Tardigrada

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Adapted from Lesser Known ProtostomePhyla. SICB
2001. J.R. Garey.
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Tardigrada
http//www.solutionassoc.com/Fun/Fun.html
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Tardigrada water bears

• First discovered in 1773
• 800 spp
• 0.1-0.5mm in length
• Widespread
• Live in semi aquatic habitats, water film
• Cryptobiotic, some are cyclomorphic
• Temp range from 149C to -272C, withstand high
  vacuum, high UV, long periods without O2
• Dessication for gt 120 years back to life in hours

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Tardigrada

• Metameric body plan
• Toes on each leg with intrinsic musculature (cf
  onychophoryans)
• Walk with muscles, not with hydrostatic skeleton
• Oral stylets pierce plant cell walls
• Diets specialized for predation, herbivory,
  detritivory
• Internal fertilization, shed cuticle with eggs

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Adapted from Lesser Known ProtostomePhyla. SICB
2001. J.R. Garey.
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Onychophorans velvet worms
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Onychophorans

• Discovered in 1826
• 110 spp, 5mm-15 cm
• Extant spp all terrestrial
• Humid habitats only
• Cuticle thin (no Ca), permeable
• 13-43 pairs of sac-like legs
• Metameric
• little tagmatization
• little cephalization
• Annelid/arthropod link
• Head polychaete

Oral slime papillae
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• Predaceous
• Spray adhesive goo from slime glands (modified
  nephridia) to entangle prey
• Gas exchange by trachea, spiracles
• Not homologous to arthropod trachea
• Reproduction
• Ovoparity, viviparity, ovoviviparity

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Phylum Arthropoda

• Arthro joint, poda feet
• Refers to hard, chitinous exoskeleton
• Terrestrialized annelid body plan
• Metameric
• Tagmatized
• head, thorax, abdomen
• cephalothorax, abdomen
• prosoma, opisthosoma
• Cephalized
• Compound eyes, antennae (mechano- chemosensory)

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P. Arthropoda
Modern crustacea
Myriapoda
Hexapoda
Chelicerata
Cenozoic (65-present)
Trilobita
Mesozoic (251-65 mya)
Paleozoic (542-251 mya)
Precambrian (gt542 mya)
Crustaceamorph stem line
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Phylum Arthropoda

• Subphylum Trilobita
• SubPhylum Chelicerata
• Class Merostomata horseshoe crabs
• Class Arachnida spiders, ticks
• Class Pycnogonida sea spiders
• Subphylum Hexapoda
• Class Entognatha
• Class Insecta !!
• SubPhylum Crustacea
• 6 subclasses

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Phylum Arthropoda

• Subphylum Trilobita
• Common 500 mya (4000 spp) but extinct by 225 mya
• Each body segment had a biramous appendage (inner
  for walking)
• 3 body tagma
• Compound eyes with ommatidia

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Subphylum Chelicerata

• Include spiders and mites and daddy LL,
  scorpions, horseshoe crabs
• Lack antennae
• 1st pair of appendages on the prosoma the
  chelicerae (adapted for feeding)

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Class Merostomata

• 4 spp, all marine
• Not true crabs (i.e., not crustaceans)
• head thorax prosoma or cephalothorax
• appendages of opisthosoma flattened to become
  book gills for gas exchange

Telson