A stereoscan study of the origin of ciliated cells in the embryonic epidermis ofAmbystoma mexicanum

Abstract

A stereoscan electron microscope has been used to survey the epidermis of axolotl embryos as it becomes ciliated. The observations are consistent with much earlier ones that ciliated cells first occur on the surface of the epidermis at about the time of the closure of the neural folds. The cells are located first in the anterior dorsal region of the embryo at about the one-somite stage. After this they rapidly increase in number and by the three- to six-somite stage ciliated cells, which are isolated from one another, are scattered over the entire surface of the embryo in numbers which approach those of much later stages (18 somites). At the earlier stage, however, most of the ciliated cells lie below the general surface of the epidermis, occupying pit-like depressions. This is in contrast to the later stage when they are raised above the surface. The observations support the view that the precursors of the ciliated cells lie beneath the outer epidermal layer of cells and that the ciliation of the embryonic surface occurs when they move into the outer layer as they complete their differentiation.