Henke Zaskia, Sahd Lauren, Matthee Sonja, Kotzé Sanet H
Faculty of Medicine and Health Sciences, Division of Anatomy and Histology, Department of Biomedical Sciences, Stellenbosch University, Cape Town, South Africa.
Department of Conservation Ecology and Entomology, Private bag X1, Stellenbosch University, Stellenbosch, South Africa.
J Morphol. 2018 Sep;279(9):1282-1289. doi: 10.1002/jmor.20856. Epub 2018 Sep 6.
Several muroid rodent species are distributed throughout southern Africa. Some species are reportedly classified as opportunistic omnivorous rodents consuming plant, seed, and insect material. This study aims to provide a detailed morphometric analysis of the gastrointestinal tract (GIT) of four such omnivorous species, including stomach content analysis. Fixed GIT specimens (n = 5 of each) of Rhabdomys dilectus (Mesic four-striped grass mouse), Rhabdomys pumilio (Xeric four-striped grass mouse), Aethomys chrysophilus (Red rock rat), and Lemniscomys rosalia (Single-striped grass mouse) were weighed. Length and circumference measurements of each anatomically distinct GIT region were determined to calculate the basal surface area (BSA). Histological sections from each GIT region were used to calculate a surface enlargement factor (SEF). The BSA and SEF were multiplied to calculate the luminal surface area (LSA) of each GIT region. Stomach content was analyzed both macroscopically and histologically. All species had a similar GIT morphology, namely a unilocular, hemiglandular stomach with a clear limiting ridge, which indicated the transition from stratified squamous epithelium to glandular epithelium. A large loosely spiralled cecum was present in all species. A narrowing of the cecal apex accompanied by lymph aggregates, confirmed histologically in both Rhabdomys species, indicated a cecal appendix. A single short colonic loop with a unique folding pattern for each species was present in the proximal colon. The colonic mucosal surface presented with proximal V-shaped, and distal longitudinal folds. Intermediate transitional S-shaped folds were present in three species (R. dilectus, R. pumilio, and L. rosalia). Colonic mucosal folds indicated hindgut specialization similar to other muroid rodents. The hindgut specialization was further supported by morphometric analysis, which indicated large BSA and LSA measurements in the cecum and colon. These adaptations are consistent with herbivory, despite stomach content analysis revealing omnivorous tendencies.
几种鼠科啮齿动物分布于非洲南部各地。据报道，一些物种被归类为机会主义杂食性啮齿动物，以植物、种子和昆虫为食。本研究旨在对四种此类杂食性物种的胃肠道（GIT）进行详细的形态计量分析，包括胃内容物分析。对南非横纹鼠（Mesic四线草鼠）、侏儒横纹鼠（Xeric四线草鼠）、金背岩鼠和罗莎单纹草鼠的固定GIT标本（每种n = 5）进行称重。测定每个解剖学上不同的GIT区域的长度和周长，以计算基底表面积（BSA）。使用每个GIT区域的组织学切片来计算表面扩大因子（SEF）。将BSA和SEF相乘，以计算每个GIT区域的管腔表面积（LSA）。对胃内容物进行宏观和组织学分析。所有物种的GIT形态相似，即单腔、半腺胃，有明显的界限嵴，这表明从复层鳞状上皮向腺上皮的转变。所有物种都有一个大的松散螺旋状盲肠。在两种横纹鼠中，组织学证实盲肠顶端变窄并伴有淋巴聚集，表明存在盲肠阑尾。近端结肠有一个单一的短结肠袢，每种物种都有独特的折叠模式。结肠黏膜表面呈现近端V形和远端纵向褶皱。三种物种（南非横纹鼠、侏儒横纹鼠和罗莎单纹草鼠）存在中间过渡性S形褶皱。结肠黏膜褶皱表明后肠特化与其他鼠科啮齿动物相似。形态计量分析进一步支持了后肠特化，该分析表明盲肠和结肠的BSA和LSA测量值较大。尽管胃内容物分析显示有杂食倾向，但这些适应性特征与食草性一致。
