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In most chelicerates the pedipalps are relatively small and are used as sensors by DWt7kRZs

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									Chelicerata
        Subphylum Chelicerata
• Defining characteristics
  – Absence of antennae
• Contains three classes, most of the animals
  are terrestrial and freshwater
• Marine species are horseshoe crabs, sea
  spiders, and mites
• Terrestrial include spiders, scorpions and
  mites (ticks)
      Chelicerate Segmentation
• Cephalothorax –usually has 6 pairs of
  appendages
  – First pair –chelicerae
  – Second pair –pedipalps
  – Both function as mouthparts
  – The rest are for walking
                   Chelicerae
• The chelicerae ("claw horns") that give the sub-phylum
  its name normally consist of three sections, and the
  claw is formed by the third section and a rigid
  extension of the second.
• However spiders' have only two sections, and the
  second forms a fang that folds away behind the first
  when not in use.
• The relative sizes of chelicerae vary widely: those of
  some eurypterids formed large claws that extended
  ahead of the body, while scorpions' are tiny pincers
  that are used in feeding and project only slightly in
  front of the head.
                 Pedipalps
• In most chelicerates the pedipalps are
  relatively small and are used as sensors.
• However those of male spiders have bulbous
  tips that act to syringes to inject sperm into
  the females' reproductive openings when
  mating, while scorpions' form large claws used
  for capturing prey
Spider Chelicerae
•   1 Fang (chelicera)
•    2 Venom gland
•    3 Brain
•    4 Pumping stomach
•    5 Forward aorta branch
•    6 Digestive cecum
•    7 Heart
•    8 Midgut
•    9 Malphigian tubules
•   10 Cloacal chamber
•   11 Rear aorta
•   12 Spinneret
•   13 Silk gland
•   14 Trachea
•   15 Ovary (female)
•   16 Book lung
•   17 Nerve cord
•   18 Legs
•   19 Pedipalp
            Taxonomic Summary
• Phylum Arthropoda
  –   Subphylum Chelicerata
  –   Class Merostomata
  –   Class Pycnogonida
  –   Class Arachnida
           Class Merostomata
• Defining characteristics
  – Appendages on the abdomen are flattened and
    modified for gas exchange as “book gills”
  – Terminal portion of body drawn out into an
    elongated spike
• Only 4 living species; the horseshoe crabs
             Horseshoe Crab
• The cephalothorax and
  abdomen are covered
  by a hard non-jointed
  carapace
      Merostomata Appendages
• Possess an anterior chelicerae and 5 pairs of
  walking legs
• In males the first pair of walking appendages
  are modified for grasping the female during
  reproduction
• All the legs (except the last pair) bear pinchers
  for manipulating food
• Walking legs bear gnathobases on basal part
  of legs, which aid in food manipulation
                 Respiration
• The abdomen bears the
  book gills and is
  endowed with blood
• The blood or
  components of it are
  used in pharmaceutical
  research
            Class Pycnogonida
• Defining characteristics
  – Body is not divided into distinct regions
  – Unique proboscis at the anterior end, with an
    opening at its tip
• Includes the sea spiders, several of which are
  common in our area
• Feed on soft bodied invertebrates, hydroids,
  bryozoan colonies, and sponges
                    Sea Spiders
• Have a long proboscis
  for feeding and a
  digestive tract with
  gonads extending into
  the walking legs
• Difficult to discern the
  cephalothorax, and
  abdomen
• Anterior appendages
  may bear cheliceras
  that grasp pieces food
                     Sea Spiders
• Ovigers –structures
  used by males to carry
  eggs on the body
   – When eggs are mature
     they are deposited in a
     hydroid colony
               Class Arachnida
• Arachnid, term for
  animals in the class
  including the scorpions,
  spiders, daddy longlegs,
  mites, and ticks, and
  certain other eight-
  legged land
  invertebrates.
              Characteristics
• Arachnids have four pairs of legs
• Arachnids are further distinguished by the fact
  they have no antennae and no wings.
• There are some important modifications that
  are particularly important for the terrestrial
  lifestyle of an arachnid, such as internal
  respiratory surfaces in the form of trachea, or
  modification of the book gill into a book lung,
               Arachnid Eyes
• Arachnids have two kinds of eyes, the lateral and
  median ocelli.
• The lateral ocelli evolved from compound eyes
  and may have a tapetum, which enhances the
  efficiency of photon capture.
• The median ocelli develop from a transverse fold
  of the ectoderm.
• The ancestors of modern arachnids probably had
  both types, but modern ones often lack one type
  or the other.
                 Spiders
• http://www.kidzone.ws/lw/spiders/facts.htm
• http://www.tooter4kids.com/Spiders/facts.ht
  m
• http://news.nationalgeographic.com/news/20
  04/06/0623_040623_spiderfacts.html
                Scorpions
• http://www.desertusa.com/oct96/du_scorpio
  n.html
• http://www.thaibugs.com/Articles/scorpion_f
  acts.htm
• http://www.scorpionfacts.info/
• http://animals.nationalgeographic.com/anima
  ls/bugs/scorpion.html
                   Ticks
• http://www.lyme.org/ticks/facts.html
• http://www.health.state.ri.us/disease/commu
  nicable/lyme/facts.php
• http://animals.nationalgeographic.com/anima
  ls/bugs/deer-tick.html
               Harvestmen
• http://www.critterzone.com/magazineresourc
  e/magazine-article-harvestmen-daddy-long-
  legs-Opiliones-harvestman.htm
• http://www.backyardnature.net/longlegs.htm
• http://www.biokids.umich.edu/critters/Opilio
  nes/
                   Mites
• http://www.naaf.no/en/Information-on-
  asthma-Chronic-Obstructive-Pulmonary-
  Disease-COPD-allergy-and-
  eczema/Allergi/Useful-facts-on-mites-midd/
• http://www.ehso.com/ehshome/dustmites.ph
  p
• http://education.yahoo.com/reference/encycl
  opedia/entry/mite

								
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