INFLUENCE OF IODOACETATE ON ACTIVATION AND DEVELOPMENT OF THE EGGS OF ARBACIA PUNCTULATA

¹ From the Institute of Experimental Zoölogy, Stockholm, Sweden, and the Marine Biological Laboratory, Woods Hole

1. It has been proved by the experiments briefly reported above that monoiodoacetate does not inhibit the fertilization process in the Arbacia egg. Thus enzymatic or other activities in which SH-groups are involved do not play an essential rôle in the fertilization process. The activity of the sperm-agglutinating substance secreted by the egg is not impaired by iodoacetate. The penetration of iodoacetate into the unfertilized egg is ascertained by the presence of morphological defects in larvæ reared from eggs removed from the iodoacetate sea water and fertilized in normal medium.

2. Iodoacetate in the concentration (0.03 m) used in these experiments is harmful to the development of fertilized eggs. There is a remarkable difference in resistance between unfertilized and fertilized eggs towards iodoacetate. The normal increase of respiration following fertilization takes place also in 0.03 m iodoacetate but there is soon a considerable decline of respiration, which can be prevented by addition of pyruvate or lactate. A carbohydrate metabolism must be involved in the oxidation processes in the fertilized eggs. The addition of pyruvate or lactate, although restoring respiration, does not inhibit the injury caused to the fertilized egg by the addition of iodoacetate.

3. The morphological defects caused by a treatment of the eggs by iodoacetate before fertilization are prevented by addition of pyruvate to the fertilized eggs. These results have some bearing on the development mechanics of the sea urchin. A carbohydrate breakdown seems to be a necessary condition for the full morphological differentiation of the anterior or animal region of the larva.