ANATOMY AND ULTRASTRUCTURE OF EXCRETORY SYSTEM OF LIZARD, SCELOPORUS-CYANOGENYS

The anatomy and ultrastructure of the lizard (S. cyanogenys) kidney were studied by light microscopy and EM. The number of glomeruli was counted in serial sections and estimated to be 2000 (in the 2 kidneys). Beginning with the glomerulus and Bowman''s capsule the nephron segments are sequentially: proximal tubule; intermediate ciliated segment consisting of a proximal and distal part; distal tubule, which can be divided into 2 segments, followed by connecting tubule and initial collecting duct. The initial collecting ducts from several nephrons open into the collecting duct. Tubular epithelium in this lizard has similarities to that of other reptiles. The lateral borders do not overlap as in mammals, but interdigitate by fingerlike projections. The length of the nephron segments was measured in disected tubules and the diameter was measured on light and electron micrographs. From these measurements estimates of inner tubular surface area were made. Together with data from physiological studies (Stolte et al., 1976; Schmidt-Nielsen, 1976) the estimated surface area was used to calculate transport rates per unit area across the epithelium. Comparisons of structure and transport rates were made between S. cyanogenys and other reptiles and mammals.