Phylum Arthropoda

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Phylum Arthropoda Phylum and Subphyla
Characteristics

• Phylum Characteristics segmented body (tagmata),
  chitinous exoskeleton jointed appendages
  highly developed sense organs and complex
  behavior patterns (incl. social systems)
• Overview of Diversity and Characteristics of
  Subphyla
• Subphylum Trilobita extinct trilobites (most
  common in the Paleozoic) cephalon (head
  segment) with compound eyes, mouth, and antennae
• Subphylum Chelicerata extinct eurypterids (up to
  3 m long), horseshoe crabs, sea spiders,
  spiders, scorpions, ticks, and mites six pairs
  of cephalothoracic appendages (incl. pair of
  chelicerae for sucking liquid food), plus four
  pairs of walking legs lack antennae
• Subphylum Myriapoda centipedes, millipedes,
  others mandibles one or two pairs of uniramous
  appendages on most or all trunk segments
• Subphylum Crustacea crabs, shrimps, and other
  aquatic forms biramous appendages, often
  modified gills present carapace
• Subphylum Hexapoda insects head, thorax, and
  abdomen three pairs of legs wings often
  present highly modified mouthparts

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Fig. 19.4
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Fig. 19.1
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Fig. 19.2
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Subphyla Chelicerata and Myriapoda

• Subphylum Chelicerata (extant forms)
• Horseshoe crabs hinged carapace and tail-like
  telson book gills trilobite larvae mass
  spawnings provide food for shorebirds
• Sea spiders (pycnogonids) most abundant in polar
  oceans some duplicated segments result in 5-6
  pairs of legs
• Class Arachnida (earliest terrestrial animals,
  Silurian)
• Spiders cephalothorax and abdomen joined by
  slender pedicel fangs with venom glands (incl.
  black widow, brown recluse, tarantulas) many
  with silk glands and webs eight simple eyes
  control populations of insects
• Scorpions stingers with venom glands (some can
  be fatal) complex mating dance viviparous
  development , young develop on females back
• Ticks and mites fusion of tagmata ticks suck
  blood and can spread disease (ex. Lyme disease)
  mites important agricultural pests include
  commensal hair follicle mite (Demodex) and itch
  mite (cause of scabies)
• Sun and whip scorpions include local camel
  spiders
• Subphylum Myriapoda paired appendages on nearly
  all trunk segments
• Class Chilopoda centipedes venomous, active
  carnivores (tropical species can be dangerous to
  humans) up to 177 segments with most bearing
  pair of jointed legs
• Class Diplopoda millipedes slow, herbivorous
  secrete toxic or repellent fluids from body
  abdominal segments with two pairs of legs (the
  appearance of a thousand feet)

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Fig. 19.5
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Fig. 19.6
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Fig. 19.7
Sonograph of Sea Spider Fossil
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Fig. 19.8
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Fig. 19.10
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Fig. 19.13
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Fig. 19.14
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Fig. 19.15
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Fig. 19.18 and 19.19
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Fig. 19.21
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Fig. 19.22
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Fig. 19.23
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The Crustaceans Diversity and Class
Characteristics

• Diversity insects of the sea about 67,000
  described species, some extremely abundant (ex.
  copepods)
• Class Remipedia inhabit caves with connections
  to the sea
• Class Branchiopoda include brine shrimp and
  water fleas (Daphnia)
• Class Ostracoda (ostracods) bivalved carapace
  many bioluminescent
• Class Maxillopoda include copepods (planktonic
  and parasitic forms), fish lice, and barnacles
  (sessile or parasitic as adults)
• Class Malacostraca most with hard carapace
  covering cephalothorax
• Order Isopoda dorsoventrally flattened, lack
  carapace include pill bugs, rock lice,
  parasitic forms, and deep-sea forms (some of
  which exhibit gigantism)
• Order Amphipoda laterally flattened lack
  carapace include kelp hoppers, skeleton
  shrimp, whale lice, and pelagic species (ex.
  Phronima)
• Order Euphausiacea (krills) carapace fused to
  thoracic segments but gills partially exposed
  abundant prey in Southern Ocean for baleen
  whales, penguins, crabeater seals, and others
• Order Decapoda crabs, shrimp, lobsters,
  crayfish often with chelae (pincers) support
  important fisheries (ex. Alaskan king crab)

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Fig. 20.1
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Fig. 20.14
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Fig. 20.15
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Fig. 20.16
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(No Transcript)
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Fig. 20.18
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Fig. 20.21
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Fig. 20.23
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Fig. 20.24
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Fig. 20.25
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Fig. 20.26
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Fig. 20.27
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Fig. 20.28
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The Crustaceans Structure and Development

• Structure two pairs of antennae, biramous
  appendages
• Serial homology and specialization of appendages
  (incl. mouthparts) decapods with five pairs of
  walking legs, abdominal swimmerets, and
  tail-like uropod
• Gills in larger forms extend from appendages or
  are internal (water pumped into gill cavities
  via pumping of second maxillae)
• Open circulatory system hemoglobin or hemocyanin
  (copper-based)
• Sensory systems include statocysts, tactile
  hairs, and compound eyes
• Development metamorphosis vs. direct development
  
• Common larval stages include nauplius (with
  single medial eye), zoea (crabs), cyprid
  (barnacles), and phyllasoma (lobsters)
• Molting cycle and ecdysis (shedding of cuticle)
  controlled by hormones
• Cuticle is non-living, must be shed as grows
  growth occurs during intermolt phases until
  space filled, absorbed water splits old
  cuticle, animal stays sheltered until new
  cuticle hardens

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Fig. 20.2
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Fig. 20.3
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Fig. 20.5
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Fig. 20.10
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Fig. 20.12