Genital and Pelvic Kidney Renal Corpuscles of the Red-spotted Newt, Notophthalmus viridescens (Amphibia, Urodela, Salamandridae)

Salamanders possess a bipartite kidney: a caudal portion contains nephrons that primarily function in urine formation (pelvic kidney nephrons) and a cranial portion where nephrons also serve as sperm conduits (genital kidney nephrons). Nephrons of these two kidney regions were examined microscopically in Notophthalmus viridescens. No microstructural differences were observed between the filtration barriers of renal corpuscles from pelvic and genital kidney nephrons. However, pelvic kidney renal corpuscles were significantly larger than genital kidney renal corpuscles and possessed a much more developed, and vascularized, glomerular structure. Furthermore, whereas filtrate was easily observed in the urinary space of pelvic kidney renal corpuscles, the urinary space of genital kidney renal corpuscles did not bind with stains used for examination with transmission electron microscopy. This finding corresponds with the previous lack of filtrate observed in the proximal tubules of genital kidney nephrons in comparison to copious filtrate in pelvic kidney proximal tubules. These results may indicate a lack of urine forming function in the genital kidney nephrons.