Pagurus alatus Fabricius 1775

Pagurus alatus Fabricius, 1775

(Fig. 15)

Pagurus alatus Fabricius, 1775: 411.

Eupagurus variabilis Milne-Edwards & Bouvier, 1892: 217.— Selbie, 1921: 36, pl. IV figs. 4, 5, pl. V figs. 1–3. Pagurus alatus. — Ingle, 1985: 765 (key); 1993: 33 (key) 136, figs. 109–112 (lit.). not Eupagurus alatus. — Forest, 1955: 110, fig. 23, pl. V figs. 2 and 3 (= P. excavatus) not Pagurus alatus.— Zariquiey, 1968: 247, figs 89e, 90b, o, 91e (= P. excavatus)

Material examined. MU57, 430– 406 m, (1); MU120, 109– 105 m, (1); MU142, 109– 112 m, (1); MU158, 80– 98 m, (2); MU207, 88– 117 m, (1); MU260, 101– 120 m, (1); MUBV 20, 155 m, (5); MUBV 21, 107– 109 m, (31).

Males: 3.06–6.56 mm, females: 3.10–3.40 mm, ovigerous females: 3.01–4.03 mm

Habitat. This species is characteristic of bathyal muds (d’Udekem d’Acoz 1999; Follesa et al. 2009; Mura et al. 2006), but is also reported on sand (Pipitone & Arculeo 2003) and on bottoms of sand, silt, coarse sands and gravel by Serrano et al. (2011).

Pagurus alatus was found inhabiting shells of the gastropod species Colus islandicus (Mohr, 1786) in Cap Breton Canyon (Bay of Biscay) (Urzelai et al. 1990). In symbiosis with this crab were the cnidarians Adamsia palliata (Müller, 1776), Calliactis parasitica (Couch, 1842), Epizoanthus paguriphylus Verrill, 1883, Paracalliactis mediterranea Ross and Zamponi, 1982 and the polychaete Neanthes fucata (Savigny, 1818) (Williams & McDermott 2004).

Our specimens were collected mainly on sandy bottoms, but also on sandy-mud bottoms. They were found inhabiting shells of the gastropods Aspa marginata (Gmelin, 1791), Calliostoma granulatum (Born, 1778), Euspira grossularia (Marche-Marchad, 1957), Euspira subplicata (Jeffreys, 1885), Nassarius arcadioi Rolán & Hernández, 2005, Natica canariensis Odhner, 1932, Ranella olearium (Linnaeus, 1758) and in a shell of the genus Genota. As epibionts over gastropod shells we found Demospongia, two different actinian species, some specimens of Anomiidae bivalves, one acorn barnacle and some tubes of Serpulidae polychetes. Over the chelipeds and ambulatory legs we identified the hydrozoan Leuckartiara octona (Fleming, 1823).

Distribution. Eastern Atlantic, from Iceland, Norway, the Shetland Islands and the North Sea southwards to Mauritania, including the Canary Islands and the Mediterranean Sea (d’Udekem d’Acoz 1999). The record from Loos Islands (Guinea) (Forest 1955) belong to P. excavatus (see remarks). Bathymetrical range varies from 5–10 m (Pipitone & Arculeo 2003) to 1430–1505 m (García Raso 1996), although the species is mainly found around 150 m depth (d’Udekem d’Acoz 1999).

Further records were from the Bay of Biscay (Urzelai et al. 1990; Serrano et al. 2006; Cartes et al. 2007; Sánchez et al. 2008; Serrano et al. 2011), off Portugal (Monteiro et al. 2001) and the Mediterranean Sea (Koçak et al. 2001; Abelló et al. 2002; Biagi et al. 2002; Pipitone & Arculeo 2003; Colloca et al. 2004; Company et al. 2004; Ungaro et al. 2005; Mura et al. 2006; Ates et al. 2006; Fanelli et al. 2007; Cartes et al. 2009; Follesa et al. 2009; Papiol et al. 2012).

Remarks. Our specimens coincide with the descriptions and figures given by Ingle (1993).

The taxonomic status of P. alatus, P. excavatus and P. variabilis has been controversial for many years. The differences between P. excavatus and P. variabilis were established by A. Milne-Edwards & Bouvier (1900). Following that opinion, Selbie (1921) indicated that the most reliable features to separate both species were the number of unpaired pleopods in males (three in P. variabilis and four in P. excavatus) and the length of the dorso-outer process of the antennal peduncular segment 2 that reaches, or passes, the base of the terminal joint in P. alatus but not in P. excavatus.

Forest (1955: 109) also followed this differentiation, considering P. excavatus to be identical to P. alatus (the latter name having priority) and different from P. variabilis. This author also indicated the presence of two Pagurus (as Eupagurus) groups in West Africa, the first group including P. alatus, with four unpaired pleopods in males (a feature of the current concept of P. excavatus), and the second group, including P. variabilis, with three unpaired pleopods in males (a feature of the current concept of P. alatus). Forest opinion was shared by Zariquiey (1968).

Based on Selbie (1921), Ingle (1985) indicated that there were no consistent records of P. excavatus north of the southern part of the Bay of Biscay. Taking into account that P. alatus was described after material collected in Iceland, Ingle concluded that P. alatus and P. excavatus were two different species and reinstated P. excavatus as a valid species. In addition, Ingle (1985) considered P. variabilis, whose distribution was more boreal, to be a junior subjective synonymy of P. alatus.

Ingle (1993) provided a complete synonymy for P. alatus and P. excavatus, which is currently accepted. Nevertheless, the report of P. alatus in Forest (1955) from Loos Islands and Zariquiey (1968) from the Iberian Peninsula should be definitively included in P. excavatus.