The Horseshoe Crab is a fascinating organism and is one of the world?s oldest. It is a ?living fossil?. Though it is called crab, it is not really a crab; instead it is closely related to spiders and scorpions. The Horseshoe Crab has three main parts of the body: the head region, known as the ?prosoma?, the abdominal region or ?opisthosoma? and the spine-like tail or ?telson?. It has five pairs of jointed legs and a pair of pincers, and it molts its skin many times as it grows. The Horseshoe Crab is a hard-shelled invertebrate that lives in warm, shallow coastal waters on the sea floor. It has light blue, copper-based blood and breathes using gills. The Horseshoe Crab also has a long tail which acts as steering and it helps in righting itself when it is flipped upside down. Both the sexes look similar, but female horseshoe crabs are much larger than males. The Horseshoe Crab has a compound eye on each side of the prosoma, five eyes on the top of the carapace, and two eyes near to the mouth, making a total of nine eyes. It is essentially a nocturnal animal and it digs for food under the sand bed. Therefore, it is suggested to keep a thick sand bed in your aquarium. The Horseshoe Crab can feed on worms, algae and mollusks in the sediment. They are very effective scavengers at an early age, and are great for aerating and maintaining sand beds through sifting the sand and gravel in search of its food. The Horseshoe Crab is reef safe but on attaining bigger size it might harm other tank mates.
When most people think of Horseshoe Crabs they think of these huge crabs they they've seen on TV or in the Zoo. On the contrary, the Horseshoe Crabs Saltwaterfish.com offers are only an inch or two in size. In the aquarium, these creatures are as peaceful and as docile as they come. They spend most of their time buried in the sand foraging for food. They can often be recognized crawling under the sand's surface by looking for moving sand. The Horseshoe Crab has a hard, spiny shell that is porcelain white in color. Horseshoe Crabs have a number of claw-like legs underneath their hard shell that give them incredible digging ability. They also have a sharp spine that resembles a tail. In nature, this spine is used as a defense mechanism; when threatened the Horseshoe will lift up its spine to impale a predator. The Horseshoe is a very poor swimmer, which can make for great entertainment as they wobble around in the water. These crabs will molt often leaving behind a translucent replica of itself.Crabs belong to the Class Crustacea and Order Decapoda, which is characterized by two pair of antennae, three body parts, and five pairs of legs. The head of a Crab is connected to the thorax and covered by a shell called carapace. They have a smaller abdomen and tail compared to Shrimp and they keep this tucked beneath the carapace. The first pair of their legs are usually developed claws which they use to gather food, use as protection, and to move objects. In order for Crabs to grow they need to shed their exoskeleton, a process called "molting", which allows them to remove their restricting shell and begin a new one. Often times in the home aquarium Crabs will leave this translucent shell in full view so it can serve as a distraction while the Crab finds a hiding place and allows its new shell to harden.