Light microscopic studies of the stomach of the lesser mouse deer (Tragulus javanicus).

The stomach of the lesser mouse deer was studied at the light microscopic level using histological and immunohistochemical methods. The stomach was clearly differentiated into rumen, reticulum including reticular groove, a small transition zone and abomasum. The mucosal surface of the rumen, reticulum and transition zone was lined with a stratified squamous epithelium and that of the abomasum with a simple columnar type. The epithelial keratinization was weak in the rumen, floor of the reticular groove and transition zone, while it was strong in the reticulum, especially on the tip of the reticulum papillae. Large sinusoidal capillaries were often present in the ruminal papillae. In the ruminal mucosa, a thin layer of alpha-smooth muscle actin immunoreactive cells was demonstrated by immunohistochemistry. The muscularis mucosae of the reticulum was continuous and well-developed. The transition zone appeared as a nonglandular area having many low mucosal folds and two layers of tunica muscularis. The abomasal mucosa consisted of cardiac, proper gastric and pyloric glands. Cells immunoreactive for bovine pepsinogen and bovine prochymosin antisera were demonstrated in the abomasum. It is suggested that the characteristic features observed might be adaptations to a relatively rapid passage and rapid absorption of the fermentation products. There is some evidence that the transition zone is not a part of either the floor of the reticular groove or the abomasum, suggesting a possible reevaluation of the term used for the reticulo-abomasal orifice in the mouse deer.