Campanularia gracillima Alder, 1856: 361 Lafoea gracillima : Jäderholm, 1909: 74 Calder, 2012: 29–30 Hydroids (Cnidaria, Hydrozoa) from Mauritanian Coral Mounds Gil, Marta Ramil, Fran Agís, José Ansín Zootaxa 2020 2020-11-16 4878 3 412 466  Calder, 2012: 29–30  3RVM3 (Alder, 1856) Alder 1856 [151,536,1302,1329] Hydrozoa Lafoeidae Lafoea Animalia Leptothecata 13 425 Cnidaria species gracillima      Campanularia gracillima Alder, 1856: 361, pl. 14, figs. 5, 6.     Lafoea gracillima: Jäderholm, 1909: 74, pl. 7, figs. 6, 7;  Calder, 2012: 29–30, fig. 28.   Material examined. MAURIT-0911, stn MUDR01, 16º08´24”N, 16º57´12”W,  488 m,  5-XII-2009: two colonies, without coppiniae.  MAURIT-0911, stn MUDR02, 16º08´50”N, 16º57´01”W,  462 m,  5-XII-2009: four colonies, no coppiniae.  MAURIT-1011, stn MUDR20, 16º08´11”N, 16º56´08”W,  405 m,  7-XII-2010: two colonies, no coppiniae.  MAURIT-1011, stn MUDR21, 16º28´13”N, 16º51´43”W,  522 m,  9-XII-2010: one colony 16 mmhigh, without coppiniae.   MSM 16/3, stn GeoB 14802–1, 20°14.791’N, 17°40.188’W,  595 m,  3-XI-2010: two colonies, one colony with four isolated hydrothecae rising from stolon on coral, no coppiniae.  MSM16/3, stn GeoB 14886–1, 18°39.013’– 18°38.476’N, 16°43.580’– 16°43.757’W, 484–640 m, 12-XI-2010: two colonies 10 mmhigh, one attached to  Acesta excavata, and the other one to  Madrepora oculata; no coppiniae.   Biology.This species has been found growing on shells and other hydroids ( Alder 1856) and on the stem of  Tubularia indivisa Linnaeus, 1758( Calder 2012). Jäderholm (1909)reported this species on rocky, shell and muddy bottoms in the Arctic Seas. The colonies studied by us were found growing on  M. oculata, an unidentified coral and the bivalve  A. excavata.   Distribution.  Lafoea gracillimais an Arctic and North Atlantic species distributed from Nantucket Sound in the west ( Calder 2012) to Mauritaniain the east ( Gil & Ramil 2017a). In West Africa, it was collected from Morocco[ Ramil & Vervoort 1992; Vervoort 2006, both as  Lafoea dumosa(Fleming, 1820)], Canary Islands ( Vervoort 2006, as  L. dumosa), Mauritania( Gil & Ramil 2017a) and Cape VerdeArchipelago ( Vervoort 2006, as  L. dumosa). The species was collected from depths of 20–30 m( Calder 2012) to 365 m( Jäderholm 1909). Many records of  L. gracillimawere included in  L. dumosaor  Lafoea fruticosa(Sars, 1851), and, currently, it is not possible to provide an accurate overview of its actual distribution and habitat. Our material was collected from depths of 405 to 640 m.   Remarks. Cornelius (1975)synonymised  L. gracillimaand  L. fruticosawith  L. dumosa, and his opinion was largely shared by later authors. In its current concept,  L. dumosais an almost cosmopolitan species with considerable variation in colony and hydrothecal morphology ( Vervoort 2006). Nevertheless, several authors have suggested the possibility of a species complex. Schuchert (2001)found differences in the measurements of the nematocysts of the stalkless  L. dumosaand pedicellate  L. fruticosa; Moura et al.(2008), using DNA barcoding, found two divergent genotypes within  L. dumosa, suggesting the possibility of a cryptic species. Finally, Calder (2012)maintained  L. gracillimaas a valid species different from both  L. dumosaand  L. fruticosa. During the study of this collection, we compared this material with the typical stalkless  L. dumosacollected from Galicia(Northwest Spain), and we are convinced that they are different species. Consequently, as per Calder (2012)we prefer to maintain  L. gracillimaas valid species. 3044195387 2009-12-05 MUDR 488 16.14 21 -16.953335 13 425 MUDR01 1 3044195370 [199,1388,1544,1571] 2009-12-05 MUDR 462 16.147223 21 -16.95028 13 425 MUDR02 1 3044195324 [199,1382,1580,1607] 2010-12-07 MUDR 405 16.136389 21 -16.935555 13 425 MUDR20 1 3044195338 2010-12-09 MUDR 522 16.470278 21 -16.861944 13 425 MUDR21 1 3044195314 2010-11-03 MSM 595 20.246517 1 -17.6698 13 425 MSM 16 1