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Arthropods. http://www.iteachbio.com/Marine-Biology/Arthropods.mov. Arthropoda. Arthro-joint; pod-foot Largest group of animals Spiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, insects, etc. Found in all types of environment All feeding types –

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arthropoda
Arthropoda
  • Arthro-joint; pod-foot
    • Largest group of animals
      • Spiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, insects, etc.
    • Found in all types of environment
    • All feeding types –
      • carnivorous, omnivorous, herbivorous
  • All arthropods have
    • Exoskeleton
    • Segmented body
      • Body segments grouped into specialized regions (= tagmata, plural)
    • Jointed legs
    • Air piped directly to cells
    • Highly developed sensory organs
exoskeleton
Exoskeleton
  • Cuticle
      • Outer covering secreted by epidermis
      • Composed of 2 layers
        • Both layers contain chitin
          • Tough, resistant, nitrogenous

polysaccharide

    • Procuticle
      • Inner, thicker part of cuticle
      • Exocuticle – secreted before a molt
      • Endocuticle – secreted after a molt
    • Epicuticle
      • Outer, thin part of cuticle
      • Composed of protein & lipids
exoskeleton1
Exoskeleton
  • Some arthropods grow too big for their exoskeletons & must molt
    • Molting (ecdysis) is to leave an exoskeleton and grow a new one
segmentation
Segmentation
  • Typically each segment has a pair of jointed appendages
    • Limb segments
      • Hollow levers, rapid action
    • Jointed appendages
      • Sensory hairs for food handling, swift/efficient walking or swimming

Air Piped Directly to Cells

  • Highly efficient tracheal systems of air tubes
    • Delivers oxygen directly to tissues & cells
      • Creates a high metabolic rate
general
General
  • Usually are active, energetic animals
  • Most abundant and diverse of all animals
    • Greatest diversity (have no rivals)
    • Most number of species
    • Widest ecological distribution
  • They compete with us for food and spread serious diseases
    • They are essential in pollination of many food plants
    • They also serve as food, yield drugs and dyes
    • And create products like silk, honey, and beeswax
subphylum trilobita
Subphylum Trilobita
  • became extinct about 200 million years ago
  • they were bottom dwellers, probably scavengers
  • could roll up like pill bugs
subphylum chelicerata
Subphylum Chelicerata
  • very ancient group including: horseshoe crabs, spiders, ticks and mites, scorpions, sea spiders, and others
  • characterized by presence of 2 tagmata and six pairs of appendages
    • a pair of “chelicerae
    • a pair of “pedipalps”
    • four pairs of walking legs
  • they have no “mandibles” or “antennae”
  • most suck liquid food from their prey
class merostomata subphylum chelicerata
Class Merostomata (Subphylum Chelicerata)
  • (horseshoe crabs)
  • only five living species
  • 12” males, 18” females
  • live in shallow water along North American Atlantic coast
  • feed at night on worms and small molluscs
  • are harmless to humans
class pycnogonida subphylum chelicerata
Class Pycnogonida (Subphylum Chelicerata)
  • (sea spiders )
  • Move on four pairs of long, thin walking legs
  • Feed by sucking juices from hydroids and soft-bodied animals
  • Often have a pair of ovigerous legs (ovigers) with which males carry the egg masses
  • Common in all oceans
class arachnidan
Class Arachnidan
  • Over 50,000 species
    • Spiders, scorpions, pseudoscorpions, ticks, mites, harvestmen (daddy longlegs), etc
  • Tagmata
    • Cephalothorax & abdomen
class arachnida order araneae spiders
Class ArachnidaOrder Araneae: Spiders
  • Over 35,000 species
  • Cephalothorax & abdomen show no external segmentation
    • The tagmata are joined by a narrow, waistlike “pedicel”
  • Predators
    • feeding mostly on insects
  • Chelicerae
    • function as fangs and bear ducts from their venom glands
  • Some chase their prey, other ambush them, and many trap them in silk webs
class arachnida order araneae spiders1
Class ArachnidaOrder Araneae: Spiders
  • Seizes prey with chelicerae
    • Injects venom
    • Venom liquefies tissues, allowing spider to suck the broth into the stomach
  • Spiders with teeth crush or chew prey
class arachnida order araneae spiders2
Class ArachnidaOrder Araneae: Spiders
  • Spiders breathe by book lungs or tracheae (or both)
    • Book lungs – many parallel air pockets extending into a blood-filled chamber
class arachnida order araneae spiders3
Class ArachnidaOrder Araneae: Spiders
  • Excretory System
    • Malpighian tubules
      • Works in conjunction with specialized rectal glands
      • Potassium, other solutes, and waste materials are secreted into the tubules,
        • which drain the fluid, or “urine” into the intestines
      • Rectal glands reabsorb most of the potassium and water
        • producing a nearly dry mixture of urine and feces
class arachnida order araneae spiders4
Class ArachnidaOrder Araneae: Spiders
  • Eight Simple Eyes (poor vision)
    • Each provided with a lens, optic rods, and retina
    • Perceive moving objects
      • Some may form images
  • Sensory setae
    • Hairlike structure to aid in awareness of its environment
      • Setae communicate information about

