2. • The univoltine silkworms lays only hibernating
eggs, while bivoltine lay one brood of diapausing
and one non-diapausing egg. These eggs will not
hatch till the following spring until artificial
methods are adapted for hatching
• The most common method of artificial hatching
is acid treatment
• Such acid treated eggs are termed as artificial
non-diapause eggs.
5. Preparation of hydrochloric acid
• The required quantity of Hcl of required specific
gravity is derived with formula:
• Quantity of acid solution required
= (desired sp. gr-1.000)x volume of acid (ml)
(original sp. gr-1.000)
6. • There are two methods of acid treatment
• They are
(1) Hot Acid Treatment
(2) Cold Acid Treatment.
7. Hot acid treatment :
• It is performed while the acid is hot.
• It is conducted with HCl of specific gravity
1.075 (recorded at 15°C) with 15%
concentration and heated to 46°C with a
dipping duration ranging between 4 and 7
minutes.
8. Acid treatment schedule for popular
bivoltine races of South India
Name of the breed Type Optimum range of
dipping duration
(in minutes)
KA Chinese 4-5
NB7 Chinese 4-5
NN6D Chinese 4-5
CC1 Chinese 4-5
CA2 Chinese 4-5
NB4D2 Japanese 5-6
NB18 Japanese 5-6
PCN Yellow bivoltline 4-5
15. Precautions
• Dipping duration of a particular breed, specific gravity and
temperature is accurately maintained
• Prior to the slipping of the egg cards into the container, the
heated acid should be thoroughly mixed
• The egg cards/loose eggs are frequently moved to enable
uniform and proper exposure of the eggs to acid
• Immediately after the treatment, the egg cards/loose eggs are
thoroughly washed in running water
• The treatment is done only when the eggs have minimum of 20
hours development
16. Advantages
• Immersion period being less (only 4 - 7 min)
• A large quantity of eggs can be treated in a shorter
period
• This treatment does not affect the non-diapausing eggs
• Quantity of concentrated acid required is relatively less.
• It controls pebrine disease
17. Disadvantages
• It is not suitable for younger age eggs.
• Demands additional infrastructural facilities for heating
of the acid.
• Time of treatment being very short, one has to be quite
alert and conduct the treatment with utmost precision
and care.
• Continuous emanation of acid fumes may affect the
health of the technicians and corrode equipments and
fixers of the chamber.
18. Cold acid treatment
• This is commonly referred to as room temperature acid
treatment method (23°C to 30°C) as the treatment is
performed at room temperature.
• The specific gravity of HCl required is 1.10 with 20%
concentration. The soaking time ranges between 40 to
90 minutes depending upon the prevailing acid
temperature.
• The treatment is conducted when the eggs have
accomplished atleast 15 hours of development.
21. Advantages :
• It is even suitable for eggs of younger age.
• Silkworm breeds relatively weak or sensitive to hot
acid can easily be handled.
• No heating of acid is involved and hence additional
equipments and electricity are also not required.
• In loose eggs treatment, unfertilized eggs crumble and
facilitate comfortable separation.
• Quantity of fumes emanated is significantly less
compared to hot acid treatment method
22. Disadvantages :
• Needs sufficiently large quantities of concentrated
acid.
• Non-diapausing eggs do not withstand cold acid
treatment and get damaged, Hence silkworm breeds
with low potency of hibernation cannot be handled in
cold acid treatment.
• The quality of the egg card should be good enough to
withstand longer duration of dipping and subsequent
washing in water.
23. Acid treatment after chilling
• ln silkworm eggs, diapause termination is achieved by exposing
the eggs to low temperature
• Such chilled eggs give good and uniform hatching.
• Short term chilling:
The eggs preserved at high temperature (25°C) for 30-35
hours and chilled at 5°C for 30-40 days
• Long term chilling:
40-50hours old eggs chilled for35-50days are subjected to this
acid treatment.
24. Precautions :
1. While shifting the eggs from high temperature (25°C) to low
temperature (5°C) or vice-versa, they have to be essentially
passed through an intermediate temperature of 15°C for about
3 hours to avoid shock.
2. The eggs released from 5°C have to be acid treated within six
hours. This is so because the serosal pigment starts spreading
uniformly in the sersoal cells. Once the spread of the pigment is
complete, the impact of acid treatment gets nullified.
3. Acid treatment should not be performed immediately after
release from 5°C as it would give shock to the embryos and may
result in white rot eggs (dead eggs).
25. comparative requirements of
different types of acid treatment
characters Common hot acid
treatment
Common cold
acid treatment
Acid treatment for
chilled eggs
Specific gravity of
HCl
1.075 1.10 1.10
Concentration of
HCl
15% 20% 20%
Temperature of HCl
during treatment
46°C 25°C /26°C
/29°C
47.8°C
Age of the egg 20-24 hrs 20-24 hrs 30-35 hrs old egg
chilled for 30-40
days
40 -50 hrs old egg
chilled for 35-50
days
26. How the acid acts in blocking diapause. Some of the theories are as
under :
• 1. Miura (1929) first reported that activation and hatching of eggs
by HCl is due to the electron charge of the chloride ion and
concluded that the hatching possibility or impossibility of the eggs
depends upon the eggs' ability to absorb negative ions.
• 2. Okada (1971) and Sonobe (1979) reported that soaking of 20
to 24 hours old eggs in HCl solution enhances oxygen
permeability of the chorion which prevents the occurrence of
diapause.
• 3. HCI treatment increases the rate of water loss abruptly,
suggesting the prevention of diapause. (Sonobe,1979).
• 4. HCI permeated through the egg shells during the course of
treatment brings about a decline in pH values of egg contents
(Yoshimi et al 1986)
