© Zoological Institute, St.Petersburg, 2001 On the taxonomic status of Cerianthus septentrionalis van Beneden, 1923 (Cnidaria: Anthozoa: Ceriantharia) T.N. Molodtsova Molodtsova, T.N. 2001. On the taxonomic status of Cerianthus septentrionalis van Beneden, 1923 (Cnidaria: Anthozoa: Ceriantharia( Zoosystematica Rossica, 10(1): 9-10. The holotype of Cerianthus septentrionalis van Beneden, 1923 is examined. This species was pretended to have two separate sexes. However as result of close investigation, both types of gonads are foundin the holotype. C. septentrionalis is thus a junior synonym of the common North Atlantic species C. lloydii Gosse, 1859 (new synonymy). TN. Molodtsova, P.P. Shirshov Institute of Oceanology, Nakhimovsky pr. 36, Moscow 117851, Russia; e-mail: [email protected] Most of cerianthids are hermaphrodites. Male to 15-20 cm long, and with up to 170-200 very and female gonads occur in the same animal, long marginal tentacles. Large tubes of P: mul­ often in the same fertile mesentery (Carlgren, tiplicatus rise up to 10 cm above the bottom 1912; Molodtsova & Malakhov, 1995). How­ and can serve as a substrate for various marine ever, several species of cerianthids have been animals: polychaetes, sipunculas, crustaceans described as having separate sexes. One of etc. (O'Connor et al., 1977). such odd species, Cerianthus septentrionalis Thus, C. septentrionalis could be considered van Beneden, 1923, was described from a sin­ as a junior synonym of one of these species as gle specimen from the Norway coast. well. However, Beneden (1923) mentioned in . This specimen was determined by Daniel­ his description that his new species differed ssen as C. borealis Danielssen, 1889 and sent from Danielssen 's description of C. boreal is in to Liege to E. van Beneden for furtherstudying several aspects. Therefore, the type material of microanatorriy. After close examination of had to be investigated. the specimen, Beneden (1923) decided that he Danielssen's description contained several was dealing with a new species: "La diagnose questionable points. For example, Danielssen de C. Borealis ne s'applique pas a !'animal que mentioned that marginal tentacles in his spe­ je dois l'obligeance de !'eminent et regrette cies were several times more numerous than naturaliste de Bergen. Je le considere comme mesenteries. All mesenteries in Danielssen's C. nouveau et je le decrirai sous le nom de Ceri­ borealis were fertile, including directive ones. anthus septentrionalis". On the other hand, the cerianthid examined by C. borealis was described by Danielssen Beneden (1923) was very close to C. lloydii (1889) as .having two separate sexes with dif­ Gosse and had two types of mesenteries, but ferent body shape. However, Carlgren (1912) had only one femaletype of gonads. considered these two separate sexes as two dif­ By the courtesy of Dr. Michele Loneux, we ferent common species of ceriantharia viz. had an opportunity to examine the holotype of Cerianthus lloydii Gosse, 1859 and Pachyceri­ C. septentrionalis preserved in Musee de anthus multiplicatus Carlgren, 1912. These two Zoologie de l'Universite de Liege (Belgium) species can be easily distinguished by their ex­ (box 236, slides 21-100) and listed in the in­ ternal appearance. C. lloydii ranges fromrather ventory of the collection as "Cerianthus bore­ small to medium-sized, up to 10 cm long, with a/is Danielssen". It is represented by a series of up to 70 fairly short marginal tentacles, microscope sections, 5 µm thick. Close investi­ whereas P. multiplicatus is a large species, up gation of these microscope slides has revealed a This is publication no. 13 of the project "Regional patterns and biodiversity on deep seafloor of European seas based on Russian and German collections". 10 T.N. Mo/odtsova: On Cerianthus septentrionalis • ZOOSYST. ROSSICA Vol. 10 Figs 1-4. Developing male gonads in the fertile mesenteries of the Cerianthus septentriona/is holotype. tt, male gonads; oo, oocyte. number of groups of negligible cells disposed Liege. The work was financially supported by Volk­ tightly close to ovum cells (Fig. 1 ). Some of swagen Foundation grant project 11/73638. such groups (Figs 3-4) were better developed and separated from gastroderm by their own meso­ References gleal capsules. They have had a strong resem­ blance with a developing male gonad of C. lloydii. Beneden, E. van. 1923. Travaux. postumes d'Edouard Thus, the specimen, described by van van Beneden sur Ies Cerianthaires. Arch. Biol., vol. Beneden, has had two types of gonads, male hors serie. 242 p. and female, respectively. It follows that the Carlgren, 0. 1912. Ceriantharia. The Danish lngolf­ septentrionalis Expedition, 5(3): i-xviii, 1-78. only character separating C. Daniclssen, D.C. 1889. Cerianthus borea/is. Bergens from C. lloydii is invalid. C. septentrionalis Mus. Aarb., 1888(1): 1-12. van Beneden, 1923 is thus a junior synonym of Molodtsova, T.N. & Malakhov, V.V. 1995. Cerian­ C. lloydii Gosse, 1859 (new synonymy). thus /loydii (Anthozoa, Ceriantharia) from the vol­ On the other hand, the order of gonad forma­ canic ecosystem of Kraternaya Bay. I. Morphology tion in van Beneden's specimen seems interest-· and anatomy of adult polyps, geographic distribu­ ing. All cerianthids are considered to be pro­ tion. Zoo/. Zh., 74(10): 5-17. (In Russian). tandrous hermaphrodites (Carlgren, 1912; Tif­ O'Connor, B., Kiinneckcr, G., McGrath, D. & fon, 1987). However, our results show that this Keegan, B.F. 1977. Pachycerianthus multiplicatus feature is not so clear even in the well investi­ Carlgren - biotope or biocoenosis? Europ. mar. gated C. lloydii. There is a strong reason to be­ Biol. Symp., 11: 475-482. Tiffon, J. 1987. Ordre des Cerianthaires (Ceriantharia lieve that in the Norwegian population of C. Perrier 1883). In: Grasse, P.-P. & Doumenc, D. lloydii protogyny can be displayed. (Eds). Traite de zoologie. Anatatnie, systematique, biologie, t. 3. Cnidaires, Anthozoaires, fasc. 3: 1- Acknowledgements 859. Paris, etc.: Masson. I at'n indebted to Dr. Michele Loneux for her help during my stay at Musee de Zoologie de I 'Universite de Received 16 June 2000 .