| Limulidae Temporal range:
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|---|---|
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| Tachypleus gigas, one of the four extant species | |
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| Jurassic-aged limulids. Crenatolimulus (A,B), Limulus (C), Mesolimulus (D,E) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Order: | Xiphosura |
| Superfamily: | Limuloidea |
| Family: | Limulidae Leach, 1819[1][2] |
| Genera | |
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See text | |
Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and are the only surviving xiphosurans. Despite their name, they are not true crabs or crustaceans. Rather, they are chelicerates. This makes them more closely related to arachnids like spiders, ticks, and scorpions.
The body of a horseshoe crab is divided into three main parts: the cephalothorax, abdomen, and telson. The largest of these, the cephalothorax, houses the majority of the animal's eyes, limbs, and internal organs. It's also where the animal gets its name, as its shape somewhat resembles that of a horseshoe.
Horseshoe crabs primarily live on the bottom of shallow coastal waters, but can swim if needed. These animals are occasionally used as fishing bait, but they are also eaten in some parts of Asia. More commonly, horseshoe crabs are caught for their blood, something valuable to the medical industry. This use comes from the Limulus amebocyte lysate, a chemical in their blood used to detect bacterial endotoxins.
In recent years, these animals have experienced a population decline. This is mainly due to coastal habitat destruction and overharvesting.
- ^ Sekiguchi K (1988). Biology of Horseshoe Crabs. Science House. ISBN 978-4-915572-25-8.
- ^ "Limulidae Leach, 1819". World Register of Marine Species. Flanders Marine Institute. 2023. Archived from the original on 26 April 2023. Retrieved 17 January 2023.