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A new fate map for Salmo gairdneri

1973; Wiley; Volume: 184; Issue: 1 Linguagem: Inglês

10.1002/jez.1401840105

1097-010X

William W. Ballard,

Congenital heart defects research

Abstract Chalk granules implanted among the cells of the stage 7 blasto‐disc are carried along with the cells to final location in the differentiating tissues and organs. The results, more often than not, are inconsistent with predictions suggested by an earlier fate map for Salmo (Pasteels, (36). Granules vertically thrust into a given spot on the blastodisc are usually carried to various levels of the trunk and to a variety of organs, presumably because cells at different depths of one spot and at different distances from the center are moving at different rates. Data from hundreds of such implants are assembled into charts showing the areas from which cells are drawn, to contribute to formation of the endoderm, notochord, five separate zones of the central nervous system, the head mesoderm, anterior and posterior trunk somites, tail somites, lateral plate, and heart. Using evidence of the overlapping and intergradation of these areas, as well as evidence from vital dyes when allowed to penetrate to various depths of the pregastrular blastodisc, a three‐dimensional fate map is synthesized for Salmo gairdneri , which is very different from the earlier map, but consistent with the previously reported patterns of morphogenetic movements in this species (Ballard, (73b). In contrast with the gastrulation of amphibia and birds, Salmo germ layers arise without any invagination, and there is at no time an anterior mesoderm‐free area. Previous efforts to generalize upon vertebrate gastrulation and its evolution within the phylum seem to have been premature.