The effect of stress on semen reduction in the marmoset monkey (Callithrix jacchus)

This study compared a number of semen parameters of two separate groups of the common marmoset monkey (Callithrix jacchus) in order to determine the effect of a continuous potentially stressful situation on these parameters, and thus on the monkey's reproductive ability. The semen from 16 adult male marmoset monkeys was collected and analysed to compare semen parameters between a 'normal' (control) group (n = 9) and a 'blood withdrawn' ('stress') group (n = 7). The semen parameter values observed in the control were: pH 7.51 +/- 0.22, volume 40.2 +/- 27.2 mu l, concentration 27.3 +/- 14.8x10(4)/mu l, motility 47.4 +/- 15.9%, grade of velocity 3.5 +/- 1.2, and normal morphological forms 51.8 +/- 13.7%. The 'blood withdrawn' group of marmoset monkeys showed significantly lower semen volume and sperm concentration than the 'normal' group. In addition, total count of spermatozoa, normal spermatozoa, motile spermatozoa and normal motile spermatozoa per ejaculate per monkey was significantly reduced in the 'blood withdrawn' group. The semen of these monkeys also revealed a significantly higher percentage of abnormally-shaped sperm heads than the normal group, and cases of impotence and sham ejaculation were recorded. Our study revealed that the continuous withdrawal of a small volume of blood from a group of marmoset monkeys appeared to be stressful to these monkeys and as a result, influenced their semen parameters, possibly making them less fertile. In addition, electroejaculation was found to be possibly harmful to the monkey's reproductive ability.