Embryogenesis in silkworms
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Embryogenesis ? ?
Developmental process that usually begins once the egg has been fertilized.
Why? To identify suitable stages for refrigeration.To know about initiation, continuation &
termination of diapause.Device strategies for long term cold storage.To identify when diapause terminates.
EMBRYOGENESIS
Fertilization
Sperm nucleus + egg nucleus (syngamy) = diploid zygote
( EMBRYO) – 2 hr@ 250 C
Cleavage
Nucleus divides mitotically to form many which lie in polar plasm
( meroblastic).
Germ band formation (24 hr)
Blastoderm cells in the ventral side of egg divides & collect to form lamelliform structure called ventral plate
Ventral plate further thickens to form germ band which later sink inside the egg – Daruma stage.
A membraneous layer forms two folds around the germ band called serosa (entire surface) & amnion
( ventral surface)
ORGANOGENESIS
Otsu –A stage:It is swelling of cephalic lobe
Otsu –B stage:It is distinct depression stage.
Hei - A stage: body becomes long & slendercephalic lobe is distinct1st 4 segments form head, next 3 segments form abdomen & last 11 segments form thorax
Hei - B stage:Development of cephalic embryo upto 80%
Period of shortening & organ formation
Embryo expands in girth & shortens , segmental
appendages develops distinctly.
Ectoderm forms fore gut & hind gut , endoderm forms
midgut.
Alimantary canal, head, thoracic legs , abdominal appendages are formed.
Eye spot stage (8th day)
Bristles grow around body surface
Dark pigmentation around mouth & head which can be
seen through egg shell as blue spot
Head pigmentation
Blastokinensis
It is an active movement of embryo from the ventral to the dorsal side of the egg and at the same time revolves
1800 on its long axis
Reference
Comprehensive sericulture - G .Ganga Introduction to sericulture - S.Ganga & J.Sulochana Chettyhttp://www.seriinfo.@10% html.http://www.seriuniv.comhttp://www.seriagro@20%.html