Table 1.

Embryonic Staging Indexes and Twin‐tail Goldfish Specific Features

Period	Representative staging indexesa	Specific features of twin‐tail goldfish
Zygote	Perivitelline space, cytoplasm moves to animal pole to form the blastodisc	Under the light microscope, specific features were not detected from zygote to gastrula periods
Cleavage	The number of cells
Blastula	The shape of the blastodisc
Gastrula	The shape of the blastoderm
Segmentation	Somite number, appearance of Kupffer's vesicles, yolk extension, lens and otic vesicles, extended tail and sculpted brain	Enlarged tail bud, polymorphic appearance of Kupffer's vesicles
Pharyngular	OVC, pectoral fin appearance, pigmentation in retina and skin, shape of the median fin fold	Bifurcated median fin folds and enlarged blood island
Hatching	Pectoral fin morphology, xanthophore patterns, caudal fin fold shape	Bifurcated caudal fin fold and expansion of the posterior side of the yolk

^a Modified from Tsai et al., 2013