1

Phylum Arthropoda

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Jointed Appendages

3

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

7

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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23

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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

Order Opiliones

• One body segment• Short fangs• Myth- not most

venomous• Daddy- long legs,

harvestmen, opilioids

• http://spiders.ucr.edu/daddylonglegs.html 41

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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) 44

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 46

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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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56

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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