September 27, 2012



I was walking on the beach this weekend and came across a lot of very big, brown shells. I used a SeeMore Explorers Observation Log to describe what I saw:




























I actually knew what the animal was, but I wanted my readers to see how it is possible to figure out what you are seeing in nature.

I have always been fascinated by horseshoe crabs. Did you know that they are one of oldest living creatures? They have been around for 450 million years, which means they were here on Earth 200 million years before the dinosaurs!

The reason the shell I picked up was so light was because the crab was not in there any longer. Horseshoe crabs molt as they grow - that means that they shed their hard shells when they grow out of them. They walk out of the hard shell, and their inner shell, which they already have, begins to harden, becoming their new outer shell. Horseshoe crabs molt many times - 16 times for males, 17 times for females - before they are fully grown. If the shell had been heavy, then it would have been a dead animal.

One other interesting thing about horseshoe crabs is that they are not actually in the crustacean (crab and other shellfish) family. They are more closely related to arachnids (spiders) than they are to shellfish.

What a fascinating animal. Now can you see why I’ve always been interested in these prehistoric animals called horseshoe crabs?

Posted by: Seymour Simon

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