Ultrastructure and functional morphology of the dorsal organs in Scoloplos armiger (Annelida, Sedentaria, Orbiniida)

Abstract Annelids and particularly polychaetes possess a great variety of sensory organs respond to numerous stimuli. Although eyes nuchal are comparatively well studied, the so-called dorsal among lesser-known sense in aquatic annelids. Moreover, they known be restricted only two out approximately 80 families polychaetes—Orbiniidae Spionidae—which not closely related. These have been regarded as segmentally repeated latter taxon, but Orbiniidae, data lacking, although it is that occur almost along entire trunk except for anterior-most segments. Furthermore, organ ultrastructure uniform many polychaete species, comparative investigation has conducted Orbiniidae. To bridge this gap, we examined an intertidal population widely distributed species Scoloplos armiger . completely identical, show high degree correspondence specimens. both correspond general structure organs. They comprise ciliated supportive cells bipolar receptor innervated directly from brain. The form subcuticular spaces olfactory chambers apically protected by specialized microvilli house processes—cilia microvilli—of monociliated cells. Therefore, can concluded also identical However, despite with spionids, convergent evolution taxa appears most parsimonious interpretation.