Mitotic behavior and pseudopodial activity of cells in the embryo of Oryzias latipes during blastula and gastrula stages

A simple and rapid method for mechanically isolating cells from fixed embryos of Oryzias latipes was developed, in order to study the mitotic and pseudopodial activities of the cells during early development. Most of the sister cells retain cytoplasmic connections with each other until the prophase of the next mitosis, during the synchronous cleavage stage. The cells of the enveloping layer (EVL), an embryonic epithelium, never extrude pseudopodia. The appearance and the increase and decrease of six types of pseudopodial activity in deep cells during the blastula and gastrula stages are described, and an antagonism between the mitotic and the pseudopodial activities in deep cells has been documented in a quantitative manner. A noteworthy finding in the present study is the occurrence of an elongated intercellular cytoplasmic bridge, which connects members of pairs of postmitotic deep cells from the midblastula stage until the late gastrula stage. The intercellular bridge has been found for the first time in the Oryzias embryo as a result of the newly developed method for the isolation of cells.