Oxygen and Air Pressure Effects Upon the Early Development of the Frog's Egg

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Abstract
In Rana pipiens, pituitary-stimulated eggs were brought in before the breeding season and kept at 1[degree]C. In eggs deposited under natural conditions, the period of development during which the expt. was initiated varied between the 4-and the 16-cell condition. The pituitary-induced eggs were placed in a pressure chamber 15-20 mins. after sperm suspension was added. Pressures up to 3 atm. of O2 were added to the normal airpressure in the pressure chambers. Small eggmasses were placed in glass dishes and covered with water which remained unchanged while the eggs were in the chambers. Control eggs were kept in shallow water which was changed daily and were watched up to the late yolk plug and early neurulation state, after which the pressure chambers were open. The expts. were done at 14[degree]-20[degree]C, and in some cases at 16[degree]-25[degree]C. The pressures of O2 had no gross morphologic effect upon development through the blastular stage. Increased pressures accelerated gastrulation and neurulation. Embryos subjected to this treatment, then removed and placed in shallow fresh water, developed as follows: (1) up to 11/2-2 atm. no deleterious effects were found in the tadpoles. They showed accelerated development compared with controls; (2) at 3 atm. there were various conditions of abnormal development in the tadpoles. O2 at 1-11/2 atm. appeared beneficial to early development. In pituitary induced eggs, 1 atm. added to the normal air accelerated development. Similar pressures produced a recovery effect in some of these pituitary-induced eggs. Pressures of 3 atm. suppressed development at an advanced blastular condition.

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