A morphogenetic hormone. Has multiple functions and a primary role of JH in insect development is to modulate ecdysone action. Maintains the current commitment of the tissues and cells whereas ecdysone causes both predifferentiative and differentiative cellular events that are necessary for the moult. When JH is present, a moult to a larval stage ensures. If JH is absent at the onset of the moult, morphogenesis occurs. Further studies and researches are still going on that can elucidate new

1. M. Phil (Zoology), 2nd Semester
Roll: BUR MP ZOO No.: 2008 / 9
Registration No.: 2546 of 2008 – 2009
The University of Burdwan
Burdwan – 713 104
West Bengal, India
SARAMITA DE (CHAKRAVARTI)

2. Moulting and development are controlled by
three main hormones -
Brain
Neurosecretory cells
Corpus cardiacum
Corpus allatum
EARLY
LARVA
LATER
LARVA PUPA ADULT
Prothoracic
gland
Ecdysone
Brain
hormone (BH)
Juvenile
hormone
(JH)
Low
JH
Neurosecretory cells in the brain produce
brain hormone (BH), which is stored in
the corpora cardiaca (singular, corpus
cardiacum) until release.
1
BH signals its main target
organ, the prothoracic
gland, to produce the
hormone ecdysone.
2
Ecdysone secretion
from the prothoracic
gland is episodic, with
each release stimulating
a molt.
3
Juvenile hormone (JH), secreted by the corpora allata,
determines the result of the molt. At relatively high concen-
trations of JH, ecdysone-stimulated molting produces
another larval stage. JH suppresses metamorphosis.
But when levels of JH fall below a certain concentration, a
pupa forms at the next ecdysone-induced molt. The adult
insect emerges from the pupa.
4

3. What is a Juvenile Hormone?What is a Juvenile Hormone?
A sesquiterpenoid molecule that –A sesquiterpenoid molecule that –
 Regulator of insect developmentRegulator of insect development
 Prevents adult differentiationPrevents adult differentiation
 Retains larval structuresRetains larval structures
 Regulates the ovarian maturationRegulates the ovarian maturation
 Modulates Ecdysone actionModulates Ecdysone action
 Key player for phase polymorphismKey player for phase polymorphism

4. JH synthesized and releasedJH synthesized and released
by -by -
► Prothoracic glands stimulated by PTTHProthoracic glands stimulated by PTTH
(Prothoracicotropic Hormone), which is(Prothoracicotropic Hormone), which is
produced by neurosecretory cells in the brainproduced by neurosecretory cells in the brain
and released from the terminals of eitherand released from the terminals of either
Corpora Cardiaca (CC) or Corpora AllataCorpora Cardiaca (CC) or Corpora Allata
(CA).(CA).

5. Isolation of Juvenile Hormones
 Williams (1956) found a lipid extract from the
abdomen of Hyalophora cecropia males produced JH
effects in Coleoptera (Tenebrio molitor) and in Bugs
and cockroaches and also in other moths.

6. Chemical Characteristics of
Juvenile Hormones
 The chemical identification of active principle (by gas
chromatography) was facilitated by the experiment on
Hyalophora cecropia (Williams, 1956).
 Chemical formula of male Hyalophora cecropia extract as
Methyl – 10- epoxy – 7 ethyl – 3, 11 – dimethyl 2, 6
tridecadienoate or methyl – 12, 14 – dihomo juvenate
(Meyer, 1970).

7. Chemical Structure of Juvenile Hormone
and
its one of the Analogue (Juvabione)
Juvenile hormone
Juvabione

8. Juvenile Hormone content of
Hyalophora cecropia during development
(After Schneiderman, 1961)
Stages of DevelopmentStages of Development JH content / gm fresh weightJH content / gm fresh weight
compared with adult male (in %)compared with adult male (in %)
1. Unfertilized Eggs1. Unfertilized Eggs 4.304.30
2. 7 – days old Embryos with yolk2. 7 – days old Embryos with yolk 3.703.70
3. 13. 1stst
instar larvae (freshly hatched)instar larvae (freshly hatched) 6.406.40
4. 54. 5thth
instar larvae (mixed ages)instar larvae (mixed ages) 0.500.50
5. Freshly moulted pupae5. Freshly moulted pupae 0.750.75
6. Diapausing Pupae (1 month old)6. Diapausing Pupae (1 month old) 0.550.55
7. Chilled Pupae (6 months old)7. Chilled Pupae (6 months old) 0.000.00
8. Pupae 2 days of adult development8. Pupae 2 days of adult development 0.000.00
9. Pupae 11 days of adult development9. Pupae 11 days of adult development 0.000.00
10. Pupae 17 days of adult development10. Pupae 17 days of adult development 0.000.00
11. Pupae 20 days of adult development11. Pupae 20 days of adult development 0.500.50
12. Pupae 22 days of adult development (males)12. Pupae 22 days of adult development (males) 50.0050.00
13. Adult males, 2 days old13. Adult males, 2 days old 100.00100.00
14. Adult females, 2 days old14. Adult females, 2 days old 3.203.20

9. Observations -
 JH content is fairly high in unfertilized eggs,
during embryonic period and in freshly
hatched larvae.
 JH content decreases at the end of larval
development and in pupa, disappears and
does not reappear until just before adult
emergence; in females increases slowly, but
rapidly in males.

