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3.8. Major carp egg and embryonic developmental stages
Unit 3 - Breeding of major carps
3.8. Major carp egg and embryonic developmental stages
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The fertilization of major carp eggs is external.
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The fertilized eggs absorb water and swell considerably in 10-15 minutes and they becomes a little hard and this process is known as water hardening.
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They are bead-like, non-adhesive, semi-buoyant and have a large perivitelline space.
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The size of the eggs varies between 2.5 and 6.5 mm.
Important major carp egg and embryonic stages and time required for each stage are as follows
Sl. no. |
Time required at 24-310C (Cumulative) |
Stage |
1 |
0 min |
Fertilization |
2 |
10-15 min |
Water hardening and blastodisc formation |
3 |
30-50 min |
First cleavage (2 cells) |
4 |
40-65 min |
Second cleavage (4 cells) |
5 |
50-80 min |
Third cleavage (8 cells) |
6 |
60-90 min |
Fourth cleavage (16 cells) |
7 |
70-120 min |
Fifth cleavage (32 cells) |
8 |
2-2½ hrs |
Morula stage – less than half of yolk invaded by germ layer |
9 |
2½-3 hrs |
Blastula – about half of yolk invaded by germ layer |
10 |
3-3½ hrs |
Gastrula – about three-fourth of yolk is invaded by germ layer |
11 |
3-4 hrs |
Yolk-plug stage – complete invasion of yolk by germ layer excepting a small pore (blastopore) |
12 |
4-6 hrs |
Elongation of yolk mass-embryonic stage starts |
13 |
5-6 hrs |
Pea-shaped embryo – somites and myotomes appear |
14 |
8-10 hrs |
Comma-shaped embryo- optic vesicles appear, occasional twitching movement starts, gill rudiments and pectoral fin bud appear, heart appear |
15 |
14-15 hrs |
Advanced embryo – increase in the number of somites and myotomes, twitching movement quite rapid |
16 |
18-20 hrs |
Hatching – it takes place over a period of 2-3 hrs at 24-310C |