Limuli

Limuli is the Latin plural form of limulus, the genus of horseshoe crabs. The best-known species is Limulus polyphemus, the Atlantic horseshoe crab, found along the eastern coast of North America from Canada to the Gulf of Mexico and the Caribbean. In taxonomic usage, limuli refers to multiple individuals of Limulus; in modern writing, scientists typically refer to Limulus polyphemus or to the genus Limulus rather than using the plural form limuli.

Limuli have a hard, horseshoe-shaped carapace, a long tail spine (telson), and book gills for underwater respiration. They lack segmented abdomens like true crabs and rely on chelicerate mouthparts to feed. Adults reach up to about 60 cm in length, with most much smaller.

They inhabit shallow coastal waters, bays, and estuaries, often in seagrass beds or sandy bottoms. They are mostly nocturnal, feeding on worms, mollusks, crustaceans, and detritus. Spawning occurs in spring, when adults migrate to beaches to release eggs and sperm into the surf; eggs hatch into free-swimming larvae that molt through several instars before reaching adulthood.

Limulus blood contains amebocytes whose clotting reaction to bacterial endotoxins forms the basis of the Limulus amebocyte lysate (LAL) test, widely used to ensure medical equipment and vaccines are endotoxin-free.

Conservation and management: overharvesting for bait and biomedical use, habitat loss, and climate change threaten some populations. Regional regulations, harvest limits, and beach protections are in place in parts of the range to support sustainability.