Figure No. Developmental stage Time of appearance (h) Characters
1a Fertilization 00:00 Round, transparent and adhesive in nature
1b Blastodisc 00:21±00:01 An out growth over the vitelline sphere developed at animal pole
1c Two cell 00:49±00:02 First cleavage, where two cells over the yolk sphere was clearly visible.
1d Four cell 01:07±00:04 Second cleavage, where blastomeres were clearly visible and counted.
1e Eight cell 01:30±00:06 Third cleavage, where little overlapping of blastomeres was observed.
1f Sixteen cell 01:51±00:08 Fourth cleavage, where overlapping of blastomeres was observed and were placed in two rows.
1g Thirty two cell 02:04±00:10 Fifth cleavage where the blastomeres were visible in 2-3 layers.
1h Sixty four cell 02:32±00:20 Sixth cleavage, where overlapping of blastomeres was observed and were placed in 2-3 layers.
1i Morula 03:43±00:33 Blastodermal cells were very small due to repeated division and gave a flowery look at the animal pole.
1j Blastula 05:12±01:08 Difficult to recognize the blastomers. The blastoderm was compressed and occupied more than half area over the yolk sphere.
1k Gastrula 07:27±01:16 Thick layer of blastoderm or germinal ring occupied 3/4th area over the yolk sphere. One end of it was observed broad, which became the future cephalic part of the embryo.
1l “C” shape embryo 09:29±01:24 Embryo looked kidney shape over the yolk sphere with clear distinction of head and tail.
  Twitching 21:30±01:10 Tail became free from yolk sphere and beat in quick succession to rupture the egg membrane.
1m Hatching 25:27±01:28 The larvae were transparent with straight body and having free swimming capability.
Time shown in the table for each developmental stage is the average value of two observations (Mean ± SD). Time is expressed as h:min ± h:min
Table 1: Different events of embryonic development of fertilized egg and their respective Time in P. pangasius.