This document discusses metamorphosis in amphibians. It begins by defining metamorphosis and noting that it occurs in both invertebrates and chordates, including amphibians. It then describes the characteristics of amphibians and the differences between the larval and adult stages of anurans, or tailless amphibians. The document outlines the developmental stages from embryo to larva to adult. It details the changes that occur during the prometamorphic and metamorphic climax periods of metamorphosis in Rana pipiens frogs. Finally, it briefly mentions some other highlights of amphibian metamorphosis, including the role of hormones and iodine.

1. TKR
Presents
METAMORPHOSIS IN
AMPHIBIANS

2. Introduction
Metamorphosis is tranformation or change from
one form to another.
Metamorphosis is seen both in invertebrates and
chordates.
For example insects, echinoderms,amphibians,
fishes and so on.

4. AMPHIBIANS
 Amphibians is a class under chordates.
 They are found almost everywhere.
 These are the group of amphibians that show link
between aquatic and terrestrial mode of life.
 Some charachterstic feature of amphibians are they are
cold blooded, have three chambered heart, 10 pairs of
cranial nerves, undergo indirect development.

5. Comparison between larval and adult
stage in Anurans
Larval Stage Adult Stage
 Gills present, larval hb.
 Herbivores, long digestive
tract, small mouth.
 Nictitating membrane
absent, porphyropsin.
 Largely ammonia.
 Thin skin, no mucous
gland.
 Gills absent, lungs well
developed, adult hb.
 Carnivores, short digestive
tract, large mouth.
 Nictitating membrane
present, rhodopsin.
 Largely urea.
 Thick skin, mucous glands.

6. Devlopment
 Stages of growth can be roughly divided as:
1. Embryo
2. Larva
3. Adult
 Stages of metamorphosis can be roughly divided into:
1. Prematamorphic period
2. Prometamorphic period
3. Metamorphic climax

7. Changes During Metamorphosis
 Premetamorphic period in Rana pipiens last for 7 weeks.
 It’s the growth period without much change in body
 With emergence of hind limb starts the “Prometamorphic period”.
 This period is marked with most of the changes and lead to
metamorphic climax.
 The changes in prometamorphic change includes growth of hind
limbs, thinning of operculum, appearance of forelimbs, reposition of
eyes, shift in position of anus, mouth becomes wider, muscular jaws
develops, tail and gills are completely reabsorbed.
 The rapid series of events following emergence of forelimbs to
achieve definite adult body are designated collectively as
metamorphic climax.
 The most dramatic change during climax is reabsorption of tadpole
tail.

9. Other Highlights Of Metamorphosis
 These events are coordinated i.e. limbs develop first before
tail regresses.
 Different tissues require different threshold dose of hormone
to undergo changes.
 Main hormones playing role in metamorphosis is thyroxin,
prolactin.
 Element influencing metamorphosis is Iodine.
 Iodine has been seen to cause metamorphosis even in
thyroidectomized axolotl.
 Metabolites available from tissue destruction are available for
other anabolic process.
 Double metamorphosis.
 Paedomorphosis.

10. Thank you