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1. Moulting in arthropods and
insects
By
a.m.manoj
13-503-006

2. A RECAP ON STRUCTURE AND
FUNCTION OF CUTICLE

3. NEED OF MOULTING
• Growth is limited by the cuticle which only
undergoes a limited amount of stretching so
that for any marked increase in size to occur
the cuticle must be shed and replaced
• Casting the cuticle is commonly known as
moulting

4. MOULTING
Definition
Periodical shedding or casting of old cuticle
and developing and hardening of new
cuticle.

5. Two main process in moulting
• It mainly involve two distinct process which may be
widely seperated in time so that it is convinient to
distinguish between them
The two main process are
1. Apolysisseperation of old cuticle
2. Ecdysissheddding of remmanants of the old
cuticle (insects,chapman r.F)

6. STEPS INVOLVED IN MOULTING
PROCESS
1. Apolysis
2. Secreation of inactive moulting fluid by epidermis
3. Production of cuticulin layer of new exoskeleton
4. Activation of moulting fluid
5. Digestion and absorption of old endocuticle
6. Epidermis secretes inner epicuticle and new procuticle
7. Ecdysis
8. Expansion of new integument
9. Tanning

7. CHANGE IN EPIDERMIS
The onset of moulting is indicated first by
changes in the epidermal cells which divide
mitotically and become coloumnar in form
When they are flattened the over all area of
the epidermis
Hence the cuticle size is increased

8. SEPERATION OF OLD CUTICLE FROM
THE EPIDERMIS
• As a result of changes in cell shape, a tension
is generated at the surface of the epidermal
cell which result in their seperating from the
cuticle

9. DIGESTION OF OLD ENDOCUTICLE
• As the cuticle separate from the epidermis moulting
fluid is secreted into the space
• It is followed by the secretion of moulting fluid
• But it precedes it activation (moulting fluid at the
initial will be in inactive stage)
• As a result of activity of mouling fluid line of
weakness appears in the ecdysial line

10. ROLE OF MOULTING FLUID
• The moulting fluid contain the enzyme proeinase and
chitinase
• But at first level of secreation the moulting fluid will
be in inactive stage
If cuticulin doesn’t preced mooulting liquid what
happens
?

11. ECDYSIS
• Usually ecdysis follows as soon as digestion is
complete
• As a process of seperating the old cuticle
which consist of epicuticle and exocuticle
from the new cuticle
• In sometime the old cuticle may retain for a
time and the insect reffered to as pharate
instar

12. DURING ECDYSIS
• The pore canal within the procuicle allow the
movement of lipids and proteins towards the new
epicuticle where the wax layer and cement layer form
• Wax layer (reason why wax is advanced in ecdysis)
• Forms shortly before ecdysis wax is seperated on to
the surface of the new cuticle and the layer adjacent
to the cuticulin forms oriented monolayer

13. AFTER ECDYSIS
• Soon after ecdysis the layer formed is the
cement layer
A animated tour to moulting

14. Mechanism
• Te insects swallows air or water which swells
the gut
• So that the haemolymph pressure is
increased
• There will be muscle contracion
• By prestaic body movement the old
exocuticle or exuvium is moved posteriorly
with the remaining moulting fluid
• Which will act as lubricant

15. TANNING
• The wrinkled new integument is expanded by streching
• Differentation of procuticle into exocuticle and epicuticle
take place(after ecdysis) by sclerotization of exocuticle alone
• After hardening muscle relax ,and air is exhaled ,blood
pressure reduce and the space is now available for further
protoplasmic synthesis
• Until the process of tanning is complete it is called as in
teneral condition

17. TERMS USED IN INSECT DURING
MOULTING STAGES
• Instar  insect growth occurs through a
series of immature stage is called instar
• Time interval between two subsequent
moulting is called stadium

18. DURING ONSET OF MOULTING IN
INSECT
• Moulting begins when the brain receives stimuli from the
body and environment
• The immature stage of insect stops feeding
and become inactive before moulting.
• Each active stage in the insects life is
followed by a sluggish pre-moluting period.

19. Some change
• It is not necessary that all insect moult oly
during larval stage
Mayflies (Pterygote insect) and all Apterygote
insects (except Dipulrans ) moults during
adult stage.

20. In arthropods

21. MOULTING PROCESS
It involve 5 steps
1. Premoult
2. Moult
3. Inflation
4. Postmoult intermoult

22. PRE MOULT
• A new cuticle is secreated below the old
cuticle
epicuticle
procuticle
epicuticle
procuticle
initial state
early premoult –
separation of
epithelia from
epi-,procuticle
epithelium
epithelium

23. DIGESTION OF OLD MATERIAL AND NEW
FORMATION
epicuticle
procuticle
epithelium
early premoult –
separation of
epithelia from
epi-,procuticle
epithelium
old epicuticle
old procuticle
new epicuticle
new procuticle
late premoult –
digestion of old
matl. formation
of new.

24. INFLATION – rapid increase in size by inhaling
water or air pushing out the new cuticle.
POSTMOULT : hardening of the skeleton by
tanning, sclerotization.
INTERMOULT: tissue grows to fill in new
cuticle.

25. A show on
moulting