Activation of saturniid moth sperm by a secretion of the male reproductive tract

Whereas sperm under storage in the seminal vesicles of male Saturniid moths are essentially motionless, they become vigorously motile when ejaculated into the spermatophore. This activation is provoked by a certain secretion of the male's ‘common duct’. The amount of activator in the secretion of a male Antheraea pernyi is prodigious: an extract of a single common duct is sufficient to induce motility in the sperm of nearly half a million male moths. Activating substances could not be recovered from any other tissues or organs of either developing or mature male moths. Nevertheless, substances capable of activating pernyi sperm were obtained from the common ducts of diverse Lepidoptera, and even from the accessory glands of two Orthoptera.Provided that the dilution was not excessive, activated silkmoth sperm in vitro remained optimally motile in a wide variety of solutions having a pH between 5·8 and 7·8 and an osmolarity between 80 and 190 milliosmols. Motility was enhanced in the presence of added protein, but was completely inhibited by dilute concentrations of heavy metal cations. Motility was normal under anaerobic conditions, and even in an atmosphere of carbon monoxide. Apparently the motility of silkmoth sperm can be sustained by glycolysis alone.