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Red deer (Cervus elaphus barbarus). | |
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Brocket deer (Mazama sp.). | |
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White-tailed deer (Odocoileus virginianus). |
3) Implantation The deer placenta is "oligocotyledonary", with maximally 10 cotyledons. Most of their placentas possess only 4-6 cotyledons. This contrasts with cow, sheep, and other ruminants, which have up to ten times that many cotyledons. Moreover, the shape of cotyledons varies somewhat in ruminants. Most deer species have convex cotyledonary shapes (see Mossman, 1987). This contrasts with the goat, for instance that have a concave cotyledonary structure (Please see the chapter on Cretan goat). The early attachment of deer blastocysts is mesometrial and it is confined to the uterine caruncles. These are usually in mesometrial rows. In between the cotyledons is the allantochorionic membrane that is covered by villus-free trophoblast. This area is the site of the areolae, modifications of endometrium with focal endometrial secretion and absorption of nutrients (uterine milk) by the trophoblast. Most cervid placentas have their umbilical cords attached to the chorion at the mesometrial aspect of the uterus. All have a large allantoic sac, but the yolk sac is transitory. Chapman and Dansie (1969) studied implantation in feral Chinese muntjac that had escaped in England. They found that the majority of their fetus are in the right uterine horn. That is not the case in all cervids. |
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General situs of deer placentas. |
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Bicornuate uterus pregnant with twins of white-tailed deer (Odocoileus virginianus). | |
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Bicornuate uterus pregnant with twins of white-tailed deer (Odocoileus virginianus). | |
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Twin gestation in white-tailed deer, in December (New Hampshire). Note three cotyledons per animal of approximately equal size in different uterine horns. | |
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Composite of the same white-tailed deer specimen, injected with green dye. Note the intimate fusion of the cotyledons and chorions, but an absence of anastomoses between the twin circulations. At top right is a complete "placentome". | |
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For a larger image of the composite above, click this thumbnail. | |
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For a larger image of the composite above, click this thumbnail. | |
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For a larger image of the composite above, click this thumbnail. | |
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For a larger image of the composite above, click this thumbnail. |
The placental development of the red deer, Cervus elaphus, was described by McMahon et al. (1997). Twelve uteri were studied between 27 and 55 days of gestation. Gastrulation was complete by 27 days and the trophoblast had covered both uterine horns. Trophoblastic "plaques" were seen by day 34 and, by day 41, the placentomes had formed. Placentation was otherwise deemed to be similar to that of other ruminants. Hamilton et al. (1960) had 15 such uteri and found four cotyledons in each uterine horn. | |
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Placenta of Barbary red deer, Cervus elaphus barbarus. | |
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Placenta of Barbary red deer, Cervus elaphus barbarus. | |
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Placenta of singleton wapiti, Cervus elaphus, with 8 cotyledons, 4 in each horn. | |
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Placenta of singleton Père David's deer neonate, Elaphurus davidianus. As discussed next, there are five large cotyledons with flat, ovoid shape and a relatively long cord. | |
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Placenta of singleton Père David's deer neonate, Elaphurus davidianus. As discussed next, there are five large cotyledons with flat, ovoid shape and a relatively long cord. |
The placenta of the Père David's deer, Elaphurus davidianus, has been studied by Harrison & Hamilton (1952). They had four specimens of pregnant uteri at their disposal. They found three elongated caruncles in the right uterine horn and two in the left horn of two non-pregnant animals. The placentomes of this deer species are the largest observed to date. They are more flat than those of other cervids with their more convex placentomes. Harrison & Hamilton found that the fetuses were present in the right horn, but the left horn was equally enlarged. There were five placentomes (cotyledon + caruncle), mostly situated on the posterior wall of the uterus, and on the septum. They also observed large allantoic sacs and the usual excrescences of the amnion, representing squamous metaplasia. The umbilical cords measured 10-12 x 2-3 cm in length and width, and contained two arteries, two veins and the allantoic duct. A number of minute vessels were also present in the cords, interpreted to supply the mesenchyme of the cord. The general structure of the