Evolution and Development of Segmented Body Plan Revealed by engrailed and wnt1 Gene Expression in the Annelid Alitta virens

Segmentation is one of the most striking features of bilaterians, and understanding its mechanisms provides insights into the evolution of body plans. In annelids, segmentation occurs at different developmental stages through a variety of processes, yet the molecular pathways remain underexplored. Aiming to compare segmentation patterns in ontogeny and phylogeny, we analysed the expression of Avi-en (homologous to engrailed) and Avi-wnt1 in the nereidid polychaete Alitta virens. Using in situ...