1. INSECT HORMONES

2. Manduca sexta
Rhodnius prolixus

3. Main Endocrine Centres
Neurosecretory cells in brain
Brain
Neurosecretory cells in SEG
Prothoracic (ecdysial) gland
Corpus cardiacum
Corpus allatum
Neurosecretory cells in VNC
Ovary

8. Neuroendocrine Regulation
Central nervous system
Neurosecretory cells
+/-
+/-
+/-
Hormone • • • • • • • • • • • •
Neurohormone
Neurohemal organ
+/-
Neurohormone
Endocrine gland
+/-
Hormone
Target cell
+/-
Target cell

9. Physiological Actions of Hormones
1. Metabolism and homeostasis
* Metabolism of carbohydrates, lipids
* Water balance and diuresis (excretion of water following a blood meal)
* Cardioactive and muscle stimulation/inhibition
2. Growth, molting and metamorphosis
3. Reproduction
4. Diapause = state of arrested development
* Any stage - egg, larval, pupal, adult
5. Phase or caste polymorphism
* Social insects - ants, termites, honeybees
* Locusts and aphids show phase polymorphism
6. Behaviour
* During molting process
* Migration
* Reproductive behavior
* Social behavior
* Pheromones

10. Sensitive periods for JH
JH level
Ecdysone level
4th instar
5th instar

11. Moulting and Hormones Outer epicuticle Epicuticle Inner epicuticle
Exocuticle
Procuticle
Endocuticle
Epidermis
Basement membrane
Pore canals

12. Moulting Cycle (Part 1)
Step 1
Step 2
Step 3/4

13. Moulting Cycle (Part 2)
Step 5-7
Ecdysis
New Integument

14. Insect Moulting 2 1 3 4 OLD 5 epi- exo- endo- epithelial cells
subcuticular space
moulting fluid
epi-
OLD
exo- 3
Ecdysial membrane
New epicuticle-
Undifferentiated procuticle 4
Cuticlin layer 5
Epithelial cells

15. Ecdysone Juvenile hormone I Juvenile hormone II 20-Hydroxyecdysone
CH3
CH3
CH3
CH3 O
CH3
CH2
CH2
CH3 C H C
CH2
CH2 O C H C C O
CH3
CH3 H
Ecdysone
CH3
Juvenile hormone I
CH3 O
CH3
CH2
CH2
CH3 C H C
CH2
CH2 O C H C C O
CH3 H
CH3
Juvenile hormone II
CH3 O
CH3
CH2
CH2
CH3 C
20-Hydroxyecdysone H C
CH2
CH2 O C H C C O
CH3 H
Juvenile hormone III

16. (neurosecretory cells)
Action pathway for JH and Ecdysone
Brain
(neurosecretory cells)
Production, storage and release of protothoracicotropic hormone (PTTH}
Corpus cardiacum
Corpus allatum
PTTH stimulates
Juvenile hormone (JH)
Binding protein (JHBP)
Ecdysone (ec)
JH-JHBP
20-hydroxyecdysone
chromosomes
chromosomes
chromosomes
RNA
RNA
RNA
Protein synthesis
Protein synthesis
Protein synthesis
Larval structures
Larval structures
Larval structures

17. Moulting video