Gut morphology and rate of passage of fungal spores through the gut of a tropical rodent, the giant white-tailed rat (Uromys caudimaculatus)

Gut morphology and rate of digesta passage through the gut in captive giant white-tailed rats (Uromys caudimaculatus) were investigated. Rate of passa ge was measured using a solute marker (Co-EDTA), a marker of large particle s (Cr-mordanted plant cell walls) and spores of the ectomycorrhizal fungus Pisolithus spp. The mean retention time (MRT) of fungal spores in the whole gut (48.4 +/- 6.0 h), was long in comparison to that found in other rodent s of similar body mass and was intermediate to MRT of the solute marker (45 .4 +/- 8.8 h) and the large particle marker (55.5 +/- 7.2 h). Thus, retenti on of spores is likely to be little affected by being free or attached to p ieces of ingested fruiting bodies. The stomach is unilocular and hemiglandu lar and contains a large fundic diverticulum lined entirely by non-glandula r squamous epithelium. The significantly longer MRT for the large particle marker than the solute marker suggests that some selective retention of par ticles takes place, probably in the fundic diverticulum of the stomach. We suggest that the large fundic diverticulum may function in storage and poss ibly increased digestive efficiency of starchy food items, and in retaining spores, especially when still attached to fruiting bodies.