Hydromedusae observed during night dives in the Gulf Stream Author Schuchert, Peter Muséum d’histoire naturelle, C. P. 6434, CH- 1211 Genève 6, Switzerland peter.schuchert@ville-ge.ch Author Collins, Richard 880 NE 33 rd Street, Boca Raton, Florida, USA rc6684@icloud.com text Revue suisse de Zoologie 2021 2021-10-21 128 2 237 356 journal article 10.35929/RSZ.0049 172fa5c5-c0c4-4bd7-b710-d608237b8458 0035-418 5639938 Corymorpha gracilis ( Brooks, 1883 ) Fig. 25 A-B Steenstrupia gracilis Brooks, 1883: 144 . Steenstrupia rubra . – Mayer, 1910: 31 , pl. 1 fig. 7. [not Steenstrupia rubra Forbes, 1848 = Corymorpha nutans M. Sars, 1835 ] Euphysora gracilis . – Kramp, 1959a: 89 , fig. 40a. – Kramp, 1961: 40 . – Goy, 1979: 269 , fig. 2. Corymorpha gracilis . ‒ Nagata et al ., 2014: 299 , fig. 9. not Euphysora gracilis – Pagès et al., 1992: 20 , fig. 18. Examined material: BFLA4368 ; 1 specimen ; size 4 mm ; preserved in ethanol for DNA extraction; 16S sequence MW528715 . – BFLA4401 ; 1 specimen ; size 6 mm ; preserved in ethanol for DNA extraction; 16S sequence identical to MW528715 . Observations: Umbrella bell-shaped, height 4 to 6 mm , about two times higher than wide, with very large, pointed apical process, often of the same size as the umbrella. No gastric peduncle. Manubrium tubular with some tapering towards mouth, length about 1/2 to 4/5 of the subumbrellar height, with long, conspicuous apical canal entering apical process ( Fig. 25 A-B), distal end often somewhat thickened and yellow in colour. Gonads wrapping manubrium entirely without perradial interruptions. Marginal tentacles of distinct types , one long, extensible tentacle with up to 7 large, oblong nematocyst clusters encircling tentacle entirely, some smaller annular nematocyst, clusters can be present, terminal cluster oblong and slightly thicker than annular ones. The annular clusters may be absent and only a few small clasping clusters can be present (likely in regeneration after tentacles loss). Other tentacles reduced to mere cones, the one opposite the longer tentacle about twice as long as the other two. Radial canals fine, but well visible due to white-yellowish pigmentation. Gastrodermis of tentacles with some red hues. 16S Data: A blastn search in GenBank using the sole 16S indicated Corymorpha nutans as best match, although with only 89% identity. This species was followed by other Corymorpha and Aplanulata species with similar low identity scores. Distribution: Atlantic cost of the USA from New England to Florida ( Brooks, 1883 ; Kramp 1959 ); Brazil ( Kramp, 1959 ; Nagata et al., 2014 ); South Atlantic ( Goy, 1979 ). Doubtful records from the Benguela current ( Pagès et al ., 1992 ). Type locality: USA , North Carolina , Newport River. Remarks: The specimen depicted by Pagès et al. (1992) and identified as Euphysora gracilis (syn. Corymorpha gracilis ) lacked the typical large apical projection with the gastrodermal process in it. It is therefore not unambiguously attributable to Corymorpha gracilis .