Morphology of the gastrointestinal tract in primates: Comparisons with other mammals in relation to diet
Summary (2 min read)
COMPARATI VE ANATOMY 0~' T il E GASTRO-I NTESTINAL TRACT
- Variation in h istological s tructure effects divisions into stomach , .~mall intestine (duodenu m, jejunum, ileum), and large intestine (caecum and colon).
- The latter are made from relaxed guts immersed in wate r a nd positioned io s how the ma in featu res clearly; a complete reconstruction , impossi ble by photograph, is ach ieved by moving parts of the tract wh ile drawi ng, and adjusting the d imensions of each region after dissection and meas urement.
Frug iuores
- All frugivores supple ment thei r diets wit h varying a mou nts of insects and/or leaves, but have no distinctive st ructural specialization in the g ut, al thoug h its morphology may show considerable vari ation between species.
- Among a rtiodactyls, the pigs have a stomach that is clearly di vided into zones, and in some cases into compa rtments; they have an especially long sma ll intestine, a IMge caecum, and a relatively complex colon, so that the whole tract is about 20 times body length.
- Ma rmosets show some elongation of the fundus, whereas those of cebids are more specia lized with a globular fundus, conical body, a nd cyli ndrical pylorus.
- 6l, Lemur, a nd callitrichids, a nd cebids and most cata rrhines otherwise have three, except for gibbons with fow <H ill , '58).
- The capacious colon of gibbons <Fig. 10) is ind icative of consideta ble leaf co ntent in the diet and its potent ia l for ferme ntation.
Folivores
- Sirenia ns, such as the dugong, ha ve a complex two-ch a mbered stomach, with one part fulfi lling the role of the duodenum ; t hey a lso have a very wide caecum (Grasse, '55) .
- The stomach leads into a long intesti ne with a wide caecum.
- These sa cculations are produced by the reduction of longi tudinal muscle into two or more bands (taen ia).
- The artiodactyl ruminants are well known for their fo ur-chambered stomach (Comline et al. , '68) , which is dominated by the vast rumen, divided into dorsal and ventral sacs by muscular pillars, and covered by kera t inized sq uamous epithelium with papillae of varying size and shape (Fig. 16 ).
Methods
- One-hundred forty-eight specimens were caught in their natura l habitat by hun ters dur ing pes t cont rol opera t ions or by local people for food; 29 a n ima ls, mos tly pr imates, died in captiv ity, from illness or old age.
- Specimens were weighed intact, which was not a lways possible in the fie ld, and their lengths were measured from bregma to ischium a nd from tip of nose to base of tail.
- Upper left, t he stomach (part1ally d1stended w1th wat er) displayed to show the large sac, the gastr ic tube (on t he n ght), and the pylorus (lower left).
- Thus, volumes have been recalcu lated along these lines <Table 4), yielding values one-third less on average.
- The categories of "fa univore," "f1 ug ivore," a nd "fo livore" a re esta blished a ccord ing to str uct ural disconti nui ties, and at this stage they can be no more tha n suggest ive of diet.
CO EFFICIENT of GUT DIFFERENT IATI ON
- Nevertheless, these crude a rcal measures seem to prov ide the best ind icators of dietary ada ptation.
- Correlations within each g rou p, however, a re less close tha n in the analys is of volumes, and ca lcula tion of the 95'# confidence interva ls produces extens ive overla p between the difTerent regression lines.
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Cites background from "Morphology of the gastrointestinal ..."
...Variation between primate species in digestive retention times (Lambert 1998, 2002; Milton and Demment 1988), gut surface area and volume (Chivers and Hladik 1984; Kay and Davies 1994), relative lengths of portions of the gut (Chivers and Hladik 1980; 1984), and gut microbial communities (Bauchop 1971; Bauchop and Martucci 1968) correlate well with dietary specializations....
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...…2002; Milton and Demment 1988), gut surface area and volume (Chivers and Hladik 1984; Kay and Davies 1994), relative lengths of portions of the gut (Chivers and Hladik 1980; 1984), and gut microbial communities (Bauchop 1971; Bauchop and Martucci 1968) correlate well with dietary specializations....
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