INSECT

HORMONES

Manduca sexta

Rhodnius prolixus

Main Endocrine Centres

Prothoracic (ecdysial) gland

Neurosecretory cells in VNC

Corpus allatum

Corpus cardiacum

Neurosecretory cells in SEG

Neurosecretory cells in brainBrain

Ovary

Corpora cardiaca

Corpora allata

Neuroendocrine Regulation

Central nervous system

Neurohemal organ

Neurosecretory cells

Neurohormone

Neurohormone

Hormone

Hormone

Endocrine gland

Target cell

• •• ••• • •• •

••

+/-

+/-+/-

+/-

+/-

+/-Target cell

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

Sensitive periods for JH

JH level

Ecdysone level

4th instar 5th instar

Outer epicuticle

Inner epicuticleEpicuticle

Exocuticle

Endocuticle

Epidermis

Basement membranePore canals

Procuticle

Moulting and Hormones

Moulting Cycle (Part 1)

Step 1 Step 2 Step 3/4

Moulting Cycle (Part 2)

Step 5-7 Ecdysis New Integument

CH2

CH2

CH3

CH3

CH3

CH3

CH3

CH2

O

O

O

C

C

CH

H

H

C CH2

C

CH3

CH3

CH2

CH2

CH3

CH3

CH3

CH3

CH3

CH2

O

O

O

C

C

CH

H

H

C CH2

C

CH3

CH2

CH2

CH3

CH3

CH3

CH3

CH3

CH2

O

O

O

C

C

CH

H

H

C CH2

C

Ecdysone

Juvenile hormone I

Juvenile hormone II

Juvenile hormone III

20-Hydroxyecdysone

Juvenile hormone

Penultimate larval instar Final larval instar Adult

JH sensitive period

JHTiter

Corpus cardiacum

Corpus allatum

Brain (neurosecretory cells)

Production, storage and release of protothoracicotropic hormone (PTTH}

PTTH stimulates

Ecdysone (ec)

Juvenile hormone (JH)

Binding protein (JHBP)

JH-JHBP 20-hydroxyecdysone

chromosomes

RNA

Protein synthesis

Larval structures

chromosomes

RNA

Protein synthesis

Pupal structures

chromosomes

RNA

Protein synthesis

Adult structures

Action pathway for JH and Ecdysone

Moulting video

http://www.vanderbilt.edu/exploration/news/news_bursicon.htm