Sichuan takin (Budorcas taxicolor)

Order: Artiodactyla

Family: Bovidae

1) General zoological data

The takin represents the single species of the genus Budorcas. There are perhaps three subspecies, two of which are being bred at the San Diego Zoo. Much confusion exists concerning the relationship of takins to other bovidae. Budorcas denotes this, as it is best translated as "ox-gazelle" (in German "Rindergemse"), while "takin" is the Tibetan-Burmese name for the animal. "Taxicolor" is derived from badger-colored (Gotch, 1979). The golden takin has been a legendary animal because of its "Golden Fleece". Its taxonomic classification is apparently not yet resolved. This aspect is considered subsequently. The animals come from northeastern Asia, especially Tibet/China. They are stoic, large ox-like animals with shaggy hair and golden to brown color, depending on the subspecies. Despite its deliberate movements, takins are excellent climbers and have surprised us in captivity by nimbly climbing onto the partitions between enclosures. Their closest relative perhaps is the Canadian muskox, but that has been disputed recently (Groves & Shields, 1997). Others consider a relationship to caprinae. Takins weigh about 150-400 kg according to Nowak (1999). They are herbivores and have an apparently important need for salt. They are said to travel far to reach salt licks. The animals live in groups of 10-35 animals (occasionally hundreds) and prefer brush and forested areas.

Breeding colony of Mishmi and Sichuan takins at the San Diego Zoo.

Breeding colony of Mishmi and Sichuan takins at the San Diego Zoo.

Breeding colony of Mishmi and Sichuan takins at the San Diego Zoo.

2) General gestational Data

The gestation lasts 200-220 days according to Aung (1968), and Penny (1989) reports that the singleton neonates weigh from 5-7 kg. Twins are very uncommon. Sexual maturity is reached at 30 months and longevity is at least 20 years in captivity. The takins have become endangered in some regions.

3) Implantation

This has not been described.

4) General Characterization of the Placenta

There have not been any reports on takin placentas; this is apparently the first look at their structure. It is a multicotyledonary placenta with epitheliochorial trophoblast relationship to the endometrium. The single specimen I had available had 60 cotyledons varying from 1-5 cm in diameters. The entire placenta measured 70 x 30 x 1 cm and must have occupied both uterine horns. It weighed 650 g and was associated with a live birth. Unfortunately, the specimen was moderately autolyzed; that prevented excellent histologic preparations to be made. Nevertheless, because they are so rarely seen, I felt it important to present this placenta here.

Since the first description I have had the opportunity of seeing one additional term placenta for study. It weighed 1,050 kg, had 60 cotyledons that measured from 1 to 5.6 cm in diameters. The umbilical cord was 36 x 1.5 cm. In 2003 an additional placenta of a Sichuan takin became available that weighed 1,000 g and had140 cotyledons. It is depicted below. It measured 115x35cm in greatest dimension and the neonate survived. In January 2004 I obtained yet another Mishmi takin placenta at term. It weighed 700g and had 120 cotyledons. Thus, there is considerable variation in the number of cotyledons.

Macroscopic appearance of term takin placenta.

Second term takin placenta with 75 cotyledons, poorly arranged in rows. Maternal aspect.

Second placenta, fetal surface. Umbilical cord inserts at arrows. Small white amnionic nodules are present at tope left.

New Takin placenta (2003) with extensive areas of squamous metaplasia at arrows.

Surface of takin placenta with chorionic membrane above. Beneath the chorionic plate numerous hemosiderin-laden macrophages are present, from old hematomas.

While the structure of villi is similar to most other ungulates here presented, there is an unusual amount of subchorionic hemosiderin in macrophages, undoubtedly stemming from local hematomas. One can equate these with the so-called hematophagous regions of other species. Likewise, within the trophoblastic cells of the villous cover, hemosiderin is frequently seen within the cytoplasm.

5) Details of fetal/maternal barrier

Terminal takin villus with tall columnar trophoblast having microvilli and giant nuclei.

Terminal villi of takin placenta with binucleate trophoblast at arrows. Debris between the villi is interpreted as being due to autolysis.

Single villus of mature placenta of Sichuan takin. Note the large trophoblastic giant cells, especially at top left.

No implanted placenta has been observed, but the cotyledonary structure of this placenta is so similar to that of other bovid species that one may safely assume it is essentially similar in maternal relation. The villus has a thick layer of trophoblast and binucleate giant cells are present in the trophoblastic surface.

6) Umbilical cord

The umbilical cord of this placenta measured 8 cm in length and 3 cm in diameter. It contained 4 vessels (2A, 2V) and a large allantoic duct. In addition to the four principal blood vessels, there are very numerous small blood vessels, many associated with the allantoic duct. Hippomanes were found in the allantoic duct. It contained many birefringent crystals.

The most recent placenta obtained had extensive squamous metaplasia and numerous squamous/keratin inclusion cysts on its surface and on the amnion as well, as seen in other cases of this species (see below).

This is a portion of the umbilical cord with allantoic duct at left, containing Hippomanes with many crystals. Note the extensive smaller vasculature, next to the duct, and small blood vessels in the arterial wall at right.

7) Uteroplacental circulation

This section of the takin placental surface shows the degree of autolysis. Amnion and chorion are reasonably well preserved, but trophoblast is autolyzed. FV=fetal vessel.

The circulation has not been described but must be similar to other bovid species' placenta.

8) Extraplacental membranes

The amnion had many areas of squamous metaplasia. The allantoic membranes have a large number of small blood vessels. Some of these derive from the large allantoic vessels in the umbilical cord.

Section through one of the "pearls" on the amnionic surface, showing a keratin inclusion "cyst".

Sections of the membranes that partition amnion. The allantois contains debris and its connective tissue compartment is full of small blood vessels.

Sections of the membranes that partition allantoic sac. The allantois contains debris and its connective tissue compartment is full of small blood vessels.

9) Trophoblast external to barrier

There is no infiltration of trophoblast.

10) Endometrium

There are no reports and I have not had a uterus available for study.

11) Various features

None.

12) Endocrinology

No studies have been published to provide endocrine data. The animals have a birth interval of about one year.

13) Genetics

Takins have 52 chromosomes, while the muskox has 48. Both have the same NF (fundamental number) that suggested a closer relationship to us (Bogart & Benirschke, 1975; Pasitschniak-Arts et al., 1994). The latter authors performed an extensive study of takin, muskox and sheep chromosomes. In addition, they reviewed the sparse and conflicting anatomic literature of these species without firmly resolving the controversial aspects. Another point of view of the relation of takin to muskox was expressed by Groves & Shields (1997). These investigators studied the cytochrome-b mtDNA gene of these animals, and of three caprine species, to test the possibility of a common ancestor for muskox and takin. They rejected this hypothesis and suggested that convergent evolution was more likely to give rise to the similar phenotypes (size, horns, hair) and behavior of takin and muskox. Many additional cytogenetic studies have since been performed by us and these show a uniform 2n=52 for both subspecies. Hybrids have not been described.

14) Immunology

I know of no studies.

15) Pathological features

No reports are available on pathologic features.

16) Physiologic data

No data are available.

17) Other resources

The CRES facility of the Zoological Society of San Diego has cell strains of both Mishmi and Sichuan takins. Both subspecies exist in sizeable breeding groups at the San Diego Zoo. These can be obtained by contacting Dr. Oliver Ryder at: oryder@ucsd.edu.

18) What additional information is needed?

Better preservation (more rapid fixation) of new placentas is imperative.

Acknowledgement

Most of the animal photographs in these chapters come from the Zoological Society of San Diego. I appreciate also very much the help of the pathologists at the San Diego Zoo.