Characterization and partial purification of sperm-activating substance from eggs of the herring, Clupea palasii

Spermatozoa of the herring, Clupea palasii, were immotile in a solution of isotonic to seminal plasma but swimming was initiated in a hypertonic solution such as 60% seawater. This suggests that hyperosmolality is a factor for the initiation of sperm motility in herring. The motility of herring spermatozoa in hypertonic solution remained very low but became active in “egg water,” suggesting that a sperm‐activating substance is released from unfertilized eggs and diffuses into the surrounding environment to promote fertilization. The activity of the egg water was heat stable and nondialyzable, and was lost upon digestion with the proteolytic enzyme, pronase E; thus the substance is a protein. During procedures for partial purification using gel‐filtration chromatography on Sephadex G‐75, the substance was found to be very adherent to the Sephadex beads when buffer solution or the lower salt solution was used as the eluate instead of 0.5 M NaCl. This suggests that the sperm‐activating substance might be attached to the surface of eggs in the relatively lower ionic environment of the female reproductive organ and is released from the eggs when they are spawned into the high salt environment of seawater. © 1992 Wiley‐Liss, Inc.