white-faced Saki Monkey
Pithecia pithecia pithecia
Family: Cebidae (Pitheciidae)
1) General Zoological Data
Of the five species of saki monkeys now recognized by Nowak (1999), this species has the most northern distribution. See Hershkovitz, (1979, 1987) for recent taxonomic considerations. Saki is a Tupi Indian designation for this monkey (Gotch, 1979). The saki is one species of the large infraorder of Platyrrhini that has been divided by various molecular techniques into three genera, the Pitheciidae, Atelidae and Cebidae (Harada et al., 1995; Schneider et al., 2001). Steiper & Ruvolo (2003) added to the analysis of DNA sequences of the X-linked G6PD in these species. Adults weigh 700-1,700 (?2,500)g and have a life expectancy of 35 years (Nowak, 1999). Single young are born after a gestation of 163-176 days (Eisenberg, 1989). Sakis are not endangered now and are only occasionally seen in zoos. They are well-known, however, for their leaping ability in the forests. There is a significant facial difference in the sexes.
Rosenberger (1992) suggested that sakis depend primarily on seeds for their protein needs, a fact supported by the experiments and descriptions of Brumloop et al. (1994). They are also known to consume small mammals (bats) and birds.
General Gestational Data
The length of gestation is described as being 163-176 days (Eisenberg, 1989) and produces a single quite mature young. Twins have not been described.
General Characterization of the Placenta
Details of fetal/maternal barrier
The villous tissue is quite uniform and different from that of Callithricidae. It is somewhat trabecular and mostly villous. Long connecting strands of connective tissue extend from the chorion to the floor of the placenta. Villi are typical of primates, with a diffuse syncytial cover, few syncytial giant cells in the intervillous space, prominent villous cytotrophoblast beneath the syncytium, and a few islands of extravillous trophoblast. The latter and some of the fibrinoid material have small foci of calcification, especially at the placental floor. In contrast to marmosets and tamarins, there is no extramedullary hematopoiesis in the villi. The villous connective tissue is very sparse and only very rare Hofbauer cells are present.
The placental floor has rather thick layers of fibrin and fibrinoid with mild infiltration of cytotrophoblast, but it does not extend deeply into the decidua basalis.
There is virtually no infiltration of trophoblast into the maternal vasculature.
The umbilical cord was 14 cm long and 0.3 cm wide. It inserted near the margin and had no spirals. The umbilical cord possesses four large blood vessels, two arteries and two veins, but no small vessels. In addition, the cord has a large allantoic duct, similar to that of the spider monkey (Miller & Benirschke, 1985). There is no surface squamous metaplasia. In general, the findings are extremely similar to those of the spider monkey (see chapter on Ateles), except for the apparent lack of an allantoic sac.
No studies have been conducted but there is virtually no modification of the maternal spiral arterioles by invasive trophoblast.
Trophoblast external to barrier
There is superficial infiltration of the basal endometrium by extravillous trophoblast, but without giant cell formation. Very sparse vascular infiltration occurs, unlike that found in the spider monkey; there one finds much more trophoblastic infiltration (see chapter on Ateles).
I am not aware of any studies.
Other remarks - What additional Information is needed?
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