Lymphoid tissues of the snake, Spalerosophis diadema, in the different seasons

Abstract

The thymus in the snake, Spalerosophis diadema, is lymphoepithelial, clearly differentiated into cortex and medulla; it undergoes involution in both winter and summer. During these seasons, the spleen is divided into distinct white and red pulps. In spring and autumn, lymphocytes completely obscure the splenic stroma so that red and white pulp boundaries are obliterated. Gut-associated lymphoid tissue (GALT) is extensively distributed along the entire gastrointestinal tract. Structures resembling Peyer's patches, except in being composed of only two adjacent lymphoid accumulations, are prominent in the small intestine in winter and autumn, while decrease remarkably in number and size in spring and summer (the breeding season). In contrast, the gut-associated aggregates are numerous throughout the year. Differential sensitivity to seasonal variation is suggested as a possible marker for functional lymphocyte populations in reptiles.