Horseshoe Crab
The horseshoe crab is in the kingdom Animalia. It is under the phylum Arthropoda - joint legged animals. the subphylum is Cheilcerata - animals with no jaws. Horseshoe crabs are found in the class Merostomata - mouth surrounded by legs. The subclass is Xiphosura — from the Greek Xiphos meaning sword and ura meaning tail. Its species is polyphemus — from the Greek, meaning one-eyed giant and referring to the simple eyes on the front of the shell.
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Horseshoe crabs have bilateral symmetry. The appearance of a horseshoe crab is that the entire body of the horseshoe crab is protected by a hard shell. it has two primary compound eyes and seven secondary simple eyes, two of which are on the underside.Beneath the carapace, it looks like a large spider. It has five pairs of legs for walking, swimming, and moving food into the mouth. The long, straight, rigid tail can be used to flip itself over if turned upside down, so a horseshore crab with a broken tail is more susceptible to desiccation or predation. Behind their legs, they have book gills, which exchange respiratory gasses and are occasionall
Two of many adaptations the horseshoe crab has had to make to survive for so long are that the gills of the horseshoe crab are very versatile and they can help propel the
horseshoe crab when it is swimming upside down. Also the chelicerae, this is an appendage on the front legs that gathers food and then
brings it to where the legs can crush it and then funnels the crushed food to
the mouth.
Horseshoe crabs play an important ecological role in the food web. A decline in the number of horseshoe crabs will impact other species, particularly shorebirds and sea turtles, a federally-listed threatened species that uses the Chesapeake Bay as a summer nursery area. Shorebirds primarily feed on horseshoe crab eggs exposed on the surface, but sufficient surface eggs are available only if horseshoe crabs are spawning at high densities. Therefore, adequate spawning densities must be maintained to ensure availability of horseshoe crab eggs for shorebirds. Sea turtles feed on adult horseshoe crabs, but their diet depends on relative abundance of the prey species.
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Horseshoe crabs are important in medical
research. The large lateral compound eyes are used to study cellular mechanisms of retinal function in humans. Horseshoe crab blood and blood products are used in cancer research, to test sterility of drugs and antibiotics and to signal the presence of chemical poisons, endotoxins, produced by certain bacteria. Chitin, a substance found in the horseshoe crab’s shell, is non-toxic, biodegradable and used in contact lenses, skin creams and hair sprays. Horseshoe crabs have been intensively harvested for medical research, for industry and for bait in certain fisheries. Many states are now regulating their capture and are formulating management plans to ensure the survival of this species that has outlived the dinosaurs. |
Vocab
Telson:
-------------------------------------------------------------------------------------------------------------- Prosoma: ----------------------------------------------------------------------------------------------------------------- Opisthosoma: ---------------------------------------------------------------------------------------------------------------- Heart: ----------------------------------------------------------------------------------------------------------------- Pusher legs: ---------------------------------------------------------------------------------------------------------------- |
The horseshoe crabs tail.
--------------------------------------------------------------------------------------------------------- The front section ---------------------------------------------------------------------------------------------------------------- The middle section. ----------------------------------------------------------------------------------------------------------- long, tube like and runs the length of their body. ------------------------------------------------------------------------------------------------------------- The fifth pair of legs found nearer the tail, and is used to push the animal forward. ------------------------------------------------------------------------------------------------------------ |
http://en.wikipedia.org/wiki/Horseshoe_crab
http://www.beach-net.com/whats-here/horseshoe-crabs.php
http://www.arkive.org/horseshoe-crab/limulus-polyphemus/