Unrearable litters and prenatal reduction of litter size in the common marmoset (Callithrix jacchus)

Abstract

It is widely believed that common marmosets (Callithrx jacchus) typically give birth to twins under natural conditions. In captivity, however, births of triplets or even larger litters are common, although parents rarely succeed in rearing more than two offspring. The traditional interpretation is that captive conditions, notably the ready availability of food, have led to increased reproductive output, perhaps involving a higher ovulation rate. The present paper provides evidence, combined from ultrasound examinations between ovulation and birth and hysterotomies conducted during the late embryonic and early fetal phase, that the litter size can be progressively reduced during pregnancy without spontaneous abortion. There is an unusually long lag phase prior to the onset of embryonic growth in common marmosets; the fetal stage does not begin until day 80 of the 144-day pregnancy. Reduction in litter size occurs during embryonic stages (up to day 80), and continues into the fetal stages. These results indicate that the common marmoset is adapted for flexible modification of litter size between ovulation and birth. The high incidence of triplet births in captive colonies may therefore be an expression of an adapted natural developmental process under artificial circumstances.

Perinatal germ cell development and differentiation in the male marmoset (Callithrix jacchus): similarities with the human and differences from the rat

“…Gestation in the marmoset lasts for 144 days (Windle et al ., 1999). The gestation of pregnant females was assessed by systematic palpation and/or ultrasound.…”

Monitoring reproduction in Callitrichidae by means of ultrasonography

“…13,15 The occurrence of an extended lag phase was subsequently confirmed by ultrasonographic monitoring of 8 individual pregnancies from ovulation to birth 9 and by analysis of a larger data set for embryonic/fetal development. 16 For Callithrix jacchus, at least, an extended lag phase at the beginning of pregnancy provides an explanation for the apparent paradox that females can conceive again shortly after birth despite the heavy demands of lactation, by postponing the main period of prenatal development and growth until weaning of the last offspring.…”

Efficient Embryo Transfer in the Common Marmoset Monkey (Callithrix jacchus) with a Reduced Transfer Volume: A Non-Surgical Approach with Cryopreserved Late-Stage Embryos1

“…As a result, the birth rate was significantly higher in the latter than in the former, although the analysis was applied to a small number of samples and must, therefore, be interpreted cautiously. Ovulation numbers of the common marmoset are two or more [1][2][3], but litter sizes may be reduced during pregnancy [15,16], most likely in response to proximate environmental factors. As a consequence, marmosets in captivity can deliver from one to four offspring per litter, with two being the most common.…”