Lisova E.D., Vortsepneva E.V
Rhinophores are important chemosensory cephalic organs in nudibranch mollusks. Morphology of rhinophore are important taxonomic features. In this regard, the external structures of the rhinophore have been described for many species. However, their general morphology has so far been studied fragmentarily. Many details of the internal morphology have not been studied in detail at all. In this work, for the first time, the structure of the Onchidoris muricata rhinophore is described in detail.
The collection of material was carried out in the Kandalaksha Bay of the White Sea. The samples were examined by light, scanning electron microscopy, and morphological dissections were also performed.
The large nerve, muscles and the lymphatic cavity are located in the rhinophore center. The large nerve of the rhinophore has branches that bifurcate at the end. The muscular system of the rhinophore is represented by longitudinal muscles retractors, as well as transverse thin strands. The lymphatic canal does not have its own wall and is limited by the rhinophore structural element. The rhinophore wall is reinforced with a large number of spicules. The morphology of the rhinophores spicules differs significantly from the spicules of their body. The spicules are thinner and more curved. The spicule complex of monoaxones and multiaxones looks like a bonfire from a log cabin. A framework of four spicules located along each rhinophore extends around the central part of the rhinophore. Two spicules run directly into the fold of the rhinophore. The rows of spicules are circumferentially displaced relative to each other. The contraction of the rhinophore occurs with the participation of the retractor muscles, the relaxation is passive due to the injection of hemolymph
Our data of the structure of the rhinophore supplement the existing and significantly expand the understanding of the structure of the spicule complex of nudibranchs.
Acknowledgments: This research was carried out as part of the Scientific Project of the State Order of the Government of the Russian Federation to Lomonosov Moscow State University, No. 121032300121-0. Support was provided by the Russian Science Foundation No. 21-14-00042.