Soemmerring's Gazelle (Gazella soemmerringi(i))

Order: Artiodactyla

Family:Bovidae

1) General Zoological Data

This gazelle was named in honor of a great German physician upon his 50th anniversary of obtaining the medical degree. Cretzschmar (1826) depicted that animal as being quite dark brown; it is reproduced here from the first picture. In the review of "Nanger" gazelles, however, Lange (1971) described the animal as having a light-colored back. Moreover, he suggested that a number of subspecies exist, largely differentiated by horn types. He reviewed skulls and living specimens of this species and compared them with Dama and Grant gazelles. Soemmerring's gazelle is the smallest of these species and is one of the "Nanger" (naguer) gazelles, or "Spiegelgazellen" (because of the white rear patch). The denominated specimen was said to have originated in Somalia. Most or at least many animals now kept in zoos come from Khartoum, but who it is that makes the decision for the denomination "Soemmerring" of any given animal is unknown. This is even more dubious when their chromosomes and varied phenotypes are studied. It would appear that there is a mixture of these animals in captivity and few if any are truly Soemmerring's gazelles as originally described. This hybridization of related species with, however, different chromosome numbers, is perhaps also the reason for their frequently poor reproductive performance in captivity.

Longevity of this species was given as being 15 years 6 months (Jones, 1993). The behavior of this species was studied in detail by Walther (1964).

Soemmerring's gazelle from Cretzschmar's original description. The horn shape is especially characteristic for this species.

Putative Soemmerring's gazelle acquired by S.D. Zoo. The horn shape is proper.

Another putative Soemmerring's gazelle acquired by S.D. Zoo. The lateral stripe alone rules this out as a typical Soemmerring's gazelle.

Soemmerring's gazelles at Abu Dhabi Zoo. Note the characteristic shape of the horns.

2) General Gestational Data

Mentis (1972) reviewed many characteristics of ungulate gestations. The gestational period of Soemmerring's gazelles is given as "a few days over 7 months" from observations in the Giza Zoological Garden. Singletons are the rule. The neonate observed by us weighed 2,600 g and the placenta was 175 g.

3) Implantation

There are no reports on early implantation and the mode of implantation. In general it can be expected that all reproductive aspects are very similar to those of the Mhorr gazelle. They have there been summarized in considerable detail and the reader is invited to check details there as well.

4) General Characterization of the Placenta

The placenta of this species has not been described heretofore. One term placenta was available to me from a newborn female that took a few breaths but then expired. The newborn weighed 2,600 g and had a crown-rump length of 42 cm. The multicotyledonary placenta weighed 175 g, measured 62 cm in greatest dimension and occupied both uterine horns. The horn with the fetus contained 37 cotyledons, whilst the lesser horn had 32 cotyledons, essentially the same number as found in the Mhorr gazelle. The cotyledons are arranged in 3-4 rows. The cotyledons measured between 3 and 2 cm in widths and 0.4 cm in thickness. The umbilical cord inserted in the center and measured 9 cm. It contained four blood vessels and the large allantoic duct. These observations are very similar to those of the Mhorr gazelle as well (see that chapter). This is an epithelio-chorial, multicotyledonary placenta.

Delivered placenta of Soemmerring's gazelle described here.

5) Details of fetal/maternal barrier

The long, slender villi are covered by simple, and mostly single-nucleated trophoblast and abut maternal endometrial epithelium (which is not present in this specimen, of course). There is also too much autolysis in this specimen to make really detailed observations. Nevertheless, typical binucleate cells are present, as expected, but they are not abundant. The fetal capillaries impinge deeply upon the trophoblast. There is virtually no yellow pigmentation of trophoblast in the specimen for study.

Chorion and first branches of villous ramifications; slight autolysis - no pigment.

Higher magnification of villous surface with two binucleate cells. Note close proximity of fetal capillaries to the villous surface.

6) Umbilical cord

There are two arteries and two veins. In the center is a large allantoic duct. The cord is not spiraled and was 9 cm long in this specimen. Characteristically, one pair of vessels passes to one horn, the other pair to the other horn. In addition to the paired large blood vessels, there are numerous smaller blood vessels, especially around the allantoic duct. It is lined with flat urothelium and contained some debris.

Central portion of the umbilical cord with allantoic duct and edge of large artery.

7) Uteroplacental circulation

No details are known.

8) Extraplacental membranes

The outer surface of the placenta is covered with tall trophoblast and the membrane is markedly vascularized. The amnion is extremely thin and has no vessels.

9) Trophoblast external to barrier

There is no infiltration of trophoblast into the endometrial stroma or myometrium.

10) Endometrium

No data exist and I have not had a pregnant uterus for study.

11) Various features

No special features are known to me.

12) Endocrinology

I am not aware of any studies detailing information on hormonal studies of Soemmerring's gazelles. Nevertheless, it is likely that those published for Mhorr gazelles are relevant (Pickard et al., 2001). They found by studying fecal progestogens that the estrous cycles is 18, 6 days long and progestins rose after the tenth week of pregnancy.

13) Genetics

The chromosomes of Soemmerring's' gazelles are complex (Benirschke, et al., 1984). As many other African gazelles, Soemmerring's gazelles have an autosome/X chromosome fusion. Thus, males and females would have different chromosome numbers; generally the males have one more than females. There is, however, also an autosome/Y chromosome fusion and several other complex structures were found. But that is not enough; when we examined 8.20 different so-called Soemmerring's gazelles from different localities we found 6 different chromosome numbers (ranging from 34 to 39) and various additional (autosomal) fusions of the Robertsonian type. It is also a fact that few of the animals examined (or kept in zoos) have the precise phenotype as originally described when the species was named by Cretzschmar. Most animals come from exportation out of Khartoum, but their real origin is generally unknown. Perhaps the animals kept at Abu Dhabi (shown above) are most like those described originally. Many animals in zoological gardens must be assumed to be hybrids of various North African gazelles. Vassart et al. (1995) showed well-banded chromosomes of a male with 2n=36 (see below) and further elaborated on the complex chromosome structure of gazelles.

The dam giving birth to this neonate had 36 chromosomes; the male had 37 chromosomes and is the sire of most San Diego animals.

Karyotype of female Soemmerring's gazelle with 36 chromosomes.

Karyotype of male with 37 chromosomes that show the numerous translocations.

The various chromosomal arrangements in 28 animals (from Benirschke, et al., 1984).

14) Immunology

No details have been published.

15) Pathological features

A common problem experienced in our group of animals has been lack of parental care with malnutrition resulting. Iori & Lanfranchi (1996) described the infection with helminths in animals from Somalia. Some of our animals have suffered dental disease.

16) Physiologic data

Various hematologic and chemical studies were summarized by Olsen & Jones (1984).

17) Other resources

Numerous cell strains are kept in the "Frozen Zoo" of the Zoological Society of San Diego (CRES). They can be made available by contacting Dr. Oliver Ryder at oryder@ucsd.edu.

18) Other remarks - What additional Information is needed?

Implanted placenta in uteri should be studied. Also, because of the numerous chromosomal varieties, I have recommended that only those animals be bred that have compatible karyotypes. No hormonal data have been accumulated.

Acknowledgement

I appreciate very much the help of the pathologists at the San Diego Zoo.