Cell type specification in the crustacean Paryhale hawaiensis

Animal embryos specify four early cell types. Determining the underlying mechanism is one central question of developmental biology. At present, it is studied how the crustacean Parhyale hawaiensis manages such developmental program at the eight-cell stage. Specification of germ cells, e.g., depends on the genes vasa and nanos, however, in a different way than in Drosophila melanogaster , demonstrating change of gene function during evolution.