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. TRa= receptor for T3; ubiquitous TRb= receptor induced by hormones Stages of Hormone activity in Metamorphosis Premetamorphosis Prometamorphosis Metamorphic climax

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

Metamorphosis: Insects

Insect Imaginal Discs Try to find good model for this

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