Trinchesia foliata

Trinchesia foliata (Forbes & Goodsir, 1839)

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 a great previously undetected species diversity.
A few months later Korshunova et al. (2017) take up the study of the phylogeny of the Tergipedidae and using not only molecular data but also morphological and ontogenetic data they severely criticise the work by Cella et al. (2016), proposing to reinstate the families Calmidae, Eubranchidae, Fionidae, Tergipedidae, Cuthonidae, Cuthonellidae and Trinchesiidae, the latter being the most abundant in specific taxa. They also reinstate the genera Catriona, Diaphoreolis, Phestilla and Trinchesia that in the paper by Cella et al. (2016) had been included in the genus Tenellia. Korshunova et al. also describe a new genus, Zelentia that includes Z. pustulata (type species Eolis pustulataAlder & Hancock, 1854), Z. fulgens (MacFarland, 1966) and a new species from the Barents Sea, Z. ninel, indicating important p-distances among the three species (between 10.49% and 13.83%). All previous genera, Korshunova et al. (2017) consider them within the family Trinchesiidae. They also question the validity of the Rubramoena genus of Cella et al.
The position of WoRMS is conservative, maintaining the families Cuthonidae, Calmidae, Cuthonellidae, Eubranchidae, Fionidae, Pseudovermidae, Tergipedidae and Trinchesiidae within the superfamily Fionoidea. The European species that, until recently, were considered as Cuthona, WoRMS considers them within the genus Trinchesia, as T.albopunctata, T.caerulea, T.foliata, T.genovae, T.granosa, T.ilonae, T.miniostriata and T.ocellata. Rubramoena is also considered a valid genus in WoRMS. These opinions are those that we accept in OPK while no other more conclusive data are available.

• Eolidia foliata Forbes & Goodsir, 1839
• Eolis conspersa Dalyell, 1853 
• Eolis olivacea Alder & Hancock, 1842
• Cuthona foliata (Forbes & Goodsir, 1839)
• Tenellia foliata (Forbes & Goodsir, 1839)

Description
These is a small-sized aeolidacean that usually does not exceed 5-6 mm in length, although a maximum size of 10 mm has been reported (Bouchet, 1977). The body is usually translucent whitish, with opaque white scores on the head, oral palps, dorsum, flanks and tail. There are characteristic orange lines from the base of the oral palps to the anterior base of the rhinophores and from the posterior base of these, somewhat divergently, to the first group of cerata. The oral palps are short, semitransparent and have white granulations that are usually aligned on the anterior side. The rhinophores are somewhat longer than the oral palps, they have a blunt tip and the upper third is whitish. There are 5 to 7 cerata groups on each side of the back, with up to 5 cerata per group. Between 2 and 3 cerata groups are located in front of the cardiac area. The cerata are relatively short and globose and their apex is rounded and translucent, the cnidosac can be seen by transparency. The color of the digestive gland inside is usually chestnut brown with olive tones. White granulations are scattered on the surface of cerata, more abundant in the upper two thirds. The foot is semitransparent, as the body, and is rounded and slightly widened in the front area, not forming propodial palps.

Biology
Like other species of small aeolidaceans, T. foliata is usually found between intertidal or infralittoral algae with epizootic hydrozoans and on the underside of stones. The spawn is shaped like a small semicircular ribbon (Alder & Hancock, 1845).

Etymology

• Trinchesia. In honor of Professor Salvatore Trinchese (1836-1897), Italian opisthobranchiologist, Professor of Zoology at Bologna University and successor of Paolo Panceri as Professor of Comparative Anatomy at the University of Napoli.
• Foliata. From Latin “foliātus”, bearing foliage, bearing leaves, from “folium”, leaf.

Distribution
T. foliata is a species of the European Atlantic that has been reported from Norway and the British Isles down to Portugal (Bouchet, 1977). This author also indicates the differences between this species and T. genovae, as they are very similar and probably have been confused in the literature, noting that the distribution of T. foliata is eminently Atlantic whereas T. genovae is Mediterranean. Calado (2002) cites T. foliata for the Azores. In the Iberian Peninsula it has been reported from the Bay of Biscay to the Strait of Gibraltar (Cervera et al., 2004). There are some reports of T. foliata in the Mediterranean that would need to be confirmed.

Known georeferenced records of the species: Trinchesia foliata

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

Similar species
Trinchesia genovae, an eminently Mediterranean species, very similar but with a characteristic yellow dorsal line and yellow rings in the cerata that T. foliata does not have.

More pictures

Trinchesia foliata @ Cudillero, Asturias, Spain 10/10/2013 by Luís Ángel Díaz

Trinchesia foliata @ Cudillero, Asturias, Spain 10/10/2013 by Luís Ángel Díaz

Trinchesia foliata by Enric Madrenas

Trinchesia foliata by Enric Madrenas

Trinchesia foliata Murles Point, Co. Donegal, Ireland

Trinchesia foliata @ Looe, Cornwall, UK by Heather Buttivant

Trinchesia foliata @ Looe, Cornwall, UK by Heather Buttivant

Trinchesia foliata @ Sweden by Klas Malmberg

Trinchesia foliata @ Sweden by Klas Malmberg

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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