The lobate ctenophore Mnemiopsis leidyi is an emerging model system for evolutionary and developmental studies.  Ctenophores possess a bi-radial body plan that includes nerve cells, ectodermal and endodermal germ layers, well defined muscle cells, and two axes of planar symmetry.  The nervous system is comprised of derived neural cell types organized in a diffuse, but structured, network with foci associated with the apical organ and the tentacles.  The principal synapomorphies of the group are modified giant cilia comprising the characteristic ‘ctene’ rows used for locomotion and specialized adhesive cells associated with the tentacles termed colloblasts.  Ctenophores also have temporally rapid regenerative capacity.  This significant morphological complexity requires the specification and patterning of a diverse set of differentiated cell fates during embryogenesis as well as via regeneration in the adult.

Mnemiopsis leidyi