Reproduction and aging in marmosets and tamarins.

This chapter presents data on the relations between reproduction and aging in both captive and free-ranging marmosets and tamarins. The relationship is examined from two perspectives. First, the relation of age to physiological impairments in reproductive function is explored. Callitrichid females, in common with many other nonhuman primates, begin to display anovulation associated with follicular depletion at a point relatively close to the maximum life span. Unlike Old World primates, however, they continued to display significant steroidogenic activity in the ovary. There are age effects on some reproductive output variables, such as litter size and inter-birth interval, though the effects are often small. Like other mammals, male marmosets display a change in levels of androgens with age, although the magnitude of the decrease is not large and they actually mount an elevated response to GnRH challenge as they age. We also examined whether age affects either the establishment or maintenance of a breeding position, the factors most important in determining lifetime reproductive success. Infant mortality did increase with increasing parturitions, suggesting that there may have been aging or parturition effects on lactation. Generally, marmoset females were well past the age of sexual maturity at the beginning of the tenure and approaching 8-9 years at the end of it. Reproductive decline did not appear to be a gradual process, but a rather abrupt one, often causing the dismantling of the group. There are potentially interesting relations among maternal age, mass and declining reproductive performance, given the known importance of mass as a determinant of reproductive success in female callitrichids.

Reproductive output, maternal age, and survivorship in captive common marmoset females (Callithrix jacchus).

Common marmosets (Callithrix jacchus) demonstrate significant variation in reproductive output on both a yearly and lifetime basis in comparison to other anthropoid primates. We explore the factors that may be most important in determining reproductive variation in captive common marmosets. Studies have found that maternal age, maternal condition, and dam survivorship are related to reproductive output; however, these reports are not in agreement and are far from conclusive. With the use of a large, multicolony, demographic database pooling data across five marmoset colonies, we examined litter information for 1,649 litters, and reproductive summaries for 400 dams to assess 1) how reproductive output variation (total production, total weaned production) is determined by litter size, interbirth interval (IBI), age at first birth, and dam survival age; 2) the relationship between maternal age and reproductive output variables; and 3) relationship between the reproductive output variables and survival. We used stepwise regression procedures to describe the amount of variation in lifetime reproductive output among dams, and found that mean litter size accounted for 18% of the variance in total production, survival age accounted for 10.6%, age at first birth accounted for 8.8%, and mean IBI accounted for 5%. For total (nonzero) weaned production, survival age accounted for 7.6% of variance, age at first birth accounted for 7.2%, mean IBI accounted for 2%, and mean litter size accounted for 1.6%. We identified significant effects (P<0.05) of maternal age on litter size and IBI length, but no effect of dam age on weaned litter size. Cox proportional hazards regression analyses revealed significant effects (P<0.01) of number of litters, age at first birth, and site on dam survivorship. Dams that produced more litters showed higher survivorship. Age at first birth showed a positive relationship with dam survivorship, i.e., dams that delayed first reproduction had higher survival. Our findings about reproductive variation in marmosets may have practical applications for the management of marmoset breeding colonies.

Aspects of common marmoset basic biology and life history important for biomedical research.

While common marmosets are increasingly used as alternative primate models in biomedical research, their life history, specialized behavior and unique physiology are not well known. This paper describes important marmoset attributes that are particularly relevant for biomedical research, including reproduction, neurobiology, immunology, endocrine signaling, obesity and aging, in addition to fetal and postnatal development. While common marmosets exhibit characteristic anthropoid primate traits, they clearly differ from Old World primates and humans in a variety of functions, including reproduction, endocrine signaling and immunology. These differences, however, permit the use of common marmosets in unconventional research strategies targeted on human pathology.