Author

Lucas Leclère

Additional Author(s): Evelyn Houliston

Published on SDB CoRe: Sep 10 2012

Tools & Techniques: Microscopy
Early Embryogenesis: Cleavage; Blastula
Embryonic Patterning: Axis Formation
Organism: Clytia
Stage of Development: Embryo

Object Description

This is a time lapse recording of a developing Clytia hemisphaerica (Cnidaria, Hydrozoa) embryo from the fertilized egg until blastula stage. The movie covers approximately 9 hours at 18°C, with one image taken every 2 minutes. The animal pole is positioned towards the top right corner at the initiation site of the first cleavage furrow, and at the cleft between the lobes during cleavage. The commonly observed peanut/heart shape of the blastula seen in this example (00:05-00:16 seconds) results from a transitory fold in the epithelial layer during cleavage stage—not related to gastrulation—that can be traced back to the first cleavage (00:00-00:01). The left lobe of the peanut-shaped blastula corresponds to the left blastomere from the first cell division, and the right lobe to the right blastomere. The major cleft between the two halves corresponds to the initiation side of the cleavage furrow at the animal pole of the 1-cell embryo. Clytia blastulae show quite variable and irregular forms with 50 to 70% of the blastula presenting the peanut/heart shape, the other 50-30% showing variable irregular shapes throughout cleavage and blastula stages. Later during development gastrulation will take place at the animal pole leading to the formation of the endoderm and ectoderm, the animal pole becoming the oral/posterior pole of the planula larvae. This recording was made on a Zeiss inverted microscope equipped with a motorised stage driven by "MetaMorph" software (Molecular Devices, Sunnyvale, CA).

References

Leclère, L., Jager, M., Barreau, C., Chang, P., Le Guyader, H., Manuel, M., Houliston, E. Maternally localized germ plasm mRNAs and germ cell/stem cell formation in the cnidarian Clytia. Dev Biol, 2012, 364:236-248.

Houliston, E., Momose, T., Manuel, M. Clytia hemisphaerica: a jellyfish cousin joins the laboratory. Trends Genet, 2010, 26:159-167.

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