Scanning electron microscopic investigation of general morphology and ciliary structures in Nereilinum murmanicum Ivanov, 1961 (Annelida, Siboglinidae)

The general morphology of the body, including the distribution of putative sensory ciliary cells, was studied using scanning electron microscopy (SEM) in the siboglinid Nereilinum murmanicum Ivanov, 1961 collected from the Barents Sea and at a new, deeper locality in the Greenland Sea outside the known range of this species. The fine features of cuticular structures in N. murmanicum, including the bridle and cuticular plaques from different parts of the body, were described for the first time. Since we have previously shown in the closely related siboglinid Oligobrachia haakonmosbiensis Smirnov, 2000 using SEM and confocal laser scanning microscopy (CLSM) that all epidermal cilia except for the ventral ciliary band belong to sensory cells, we consider all ciliary structures detected in N. murmanicum as sensory. The tentacles, clusters of ciliary cells along the dorsal furrow, areas around the openings of the multicellular glands, papillae, and the ciliary patch located on the cephalic lobe at the base of the tentacles can be regarded as specialized sensory areas. Based on our current knowledge of sensory structures in annelids, a number of assumptions were made about possible functional characteristics of putative sensory structures in siboglinids.