EFFECTS OF FERTILIZATION AND DEVELOPMENT ON THE OXIDATION OF CARBON MONOXIDE BY EGGS OF STRONGYLOCENTROTUS AND URECHIS AS DETERMINED BY USE OF C¹³

¹ Division of Biology, California Institute of Technology, Pasadena, California

1. The rates of gas-uptake and oxidation of CO (labelled with C¹³) have been determined for developing eggs of the gephyrean, Urechis caupo, and for unfertilized eggs and developing embryos of the sea urchin, Strongylocentrotus purpuratus. In the light in 80% CO/20% O₂, there is excess gas-uptake over that of the aircontrols at all stages of development, but the percentage of excess uptake falls off as development proceeds. In the dark there is increasing inhibition of respiration by CO during development.

2. The rate of CO-oxidation in the light increases less than two-fold in Urechis during 50 hours of development. In Strongylocentrotus the rate of CO-oxidation in the light nearly doubles after fertilization, but increases relatively little during later development.

3. In the dark, in Urechis, the rate of CO-oxidation during early cleavage is about half that in the light, but the dark-rate decreases five-fold during the swimming stages. In the sea urchin there is only a slight decrease in rate of CO-oxidation during development. The developmental changes in the ratio of dark-to-light oxidation of CO are interpreted on the basis of an increasing degree of saturation of cytochrome oxidase with its reducing substrate.