NX09

Female

The Moon

Horseshoe crab are marine arthropods of the family Limulidae and order Xiphosura or Xiphosurida that live primarily in and around shallow ocean waters on soft sandy or muddy bottoms. They occasionally come onto shore to mate. They are commonly used as bait and in fertilizer. In recent years, a decline in the number of individuals has occurred as a consequence of coastal habitat destruction in Japan and overharvesting along the east coast of North America. Tetrodotoxin may be present in the roe of species inhabiting the waters of Thailand.[2] Horseshoe crabs are considered living fossils.[3]
Horseshoe crabs resemble crustaceans, but belong to a separate subphylum, Chelicerata, and are closely related to arachnids, e.g., spiders and scorpions. The earliest horseshoe crab fossils are found in strata from the late Ordovician period, roughly 450 million years ago.

The Limulidae are the only recent family of the order Xiphosura, and contain all four living species of horseshoe crab:[1]

Carcinoscorpius rotundicauda, the mangrove horseshoe crab, found in Southeast Asia
Limulus polyphemus, the Atlantic horseshoe crab, found along the American Atlantic coast and in the Gulf of Mexico
Tachypleus gigas, found in Southeast and East Asia
Tachypleus tridentatus, found in Southeast and East Asia
Unlike vertebrates, horseshoe crabs do not have hemoglobin in their blood, but instead use hemocyanin to carry oxygen. Because of the copper present in hemocyanin, their blood is blue. Their blood contains amebocytes, which play a role similar to white blood cells of vertebrates in defending the organism against pathogens. Amebocytes from the blood of L. polyphemus are used to make Limulus amebocyte lysate, which is used for the detection of bacterial endotoxins in medical applications. The blood of horseshoe crabs is harvested from living horseshoe crabs for this purpose.[1]

Harvesting horseshoe crab blood involves collecting and bleeding the animals, and then releasing them back into the sea. Most of the animals survive the process; mortality is correlated with both the amount of blood extracted from an individual animal, and the stress experienced during handling and transportation.[12] Estimates of mortality rates following blood harvesting vary from 3 to 15%.[13]
Horseshoe crab are used as bait to fish for eels (mostly in the United States) and whelk. However, fishing horseshoe crab is temporarily forbidden in New Jersey (moratorium on harvesting) and restricted to only males in Delaware. A permanent moratorium is in effect in South Carolina.[14]

A low horseshoe crab population in Delaware Bay is hypothesized to endanger the future of the red knot. Red knots, long-distance migratory shorebirds, feed on the protein-rich eggs during their stopovers on the beaches of New Jersey and Delaware.[15] An effort is ongoing to develop adaptive-management plans to regulate horseshoe crab harvests in the bay in a way that protects migrating shorebirds.

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