Single cell labeling in medaka embryo. (A) Instruments for single cell labeling. Embryonic cells are labeled by an electroneedle under a fixed stage microscope. Oscilloscope monitors the current and voltage. The positions of labeled cells are recorded by fluorescent microscopy. (B) Magnification of the stage. Embryo is placed on the silicon mount and oriented under 10 or 40 lens. Silicon mount is filled with BSS + PS buffer and connected with ground electrode. (C) Illustration of the embryo. Embryo is mounted with animal pole up. Electroneedle is filled with rhodamine dye and penetrated into a cell of interest. Electrical oscillations generated by the amplifier cause migration of the anion-charged dye.