cotyledon was essentially similar to that found in the white-tailed deer described above, except that they were larger. These authors estimated the number of villi per placentome to be 10,000 - 12,000 stem villi, and 46,000 - 47,000 secondary villi. They also referred to the ease with which cotyledons can be peeled away from the caruncles. In contrast to the usual findings on the surface of human placentas where arteries pass over the veins, in cervid specimens both modes occur with equal frequency. The investigators observed the numerous giant cells with two nuclei and their "discrete large and small granules", lack of brush border and the presence of intraepithelial fetal capillaries. The endometrial surface epithelium lacked such capillaries. There is a detailed consideration also of the complexity of the fetal and maternal vasculatures. Finally, they observed that the free chorionic membrane is always covered by a single layer of trophoblast, is never villous, and is in contact with the endometrium; areolae were also described, similar to those of the white-tailed deer. I have had two full term placentas of an Elaphurus davidianus for study. The stillborn fetus of the last specimen weighed 15 kg. The placenta weighed 450 g, had 5 cotyledons and measured 16-17 x 14.5-6.5 x 1-0.8 cm. The umbilical cord was 20 cm long, 2 cm in diameter, and it had no twists. It contained 4 vessels and the allantoic duct. Additional information is shown in the table below. The placentation of the roe deer, Capreolus capreolus, has not been studied recently. Hamilton et al. (1960) described the placentas of 22 pregnant uterine specimens. There were twins in 84%, of which they believed that at least 7.7% were monozygotic. Interestingly, although all twins had the same sex, no circulatory anastomoses were found. The usual number of placentomes was eight, four in each horn. Aitken et al. (1973) studied the blastocyst and endometrium in the diapause of delayed implantation. Aitken (1975) later expanded these electronmicroscopic studies on blastocysts. This is of interest, of course, because roe deer have a delayed implantation of about 5 months. The blastocysts lose their zona pellucida and remain in the uterus for 5 months before implanting on the caruncular ridges to form the basis for their cotyledonary placenta. Prior to implantation, there is much embryonic growth. The trophoblastic surface of the blastocysts was covered with microvilli but the cytoplasm of the trophectoderm was strikingly devoid of organelles, other than containing some mitochondria. Later, the blastocysts became elongated and, when there was more embryonic development, many more organelles became evident in the trophoblast, including granules and lipid. The elongation of the blastocyst was interpreted as being due to endometrial secretions. The endometrium had a glandular structure except for four aglandular "caruncular ridges". Surprisingly, no major changes took place in the structure of the corpora lutea during the diapause. Because much increased estrogen secretion occurred during this time, one might have expected morphologic differences to account for this endocrine change. So far, the presumed endocrine signal for implantation has remained elusive. Hamilton et al. (1960) made an exhaustive effort to describe the anatomy of the fallow deer, Dama dama, having over 200 pregnant uteri at their disposal. In addition, they dissected a variety of other pregnant deer, some results of which are summarized at the end of the table below. Furthermore, they did histology, electronmicroscopy of all structures and they displayed their findings of color-injected cotyledons in superior photographs. I encountered no additional new findings of placentation in cervids. It is perhaps important to mention though that these authors divided the cotyledons into three zones: The subchorionic comprising 1/5 of villi, was referred to as the "storage zone"; next comes an even narrower "zone of attrition"; the bulk (towards the uterine wall) was made up of the "zone for physiologic exchange". These areas have been depicted in a photograph below. It is true, however, that Mossman (1987) took exception to these terms. He indicated that in the "storage zone" (A in the photo) there accumulates glycogen with advancing gestation. This region, as he pointed out, is the area of atrophy of maternal crypts with columnar cytotrophoblast, an area more like a syndesmochorial region. Hamilton et al. (1960) also drew attention to intraepithelial capillaries (in the trophoblastic surface -see photo below). Because of the very unusual features identified in the placentation of the Chinese Tufted Deer (Elaphodus cephalophus) a separate chapter is available on that species (see Tufted deer). The placenta of an Eld's deer (Cervus eldii) weighed 550 g and had 5 large, flat cotyledons. Its umbilical cord measured approximately 15 cm in length. |
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Tip of villus of delivered placenta from wapiti to show the intraepithelial capillaries in the trophoblast layer. | |
The
placenta of a Javan rusa deer (Cervus timorensis) became available
during the extraction of a female neonate with dystocia. The placenta had
3 very large cotyledons (15 x 13 cm) and weighed 750 g with all appendages.
