Cryopreservation of Sperm of an Endangered Species— Assamese Macaque

Abstract

The Assamese macaque (Macaca assamensis) is a rare and endangered species, which can only be found now in northern India and southwest China. There is an urgent need to cryopreserve Assamese macaque sperm for the conservation of this endangered species. Spermatozoa were collected from four adult male monkeys (Assamese macaque) using penile electroejaculation. In the light of the previous research on cryopreservation of cynomolgus macaque and rhesus monkey sperm, we developed an effective technique for cryopreservation of Assamese macaque sperm using TTE (TES + Tris + egg yolk) as an extender (base solution) with 5% (vol/vol) glycerol (as a cryoprotectant). Sperm motility and sperm penetration rate of zona-free hamster oocytes were measured to evaluate post-thawed sperm viability and function. In comparison with fresh sperm, the post-thawed sperm motility right after thawing was 69 ± 5% (n = 9). After incubation for 1, 2, 4, 6, 8, and 10 h, post-thawed sperm motility was 60.6 ± 2.1, 37.9 ± 12.4, 31.4 ± 14.3, 20.7 ± 18.5, 17.1 ± 16.0, and 2.0 ± 1.6% (n = 3), respectively. In contrast, after incubation for 1, 2, 4, 6, 8, and 10, the fresh semen sperm motility was 74.0 ± 1.8, 67.0 ± 5.6, 60.7 ± 5.1, 40.4 ± 12.7, 29.1 ± 13.0, and 14.1 ± 6.1% (n = 3), respectively. The rate of penetration of zona-free hamster oocytes by frozen-thawed spermatozoa was 39.4% versus 53.2% by fresh sperm. In conclusion, the developed technique and the cryopreservation solution are useful and effective for cryopreservation of Assamese macaque sperm.