Structure and evolution of the cuticular plaques of pogonophorans (Annelida: Pogonophora)

Abstract

The structure and evolutionary significance of the pogonophoran trunk cutucular plaques are studied. All pogonophoran cuticular plaques, including those in the bridle, have the same basal set of the structural characters. The structure, origin and arrangement pattern of the cuticular plaques show that they are apomorphies of Pogonophora. These structures, unlike setae, are not derived from any ancestor cuticular structures. The arrangement patterns of the cuticular plaques are quite variable in different body parts but nowhere repeat the neuro-notopodial scheme of the annelid setae arrangement. In various body regions of pogonophorans, including the bridle, the cuticular plaques underwent the similar evolutionary transformations.