OXYGEN UTILIZATION IN THE SYMBIOSIS OF EMBRYOS OF THE SALAMANDER, AMBYSTOMA MACULATUM AND THE ALGA, OOPHILA AMBLYSTOMATIS

Abstract

1. Oxygen consumption measurements were made on embryos of the salamander, Ambystoma maculatum, which develop within a gelatinous envelope usually inhabited by a unicellular green alga, Oophila amblystomatis, and numerous protozoa and bacteria. 2. A comparison of embryos associated with the alga, and others of the same developmental stage but lacking visible signs of the alga, reveal that the former respire at a greater rate in both early and later stages. 3. In darkness the oxygen consumption of the algae-containing complexes is greater than in the light, suggesting that photosynthesis by the algae answers a portion of the oxygen demand. This is also indicated by the fact that isolated green envelopes consume only half as much oxygen as isolated colorless envelopes. Net consumption by the isolated green envelopes is taken to mean that algal oxygen production is not sufficient to meet the requirements of the heterotrophic inhabitants of the envelope, and therefore could not provide a surplus to the embryo. It is suggested that the higher metabolic rates and more rapid development of embryos associated with algae must depend in part on some factor other than oxygen supplied by photosynthesis. 4. The problem of proving the existence of a growth factor is pointed out, and some additional unsolved problems regarding the life of the alga and its means of penetration into the egg envelope are indicated.