Table 1. The emerging time of embryonic structures in Taiwan Country Chicken (TCC) and Brown Tsaiya Ducks (BTD) during the first 72 h of incubation in comparison with the HH* staging system.
| Hour post-incubation | |||
|---|---|---|---|
| Embryonic structures | HH* | TCC | BTD |
| Two-layered blastoderm (HH1; D13) ** | 0–5 | 0–5 | 1–12 |
| Primitive streak (HH2; D14) | 6–7 | 6–7 | 10–13 |
| Intermediate primitive streak (HH3; D15) | 12–13 | 12–13 | 19–24 |
| Full-length primitive streak (HH4; D16) | 18–19 | 18–19 | 25–27 |
| Regressing primitive streak | N/A | 23–39 | 28–42 |
| Headfold formation (HH6; D19) | 23–25 | 22–25 | 31–36 |
| First somite pair (HH7; D20) | 23–26 | 24–26 | 32–34 |
| Neural fold (HH7; D21) | 23–26 | 24–26 | 32–34 |
| Primary optic vesicles (HH9; D22) | 29–33 | 27–32 | 36–42 |
| Paired heart primordia (HH9; D22) | 29–33 | 26–32 | 36–42 |
| Nervous system | |||
| Three primary brains (HH10; D23) | 33–38 | 33–39 | 43–46 |
| Five neuromeres (HH11; D24) | 40–45 | 40–45 | 46–52 |
| Limb primordia; wing and leg buds (HH17; D30) | 51–64 | 51–64 | 64–72 |
| Allantois (HH19; D32) | 65–72 | 68–72 | N/A |
*Hamburger-Hamilton staging system
** The embryonic structures refer to the stages from Hamburger and Hamilton (1915) and Dupuy et al. (2002), designated as D-staging or D.
N/A: data not available.