molecular studies indicate that nematodes and other
PSEUDOCOELOMATES probably did not branch from the
base of the bilaterian tree as in the traditional view,
but form one CLADE (the Ecdysozoa) with moulting
protostomes, such as Drosophila 42. Given these new
phylogenetic relationships, the absence of Hh and
JAK/STAT signalling components in the C. elegans
genome represents a gene loss, as these two pathways
are present in Drosophila and in deuterostomes. So,
the phylogenetic placement of organisms has important
consequences on how the evolutionary pattern of
signalling pathways is interpreted.