Amphioxus



Amphioxus, also commonly known as Lancelet, are a group of primitive chordates. Lancelet.jpg
They are generally found buried in the sand in shallow parts of temperate or tropical seas. Amphioxus are very important in the study of zoology, as they provide indications about the origin's of vertebrates. [[http://en.wikipedia.org/wiki/Pharyngeal_slit|]]


Physical Attributes




Lancelets grow up to about five centimetres long, being eight centimetres at the longest. In common with the vertebrates, lancelets have a nerve cord running along the back, pharyngeal slits and a tail that runs past the anus. Also like vertebrates, the muscles are arranged in blocks called myomeres. Unlike the vertebrates, however, the dorsal nerve cord is not protected by bone, but a rather simpler notochord made up of a cylinder of cells that are closely-packed to form a toughened rod. The lancelet notochord, unlike the vertebrate spine, extends into the head. This gives the subphylum its name (cephalo- meaning 'relating to the head'). The lancelets also have oral cirri, thin tentacle-like strands that hang in front of the mouth and act as sensory devices and as a filter for the water passing into the body. The water exits the body via the atriopore.
(taken from: http://en.wikipedia.org/wiki/Amphioxus)

Scientific Classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Cephalochordata

400px-Lancetnikinside.png

  1. brain-like blister
  2. notochord
  3. dorsal nerve cord
  4. post-anal tail
  5. anus
  6. food canal
  7. blood system
  8. atriopore
  9. overpharynx lacuna
  10. gill slit
  11. pharynx
  12. vestibule
  13. oral cirri
  14. mouth opening
  15. gonads (ovary/testicle)
  16. light sensor
  17. nerves
  18. metapleural fold
  19. hepatic caecum (liver-like sack)