Studies on the gastrulation of amphibian embryos: Ultrastructure of the migrating cells of anurans.

In order to investigate the ultrastructure of the migrating cells in anuran gastrulae, three anurans, which belong to three different genera, were observed with transmission electron microscopy supported by light microscopy of the 1 μm sections and scanning electron microscopy. Fine filopodial cell processes, as well as cell processes probably flattened against the inner surface of the blastocoel wall, were formed by the migrating cells. Blebs and lobopodial cell processes were frequently observed inBufo, sometimes inXenopus, but not observed inRana. Microfilaments were observed in the cell processes. Focal close contacts, probably having adhesive properties, were made between the migrating cells and the inner surface of the blastocoel wall. These observations suggest that the cells migrate along the inner surface of the blastocoel wall by forming filopodia and pseudopodia flattened against the wall. The role of the blebs and lobopodial cell processes requires more investigation.