Cell lineage and cell fate in crustacean embryos--a comparative approach.

Malacostracan crustaceans undergo a complex and stereotyped cleavage pattern during formation of and segmentation in their post-naupliar germ band. This pattern has been studied in several malacostracan representatives with respect to morphogenesis and expression of the engrailed gene. Although this cell lineage pattern is specific and invariant in each species, comparative analyses reveal subtle differences between different parts of individual germ bands and between germ bands of different species. We conclude that despite the elaborate cleavage pattern, cell fate specification is not closely linked to cell lineage. Furthermore, some aspects of the evolutionary alterations of germ band formation and segmentation in annelids and arthropods are discussed.