Surroundings

        • Air currents, changing tensions in web
class arachnida order araneae spiders5
Class ArachnidaOrder Araneae: Spiders
  • Web-Spinning Habits
    • Silk glands
      • Found in 2-3 pairs of spinnerets
      • Emits a protein secretion as a liquid; hardens on contact with air to form a silk thread
        • Stronger than steel threads (same diameter)
    • Silk threads used for
      • trapping insects
      • Line their nests
      • Form sperm webs or egg sacs
      • Warning threads, molting threads, nursery webs
      • Wrap prey securely
class arachnida order araneae spiders6
Class ArachnidaOrder Araneae: Spiders
  • Are Spiders Really Dangerous
    • Timid creatures; more of an allies in the conflict with insects
      • Venom usually harmless to humans
    • Bite only when threatened or defending eggs or young
    • Two genera (in the United States) can give severe or fatal bites
      • Black widows (Latrodectusmactans)
      • Brown recluse (Loxoscelesreclusa)
class arachnida order araneae spiders7
Class ArachnidaOrder Araneae: Spiders
  • Black widow
    • Moderate to small in size
    • Shiny black, with a bright orange or red “hourglass” on the underside of their abdomen
    • Venom is neurotoxic
      • Acts on the nervous system
      • 4-5 of each 1000 bites are

reported fatal

class arachnida order araneae spiders8
Class ArachnidaOrder Araneae: Spiders
  • Brown Recluse
    • Smaller than black widows
    • Brown, and bear a violin-shaped dorsal stripe on their cephalothorax
    • Venom is hemolytic
      • destroying tissues and skin surrounding a bite
    • Bite can be mild to serious

and occasionally fatal

class arachnida order scorpionida scorpions
Class ArachnidaOrder Scorpionida: Scorpions
  • Common in tropical & subtropical regions
  • Generally secretive
  • Feed on insects & spiders
    • Seize with clawlike pedipalps & rip with jawlike chelicerae
  • Short cephalothorax
    • Bears appendages
    • 1-6 pairs of eye
  • Abdomen
    • Preabdomen
    • Postabdomen
      • Tail-like structure ending in a stinging apparatus
        • Injects venom (most are not harmful to humans)
class arachnida order opiliones harvestmen
Class ArachnidaOrder Opiliones: Harvestmen
    • “daddy longlegs”
  • Broad joining of the abdomen & cephalothorx
  • 4 pairs of long spindly legs
    • Can cast off legs if grasped by a predator
  • Chelicerae are pincherlike
  • Feed mostly as scavengers
class arachnida order acari ticks mites
Class ArachnidaOrder Acari: Ticks & Mites
  • Cephalothorax & Abdomen completely fused
  • Capitulum
    • Anterior projection that carries mouth parts
  • Found everywhere, over 25,000 species
class arachnida order acari ticks mites1
Class ArachnidaOrder Acari: Ticks & Mites
  • Mites
    • sometimes cause allergies and dermatoses
    • Agricultural pests
    • Feed on dermal tissue of terrestrial vertebrates
  • Ticks
    • Larger than mites
    • Suck blood until enormously distended
    • are among the world’s premier disease vectors,
      • second only to mosquitoes
        • (Lyme disease, Rocky Mountain spotted fever, tularemia, Texas cattle fever, etc)