(Figure 4 (h))
Material examined
Punta del Romaní, L’Escala (Spain), 42°6 ʹ 54”N, 3°10 ʹ 9”E, 10 February 2014, 7 m depth, 1 spc., juvenile, L = 3 mm; 14 February 2015, 14 m depth, 1 spc., adult, L = 10 mm; Le Ponton, Étang de Thau, Sète (France), 43°25 ʹ 28.5”N, 3°42 ʹ E, 14 April 2018, 1 m depth, 3 spc., adults, L = 7–20 mm; Cala Maset caves, Sant Feliu de Guíxols (Spain), 41° 47 ʹ 10”N, 3°2 ʹ 44”E, 15 April 2018, 0.6 m depth, 15 spcs, juveniles, adults and egg masses, L = 4–15 mm; 6 June 2018, 0.6 m depth, 20 spcs, adults and egg masses, L = 10–15 mm; 11 March 2020, 0.5 m depth, 12 spcs, adults and mating, L = 7– 15 mm; Tamariu beach (Spain), 41°55 ʹ 0.5”N, 3°12 ʹ 27.1”E, 11 February 2019, 2 m depth, 4 spcs, adults, L = 6–10 mm.
External morphology
Body elongate, narrow, background colour white or light yellow. Rhinophores and oral tentacles smooth, more intensely white than the body. Red or orange mark between eyes and on central dorsum. Cerata globular, displaying a bright yellow-blue-yellow colouration.
Ecology
Specimens found mating and laying the eggs on the hydrozoans Sertularella mediterranea Hartlaub, 1901 and Sertularella polyzonias (Linnaeus, 1758) inside superficial caves.
Distribution
North-east Atlantic (Korshunova et al. 2019); Adriatic Sea (Ballesteros et al. 2012–2021); Mediterranean French coast (this study); Spain: Catalonia (this study).
Remarks
This species was recently described and observed in the North Atlantic and Mediterranean Sea (Korshunova et al. 2019). It is different from similar Trinchesia species by having one light or pale red marking between the eyes and in the middle part of the back. This species likely has a shorter life cycle than T. morrowae (Korshunova et al. 2019), since it has only been observed in the winter and spring months, whereas T. morrowae is observed yearround. Trinchesia caerulea (Montagu, 1804) has been found only during spring and autumn and is usually found in deeper waters than T. cuanensis (X. Salvador pers. obs.).
Order PTEROPODA Cuvier, 1804
Family CRESEIDAE Rampal, 1973
Genus Creseis Rang, 1828