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.^[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]

Embryo of Zebrafish undergoing cleavage

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.

• Early Development in Fish
• Early Development in Birds