# Horseshoe Crab (*Limulus polyphemus*) Horseshoe crabs are ancient creatures that look like armored helmets with long tails. They live in the ocean and are important for medical research. - **Category:** [Invertebrate](https://www.snappit.app/explore/categories/invertebrate) - **Rarity:** Common - **Danger:** 2/5 · Low - **Snaps:** 124 - **Habitat:** Coastal areas - **Also known as:** King Crab, Limulus ![Horseshoe Crab](https://res.cloudinary.com/drieglelr/image/upload/v1771426736/objects/6163.jpg) ## Appearance The Horseshoe Crab has a hard, helmet-shaped carapace that is typically brownish-green. Its unique dome-like shell and long, spiky tail, called a telson, make it visually distinct from true crabs. Its smooth, rounded front shell protects most of its body. ## Taxonomy - **Kingdom:** Animalia - **Phylum:** Arthropoda - **Class:** Merostomata - **Order:** Xiphosurida - **Family:** Limulidae - **Genus:** Limulus ## Interesting facts - A female horseshoe crab can lay up to 80,000 tiny eggs in a single nesting season! - Horseshoe crabs breathe using 'gill books,' special leaf-like structures hidden under their shell. - They are more closely related to spiders and scorpions than to true crabs or insects! - They have 10 eyes, some on top and some underneath their shell, for sensing light! ## Special abilities - **Blood Shield:** Horseshoe Crab has unique copper-based blue blood that helps them fight off bacteria and detect harmful substances. - **Living Fossil Armor:** Horseshoe Crab has a tough, multi-jointed exoskeleton that helps protect them from many ocean predators. - **Tail Skipper:** Horseshoe Crab can use its long, spiky telson (tail) that helps them flip themselves back over if overturned. ## Measurements & details - **Size:** 300-600 mm - **Lifespan:** 3650-7300 days - **Leg Count:** 10 ## Diet & Feeding They are bottom-feeders, eating small invertebrates and worms found in the seafloor. - **Primary Foods:** marine worms, small clams, crabs, dead fish - **Foraging Method:** Foraging ## Ecological connections - **Eaten by:** [Red Knot](https://www.snappit.app/explore/red-knot) (*Calidris canutus*) — Their eggs are a critical food source for migrating birds. - **Eaten by:** [Loggerhead Sea Turtle](https://www.snappit.app/explore/loggerhead-sea-turtle) (*Caretta caretta*) — Adult horseshoe crabs are part of their diet. - **Eaten by:** Dusky Shark (*Carcharhinus obscurus*) — Sharks occasionally prey on adult horseshoe crabs. ## Traits - [Omnivorous](https://www.snappit.app/explore/traits/omnivorous): This trait identifies organisms whose diet includes both plant and animal matter. - [Ancient Lineage](https://www.snappit.app/explore/traits/ancient-lineage): This trait signifies organisms belonging to a very old evolutionary group with ancestors dating back millions of years. - [Armored](https://www.snappit.app/explore/traits/armored): Armored describes animals protected by a hard, external covering or shell for defense. - [Keystone Species](https://www.snappit.app/explore/traits/keystone-species): Describes a species whose presence and role have a disproportionately large effect on its environment. - [Regenerative](https://www.snappit.app/explore/traits/regenerative): Regenerative organisms possess the ability to regrow lost or damaged body parts, tissues, or organs. - [Marine](https://www.snappit.app/explore/traits/marine): Marine habitats encompass all saltwater environments of the Earth's oceans, supporting an immense diversity of aquatic life. - [Nocturnal](https://www.snappit.app/explore/traits/nocturnal): Nocturnal animals are primarily active during the nighttime hours, typically resting or sleeping during the day. - [Venomous](https://www.snappit.app/explore/traits/venomous): Venomous organisms produce toxins that are injected into another animal, typically through a bite or sting. ## Collections - [Insects](https://www.snappit.app/explore/collections/insects) ## Safety **Danger:** 2/5 · Low If you see a horseshoe crab on the beach, observe from a safe distance and don't touch them. ## Frequently Asked Questions ### How to identify Horseshoe Crab? Look for fins, arms, tentacles, shells and body symmetry. Underwater light shifts colors, so structure and markings usually matter more than shade. Sea Creature Identifier: upload a photo and compare the visible details. ### How big is Horseshoe Crab? 300-600 mm ### How long does Horseshoe Crab live? 3650-7300 days ### What does Horseshoe Crab eat? They are bottom-feeders, eating small invertebrates and worms found in the seafloor. ### Where is Horseshoe Crab usually found? Coastal areas ### How does Horseshoe Crab hunt? Foraging ### How many legs does Horseshoe Crab have? 10 ## Where to spot - [Barrington Civic Center Historic District](https://www.snappit.app/guides/places/barrington-civic-center-historic-district) — Rhode Island, US · Historic District - [Bellevue Avenue Historic District](https://www.snappit.app/guides/places/bellevue-avenue-historic-district) — Rhode Island, US · Historic District - [Camp Evans](https://www.snappit.app/guides/places/camp-evans) — New Jersey, US · Historic Site - [Cape Lookout Coast Guard Station](https://www.snappit.app/guides/places/cape-lookout-coast-guard-station) — US · Historic Site - [Cedarmere-Clayton Estates](https://www.snappit.app/guides/places/cedarmere-clayton-estates) — New York, US · Historic District - [Coindre Hall Park](https://www.snappit.app/guides/places/coindre-hall-park) — New York, US · Park [View all places to see Horseshoe Crab](https://www.snappit.app/guides/where-to-see/horseshoe-crab) ## More Invertebrate - [Coral](https://www.snappit.app/explore/coral) - [Crab Spider](https://www.snappit.app/explore/crab-spider) (*Mecaphesa asperata*) - [Garden Spider](https://www.snappit.app/explore/garden-spider) (*Araneus diadematus*) - [Brown Recluse Spider](https://www.snappit.app/explore/brown-recluse-spider) (*Loxosceles reclusa*) --- Source: [Horseshoe Crab: Facts & Places to See — Snappit](https://www.snappit.app/explore/horseshoe-crab)