Prolonged survival of mouse epididymal spermatozoa stored at room temperature

The viability and fertility of isolated mouse epididymal spermatozoa kept for up to 7 days at various temperatures (4 degrees C, 22 degrees C, and 37 degrees C) were determined. Spermatozoa kept for 3 days at 22 degrees C were still active, while those kept at 37 degrees C or 4 degrees C exhibited great reduction in motility within 2 days after isolation. In vitro fertilizing abilities of spermatozoa left for 0, 1, 2, and 3 days at 22 degrees C were 69.2, 32.5, 9.5, and 4.9%, respectively, when the cleavage rate to two-cell stage was examined. Transfer of two-cell embryos produced in vitro with spermatozoa left for 1, 2, and 3 days at 22 degrees C resulted in production of fetuses with efficiencies of respectively 30.2, 11.5, and 16.7%, which were lower (63.3%) than that of embryos derived from in vitro fertilization with fresh spermatozoa. These findings indicate that spermatozoa kept for up to 3 days at 22 degrees C can fertilize oocytes, although at relatively low efficiency.