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Horse Shoe Crab

Horse Shoe Crab

The Horse Shoe Crabs (Limulus polyphemus) are arthropods. They are found in shallow ocean waters on soft sandy or muddy bottoms. These horse crab is also called a "living fossil" as it has been living on this earth for million of years. Horse Shoe Crab is the species, which have the history of surviving for more than 250 million years. Though it is called a crab, it belongs to the Arachnid or Spider family. It is not a Crustacean. It seems to be dangerous by its appearance but it is not so. It is not dangerous.

Horse Crab Classification and Distribution

Limulidae is the family of the order Xiphosurida, which contains all the four living species of horse shoe crabs. They are the following:
Carcinoscorpius rotundicauda
These are the mangrove horse shoe crab and are found in South East Asia. Limulus polyphemus: These are Atlantic horse shoe crab and are found in the Gulf of Mexico and Northwest Atlantic coast. Tachypleus gigas: They are found in South and Southeast Asia. Tachypleus tridentatus: These are found along the coast of East Asia.

Horse Shoe Crab Anatomy
The horse shoe crab's body is around 2 feet long and is of brownish-green color. They breathe with the help of the gills. Their entire body is protected by a hard shell. They have a five pair of legs and a long and straight tail to turn upside down. This long thin tail also helps them to change their direction while swimming. They have a pair of eyes on the upper part of the shell. The diet of the horse shoe crab is clams, which includes worms and other invertebrates. But, most often they wait for night to fall for hunting worms, mollusks and crustaceans.

HorseShoe Crabs

Horse Shoe Crab Reproduction
The horse shoe crabs migrate to shallow coastal waters during their breeding season. For mating, the males select a female and cling on to her back. The spawning takes place in the last two weeks in May and the first two weeks in June. It is seen that the females dig a hole and lay eggs there. Then, the male fertilizes those eggs. A female can lay (60,000 to 120,000) eggs. The eggs take around two weeks to hatch. They lay eggs in such a large number and the reason is that these eggs are left unattended after being laid. These eggs pass through the tough natural conditions and also its predators. And, as a result only few percentages of them survive to reach adulthood.

Horse Shoe Crab Facts

  • They have four eyes in which two are small and two are compound.
  • It does not have hemoglobin in its blood.
  • Its neither a true crab nor a crustacean, but its an Arthropod.
  • Spiders and ticks are believed to be the relatives of the four known species of horse crab.
  • The female of these species is larger than a male.
  • The horseshoe crabs were used as fertilizer in the 1900s.

The number of this horse shoe crab has come down tremendously. These species is in the danger list of extinction and are needed to be protected at the time of breeding which takes place during the new moon in May and June.