Ontogenesis of the rumen: a comparative analysis of the Merino sheep and Iberian red deer.
The aim of this study is to describe differences in the ontogenesis of the rumen in the sheep (domestic ruminant) and deer (wild ruminant). A total of 50 embryos and fetuses of Merino sheep and 50 of Iberian deer were used, from the first stages of prenatal life until birth. For the study, the animals were divided into five experimental groups according to the most relevant histological characteristics. The appearance of the rumen from the primitive gastric tube was earlier in the sheep (22% gestation, 33 days) than in the deer (25% gestation, 66 days). In both cases it displayed a primitive epithelium of a stratified, cylindrical, non-ciliary type. At around 28% gestation in the sheep (42 days) and 26% (67 days) in the deer, the rumen was configured of three clearly-differentiated layers: internal or mucosal, middle or muscular and external or serosal. In both species the stratification of the epithelial layer was accompanied by modifications in its structure with the appearance of the ruminal pillars and papillae. The pillars appeared before the papillae and the appearance of both structures was always earlier in the deer (pillars: 70 days, 27% gestation; papillae: 97 days, 36% gestation) than in the sheep (pillars: 42 days, 28% gestation; papillae: 57 days, 38% gestation). The outlines of the ruminal papillae appeared as evaginations of the basal zone toward the ruminal lumen, dragging in their formation the basal membrane, the lamina propria and the submucosa. The tegumentary mucosa of the rumen was without secretion capability in the first embryonic phases. From 67 days (26% gestation) the neutral mucopolysaccharides appeared in the deer and at 46 days (30% gestation) in the sheep. In both cases they continued to decrease until birth, this diminution being more pronounced in the deer. Finally, the presence of neuroendocrine and glial cells was detected in the deer at earlier stages than in the sheep.
Department of Veterinary Anatomy, Faculty of Veterinary Medicine, University of Extremadura, Cáceres, Spain. afranco@unex.es
Antonio
A
Franco
Javier
J
Masot
Eloy
E
Redondo
D000818:Animals; D003670:Deer / Q000196:embryology*; D004848:Epithelium / Q000196:embryology; D005260:Female; D005865:Gestational Age; D005966:Glucuronidase / Q000378:metabolism; D008190:Lyases / Q000378:metabolism; D009024:Morphogenesis; D055099:Neuroendocrine Cells / Q000166:cytology; D009457:Neuroglia / Q000166:cytology; D012417:Rumen / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D034561:Sheep, Domestic / Q000196:embryology*
C021812:mucopolysaccharidase; D005966:Glucuronidase; D008190:Lyases