1) General zoological data of species
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 one species will be dealt with here in some detail.
All lemurs are significantly endangered. 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 Research 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).
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.
2) General gestational data
In Madagascar (Malagasy Republic), lemurs mate from April to June and have a gestational length of about 4½ months (black lemurs 127 days; ring-tailed lemurs 136 days or less; ruffed lemurs 90-102 days). The ruffed lemurs (Varecia spp.) have been grouped with the genus Lemur in the past but now they are separated as comprising a different genus, Varecia. They are also somewhat heavier than most of the other species. The estrous cycle is 30 days in length in ring-tailed lemurs, with estrus around 6 days. Multiple offspring are much more common in ruffed lemurs, while singletons are the rule in ring-tailed lemurs. Longevity of ring-tailed lemurs is 19 years (Bogart et al., 1977).
The litter size varies appreciably, especially in ruffed lemurs where triplets and quadruplets occur. The weight of the placenta in ruffed lemur is around 20 g (perhaps incomplete) and the placenta has a diameter of 3.5 x 1.5 cm and is 1 cm in thickness. The newborns weigh around 80-90 g, while "cattas" (ring-tailed lemurs) weigh only 15-20 g at birth with a placenta of about 7-8 g.
|Black and white ruffed lemur (Varecia variegatus).|
Early embryonic/placental stages of these species have not been described. Mossman (1987), however, suggested that implantation occurs in an antimesometrial location. The final location of the diffuse lemur placenta is one throughout the bicornuate uterus.
|Delivered placenta of black and white ruffed lemur. At left is the cervical area (C).|
|Terminal villi of mature placenta from black and white ruffed lemur. Note the peripheralization of fetal capillaries beneath the single-layered trophoblast|
|Complete cross sections of mature placenta from black and white ruffed lemur.|
|The maternal myometrium.|
4) General characteristics of placenta
Lemurs have a diffuse, villous placenta that occupies the entire bicornuate uterus. The nidation is superficial (Mossman, 1987). Their placenta is epitheliochorial and it has a large allantoic sac. There is no invasive trophoblast.
5) Details of barrier structure
|Trophoblastic surface beneath the chorionic plate of lemur.|
6) Umbilical cord
The umbilical cord contains three blood vessels. In addition there is a large allantoic duct that connects the bladder with the allantoic sac. It is a short cord, about 10 cm in length and 0.3 cm in width. Cords may have some keratiniziation of the amnionic surface.
|Cross-section of mature lemur umbilical cord. Two arteries, one vein and a large allantoic duct.|
7) Uteroplacental circulation
There is no description of these features in the literature.
|Membranes with amnion at left. It exhibits some squamous metaplasia. The thin allantois is at right and its membrane carries the allantoic blood vessels. Numerous pigmented macrophages are present in these membranes.|
9) Trophoblast external to barrier
There is no extravillous trophoblast, and giant cells are not present. There is also no maternal vascular trophoblastic infiltration or invasion.
There is no decidualization of the endometrium. In postpartum uteri, hemosiderin granules are found in the endometrium.
Other data to be accumulated
K.: Pectus excavatum in ruffed lemurs (Lemur [Varecia] variegatus).
XXII Internatl. Symp. über die Erkrankungen der Zootiere. Arnhem,
Holland, May. Akademie-Verlag, Berlin, pp. 169-172, 1980.
Benirschke, K., Kumamoto, A.T. and Bogart, M.H.: Congenital anomalies in Lemur variegatus. J. Med. Primatol. 10:38-45, 1981.
K. and Miller, C.J.: Weights and neonatal growth of ring-tailed lemurs
(Lemur catta) and ruffed lemurs (Lemur variegatus). J. Zoo Anim.
Med. 12:107-111, 1981.
M.H., Cooper, R.W. and Benirschke, K.: Reproductive studies of Lemur m.
macaco, Lemur variegatus subcinctus and Lemur v. ruber.
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Gray, A.P.: Mammalian Hybrids. Second edition. A Check-List with Bibliography. Commonwealth Agricultural Bureaux, Farnham Royal, Slough, UK, 1972.
Hsu, T.C. and Benirschke, K.: An Atlas of Mammalian Chromosomes. Springer-Verlag, New York, 1975.
Mossman, H.W.: Vertebrate Fetal Membranes. MacMillan, Hound mills, 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.
Puschmann, W.: Zootierhaltung. Vol. 2 Säugetiere. VEB Deutscher Landwirtschaftsverlag, Berlin, 1989.
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.
|Ring-tailed lemur (Lemur catta).|
|Red ruffed lemur (Lemur/Varecia variegatus ruber).|
|Black lemur (Lemur macaco), male is black, female is pale.|
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