General Zoological Data
Giraffes are believed to have originated in Africa during the Miocene (Thenius, 1967; Spinage, 1968; Gentry, 2000). This is in contrast to the okapi, the other member of the family Giraffidae. The okapi presumably stems originally from short-necked giraffoid ancestors in Asia. The much lower chromosome number of the giraffes (2n=30, down from 2n=46 in okapis and nilgai) also suggests a later derivation of the giraffes from bovid ancestral stock. Investigation of tooth morphology (Solounias et al., 2000) additionally provides significant differences in the browsing behavior of the giraffe and okapi. There is, however, ongoing discussion of the development of giraffidae in the literature that may ultimately only be resolved by more sophisticated genetic studies (Gatesy & Arctander, 2000).
In the past, giraffes extended over Eurasia but they are now confined to sub-Saharan Africa. They are browsing animals of the open savannah. Many behavioral and structural differences exist between the giraffe and okapi that will also be of interest in the future exploration of their evolution (Gijzen, 1959). Suggestions have, therefore, been made to place these animals into separate subfamilies.
There is only one good species of giraffe, with at least four (some authors suggested eight) subspecies. They have various color and reticulation patterns, largely depending on their location in Africa. Their distinct status as defined subspecies is often challenged; these forms also have often hybridized. Giraffes weigh between 500 and 1,930 kg (Hayssen et al., 1993). Males are larger than females. Neonates are recorded to weigh between 30 and 100 kg.
|Masai giraffes at San Diego Zoo.|
|Masai giraffe at San Diego Zoo.|
General Gestational Data
Characterization of the Placenta
The following weights of giraffe placentas are available:
expansion of the opened sac was 156 cm in the gravid horn and 135 cm in
the nongravid horn of the placenta described by Deka et al. (1980); maximum
breadth was 56 cm. In the placenta here shown, the diameters were 181
x 35 cm. In another Masai giraffe placenta that I examined, the expansion
was 181 x 40 cm. It had 155 cotyledons in four rows, with considerable
difference in sizes. The reticulated giraffe specimen measured 160 cm
in greatest length, 70 cm across and had a large allantoic sac.
In July, 2004 I obtained the pregnant uterus from a Ugandan giraffe that had died from aspiration, following the “bloat”. The 190 g male fetus was in the left horn, the side that also contained the large corpus luteum in its ovary. The placenta extended into the right horn as well, but the cotyledons were remarkably smaller in that horn. The left horn contained 60 cotyledons, the right had 50. The cord was 12 cm long, had a decidedly right spiral and was studded with diminutive foci of squamous metaplasia. There was abundant light yellow allantoic and amnionic fluid present, and the fetal bladder was filled with urine as well.
|Fetal surface of a portion of a term, delivered giraffe placenta with cord insertion site.|
|Maternal surface of a portion of giraffe placenta at term. There are four somewhat irregular rows of cotyledons of great size difference.|
|Term Masai Giraffe placenta with surviving female newborn - 155 cotyledons in four rows. Insertion of umbilical cord at arrow.|
|Term Masai Giraffe placenta with surviving female newborn - 155 cotyledons in four rows. Insertion of umbilical cord at arrow.|
|Giraffe uterus with 190 g conceptus in left horn. Ovaries are at arrows.|
Uterus before opening the fetal sacs.
|Opened uterus with fetus in left horn; the sac of the right horn is not yet opened.|
|The 190 g fetus with short but twisted cord.|
Details of fetal/maternal barrier
|Partial cotyledon of delivered giraffe placenta. The maternal surface is ragged, as it withdrew from the caruncle. Note the straight and minimally branched villi. Fetal surface vessels above, within the chorion.|
|Edge of giraffe cotyledon. Arrow is at the continuation of the chorion between cotyledons.|
|Term giraffe placental surface with focal pigment deposition beneath the chorionic plate.|
|Edge of cotyledon of giraffe placenta. At right top, the chorion and trophoblast extend over the intercotyledonary region and the areolae.|
|Chorion at right, trophoblast over the intercotyledonary region (left) with areolar proteinaceous fluid (uterine milk).|
|Binucleate trophoblastic cell at tip of villus. Note superficial location of fetal capillaries.|
The placenta of the immature gestation described above (190 g fetus) had 110 cotyledons. They were significantly smaller in the unoccupied sac. The histology is not much different from that of the term gestation but there was absolutely no pigment beneath the chorionic plate. Binucleate cells were very rarely found. The relationship to the maternal endometrial surface is nicely shown in the photographs.