Its cord was 17 cm long and 2 cm in width. Its surface and that of the amnion
had a remarkable degree of keratin formation (Squamous metaplasia). The
stillborn female fetus (7,500 g) had large cystic ovaries and a bicornuate
uterus which contained one small and 2 large caruncles in each horn. Although Hamilton et al. (1960) did not find hematomas, as other authors had, I can confirm that hemosiderin, representing the remains of hematomas, is frequent at the margin of cotyledons. There is early necrosis when the centers of the caruncles develop. |
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Weights,
Number of Cotyledons, and Cord Lengths
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(Personal observations from delivered placentas. (above)
(Preceding data are from Hamilton et al., 1960) |
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Structure of one-half placentome (Eld's deer). Fetus. | |
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Structure
of one-half placentome (Eld's deer). Uterus. (F.V.=
Fetal vessel; F.C.= Fetal connective tissue of villi; |
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Structure
of one-half placentome (Eld's deer). Uterus. (F.V.=
Fetal vessel; F.C.= Fetal connective tissue of villi; |
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Structure
of one-half placentome (Eld's deer). Uterus. (F.V.=
Fetal vessel; F.C.= Fetal connective tissue of villi; |
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5) Details of barrier structure All cervidae have an epitheliochorial, cotyledonary placenta whose size varies with the size of the animal and offspring. In general, the number of cotyledons is very small in cervids when compared to other ruminants. Because of the apparent fusion of the binucleate trophoblastic cells with some endometrial epithelium, the barrier is now often referred to as being "synepitheliochorial". The trophoblast is cuboidal to columnar and differs in fine structural morphology between the cotyledonary regions and that of the intercotyledonary membranes (see above, Sinha et al., 1969). The fusion of diplokaryocytes with endometrium has also been referred to above. |
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This
is a cross section of the villous tissue of a cotyledon in an Eld's deer
(Cervus eldi). Note the widely scattered capillaries in the very
loose connective tissue of villi. T=trophoblast; M=maternal tissue (caruncle). |
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Fetal/maternal apposition at the bottom of the caruncle crypt in an Eld's deer (Cervus eldi). These show the tip of a villus (left and bottom right), interdigitating with the caruncle. The diplokaryocytes/giant cells are readily identified. Note the very loosely constructed villous cores in which fetal capillaries are widely dispersed. | |
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Tips
of villi at implantation site, interdigitating with caruncular clefts. Note
the large number of giant cells and mitoses. E=endometrium; F=fetal villous connective tissue; T=trophoblast. (Cervus eldi). |
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Tips
of villi at implantation site, interdigitating with caruncular clefts. Note
the large number of giant cells and mitoses. E=endometrium; F=fetal villous connective tissue; T=trophoblast. (Cervus eldi). |
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Margin of cotyledon with endometrial glands next to cotyledon. There is much hemosiderin in the superficial endometrium. (Eld's deer). | |
6) Umbilical cord The white-tailed deer has two arteries, two veins and an allantoic duct (Sinha et al., 1969). This is true of the other deer species that I have examined and for what studies have been detailed in publications. Arteries and veins branch, in parallel, to supply the cotyledons. Harrison & Hamilton (1952) found the same to be true in Père David's deer. There are no good descriptions of the lengths of umbilical cords, other than for what is compiled in the table above from a few delivered placentas. They may be longer in utero, but that apparently has not been measured. Spiral turns are not observed, and there are relatively fewer small blood vessels than what has been observed in some other taxa, dolphins for instance. Some are clearly derived from the major cord vessels. |
