The Morphology of the Gastrointestinal Tract and Food Transit Time in the Fruit Bats Pteropus Alecto and P. Poliocephalus (Megachiroptera).

Abstract

The gastrointestinal tract of the fruit bats Pteropus alecto and P. poliocephalus was investigated by dissection and by light and electron microscopy. Food transit time was recorded for cultivated fruits and roentgenograms were obtained from bats given barium-labelled food. Minimum food transit time varied from 12 to 34 min for cultivated fruits but this was extended to 44 min by the addition of Ba. There was little variation between the gastrointestinal tracts of the two species. The stomach has an elongated terminal part, and expanded cardiac and fundic regions which display a relatively thick gastric mucosa and abundant parietal cells. A caecum and appendix are absent. Well developed villi of the small intestine feature absorptive cells with relatively large microvilli (less than or equal to 5.7 mu m tall). The intestinal mucosa displays more goblet cells in P. poliocephalus than in P. alecto. The large intestine is short and features prominent longitudinal folds; the mucosa undergoes a gradual transition, with number and size of villi decreasing in the distal part of the intestine. Although a distinct rectum cannot be distinguished, the colonic mucosa is restricted to a short segment, slightly shorter in P. poliocephalus than in P. alecto. The study highlights several anatomical features of the gastrointestinal tract, which probably allow fruit bats to process large quantities of food rapidly. The advantage of this to a flying mammal is a reduction in bulk carried in the digestive tract, enabling it to reduce the energy expenditure associated with foraging flights.