A fate map of superficial and deep circumblastoporal cells in the early gastrula of Pleurodeles waltl.

We have determined the fate of presumptive mesodermal cells in the early Pleurodeles waltl gastrula. We labeled all cells in a gastrula with RLDx cell lineage tracer and superficial cells with 125I and then grafted small pieces of the marginal zone orthotopically into unlabeled host embryos. Labeled progeny were identified in sectioned embryos at the tail bud stage. The use of double-labeled grafts allowed us to study the relative contributions by superficial and deep cells to different derivatives. We found that the presumptive regions are generally distributed according to classical fate maps for urodeles but that the boundaries between presumptive regions are indistinct, due to extensive intermingling between cells at the edges of grafted regions. We have shown that there is a high dorsal to low ventral gradient of mixing between superficial and deep cells.