Article · Wikipedia archive · Last revised Jul 24, 2026

Blastodisc

The blastodisc, also called the germinal disc, is the embryo-forming part on the yolk of the egg of an animal that undergoes discoidal meroblastic cleavage. Discoidal cleavage occurs in those animals with a large proportion of yolk in their eggs, and include insects, fish, reptiles and birds. The blastodisc is a small disc of cytoplasm that sits on top of the yolk. In birds, it is a small, circular, white spot on the surface of the yellow yolk of an egg, at the animal pole.

Last revised
Jul 24, 2026
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Embryo of Zebrafish undergoing cleavage source ↗

The blastodisc, also called the germinal disc, is the embryo-forming part on the yolk of the egg of an animal that undergoes discoidal meroblastic cleavage.1 Discoidal cleavage occurs in those animals with a large proportion of yolk in their eggs, and include insects, fish, reptiles and birds.2 The blastodisc is a small disc of cytoplasm that sits on top of the yolk. In birds, it is a small, circular, white spot (approximately 1.5-3 mm across) on the surface of the yellow yolk of an egg, at the animal pole.3

References

References

  1. "Definition of BLASTODISC". www.merriam-webster.com. Retrieved 15 October 2022.
  2. Gilbert, Scott F. (2006). Developmental biology (8th ed.). Sunderland, Mass.: Sinauer Associates Publishers. p. 215. ISBN 9780878932504.
  3. Gilbert, Scott F. (2006). Developmental biology (8th ed.). Sunderland, Mass.: Sinauer Associates Publishers. pp. 336–337. ISBN 9780878932504.