Penile vibrostimulation (PVS), a noninvasive repeatable method, has been shown in the squirrel monkey to yield semen of higher quality than rectal probe electro‐ejaculation (RPE). The present study aimed at establishing the conditions for PVS to collect ejaculates from marmoset monkeys. Ten adult males were trained on the appropriate handling before each was subject to six to 12 PVS tests. Ejaculation was stimulated using a FertiCare® personal vibrator fitted with a 2 cm × 0.5 cm i.d. glass tube. The stimulus was repeatedly applied over a frequency of 75–95 Hz and amplitude of 1–2 mm for up to 20 min. Ejaculates were analyzed for volume, total sperm number, sperm concentration, and proportion of living and motile sperm. Ejaculates were obtained in 31 of 88 PVS tests; 87.1% of the ejaculations occurred at 80–85 Hz frequency and 1–1.5 mm amplitude. In 18 tests ejaculates were produced within 49.7 seconds. Ejaculates were characterized by (mean values): volume 31.9 μl, total sperm number 34.2 × 106/ejaculate, concentration 1,154.2 × 106 sperm/ml, live sperm 74.6%, motile sperm 59.6%. Total number and concentration of spermatozoa were significantly enhanced in singly living males. PVS yielded three to four times more spermatozoa than comparable previously published values for RPE. Enhancing the success rate by preselecting males for responsiveness may render PVS the sperm collection method of choice in marmoset monkeys. Am. J. Primatol. 52:149–154, 2000. © 2000 Wiley‐Liss, Inc.

Assisted reproductive techniques make an important contribution to the conservation of endangered primate species. In our laboratories marmoset monkeys (Callithrix jacchus) are used as a model species for developing assisted reproductive technologies for New World primates. The studies require a reliable method for collecting functional sperm from these small animals. For this purpose a minimally invasive procedure, vaginal washing after natural mating, was evaluated for its suitability as a routine method of obtaining ejaculated sperm of high quality. The objective of the first series of tests was to identify a behavioural pattern which was easily discernible by the observer and provided a reliable indication that ejaculation had occurred. In a second series of tests the influence of length of separation of the male prior to copulation on the quality of the ejaculate was evaluated. Six adult ovariectomized and five adult intact females were used for vaginal washing, while their mates served as donors of ejaculates. Matings at specific times were achieved by separating the males from their females for a certain time period and subsequently introducing either their own mates or unfamiliar males to the females. After each observed mating vaginal washing was performed on the unsedated females. The seminal samples obtained were analysed for sperm concentration, the proportion of motile sperm and the proportion of live sperm. The results have shown (a) that ejaculation was indicated with a reliability of 86.1% by the behaviour of the female, who terminates a copulation by moving away from her partner; (b) that separation of the male for up to six days had no negative effect on the sperm quality; (c) that the sperm samples were of high quality. Vaginal washing after natural matings appears to be a practical, reliable and gentle method for routinely collecting ejaculates from marmoset monkeys and possibly other New World primates.

Ultrasonography was used in six saddle back tamarin females (Saguinus fuscicollis) to diagnose pregnancy, monitor the patterns of uterine growth and embryonic/foetal development and examine the incidence loss of single embryos/foetuses. Pregnancy was reliably diagnosed 17 days after conception, 10 days earlier than by plasma progesterone measurement. The patterns of uterine and embryonic/foetal growth paralleled those reported for the common marmoset, including a delay in embryonic development. The results support the hypothesis of retardation of organogenesis in most callitrichid species. Individual embryos could be reliably identified from day 50 of pregnancy; a loss of single embryos/foetuses after this stage did not occur. All pregnancies were carried to term, resulting in five times twins and one singleton. The smaller litter size compared to the common marmoset may be due to loss of single embryos at earlier stages of pregnancy or to a lower ovulation rate.

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