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| Horseshoe Crabs are not
actually crabs, but are in the Arachnid (spider) family. Even older
than dinosaurs, they go
back 350 million years (some sources say 600 million years!), and scientists study their blue blood
because of their longevity. Labs use a compound in their blood to
test intravenous drugs for bacteria. Horseshoe Crabs continuously grow out of their shells and
replace them with larger shells. They can live to 20 years. Females
dig shallow holes at the high-tide line and lay 20,000-80,000 tiny
eggs in the holes. Horseshoe Crab eggs are a main source of food for
migrating birds--particularly Red Knots, Dunlins, Semipalmated
Sandpipers, Sanderlings, Ruddy Turnstones and Gulls. An egg
that survives the birds' feast will grow to 1" the first year. This animal can only eat when it is walking!
Its legs grind its food and pass it to the adjacent mouth. Food
includes mollusks, crustaceans and worms. A Horseshoe Crab is not harmful to humans. The sword-like tail helps an overturned Horseshoe Crab flip itself to
an upright position. They are often flipped upside down by rough
wave action along the shore. They get stranded on the beach upside
down as the tide goes out, and could die if their gills dry out. I
have seen large numbers of Horseshoe Crabs flipped upside down by
boat wake and large waves, and have flipped them back over so they
could crawl back into the water. Read my Horseshoe
Crab article. |
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