LYTIC EFFECTS OF SPERM EXTRACTS ON THE EGGS OF MYTILUS EDULIS

¹ Department of Zoology and the Division of Medical Physics, University of California, Berkeley, California

Extracts of Mytilus sperm contain a lytic substance, or substances, which causes dissolution of the egg membrane and the intercellular cement which binds the blastomeres together. Bioassays were utilized to investigate the occurrence and relationship of the active agents and some of their chemical properties. The lytic effects are exhibited by concentrated sperm suspensions and their supernatants obtained by centrifugation. Extracts prepared by freezing and thawing and by acidification or alkalization exhibit the same relative strengths of lytic activities.

The active agents are large molecules, as indicated by their non-dialyzability through cellophane. They are precipitated by ammonium sulfate, by dialysis against distilled water, and by alcohol. These properties indicate a protein nature of the lytic substances, an assumption which is further supported by the fact that they are inactivated by trypsin.

While there is no conclusive evidence that there are two separately acting lysins, this is strongly suggested, in part, by a differential inactivation of sperm activities by heat. The membrane lysin is heat labile whereas the cement-lytic activity is relatively heat stable. It is concluded that the latter effect is not brought about by a binding of free calcium of the sea water.

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