post embryonic development metamorphosis- amphibians and insects tissue regeneration aging
TRANSCRIPT
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
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. 15.25And 15.26
Morphallactic Regeneration: Hydra• Basal disc/hypostome• Head activation/inhibition
gradients• Hypostome= “organizer”• Basal disc
activation/inhibition Fig. 15.25And 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