SEASONAL-CHANGES IN DIGESTIVE ENZYMATIC-A CTIVITY IN THE SMALL CHILEAN MARSUPIAL THYLAMYS-ELEGANS - INTESTINAL DISACCHARIDASES

It has been suggested that carnivorous vertebrate species are unable t o regulate digestive attributes, such as nutrient transport and enzyme activities, when exposed to different diets. However, we have previou sly shown that the mouse-opposum Thylamys elegans, a small insectivoro us marsupial inhabiting the Mediterranean environments of central Chil e, is able to change its dissacharidase activity levels, in response t o differences in the chemical composition of the food items. The absen ce of such digestive constraint suggest that T. elegans may behaves op portunistically in response to changes in the environmental availabili ty and abundance of their trophic resources. Consequently, all else be ing equal, we expect that seasonal change in intestinal dissacharidase s activities (i.e., sucrase, maltase and threalase) tend to be correla ted with seasonal changes in fruit and insect availability. We detecte d significant differences between the activities of such dissacharidas es between winter and summer. We hypothesize about the mechanisms of r egulation and expression of such dissacharidases, and discuss the phys iological, behavioral and ecological consequences of such mechanisms.