Medusae of the genus Rhabdoon (Hydrozoa: Anthomedusae: Tubularioidea) in the Arctic Ocean

Abstract

One hundred and three specimens of juvenile and mature one-tentacle, relatively small-sized hydromedusae of unclear systematic position were found in the zooplankton collections from the Arctic Ocean. Examination of the mature specimens led to the conclusion that their morphology fits with the last diagnoses of the genus Rhabdoon (Anthomedusae) and that they belong to the species named here as R. reesi. The study of the morphology and cnidome composition of immature medusae suggested them to be young stages of the same species. The comparative study of these juvenile forms with Yakovia polinae, the medusae described previously from the Arctic as a new genus and new species, suggested Y. polinae to be a junior synonym of R. reesi. The distribution of R. reesi in the Arctic Ocean is mapped according to recent and historical records.

Keywords:

• Arctic ocean
• one-tentacle medusae
• cnidophores
• genus Rhabdoon

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

We are grateful to Drs I. Kerzner, D. Calder and W. Vervoort for their useful advice regarding nomenclatural problems, and Dr. W. Pulawski for the information about the distribution of “Taxonomic Guides” in the US libraries. Thanks also to Dr Olga Kosobokova who helped to find the unpublished Masters Thesis of Shirley (1966). T. Scherzinger and B. Stroscher (AWI) assisted during the zooplankton sampling. Olga Sheiko helped with nematocyst investigations, A. Novigatsky (IO RAS), Sergey Grebelnyi and V. Dzurinsky (ZIN RAS) with the computer treatment of illustrations. We are thankful to every of the reviewers – Drs F. Boero, A. Brinckmann-Voss and unnamed reviewers for the useful advice and important corrections. This study contributes to the Arctic Ocean Diversity Project (ArcOD) of the Census of Marine Life Project. The work of SSD was supported by Project no. 16 “Investigation of Antarctic”, the Program “World Ocean”; KKN was supported by the Russian Foundation for Basic Research, grant no. 03-05-64871.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

1. Seven issues of “Taxonomic Guides to Arctic Zooplankton” were prepared under the direction of John L. Mohr and distributed in 1970–1971 by the Department of Biological Sciences of the University of Southern California in Los Angeles. Part II, containing the paper by Shirley & Leung (1970), is a Technical Report bearing on the title page a statement that its distribution is not limited and a stamp “This document has been approved for public release and sale; its distribution is unlimited”. The paper is cited in Vervoort (1995) and Brunel et al. (1998). Professor W. Pulawski (Californian Academy of Sciences) informed us: “[Our librarians] have found that the Guides are present in 10 USA libraries. Part II is listed under all of them”. W. Pulawski specifically confirmed the presence of Part II in the library of the American Museum of Natural History, Washington DC. Hence, the guide by Shirley & Leung (1970) conforms to the criteria of publication (Code, Article 8.1) as it was distributed rather than copied on demand. The method of reproduction was apparently mimeography, as this method is cited for other contemporary publications of the department authored or co-authored by Shirley.