Expression of the transcription factor genes brachyury, Tbx2/3 and sall is characterized in
detail for the first time in an indirectly developing spiralian with a feeding trochophore. In …

Many regulatory genes appear to be utilized in at least superficially similar ways in the
development of particular body parts in Drosophila and in chordates. These similarities have …

Polyplacophorans, or chitons, are an important group of molluscs, which are argued to have
retained many plesiomorphic features of the molluscan body plan. Polyplacophoran …

Animals with the simplest bodies: sponges and placozoans. These organisms have interior
spaces and a few cell types, but in contrast to the eumetazoans (all other categories of …

Polyclad flatworms offer an excellent system with which to explore the evolution of larval
structures and the ecological and developmental mechanisms driving flatworm and marine …

Hexapoda not only constitutes the largest taxon in the biological world; its representatives
are also the best-studied invertebrates. This chapter will give an overview of general …

Annelids, or segmented worms, constitute one of the major animal phyla. The modular
organization of the segmental body plan has endowed a high degree of constructional …

'Trochophore'is commonly used to designate larvae with opposed-band feeding and a
particular set of ciliary bands. The trochophore has been proposed to represent the …

The non-bilaterian animals comprise organisms in the phyla Porifera, Cnidaria, Ctenophora
and Placozoa. These early-diverging phyla are pivotal to understanding the evolution of …

The quest for the first bilaterian organisms is the biggest riddle in metazoan evolution and in
understanding the evolution of developmental mechanisms. Recent molecular work has …