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BY :-
IQRAASLAM
Bs zoology 5th
METAMORPHOSIS
 the process of transformation
 immature adult form
 two or more distinct stages.
 In an insect or amphibian
AMPHIBIAN METAMORPHOSIS
 amphi ("double") and bios ("life")
 aquatic terrestrial existence
 urodeles (salamanders)
 resorption of the tail fin
 destruction of the external gills
 skin structure
continue
Morphological changes
1. GROWTH OF NEW STRUCTURES
2. CELL DEATH
3. REMODELING
4. BIOCHEMICAL RESPECIFICATION
Conti…..
1.GROWTH OF NEW STRUCTURES
 limbs emerge
 nictitating membranes and eyelids
 Lateral eyes front eyes
 New neurons spinal cord
 Ephrin B cause ipsilateral
Eye migration and associated neuronal changes during metamorphosis
of the Xenopus laevis tadpole
2. CELL DEATH
 the paddle-like tail
 Recent evidence ,
 Apoptosis …….. caspase-9
 Phagocytosis ……. Proteases
 Gills
 red blood cells

Shape of cells & hemoglobin
3. REMODELING
 larval intestine ….. shorter
 Schrieber experiment
 metalloproteinase stromelysin-3
Conti…….
 optic nerve pathway
 motor neurons , tadpole jaw
 lateral line system degenerates
 ear differenciations …a brief period of deafness
 SKULL
 tadpole skull is primarily
neural crest-derived
cartilage……..
 adult skull is primarily
neural crest-derived bone
Changes in the Xenopus skull during metamorphosis.
4.BIOCHEMICAL RESPECIFICATION
 Liver
 synthesize the enzymes
 Ammonotelic……. ureotelic
Hormonal control
 1912 by Gudernatsch
 fed powdered horse thyroid glands
 Allen (1916
 destroyed the thyroid
 threshold model
low concentration ……..development of limbs
increasing amounts ….. resorption of the tail
Metabolism of (T4) and
(T3).
 Hormone receptor
 (TRa)………….. all tissues , before thyroid gland
 (TRB)…………. activated by thyroid hormones.
 Stages of metamorphosis
1.premetamorphosis
 CRH….. (TSH), …..T4…… low amounts of T3.
 High levels of deiodinase II before secretion of t4….T3
 limb rudiments
 Metamorphic climax stage
 concentration of T4 rises
 TRB levels peak inside the cells
 deiodinase II is expressed as tail resorption, gill
resorption, and intestinal remodeling
Regionally specific developmental programs
Thank you

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Dev bio

  • 1.
  • 3. METAMORPHOSIS  the process of transformation  immature adult form  two or more distinct stages.  In an insect or amphibian
  • 4. AMPHIBIAN METAMORPHOSIS  amphi ("double") and bios ("life")  aquatic terrestrial existence  urodeles (salamanders)  resorption of the tail fin  destruction of the external gills  skin structure
  • 6. Morphological changes 1. GROWTH OF NEW STRUCTURES 2. CELL DEATH 3. REMODELING 4. BIOCHEMICAL RESPECIFICATION
  • 7. Conti….. 1.GROWTH OF NEW STRUCTURES  limbs emerge  nictitating membranes and eyelids  Lateral eyes front eyes  New neurons spinal cord  Ephrin B cause ipsilateral
  • 8. Eye migration and associated neuronal changes during metamorphosis of the Xenopus laevis tadpole
  • 9. 2. CELL DEATH  the paddle-like tail  Recent evidence ,  Apoptosis …….. caspase-9  Phagocytosis ……. Proteases  Gills  red blood cells  Shape of cells & hemoglobin
  • 10. 3. REMODELING  larval intestine ….. shorter  Schrieber experiment  metalloproteinase stromelysin-3
  • 11. Conti…….  optic nerve pathway  motor neurons , tadpole jaw  lateral line system degenerates  ear differenciations …a brief period of deafness
  • 12.  SKULL  tadpole skull is primarily neural crest-derived cartilage……..  adult skull is primarily neural crest-derived bone
  • 13. Changes in the Xenopus skull during metamorphosis.
  • 14. 4.BIOCHEMICAL RESPECIFICATION  Liver  synthesize the enzymes  Ammonotelic……. ureotelic
  • 15. Hormonal control  1912 by Gudernatsch  fed powdered horse thyroid glands  Allen (1916  destroyed the thyroid  threshold model low concentration ……..development of limbs increasing amounts ….. resorption of the tail
  • 16. Metabolism of (T4) and (T3).
  • 17.  Hormone receptor  (TRa)………….. all tissues , before thyroid gland  (TRB)…………. activated by thyroid hormones.
  • 18.  Stages of metamorphosis 1.premetamorphosis  CRH….. (TSH), …..T4…… low amounts of T3.  High levels of deiodinase II before secretion of t4….T3  limb rudiments
  • 19.  Metamorphic climax stage  concentration of T4 rises  TRB levels peak inside the cells  deiodinase II is expressed as tail resorption, gill resorption, and intestinal remodeling