Palio nothus ( Johnston, 1838 )

Salvador, Xavier, Fernández-Vilert, Robert & Moles, Juan, 2022, Sea slug night fever: 39 new records of elusive heterobranchs in the western Mediterranean (Mollusca: Gastropoda), Journal of Natural History 56 (5 - 8), pp. 265-310 : 275-276

Palio nothus ( Johnston, 1838)

( Figure 3 (a))

Material examined

Cala Maset caves, Sant Feliu de Guíxols ( Spain), 41°47 ʹ 10”N, 3°2 ʹ 44”E, 16 January 2018, 1.7 m depth, 5 spcs, adults and egg masses, L = 8–14 mm; 7 May 2018, 1.4 m depth, 1 spc ., adult and egg masses, L = 15 mm; L = 8–14 mm; 11 March 2020, 2 m depth, 7 spcs, juveniles.

External morphology

Body short, thick, background colour black with numerous white papillae. Mantle margin white. Rhinophores with lamellae, beige or white. Branchial leaves dark brown.

Ecology

Specimens were found mating and laying the egg masses on the bryozoans Amathia lendigera (Linnaeus, 1758) at the entrance of a cave, on overhangs. Egg masses were white with a soft brown colour and laid in a ‘C’ shape over the bryozoans. Juvenile specimens, only found in 2020, were also crawling on A. lendigera . Slugs are more active at night and may go unnoticed by divers and other observers during the day.

Distribution

North Sea ( England and Norway; Johnston 1838; Evertsen and Bakken 2013); Mediterranean Spanish coast: Catalonia ( Ballesteros et al. 2016; this study).

Remarks

This species apparently has an Amphi-Atlantic and Boreo-Arctic distribution, but its identity may need confirmation since is easily confused with Palio dubia (M. Sars, 1829) ; therefore, several records may have been misidentified ( Thompson and Brown 1984).

Genus Polycera Cuvier, 1816

Figures

Figure 3. Photographs of live Nudibranchia species: (a) Palio nothus and its egg mass. (b) The alien Polycera hedgpethi. (c) Polycerella emertoni and egg mass on Amathia verticillata. (d) Thecacera pennigera on top of the bryozoan Bugula sp. (e) Two specimens of Anteaeolidiella lurana and their egg masses. (f) Doto cervicenigra. (g) Doto fragilis (photo credit: Oriol Planas). (h) Doto pygmaea.