LOCATION AND ULTRASTRUCTURE OF PRIMORDIAL GERM CELLS (PGCs) IN AMBYSTOMA MEXICANUM

Abstract

Stages 23-47 of A. mexicanum were studied. PGC were found in spaces between the endodermal cell mass and the lateral plate mesoderm at stages 23-35. Some of the PGC at stage 35, and most of them at stages 40 and 42, were located near the Wolffian duct. At stages 46 and 47 all the PGC were situated in the genital ridges. Cilia, which have hitherto never been reported in PGC, were occasionally seen in PGC of Ambystoma from stage 23 until stage 46. No germinal plasm was found in the PGC prior to stage 40. Specific structures or nuage material, corresponding to germinal granules or their derivatives in Xenopus, were 1st recognized in the vicinity of the nucleus at stage 40. Between stages 40-46, the amount of nuage material markedly increased. It was finally localized mainly in intermitochondrial spaces. A possible transfer of material from the nucleus to the cytoplasm or vice versa through nuclear pores was 1st noticed at stage 40, the material concerned being quite similar in ultrastructure to the nuage material.