Table of Embryonic Stages

 

Developmental timetables for the Drosophila melanogaster embryo
(at 25°C)
Stage Time (hours) Developmental event
1 0–0:25 First two nuclear divisions. Egg uniformly dark in center and light at periphery.
2 0:25–1:05 Nuclear divisions 3–8. Egg cytoplasm retracts considerably from vitelline envelope,
leaving empty space at anterior and posterior poles.
3 1:05–1:20 At posterior end, three polar buds form (later to pinch off and become pole cells), and
divide once. Nuclear division 9. Dividing blastoderm nuclei cause granulated appearance in wide zone in periphery. Empty space at anterior pole disappears.
4 1:20–2:10 Blastoderm nuclei in periphery making a bright peripheral rim. Nuclear divisions 10–13,
just prior to cellularization. Two more divisions in polar buds.
5 2:10–2:50 Cellularization of the blastoderm occurs, and nuclei elongate considerably. Pole cells
begin to shift dorsally. Midventral blastoderm cells look irregular and wavy, preceding
their invagination.
6 2:50–3:00 Early gastrulation: ventral furrow forms, from which mesoderm and endoderm originate;
at posterior pole, cells shift dorsally to form a dorsal plate to which pole cells adhere;
cephalic furrow becomes visible as a lateroventral slit.
7 3:00–3:10 Endoderm of anterior and posterior midgut and ectoderm of hindgut invaginate; dorsal
folds appear.
8 3:10–3:40 Amnioproctodeal invagination, rapid phase of germ band elongation.
9 3:40–4:20 Transient segmentation of the mesodermal layer, visible in region of germ band as
prominent bulges protruding into yolk sac.
10 4:20–5:20 Stomodeum invaginates ventrally at anterior pole. Germ band continues to expand.
Interior of egg occupied by yolk sac which is a dark, uniform mass. Periodic furrows in
epidermis appear. Pole cells leave cavity of posterior midgut and locate themselves
dorsally outside yold sac. Primordia of Malpighian tubules form. Neuroblasts divide.
11 5:20–7:20 Growth with no major morphogenetic changes. Intersegmental furrows form in
epidermis; mandible, maxilla, and labium visible as protuberances. Germ band extension reaches its maximum extent. Posterior pole becomes withdrawn from vitelline envelope.
12 7:20–9:20 Shortening of the germ band so that opening of hindgut becomes located at dorsal side of posterior pole. Width of germ band increases. Anterior and posterior midgut clearly
visible and fuse. Germ band segmentation very prominent.
13 9:20–10:20 Germ band shortening completed. Conspicuous triangular gap ventrally due to retraction of clypeolabrum. Labium moves to ventral midline, displacing opening of salivary gland and duct. Yolk sac protrudes dorsally, has characteristic convex shape. Dorsal fold (ridge) appears. Head involution begins.
14 10:20–11:20 Head involution continues. Dorsal closure and closure of midgut. Anal plate ventrally
displaced from posterior tip. Dorsal spiracles evident.
15 11:20–13:00 Dorsal closure and dorsal epidermal segmentation. Gut forms closed tube containing yolk sac. Supraoesophageal ganglia and pharynx evident.
16 13:00–16:00 Intersegmental grooves distinguishable middorsally. Dorsal ridge overgrows tip of
clypeolabrum. Constrictions appear in midgut. Shortening of ventral cord.
17 16:00–24:00 Tracheal tree contains air. Retraction of ventral cord continues. Embryo hatches as first
instar larva.
Source: After Campos-Ortega and Hartenstein, 1985. The Embryonic Development of Drosophila melanogaster. Springer-Verlag, Berlin.