Comparative gastrointestinal morphology of three small mammalian insectivores: Acomys spinosissimus (Rodentia), Crocidura cyanea (Eulipotyphla), and Amblysomus hottentotus (Afrosoricida)

Abstract

The gastrointestinal morphology was investigated in three mammalian insectivorous species, namely Acomys spinosissimus, Crocidura cyanea, and Amblysomus hottentotus. The aim of the study was to provide a comprehensive morphological comparison between the different species and to explore whether anatomical gastrointestinal adaptations are associated with the insectivorous diet of these species. The shape, proportional length, and proportional surface areas of the different gastrointestinal regions were recorded and compared in the three insectivores. Hematoxylin and Eosin (H&E) and Alcian Blue/Periodic Acid Schiff (AB/PAS) were used for morphological assessment. In all three species, the stomach was simple and uncompartmentalized. The internal aspect of the stomach in A. spinosissimus was hemi-glandular, containing stratified squamous epithelium in the fundus, with glandular epithelium in the body and pyloric region. However, C. cyanea and A. hottentotus had wholly glandular stomachs. Paneth cells were not observed in the intestinal tracts of C. cyanea and A. hottentotus. Acomys spinosissimus was the only species studied that had a cecum. The proximal colonic region of A. spinosissimus had V-shaped mucosal folds. Histologically, C. cyanea had villi throughout the entire gastrointestinal tract (GIT), whereas for A. hottentotus villi were not present in the most distal gastrointestinal regions. In both C. cyanea and A. hottentotus, longitudinal mucosal folds were present in the distal part of the colon. The GITs of C. cyanea and A. hottentotus showed little morphological differentiation namely, a simple, glandular stomach and the lack of a cecum.

The comparative gastrointestinal morphology of five species of muroid rodents found in Saudi Arabia

“…This was in contrast to the broad sac-like ceacum observed in A. spinosissimus (Boonzaier et al, 2013). Taenia and haustra were not observed in any of the caeca or the colons of the present study as was the case in A.…”

“…The V shaped colonic folds observed in the Meriones and Acomys species in the present study were similar to those described in A. spinosissimus (Boonzaier et al, 2013) and almost all myomorph rodents according to Björnhag and Snipes (1999) and Hume (2002). These folds are postulated to retain food particles and therefore slow down digesta transit (Boonzaier et al, 2013). In addition to the oblique folds noted in the above mentioned species, D. dasyurus exhibited folds arranged in a loose longitudinally arranged spiral similar to that described in two insectivorous species (A. hottentotus, and C. cyanea) studied by Boonzaier et al (2013).…”

“…Acomys spinosissimus (Southern African Spiny Mouse) (Boonzaier et al, 2013). The separating ridge in rodents is referred to as a bordering fold (Carleton, 1973) or a limiting ridge (Robert, 1971) and in non-rodent mammals such as the horse, a similar elevated line is called the cuticular ridge or margo plicatus (Sisson, 1911).…”

“…spinosissimus (Boonzaier et al, 2013). Taenia are usually associated with haustra which increase the storage volume of an organ and therefore cause retention or "damming up" of digesta.…”

“…These folds are postulated to retain food particles and therefore slow down digesta transit (Boonzaier et al, 2013). In addition to the oblique folds noted in the above mentioned species, D. dasyurus exhibited folds arranged in a loose longitudinally arranged spiral similar to that described in two insectivorous species (A. hottentotus, and C. cyanea) studied by Boonzaier et al (2013). While coprophagy was never described in any of the species in the present study, it is possible that these folds may slow down the rate of digesta through the first part of the colon and may suggest a colonic separation mechanism (CSM).…”