Okenia picoensis

Okenia picoensis Paz-Sedano, Ortigosa & Pola, 2017

Okenia picoensis @ Palamós by Enric Madrenas
















































Goniodoridella picoensis   (Paz-Sedano, Ortigosa & Pola, 2017)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 1723425).
Body small, up to 5 mm in length, high and elongate. There are three color morphs reported from the type location: some specimens are bright yellow with orange tips of rhinophores, gills and tail, other specimens were white with yellow tips of rhinophores, gills and tail, while the third group show a yellowish transparent base colouration and the tips of external organs and tail may have, or not, orange or yellow tips. Mantle  is covered by long spicules of different sizes and with bulges along them. There is a well-developed notal border with five lateral papillae, symmetrically distributed on each side of body. Two papillae are located ahead of rhinophores, two behind the gills and the remaining three grow on each side of the body between rhinophores and gills. Papillae are cylindrical, long and narrow, increasingly longer and wider to the rear side of the animal. A single median papilla grows in the middle of the dorsum, on the end of a mid-dorsal ridge that extends ahead to the rhinophores. Rhinophores are elongated and slender, bearing between 7 and 9 lamellae at the back and sides of the rhinophores, but not at their front side. Tips of rhinophores lack any lamellae. Gills are formed by 4 unipinnate leaves surroundind the anus, the two anteriormost grow from a common stalk; their shape and length are similar to those of papillae. The foot is long and slender. Two relatively short oral tentacles are located in both sides of mouth. Gonopore is located on right side of body.

Although its diet is unknown, it can be assumed that this species feeds on small bryozoans like the other species of the genus Okenia. No further details of its biology are known.


  • Okenia. In honor of Prof. Dr. Ludwig Gilbert Lorenz Oken, (1779-1851), German natural philosopher, editor of the magazine “Isis” and publisher of the book “Lehrbuch der Naturgeschichte”.
  • Picoensis. Refers to the island of Pico, in the Azores archipelago, where this species was found.

Originally described on the island of Pico, in the Azores archipelago (Pola et al., 2017), it has subsequently been cited throughout the Mediterranean, except in the Adriatic (so far), with reports from the Sea of Alborán to Israel that have occurred in a matter of months, a rapid progress detailed in the paper by Trainito et al., 2022. The first record for Iberian waters (Pontes & Madrenas, 2021) was made in La Herradura, Granada, Spain by David Ballesteros, but in June 2021 it appeared in Tamariu, Catalonia, Spain, reported by Maria Pichlmaier in 8 meters of water on a shady wall. In February 2022 it appeared at Eivissa, Balearic Islands, record with pictures by Joan Pereyra. On 2023 it has been frequent in most diving spots along the Costa Brava, which is surprising given its recent appearance on these coasts.

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

Similar species
Regarding its colouration and external morphology, only two Atlantic taxa resemble Okenia picoensis: Okenia sp.1 from the book by Valdés et al. (2006: p.126) shows a specimen collected at Flamingo Bay, Virgin Island (Bahamas) that shares the same number and distribution of lateral and middorsal papillae. Also Okenia miramarae Ortea and Espinosa, 2000, described on two specimens collected in Miramar, La Habana (Cuba) as having a white background colour with the tips of the lamellae, rhinophores and gill coloured in light orange, and a purplish pink stain behind the gill, also with extraordinarily large lateral papillae on each side of the gill, that exceed the length of the tail when the animal moves. O. picoensis has these papillae quite long but never as long as those described for O. miramarae. O. picoensis has lamellated rhinophores and not tubercled as O. miramarae. Recently O.miramarae was reported at Taliarte, Gran Canaria, Canary Islands, based on two pictures Moro et al. (2016: p.21, pl.7) with no collected specimens that we suspect they belong to O. picoensis, but further anatomical and molecular studies of new specimens from Canary Islands are needed to clarify this matter.


    Western Mediterranean: ★★☆☆☆
    Eastern Mediterranean: ★☆☆☆☆
    Atlantic Ocean: ★☆☆☆☆

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



More pictures


    Crocetta F, Al Mabruk SAA, Azzurro E, et al. 2021. New Alien Mediterranean Biodiversity Records (November 2021). Mediterranean Marine Science. 22(3):724–746. Available from https://ejournals.epublishing.ekt.gr/index.php/hcmr-med-mar-sc/article/view/26668/22433.
    Moro L, Ortea J, Bacallado JJ. 2016. Nuevas citas y nuevos datos anatómicos de las babosas marinas (Mollusca: Heterobranchia) de las islas Canarias y su entorno. Revista de la Academia Canaria de las Ciencias., 48: 9-52.
    Orfanidis S, Alvito A, Azzurro E, et al. 2021. New Alien Mediterranean Biodiversity Records (March 2021). Mediterranean Marine Science. 22(1):180–198. https://doi.org/10.12681/mms.25294.
    Ortea JA, Espinosa J. 2000. Nueva especie del género Okenia Menke, 1830 (Mollusca: Nudibranchia) de Cuba. Avicennia, Revista de Oceanología, Ecología y Biodiversidad Tropical 12-13:84-86.
    Paz-Sedano S, Ortigosa D, Pola M. 2017. A new Okenia Menke, 1830 from the Azores Islands, Portugal. Spixiana. 40(1):13–22.
    Poizat CH. 1991. New data on an interstitial opisthobranch assemblage and other meiofauna from the Skagerrak, Sweden. J. Molluscan Stud. 57(4, supplement):167-178.
    Pola M, Paz-Sedano S, Macali A, et al. 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. https://doi.org/https://doi.org/10.1371/journal.pone.0215037.
    Pontes M, Madrenas E. 2021. First records of the NE Atlantic nudibranch Okenia picoensis Paz-Sedano, Ortigosa & Pola, 2017 (Gastropoda, Goniodorididae) in the Mediterranean Sea [in] Orfanidis et al. (2021) New Alien Mediterranean Biodiversity Records (March 2021). Mediterranean Marine Science. 22(1):186–187. https://doi.org/10.12681/mms.25294.
    Trainito E, Migliore V, Doneddu M. 2022. How many seas must a nudibranch sail? Okenia picoensis (Mollusca: Nudibranchia: Goniodorididae) conquering the Mediterranean. Studia Marina. 35(1):15–25. https://doi.org/10.5281/zenodo.6676729.

    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 (2023) "Okenia picoensis" in OPK-Opistobranquis. Published: 29/03/2021. Accessed: 24/04/2024. Available at (https://opistobranquis.info/en/?p=32030)

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