MOTILITY AND LOCOMOTION OF EMBRYONIC CELLS OF THE MEDAKA, ORYZIAS LATIPES, DURING EARLY DEVELOPMENT

The motility and locomotion of embryonic cells of the medaka, Oryzias latipes , were studied in situ with time-lapse cinematography.
In the early morula (128-cell stage), the surface of the blastomeres begins to undulate gently. By the early blastula stage, these undulations increase gradually in amplitude, and blebs appear. These blebs protrude and retract rapidly. In the mid-blastula stage they are found in most of the blastomeres. Some are found adhering to the surfaces of other cells. Blebs often expand into elongate lobopodia. Cell locomotion is first evident in the mid-blastula stage and continues throughout gastrulation and afterward. The cells move in the direction of the protrusion. In the late blastula a number of blastomeres locomote in random directions. In the thickening stage, when blastoderm epiboly begins, the cells with lamellipodia or elongate filopodia increase gradually in number, and in the early gastrula most cells change into this form. The motility, rate of movement, and mode of locomotion of embryonic cells during early development are described in detail.