Okenia problematica

Okenia problematica Pola, Paz-Sedano, Macali, Minchin, Marchini, Vitale, Licchelli et Crocetta, 2019

Okenia problematica @ Gallipolli (Lecce, Italy) by Fabio Vitale













































Okenia problematica  Pola, Paz-Sedano, Macali, Minchin, Marchini, Vitale, Licchelli & Crocetta, 2019

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 1343365).

  • Okenia impexa banyulensis Schmekel, 1979 (unavailable under ICZN Art. 15.1: name proposed conditionally after 1960)

Elongated, translucent white body, covered with many and concentrated brown spots, with randomly scattered white-yellowish spots. The whole body is covered by conspicuous spicules, and it ends in a long and pointed translucent white tail covered with mostly white and scattered brown dots. The notal border is well developed, with 8 lateral papillae symmetrically distributed on each body side. Distribution of papillae is as follows: one located in front of rhinophores, one besides the rhinophores, four between the rhinophores and the gill, and two behind gill rising from same stalk. The shape and size of the papillae is slightly variable; the two papillae located at the front are long and finger-like, followed by a shorter one and then they subsequently increasing in size to the rear side of the body. All papillae located behind the rhinophores have a rounded widening at the tip, more evident in the papillae located behind the gill. There is a single papilla in the mid-dorsal line similar in shape and size to the ones on the sides, and also with a rounded tip. Rhinophores are long and slender, of the same colour pattern of the body, with 6–9 lamellae each on the distal portion. Gill is composed of four unipinnate branches surrounding the anus, the two located ahead sharing a common stalk. There are two short oral tentacles flanking the mouth. The foot is long and slender, coloured translucent white without any spots, and with two small but elongated propodial tentacles in the anterior side. Genitalia is located on the right side of the body, usually close to the rhinophore.

Okenia problematica seems to be common 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. Templado (1982), Valdés & Ortea (1995), García-Gómez et al. (2011), and Ballesteros et al. (2016) mostly reported its cryptic presence in rocky infralittoral bottoms (~5–10 m) with the bryozoan Margaretta cereoides (Ellis & Solander, 1786). However, Schmekel (1979), Schmekel & Portmann (1982), Valdés & Ortea (1995), and Ballesteros et al. (2016) also reported its presence at 5–15 m depth on infralittoral algae such as Halimeda J.V.Lamouroux, 1812, those of the family Corallinaceae Lamouroux, 1812 and Codium vermilara (Olivi) Delle Chiaje, 1829.


  • Problematica, due to its complex taxonomic history.

Species has been described on specimens collected at Gallipoli (Lecce, Italy), Aiguafreda (Begur, Girona, Spain), and Cala Joncols (Roses, Girona, Spain). Literature records of Okenia cupella and Okenia impexa from the Mediterranean Sea also belong to this taxon.

Known georeferenced records of the species: Okenia problematica
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
: Manuel Ballesteros.
: M@re Nostrum
: Altres fonts
: Marine Regions


    Western Mediterranean:1 out of 5 stars
    Eastern Mediterranean:0 out of 5 stars
    Atlantic Ocean:0 out of 5 stars

This chart displays the monthly observation probability for Okenia problematica based on our own records.

Other pictures


    Ballesteros, M., E. Madrenas, and M. Pontes. 2021. OPK - Opistobranquis. (https://opistobranquis.info/).
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    Ballesteros, M., M. Pontes, and E. Madrenas. 2019. Els nudibranquis del mar català. Brau, Figueres.
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    Cervera, J. L., G. Calado, C. Gavaia, M. A. E. Malaquías, J. Templado, M. Ballesteros, J. C. García-Gómez, and C. Megina. 2004. An annotated and updated checklist of the opisthobranchs (Mollusca: Gastropoda) from Spain and Portugal (including islands and archipelagos). Boletín Instituto Español de Oceanografía, 20 (1-4): 1-111. L.
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    Long, S. J. 2006. Bibliography of Opisthobranchia 1554-2000. Bayside Books & Press, Tustin, CA, U.S.A. 672p.
    McDonald, G. 2009. Bibliographia Nudibranchia. 2nd Online Edition, Annotated. 1072 pp  Institute of Marine Sciences, University of California, Santa Cruz. (http://escholarship.org/uc/item/8115h0wz).
    Pola, M., S. Paz-Sedano, A. Macali, D. Minchin, A. Marchini, F. Vitale, C. Licchelli, and F. 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.
    Sabelli, B., R. Gianuzzi-Savelli, and D. Bedulli. 1990. Catalogo annotato dei Molluschi marini del Mediterraneo. Libreria Naturalistica Bolognese. Bologna, Italy: 348 pp.
    Schmekel, L. 1979. First record of Okenia impexa Marcus, 1957 from the western Atlantic in the Mediterranean. Veliger 21(3):355-360.
    Schmekel, L., and A. Portmann. 1982. Opisthobranchia des Mittelmeeres, Nudibranchia und Saccoglossa. Fauna e Flora del Golfo Napoli. Springer-Verlag, Berlin.
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    Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

Cite this article as:

Pontes, Miquel, Manuel Ballesteros, Enric Madrenas (2021) "Okenia problematica" in OPK-Opistobranquis. Published: 29/11/2020. Accessed: 27/01/2021. Available at (https://opistobranquis.info/en/cxPaK)

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