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 Haloa japonica ( Pilsbry, 1895 ) ( Figure 2 (a)) Material examined Le Ponton , Étang de Thau , Sète ( France ), 43°25 ʹ 28.5”N , 3°42 ʹ E , 3 November 2017 , 2.1 m depth , 1 spc ., adult, L = 20 mm ; 14 April 2018 , 1.7 m depth, 3 spcs, adults, L = 20–30 mm ; 21 May 2018 , 1.9 m depth, 8 spcs, adults, L = up to 35 mm . External morphology Shell external, translucent, background colour brown with large orange punctuations. Parapodia darker on top. Head lighter on edge, with darker central part between the eyes. Ecology Found at night on soft bottoms, between Ceramiales algal species and other red algae. Individuals found during April and May 2018 were mating. Distribution Japanese coast ( Pilsbry 1895 ); USA ( Hanson et al. 2013 ; GBIF.org 2021); Italy ( Crocetta et al. 2013 ); Atlantic Spanish coast: Galicia and Cantabria; Mediterranean Spanish coast: Andalucía ( Cervera et al. 2004 as Haminoea cadillegenita ); Mediterranean French coast ( Hanson et al. 2013 ; this study). Remarks In the marine pools along the French south-eastern Mediterranean coast there are several marine species of Japanese origin, such as the alga wakame [ Undaria pinnatifida (Harvey) Suringar, 1873 ] and the oyster [ Magallana gigas (Thunberg, 1793) ], so their presence may be caused by aquaculture (e.g. Faasse 2018 ). Genus Haminoea Turton and Kingston [in Carrington], 1830