Common name: Horseshoe crab

Scientific name: Limulus polyphemus (Linnaeus, 1758)
Horseshoe CrabHorseshoe crab (Limulus polyphemus) crawling in sand
Horseshoe Crab(Limulus polyphemus)  Feeding in Tide Pool on Marco Island Beach, Marco Island, Florida, USA

General information

The Horseshoe Crab, Limulus polyphemus, is an ancient marine arthropod that is more closely related to spiders and scorpions than to true crabs. Despite its name, it is not a crab at all. These creatures have been around for over 450 million years, making them living fossils. They have a hard exoskeleton, a long, pointed tail spine (telson), and a unique, horseshoe-shaped carapace.

Details

Recommended minimum tank volume
2,000 liter (530 gallons)
Salinity
S.G. 1.020 to 1.025
Temperature
16 to 24 °C (61 to 75 °F)
Acidity
pH 7.8 to 8.3
Average size
60 cm (2′)
Care level
Very difficult Needs very large space, not for home aquariums
Diet
Omnivore Scavenges, eats worms, algae, detritus
Reefsafe
No May disrupt tank environment
Aggression
Peaceful Non-aggressive but can harm with size
Captive bred
No

Taxonomy

  1. Kingdom
    Animals
    Animalia
  2. Phylum
    Arthropods
    Arthropoda
  3. Class
    Horseshoe Crabs
    Merostomata
  4. Order
    Horseshoe Crabs
    Xiphosurida
  5. Family
    Horseshoe crabs
    Limulidae
  6. Genus
    Horseshoe Crab
    Limulus
  7. Species
    Horseshoe crab
    Limulus polyphemus (Linnaeus, 1758)
  8. Synonyms
    Limulus albus Bosc, 1802
    Limulus americanus Leach, 1819
    Limulus cyclops Fabricius, 1793
    Limulus occidentalis Lamarck, 1801
    Limulus sowerbii Leach, 1815

Care

Horseshoe Crabs are not commonly kept in home aquariums due to their large size and specialized needs. They require spacious tanks with a deep sand bed for burrowing and a variety of live foods to scavenge. Their diet in captivity can include mollusks, worms, and other small invertebrates.

Reproduction

Horseshoe Crabs are known for their spectacular spawning events on beaches during the spring and summer full moons. Females lay thousands of eggs in the sand, which are then fertilized by the males. In captivity, breeding is rare and requires a large, species-specific setup.

Symbiosis

While not typically involved in symbiotic relationships within an aquarium setting, Horseshoe Crabs play a crucial ecological role in their natural habitat. Their eggs provide a vital food source for migrating shorebirds, and their scavenging helps to clean the environment.

Habitat

Limulus polyphemus is found along the Atlantic coast of North America, from Maine to the Yucatan Peninsula. They inhabit shallow ocean waters and estuaries, often burying themselves in sandy or muddy substrates.