Gross intestinal morphometry and allometry in primates

• Published in: American journal of primatology Vol. 81; no. 8; pp. e23035 - n/a
• Main Authors: McGrosky, Amanda, Meloro, Carlo, Navarrete, Ana, Heldstab, Sandra A., Kitchener, Andrew C., Isler, Karin, Clauss, Marcus
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.08.2019
• Subjects: Allometry; anatomy; Animals; Body mass; Body Weight; Carnivora; Colon; Confidence intervals; Correlation analysis; Diet; digestive tract; Evolution; Intestine; Intestines - anatomy & histology; Large intestine; Leaves; Mammals; Monkeys; Monkeys & apes; Morphometry; Organ Size; Phylogeny; primate; Primates; Primates - anatomy & histology; Scaling; Small intestine; Species Specificity; Statistical analysis; Terrestrial environments; Vegetable fibers; primate; phylogeny; diet; digestive tract; anatomy
• ISSN: 0275-2565; 1098-2345
• DOI: 10.1002/ajp.23035

Although it is generally assumed that among mammals and within mammal groups, those species that rely on diets consisting of greater amounts of plant fiber have larger gastrointestinal tracts (GIT), statistical evidence for this simple claim is largely lacking. We compiled a dataset on the length of the small intestine, caecum, and colon in 42 strepsirrhine, platyrrhine, and catarrhine primate species, using specimens with known body mass (BM). We tested the scaling of intestine length with BM, and whether dietary proxies (percentage of leaves and a diet quality index) were significant covariates in these scaling relationships, using two sets of models: one that did not account for the phylogenetic structure of the data, and one that did. Intestine length mainly scaled geometrically at exponents that included 0.33 in the confidence interval; Strepsirrhini exhibited particularly long caeca, while those of Catarrhini were comparatively short. Diet proxies were only significant for the colon and the total large intestine (but not for the small intestine or the caecum), and only in conventional statistics (but not when accounting for phylogeny), indicating the pattern occurred across but not within clades. Compared to terrestrial Carnivora, primates have similar small intestine lengths, but longer large intestines. The data on intestine lengths presented here corroborate recent results on GIT complexity, suggesting that diet, as currently described, does not exhaustively explain GIT anatomy within primate clades. Research Highlights In a large sample of primates, intestinal length measurements show poor correlation with diet. Lemurs have a comparatively long caecum and old world monkeys a comparatively short one, with new world monkeys in between. Compared with terrestrial Carnivora, primates have similar small intestine lengths, but longer large intestines.