Early Stages of
Development


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Developmental Biology Laboratory Observations of the Zebrafish Embryo


Zygote Period (0-.75h)

0_2h.gif (33832 bytes)

0_75h.gif (30893 bytes)
1-cell
(0.2 h)		 2-cell
(0.75 h)

Cytoplasm streams toward animal pole to form the blastodisc


Cleavage Period (0.75-2.2 h)

01_0h.gif (28741 bytes)

01_25h.gif (20243 bytes)

01_5h.gif (28692 bytes)

01_75h.gif (17717 bytes)

02_0h.gif (121783 bytes)
4-cell
(1 h)		 8-cell
(1.25 h)		 16-cell
(1.5 h)		 32-cell
(1.75 h)		 64-cell
(2 h)

During this period, the first 6 cleavages occur. The cells, or blastomeres, divide synchronously at about 15 minute intervals.

 

Blastula Period (2.25-5.25 h)

02_25h.gif (181416 bytes)

02_5h.gif (131503 bytes)

02_75h.gif (140058 bytes)

03_0h.gif (150248 bytes)

03_3h.gif (156480 bytes)
128-cell
(2.25 h)		 256-cell
(2.5 h)		 512-cell
(2.75 h)		 1k-cell
(3 h)		 high
(3.3 h)
 

03_7h.gif (61668 bytes)

04_0h.gif (94238 bytes)

04_3h.gif (82644 bytes)

04_7h.gif (97384 bytes)

 05_3h.gif (47257 bytes)
oblong
(3.7 h)		 sphere
(4 h)		 dome
(4.3 h)		 30%-epiboly (4.7 h) 50% epiboly
(5.3 h)

Midblastula transition occurs at the 10th cleavage. At this division, cell membranes do not form between cells of the bottom, marginal, row of blastomeres, and thereafter, it develops into the "yolk syncytial layer (YSL)" of the yolk cell. After midblastula, transition cell divisions are asynchronous. Margin reaches 30% epiboly.

 

 

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