Okenia aspersa

Okenia aspersa (Alder & Hancock, 1845)

Okenia aspersa @ Pointe de l'Espiguette, France by Pascal Girard
















































Okenia aspersa  (Alder & Hancock, 1845)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 140035).

  • Doris quadricornis Montagu, 1815
  • Idalia aspersa Alder & Hancock, 1845
  • Idalia caudata Orested, 1844 
  • Idalia modesta Verrill, 1875 
  • Idalia pulchella Alder & Hancock, 1854
  • Idaliella modesta (A. E. Verrill, 1875)
  • Okenia ascidicola M. P. Morse, 1972 
  • Okenia leachii var. quadricornis (Montagu, 1815)
  • Okenia modesta (A. E. Verrill, 1875) 
  • Okenia pulchella (Alder & Hancock, 1854)
  • Okenia quadricornis (Montagu, 1815)

With a lenght of about 15-20 mm, the reddish brown body bears spicules and a narrow pallial ridge with 16 simple appendages, of which the anterior 4 are elongate, while the remainder are shorter, all of the same colour of the body. Small areas of the flanks, veil, tail, rhinophores, gills and appendages show a darker colour and there are yellow patches scattered everywhere but the ventral surface of the foot. Also there are opaque white spots scattered over flanks, veil and tail, that shows a white middle line from the gills to almost its tip. The frontal velum is slightly bilobed. The rhinophores, having 43 lamellae, are a little longer than the anterior appendages, all of them with hyaline white tips. The branchial tuft has 11 unipinnate gills. The spicules lie within the integument and up to the tips of the pallial ridge appendages. The genital pore opens on the right of the anterior third of the animal’s body.

Okenia aspersa is reported to feed on Ascidiella spp. (Thompson, 1964; Thompson & Brown, 1976; Todd, 1981) and Molgula spp. (Holt, 1891; Thompson & Brown, 1976; Just & Edmunds, 1985; Picton & Morrow, 1994; Valdés & Ortea, 1995).


  • 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”.
  • Aspersa. From Latin “aspersus”, sprinkled, powdered.

This species has been reported from Norway to Southern Portugal, also in the Western Mediterranean where it has been found in France, Italy and Malta. A report of Okenia ascidicola from Massachussetts, USA (Morse, 1972), that is now considered a synonim of O.aspersa, should be verified molecularly.

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


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

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



More pictures


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Further reading

Cite this article as:

Ballesteros, M., Madrenas, E. & Pontes, M. (2023) "Okenia aspersa" in OPK-Opistobranquis. Published: 19/10/2014. Accessed: 27/02/2024. Available at (https://opistobranquis.info/en/?p=16277)

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