A Wave of Dead Crabs! No.. Wait..

Strolling along the lagoon yesterday evening I spotted several dozen molts from American horseshoe crabs (Limulus polyphemus). Horseshoes are some of my absolute favorite animals on the planet. From their incredibly long survival timeline (pre-dinosaur, arising nearly 540 Mya) to their awesome quicksilvery-blue blood there’s just a lot of quirky facts to relate about them to students. Plus, they’re a great conservation story as a rather keystone-like species on the flyways of migrating North American birds.

My strolling partner, however, thought the molts were actual dead crabs and he practically pleaded with me not to head down to the water. “Sarah, it’ll just make you mad. Let’s go get coffee instead.” I had quite the laugh when I found the chitinous remains of their cast off outer shells instead of actual mini carcasses. From the looks of things several different instar stages of horseshoe crabs are molting in the lagoon at the moment. The fact that they are molting near the same time seems a bit bizarre to me, but perhaps there is some environmental or seasonal cue they need for inspiration to make such a drastic change. Or perhaps its just a sign that they’ve moved into shallower habitat and more of the castoffs are floating in to shore before being destroyed by the waves. Whatever the reason, there were dozens.

Molts are rather fragile but with a little cleaning and spray coats with fixative they can make pretty fantastic biofacts for environmental education. If you’re a teacher and would like a molt (most are 1 – 1.5″ with the ventral plate of legs and book gills intacts) for use in your classroom please drop me a note (email: notes @ seanursery dot com).

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