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Table 2 Comparative developmental guide for cephalopod development

From: A practical staging atlas to study embryonic development of Octopus vulgaris under controlled laboratory conditions

Octopus vulgaris Doryteuthis pealei Sepia officinalis General characteristics Stage
Adapted from Naef, 1928 Arnold, 1965 Boletzky, 2016   
Fertilized egg Stage 1 Stage 1 Newly laid fertilized egg that did not finish maturation Segmentation (cleavage)
First maturation division Stage 2 Stage 1 First polar body Segmentation (cleavage)
Second maturation division Stage 3 Stage 1 3 polar bodies Segmentation (cleavage)
2 cells, first cleavage Stage 4 Stage 2 Two partially separated cells Segmentation (cleavage)
4 cells, second cleavage Stage 5 Stage 3 Four partially separated cells Segmentation (cleavage)
8 cells, third cleavage Stage 6 Stage 4 Eight incompletely separated cells Segmentation (cleavage)
16 cells, fourth cleavage Stage 7 Stage 5 2 completely closed blastomeres, 14 blastocones Segmentation (cleavage)
32 cells, fifth cleavage Stage 8 Stage 6 12 blastomeres, 20 blastocones Segmentation (cleavage)
64–66 cells, sixth cleavage Stage 9 Stage 7 36 blastomeres, 28 blastocones Segmentation (cleavage)
Stage I Stage 10 Stage 8 Morula (advanced cleavage) Segmentation (cleavage)
Stage II Stage 10 Stage 9 Blastula Segmentation (cleavage)
Stage III Stage 11 Stage 10 Onset of epiboly Gastrulation
Stage IV Stage 12 Stage 11–12 Formation of the germinal disk (yolk envelope & embryonic proper) Gastrulation
Stage V Stage 13 Stage 13 Epiboly continues Gastrulation
Stage VI Stage 14–15-16 Stage 14 Mesoderm concentrations become more distinct (smooth surface) Epiboly
Stage VII.1 Stage 17 Stage 15 Visible thickening of placodes starts Epiboly
Stage VII.2 Stage 18 Stage 15 Primordia of mantle, eyes, mouth and arms visible Epiboly/ Organogenesis
Stage VIII Stage 19 Stage 16 Mouth and eye invagination, funnel pouches and statocysts visible Organogenesis
Stage IX Stage 20 Stage 17 Primordia more prominent. Funnel tube rudiments are distinct Organogenesis
Stage X Stage 21 Stage 18 Eye vesicles closed and sticking out. Funnel tube rudiments fuse ventrally Organogenesis
Stage XI Stage 22 Stage 19 Mantle starts to grow. Funnel tube rudiments bend towards midline Organogenesis
Stage XII.1 Stage 23 Stage 20 Funnel tube rudiments start to form a tube ventrally. Mantle covers 1/2nd of gills Organogenesis
Stage XII.2 Stage 23 Stage 20 Funnel formed siphon at ventral extremity. Mantle bowl-shaped Organogenesis
Stage XIII Stage 23 Stage 21 Formation of the funnel complete. Iris fold rudiment visible Organogenesis
Stage XIV Stage 24 Stage 22 Mantle as wide as long and covers gills completely Organogenesis
Stage XV.1 Stage 25 Stage 23 Mantle covers ventral margin of funnel. Inner yolk strongly constricted Organogenesis
Stage XV.2 Stage 26 Stage 24 Mouth starts to internalize Organogenesis
Stage XVI Stage 27 Stage 25–26 Few anterior chromatophores evident. Mouth completely covered by arm crown Organogenesis
Stage XVII Stage 28 Stage 27 Mantle enlarged in relation to head. Chromatophores numerous Organogenesis
Stage XVIII.1 Stage 28 Stage 27 Yolk sac same size as head (Octopus & Loligo) Growth
Stage XVIII.2 Stage 28 Stage 27 Chromatophores darker Growth
Stage XIX.1-XIX.2 Stage 29 Stage 28 Pigmentation of ink sac. Eyes covered with iridophores Growth
Stage XX.1 Stage 29 Stage 29 Yolk nearly depleted Growth
Stage XX.2 Stage 30 Stage 30 Loss of outer yolk and hatchling Growth