[C] Urochordata

• Urochordate Classes:

  1. Ascidiacea
  2. Larvacea
  3. Thaliacea
• Ascidiacea - Sea Squirts

  • Sessile adult, planktonic larvae
  • Larvae undergo metamorphosis, lose notochord, tail and DNC
  • Tunic attaches them to substrate
  • Stigmata sieve water
  • Monoecious and hermaphroditic, self-fertilization rare
  • Asexual reproduction via budding
• Larvacea

  • Marine planktonic urochordates 
  • Adults retain larval tadpole-like characteristics 
  • External feeding apparatus for filtering (house) 
  • Screens
  • Filters
  • Gelatinous matrix
  • The house can be discarded and a new one regenerated
• Thaliacea - salps

  • Marine planktonic urochordates (salps) 
  • Can be solitary or colonial 
  • Derivatives of adult ascidians 
  • Similar body plan, but
  • Incurrent and excurrent siphons at opposing ends (like tube/pipe)
  • Muscle bands encircling the test wall contract to push water