Analysis of cell movement in amphimedon embryos by injection of fluorescent tracers.

INTRODUCTIONAlthough attempts to culture prepigmentation-stage embryos (i.e., blastulas and early gastrulas) outside of brood chambers have so far been unsuccessful in Amphimedon, it is possible to manipulate embryos within the brood chamber and follow their development under laboratory conditions. This protocol describes microinjection of lipophilic tracers such as 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) into embryos embedded in their native brood chamber. DiI does not appear to perturb embryonic development and is relatively resistant to photobleaching. As long as care is taken not to damage the fragile embryos during observation and photography, the same embryo can be photographed multiple times, permitting its development to be tracked (up to 4 wk) from early cleavage stages to hatching of free-swimming parenchymella larvae. The embryos or larvae also can be fixed without loss of fluorescence. This method also can be used to deliver other types of solutions to embryos or individual cells of early embryos.