Developmental stage | Elapsed time | Remark | Features of eggs and embryos |
Fertilized egg | 0.0 | Fig. 1A | Spherical & transparent with buoyancy |
1 cell | 40 min | Fig. 1B | |
2-cell | 1 h 12 min | Fig. 1C | First cleavage |
4-cell | 1 h 46 min | Fig. 1D | Second cleavage, plane perpendicular to the first |
8-cell | 2 hrs 25 min | Fig. 1E | Third cleavage, plane perpendicular to the second |
16-cell | 2 hrs 52 min | Fig. 1F | |
32-cell | 3 hrs 48 min | Fig. 1G | |
64-cell | 4 hrs 04 min | Fig. 1H | |
Morula | 6 hrs 06 min | Fig. 1I | |
Blastula | 10 hrs 25 min | Fig. 1J | Start of blastula stage |
Early gastrula | 14 hrs 20 min | Fig. 1K | Blastoderm expanded towards the vegetal pole to cover the yolk |
Late gastrula | 21 hrs 21 min | Fig. 1L | Blastoderm had covered most of the yolk |
Formation of embryo | 22 hrs 20 min | Fig. 1M | Outline of the embryo became clearly visible |
Kupffer’s vesicles | 24 hrs 02 min | Fig. 1N | 10 to 11 myotomes were visible |
Auditory vesicles and eye lens | 27 hrs 53 min | Fig. 1O | 13 myotomes were visible |
Melanophores appearance | 31 hrs 22 min | Fig. 1P | 18 to 19 myotomes, melanophores appeared on the embryo |
Melanophores appearance | 34 hrs 06 min | Fig. 1Q | Melanophores appeared on the yolk |
Heart beat | 54 hrs 43 min | Fig. 1R | 28 to 30 myotomes, embryonic movements |
Hatching | 67 hrs | Fig. 1S | Hatching begins |