XY female marmoset (Callithrix jacchus)

A marmoset (Callithrix jacchus) with atypical external genitalia was phenotypically and genetically characterized. Testosterone concentration correlated with that of female marmosets. Externally, there was only one opening for the urethra. Internal genitalia were characteristic of those of female marmosets, and consisted of ovaries, with follicles in various developmental stages, and uterus. Microscopically, a normal vaginal structure was found. An XX/XY chimerism and high steroid hormone values are normally found in common marmosets. Genetic analysis was used for in vivo determination of sex. The Y-linked zinc finger protein gene (ZFY) last intron, and sex-determining region Y gene (SRY) exon were found by use of polymerase chain reaction and posterior sequencing analyses, indicating that this marmoset had Y-linked chromosome sequences. Normal SRY exons can, therefore, be associated with female internal sexual organs in marmosets; this may be the first XY female described in non-human primates.     

Handedness in the common marmoset (Callithrix jacchus)

For about 20 months the development of hand preferences in 21 experimentally naive common marmosets (Callithrix jacchus) was examined in 15 different tests. Test preferences were compared with their spontaneous behavior preferences in such contexts as feeding, grooming, play, and others. In the spontaneous use of the hands, only eight animals showed a significant lateral preference (2 left-handed, 6 right-handed). During the test period, however, the number of handed marmosets increased to 19 (5 left-handed, 14 right-handed). Most of the animals fluctuated considerably in their preference levels, a situation which led to a remarkable test response inconsistency of handedness. When the test situation was changed, complete reversals of handedness were more frequent than weakening or strengthening of a particular preference. The animals' emotions during the test session and environmental variables affected handedness significantly. None of the tested marmosets showed an increase of hand preference from the first to the last test. Our results indicate that Callithrix is ambidextrous rather than handed.     

Intestinal cryptococcosis in a common marmoset (Callithrix jacchus)

A five-year-old female common marmoset (Callithrix jacchus) died after a one-month clinical course of nonspecific signs. Pathologic findings were acute diffuse fibrinonecrotizing enteritis and granulomatous endolymphangitis of intestinal and mesenteric lymphatic vessels. Both lesions were associated with a marked proliferation of Mayer's mucicarmine-positive, 4 to 15 microm yeasts that were surrounded by a wide clear halo. The infection was probably acquired by oral route. Other findings included moderate multifocal granulomatous and necrotizing hepatitis and mesangial nephropathy. Although the immunological status of this marmoset was unknown, cryptococcosis might induce primary lethal intestinal infections in callitrichids.     

Cloprostenol-induced luteolysis in the marmoset monkey (Callithrix jacchus)

A single intramuscular injection of 0.5 micrograms cloprostenol was not luteolytic on Day 6 or 7 of the ovarian cycle (N = 3), but was luteolytic in some animals (3/5) on Day 8 and 9 and luteolytic in all 23 animals treated between Days 10 and 17 of the ovarian cycle, and in 7 animals treated between Days 19 and 43 of pregnancy. Luteal function was monitored by measurement of progesterone in peripheral blood using a simple and rapid non-extraction assay. There was a dramatic fall in peripheral blood progesterone to less than 10 ng/ml within 24 h of cloprostenol injection; progesterone remained at this low level until the day after post-treatment ovulation. The interval from cloprostenol injection to ovulation in animals treated between Days 8 and 17 was 10.7 +/- 0.3 days. A similar interval was found in pregnant animals. Embryos recovered from the uterus after cloprostenol treatment were morphologically normal (23/24).     

Plasma aminotransferase measurements in the marmoset (Callithrix jacchus)

Plasma aminotransferase values were measured in a large number of samples from male and female marmosets. There were no differences due to age or sex for either AST or ALT. Haemolysis affected values for both enzymes, though the effect on ALT was greater.     

Pregnancy diagnosis in the common marmoset (Callithrix jacchus jacchus).

Abdominal palpation of the uterus was carried out on 25 pregnant and 29 non-pregnant marmosets (Callithrix jacchus jacchus). 195 complete 24-hour urine specimens, collected between the first week of gestation and term (21 weeks), were tested with the Sub-Human Primate Tube (SHPT) test. No significant differences between the two methods in their ability to diagnose pregnancy were obtained between the first and 13th week of gestation. The SHPT test was seldom positive after the 13th week of pregnancy, whereas, with one exception, palpation always indicated pregnancy.     

The fertility of daughters in common marmoset (Callithrix jacchus jacchus) family groups

Observations previously made in the field of inter-group mating raised questions concerning the fertility of daughters in family groups and about possible competition between mothers and daughters. To test whether daughters in captive family groups could become pregnant, daughters from four groups were placed with a strange male for a period of 30 min, twice a week for eight weeks. No changes were observed in the mother/daughter interactions during the time in which the daughters were allowed contact with the strange male. Two of the daughters showed signs of ovulation and the male only copulated with these animals. One daughter became pregnant, but it was aggression with her siblings rather than her mother which necessitated removing her from her family group.     

