鳥類可以依照雛鳥型態與育雛行為的不同分為早熟鳥（例：雞與鴨）與晚熟鳥（例：雀鳥與鸚鵡）。其中最明顯的特徵即為雛鳥絨毛的發育的不同，早熟鳥幼鳥全身被絨羽覆蓋，晚熟鳥雛鳥則皮膚裸露。依照親源關係分析與化石證據推斷，早熟鳥是較接近祖先的型態。先前的研究發現，錦花雀（Taeniopygia guttata）的雛絨毛是透過成纖維細胞生長因子訊號路徑(FGF signaling pathway)所抑制。本研究使用另一種晚熟鳥，虎皮鸚鵡（Melopsittacus undulates），來探索其他晚熟鳥是否也用同樣的機制來抑制絨羽的發育。此外我們也發現鴨子（Anas platyrhynchos domestica）毛囊生成的過程與雞和其他馴化鳥類不同，顯示出在早熟鳥中，雛絨毛發育的情形也具有多樣性。我們應用原位雜合實驗和特定股RNA定序來觀察候選基因的表現情形，並與先前的研究比較。我們的結果顯示，鸚鵡和雀鳥可能都使用相似的抑制路徑來抑制絨羽生成。我們的結果也顯示在鴨子的絨羽發育過程中，有反股的音蝟因子（Sonic hedgehog，SHH）扮演著抑制的角色。這項研究提供了對於鳥類雛絨毛演化更深一層的認識。

Birds can be classified into precocial birds and altricial birds according to their morphologies and behaviors. One of the most obvious differences is their natal down development in hatchlings. Precocial birds’ hatchlings are covered with down feathers, while that of altricial birds are almost naked. Precociality in birds is considered to be ancestral based on fossil evidence and phylogenetic analysis. In a previous study, we found that the formation of natal down of zebra finch (Taeniopygia guttata) hatchling, an altricial bird, is repressed by the fibroblast growth factor (FGF) signaling pathway. To discover the natal down suppression (NDS) mechanism in other altricial birds, we used budgerigar (Melopsittacus undulates), which is also an altricial bird, as another model to investigate their NDS mechanism. Besides, we also found that the pattern formation of placodes in duck (Anas platyrhynchos domestica) embryos are different from those of chickens and other domestic birds, showing the diversity of natal down development in precocial birds. We applied in situ hybridization assay and Strain-specific RNA sequencing on selected species to observe candidate gene expression, then comparing them with the results in previous studies. Our results suggested that budgerigars share similar FGF signaling pathway with finches. We also suggested that an antisense SHH RNA may play an inhibitory role in ducks. This study provides a deeper understanding of natal down evolution in birds.

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