SILKWORM : Acid Treatment of silkworm eggs

2. •Temperate Breeds Are Either Univoltine/ Bivoltine. They Lay Both Hibernating And
Non Hibernating Eggs.
•Tropical Breeds Are All Multivoltines. They Lay Only Non Hibernating Eggs.
Depending Upon Diapause character Silkworm eggs are-
•HIBERNATING EGGS •NON- HIBERNATING EGGS
UNIVOLTINE
BIVOLTINE
MULTIVOLTINE
Ex- All European Breeds.
Ex- NB4D2, NB18, KA, NB7.
Ex- Pure Mysore, C.nichi, Hosa Mysore, Raj

3. ACID TREATMENT OF SILKWORM EGGS
•Inorganic acids are preferred over organic acids
•Inorganic acids such as- HNO3, H2SO4 , Aqua regia.

4. APPLIANCES USED IN ACID TREATMENT

5. HCl TREATMENT
There are pure and industrial/commercial variety of HCl.
PURE HCl
• Colourless
• At 15˚C contain 42% of HCl.
• Specific gravity is 1.212
COMMERCIAL HCl
• Light brown/yellow
• At 15˚C contain 30% of HCl.
• Specific gravity is 1.180
The commercial grade HCI is generally available in a range of 1.150 to
1.180 specific gravity.
•Preparation of HCl

6. CORRECT AGE OF SILKWORM FOR ACID TREATMENT
•20 and 24 hrs after ovipositon.
•Eggs are kept at 25˚C and RH (75+5)%.
•Freshly laid eggs are pale or dark yellow.
•Initiation of diapause is represented by acquiring brown colour due to
Ommochrome pigment in serosal cells.
SPECIFIC GRAVITY DEPENDS UPON-
•Concentration of HCl
•Temperature

7. FORMALIN TREATMENT
•Eggs Are Soaked In 2% Formalin Solution For 15 Min
•Followed By Washing To Remove Formalin Traces
•Helps In Fixation And Surface Sterilization

8. HOT ACID TREATMENT
•Specific Gravity Of HCl- 1.075 Recorded At 15˚C.
•Concentration Of HCl- 15%.
•Temperature Of HCl- 46 ˚C.
•Immersion Time- 4-7 Minutes. Dipping Duration Varies With Races.
After dipping, eggs are washed in water at temperature 15-30˚C for 15-20 min.
Washing is followed by drying
ADVANTAGES
• Large quantity of eggs be treated in
short time
• Quantity of conc. Acid is less.
• Doesn’t effect non diapausing eggs.
DISADVANTAGES
• Not suitable for younger eggs
• Precision is required
• Unfertilized egg do not get
crumbled.

9. COLD ACID TREATMENT
•Also known as room temperature acid treatment.
•Specific gravity is 1.10 at 15˚C
•Concentration of HCl is 20%.
•Immersion time is 40-90 min depending upon temperature
•Temperature varies from 23-30 ˚C
ADVANTAGES
• Safe and reliable
• Suitable for eggs of younger age
• Unfertilized eggs get crumbled
DISADVANTAGES
• Requires large amount of acid
• Silkworm with low potency of
hibernation are not treated as it get
crumbled
• Quality of egg card should be good

10. TREATMENT OF LOOSE EGGS
•Easier in both hot acid and cold acid treatment
•Huge quantity of eggs can be treated (4000-6000dfls)
•Eggs are kept in a perforated container with a central rod
•Altogether dipped in the acid container and rotated
WASHING OF EGGS
•After immersion eggs are subjected to washing at 15-30˚C for
15-20 mins.
•presence of acid is tested
•After washing eggs are subjected to drying at temperature
of24-26 ˚C.

11. POSTPONEMENT OF ACID TREATMENT
•Eggs are kept at 5˚C for 5 days to 7 days at 2.5 ˚C
•Optimum age is 16-22 hrs after oviposition.
•Eggs are passed at intermediate of 15˚C for 2hr before it
•After release they are passed at 15 ˚C and 25 ˚C before subjecting to acid
treatment
Cold storage of acid treated eggs
•To adjust hatching date
•Acid treated diapause eggs are referred as artificial non diapause eggs
•Stored at 5 ˚C at maximum duration 3 weeks

12. ACID TREATMENT AFTER CHILLING
•Eggs exposed at temperature of 5˚c or 2.5 ˚C, artificial overwintering for 90
days
•Short term chilling- eggs preserved at 25 ˚C for 30-35 hrs then chilled at 5 ˚C
for 30-40 days
•Long term chilling- 40-45 hrs old eggs chilled at 5 ˚C for 35-50 days
•Then followed by acid treatment within 6 hrs.
•Cold storing or releasing, the eggs should be kept at 15˚C for about 3hrs
•Prior to acid treatment eggs are later kept at 25 ˚C.
•HCl of specific gravity=1.10 at 15 ˚C
•Concentration 20% treated at temperature 47.8 ˚C with similar dipping
duration of races in hot acid treatment
ACID TREATMENT

13. PRECAUTIONS DURING ACID TREATMENT
Quality of the acid
Re-use of acid
Temperature of the acid
Dipping duration
Co-ordination
Maintenance of acid
temperature
Test hatching
Washing after acid treatment
Colour of eggs
Use of protective materials

14. •Oxygen consumption
•Carbohydrate metabolism
•Changes in amino acid
•Pigment formation
•Esterase A activity

15. conclusion
•Voltinism and diapause
•Artificial methods to break diapause
•Acid treatment its advantages and
disadvantages
•Metabolism associated with initiation and
termination of diapause

16. REFERENCES
BOOKS
•Ganga and Sulochana(2020 ). An introduction to Sericulture(Eds).Oxford and
IBH Publishing Co Pvt. Ltd.
•N.M. Biram Saheb, Dr. K. Sengupta and Dr G.V.Reddy(1990) A Treatise on the
Acid Treatment of Silkworm Eggs.(Eds) Central Silk Board - Government of India
Tribhuwan Singh, Pramod Kumar Singh and Khursheed Ahmad Sahaf(2013). Egg
Diapause and Metabolic Modulations during Embryonic Development in the
Silkworm, Bombyx mori L. (Lepidoptera: Bombycidae). Annals of Biological
Research, 4(1), 12-21.
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