Trinchesia ocellata

Trinchesia ocellata  Schmeckel, 1966

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.

• Tenellia ocellata  (Schmekel, 1966)
• Cuthona ocellata (Schmeckel, 1966)

Description
The specimens can grow up to 13 mm in length. The animal body is stylized and translucent but with a yellowish-green hue. In the dorsum stands out a white longitudinal line that runs from the head, across the base of rhinophores, to the tail. On the flanks of the body also tends to have a white line, sometimes discontinuous. The oral palps are relatively short, transparent and with white pigment on the surface, but at the base, which is yellow. The rhinophores are almost as long as the oral palps and are also semi-transparent, so with a binocular lens it is possible to see the rhinophoric nerve inside. The surface of rhinophores has white spots that may be almost continuous in the front and rear sides. The eyes, inconspicuous, are located somewhat behind the base of the rhinophores. There can be up to 8 groups of cerata on each side of the body. The first two groups are symmetrical and among them there is the heart region, noticeable because of a slight prominence and because of the transparent integument, it is possible to distinguish the atrium and the ventricle and observe its contractions. There are three rows of cerata in the first group while only one row in the other groups. From the second group of cerata, the rest are asymmetric, the insertion of the right ones being a little advanced than the insertion of the left ones. In each group, the size of cerata increases from the outer side to the more internal ones. Inside each cerata, the digestive gland is brown at the base and deep red near the apex, which is yellowish. In the upper half of the epidermis of the cerata there are white spots of irregular size and shape. The foot is narrow and its anterior zone has short propodial palps coloured yellowish green. The genital orifice is located under the second row of the first group of cerata on the right side of the body.

Biology
Several species of hydrarians have been cited as substrate for T.ocellata, both thecate and athecate, like the genus Halecium, Dynamena, Sertulaella, Dicoryne, Podocoryne, Obelia and Eudendrium. They could be this species food source. Spawns have been found on colonies of the hydrarian Halecium labrosum; the spawn is an irregularly shaped transparent cord with white eggs of about 120 microns in diameter.

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.
• Ocellata derives from Latin ocellus, a diminutive of oculus, eye. Refers to a simple eye common to many marine organisms, but is also used for animals with circular spots, similar to eyes.

Distribution
It is present on all the coasts of the Iberian Peninsula, both Atlantic and Mediterranean. In the western Mediterranean it has been reported in Spain, France and Italy, with some reports in the Adriatic Sea. In Catalonia it has been found all along the Costa Brava, where it is relatively common.

Known georeferenced records of the species: Trinchesia ocellata
Sources:
: OBIS : GROC 2010-2011 : Enric Madrenas : João Pedro Silva : Bernard Picton : GBIF.ORG	: OPK : VIMAR : Manuel Ballesteros. : M@re Nostrum : Altres fonts : Marine Regions

Similar species
The greenish yellow coloration of the body make it unmistakable.

Abundance

Western Mediterranean:	★★☆☆☆
Eastern Mediterranean:	☆☆☆☆☆
Atlantic Ocean:	★☆☆☆☆