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Portion of umbilical cord of reindeer (Rangifer tarandus). A.D.=allantoic duct. Note the large number of scattered small blood vessels, mostly around allantois. | |
10)
Endometrium 11)
Various features |
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The two muntjac species ("barking deer") with their marked difference in chromosome number but only slight phenotypic variation. (After Grzimek). | |
The chromosome number of cervidae is variable. The usually high chromosomal number in many deer species (around 2n=70) presumably reflects their closer relationships, while a few "outliers" are also somewhat removed from the mainstream of cervidae (see Yang et al, 1997). We have established the following chromosome numbers: Moose (70); Axis deer - chital (66); Hog deer (68); Roe deer (70); Barasingha deer (56); Red deer (68); Sambar deer 60; 64-65); Fallow deer - Dama (68); Père David's deer (68); Chinese water deer (Hydropotes inernis) (70); Red brocket deer (Mazama) (50); Reindeer (70); Pudu (70); White-tailed deer (70); Mule deer (70); Chinese muntjac (46); Indian muntjac (6/7) [see Hsu & Benirschke]. Since then, numerous chromosomal banding studies have been done on some of these species and additional species have also been studied: Tufted deer (Elaphodus cephalophus) 2n=46-48 (Shi et al., 1991); white-lipped deer (Cervus albirostris Przewalski) 2n=66 (Wang et al., 1982), and several other muntjacs. Eld's deer (Cervus eldi) has 2n=58 (Neitzel, 1979, she also lists another group of deer species). Sika deer (Cervus nippon hortulorum Swinhoe) has 2n=64-68 (Gustavsson & Sundt, 1969). Another complete listing may be found in Groves & Grubb (1987). Evolutionary relationships have been discussed at the beginning of this chapter. Modern studies are beginning to provide further insight into disputed areas. Thus, the mtDNA of muntjacs was explored by Lan & Shi (1993). Repetitive DNA of cervids was used for evolutionary questions by Bogenberger et al. (1987). Chromosome "painting" led to a better understanding of muntjac chromosomal fusions (Yang et al., 1995). mtDNA was used in studying hybrids between mule and white-tailed deer (Carr et al, 1986), and so forth. Genetic heterozygosity positively influenced fetal size and growth in white-tailed deer, while number of fetuses correlated negatively (Cothran et al., 1983). 14) Immunology Lymphocytic infiltration of the uterine mucosa/epithelium is a frequent, if not regular, feature of ruminant uteri. Lee et al. (1995) studied this in six species of deer. They found a significant cellular increase to occur from early implantation to mid-gestation. They observed also that the size of granules of these cells varies greatly and that they increase with gestation. The investigators observed that these lymphocytes tend to be close to regions where the trophoblastic binucleated cells fuse with the endometrial epithelium. Here they produce the trinucleate cells and give up their granules. The precise reason for these changes remains unknown but "immune recognition" is suspected.. 15)
Pathological features 17)
Other resources
18) Other relevant features and information needed in future
