Molecular Staging Resource

Developmental timeline and staging designations for Smed embryogenesis.
Timeline: days (d) post egg capsule deposition at 20˚C. Gray bars indicate time windows for RNA-Sequencing samples. Double headed arrows: time windows for Stages (S) S1-S8.



Click here for Single Embryo RNA-Sequencing Analysis Material and Methods

Stage NameTimeDescriptionIllustration

Stage 1

D0-D2Zygote and dispersed blastomere cleavage in a yolk syncytium.

Stage 2

D2-D3Sphere formation. A fraction of the blastomeres differentiate into temporary embryonic tissues that provide form and function to the embryo. Undifferentiated blastomeres remain in the embryonic wall.

Stage 3

D2-D4Dispersed blastomere cleavage in the embryonic wall of nascent spheres. Yolk ingestion into the gut cavity.

Stage 4

D3-D5Dispersed blastomere cleavage in the embryonic wall. Yolk ingestion into the gut cavity. Early embryonic gut formation.

Stage 5

D5-D7Organogenesis onset. Downregulation of early embryo enriched transcripts and birth of adult lineages in blastomere population. Early embryonic gut formation continues. Yolk ingestion into the gut cavity.

Stage 6

D7-D9Organogenesis and morphogenesis. Definitive organ formation. Temporary embryonic cell types degenerate. Embryo elongation.

Stage 7

D9-D11Organogenesis and organ maturation continues. Onset of gliding motility.

Stage 8

D13-D15Organogenesis and organ maturation continues. Hatching.