• • • Post Embryonic Development Metamorphosis- Amphibians and Insects Tissue Regeneration Aging

Metamorphosis: Overview • • Direct Developers Indirect Developers

• • Metamorphosis: Amphibians Hormones – – Thyroxine (T4) triiodothyronine (T3) Hormones cause: – Growth – – – Death Remodeling Respecification

• • • Hormones: Growth Growth and rearrangement Limbs Eyes

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

• • • Hormones: Remodeling Digestive tract Skull and gills Nervous system

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

• • • • Hormone function during Metamorphosis T4 secreted by Thyroid.

TR a = receptor for T3; ubiquitous TR b = receptor induced by hormones Stages of Hormone activity in Metamorphosis – – – Premetamorphosis Prometamorphosis Metamorphic climax

• • • • • Hormone function during Metamorphosis T4 secreted by Thyroid.

TR a = receptor for T3; ubiquitous TR b = receptor induced by hormones TR/RXR complexes Stages of Hormone activity in Metamorphosis – – – Premetamorphosis Prometamorphosis Metamorphic climax

Metamorphosis: Insects

Insect Imaginal Discs

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

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

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

Imaginal Discs: Wing Fig. 15.14

Imaginal Discs: Wing

Imaginal Discs: Wing • Figure 15.15

Hormonal Control of Insect Metamorphosis • Fig. 15.16

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)

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

Regeneration: Epimorphic

• Epimorphic regeneration requires nerves and AEC Newt anterior gradient protein (nAG).

• Fig 15.22

• • • • Morphallactic Regeneration: Hydra Basal disc/hypostome Head activation/inhibition gradients Hypostome= “organizer” Basal disc activation/inhibition Fig. 15.25

And 15.26

• • • • Morphallactic Regeneration: Hydra Basal disc/hypostome Head activation/inhibition gradients Hypostome= “organizer” Basal disc activation/inhibition Fig. 15.25

And 15.26

Compensatory Regeneration: Liver

Aging

• • 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?

• • • Aging DNA repair enzymes p53 Insulin Signaling

We’re staying alive… Fig. 15.35

DNA methylation and Early Bird Specials.

Fig 15.36 and 15.37