Thirty fertilized chick eggs preincubated for 0, 7 and 10 days on earth (10 eggs each) were flown in the space shuttle 'Endeavour' and further incubated for 7 days under microgravity. Twenty out of thirty eggs ( 9 10 ten-day-old; 10/10 seven-day-old; 1 10 zero-day-old) were recovered alive after landing. The only living embryo of the zero-day-old group died 24 days after launch, and was comparable to a 16-day-old embryo. The high mortality of the 0-day-old eggs appeared to be related to the specific inner structure of the egg. Simulation experiments performed on earth indicated that when yolk stayed in the albumen for more than 2 days, most of the embryos died. The subtle difference in specific gravity between the yolk (1.029) and albumen (1.040) plays a critical role in early chick embryogenesis. © 1994.
Suda, T., Abe, E., Shinki, T., Katagiri, T., Yamaguchi, A., Yokose, S., … Naito, M. (1994). The role of gravity in chick embryogenesis. FEBS Letters, 340(1–2), 34–38. https://doi.org/10.1016/0014-5793(94)80168-1