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 passage was measured using a solute marker (Co-EDTA), a marker of large particles (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 rodents 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, retention of spores is likely to be little affected by being free or attached to pieces of ingested fruiting bodies. The stomach is unilocular and hemiglandular and contains a large fundic diverticulum lined entirely by non-glandular squamous epithelium. The significantly longer MRT for the large particle marker than the solute marker suggests that some selective retention of particles takes place, probably in the fundic diverticulum of the stomach. We suggest that the large fundic diverticulum may function in storage and possibly increased digestive efficiency of starchy food items, and in retaining spores, especially when still attached to fruiting bodies.