Sea slug night fever: 39 new records of elusive heterobranchs in the western Mediterranean (Mollusca: Gastropoda) Author Salvador, Xavier 0000-0003-3039-7566 Author Fernández-Vilert, Robert 0000-0002-2812-4414 Author Moles, Juan 0000-0003-4511-4055 text Journal of Natural History 2022 2022-05-18 56 5 - 8 265 310 http://dx.doi.org/10.1080/00222933.2022.2040630 journal article 10.1080/00222933.2022.2040630 38f6df24-838f-409a-90df-b56087e6a9bc 1464-5262 6758438 Placida tardyi ( Trinchese, 1874 ) ( Figure 6 (e)) Material examined Fòrum pools, Barcelona ( Spain ), 41°24 ʹ 34.5”N , 2°13 ʹ 36.8”E , 23 November 2017 , 0.4 m depth , 12 spcs, juveniles, adults and egg masses, L = 3–20 mm ; le Ponton , Étang de Thau , Sète ( France ), 43°25 ʹ 28.5”N , 3°42 ʹ E , 21 May 2018 , 0.5 m depth , 3 spcs, adults, L = 17–25 mm ; Cala Maset caves, Sant Feliu de Guíxols ( Spain ), 41°47 ʹ 10”N , 3°2 ʹ 44”E , 19 December 2018 , 2 m depth , 2 spcs, adults and egg masses, L = 10–15 mm ; 1 January 2019 , 1.3 m depth , 3 spcs, adults, L = 13–15 mm ; Cala Sa Tuna, Begur ( Spain ), 41°57 ʹ 38”N , 3°13 ʹ 52”E , 31 January 2019 , 0.5 m depth , 1 spc., juvenile, L = 3 mm ; Tamariu Beach ( Spain ), 41°55 ʹ 0.5”N , 3°12 ʹ 27.1”E , 10 September 2019 , 1 m depth , 4 spcs, adults with egg masses, L = 10–20 mm ; Punta de la Mona , Andalucía ( Spain ), 36°43 ʹ 12.9”N , 3°43 ʹ 43.1”W , 19 September 2020 , 2 m depth , 2 spcs, adults, L = 15–20 mm . External morphology Body elongate, narrow, background colour white and semi-transparent with a central white circle on dorsum. Lateral body parts and foot with dark brown or purple colour. Cerata long, smooth; background colour green, with white spots, tip dark garnet in colour. Rhinophores smooth, large, with white dots concentrated at apexes. Oral tentacles wide and short. Ecology Specimens found in masses of the green alga Bryopsis duplex , mating, and laying whitish and cylindrical egg masses at the base of the alga. This species can go completely unnoticed within the algal masses; moves actively at night. Distribution Originally described from Italy : Genoa ( Trinchese 1874 ), Gulf of Naples ( Gascoigne and Sordi 1980 ); also, Portugal ( Calado et al. 2003 ); Gibraltar ( Cervera et al. 1988 ); Spain : Andalusian coast (this study), Catalonia (this study); France (this study). Remarks This species can be misidentified as P. vidiris ( Trinchese, 1874 ) , but it is distinguishable by its brown or purple body margins and the tip of the cerata darkly coloured in garnet ( Pruvot-Fol 1954 ).