Abstract text (incl. figure legends and references)

The African giant pouched-rat (AGR) is semi-fossorial, nocturnal and omnivorous wild rodent that is widely distributed in sub-Saharan Africa.. AGR is used to detect land mines and for tuberculosis investigation and other biomedical uses. The stomach plays important roles in the physical and digestive process. There are reports on gross anatomy, morphometric and histology of the digestive tract of AGR (Knight and Knight-Eloff; 1987). Detailed investigations on the internal morphology of the stomach of AGR are scant, and studies that used scanning electron microscopic technique (SEM) for investigation rare. This study therefore seeks to examine the relationship between stomach structure and food habits by gross dissection, stereomicroscopy, and histology and scanning electron microscopic techniques. Six adult rats of either sex captured from the wild at night with metal-cage traps were used. Grossly, the stomach externally showed a U-shaped compartmentalized parts with copious sacculations. Well developed oesophageal groove, numerous papillae (corpus of non-glandular zone) and pyloric pouch were identified. An internal limiting ridge demarcated glandular from non-glandular part (FIGS.1A-1D). The four regions of the glandular stomach are cardiac, fundus, pylorus and antrum, while non-glandular zone consists of coma-shaped fundus and out-pocketing saccus cecum. Internally non-glandular zones are comprised of protruded papillae-like structures and thick wall, the glandular part showed smooth fundic mucosa, pyloric sphincter and gastric diverticular folds. The mean weight and length and width of the stomach were 27.7g, 19.5 cm and 3.9 cm respectively. Histologically (Fig. 2A), the arrangement of stomach tissues was as seen in typical mammalian pattern with variations in the glandular and non-glandular compartments. The wall of the stomach in the glandular and non-glandular regions showed four layers; mucosa supported by lamina propria, submucosa (loose connective tissue, vessels and nerves), muscularis (inner oblique, inner circular and out longitudinal muscle layers) and serosa. Non-glandular corpus and fornix ventriculi was covered in the lumen by numerous papilla lined by stratified keratinized epithelium. The glandular part is folded into rugae and the complex epithelial/ glandular lining contains depressions (gastric pits) which provided entrance into gastric glands lined by five types of typical epithelial cells There were variations of these components in the parts of the glandular antrum, cardiac, fundic and pyloric glands. The presence of neutral and acidic mucins in the gastric pits was demonstrated by PAS and AB reactions. Under SEM, the mucosal surface of the non-glandular compartment showed projections of robust papillae with longitudinal invaginations and desquamated keratinous structures of the papillae(Figs.2B-D). In fundic glandular part, gastric plicae with numeous openings of gastric glands were apparent and several longitudinal rigdes were seen amongst the plicae in the pyloric antrum. The study demonstrated that the stomach of AGR is complex as in other Cricetids (Perrin and Kokkin, 1986). The presence of sacculations, well-developed, numerous papillae, and pyloric pouch makes it remarkably different from other wild rats and supports its omnivorous dietary habit and symbiotic bacteria role in the stomach.

Knight & Knight-Eloff (1986). J. Zool., 213:7-22

Perrin & Kokkin (1986). South Afr. J. Zool., 21(3):202-210