Implantation and early placentation in the one-humped camel (Camelus dromedarius)

The ovaries and uteri were removed from four pregnant camels on days 14, 25, 35 and 56 after ovulation. The day 14 and 25 uteri were perfuse-fixed with 3 per cent glutaraldehyde: 3 per cent paraformaldehyde whereas the day 35 and 56 specimens were opened dorsally for photography before biopsies of allantochorion attached to endometrium were taken and fixed in either 3 per cent glutaraldehyde: 3 per cent paraformaldehyde or Bouin's fluid. Samples of each uterus were then processed and sectioned for light and transmission electron microscopy. By day 14 the majority of the trophoblast had become closely apposed to the luminal epithelium of the endometrium to form the start of an epitheliochorial placenta with microvillar interdigitation initiated in some places. By day 25 a well-developed microvillar junction had formed between the fetal and maternal tissues. The fetus was situated in the middle of the left uterine horn in the day 35 and 56 specimens and, histologically, large multinucleate giant trophoblast cells had developed at frequent but irregular intervals along the, otherwise single-cell, trophoblast. These giant cells were often situated over the mouth of an endometrial gland but their actual function in pregnancy is not yet known.