DIFFERENTIAL EFFECT OF SEASONAL-VARIATION ON LYMPHOID-TISSUE OF LIZARD, CHALCIDES-OCELLATUS

In the lizard, Chalcides ocellatus, the thymus and spleen are similar to those of mammals except that lymphoid tissue of the lizard's thymus and spleen is atrophic in winter. Lizards also possess numerous dense lymphoid nodules associated with the entire gut mucosa and the submucosa of the ileo-colon junction and the caecum. A peculiar lymphoepithelial macroorgan, resembling the bursa of Fabricius occurs in the colon. Oesophageal nodules are few in winter, but their number and size increase in spring and summer and then decrease in autumn. In contrast, lymphoid tissue of the stomach, small and large intestines does not appear to be affected by seasonal variation. Dichotomy of lymphocyte populations in lizards is suggested. © 1978 Pergamon Press.