高清彩图显示爪蟾（Xenopus laevis）早期发育时期示意图（stage 1–stage 40），基于 Nieuwkoop & Faber 分期标准（NF 分期）。图中依次展示了从受精卵到游泳蝌蚪的各关键发育时期的形态特征，是实验室鉴定胚胎发育进程的重要参照。High-resolution colour chart of Xenopus laevis early developmental stages (stage 1–40) based on the Nieuwkoop & Faber (NF) staging table. The chart depicts the morphological features of each key stage from fertilised egg to free-swimming tadpole and serves as the primary laboratory reference for staging embryos.
NF 分期概要NF staging overview
| NF 期NF stage | 发育阶段Developmental stage | 时间（25 ℃）Time at 25 ℃ | 主要特征Key features |
|---|---|---|---|
| 1–8 | 受精卵 → 卵裂Fertilised egg → cleavage | 0–8 h | 第一、二次卵裂，8 细胞1st–2nd cleavage, 8-cell stage |
| 8–9 | 囊胚Blastula | 8–10 h | 囊腔形成，细胞数 ~1000Blastocoel forms, ~1000 cells |
| 10–12 | 原肠胚Gastrula | 10–14 h | 背唇（Spemann 组织者）出现，三胚层建立Dorsal lip (Spemann organizer) appears; three germ layers established |
| 13–20 | 神经胚Neurula | 14–22 h | 神经板、神经管闭合Neural plate forms, neural tube closes |
| 21–35 | 尾芽胚 → 游泳蝌蚪Tailbud → swimming tadpole | 1–3 d | 心跳、色素、尾芽伸展Heartbeat, pigmentation, tail extension |
| 36–40 | 自由游泳蝌蚪Free-swimming tadpole | 3–5 d | 消化道形成，开始摄食Gut forms, feeding begins |
发育速度随温度显著变化：18–22 ℃ 较慢，25–27 ℃ 较快。实际分期须以形态为准，不能仅依据时间。Development rate varies significantly with temperature: slower at 18–22 ℃, faster at 25–27 ℃. Always stage by morphology, not time alone.
分期在实验中的应用Applications of staging
- 显微注射时机：多选用 NF 1–2 期（单细胞或双细胞）进行 mRNA / Morpholino 注射，靶向胚胎全身；NF 8 期（8 细胞）可定向注射特定卵裂球，实现区域性标记。Injection timing: NF 1–2 (1- or 2-cell) for whole-embryo mRNA/Morpholino delivery; NF 8 (8-cell) for blastomere-targeted regional labelling.
- 组织移植实验：NF 10.5 背唇是 Spemann 组织者实验的经典取材时期。Graft experiments: NF 10.5 dorsal lip is the classical stage for Spemann organizer assays.
- 基因表达分析：ISH 和 IHC 通常覆盖 NF 10–40 各关键时间点，绘制基因时空表达图谱。Gene expression analysis: ISH and IHC typically span NF 10–40 key time points for spatiotemporal expression mapping.
- 药物处理：将胚胎置于含目标化合物的盐溶液中，精确控制起始和终止发育时期。Drug treatment: expose embryos to compounds in saline solution with precise control of treatment window.
参考文献References
- Nieuwkoop PD, Faber J (1994) Normal Table of Xenopus laevis (Daudin), 2nd edn. Garland Publishing, New York. (Originally published 1956, North Holland Publishing Co., Amsterdam.)
- Harland R & Gerhart J (1997) Formation and function of Spemann's organizer. Annu Rev Cell Dev Biol 13:611–667.
- Sive HL, Grainger RM, Harland RM (2000) Early Development of Xenopus laevis: A Laboratory Manual. Cold Spring Harbor Laboratory Press.