INDEPENDENCE OF POST-FERTILIZATION RESPIRATION IN THE SEA-URCHIN EGG FROM THE LEVEL OF RESPIRATION BEFORE FERTILIZATION

Abstract

Using the Cartesian diver micro-respiration technic it was found that in Psammechinus miliaris the rate of respiration of the newly fertilized egg is independent of the rate of respiration of the unfertilized egg at the moment of fertiliza- tion. The quotient (respiration after fertilization)/(respiration before fertilization) decreased considerably (probably even to values less than 1) if the time interval between egg removal from the ovary and fertilization was diminished. This means that the respiration of the just-removed egg is actually higher than that of the fertilized egg during the first hrs. of development. If the decreasing part of the pre-fertilization respiration is given time to disappear (approx. 4 hrs.) before fertilization, the quotient lies between 3 and 4. It is thought possible that the decreasing respiration part of the unfertilized egg is abolished upon fertilization, due to probable changes in the function of members of the oxidizing system, situated between the oxidase and the dehydrogenases. It cannot be decided from the expts. whether the constant respiration part of the unfertilized egg still participates in the respiration of the fertilized egg or not. From the R. Q. values it appears probable that different substrates are utilized before and after fertilization.