Fig. 4A; Table 6
Campanularia gigantea Hincks, 1866: 297.
Clytia gigantea – Calder 2012: 46–47, figs 46–47. — Peña Cantero & Horton 2017: 13, fig. 5a–b. Clytia sp. – Ramil 1988: 254–256, pl. XVII.
SOUTH ATLANTIC OCEAN • 5 colonies, up to 13 mm high (2 growing on a ghost fishing net, 1 on Stegolaria geniculata), no gonothecae; Valdivia Seamount, stn BT12; 24°49′01″–24°47′38″ S, 6°24′40″–6°25′26″ E; 887– 886 m depth; 7 Feb. 2015; SEAFO-2015 leg.; SEAFO-2015-40552, SEAFO-2015-40582, SEAFO-2015-40811, SEAFO-2015-40852, SEAFO-2015-40857, LZM-UV slide R. 579.
Despite the fact that this species is currently included in the synonymy of Clytia hemisphaerica (Linnaeus, 1767) (Schuchert 2020), we agree with Calder (2012) who considers C. gigantea as a valid species, due to the comparatively larger size of its hydrothecae, provided with linguiform cusps, an opinion that was also later shared by Peña Cantero & Horton (2017). Moreover, Ramil (1988), in his study of the hydroids of Galicia (NW Spain), described this species as Clytia sp., apart from C. hemisphaerica, based on the same features highlighted by Calder (2012). Therefore, considering that both morphological features and measurements of our colonies coincide with those given by Ramil (1988), Calder (2012) and Peña Cantero & Horton (2017), we identify this material as C. gigantea.
The material studied here also resembles C. joycei Calder, 2019 in the hydrothecal shape; however, C. joycei is a shallow-water species, growing on the seagrass Thalassia testudinum K.D. Koening, 1805 and develops minute, stolonal colonies with comparatively smaller hydrothecae. These features typically separate C. joycei from C. gigantea (Calder 2019).
This species has been recorded from the boreal waters of the Northeast Atlantic (Calder 2012) to Galicia, NW Spain (Ramil 1988, as Clytia sp.) and also from Newfoundland to Cape Cod in the West Atlantic (Calder 2012). Its presence outside the Atlantic Ocean, including the Mediterranean Sea, is considered as doubtful by Calder (2012). The records from Chile (Leloup 1974; Galea et al. 2009) are based on misidentifications (Galea & Schories 2012). Its bathymetric distribution extends from 20 (Calder 2012) to 950 m (Peña Cantero & Horton 2017). Clytia gigantea is reported here for the first time from the South Atlantic, at Valdivia Seamount.