Taxonomic note: The most similar species to M. mediterranea is M. limaciformis, described by Eliot (1908) from the Red Sea. Both species share several morphological and anatomical features, like a deep saffron-red base body colour with small yellowish to white dots scattered on the back and sides of the body. However, the presence of purple on the tips of the rhinophores and the tips of the gill is distinctive in M. limaciformis (Baba, 1960 and Pola et al. 2006a). To discard the possibility that M. mediterranea was actually M. limaciformis introduced through the Suez Canal (as previously believed), phylogenetic analysis were conducted and certified different (Domínguez et al. 2015). Willan & Chang (2017) moved it into the new genus Martadoris Willan & Chang, 2017.
Tambja mediterranea Domínguez, Pola & Ramón, 2015
Description This species body is elongate and limaciform, ending in a pointed tail. The living animal measures up to 10 mm in length. Base body colour is orange-red. The dorsum is covered with rounded whitish or yellowish tubercles. In some specimens, the tubercles are large and most of them arranged in three rows along the body while in others, the tubercles are smaller and irregularly scattered over the dorsum. The head is rounded anteriorly, with a pair of perfoliate rhinophores with about 15–20 lamellae, retractile in elevated sheaths. The rhinophores are coloured dark red with a whitish tip. The oral tentacles are short and grooved. The gill has 3 tripinnate non-retractile leaves, with an orange-reddish rachis and whitish or yellowish branches. There are lateral slots below the rhinophores. The foot and oral tentacles are coloured orange-red.
Biology No data about it’s biology is known yet. The first collected specimens from Mallorca were found at 53 m depth, in a medium-grained sandy bottom, in a zone predominantly composed by the red algae Phyllophora crispa. The specimens from Malta were collected in bycatch from fishermen’s nets at 50-60 m depth along with Posidonia oceanica leaves and maerl. Specimens from Granada were found over calcareous red algae in 23 m depth, but the last report from Mallorca was found in 45 meters. A single specimen observed in Catalonia was found in 48 meters on a Eunicella singularis sea fan.
Mediterranea. From Latin “médium”, middle, interspace, intermediate space, center + “terra”, Earth. From the Mediterranean Sea.
Distribution It is a very recently described species, based on specimens found on the island of Mallorca (Oceanographic Campaign DRAGONSAL 2014) and Malta (Fom Ir-Rih, 07/07/2014: C. Mifsud in Sammut, 2016). On the coast of Granada (La Herradura, 6/12/2013: F. Aguado, pers. comm.), on the Italian coast (Secce di Tor Paterno, 08/30/2014: G. Salera, pers. comm.) and in Malta (Island of Gozo, 06/19/2015: H. Domnick in Köhler, 2016) there were reports of Martadoris limaciformis (Eliot, 1908) which have now been assigned to Martadoris mediterranea (Domínguez et al., 2015). The observation of a specimen of this species and 7.9 cm long in the Cap Norfeu, Roses, Spain, on the Eunicella singularis gorgonian at 48 m depth (9/11/2015: J.M. Báñez and J. Barcia, GROC), extends its distribution in the Iberian Mediterranean coast, as well as its maximum recorded size, which so far was 20 mm (23/09/2006: G. & P. Peels in Köhler, 2016; 06/19/2015, H. Domnick in Köhler, 2016). A report from Mallorca (Sòller, 12/4/2016: L. Juskaničová, pers. comm.) in 45 meters of water, and a recent report (Enric Ballesteros, Pers.Comm.) in september 2020 at Na Foradada (Cabrera, Spain) in 35 meters of water confirms the stable presence of the species in the Balearic Islands. The easternmost report is from the island of Samos, Greece, of two specimens in 8 meters of water (Tatjana Stockmann & Benjamin Gundacker) found in September 2020.
Known georeferenced records of the species: Martadoris mediterranea
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Willan, R. C., & Chang, Y.-W. (2017). Description of three new species of Tambja (Gastropoda, Nudibranchia, Polyceridae) from the western Pacific Ocean reveals morphological characters with taxonomic and phylogenetic significance for traditional Polyceridae and related “phaneorobranch” nudibranchs. Basteria. 81(1-3): 1-23.
Pontes, Miquel, Manuel Ballesteros, Enric Madrenas (2021) "Martadoris mediterranea" in OPK-Opistobranquis. Published: 31/08/2014. Accessed: 25/09/2021. Available at (https://opistobranquis.info/en/Ag8wp)