1) General Zoological Data
There are three species in the genus Hippotragus: H. leucophaeus (the blue buck - now extinct since 1800), H. equinus (the roan antelope), and H. niger (the sable antelope). Several subspecies have been described of sable and of roan antelopes (H. equinus). H. n. variani is the rare giant sable antelope (Nowak, 1999). other subspecies have been described by Groves (1983). The name derives from hippos (Greek - horse) and tragos (male goat). H.F. Varian described the giant sable of Angola (H. n. variani) in 1913 (Gotch, 1979). Indeed, Blaine (1922) considered the Angolan subspecies to be sufficiently different as to assign it species rank. The "blue buck ("Blaubock") found detailed description in the monograph by Erna Mohr (1967).
Sable antelopes are said to "share a close evolutionary relationship and together form a sister clade to the more primitive Caprinae" (Matthee & Davis, 2001). Hassanin & Douzery (1999) suggested that they arose during one of the two major explosive radiatio ns occurring between 12 and 15.3 MYA.
Jones (1993) lists longevity for two sable antelope subspecies (12-22years), with the South African animal (H. n. niger) having the record of 22 years and 3 months. This is currently not the case. Wilson & Hirst (1977) presented a detailed monograph on ecology of South African Roan and Sable antelopes. (See also the chapter on Roan antelope).
General Gestational Data
The length of gestation is reported to be 268-280 days in roan antelopes and 240-281 in sables (Nowak, 1999; Mentis, 1972). Single offspring are the norm. Neonates weigh 16 kg (Ferrell et al., 2001). The attached placenta shown in this chapter comes from a gestation that ended in maternal death. The male fetus weighed 1,125 g and had a 30 cm CR length. The breeding behavior of sable antelope has been described in detail by Buechner et al. (1974).
No specific data on early implantation have been published. Mossman & Mossman (1969) examined 58 pregnant uteri and all were implanted in the right uterine horn, irrespective of ovulation site (27 right/28 left). They likened it to the situation existing in Adenota kob. The sex ratio was 1:1. Moreover, when they examined 9 virgin uteri, the right uterine horn was longer than the left.
4) General Characterization of the Placenta
This is a polycotyledonary placenta with epitheliochorial relationship. Hradecky (1983) found one sable antelope placenta to have 185 cotyledons measuring 3x2 cm, and another with only 109 cotyledons, arranged in six rows. The first placenta we examined had nearly 100 oval cotyledons. Another one had 50+ cotyledons and weighed 820 g. The nature of the sable antelope cotyledon was described by Hradecky et al. (1988a) as composed of villi 4 mm long. The maternal septa were relatively thick and "did not fully match the shapes of the contained villi" (there was more infolding of villous surfaces).
Details of fetal/maternal barrier
The trophoblast is cuboidal with microvillous surface and closely applied to the endometrial epithelium of the crypts which also have a microvillous surface. There is the usual number of typical, large binucleate trophoblastic cells, probably also engaged in the production of placental lactogen, as is the case in other ungulates. The villous connective tissue stroma is delicate and contains a small number of macrophages (Hofbauer cells). The villi are sparsely branched. Beneath the chorionic plate and in between cotyledons, the trophoblast is much more cylindrical but in none of my specimens contains any pigment. Moreover, none of the specimens had degeneration of the septal tips or hemorrhages.
The umbilical cord has four large blood vessels, an allantoic duct and a moderate number of small vessels. Its surface is remarkable because of the numerous "callosities", areas of squamous metaplasia with rather marked keratin production. It is less than 20 cm long but good measurements have not been available. There are no spirals. The second placenta had a 10 cm long umbilical cord.
This has not been described.
Trophoblast external to barrier
There is no infiltration of trophoblast into the endometrial stroma or blood vessels.
There is no subplacenta and endometrial secretion in intercotyledonary areolae has been alleged to exist through electron microscopic observations. This was also suggested by the observations made by Hradecky et al. (1988b) on implanted placentas.
The sable antelope possesses 60 chromosomes, all acrocentrics (Wurster & Benirschke, 1968). The Y chromosome is minute, compared with the other elements. Claro et al. (1993) have made more detailed studies of this species' chromosomes, also finding 60 chromosomes but identifying the X as more similar to that of goat than cattle. To my knowledge, hybrids have not been reported. A more detailed banding study by Fordyce-Boyer et al. (1995) found subtle differences between roan and sable antelope chromosomes.
I know of no immunological studies on sable antelopes.
Other remarks - What additional Information is needed?
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Maar, T.W.J., Blumer, E.S., Spevak, E. and Osofsky, S.A.: Comparisons
among selected neonatal biomedical parameters of four species of semi-free
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