Capra ibex ibex
East Caucasian Tur
1) General Zoological Data
There are eight recognized ("good") species of goats, and many subspecies exist as well (Nowak, 1999). Material adequate for study was available from three of these species, and the findings of their placental morphology were, in general, quite similar. Nevertheless, minor differences were identified in their placentas and membranes. For that reason these are so indicated separately below. The reader should also refer to my chapters on the Sheep, Cretan Goat, and on the Nubian Ibex. Nievergelt (1966) has published a detailed ecological study of the Alpine ibex.
The origin of the domestic goat, perhaps the first ruminant animal to be domesticated by humans, and the sheep has been of interest for years, and it is still in dispute. Numerous osteological and genetic studies have attempted to clarify this puzzle. Harris (1962) concluded that it was the Bezoar goat (with at least five subspecies) that was the ancestral matriarchal form. This was further supported by evidence from an mtDNA study by Takada et al. (1997) on a relatively small sample of goats. More recently, satellite DNA studies (Curtain et al., 1973), and mtDNA cytochrome b sequences were used to arrive at more modern views of these ancestral relations (Hassanin et al. 1998). These studies, while also still not conclusive, relate C. ibex and C. hircus very closely. Mannen et al. (2001) sequenced the entire mtDNA displacement loop region and also the cytochrome b gene of several Laotian strains of goat and of markhor, and considered the markhor to be very closely related as well. The Tur is presumably more distant. More recently, Pidancier et al. (2006) studied other regions of the mtDNA and the DNA of the Y-chromosome of a variety of goat species and found two possible ancestral trees, without coming to a complete resolution of the discrepancies.
The Alpine ibex was once widely distributed over the European Alps but it is now restricted to a few protected areas (Harris, 1962). Careful measures of protection and some reintroductions of a dwindling number of animals have lead to a remarkable recovery of this subspecies (Nowak, 1999). Its phenotype, with the flat ridges across the broad anterior portions of the flat horns and the small beard, is characteristic. Longevity in captivity was given by Jones (1993) as being 18 years and 9 months. Age can be estimated by the annually increasing number of rings on the horns. Gestation lasts 150-180 days, with usually single births of 2-4 kg (Nowak, 1999). Twins occur only rarely. Puschmann (1984) gives the length of gestation as 155-170 days.
The East Caucasian Tur has more cylindrical horns with prominent ridges and they are sloped to the back. The males also have beards. Like the somewhat different West Caucasian Tur, the bodies are massive. Their gestation lasts 150-160 days and single births (3-4 kg) are the norm. Longevity in the wild is short (10 years), while in captivity they may live to 15 years (Jones, 1993).
The Turkmenian Markhor has very characteristic screw-like spiraled horns in both sexes, although those of males are much more impressive. Gestation lasts 135-170 days according to Nowak (1999), and 140-150 days according to Puschmann (1984). Twins are common and the neonatal weight is 1.5-2.5 kg. The animal is endangered. Longevity is 14 years.
General Gestational Data
Alpine Ibex: Gestational length is 150-180 days, usually singletons are born weighing 2-4 kg.
East Caucasian Tur: Gestational length is 150-160 days, singletons, rarely twins. Neonatal weight is 3-4 kg.
Turkmenian Markhor: Gestational length is 135-170 days, singletons are born but twins occur often, weighing 1.5 - 2.5 kg.
Details of fetal/maternal barrier
The villi of all three species are slender and interdigitate with the, relatively even more slender, maternal fibrous septa whose covers consist of flat, deeply-stained epithelium. There is no trophoblastic invasion of the endometrium to speak of (perhaps minimal endometrial destruction occurs at the margins of cotyledons), and binucleate cells are sparse and scattered over the otherwise cuboidal trophoblastic surface. Foci of calcification occur normally in the debris between villi and septa, and especially in the tips of occasional maternal septa. The trophoblast beneath the chorionic surface is taller, cylindrical and heavily pigmented with yellow flakes and granules. Much less pigment is present between the cotyledons.
