horseshoe crab

noun

: 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

Combined, the two fisheries kill over half a million horseshoe crabs every year. —Kristoffer Whitney, Fortune Well, 13 Oct. 2023

This suggested that the trilobite likely had alkaline or neutral conditions in its gut, similar to the conditions found in the stomachs of living mud crabs and horseshoe crabs. —Jack Tamisiea, Scientific American, 28 Sep. 2023

There are also some familiar creatures, including arthropods such as crustaceans and horseshoe crabs, as well as sponges, starfish, and worms. —Byelizabeth Pennisi, science.org, 1 May 2023

In this account, rural people are, like horseshoe crabs, holdovers—living representatives of a distant past. —Daniel Immerwahr, The New Yorker, 16 Oct. 2023

However, for now the wild harvest of horseshoe crabs remains critically important to drug safety, Blair said. —Patrick Whittle, Fortune, 31 July 2023

Red knots were listed as threatened under the Endangered Species Act in 2015, largely because horseshoe crab fishing threatened this key food source. —Kristoffer Whitney, Fortune Well, 13 Oct. 2023

Together for 22 years, the couple share a home in Corona del Mar. But rather than developing a flying car, Gregg is looking at the slime produced by hagfish, the antiseptic qualities of horseshoe crab blood, undersea robots and the potential of a sardine boat almost 90 years old. —Thomas Curwen, Los Angeles Times, 3 Nov. 2023

Now, however, critics are raising questions about environmental impacts and the process for reviewing and approving synthetic alternatives to horseshoe crab blood. —Kristoffer Whitney, Fortune Well, 13 Oct. 2023

Word History

First Known Use

1797, in the meaning defined above

Kids Definition

horseshoe crab

noun

: any of several closely related arthropods that have a broad crescent-shaped united head and thorax and a tail resembling a spike