pH in the Jelly Layer of Starfish Oocytes: (starfish oocytes/jelly layer/pH)

Using liquid ion exchanger micro-electrodes we have studied the pH in the vicinity of starfish oocytes and eggs and also in their jelly layers. Although highly variable, the pH in these zones was consistently lower (6.3-7.6) than the pH of sea water (7.8-8.2). Aged oocytes/eggs presented more acid environments than fresh oocytes. The pH indicator Phenol Red shows that the ovarian fluid is more acid than seawater, ranging from 6.0 to 7.5. Our data suggests that starfish oocytes, from their time in the ovary until several hr after their release, are surrounded by an acid environment. This micro-environment may play a role in metabolic repression in the ovary and in the regulation of sperm-egg interaction following spawning.