Early implantation and embryonic development of the baboon: stages 5, 6 and 7.

Implantation stages of the olive baboon, Papio cynocephalus anubis, showing embryonic development equivalent to Carnegie stages 5, 6 and 7 of development, were collected by hysterotomy and examined histologically. The younger specimens (stage 5) consisted of a thick trophoblastic plate composed of cytotrophoblast and syncytiotrophoblast with multiple small clefts, and a bilaminar disk embryo with a small slit-like amniotic cavity. An epithelial plaque response was present in the uterine epithelium immediately peripheral to the implantation site, within an area of pronounced uterine edema. The bilaminar embryonic disk consisted of columnar epiblast cells underlying the amniotic cavity, and thickened visceral endodermal cells that form part of the yolk sac. The slightly further developed placenta (stage 6) consisted predominantly of cytotrophoblast including primary villi and syncytiotrophoblast lining large spaces containing maternal blood. Secondary placental villi were present in the oldest group (stage 7), and there was modest decidualization of the uterine stroma. An epithelial plaque response persisted, but varied in extent. The sequence of events in early development in the baboon is similar to that in the rhesus monkey insofar as blood space formation and endometrial responses are concerned. However, the plaque response is not so great as in the rhesus; there is no secondary placenta, and the decidual response is slightly more extensive.

Reproduction in the vervet monkey (Cercopithecus aethiops): I. Testicular volume, testosterone, and seasonality.

To test whether the male could contribute to the birth peak seen in both wild and captive vervets, testicular volume and peripheral testosterone concentration were measured monthly in nine adults throughout a 14-month period. Volume was an average of 15% greater during the months of June to September, the period of natural breeding activity in the wild, than at other times of the year. Testosterone concentration rose throughout the time period but did not correlate with testicular volume. Quarterly biopsies of the right testis in animals either used for or withheld from breeding revealed the presence of spermatozoa and the existence of spermatogenesis throughout the year. There was no correlation of testicular volume with breeding status or biopsy. If these results from individually caged animals are representative of group-caged and wild animals, then such small seasonal changes are unlikely to affect year-round breeding. Therefore, a physiological contribution by the male to natural birth peaks seen in the wild and captivity is not readily apparent.