Rubramoena amoena

Rubramoena amoena (Alder & Hancock, 1845)

Rubramoena amoena 6 mm @ Lephinchapel, Loch Fyne, Scotland 15m 5-10-2008 by Jim Anderson

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.

Although recent work questions the validity of the genus Rubroamoena, we keep the proposal by Cella et al. (2016) to keep the former species Cuthona amoena and Cuthona rubescens within this genus. Both species are apparently similar, but Picton and Brown (1978) highlighted the main differences in their description of Cuthona rubescens.

Synonyms

• Eolis amoena Alder & Hancock, 1845
• Trinchesia amoena (Alder & Hancock, 1845)
• Cuthona amoena (Alder & Hancock, 1845)

Description
It is usually about 10 mm long, has a translucent body with brown spots at the base of the cerata, and characteristic brown rings on the rhinophores and oral tentacles. The upper part of the body and cerata are dotted with irregular golden or yellowish dots, being densest at the tips of the head tentacles and cerata. The mandibles are visible by transparency on the head. The foot is narrow, with the anterior edge slightly lobed, and somewhat rounded and widened laterally.

Biology
It is generally found in colonies of the hydrarian Halecium halecinum, which seems to be its food. The spawn consists of a thin, white, scalloped cord, usually coiled around the branches of its food, or forming a spiral of two or three turns.

Etymology

• Rubramoena. Refers to the specific names of the two species it contains: Rubramoena amoena (type species) and Rubramoena rubescens.
• Amoena. Femenine form of the Latin word “amoenus”, charming, pleasant, agreeable.

Distribution
From Norway and the Orkney Islands to Gibraltar. Common around the British Isles and Ireland. In the Iberian Peninsula it has been reported on the Cantabrian coast, also in Galicia and Portugal. The Mediterranean reports from Catalonia (Cadaqués, Begur, Palamós, Sant Feliu de Guíxols and Mataró), Italian Salento, Malta and the Adriatic Sea probably correspond to one or two different undescribed species.

Similar species
Trinchesia albopunctata is smaller, with white (not yellowish) body punctations, no brown bands on the rhinophores, and oral tentacles that do, however, have a band without punctations. Rubramoena sp. with brown rings on rhinophores and oral tentacles, body without yellowish punctuations, with or without a white dorsal band.

Altres fotos

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

• AsturNatura
• Biodiversity Heritage Library
• Encyclopedia of Marine Life of Britain and Ireland
• Flickr pictures
• GROC
• Interim Register of Marine and Nonmarine Genera
• MedSlugs (Atl.NE)
• NCBI GenBank
• OBIS - Search by Taxon
• Scottish Nudibranchs
• Sea Slug Forum
• World Register of Marine Species

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