Tenellia caerulea

Tenellia caerulea (Montagu, 1804)

Tenellia caerulea @ Strangford Lough, Co Down, Ireland by Bernard Picton
Class: Gastropoda Cuvier, 1797
Subclass: Heterobranchia J.E. Gray, 1840
Clade: Euthyneura Spengel, 1881
Clade: Nudipleura Wägele & Willan, 2000
Order: Nudibranchia Cuvier, 1817
Suborder: Dexiarchia Schrödl, Wägele & Willan, 2001
Infraorder: Cladobranchia Willan & Morton, 1984
Parvorder: Aeolidida Odhner, 1934
Superfamily: Fionoidea Gray, 1857
Family: Fionidae  Gray, 1857
Genus: Tenellia A. Costa, 1866
Species: Tenellia caerulea (Montagu, 1804)

Taxonomic note: The phylogenetic analyses performed by Cella et al. (2016) revealed that the traditional Tergipedidae family is polyphyletic and belongs to a larger monophyletic clade including members of the traditional families Eubranchidae, Fionidae and Calmidae; this was an unexpected result, since the validity of these taxa and their distinctness from the Tergipedidae was never questioned before. They proposed to join the families Tergipedidae, Eubranchidae, Calmidae and Fionidae under the name of Fionidae. Within Fionidae, obtained results demonstrated the need of developing a new classification as previous classifications (for instance, separating Catriona, Cuthona and Trinchesia as distinct taxa) were inconsistent with the resulting phylogeny. Analyses also recover a clade (Tenellia) that includes all members of the genera Tenellia, Trinchesia, Phestilla, Catriona and the majority of described and undescribed Cuthona species. New genera Rubramoena, Abronica and Tergiposacca are proposed to group other species. This molecular study also suggests that Fionidae is rich in cryptic species complexes, difficult to separate by traditional taxonomic characters, and previously undetected species diversity.

Korshunova et al. (2017) present some phylogenies based on morphological characters (which may be parological) to reclassify this group. In addition, for molecular phylogeny they use the COI gene (not useful to separate genera) instead of i.e. the H3 gene, so the hypotheses presented are weak. For this reason we keep the last classification until the status of this species is cleared.


  • Doris caerulea Montagu, 1804
  • Eolidia bassi Vérany, 1846
  • Eolis deaurata Dalyell, 1853
  • Eolis glotensis Alder & Hancock, 1846
  • Eolis molios Herdman, 1881
  • Cuthona caerulea (Montagu, 1804)
  • Trinchesia caerulea (Montagu, 1804)

The size of this species can reach up to 25 mm in length, although it uses to be smaller, of about 10-12 mm in length. The body background color is whitish but has a very soft yellowish green hue in some areas. Oral palps and rhinophores are relatively short and colored white yellow at the base and orange at the tips. The rhinophores are very close together at the base and the eyes are located slightly behind and outside of the base of the rhinophores. The cerata are short and fusiform and gathered in 6-7 groups at each side of the body, and the first group has about 3 rows of cerata, while the others have only one. Between the first and second group of cerata, in the center of the back, there is the cardiac area. The color of the cerata makes this species unmistakable: the translucent base with some tiny blue spots, then an orange colored ring, then a dark blue ring (that gives its name to the species), then an orange ring and finally the translucent apex. With all this coloration of the cerata, the digestive gland running inside is not visible. The foot is narrow and translucent white and does not have oral palps. The Mediterranean specimens, probably a different cryptic species, have iridiscent white or yellowish white bands along the dorsum and sides of the body; the dorsal stripe usually reaches the dorsal part of the head and the tail.