Aitken, R.J., Burton, J., Hawkins, J., Kerr-Wilson, R., Short, R.V. and Steven, D.H.: Histological and ultrastructural changes in the blastocyst and reproductive tract of the roe deer, Capreolus capreolus, during delayed implantation. J. Reprod. Fertile. 34:481-493, 1973. Anderson, R.C.: The development of Pneumostrongylus tenuis in the central nervous system of white-tailed deer. Path. Vet. 2:360-379, 1965. Bogenberger, J.M., Neitzel, H. and Fittler, F.: A highly repetitive DNA component common to all Cervidae: its organization and chromosomal distribution during evolution. Chromosoma 95:154-161, 1987. Carr, S.M., Ballinger, S.W., Derr, J.N., Blankenship, L.H. and Bickham, J.W.: Mitochondrial DNA analysis of hybridization between sympatric white-tailed deer and mule deer in west Texas. Proc. Natl. Acad. Sci. USA 83:9576-9580, 1986. Cell lines are available from CRES at the San Diego Zoo under: www.sandiegozoo.org Chapman, D.I. and Dansie, O.: Unilateral implantation in the muntjac deer. J. Zool. Lond. 159:534-536, 1969. Christian, J.J., Flyger, V. and Davis, D.E.: Factors in the mass mortality of a herd of sika deer, Cervus nippon. Chesapeake Sci. 1:79-95, 1960. Cothran, E.G., Chesser, R.K., Smith, M.H. and Johns, P.E.: Influences of genetic variability and maternal factors on fetal growth in white-tailed deer. Evolution 37:282-291, 1983. Cowan, I.M. and Johnston, P.A.: Blood serum protein variations at the species and subspecies level in deer of the genus Odocoileus. Systematic Zool. 11:131-138, 1962. Dubey, J.P.: Isolation of encysted Toxoplasma gondii from muscles of mule deer in Montana. JAMA 181:1535, 1982. Ebel, G.D., Campbell, E.N., Goethert, H.K., Spielman, A. and Telford, S.R.: Enzootic transmission of deer tick virus in New England and Wisconsin sites. Amer. J. Trop. Med. Hyg. 63:36-42, 2000. Fletcher, T.J.: Deer: New domestic farm animals defined by controlled breeding. In press, 2001. Gadsby, J.E., Heap, R.B. and Burton, R.D.: Oestrogen production by blastocyst and early embryonic tissue of various species. J. Reprod. Fertil. 60:409-417, 1980. Gray, A.P.: Mammalian Hybrids. Second edition. A Check-List with Bibliography. Commonwealth Agricultural Bureaux, Farnham Royal, Slough, UK, 1972. Griner, L.A.: Pathology of Zoo Animals. Zoological Society of San Diego, 1983. Groves,
C.P. and Grubb, P.: Relationships of living deer. In, Biology and Management
of the Cervidae. C.M. Wemmer, ed. Smithsonian Inst. Press, Washington,
1987, pp. 21-59. Hamilton, W.J., Harrison, R.J. and Young, B.A.: Aspects of placentation in certain Cervidae. J. Anatomy 94:1-33, 1960. Harrison, R.J. and Hamilton, W.J.: The reproductive tract and the placenta and membranes of Père David's deer (Elaphurus davidianus Milne Edwards). J. Anat. 86:203-224, 1952. Hsu, T.C. and Benirschke, K.: An Atlas of Mammalian Chromosomes. Springer-Verlag, New York, 1975. Huang, F., Cockrell, D.C., Stephenson, T.R., Noyes, J.H. and Sasser, R.G.: Isolation, purification, and characterization of pregnancy-specific protein B from elk and moose placenta. Biol. Reprod. 61:1056-1061, 1999. Hudson, P. and Browman, L.G.: Embryonic and fetal development of the mule deer. J. Wildlife Manag. 23:295-304, 1959. Kitchen, H., Putnam, F.W. and Taylor, W.J.: Hemoglobin polymorphism: Its relation to sickling of erythrocytes in white-tailed deer. Science 144:1237-1239, 1964. Kurnosov, K.M.: Interfetal placental connections of the elk in embryonic parabiosis. Proc. Akad. Nauk. SSR Doklady, Biol. Sect. 142:92-94, 1962 (in English). Lan, H. and Shi, L.: Restricted endonuclease analysis of mitochondrial DNA of muntjac and related deer. In, Deer of China, N. Ohtaishi and H.-I. Sheng, eds. Elsevier Science Publ., 1993. Lawn, A.M., Chiquoine, A.D. and Amoroso, E.C.: The development of the placenta in the sheep and goat: an electronmicroscope study. J. Anat. 105:557-578, 1969. Lee, C.S., Gogolin-Ewens, K. and Brandon, M.R.: Comparative studies on the distribution of binucleate cells in the placentae of the deer and cow using monoclonal antibody, SBU-3. J. Anat. 147:163-179, 1986. Lee, C.S., Wooding, F.B. and Morgan, G.: Quantitative analysis of intraepithelial large granular lymphocyte distribution and maternofetal cellular interactions in the synepithelichorial placenta of the deer. J. Anat. 187:445-460, 1995. McMahon, C.D., Fisher, M.W., Mockett, B.G. and Littlejohn, R.P.: Embryo development and placentome formation during early pregnancy in red deer. Reprod. Fertil. Dev. 9:723-730, 1997. Mansell, W.D. and Cringan, A.T.: A further instance of