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| [A-D] Okenia longiductis Okenia problematica Pola, Paz-Sedano, Macali, Minchin, Marchini, Vitale, Licchelli & Crocetta, 2019 |
Abstract
The precise number of Okenia taxa inhabiting the Mediterranean Sea, as well as their general taxonomy, varies according to different specialists. So far, eight valid species have been reported from the area: Okenia aspersa (Alder & Hancock, 1845), Okenia cupella (Vogel & Schultz, 1970), Okenia elegans (Leuckart, 1828), Okenia hispanica Valdés & Ortea, 1995, Okenia impexa Er. Marcus, 1957, Okenia leachii (Alder & Hancock, 1854), Okenia mediterranea (Ihering, 1886), and Okenia zoobotryon (Smallwood, 1910). Of these, only three (O. elegans, O. hispanica, and O. mediterranea) have their type localities in the Mediterranean Sea, whereas the others were described from different biogeographic areas and later included in the Mediterranean biota. We carried out a review on Mediterranean Okenia species through an integrative approach, based on a wide literature search and a morphological and molecular analysis of available type material and samples collected recently. The present study confirmed the presence of O. aspersa, O. elegans, O. hispanica, and O. mediterranea in the Mediterranean Sea, although leaving remaining questions about some of those taxa. The distribution of O. cupella, O. impexa, and O. zoobotryon is limited to the western Atlantic, and of O. leachii to the eastern Atlantic. All specimens previously identified as O. cupella, O. impexa, and O. zoobotryon by different authors in the Mediterranean Sea were repeatedly misidentified. Thus, we describe Okenia problematica sp. nov. and Okenia longiductis sp. nov., from the “Mediterranean” Okenia cupella/impexa and O. zoobotryon. We also consider here Okenia pusilla Sordi, 1974 a nomen dubium and include a redescription of the holotype of O. cupella. A molecular phylogeny, including all the sequenced Okenia species, was performed in order to evaluate the evolutionary relationships of the newly described species with the other congeneric taxa.
Systematics
Order Nudibranchia Cuvier, 1817
Family Goniodorididae H. Adams & A. Adams, 1854
Genus Okenia Menke, 1830
Type species: Idalia elegans Leuckart, 1828 by monotypy
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| Okenia longiductis sp. nov. A. Specimen from Lago di Sabaudia (Italy). Photograph by A. Macali. B. Specimen from La Grande-Motte (France). Photograph by D. Minchin. C. Egg-masses on Amathia verticillata from La Grande-Motte (France). Photograph by D. Minchin. D. Specimen from Mar Piccolo, Taranto (Italy). Photograph by G. Colucci. Size (alcohol-preserved specimens) ~9 mm maximum length. |
Okenia longiductis sp. nov.
Etymology: Named longiductis due to its long reproductive ducts.
Ecology: We always found this species living in the infralittoral zone (up to 5 m depth) on the arborescent bryozoan Amathia verticillata (delle Chiaje, 1822) (Fig 3B and 3D). The same depths and feeding association hold for previous records belonging to Okenia zoobotryon. White and ring-shaped egg-masses were present on this bryozoan (Fig 3C).
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| Okenia problematica sp. nov. Living animals from Gallipoli (Italy). A. Holotype (MNCN15.05/200034); B. Paratype (SZN-MOL0001). Photographs by F. Vitale. Size (alcohol-preserved specimens) ~2.5 mm maximum length. |
Okenia problematica sp. nov.
Etymology: Named problematica due to its complex taxonomic history.
Ecology: We always found Okenia problematica sp. nov. at depths below 10 m. The specimens collected in Gallipoli (Italy) were found on an artificial reef located on a sandy bottom, amidst unidentified hydrozoans and encrusting bryozoans. ...
Marta Pola, Sofía Paz-Sedano , Armando Macali, Dan Minchin, Agnese Marchini, Fabio Vitale, Cataldo Licchelli and Fabio Crocetta. 2019. What is really out there? Review of the Genus Okenia Menke, 1830 (Nudibranchia: Goniodorididae) in the Mediterranean Sea with Description of Two New Species. PLoS ONE. 14(5): e0215037. DOI: 10.1371/journal.pone.0215037