This pigment has been of interest to me. It has usually been assumed to derive from maternal hemorrhages, and this region of ruminant placentas has been referred to as the "hematophagous region". It has been presumed that this area serves the fetus to obtain much iron from the dam. Iron stains have been consistently negative, however, and the "Gmelin" reaction for hematoidin (bilirubin) has failed to disclose that substance as representing the hemoglobin-derived pigment (see the chapter on urial sheep). Furthermore, the lack of solubility in organic solvents (alcohol, xylene, chloroform) does not match the expected quality of hematoidin. On the other hand, it is difficult to imagine that other pigments should exist in this location. To be inclusive, however, I have bleached the slides with peroxide (this is used in order to bleach melanin in histochemical preparations), and the pigmentation was abolished. Next I performed the "Schmorl" stain for melanin and this was focally positive. It was similar to the pigmentation of basal skin strata in control slides, but not quite so dark and uniformly black, as can be seen in the next photograph. While it is difficult to imagine that melanin gets into these specific trophoblastic cells, it is presently the more likely type of pigment, rather than being one of a blood derivative. Alternatively, it may be "ageing pigment", such as found in heart muscle, and occasionally referred to as "promelanin". It is of interest then to recall Amoroso's (1961) statement of the presence of melanoblasts in the sheep endometrium, as had been determined by Grant (1933). Perhaps the same pertains to exotic species and this aspect would be worthy of future study. For this reason then I performed silver stains that normally display melanin pigment, and it was positive also. I conclude, therefore, that this "hematophagous organ" is not likely the site of blood breakdown (and fetal iron absorption) but that it results from the degeneration of endometrial septal tips (observed) with release of their melanin. Perhaps differences in melanin content of ruminant endometria exist to explain the great variability of the amount of pigment found here.
The Alpine ibex cord measured 16 cm and was covered with fine yellow granules. That of the Tur was also 16 cm long. The umbilical cords of the younger Markhor fetuses were 9 cm long. All contained four large blood vessels and a large allantoic duct lined by urothelium. The smaller blood vessels of the cord congregated strikingly around the allantoic duct, more so than is found in other Artiodactyla, and they were often seen to emerge from the larger blood vessels. The cords had no spiraling but numerous plaques of squamous metaplasia were found on the surfaces.
Amoroso (1961) has shown some of the sheep placental vasculature, and sheep have served as experimental animals to understand gestational problems better for many years. An abundant literature is available that discusses blood flow but it cannot be cited in this brief context. The reader is referred to studies by Barcroft, Barron, Metcalfe, Battaglia, Meschia, and others.
8) Extraplacental membranes
The membranes between the cotyledons are covered with cylindrical trophoblast that is occasionally pigmented. The large allantoic sac lies next (inside) to it and has its usual small caliber vasculature and a cuboidal to cylindrical epithelium that is not pigmented and that has relatively clear cytoplasm. Small amounts of yellow hippomanes were found in the allantoic fluid of the Alpine ibex. The amnion is covered with thin epithelial cells and is avascular. Remnants of yolk sac are not found.
The endometrium has a tall columnar surface epithelium. Beneath this are numerous glands, but very few are found beneath the cotyledons. Here, the endometrium has a fibrous appearance. The surface epithelial sheet of endometrium covers the outside of the cotyledons to their mid to upper portions, as is seen in the low power photograph shown above.
Between the endometrial surface and the intercotyledonary membranous trophoblast is a large amount of scattered debris. It is of uncertain origin. It is not pigmented and has often a granular feature; elsewhere it appears as though being composed of debrided squamous flakes.
Trophoblast external to barrier
There is no convincing evidence for invasion of the maternal tissues.
No decidua in the true sense exists. The endometrial stroma becomes rather more fibrous at the site of implantation than it was in the nonpregnant caruncle.
There is no subplacenta.
Other remarks - What additional Information is needed?
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