Figure 1

Axolotl larva stage 45 and 52. A. Dorsal view of recently hatched axolotl larva (stage 45; forelimb present as limb buds). The pronephroi can be seen as two small bulges behind the gills. B. Schematic representation of the pronephric nephron in the stage 52 larva as revealed from light- and transmission electron microscopy on serial section of plastic embedded tissue. The pronephros consists of an external glomus (gl) and a single renal tubule, which opens into the coelom (co) via two ciliated nephrostomes (ne). In this late larval stage the tubule is divided into two ciliated tubules (ci), two proximal tubule branches (pt), a common proximal tubule, a ciliated intermediate segment (is) and a distal tubule (dt). The distal tubule continues as the pronephric duct (pd), which leaves the confines of the pronephros and empties into the cloaca.