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AMPHIBIAN METAMORPHOSIS

AMPHIBIAN METAMORPHOSIS. METAMORPHOSIS :- the transition from a larval stage to an adult stage. MORPHOLOGICAL CHANGES ASSOCIATED WITH METAMORPHOSIS :- In amphibian, habitat changes from aquatic to the terrestrial. In urodeles (salamander):- These changes include the

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AMPHIBIAN METAMORPHOSIS

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  1. AMPHIBIAN METAMORPHOSIS • METAMORPHOSIS :- the transition from a larval stage to an adult stage. MORPHOLOGICAL CHANGES ASSOCIATED WITH METAMORPHOSIS :- In amphibian, habitat changes from aquatic to the terrestrial.

  2. In urodeles (salamander):- These changes include the • resorption of tail fin. • The destruction of the external gills. • Changes in the skin structure. In Anurans (frog and toad):- The metamorphic changes are more dramatic .

  3. Metamorphic changes in anurans

  4. Metamorphosis in amphibians is regulated by Thyroxin concentration in the blood which stimulates metamorphosis- which counteracts its effects. Specific events are dependent on threshold values for different tissue, because most embryonic development is subjected to specific ecological circumstance. After metamorphosis these organs become redundant and will be reabsorbed by controlled cell death called apoptosis.

  5. BIOCHEMICAL CHANGES • In tadpoles, ;- major retinol photopigment is porphyropin changes into the rhodopsin during metamorphosis. Tadpole haemoglobin changes into the adult haemoglobin that binds with oxygen more slowly Tadpole are ammonotelic adult ureotelic.

  6. HORMONAL CONTROL The control of metamorphosis by thyroid hormone was demonstrate byGuder-natch(1912) The metamorphic changes of frog development are all brought about by the secretion of hormones Thyroxin (T-4) and Triiodothyronine(T-3) from the thyroid during metamorphosis . It is thought that T-3 is the more important hormone, as it will cause metamorphic changes in thyroidectomized tadpole in much lower concentration than (T-4).

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