Medical Significance of the Class Arachnida Arthropoda : The class Arachnida is a group of more than 100,000 species, including spiders, scorpions, ticks, and mites. Most arachnids are adapted to kill prey with poison, stingers, or fangs. Like crustaceans, arachnids have a body that is divided into a cephalothorax and abdomen.
On the cephalothorax there are 4 pairs of legs, a pair of Chelicerae, and a pair of appendages called the pedipalps. The pedipalps help chew; in some species the pedipalps are specialized to perform other functions. Arachnids undergo incomplete metamorphosis. The class Arachnida includes 3 orders of medical importance:
1. Order the Scorpion
2. Order Araneae (spiders)
3. Order Acari (fleas and mites)
Scorpions are a group of arachnids whose pedipalps are modified into pincers. Scorpions use these pincers to handle their food and tear it apart. The scorpion’s venomous sting is used primarily to electrocute its prey and less often to defend itself. The sting is located in the terminal segment of the body, which is slender towards the tip.
The scorpion’s elongated, jointed belly is its trademark; in most chelicerates, the abdominal segments are more or less fused together and appear as a single unit. Adults of this arachnid order range in size from 1 to 18 centimeters. There are about 1,200 species of scorpion, all terrestrial, living around the world, although they are common in the tropics, subtropics, and deserts.
The mating of scorpions is complicated, with the spermatophores fixed to the substrate by the male and then taken up by the female. The young are born alive, with 1 to 95 in a given liter. Scorpions differ from spiders in two ways. Scorpions have very large pedipalps, which they hold in a forward position.
They also have a large stinger in the last segment … Read more