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Figure 2. Pronephric duct (PND) extension in Xenopus laevis. In situ hybridization with Xpax2 reveals the developing nephric system in stage 28 (A) and stage 34 (B) embryos. In A, the posterior PND tip is indicated at the level of somite IX. PND formation at this stage is entirely due to local segregation of duct tissue from mesoderm ventral to somites IV-IX. In B, migration has contributed to PND formation from somites IX-XIV, and the rectal diverticulum (concave arrow) is extending rostrally to meet and fuse with the PND at the level of somite XIV. Morphogenesis of rectal diverticulae is not well understood. p, pronephros; posterior tips of the PNDs are indicated by triangular arrows. Anterior is to the right, and dorsal is to the top in all figures. |
