Relation of intracellular pH and pronuclear development in the sea urchin,Arbacia punctulata,: A fine structural analysis

Zygotes, treated with sodium-free artificial seawater (Na-free ASW) in order to inhibit the elevation of intracellular pH at fertilization, were examined by light and electron microscopy. Although such specimens elevated fertilization membranes, male pronuclear development and sperm aster formation were suppressed. Inhibition of these events was reversed when zygotes were resuspended in seawater or in Na-free ASW containing ammonia. These results indicate that alkalinization following insemination or processes accompanying this alteration induce a pervasive change within the zygote which supports events of fertilization.