A histology-free description of Tetrastemma cupido sp. nov. (Nemertea: Eumonostilfera) from Sagami Bay, Japan

ABSTRACT

We provide a histology-free description of the eumonostiliferous hoplonemertean Tetrastemma cupido sp. nov. based on specimens collected subtidally at a depth of 100 m in Sagami Bay, Japan. In T. cupido sp. nov., the ocelli are arranged in two, anterior and posterior, pairs of clusters, each consisting of up to eight and four ocelli, respectively. This feature is unique to T. cupido sp. nov. among ∼110 congeners in the genus Tetrastemma Ehrenberg, 1828, where the ocelli are unexceptionally four in number. The generic affiliation of the new species was confirmed with a molecular phylogenetic analysis based on partial sequences of cytochrome c oxidase subunit I, 16S rRNA, 18S rRNA and 28S rRNA genes among 31 species of eumonostiliferans. In the resulting tree, T. cupido sp. nov. was nested in a clade comprised of 11 species of Tetrastemma including the type species Tetrastemma flavidum Ehrenberg, 1828. Tetrastemma cupido sp. nov. is morphologically similar to Amphiporus superbus (Girard in Stimpson W. 1854. Marine Invertebrata of Grand Manan. Smithsonian Contr Knowl. 6:5–67), but can be distinguished from the latter by having a mid-dorsal white stripe.

Publication LSID: lsid:zoobank.org:pub:C58863AC-6176-453C-94EA-BD79D413EF41

KEYWORDS:

• JAMBIO
• marine invertebrate
• Monostilifera
• Nemertea
• Pacific
• Tetrastemmatidae

Acknowledgements

We thank Professor Alexei V. Chernyshev (A.V. Zhirmunsky National Scientific Centre of Marine Biology, Russia) for providing us with valuable suggestions and unpublished data for the present study; Dr Hiroaki Nakano (Shimoda Marine Research Centre, University of Tsukuba), Mr Mamoru Sekifuji and Ms Michiyo Kawabata (MMBS) and the other participants in the 12th and 19th JAMBIO Coastal Organism Joint Surveys in Sagami Bay for their support in collecting specimens; Dr Hiroshi Namikawa (National Museum of Nature and Science), Dr Yuji Ise (Tropical Biosphere Research Centre, University of the Ryukyus), and Dr Norio Miyamoto (Japan Agency for Marine–Earth Science and Technology) for collecting material in 2006; Mr So Abe (Yokohama Hakkeijima Seaparadise) for conducting a dredging survey in 2018, where one of the paratypes was collected.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was partially funded by the Japan Society for the Promotion of Science [grant number: 17K07520] for H. Kajihara.