Thyroid Hormones and Postembryonic Development in Amniotes - Current Topics in Developmental Biology - page 390

CHAPTER FOURTEEN

Thyroid Hormones and
Postembryonic Development in
Amniotes

Guillaume Holzer, Vincent Laudet 1
Molecular Zoology Team, Institut de G´nomique Fonctionnelle de Lyon, ´ cole Normale Sup´rieure de Lyon,
UMR5242 CNRS, Universit´ Lyon, France
1 Corresponding author: e-mail address: [e-mail]

Contents
1. Introduction 398

2. TH Signaling: The Basics 399

3. TH Controls Metamorphosis in Amphibians 402

3.1 Metamorphosis in anurans 402

3.2 Metamorphosis variation in amphibians 404

3.3 Direct development in amphibians 405

4. TH-Regulated Metamorphosis is an Ancestral Chordate Character 405

5. Mammals 406

5.1 TH levels in eutherian mammals 406

5.2 Role of TH in late gestation and early postembryonic life: data from mice 408

5.3 What about other mammals? 410

5.4 The young mammal as a larva? 411

5.5 The special case of marsupials 413

5.6 A partial conclusion on mammals 414

6. Sauropsids 415

6.1 TH levels during development in birds 415

6.2 TH levels in heterotherm sauropsids 416

6.3 Effect of TH in bird 417

6.4 A “ metamorphosis ” in sauropsids? 418

7. Conclusion 419

Acknowledgments 420

References 420

Abstract
In chordates, metamorphosis is a developmental event well described in amphibians in
which thyroid hormone triggers this event. Interestingly, among amphibians, several
variations upon the eggs/tadpole/frog developmental sequence are observed such
as direct development or neoteny. The fact that TH-regulated metamorphosis is con-
served in invertebrate chordates such as amphioxus implies that this event is an ancient