Reflections on trophoblastic pigment : Although I have stated several times that the trophoblast possesses hemosiderin inclusions, this is far from certain when reviewing other ungulate placentas. I had never stained the giraffe placentas but have now and there is no hemosiderin in the granular inclusions shown next. Thus, are they iron-containing or are we wrong in this general assumption of this route being a way for iron to be absorbed by the fetus? In other sections of this book I have suggested that this may actually be melanin, perhaps liberated from the skin. Granted, it is in big chunks and has the superficial appearance of hemosiderin and not that which we consider to be melanin in melanocytes. But, bleaching with hydrogen peroxide abolishes the pigment (as it does melanin), it stains with silver (as does melanin) and is iron-stain negative. It also does not stain for bilirubin, the only other pigment that one might consider. Thus, at present I think we must consider that it is perhaps melanin that is accumulated from “melanemia” perhaps from rubbing the skin and liberating the pigment. Besides, if this region of pigmentation really did serve as an important organ to transfer iron to the fetus, as is suggested by the term “hemophagous organ”, then one should surely expect it in immature placentas as well. It is not present in this case shown here.
|Allantoic duct in center of umbilical cord. Large vessel edge at right. Numerous small vessels are present and the allantoic duct has a muscular coat.|
|Allantoic duct of the immature placental umbilical cord.|
|Squamous nodule on the surface on immature umbilical cord.|
|Amnion near the insertion of umbilical cord with squamous pearl (verruca) at right.|
|Edge of cotyledon with intercotyledonary membrane spanning to the right.|
|Trophoblast of membrane at left; allantoic epithelium at right.|
Trophoblast external to barrier
|Low power view of neonatal giraffe uterus with four caruncles (C=caruncles)|
|Fetal uterus with caruncle at top and glandular endometrium below.|
|Neonatal giraffe ovary with three adjacent luteinized ovarian follicles (probably atretic follicles). In the very center is a fibrous scar of one.|
|Low-power view of neonatal giraffe ovary with immature oocyte mantle and stimulated follicles below.|
|Higher power view of a similar area as the previous photograph. Note the large, luteinized theca/granulosa cells. The deep red cytoplasm of these cells suggests early involution.|
|Luteinization of the "interstitial cells" of a giraffe neonatal ovary (arrows point to the collections of epithelioid cells.)|
Fetal ovary of stillborn giraffe with apparent corpora lutea.
The other ovary of the same stillborn giraffe fetus.
|The two ovaries of the pregnant giraffe with 190 g fetus. The left ovary has the very large corpus luteum, the right has a small luteinized old follicle.|
|Villus from normal giraffe placenta with extensive hemosiderin deposit around a thrombosed blood vessel.|
|Area of old degenerative change in a large villus (arrows) of an otherwise normal term giraffe placenta.|
Similar villous degeneration of a reticulated giraffe placenta.
Higher magnification of degenerating villus of term reticulated giraffe with yellow pigment of focal mineralization.
In July, 2003, we had an abortion in a Baringo giraffe. The dam went spontaneously into labor and was known to be ill. The structurally normal male fetus weighed only 19 kg and the small placenta weighed 1,300 g. Most remarkably, it had only 23 cotyledons that were yellow-red and appeared infected. The cord was 34 cm long. Pictures are shown next.
Touch preparations from the cotyledonary surface yielded very long bacilli, with some similarity to actinomyces. Sections of umbilical cord, membranes, fetal lung and testis were all normal and not inflamed or degenerated. The cotyledons, however, had a largely necrotic surface and the same long organisms were identified. Post partum the dam has a vaginal discharge but, while on antibiotics, seems reasonably healthy. Sections are shown next. I speculate that the dam must have had a preexisting endometritis that prevented normal cotyledons to form so that she ended with only 23 and very small cotyledons. That the fetus grew to become 19 kg in size is remarkable. The only similar histology I have encountered is that of a dromedary (see that chapter) in which a stillborn had a largely calcified villous surface that has great similarity to this placenta.
Murai et al. (2007) have described a large (20x36x20 cm) teratoma of the umbilical cord of a reticulated giraffe two months before birth; the dam died during gestation.
Other remarks - What additional Information is needed?
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Gatesy, J. and Arctander, P.: Molecular evidence for the phylogenetic affinities of ruminantia. Chapter 9, pp. 143-170, in Vrba, E.S. and Schaller, G. B., eds. Antelopes, Deer, and Relatives. Yale University Press, New Haven, 2000.
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