10. JH Variants
 There are six variants of Juvenile Hormones
namely – JH I, JH II, JH III, JH 0, iso JH 0
and methyl farnesoate.
 JH I and JH II are the principal JHs and JH
III is traceable.

11. Molecules with JH activity

12. Juvenoids or JH AnaloguesJuvenoids or JH Analogues
(JHa)(JHa)
 A number of substances having physiological activityA number of substances having physiological activity
more or less identical with that of some of insectmore or less identical with that of some of insect
hormones are found in extracts of other animalhormones are found in extracts of other animal
tissues and various plants.tissues and various plants.
 To date, over 100 synthetic Juvenoids or JHa haveTo date, over 100 synthetic Juvenoids or JHa have
been produced.been produced.
 They can be used to analyze all problems of insectThey can be used to analyze all problems of insect
growth and morphogenesis far more easily andgrowth and morphogenesis far more easily and
thouroughly than by corpora allata transplantationthouroughly than by corpora allata transplantation
method.method.
 They offer prospects of biological control of newThey offer prospects of biological control of new
types.types.

13. Biological activity and RF values of the authentic
juvenile hormone and the synthesized compounds *
(After Dahm et al., 1968)
Name of the CompoundName of the Compound Specific ActivitySpecific Activity
(Tu / µg)(Tu / µg) ****
RRFF******
1. t, t – C1. t, t – C1212 – ethyl – ester (VI)– ethyl – ester (VI) Inactive (at 10µg / animal)Inactive (at 10µg / animal) 0.670.67
2. c, t – C2. c, t – C1212 – ethyl – ester– ethyl – ester Inactive (at 10µg / animal)Inactive (at 10µg / animal) 0.710.71
3. t, t – C3. t, t – C1515 – ketone (VIII)– ketone (VIII) 55 0.480.48
4. t, t, t – C4. t, t, t – C1717 – methyl – ester (IX)– methyl – ester (IX) 200200 0.670.67
5. t, c, t – C5. t, c, t – C1717 – methyl – ester– methyl – ester 3030 0.670.67
6. c, t, t – C6. c, t, t – C1717 – methyl – ester– methyl – ester 11 0.730.73
7. c, c, t – C7. c, c, t – C1717 – methyl – ester– methyl – ester 11 0.730.73
8. dl – t, t, t – 10 – epoxy – C8. dl – t, t, t – 10 – epoxy – C1717 – methyl – ester (X)– methyl – ester (X) 20002000 0.400.40
9. dl – t, c, t – 10 – epoxy – C9. dl – t, c, t – 10 – epoxy – C1717 – methyl – ester (XIII)– methyl – ester (XIII) 150150 0.400.40
10. dl – t, c, t – 10 – epoxy – C10. dl – t, c, t – 10 – epoxy – C1717 – methyl – ester (XIV)– methyl – ester (XIV) 1010 0.410.41
11. dl – c, c, t – 10 – epoxy – C11. dl – c, c, t – 10 – epoxy – C1717 – methyl – ester (XV)– methyl – ester (XV) 1010 0.410.41
12. dl – t, t, t – 6 – epoxy – C12. dl – t, t, t – 6 – epoxy – C1717 – methyl – ester (XI)– methyl – ester (XI) 200200 0.440.44
13. Juvenile Hormone (from13. Juvenile Hormone (from H. cecropiaH. cecropia oil)oil) 200200 0.400.40* = All compounds were obtained by gas chromatography in pure state* = All compounds were obtained by gas chromatography in pure state
** = Tu / µg means Tenebrio Units per Microgram** = Tu / µg means Tenebrio Units per Microgram
*** = Thin Layer Chromatography on Silica Gel G (E. Merck) activated 2 hrs. at*** = Thin Layer Chromatography on Silica Gel G (E. Merck) activated 2 hrs. at
120ºC, Benzene:Ethyl acetate = 15:1120ºC, Benzene:Ethyl acetate = 15:1

