1. Post Embryonic Development
Metamorphosis- Amphibians and Insects
Tissue Regeneration
Aging

2. Metamorphosis: Overview
Direct Developers
Indirect Developers

3. Metamorphosis: Amphibians
Hormones
Thyroxine (T4)
triiodothyronine (T3)
Hormones cause:
Growth
Death
Remodeling
Respecification

4. Hormones: Growth
Growth and rearrangement
Limbs
Eyes

5. Hormones: Cell Death T3 and tail degeneration
Concomitant with adult leg generation.

6. Hormones: Remodeling
Digestive tract
Skull and gills
Nervous system

7. Hormones: Biochemical Respecification
Tadpole is ammonotelic
After morphogenesis, Frogs are ureotelic.

8. Hormone function during Metamorphosis
T4 secreted by Thyroid.
TRa= receptor for T3; ubiquitous
TRb= receptor induced by hormones
Stages of Hormone activity in Metamorphosis
Premetamorphosis
Prometamorphosis
Metamorphic climax

9. Hormone function during Metamorphosis
T4 secreted by Thyroid.
TRa= receptor for T3; ubiquitous
TRb= receptor induced by hormones
TR/RXR complexes
Stages of Hormone activity in Metamorphosis
Premetamorphosis
Prometamorphosis
Metamorphic climax

10. Metamorphosis: Insects

11. Insect Imaginal Discs
Try to find good model for this

12. Metamorphosis: Fly and Leg formation
Wingless (Wg); Wnt homolog
Decapentaplegic (Dpp); BMP homolog
Distal-less and Dachshund
20-hydroxyecdysone (20-E)

13. Metamorphosis: Fly and Leg formation
Wingless (Wg); Wnt homolog
Decapentaplegic (Dpp); BMP homolog
Distal-less and Dachshund
20-hydroxyecdysone (20-E)

14. Metamorphosis: Fly and Leg formation
Wingless (Wg); Wnt homolog
Decapentaplegic (Dpp); BMP homolog
Distal-less and Dachshund
20-hydroxyecdysone (20-E)

15. Imaginal Discs: Wing
Fig

16. Imaginal Discs: Wing

17. Imaginal Discs: Wing
Figure 15.15

18. Hormonal Control of Insect Metamorphosis
Fig

19. Regeneration
Stem-cell mediated regeneration
Epimorphosis
Morphallaxis
Compensatory regeneration
“I’d give my right arm to know the secret of regeneration”
-Oscar E. Schotte (1950)

20. Regeneration: Epimorphic
Limb regeneration in Salamanders
Regeneration blastema
Wound epidermis
Apical epidermal cap (AEC)

21. Regeneration: Epimorphic

22. Epimorphic regeneration requires nerves and AEC
Newt anterior gradient protein (nAG).
Fig 15.22

23. Morphallactic Regeneration: Hydra
Basal disc/hypostome
Head activation/inhibition gradients
Hypostome= “organizer”
Basal disc activation/inhibition
Fig
And 15.26

24. Morphallactic Regeneration: Hydra
Basal disc/hypostome
Head activation/inhibition gradients
Hypostome= “organizer”
Basal disc activation/inhibition
Fig
And 15.26

25. Compensatory Regeneration: Liver

26. Aging

27. Genetics and Aging
How can evolution select for a way to degenerate?
How can evolution select for phenotypes that can postpone reproduction or sexual maturity?

28. Aging
DNA repair enzymes
p53
Insulin Signaling

29. We’re staying alive…
Fig

30. DNA methylation and Early Bird Specials.
Fig and 15.37