The comparative anatomy of the abdominal gastrointestinal tract of six species of African mole‐rats (Rodentia, Bathyergidae)

Abstract

The gastrointestinal tracts (GITs) of six species of African mole-rats (Bathyergidae) were compared. The aim was to provide a comprehensive anatomical comparison between the different species. The relative shape, length, and surface areas were taken into account to determine whether the GITs are phylogenetically constrained or exhibit anatomical adaptations in response to diets. In all six species the stomach was simple and glandular. With the exception of Heterocephalus glaber, the caecum was coiled in a flat spiral, the ascending colon was arranged in a loop of varying lengths, and a mucosal colonic papillary-lined groove was present in the ascending colon in all species. By contrast, the caecum in H. glaber was uncoiled, the ascending colon was not looped, and the groove was not papillated. A caeco-appendix was observed only in Bathyergus suillus and Georychus capensis. Hierarchical multivariate cluster analysis on the presence/absence of nine anatomical structures associated with the GIT of mole-rats revealed that H. glaber was anatomically the least similar of the six species (77.6% similarity) with respect to the nine GIT variables included. All Cryptomys species were the same (100% similarity), and two species B. suillus and G. capensis grouped together and were more similar to the Cryptomys genus (95% similarity) than they were to H. glaber. These findings support previous phylogenetic classifications. The voluminous caeco-colon in B. suillus may be explained by its ingestion of grasses in addition to below-ground storage organs of plants. We conclude that phylogeny and diet affect the GIT anatomy of the African mole rats studied here.

The Topography and Gross Anatomy of the Abdominal Gastrointestinal Tract of the Persian Squirrel (Sciurus anomalus)

“…It is reported that the looping of the colon in various rodents with different morphological features is a way to package their relatively long colon into their abdominal cavity (Kotzé et al, 2010). This finding is consistent with our study, in which the extreme looping of colon was due to the high ratio of intestine length to body length.…”

“…Despite the visibly larger volume of the Persian Squirrel's cecum and ascending colon observed in situ (Fig.1), in addition to their relative lengths (Table II), Kotzé et al (2010) stated that the mere measurement of GIT length cannot accurately reflect the size of the various parts of the GIT and their absorptive areas. It has also been stated that GIT volume is determined either by using relative intestinal circumference measurements directly, or by comparing the intestinal content weight of various parts of the GIT to total GIT content weight indirectly.…”

“…The length of each part of the GIT was measured along the greater curvature of the stomach and the anti-mesenteric border of the intestine, using a pliable and non-stretchable tape. In addition, the surface areas of the various parts of the GIT were estimated calculating the mean of three different circumference measurements, taken at corresponding positions in all species, multiplied by the length of each part and expressed as percentage of the total gut surface area (more details in Kotzé et al, 2010).…”

Dietary composition and nutritional outcomes in two marsupials,Sminthopsis macrouraandS. crassicaudata

“…Similarly, gastrointestinal tract morphology and length has been related to diet and phylogeny in African mole-rats (Bathyergidae spp. -Kotzé et al 2010). It is likely diet has influenced gastrointestinal tract morphology and dimensions of stripe-faced and fat-tailed dunnarts, although we did not test long-term outcomes of diets on morphology in the present study.…”

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

“…As in the present study, a more accurate assessment would be to take the relative surface areas of intestinal segments into account. The proportional lengths and basal surface areas has been used successfully in comparing the GIT of other species namely mole-rats (Kotzé et al, 2010) and three insectivorous mammals (Boonzaier et al, 2013). The present study not only took into account the basal surface area but also included the luminal surface area by using a surface enlargement factor similar to a study by Snipes and Kriete (1991) that compared intestinal measurements in 18 mammals.…”