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Phylum Arthropoda
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Jointed Legs
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Number of speciesNumber of species
Arthropoda
Echinodermata
Ciliophora
Chordata
Mollusca
Platyhelminthes
Nematoda
Porifera
Annelida
Sarcomastigophora
Apicomplex
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Characteristics of Arthropods• Jointed appendages
– Extensive variation and adaptations(antennae, legs, wings. Mouthparts)
• Segmented (metameric)• tagmatation- fusion of segments to
form body regions(head, thorax, abdomen; cephalothorax in some)
• Open circulatory system• Ventral nerve cord• Compound eyes• Bilateral symmetry• Exoskeleton
Ecdysis- “an escape” - growth by molting
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Arthropods Most Successful Animals
• Number of species• Diversity• Distribution• Longevity
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Reasons for Success
• Versatile exoskeleton• Segmentation• Oxygen piped directly
to cells (terrestrial)• Highly developed
sensory organs• Complex behavior• Metamorphosis
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
From A Life of Invertebrates, Copyright © 1979, W. D. Russell-Hunter.
Modifications of Exoskeleton
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Compound Eye
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Metamorphosis:complete-
egglarvapupa adultincomplete- eggnymphadult
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Monarch Butterfly
Egglarva (caterpillar)pupa (in chrysalis) adult
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Arthropod Groups
• Subphylum Trilobitomorpha
Class Trilobita- extinct trilobites• Subphylum Chelicerata
Class Merostomata – horseshoe crabs
Class Arachnida- spiders, mites, etc.• Subphylum Mandibulata
Class Myriapoda- centipedes, millipedes
Class Insecta- insects
Class Crustacea- lobsters, crabs, etc.
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Subphylum Trilobitomorpha
• Class Trilobita- Trilobites
• Successful for 300 million years
• Extinct– 200 MYA
• One pair of antennae• appendages
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Subphylum Chelicerata
• Chelicerae( fangs)• No antenna• No mandibles• 4 pair of walking legs• 1 pair of pedipalps
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Class Merostomata
• Limulus (horseshoe crabs)– Dates back to Triassic– 245 MYA
• Carapace• Telson • Blood used by
pharmaceutical companies to test for endotoxins and pathogens
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pedipalps
Walking legs
Spines
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Class Arachnida
• Spiders• Scorpions• Ticks• Mites• All Have book lungs
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Class Arachnida• Chelicerae (fangs) 1st pair
of appendages around mouth- often with poison
• No antennae• 4 pair of walking legs• 2 body segments
(cephalothorax + abdomen)– Except mites & ticks
• Most are predators– Inject enzymes into prey– Suck fluid into pharynx
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Arachnid Body Regions Arachnid Body Regions
Prosoma or CephalothoraxProsoma or Cephalothorax
Ophisthosoma or AbdomenOphisthosoma or Abdomen
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Photo (a) © SS#11/PhotoDisc
Order Scorpionida
Large pedipalps
Abdominal stinger
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Order Araneae
• Spiders• Fangs with poison
glands• Silk glands
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Arachnid Book Lung
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Dugesiella
• Tarantula
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Latrodectus mactans
• Black widow spider• Neurotoxin
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Loxosceles reclusa
• Fiddle back spider– Brown recluse– Brown– Violin
• Necrotoxin
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Loxosceles reclusa
• Necrosis of tissue
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Day 3
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Day 4
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Day 5
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Day 6
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Day 9
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Day 10
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Order Acari
• Ticks• Mites• Full tagmatation-all
Body segments fused
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Rocky Mountain Spotted Fever
• Ticks are vector• High fever• Headache• Muscle pain• Rash
– BEGINS ON EXTREMETIES
• 25% fatal without antibiotics
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Dermacentor variabilis
Dermacentor andersoni Dog tick
Wood tick
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Dermatophagoides
• Dust mite• Allergies to fecal
products• 1 gram of dust holds
250,000 droppings
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Trombicula
• Chigger mite• Larva feed on skin• Dermatitis
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Subphylum MandibulataSubphylum MandibulataClass Myriapoda
centipedes and millipedes
Class Insectamost diverse animal classflies, bees, beetles, ants, etc.
Class Crustaceacrabs, lobster, barnacles,
copepod
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Subphylum Mandibulata
• Two pair of antennae (anterior to feeding appendages)
• Third segment bear mandibles (jaws for chewing or grinding)
• Compound eye
Class Myriapoda• “many
appendages”• Fewer than 10 to
hundreds of appendages
• Millipedes (mostly herbivorous + plain in color)
• Centipedes
( colorful, carnivorous) 43
Class Insecta(FKA-Hexapoda)• Most biodiverse class of
animals• Only invert.s that can fly• Distinctive head, thorax,
abdomen• Typically –three pair of
legs (6)• Have metamorphosis
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Class Crustacea• Biramous appendages-
separate into two rays• 3 pairs modified as
mouth parts• Two pair antennae• gills• Naupliar larval stage• Crabs, copepods,
crayfish, barnacles, lobster, shrimp, pill bugs 45
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Class Crustacea: Pill Bug•Only crustacean that is entirely terrestrial
• “rollie pollies”
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Copepod
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Barnacle
Cement glandCement gland
OvaryOvary
CirriCirri
MouthMouth
StomachStomach
AnusAnus
TestisTestisPenisPenis
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Fig. 19.24a
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Crayfish
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1.Gonopods
2. Opening of vas deferens(duct for sperm release)
3. Opening of oviduct
4. Seminal receptacle (opening used to accept sperm for fertilization)
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Fig. 19.5
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Fig. 19.7
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The End
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