have evolved very little in the last 250 million years. Maybe because they can go a year without eating and can survive extreme temperatures and salinity.
The horseshoe crab's blue blood is copper-based, and is used to test the purity of medicines. Chemists use it to detect dangerous and fatal bacteria in newly manufactured medicines. Certain shell properties are also used to speed blood clotting and to make absorbable sutures. Having had two Cesarean deliveries, I can appreciate that, as I had absorbable sutures. Very cool.