Sperm duct contractions mediate centrally evoked sperm release in goldfish

In order to determine the peripheral mechanisms underlying sperm release (SR) in goldfish, the contractile activity of the sperm ducts (SD) and testes were monitored during SR responses evoked by electrical stimulation of the brain. Electrical stimulation of the brain triggered testicular and SD contractions, and SR, while electrical stimulation of the genital nerve branch to the SD evoked only SD contractions and SR. Centrally activated SD contractions and SR were blocked by sectioning the SD genital nerve, while testicular contractions were unaffected. Testicular contractions do not appear necessary for centrally evoked SR since the response can be elicited from preparations in which the testes were separated from the SD. The results indicate that SR in goldfish is primarily mediated by the SD and not the testes. Testicular contractions may, however, serve to load the SD with milt. The functional significance of the central pathway(s) associated with SD and testicular contractions are discussed.