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.

 


 



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Stage NameDescriptionIllustration

Stage 1

A stage of Smed embryonic development, 0 - 2 days post-egg capsule deposition at 20C. Zygote and dispersed blastomere cleavage in a yolk syncytium.

Stage 2

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 2 - 3 days post-egg capsule deposition at 20C. Sphere 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

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 2 - 4 days post-egg capsule deposition at 20C. Dispersed blastomere cleavage in the embryonic wall of nascent spheres. Yolk ingestion into the gut cavity.

Stage 4

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 3 - 5 days post-egg capsule deposition at 20C. Dispersed blastomere cleavage in the embryonic wall. Yolk ingestion into the gut cavity. Early embryonic gut formation.

Stage 5

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 5-7 days post-egg capsule deposition at 20C. Organogenesis onset. Downregulation of early embryo enriched transcripts and birth of adult lineages within the blastomere population. Early embryonic gut formation continues. Yolk ingestion into the gut cavity.

Stage 6

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 7 - 9 days post-egg capsule deposition at 20C. Organogenesis and morphogenesis. Definitive organ formation. Temporary embryonic cell types degenerate. Embryo elongation.

Stage 7

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 9 - 11 days post-egg capsule deposition at 20C. Organogenesis and organ maturation continues. Embryos elongated. Eyes just visible. Onset of gliding motility.

Stage 8

A stage of Smed embryonic development defined by a unique gene expression signature and morphology, 13 - 15 days post-egg capsule deposition at 20C. Organogenesis and organ maturation continues. Hatching.