Dissociation of eusperm bundles by acids, especially by succinate accumulated in the spermatophore of the silkmoth, Bombyx mori

Eusperm bundles and separated parasperm in the vesicula seminalis of the silkmoth, Bombyx mori, were separated by centrifugation in sucrose density gradients. Staining with aceto-orcein showed dissociation of eusperm bundles as well as stained nuclei. This dissociation was induced in the presence of all acids tested. Dilute solutions of endopeptidases dissociated the head part of the eusperm bundle, whereas dilute solutions of acids mainly dissociated the trunk and tail parts. On HPLC on a strongly acidic cation-exchanger column, seven acids were detected in the spermatophore. Of these, succinate was the main component, and only its concentration increased with time. We concluded that with initiatorin, a serine-endopeptidase secreted from the glandula prostatica, succinate serves as eupyrene sperm bundle-dissociating factor in the spermatophore. The possible mechanism of formation of succinate in the spermaophore, which may be associated with glycolysis and the arginine degradation cascade under hypoxic conditions, is discussed.