Cryopreservation of lar gibbon semen collected by manual stimulation.

Abstract

We confirmed ejaculation as a result of manual stimulation in a lar gibbon, and attempted to cryopreserve the semen using TES-Tris-egg yolk-based (TTE) extender. After measuring the amount of semen (g), we first diluted the semen with TTE extender, and calculated sperm concentration (sperm/ml), total sperm count (sperm), and progressive sperm motility (%). Then, we cooled diluted semen slowly to 4°C over 2h, and added an equal volume of secondary extender containing glycerol over 30min. Finally, we flash-froze the semen solution by plunging into liquid nitrogen. In addition, we freeze-thawed the solution to determine the recovery rate of the motile sperm. Collection of semen was successful on four of the five occasions. The median (min-max) quantity of ejaculate was 0.19g (0.09-0.26g), the median sperm concentration was 1.38×10(9)sperm/ml (1.20-1.53×10(9)sperm/ml), and the median total sperm count was 0.26×10(9) sperm (0.11-0.40×10(9) sperm). Moreover, the median sperm motility immediately after ejaculation was 65% (60-75%), the median sperm motility after freeze-thawing was 30% (25-35%), and the median recovery rate was 42.3% (40.0-58.3%). We were able to (1) collect semen from a lar gibbon by manual stimulation, (2) reveal andrological findings regarding semen characteristics, and (3) preserve the genetic resource using TTE cryopreservation.