Phylum Arthropoda: Protostome-Eucoelomate Group
• Jointed appendages
• Metamerism- serial segmentation
• Tagmata- discrete functional units (head-thorax-abdomen)
• Exoskeleton
• Gills and tracheal system
• Highly specialized body segments
• Hemocoel-body space filled with hemolymph
• Open circulatory system
Subphylum Chelicerata
1. 1st pair of appendages modified into chelicerae
2. Pedipalps, 4 pairs of legs
3. No antennae or mandibles
4. Two tagmata: cephalothorax and abdomen
Class Merostomata
A. Aquatic chelicerates
B. Respiration- gills
C. Lifestyle- marine
D. Ex:Horseshoe crabs
Class Arachnida
A. Structure- Somites fused into cephalothorax
B. Segmentation-abdomen segmented or unsegmented
C. Respiration- book lungs
D. Lifestyle- terrestrial and freshwater
Subphylum Crustacea
1. Structure- Covered with carapace
2. Mandibles and 2 pairs of maxillae
3. Appendages- biramous
4. Cephalization- developed with two pair of antennae
5. Respiration- gills
6. Ex: Crayfish
Subphylum Uniramia
1. Appendages- uniramous
2. Cephalization- head appendage consisting of one pair of antennae
3. One pair of mandibles
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Class Chilopoda
1. Structure- elongated with dorsoventrally flattened body
2. Appendages- one pair of legs per segment
3. Trachea present
4. Ex: Lithobius; Centipedes
Class Diplopoda
1. Structure- wormlike
2. Appendages- two pairs of legs per segment
3. Ex: Spirobolus; Millipedes
Class Insecta
1. Structure- three tagmata: head, thorax and abdomen
2. Appendages- three pairs of jointed legs
3. Ex: Romalea (grasshopper)
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Subphylum Chelicerata
Class Merostomata
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Subphylum Crustacea
Class Malacostraca
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Subphylum Uniramia
Class Insecta
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Class Diplopoda
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Class Chilopoda
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