Photographic Study of Chick Embryo Development In vitro

Abstract

A photographic study of development of chick embryos cultured in vitro was conducted in order to demonstrate the relationship between embryos and extraembryonic membranes during culture. Survival of embryos in this system has been extended to 21 days of total incubation (3 days in shell plus 18 days in vitro) and development to Hamburger-Hamilton stage 45 (partial or complete yolk sac retraction). A few mature cultured embryos have “pipped” through the chorioallantoic membrane and have emitted audible peeping. Three-day embryos and egg contents were cultured in commercial plastic wrap suspended in plastic tripods. The yolk sac expanded and flattened to cover the bottom of the culture chamber by five days of total incubation. Downgrowth of the yolk sac vascular system along the plastic wrap walls of the chamber began by six days, while downgrowth of the chorioallantoic membrane (CAM) began by eight days. The CAM often completely enclosed cultured egg contents by 17 days, an event which occurs in ovo by 11 to 12 days. Lack of formation of the albumen sac resulted in inhibition of albumen uptake during the latter portion of incubation. A small number of embryos were on their right side rather than on the normal left side during the first two days of culture. Many of the right side cultured embryos experienced “compensatory torsion” onto their left side by three days of culture (six days of total incubation).