Prochordates

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S.Seethakutty
Chettinad Vidya Mandir
Karur,Tamil Nadu

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Prochordates

  1. 1. Kingdom Animalia chordates non-chordates (presence of notochord.) (absence of notochord.)
  2. 2. The notochord serves as a guide for the axial skeleton.
  3. 3. Therefore, can all animals be classified as chordates and non-chordates? The answer is NO.
  4. 4. Some animals like Balanoglossus
  5. 5. have a notochord,which is not present at all stages in their lifecycle, nor does it run the entire length of an animal’s body. Therefore, these animals are kept in a separate sub-phylum named Protochordata Amphioxus
  6. 6. Saccoglossus
  7. 7. Classification of Protochordata or Acraniates The notochord is only present in the tail of the larva and disappears in the adult
  8. 8. Adult Tunicata
  9. 9. BLUE BELL TUNICATE The tunic may shelter a single animal (as here), or a colony composed of clones budded from a parent individual
  10. 10. Unusual in having an outer skin ('test' or 'tunic') composed of carbohydrates - structural polymers more usually associated with plants..
  11. 11. Transparent outer skin or tunic, through which relatively complex internal structures are clearly visible.
  12. 12. Sub-phylum 1. Urochordata This sub-phylum is also called Tunicata because the adult body is enclosed within a leathery test or tunic formed of a cellulose-like organic substance termed tunicin .  
  13. 13. The notochord is only present in the tail of the larva ( hence named urochardata) and disappears in the adult.  
  14. 14. The pharynx is perforated by numerous apertures called stigmata formed by sub-division of the larval gill slits.
  15. 15. The stigmata open into an ectoderm lined cavity, the atrium.
  16. 16. The larva (tadpole) undergoes retrogressive metamorphosis , i.e., change from better developed larva to less developed adult, e.g., Herdmania (Sea squirt) . Dorsal ganglion is found in adult which is formed from dorsal tubular nerve cord of larva.  
  17. 17. Vanadocytes(BLOOD CELLS) are present except Herdmania. Excretion, by neural gland, pyloric gland and nephrocyte.
  18. 18. Circulatory system is open in tunicates.
  19. 21. Examples: Herdmania (Sea squirt),
  20. 22. Salpa
  21. 23. Doliolum,
  22. 24. Oikopleura etc.
  23. 25. Herdmania
  24. 26. Pyrosoma a colonial phosphorescent form .
  25. 27. Sub-phylum 2. Cephalochordata The notochord extends upto anterior end of the body hence this sub-phylum is named
  26. 28. The notochord persists throughout life .
  27. 29. Pharyngeal gill slits are more numerous and are better developed.  
  28. 30. The tail is present throughout life, e.g., Branchiostoma (=Amphioxus).  
  29. 31. A wheel organ of producing currents of water in vestibulae.  
  30. 32. Paired appendages absent, median fins (dorsal, ventral and caudal) are present.
  31. 33. Amphioxus has both ends pointed like lens hence it is commonly called lancelet.

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