14. The Mevalonate Pathway (MP) and Synthesis
of the Juvenile Hormones
 A ramified metabolic route based on reductiveA ramified metabolic route based on reductive
polymerization of acetyl – CoA.polymerization of acetyl – CoA.
 Final products of MP include hormonal messengers.Final products of MP include hormonal messengers.
 Important peculiarities in mevalonate pathway are –Important peculiarities in mevalonate pathway are –
- absence of the sterol branch- absence of the sterol branch
- synthesis of juvenile hormones- synthesis of juvenile hormones

16. Regulation of Mevalonate PathwayRegulation of Mevalonate Pathway
and Synthesis of JHand Synthesis of JH
JH itself a key regulatory element of mevalonate pathway.JH itself a key regulatory element of mevalonate pathway.
Cholesterol does not regulate the Mevalonate pathway.Cholesterol does not regulate the Mevalonate pathway.
A recent study onA recent study on I. piniI. pini using quantitative real time PCRusing quantitative real time PCR
examined feeding – induced changes in gene expression ofexamined feeding – induced changes in gene expression of
seven mevalonate pathway genes.seven mevalonate pathway genes.
In male all these 7 genes are expressed, but in femalesIn male all these 7 genes are expressed, but in females
only the first 5 genes are expressed.only the first 5 genes are expressed.

17. Regulation of Mevalonate PathwayRegulation of Mevalonate Pathway
and Synthesis of JHand Synthesis of JH
In insects, mevalonate pathway can beIn insects, mevalonate pathway can be
interpreted in terms of the coordinatedinterpreted in terms of the coordinated
regulation and metabolic controlregulation and metabolic control
analysis, rather than in terms of a keyanalysis, rather than in terms of a key
regulatory step.regulatory step.

18. Cellular Receptors for JHCellular Receptors for JH
 A 29 kDa nuclear protein, isolated from larval epidermalA 29 kDa nuclear protein, isolated from larval epidermal
and fat body cells ofand fat body cells of Manduca sextaManduca sexta with high specificitywith high specificity
for binding with JH I and JH II.for binding with JH I and JH II.
 Another JH receptor purified from fat body cells of bothAnother JH receptor purified from fat body cells of both
adult sexes of cockroachadult sexes of cockroach Lecophaea manderaeLecophaea manderae (64 kDa(64 kDa
with two subunits, each with 32 kDa).with two subunits, each with 32 kDa).
 Last one related to the egg production in adult than toLast one related to the egg production in adult than to
the development of immature stages and detected in thethe development of immature stages and detected in the
last instar and adult (its structure is not known yet).last instar and adult (its structure is not known yet).

19. Mechanism of Action
 The series of successive moulting processes
subdivides the post – embryonic development in
insects into several intermoult periods, or instars,
during which growth and morphogenesis are
possible. This cyclical event repeated in each of
the instars, which are strictly inter – related, are
induced and controlled by the three
metamorphosis hormones; JH is one of them
[Novák, 1952].

20. Actions of Juvenile Hormones onActions of Juvenile Hormones on
Endocrine SystemsEndocrine Systems
 Larval Moult
 Larval – Pupal commitment
 Pupal Moult

21. Roles of JH in embryonic developmentRoles of JH in embryonic development
• JH is wiped out by JH esterases that appear with the onset of the
embryonic development and then it reappears late during
embryogenesis when it is secreted by the embryonic corpora allata.
• In Hemimetabola (as in Locust) presence of JH causes premature
termination of patterning, suppression of growth, precocious
differentiation of the nymphal stage.
• In Holometabola (in Lepidoptera) there is little effect on growth and
differentiation despite the effect of JH on blastokinesis.

22. Roles of JH in DiapauseRoles of JH in Diapause
 In insects, diapause is triggered by environmental
cues such as temperature, day length, humidity,
etc.
 In adult silkworms (Bombyx mori), diapause (halt
of reproduction) due to the cessation of secretion
of JH by corpora allata.
 In rice stem-borer (Chilo suppressalis) and South –
Western corn-borer (Diatraea grandiosella) JH
titer in haemolynph is high during diapause.

23. Molecular Actions of JuvenileMolecular Actions of Juvenile
HormonesHormones
 Existence of two alternative enzyme systems
(Wigglesworth, 1935).
 Stimulates succinate oxidation and that the site of
stimulation was that part of the respiratory chain
between succinate and cytochrome – c (Stegwee,
1960).

24. Molecular Actions of JuvenileMolecular Actions of Juvenile
HormonesHormones
 Coupling of DNA molecules with certain
isoprenoid compounds which include many of the
effective JH analogue.
 Controls gene expression at the translational level
(Ilan et, al, 1970).
 Drosophila USP (Ultraspiracle) protein binds to
JH III and JH III bisepoxide with low affinity.

