1) General Zoological Data
There are numerous lemur species, all from Madagascar (Malagasy Republic) or from the Comoro Islands. They vary greatly in appearance but the surviving species vary only slightly in size. Many species have become extinct in the recent past (Ziswiler, 1967). I have had experience with ruffed lemurs, (Varecia spp.), ring-tailed lemurs (Lemur catta), and with black lemurs (Lemur macaco). Their placentation is generally similar and for that reason only the ring-tailed lemur species will be dealt with here in some detail. (See also the chapter on "Ruffed Lemurs" and “Brown lemur”.)
All lemurs are significantly endangered now. This is one reason why so many breeding colonies exist in zoos of various countries. Most notably, lemurs are well represented in the Vincennes Zoo of Paris and at the Primate Center of Duke University, Durham, North Carolina. There are some exceptionally rare species at those locations. The management of lemurs in captivity has been aptly discussed by Puschmann (1989). Longevity of ring-tailed lemurs is 19 years (Bogart et al., 1977).
The body weight of lemurs is around 2,000 g; they have long tails and thick fur. Lemurs are mostly arboreal forest dwellers (Nowak & Paradiso, 1983) and most are primarily diurnally active; a few other species not discussed here are more nocturnal. They often occur in sizeable groups and are largely vegetarian. There is an abundant literature on these well-studied prosimians.
General Gestational Data
Ring-tailed lemurs have a gestation of 136 days or less. Singletons are the rule but dizygotic twins are also common (Pasztor & van Horn, 1976; Benirschke & Miller, 1981). The latter publication also details the growth increments of a hand-raised ring-tailed lemur. Ring-tailed lemurs have an estrous cycle of 30 day, with estrus being around 6 days. The weight of newborn ring-tailed lemurs is only 25-50 g.
General Characterization of the Placenta
Details of fetal/maternal barrier
This placenta, like that of other lemurs, is typically epithelio-chorial with villi merely approximating the uterine epithelium. They are superficially attached to the undamaged uterine epithelium. The trophoblastic surface of villi is underlain by a dense capillary network and the capillaries often indent the very thin trophoblastic epithelium. Numerous macrophages (Hofbauer cells) and occasional leukocytes are found in the villous stroma.
The umbilical cords of lemurs are short, but none of these was measured. That of the last specimen was extremely short and had the usual three blood vessels. There were no spirals. Its surface was covered with thin amnionic epithelium. A widely patent allantoic duct was found in all specimens.
Trophoblast external to barrier
There is no invasion of the endometrium.
I know of no studies that relate to immunological investigations.
Other remarks - What additional Information is needed?
Benirschke, K. and Miller, C.J.: Anatomical and functional differences in the placenta of primates. Biol. Reprod. 26:29-53, 1982.
M.H., Cooper, R.W. and Benirschke, K.: Reproductive studies of Lemur
m. macaco, Lemur variegatus subcinctus and Lemur v. ruber.
Internat. Zoo Yrbk. 17:177-182, 1977.
Griner, L.A.: Pathology of Zoo Animals. Zoological Society of San Diego, San Diego, California, 1983.
Hsu, T.C. and Benirschke, K.: An Atlas of Mammalian Chromosomes. Volume 4: Folio 194. Springer-Verlag, New York, 1970.
Mossman, H.W.: Vertebrate Fetal Membranes. MacMillan, Houndmills, UK, 1987.
Nowak, R.M. and Paradiso, J.L.: Walker's Mammals of the World, Vol. II. 4th edition. The Johns Hopkins University Press, 1983.
Pasztor, L.M. and van Horn, R.N.: Twinning in prosimians. J. Human Evol. 5:333-337, 1976.
Puschmann, W.: Zootierhaltung. Vol. 2 Säugetiere. VEB Deutscher Landwirtschaftsverlag, Berlin, 1989.
Shideler, S.E., Czekala, N.M., Benirschke, K. and Lasley, B.L.: Urinary estrogens during pregnancy of the ruffed lemur (Lemur variegatus). Biol. Reprod. 28:963-969, 1983.
Ziswiler, V.: Extinct and Vanishing Animals. Springer-Verlag, New York, 1967.
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