T. caerulea is one of the most common nudibranchs on rocky shores, generally with little illumination and abundance of algae and hydroids. Among hydrarians on which it has been cited we can be highlight Aglaophenia pluma, Eudendrium racemosum, Halecium halecinum and different species of Sertularella (S.polyzonias, S.crassicaulis, S.gayi), on which it feeds. The smaller specimens in the Mediterranean usually have a brightest general body and cerata coloration, with a white dorsal band, a fact that led to speculate whether they could be different species, a fact not yet verified. The spawn is laid on the hydrarian the animal feeds on, wound into a flat spiral of about 2 and a half turns filled with white oval eggs, helically arranged within the cord; the size of the eggs is about 200 microns.


This species inhabits European Atlantic waters from Ireland and the British Isles, the Açores and the Canary islands. Despite it is present in the Mediterranean, it is probable that it shares habitat with another very similar cryptic species not yet described, present in the Mediterranean from Greece to the Western basin. In the Iberian Peninsula it is found in all its coastal areas, including Portugal. It has also been cited in Balearic islands. In the Catalan coast it has been observed in many localities of the Costa Brava, from the Port de la Selva to Blanes.

Known georeferenced records of the species: Tenellia caerulea (z-200).
: GROC 2010-2011 : VIMAR
: Enric Madrenas : Manuel Ballesteros.
: João Pedro Silva : M@re Nostrum
: Bernard Picton : Other sources
: GBIF.ORG : Marine Regions

References for the species: Tenellia caerulea

    Galicia: Urgorri and Besteiro (1983, 1984), Rolán (1983). Portugal: De Oliveira (1895), Hidalgo (1916), Nobre (1932) (all the above records as Amphorina), García-Gómez et al. (1991), Calado et al. (1999, 2003). Gibraltar: García-Gómez (1983, 2002), García-Gómez et al. (1989). Levante: De Fez (1974, as Amphorina), Templado (1982b, 1983, 1984), Marín and Ros (1987, 1991). Catalunya: Ros (1975, 1978b, 1985a, citada como Trinchesia aurantia), Ros & Altimira (1977), Altimira et al. (1981), Ballesteros (1980, 1985), Pereira (1981), Pereira & Ballesteros (1982), Huelin & Ros (1984), M@re Nostrum [Cala Rovellada (Portbou) 11/2000, Illa Rodona (Llançà) 11/1998, Bau de S’Arnella (El Port de la Selva) 6/2000, Bau de la Punta del Molí (El Port de la Selva) 5/1999, Illa Mateua (L'Escala) 12/2001 y 3/2002]. Citada con anterioridad a 1985 como Trinchesia caerulea. Baleares: Wirtz and Debelius (2003), Ballesteros and Templado (1996). Canarias: Moro et al. (1995, 2003), Ortea et al. (2001, 2003), Wirtz and Debelius (2003). Azores: Calado (2002).

    General: Barletta, 1981:114; Burgin-Wyss, 1961:461; Nordsieck, 1972:80; Pruvot-Fol, 1953b:[P]; 1954b:381; Thompson, 1976a:[P]; Thompson & Brown, 1976:186; Vicente, 1963a:177; 1967:156 as Trinchesia caerulea; Brown, 1980:243; Brown & Picton, 1979:27; Cattaneo-Vietti, Chemello, & Giannuzzi-Savelli, 1990:179[P]; Hayward, Wigham, & Yonow, 1990:726; Picton & Morrow, 1994:100[P]; Riedl, 1983:329; Schmekel & Portmann, 1982:248[P]; Thompson, 1988:266[P]; Thompson & Brown, 1984:120[P] as Cuthona caerulea

    Sources: Cervera et al., 2004, Ballesteros, 2007, McDonald, 2006 and other sources.


        Western Mediterranean:3 Stars
        Eastern Mediterranean:1 Stars
        Atlantic Ocean:3 Stars
This chart displays the observation probability for Tenellia caerulea
based on our own records.

More pictures


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:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes et al. (2012-2017) "Tenellia caerulea" in OPK-Opistobranquis, Published: 17/05/2012, Accessed: 17/10/2017 at (http://opistobranquis.info/en/puvcp)

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