ROLE OF DIETARY SUBSTRATES ON INTESTINAL DISACCHARIDASES, DIGESTIBILITY, AND ENERGETICS IN THE INSECTIVOROUS MOUSE-OPOSSUM (THYLAMYS ELEGANS)

In the insectivorous Chilean mouse-opossum, Thylamys elegans (Didelphi dae), acclimated to eating pulp of fruits with sucrose added and live insects, we studied the activity of intestinal disaccharidases, digest ive efficiency, and the effect of each diet on the energy budget. We o bserved activity modulation of the enzymes sucrase, maltase, and treha lase as well as changes in substrate affinities correlated with dietar y carbohydrates. Although this species is able to hydrolyze and assimi late sugars such as sucrose from fruits, it is nevertheless unable to obtain sufficient energy to satisfy its euthermic daily energy require ments and to survive with an exclusive diet of fruits. This situation contrasts with that observed in individuals feeding on insects, for th ey were able to satisfy their maintenance energy requirements with an exclusive diet of insects. The preferences observed in the mouse-possu m for insects over fruits is explained in terms of trade-offs between factors such as digesta transit time, food digestion (including sugars hydrolysis), and food characteristics.