Okenia mediterranea (von Ihering, 1886)
Okenia mediterranea @ L'Escala, Spain by Enric MadrenasTaxonomy
Class: Gastropoda Cuvier, 1797
Subclass: Heterobranchia J.E. Gray, 1840
Clade: Euthyneura Spengel, 1881
Clade: Nudipleura Wägele & Willan, 2000
Order: Nudibranchia Cuvier, 1817
Suborder: Euctenidiacea Tardy, 1970
Infraorder: Doridacea Thiele, 1931
Superfamily: Onchidoridoidea J.E. Gray, 1827
Family: Goniodorididae H. Adams & A. Adams, 1854
Genus: Okenia Menke, 1830
Species: Okenia mediterranea (von Ihering, 1886)
- Idalia mediterranea Ihering, 1886
This species measures up to 15 mm and has an oval shaped body coloured translucent white with many surfaces covered with opaque white, and with many yellow and reddish orange spots on the dorsum of most specimens. There are 9-12 pairs of lateral papillae tipped in orange over yellow pigment, the foremost pair longer than the rest, and the rearmost last two papillae joined at their bases on each side (Cervera et al. 1991). There is a ridge of 4-5 short, partly fused papillae along the dorsum midline, running from the rhinophores to the gills, also coloured in orange over yellow, and a row of 2-3 similarly coloured short papillae or tubercles (only present in adult specimens) on each side of the central ridge. A less common colour form shows yellow markings only (Rudman, 2001). Gills and rhinophores are relatively long and coloured with the same pattern as the other body processes. Rhinophores have 12-20 fine lamellae and the gill has 5-9 unipinnate white leaves with a yellow rachis, with 3-15 lamellae each (Cervera et al. 1991), surrounding a prominent anal papilla. The genital pore is located on the right flank of the animal, behind the rhinophores. The head has a bilobed frontal veil, with a yellow spot on each corner and the foot has a triangular shape at the tail, which is white with a yellow median line, edged with red spots in larger animals.
This species apparently feeds on the ctenostome encrusting bryozoan Alcyonidium mytili Dalyell, 1848 (see Cervera et al., 1991), despite Cattaneo-Vietti et al (1990) reported it feeding on the red gorgonian Paramuricea clavata and this information was used by other authors. The bathymetric range was reported in the coralligenous areas below 30 meters deep, but we have found this animal in much shallower water (12-15 meters), so this has to be revised. Its spawn consists on a circular shaped ribbon 10-12mm long, laid in a usually incomplete circle on the Alcyonidium bryozoan. Egg capsules measure between 71-97 microns and contain a single spherical white egg of 58-78 microns of diameter. Okenia mediterranea could be mistaken with other Okenia species, but colouration and papillae patterns differ. Okenia sapelona (Marcus & Marcus , 1967) is a very similar species (only differs on a blue tone of the white surfaces) that could correspond to a Western Atlantic distribution of Okenia mediterranea (see Valdés & Ortea, 1995 and Rudman, 2001), if this was the case O. mediterranea would become an amfiatlantic species. Confusion arises from the fact this species external features appear to change with age (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”.
- Mediterranea. From Latin “médium”, middle, interspace, intermediate space, center + “terra”, Earth. From the Mediterranean Sea.
This species has been reported in Naples, Italy (Ihering, 1886; Schmekel, 1979; Schmekel & Portmann, 1982), in Numana, Italy (Cristian Magnani in Rudman, 2001), in Sicily, Italy (Valdés & Ortea, 1995), in Lecce, Italy (Fabio Vitale & Cataldo Licchelli, 2016), in Antalya, Turkey (Haluk Akbatur in Rudman, 2001), also in Granada, Spain (Sánchez-Tocino, 2000), in Algeciras, Spain (Alma Sánchez in Rudman, 2001), in Almeria, Spain (Moreno & Templado, 1998), in Vigo, Spain (Valdés & Ortea, 1995; Carlos Fernández-Cid, 2017), in Palamós, Spain (Enric Madrenas, 2009), in L’Escala, Spain (Enric Madrenas, 2017) and in Illes Medes, Spain (Guillem Mas, 2013). Also in Sines, Portugal (Calado et al. 2003) and in Madeira, Portugal (Valdés & Ortea, 1995). It is considered very rare.
|: OBIS||: OPK|
|: GROC 2010-2011||: VIMAR|
|: Enric Madrenas||: Manuel Ballesteros.|
|: João Pedro Silva||: M@re Nostrum|
|: Bernard Picton||: Other sources|
|: GBIF.ORG||: Marine Regions|
This chart displays the observation probability for Okenia mediterranea
based on our own records.
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.