ticks only 2010 - 11/23/2010 ARTHROPODS The word arthropod...

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11/23/2010 1 Ticks by Dwight Bowman ARTHROPODS The word “arthropod” means jointed body. The most numerous organisms on earth, so in some respects, the exoskeleton has been more successful than the backbone. ortunately only a few are truly parasitic on humans. Fortunately, only a few are truly parasitic on humans. Primitive arthropods are suggested to have a form that consists of a body composed of a series of segments where each segment had a pair of jointed appendages, one on each side; down the center of the body extended the tube representing the digestive tract. The exoskeleton, that part which gives them that distinctive “crunch” if you ever happen to crush one, covers the outside of the body and is composed of chitin. To grow or to change their internal and external morphology (the process of metamorphosis), arthropods must change the external pp ) , p g cuticle that covers their body. This they do through a process of laying down a new cuticle in a process called molting, and then, the old cuticle is shed or ecdysed. The body is composed of hollow spaces with a gut, heart (an open circulatory system), and gills or tracheae for supplying air. ARTHROPODS Four major groups of Arthopods: The Trilobites comprise a group known only from fossils. The Crustacea compose the group that includes the well pg p known shrimp, lobster, crab, and crayfish, along with the less well known copepods. The Cheliceriformes include the horseshoe crabs and the arachnids (the spiders, scorpions, mites, and ticks). The Uniramia include the Myriapods (millipedes), Chilopods (Centipedes), and the Insects (Hexapods). . There are some obvious differences in the morphology f insects and arachnids of insects and arachnids. Adult insects have 6 legs, adult arachnids have 8 legs. Adult insects have three major body divisions (head, thorax, and abdomen); adult arachnids have two basic body divisions (cephalothorax and abdomen). Arachnids The medically important arachnids consist of spiders (including the funnel webs, widows and recluse spiders), scorpions, subclass Acari (ticks and mites). () Within the subclass Acari, there are four orders of importance in medical parasitology the Ixodida or Metastigmata (ticks) And the mites: Mesostigmata , Prostigmata , and Astigmata . Features that distinguish mites from ticks biologically Mites are smaller than ticks Have a short life span (usually living up to 3 months) Often have reduced appendages, a body with long setae , and possess a ypostome ut this structure lacks the recurved teeth found on ticks hypostome but this structure lacks the recurved teeth found on ticks Mites may penetrate and reside below the host’s epidermis or in the lungs and respiratory passages, ear canal and feather quills.
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ticks only 2010 - 11/23/2010 ARTHROPODS The word arthropod...

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