Embryonic stages are modified from Kimmel et al., 1995. Developmental Dynamics 203:253-310. Copyright ©1995 Wiley-Liss, Inc. Reprinted only by permission of Wiley-Liss, a subsidiary of John Wiley & Sons, Inc.
Select a stage name below to get a detailed description and images. You can also browse the zebrafish Anatomical Ontology (AO) to show anatomical terms that are present at that stage.
(h = hours of development at 28.5°C)
| Period | Stage | Begins | Developmental Landmarks | Anatomy |
| Zygote (0 - 0.75 h) | 1-cell | 0.00 h | Cytoplasm streams toward animal pole to form blastodisc | Browse AO |
| Cleavage (0.75 - 2.25 h) |
2-cell | 0.75 h | Partial cleavage | Browse AO |
| 4-cell | 1.00 h | 2 X 2 array of blastomeres | Browse AO | |
| 8-cell | 1.25 h | 2 X 4 array of blastomeres | Browse AO | |
| 16-cell | 1.50 h | 4 X 4 array of blastomeres | Browse AO | |
| 32-cell | 1.75 h | 4 X 8 array of blastomeres | Browse AO | |
| 64-cell | 2.00 h | 3 regular tiers of blastomeres | Browse AO | |
| Blastula (2.25 - 5.25 h) |
128-cell | 2.25 h | 5 blastomere tiers; cleavage planes irregular | Browse AO |
| 256-cell | 2.50 h | 7 blastomere tiers | Browse AO | |
| 512-cell | 2.75 h | 9 blastomere tiers; YSL forms | Browse AO | |
| 1k-cell | 3.00 h | 11 blastomere tiers; single row of YSL nuclei; asynchronous cell cycle | Browse AO | |
| High | 3.33 h | > 11 blastomere tiers; blastodisc flattening begins; YSL nuclei in two rows | Browse AO | |
| Oblong | 3.66 h | Blastodisc flattening; multiple rows of YSL nuclei | Browse AO | |
| Sphere | 4.00 h | Spherical shape; flat border between blastodisc and yolk | Browse AO | |
| Dome | 4.33 h | Yolk cell bulging toward animal pole as epiboly begins | Browse AO | |
| 30%-epiboly | 4.66 h | Blastoderm an inverted cup of uniform thickness | Browse AO | |
| Gastrula (5.25 - 10.33 h) |
50%-epiboly | 5.25 h | Blastoderm remains of uniform thickness | Browse AO |
| Germ-ring | 5.66 h | Germ ring visible from animal pole; 50%-epiboly | Browse AO | |
| Shield | 6.00 h | Embryonic shield visible from animal pole; 50%-epiboly | Browse AO | |
| 75%-epiboly | 8.00 h | Dorsal side distinctly thicker; epiblast, hypoblast, evacuation zone visible | Browse AO | |
| 90%-epiboly | 9.00 h | Axis and neural plate; brain and notochord rudiments | Browse AO | |
| Bud | 10.00 h | Tail bud prominent; early polster; 100%-epiboly | Browse AO | |
| Segmentation (10.33 - 24 h) |
1-4 somites | 10.33 h | First somite furrow | Browse AO |
| 5-9 somites | 11.66 h | Polster prominent; optic vesicle, Kupffer's vesicle, neural keel | Browse AO | |
| 10-13 somites | 14 h | Pronephros forms | Browse AO | |
| 14-19 somites | 16 h | EL (embryo length) = 0.9 mm; otic placode, brain neuromeres | Browse AO | |
| 20-25 somites | 19 h | EL = 1.4 mm; lens, otic vesicle, hindbrain neuromeres | Browse AO | |
| 26+ somites | 22 h | EL = 1.6 mm; blood islands, otoliths, midbrain-hindbrain boundary | Browse AO | |
| Pharyngula (24 - 48 h) |
Prim-5 | 24 h | EL = 1.9 mm; early pigmentation, heartbeat | Browse AO |
| Prim-15 | 30 h | EL = 2.5 mm; early touch reflex, retina pigmented | Browse AO | |
| Prim-25 | 36 h | EL = 2.7 mm; early motility, tail pigmentation | Browse AO | |
| High-pec | 42 h | EL = 2.9 mm; rudiments of pectoral fins | Browse AO | |
| Hatching (48 - 72 h) |
Long-pec | 48 h | EL = 3.1 mm; elongated pectoral fin buds | Browse AO |
| Pec-fin | 60 h | EL = 3.3 mm; pectoral fin blades | Browse AO | |
| Larval | Protruding-mouth | 72 h | 3.5 mm total body length | Browse AO |
| Day 4 | 96 h | 3.7 mm total body length | Browse AO | |
| Day 5 | 120 h | 3.9 mm total body length; 6 teeth | Browse AO | |
| Day 6 | 144 h | 4.2 mm total body length | Browse AO | |
| Days 7-13 | 168 h | 4.5 mm total body length; 8 teeth | Browse AO | |
| Days 14-20 | 14 d | 6.2 mm total body length; 10 teeth | Browse AO | |
| Days 21-29 | 21 d | 7.8 mm total body length | Browse AO | |
| Juvenile | Days 30-44 | 30 d | 10 mm total body length; adult fins/pigment | Browse AO |
| Days 45-89 | 45 d | 14 mm total body length; 12 teeth | Browse AO | |
| Adult (90 d - 2 y) | 90 d | Breeding adult | Browse AO | |
| Unknown | Stage yet to be determined. | |||