Inhibition of ovarian function in subordinate female marmoset monkeys (Callithrix jacchus jacchus)

Plasma concentrations of progesterone, cortisol, LH and prolactin were measured in dominant and subordinate female marmosets in 10 well-established peer groups. Subordinate females never ovulated, had a reduced LH response to LH-RH and showed no positive feedback LH surge after oestrogen administration. There was no evidence of elevated plasma cortisol levels or hyperprolactinaemia in subordinates and all showed a similar prolactin response to TRH in comparison with dominants. However, subordinates showed a reduced prolactin response to metoclopramide. These results clearly indicate that high circulating levels of cortisol or prolactin are not responsible for the inhibition of ovulation in female marmosets.     

Dental development in the cotton ear marmoset (Callithrix jacchus)

The frequency of minutia types was studied in finger prints of 77 males and 82 females. Dermal ridges were clearly printed by a revised method for this purpose. The fork index, which represents the frequency of forks in minutiae, is higher in females for each finger than in males. It differs on each finger, i.e., low on the digit I, high on the digits, III, IV and V, and intermediate on the digit II. The mean of the index for each finger distributes from about 15 to 24. Bilateral difference is not evident. The correlation coefficient between right and left hands ranges from 0.52 to 0.79. Forks appear more frequently in ulnar loops than in whorls. It is revealed that the occurrence of forks differs in dermal regions.     

Early implantation stages in the marmoset monkey (Callithrix jacchus)

The morphology of the initial stages of implantation in the marmoset monkey (Callithrix jacchus) was studied by obtaining embryos and associated endometrium at timed intervals after ovulation. Estrus cycles were detected by measuring daily levels of plasma progesterone. Following a short follicular phase, circulating levels of progesterone above 20 ng/ml were taken as representing day 1 after ovulation. On this basis, single, twin, and triplet embryos were recovered from six perfused-fixed females on days 13, 16, 19, 23, and 29 after ovulation and prepared in resin for light microscopy. Early implantation stages, 13 and 16 days after ovulation, were characterized by the intrusion of syncytial trophoblast between epithelial cells of the endometrium with minimal cellular damage. Some hyperplasia of epithelium at the margin of the implantation site was evident. The consolidation of the initial attachment was achieved by an increase in syncytial trophoblast underlying the inner cell mass of the embryo which rapidly surrounded and breached maternal capillaries. Although initially separate, the chorions of twin or triplet embryos started to fuse by day 19 after ovulation. This process was complete by day 29 such that embryos shared a common uterine exocoelom surrounded by continuous trophoblast. It was concluded that implantation in the marmoset monkey commenced on days 11-12.5 after ovulation and involved an intrusive mechanism. Although trophoblast penetration of endometrium was superficial, maternal capillaries were tapped at an early stage of implantation. The fusion of chorions of twins and triplets first occurred around day 19 after ovulation.     

Plasmodium knowlesi in the marmoset (Callithrix jacchus).

Common marmosets were shown to be susceptible to Plasmodium knowlesi malaria. The morphology of the parasite was indistinguishable from the observed in the natural host (Macaca fascicularis) and the common laboratory model (Macaca mulatta). A differential susceptibility to P. knowlesi was observed in the 8 marmosets studied. Multiplication rates of parasites were variable over 24 h periods. Five animals died of a fulminating infection within 12--17 days after challenge. Three animals recovered spontaneously from infection and were subsequently resistant to challenge with homologous and heterologous variants and strains of P. knowlesi. This resistance was maintained for intervals up to 100 days between challenge infections.     

An experimental analysis of social interaction in the common marmoset (Callithrix jacchus jacchus)

Adult and juvenile common marmosets were introduced to unfamiliar conspecifics individually and in whole groups. In introductions using animals of the same sex, adults were mutually hostile unless they were related or socially familiar; juveniles behaved submissively to adults and little aggression was observed between juveniles. In introductions using animals of the opposite sex, males of all ages solicited females but females did not reciprocate. When whole groups were introduced, in two experiments most of the elder group members behaved aggressively and younger animals did not interact frequently; but in a third experiment, in which the adult males were related, little aggression was observed and younger animals behaved amicably. It is argued that the behavioral reactions shown by individual marmosets are related to territorial hostility and that the behavior of juveniles to adults may aid assimilation of younger animals into new groups.     

A restraint system for the common marmoset (Callithrix jacchus)

A method for restraining the marmoset in a primate chair is described. The device is inexpensive to construct, is reliable, and the majority of animals can be habituated to its use. The chair has been used in neurobiological studies employing electrophysiological recordings, with or without concurrent collection of serial blood samples.     

Patterns of prenatal survival in the common marmoset (Callithrix jacchus)

Abstract: Fifty common marmoset pregnancies were monitored using ultrasound. The objective was to ascertain if fetal mortality was related to litter size. Prior to analysis we determined abortion rate and litter size were not influenced by repeated ultrasound. Mortality was unrelated to litter size and occurred fairly late in gestation. All singletons born in this study began gestation as twins. It is hypothesized that marmosets may be able to adjust litter size late in pregnancy in response to proximate environmental factors.     

Lymphocyte subsets in the young and aging marmoset (Callithrix jacchus)

T lymphocytes were studied in healthy young and old marmosets (Callithrix jacchus). Data indicate that monoclonal antisera to human T lymphocyte antigens can be used to identify these cells in marmosets. Total T and suppressor T cells were lower in the older group; there were no differences in helper T or in B cells. Helper/suppressor ratios (T4/T8) were increased in the older group. Thus, immune system alternations with aging and/or immune deficiency syndromes may be studied in this animal model using available reagents.