127 VILLOUS ARCHITECTURE AND FETO-MATERNAL INTERDIGITATION IN THE AFRICAN BUFFALO (SYNCERUS CAFFER) DURING DIFFERENT GESTATION STAGES

Abstract

Anchorage of the ruminant placenta is achieved by complementary indentation of chorionic villi into endometrial crypts. Geometrical patterns of interdigitation vary greatly among ruminants. Fetal villosity has been studied in other bovid species (Bos taurus, Bubalus bubalis) closely related to the African buffalo. The present study provides first information on villous architecture and feto-maternal anchorage in the African buffalo. Tissue samples from six pregnant cows (crown/rump length in cm: 2, 3, 14, 17, full-term) were collected during disease eradication programs in the Hluhluwe Game Reserve and from a buffalo breeding centre at Phalaborwa (afterbirths, n = 3). Tissue was fixed with 2.4% glutaraldehyde in Millonig's phosphate buffer by immersion or, if possible, via vascular perfusion through uterine and umbilical arteries prior to separation of feto-maternal tissue for scanning electron microscopy (SEM) preparation. Samples were further prepared for light microscopy and SEM using standard techniques. SEM samples were examined in a Philips XL 20 Microscope operated at 7 kV. Fetal villi consisted of a vascularized mesenchymal core covered by trophoblast epithelium. At a crown/rump length of 2 and 3 cm, the cotyledons comprised numerous short finger-like villi (length = 0.15–0.46 mm) originating from the chorionic plate. Some of these primary (stem) villi divided longitudinally a short distance from their origin. These relative simple villi were accommodated within corresponding caruncular crypts. At later gestation (crown/rump length: 14 and 17 cm), fetal villi had lengthened (length = 2–7.5 mm) and lateral (secondary) branching had started. The latter appeared in the form of bulbous or elongated structures projecting at approximately right angles from the stem villus. During the last month of gestation and in post-partum samples, primary (8–12 mm) and secondary villi had developed considerably in length. Secondary villi displayed a complex array of tertiary (terminal) villi of variable shape and size. A rich capillary network was observed within the connective tissue core of the tertiary villi as well as in the corresponding endometrial septae forming the walls of the caruncular crypts. Fully developed, each primary villus with its attendant secondary and tertiary villi formed a slender conical-shaped unit, also referred to as a cotyledonary villous tree. This paper provides the first description of villous architecture and placentome development in the African buffalo. The specific branching pattern of cotyledonary villi and complementary caruncular crypts in the African buffalo placenta, as described in this study, appears less complex when compared to that in the placenta of related Bos and Bubalus species.