Horseshoe crabs are arthropods with many appendages each having claws. Like other invertebrates insects and crabs they originate from kingdom animalia and division arthropoda. Horseshoe crabs are considered being untrue crabs and are closely related to scorpions and others with jointed legs like scorpions (Solomon et al, p.573)
Horseshoe crabs live in water in, oceans and seas. Horseshoe crabs have gills which they use for gaseous exchange. The crabs have six gills with about one hundred gill books on each. In ware, the water passes over the gill books. The gill filaments are able absorbs the dissolved oxygen present in the water to the respiratory system.The crabs have a larger shell and a tail which they use to propel their movements in the water.
The horseshoe crabs reproduce by means of eggs. The crabs have got reproductive organs, which they use, for mating and therefore the fusion of the male spermatozoa and the female oocyte. The female horseshoe crabs are larger than the male ones and, their eggs are fertilized internally. After the fertilization of the eggs, the female crabs move to the shore to lay their eggs (Slomon et al, p 581). The crabs incubate their eggs on the shore till they hatch into off springs.
A horseshoe crab has the mouth located below the shell which it uses to obtain food from the water into its digestive tract. The crab use cheliceras located closer to the mouth to grab food and submit to the oral tract. The crab controls its food into the mouth and to the gizzard using the gnathobases. With the aid of the sand swallowed by the crab, the gizzard grinds the food into smaller soluble pieces that can be assimilated into the circulatory system.
Solomon E, Berg L. Martin D. Biology Westport: Cengage Learning, 2005