A time-lapse photographic study of chick embryos exposed to teratogenic doses of hypoxia

Continuous, long-term observations of amniote embryos have always been difficult. Special culture techniques for young avian and mammalian embryos have been developed (New, 1967) and these have helped to visualize the early stages of development. But studies of normal and abnormal development during the major period of organogenesis have been made largely by tedious indirect methods, such as the examination of a series of embryos preserved at different time intervals. Transitory responses to toxic stimuli have been particularly difficult to detect in this manner. To observe the visible initial effects of teratogenic agents, a photographic time-lapse study of chick embryos in their natural, in ovo, state was initiated. This report compares the changes in normal and hypoxia-treated embryos during the third day of development. Of the many agents which produce abnormal development, oxygen deficiency is one of the better known, since (1) it is readily induced in the laboratory by a variety of means, and (2) it is generally considered to be a significantcause of spontaneously occurring anomalies (Rubsaamen, 1952; Ingalls, 1952).