BASEODISCUS URGORRII SP. NOV.

(FIGS 3G, H, 7F, G)

Baseodiscus sp. DNA105581: Andrade et al., 2012: 157.

Zoobank registration: urn: lsid: zoobank. org:act: BBF6E937-7250-495D-B216-EE5284EA04C5.

Type material: Holotype, MCZ IZ- 135319 (morphological specimen); MCZ DNA 105581 (extracted DNA); 5 October 2009, about 800 m depth, off the coast of Vigo (42°42′43″N, 11°49′53″W), Pontevedra, Galicia, Spain, collected by G. Giribet at station 27-AT of the DIVA-ARTABRIA II Expedition.

Sequences: From the holotype: JF293052, 18S (1770 bp); HQ856862, 28S (2570 bp); JF277568, 16S (502 bp); HQ848588, COI (657 bp). Determined by Andrade et al. (2012) and deposited in GenBank as derived from Baseodiscus sp. 1 SA-2011.

Description: Background body colour whitish, dorsally tinged with light brown (Figs 3G, 7F, G). Everted proboscis white in colour (Fig. 3H).

Distribution: So far known only from the type locality, sublittoral, off Galicia, Spain, in the Atlantic Ocean (present study).

Etymology: The new specific name is a noun in the genitive case, in honour of Professor Victoriano Urgorri (University of Santiago de Compostela, Spain), who organized the DIVA-ARTABRIA II Expedition, in which the type material was collected.

Remarks: Baseodiscus urgorrii represents the fourth sublittoral congener recorded from the north-east Atlantic, after Baseodiscus alpha (Joubin, 1902), Baseodiscus abyssorum (Vaillant & Joubin in Joubin, 1902) and Baseodiscus filholi (Joubin, 1902). These can be distinguished by body colour and markings, except for B. alpha (see below).

Baseodiscus alpha, originally established as Eupolia alpha Joubin, 1902, is herein regarded as a nomen dubium, because the taxon was established without any information on external features in the living state; consequently, any future material would hardly be identifiable with certainty as this species. In addition, both the exact type locality and, more importantly, depth information for this species are uncertain due to a discrepancy in the sampling data. Joubin (1902: 205) noted that the type material was obtained in dredge haul 71 (LXXI) of the French steamer Talisman from a depth of 640 m off the coast of Sudan (Côte du Soudan) on 9 July 1883. According to Parfait (1884: 540) the dredge haul 71 of the Talisman 1883 expedition was taken on 8 July at a depth of 102 m off Western Sahara (26°04′N, 17°05′W); the word ‘Sudan’ historically referred to the region south of the Sahara, stretching from West Africa to eastern Central Africa (Parrinder, 1959: 131). Again, according to Parfait (1884: 538), among the 156 dredging sites of the Talisman 1883 expedition, the dredge haul at 640 m was number 66 off Western Sahara (26°18′N, 72°12′W). In any case, either the dredge-haul number (71) or the depth (640 m) provided by Joubin (1902) was probably incorrect.

Baseodiscus abyssorum differs from B. urgorrii in having red body colour. Originally described as Eupolia abyssorum Joubin, 1902, this species was based on three worm fragments procured among material dredged from the Bay of Biscay during a cruise of the French steamer Travailleur in 1880. The type locality of B. abyssorum is either 43°38′25″N, 6°28′40″W, 1353 m depth (dredge haul 6) or 43°35′30″N, 6°25′00″W, 1107 m depth (dredge haul 7). This ambiguity stems from possible confusion by Joubin (1902: 206), who noted ‘Dragage no VII D; Profondeur: 1353 m’ as the locality for the species, while the actual depth of dredge haul 7 seems to have been 1107 m (e.g. MilneEdwards, 1882: 126; Locard, 1898: 5). The external features of the species in the living state were described from coloured drawings of two fragments made by Léon Vaillant and later passed on to Louis Joubin. One fragment was uniformly bright red in colour; the other had transverse yellow rings spaced 2–3 mm apart on the same bright-red background. Joubin (1902) suspected that these represented the ventral and dorsal surfaces of the worm, respectively. Joubin (1902) ascribed Vaillant (in parentheses) as the author of the species name. Therefore, according to Recommendation 51E of the Code (ICZN, 1999), the authors of the species should be stated as ‘Vaillant & Joubin in Joubin, 1902 ’.

Baseodiscus filholi differs from B. urgorrii in having striated markings on the body. Baseodiscus filholi was originally established as Eupolia filholi by Joubin (1902) based on a specimen obtained in dredge haul 23 of the Talisman 1883 expedition at a depth of 120 m on 15 June. According to Parfait (1884: 534), the locality was off Morocco (33°16′N, 11°13′W), with the bottom sediment composed of rocks and shells. The body markings suggest that B. filholi may be synonymous with B. delineatus or B. curtus.