insect hormones

1. ROLE OF HORMONES ON
CONTROLLING GROWTH AND
DEVELOPMENT OF INSECTS

2. What is Hormone?
 Hormones are chemicals produced by an organism which
circulate in blood to regulate its long term physiological,
developmental and behavioral activities.
 Growth and development in insects control by series of
hormones which are secreted in predetermine sequences.
 Prothoracicotropic hormone (PTTH) was the first insect
hormone to be discovered by early workers such as Stefan
Kopec (1922) and Vincent Wigglesworth (1934) as “Brain
hormone”.

3. ENDOCRINE GLANDS IN INSECTS
Glands Secretions
Neurosecretory cells Produce Neurosecretion
Prothoracic glands Produce Ecdysone
Corpora allata Produces JH
Corpora cardiaca Stores and releases brain hormones
Also produces and releases some peptides
such as Adipokinetic Hormone
Midgut endocrine cells Produce various peptides
Epitracheal glands Produce the ecdysis triggering hormone
“Eclosion” in Lepidoptera

6. NEUROSECRETORY HORMONES
BRAIN HORMONE:
 NSC in dorsal part of protocerebrum produce a
hormone called Prothoracicotropic Hormone(PTTH)
or BRAIN HORMONE which activates prothoracic
glands.
 Mostly this hormone is constituted of lipid or peptide
and water soluble polypeptide or small molecule of
protein.

7. BURSICON:
 Neurosecretory hormone that controls Tanning or
Sclerotization and mechanical properties of the
cuticle during and after a moult.
 Found in most ganglia of the CNS.
DIURETIC HORMONE:
 Neurosecretory cells scattered in the ventral nerve
cord produce Diuretic hormone.
 It involved in regulation of Insect water balance.

8. Functional significance of
NEUROSECRETORY HORMONES
 The secretions of the median neurosecretory cells
promote the functioning of the prothoracic glands
stimulate protein synthesis, probably control water
loss and oocyte development activities.
 Neurosecretory hormones have also been associated
with behavioural activities, such as, response of the
female towards the male, cocoon formation etc.

9. HORMONES FROM
CORPORA CARDIACA
 Corpora cardiaca found in most insects except
Collembola, which lies on each sides of Aorta behind
brain.
 It acts as a Conventional storage and release organ for
neurohormones.
Adipokinetic Hormone(s):
 Adipokinetic hormone (AKH), a decapeptide from
the locust has been identified. AKH in CC of locusts
regulates lipid metabolism during prolonged flight.

10. Neurohormone D:
 Material isolated from CC of Caracius morosus
called Neurohormone D which increasing the
frequency of amplitude of Heart beat, stimulating
colour change in Caracius.
Chloride- Transport stimulating hormone:
 In Desert Locust, rectum of insect is an important
organ, which regulates the ionic balance. It is
stimulated by the hormone from Corpora cardiaca,
the Chloride- Transport stimulating hormone.

11. JUVENILE HORMONE / NEOTININ
 Corpora allata secretes Juvenile hormone (JH) or
Neotinin, there by inhibit metamorphosis. This CA
hormone(s) is therefore sometimes also called as
“Inhibitory or Status Quo” Hormone.
 Corpora allata glands were discovered by JANET
during 1899.
 JH first extracted from the abdomen of Hyalophora
cercopia (Moth).

12. Functional significance of
JUVENILE HORMONES
 It is needed for egg maturation and function as
accessory glands in male.
 Other activities controlled by this hormone are
polymorphism, regeneration, metabolism of fat, water
balance, colour changes, imaginal diapause,
pheromone production etc.

13. ECDYSONE / MOULTING HORMONE
/ECDYSTERIOD
 Neurosecretory cells activate prothoracic glands to
secrete ECDYSONE.
 First experimental proof about the importance of
Prothoracic glands was provided by a Japanese
worker, Fukuda in 1940 while working with
silkworm.

15. Functional significance of
ECDYSONE
 It initiates the moulting process.
 It breaks larval and pupal diapauses.
 Renewals of growth and deposition of new cuticle.
 MH is interference in principal enzyme system,
regulate normal metabolism and growth.
Ex. Cytochrome oxidase
 It influences the puffing pattern of giant cell in
Drosophila & Chironomous.
 It inhibits the function of Corpora allata.

16. OTHER HORMONES
PEPTIDE HORMONES:
 It is known to control wide range of physiological,
Biochemical and Developmental function including water
balance, lipid and carbohydrate metabolism, muscle
contraction, reproduction, growth and development.
PROCTOLIN:
 Isolated from Periplanata americana. It acts as an
Excitatory Neurotransmitter to modulate Muscle
Excitability.

17. Functions of Endocrine Hormones
 Regulation of Moulting
 Determination of form at Metamorphosis
 Polymorphism
 Regulation of Diapause
 Involvement in Reproduction
 Regulation of Metabolic activities and general body
functions
 Regulation of Behaviour