One strength of the chicken (Gallus gallus domesticus) as a model organism for developmental biology is that the embryo develops outside the female and is easily accessible for experimental manipulation. Many techniques allow scientists to examine chicken embryos inside the eggshell (in ovo), but embryonic access can be limited at later stages of development. Fortunately, chicks can also be cultured ex ovo, or outside of the eggshell. The major advantage to ex ovo culture is greater access to tissues that might otherwise be obstructed by the shell or the orientation of the chick within the egg, especially for embryos in later stages of development.

There are two principle strategies to ex ovo culture: whole yolk culture and explant culture. During whole yolk culture, the eggshell is cracked and the contents are transferred to a simple housing vessel. However, in explant culture methods, the embryo is excised from the yolk and mounted in the housing vessel to maintain membrane tension, which is important for normal development.

Basic protocols for whole-yolk and explant techniques will be provided in this video, along with a discussion of the pros and cons of culturing chicks outside of the shell. Finally, experimental applications of ex ovo culture will be discussed, demonstrating how this approach is used to improve access to the embryo for microscopy and genetic manipulation of late stage embryos.