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“Dead” Horseshoe Crabs on the Beach

During a recent visit to New York’s Long Island, two of my granddaughters and I walked along the shoreline of Sunken Meadow State Park to see what we could find in the wrack line (an area of debris deposited on the shore by high tides). They immediately find Atlantic horseshoe crab molts that were strewn in the wrack as far as the eye could see.

As a horseshoe crab grows, it outgrows its old shell. It develops a new, soft shell and pushes out the front of the old shell leaving the molt behind. Storms and high tides deposit many of these sheds on shore. These ancient organisms will molt many times over the course of 10 years until it reaches its full size.

Horseshoe crabs are not crabs; they are a closely related to trilobites, an ocean organism that became extinct over 252 million years ago during the Permian Extinction. Horseshoe crabs are a living fossil; they survived on this planet for 360 million years.

My granddaughters must have picked up and held out dozens of molts of all sizes as we walked along the water’s edge. Their attention turned to other organisms washed ashore which will be the subject of the next few blogs.

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