horseshoe crab


Definition of horseshoe crab

: any of several closely related marine arthropods (order Xiphosura and class Merostomata) with a broad crescentic cephalothorax, six pairs of legs, and a spikelike tail especially : one (Limulus polyphemus) of coastal waters from Maine to the Yucatán Peninsula

Note: The horseshoe crab is often said to have five pairs of legs since the first pair is greatly reduced in size and used mainly for feeding. All the legs of the horseshoe crab end in claws except for the last pair of legs which have leaflike expansions used mainly for pushing.

… a horseshoe crab … is a Swiss army knife of jointed limbs—for walking, swimming, grasping, shredding, and defending.
— Carl Zimmer … the horseshoe crab has changed little since an ancestor was fossilized 150 million years ago … National Geographic

called also king crab

Examples of horseshoe crab in a Sentence

Recent Examples on the Web The story of the horseshoe crab is a lesson in humility. Tim Prudente,, "How the coronavirus vaccine relies on Maryland’s strangest fishery: horseshoe crabs," 31 Dec. 2020 Humans owe a debt to the strange-looking, ancient horseshoe crab. Alex Fox, Smithsonian Magazine, "The Race for a Coronavirus Vaccine Runs on Horseshoe Crab Blood," 8 June 2020 Back in the late 1990s and early 2000s, there was concern over the fate of the horseshoe crab. Doug Fraser, USA TODAY, "Horseshoe crabs may be the answer to a safe coronavirus vaccine next year. Here's why.," 16 June 2020 Starting at $25, adopters receive a digital photo of a horseshoe crab and adoption certificate, plus a copy of its annual newsletter. Jennifer Nalewicki, Smithsonian Magazine, "Ten Animals and Plants Around the World That You Can (Virtually) Adopt," 5 May 2020 The horseshoe crab has long been overlooked and overfished. Carol Motsinger, USA TODAY, "Horseshoe crabs have a vital role in the development of a coronavirus vaccine. Here's why.," 22 Sep. 2020 Environmentalists are concerned that the American horseshoe crab is near threatened, but Jones doubts that concern. David Hogberg, Washington Examiner, "'This supply chain has never been tested': Production bottlenecks threaten mass vaccine rollout," 3 Sep. 2020 In December 2017, researchers found a 245-million-year-old fossil of a horseshoe crab that resembled Vader. Chris Ciaccia, Fox News, "13-inch long 'Darth Vader' crustacean found in Indonesia," 20 Aug. 2020 In the race to find a COVID-19 vaccine, horseshoe crab blood is very important. Alex Fox, Smithsonian Magazine, "The Race for a Coronavirus Vaccine Runs on Horseshoe Crab Blood," 8 June 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'horseshoe crab.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of horseshoe crab

1797, in the meaning defined above

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The first known use of horseshoe crab was in 1797

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Last Updated

11 Jan 2021

Cite this Entry

“Horseshoe crab.” Dictionary, Merriam-Webster, Accessed 19 Jan. 2021.

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