LIGNOT, JH; HELMSTETTER, C; SECOR, SM*; CEPE-CNRS, Louis Pasteur University, France; CEPE-CNRS, Louis Pasteur University, France; University of Alabama, Tuscaloosa, USA: Structural changes of the intestinal epithelium with fasting and feeding for the Burmese python (Python molurus)

The small intestine of the Burmese python (Python molurus) rapidly up- and down-regulates performance at the beginning and completion of each meal. To characterize in detail the morphological plasticity of the python’s intestine associated with these regulatory responses, we used transmission electron microscopy (TEM) and conventional (CSEM) and environmental (ESEM) scanning electron microscopy to observe postfeeding changes in enterocyte structure. Epithelial samples removed from the proximal, middle, and distal regions of the small intestine were analyzed for snakes fasted and up to six days of digestion. Within hours after feeding, the intestinal mucosa transforms from a layer of pseudostratified epithelium with hypotrophic enterocytes and shortened microvilli to a monolayer of hypertrophic cells with microvilli that have lengthened by 4-fold. Hypertrophied enterocytes with elongated microvilli are maintained during digestion, with the addition of lipid droplets that begin to appear within the enterocytes within one to two days. ESEM reveals the extrusion of lipid droplets largely from enterocytes at the villus tips predominately for the proximal small intestine. At the same time, calcium-rich annulated spheroids appear at the apical ends of the proximate and middle enterocytes. These spheroids, ranging in diameter between 0.5 and 8 �m, may enter the enterocytes from the lumen, suggestive that they would originate from the meal.To be described are the exact source of the spheroids, the mechanisms by which they enter or exit the cells, and their physiological role.