fetal atrophy in white-tailed deer. Canad. J. Zool. 46:33-34, 1968. Miyamoto, M.M., Kraus, F. and Ryder, O.A.: Phylogeny and evolution of antlered deer determined from mitochondrial DNA sequences. Proc. Natl. Acad. Sci. USA 87:6127-6131, 1990. Mossman, H.W.: Vertebrate Fetal Membranes. MacMillan, Houndmills, 1987. Naik, S.N., Bhatia, H.M., Baxi, A.J. and Naik, P.V.: Hematological study of Indian spotted deer (Axis deer). J. Exper. Zool. 155:231-236, 1964. Neitzel, H.: Chromosomenevolution in der Familie der Hirsche (Cervidae). Bongo 3:27-38, 1979. Nowak, R.M. and Paradiso, J.L.: Walker's Mammals of the World, Vol. II. 4th edition. The Johns Hopkins University Press, Baltimore, 1983. Plotka, E.D.: Deer. In, Encyclopedia of Reproduction. E. Knobil and J.D. Neill, eds. Academic Press, San Diego 1998, Vol. I, pp.842-857. Pritchard, W.R., Malewitz, T.D. and Kitchen, H.: Studies on the mechanism of sickling of deer erythrocytes. Exp. Molec. Pathol. 2:173-182, 1963. Puschmann, W.: Zootierhaltung. Vol. 2, Säugetiere. VEB Deutscher Landwirtschaftsverlag, Berlin, 1989. Randi, E., Mucci, N., Claro-Hergueta, F., Bonnet, A. and Douzery, E.J.P.: A mitochondrial DNA control region phylogeny of the Cervinae: speciation in Cervus and implications for conservation. Animal Conserv. 4:1-11, 2001. Ratcliffe: Environment, behavior and disease: Observations and experiments at the Philadelphia Zoological Garden. Trans. & Studies Coll. Physic. Philadelphia 36:7-21, 1968. Saunders, J.K.: Fetus in yearling cow elk, Cervus canadensis. J. Mammal. 36:145, 1955. Schaeffler, W.F.: Serologic tests for Theileria cervi in white-tailed deer and for other species of Theileria in cattle and sheep. Amer. J. Vet. Res. 24:784-791, 1963. Shi, L., Ye, Y., Duax, X.: Comparative cytogenetic studies on the red muntjac, Chinese muntjac, and their F1 hybrids. Cytogenet. Cell Genet. 26:22-27, 1980. Shi, L. and Pathak, S.: Gametogenesis in a male Indian muntjac x Chinese muntjac hybrid. Cytogenet. Cell Genet. 30:152-156, 1981. Shi, L., Yang, F. and Kumamoto, A.: The chromosomes of tufted deer (Elaphodus cephalophus) Cytogenet. Cell. Genet. 56:189-192, 1991. Sinha, A.A., Seal, U.S., Erickson, A.W. and Mossman, H.W.: Morphogenesis of the fetal membranes of the white-tailed deer. Amer. J. Anat. 126:201-242, 1969. Sinha, A.A., Seal, U.S., Erickson, A.W.: Ultrastructure of the amnion and amniotic plaques of the white-tailed deer. Amer. J. Anat. 127:369-396, 1970. Taylor, D.O.N., Thomas, J.W. and Marburger, R.G.: Abnormal antler growth associated with hypogonadism in white-tailed deer in Texas. Amer. J. Vet. Res. 25:179-185, 1964. Undritz, E., Betke, K. and Lehmann, H.: Sickling phenomenon in deer. Nature 187:333-334, 1960. Vrba, E.S. and Schaller, G.B., eds.: Antelopes, Deer, and Relatives. Fossil Record, Behavioral Ecology, Systematics, and Conservation. Yale University Press, New Haven, 2000. Wang, Z., Du, D.R., Xu, J. and Che, Q.: Karyotype, C-banding and G-banding patterns of white-lipped deer (Cervus albirostris Przewalski). Acta Zool. Sin. 28:250-255, 1982.(in Chinese). Weldon, W.F.R.: Note on placentation of Tetraceros quadricornis. Proc. Zool. Soc. London pp.2-4, 1884. (Cited by Mossman, 1987). Wooding, F.B.: The role of the binucleate cell in ruminant placental structure. J. Reprod. Fertil. Suppl. 31:31-39, 1982. Wooding, F.B.: Frequency and localization of binucleate cells in the placentomes of ruminants. Placenta 4:527-539, 1983. Wooding, F.B., Morgan, G. and Adam, C.L.: Structure and function in the ruminant synepitheliochorial placenta: central role of the trophoblast binucleate cell in deer. Microsc. Res. Tech. 38:88-99, 1997. Wurster,
D.H. and Benirschke, K.: Chromosome studies in some deer, the springbok,
and the pronghorn, with notes on placentation in deer. Cytologia 32:273-285,
1967. Yang,
E., O'Brien, P.C.M., Wienberg, J., Neitzel, H., Kin, C.C. and Ferguson-Smith,
M.A.: Chromosomal evolution of the Chinese muntjac (Muntjacus reevesi).
Chromosoma 106:37-43, 1997. |
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