Selective retention of fluid digesta in the hindgut of bandicoots and other marsupial caecum fermenters.

Many small hindgut fermenters have a mechanism in the proximal colon that separates fluid and/or bacteria from large particles, and excretes the large particles relatively rapidly. The fluid and/or bacteria are retained in the caecum, which concentrates digestive effort in that region of the hindgut and improves overall digestive efficiency. Previously observed among marsupials only in arboreal marsupials, selective retention of fluid digesta has recently been reported also in bandicoots, small terrestrial omnivores. The separation mechanism operated independently of the nature of the diet, indicating that it is probably an important factor in the ability of bandicoots to switch between insect and plant foods, and thus to exploit nutritionally unpredictable environments. Results are discussed in relation to possible locations in the marsupial hindgut of the pacemaker that in eutherians has been shown to initiate retrograde movement of fluid and small particles in the proximal colon towards the caecum.