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Horseshoe Crab

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This horseshoe crab has been mounted near the trilobite display because it is more closely related to the extinct trilobites than crabs. Horseshoe crabs are “Living Fossils” meaning that they survived millions of years with little change to their physical form. Fossilized specimens have been found in Ordovician (~455 million years ago) aged rocks in North America. It is speculated that they may have existed since the Cambrian period (~600 million years ago). As with trilobites, a horseshoe crab grows larger by molting and shedding its shell. During its lifespan, and if conditions are right, one crab or trilobite can produce several potential fossils from its molted shells.

There are four species of horseshoe crabs alive today. They can be found on the eastern coasts of North and Central America, and in the Indo-Pacific (Japan’s Seto Inland Sea and along the east coast of India). The larva and adult stages of the Japanese version look very similar to the earliest forms of trilobites. During full and new moons in May and June at high tides, the adult horseshoe crabs swarm the wave protected beaches of bays and coves to spawn.

A female crab, which is much larger than the male, can develop 80,000 eggs in one spawning season. Most of these eggs are consumed by birds and fish.

The blood (copper based instead of iron) of horseshoe crabs is used to ensure that intravenous drugs, vaccines, and medical devices, are free of bacterial contamination before they are used on humans.

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