A. Abzhanov et Tc. Kaufman, Embryonic expression patterns of the Hox genes of the crayfish Procambarusclarkii (Crustacea, Decapoda), EVOL DEV, 2(5), 2000, pp. 271-283
Higher crustaceans (class Malacostraca) represent the most species-rich and
morphologically diverse group of non-insect arthropods. The superorders Eu
carida and Peracarida, two large groups that separated over 350 million yea
rs ago, encompass most malacostracan diversity. Recently, the Hox genes of
the peracarid woodlouse Porcellio scaber (Isopoda) were shown to be express
ed in domains that coincide with morphological boundaries of body tagmata,
which differ from those in insects (Abzhanov and Kaufman 1999a,b). Moreover
, observed changes in Hox expression domains during ontogeny correlate with
morphological remodeling, such as a transformation of the first thoracic l
eg into mouthpart maxillipeds, which occurs in the trunk of the embryo. Dec
apods have a different modification of the malacostracan bodyplan, with up
to three pairs of maxillipeds and extensive fusion and cephalization of the
thorax. Here we describe expression patterns of the trunk Hox genes Scr, A
ntp, Ubx, abd-A and cad in the eucarid crayfish Procambarus clarkii(Decapod
a). We find that the crayfish expression patterns, for the most part, resem
ble those of the woodlouse Porcellio scaber(Isopoda), but are more modulate
d and complex. Nevertheless, as in Porcellio the boundaries of the Hox expr
ession domains do correlate with morphological features and their modulatio
ns to transformations in the embryo. Thus we propose that the trunk Hox gen
es were likely important in the evolution of and currently play an essentia
l role in the development of the complex decapod bodyplan.