THE INFLUENCE OF HYDROGEN ION CONCENTRATION ON THE FERTILIZATION PROCESS IN ARBACIA, ASTERIAS AND CHÆTOPTERUS EGGS

¹ From the Lilly Research Laboratory, Indianapolis and the Marine Biological Laboratory, Woods Hole

When Arbacia, Asterias and Chætopterus eggs are inseminated in CO₂-free sea water of varying H-ion concentration, a block to fertilization appears at a H-ion concentration which is constant, and apparently characteristic for each species. If the block is defined by the H-ion concentration at which 50 per cent. of the eggs fertilize, these H-ion concentrations are: Arbacia, pH 6.8; Asterias, pH 7.0; and Chætopterus, pH 7.1.

This block to fertilization is complete, in that eggs either fertilize and develop normally, or do not fertilize at all; and it is perfectly reversible, in that eggs which do not fertilize on the acid side of the block will fertilize immediately if they are returned to solutions on the alkaline side of the block and inseminated with fresh sperm.

In sea water more alkaline than pH 9.8 to 10.0 the fertilization process in both Arbacia and Asterias eggs is either incomplete or impaired. Apparently there is no alkaline block to fertilization corresponding in its complete reversibility to the block which appears around neutrality.

In Arbacia there is an increased incidence of polyspermy within a very narrow range centering at pH 7.2, indicating some critical condition in the mechanism of fertilization at this H-ion concentration. In Asterias polyspermy occurs more or less uniformly over a wide range extending from pH 7.2 to 9.8.