PUBERTY IN THE MALE CHIMPANZEE - PROGRESSIVE MATURATION OF SEMEN CHARACTERISTICS

Cellular and biochemical characteristics of semen obtained by masturbation were studied in 5 pubertal chimpanzees during 1.5 yr. The dental age corresponding to the beginning of the pubertal testicular growth (Po) range from 5.0 to 8.3 years (mean = 6.7 +/- 1.2 yr). Time-related variations of all studied parameters were analyzed according to Po and, therefore, independently of the dental age. The emission of first ejaculates, and therefore the onset of activity of the accessory sex gland, was estimated to occur 4 mo after Po. The ejaculate volume (n = 132, r = 0.704, p < 0.001), as well as the total amounts of l-carnitine (n = 65, r = 0.649, p < 0.001), fructose (r = 0.522, p < 0.001), citrate (r = 0.748, p < 0.001), and acid phosphatase (r = 0.756, p < 0.001) increased with time. First-obtained ejaculates contained no spermatozoa. Spermarche was estimated to occur 9.4 mo after Po. Total sperm count increased with time (r = 0.595, p < 0.001). The motility and viability of spermatozoa increased with time (r = 0.474, p < 0.01 and r = 0.632, p < 0.001, respectively) while their morphology did not vary. The volume of the liquefied fraction and its content in free spermatozoa considered as available for fecundation remained low until the end of the study, most likely because of a delayed maturation of the prostate. This study shows that the maturation of the male genital tract is a progressive process. The potential for fertility may not be acquired before the complete growth of the accessory sex glands, thus not before 2.5 yr after the onset of the pubertal testicular growth.