25. Molecular Actions of JuvenileMolecular Actions of Juvenile
HormonesHormones
 Methoprene – tolerant (Met) gene in Drosophila
mutants is most interesting one that have an
intercellular JH – binding protein with reduced
JH – binding activity.
MET protein is found in the nucleus
and has a high degree of similarity to the basic helix-
loop – helix Per, Arnt and Sim (PAS) domain family
members.
 In actual, a JH receptor for insect development is
still elusive.

26. Larval Pupal Commitment

27. Regulation of Cuticular
Melanization
 Larval pigmentation is under the control of JH in
many insects, but there are not so many studies at
the molecular level.
 Manduca larvae have a transparent cuticle with
black markings. So, when JH is removed by
allatectomy about 30 hrs before the last larval
ecdysis, cuticular melanization ccurs in the newly
synthesized 5th
instar larval cuticle and can be
prevented by application of JH.

29. Applications of JHs and JHa(s)
¶ External application of only 1µg of methyl
farnesoate dichloride (one of the most active
JHa) to adult Pyrrhocoris females inhibited the
development and hatching of all the eggs laid.
¶ Performs important roles in caste differentiation
in both termites, ants and in honeybees.
¶ Discovery of two types of Entocones (JH and
MHd), lead the control of harmful insects.

30. Applications of JHs and JHa(s)
¶ Profound effect of JH on the viability of bug
Eurygaster integriceps (a serious grain pest in Eastern
Europe) [Teplakova, 1947].
¶ Topical application of JHa to last instar larvae of
Bombyx mori causes prolongation of the instar and an
approx. 20% increase in the weight of both the cocoon
and the pupa compared with the control [Chang et. al.,
1972].
¶ The greatest attention has been paid to JHa with
reference to their possible utilization as entirely new
types of insecticides.
Applications of JHs and JHa(s)Applications of JHs and JHa(s)

31. Applications of JHs and JHa(s)
¶ Wigglesworth (1973) compared the activity of three
samples of JH preparations in 5th
(last) instar nymphs of
Rhodnius prolixus.
> Natural (enantiomorphous – JH I) – causes 50%
inhibition of adult characters in a dose of about 15 µg,
> Synthetic (Racemic – JH IIa) – less active,
> Synthetic (C17 – JH i.e., JH IIb) – 2/3rds
that of the
natural JH I.
Applications of JHs and JHa(s)Applications of JHs and JHa(s)

32. Concluding Remarks
§ A morphogenetic hormone.
§ Has multiple functions and a primary role of JH in insect
development is to modulate ecdysone action.
§ Maintains the current commitment of the tissues and cells
whereas ecdysone causes both predifferentiative and
differentiative cellular events that are necessary for the
moult.
§ When JH is present, a moult to a larval stage ensures.
§ If JH is absent at the onset of the moult, morphogenesis
occurs.
§ Further studies and researches are still going on that can
elucidate new aspects of the action of this unique molecule.

33. AcknowledgementAcknowledgement
• Dr. Abhijit MazumdarDr. Abhijit Mazumdar, Reader, Department of Zoology, The University of Burdwan.
• Prof. Prasanta Kumar ChaudhuriProf. Prasanta Kumar Chaudhuri, Principal Investigator and Co – ordinator, AICOPTAX
Project, Ministry of Environment and Forests, Govt. of India.
• Dr. Niladri HazraDr. Niladri Hazra, Reader and Head, Department of Zoology, The University of Burdwan.
• All the Faculty MembersAll the Faculty Members, Department of Zoology, The University of Burdwan.
• Mr. Amitava NandiMr. Amitava Nandi, Librarian of the Department of Zoology, The University of Burdwan.
• Mrs. Sangita MitraMrs. Sangita Mitra, SRF Scholar, Mr. Asif Hossain and Miss Mou Nandi, Mr. Asif Hossain and Miss Mou Nandi, JRF Scholars of
the Entomology Research Unit, The University of Burdwan.
• Other ScholarsOther Scholars of Department of Zoology, The University of Burdwan.
• Non – teaching staffsNon – teaching staffs andand Technical AssistantTechnical Assistant of Department of Zoology, The University of
Burdwan.
• Dr. Manas MahapatraDr. Manas Mahapatra, Scientist and Director, Simultala Conservationist, an NGO working with
Wildlife Institute of India, Dehradun.
• Entire classmatesEntire classmates of Department of Zoology, The University of Burdwan.
• My husband, Mr. Chandra Kanta DeMy husband, Mr. Chandra Kanta De and my parents, parent – in lawsmy parents, parent – in laws and elder sisterelder sister.