Okenia aspersa

Okenia aspersa (Alder & Hancock, 1845)

• 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)

Description
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.

Biology
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).

Etymology

• 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.

Distribution
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

Sources:
OBIS GROC 2010-2011 Enric Madrenas João Pedro Silva Bernard Picton GBIF	OPK VIMAR Manuel Ballesteros M@re Nostrum Altres fonts Marine Regions

Videos

More pictures

Okenia aspersa Two spawn coils. Location Bushmills Bay, Causeway Coast, coordinates 55.230417,-6.5528, depth 27.5m, date 08-06-2010. – Photograph ©Bernard Picton

Okenia aspersa disruptive camouflage. Location White Cliffs, Rathlin, Rathlin Island, coordinates 55.292767,-6.240267, depth 30m, date 14-06-2007. – Photograph ©Bernard Picton

Okenia aspersa @ Tiree, W. Scotland. Collected Bob Earll, photo by Bernard Picton

Okenia aspersa @ Penzance, UK 20200509 by David Fenwick

Okenia aspersa by Cervera el al (1991)

Okenia aspersa @ France by Pascal Girard

Bibliography

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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

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