Polycera hedgpethi Er. Marcus, 1964

(Figure 3 (b))

Material examined

Le Ponton, Étang de Thau, Sète (France), 43°25 ʹ 28.5”N, 3°42 ʹ E, 8 April 2017, 1.2 m depth, 7 spc., adults and egg masses, L = 10–25 mm; 4 October 2017, 0.8 m depth, 3 spcs, adults, L = 20–25 mm; 21 May 2018, 1.5 m depth, 1 spc., adult, L = 45 mm; 1 November 2018, 1 m depth, 5 spcs, adults and egg masses, L = 15–30 mm; l’Espigó, Roses (Spain), 42°15 ʹ 39.8”N, 3°10 ʹ 26.8”E, 28 February 2020, 0.6 m depth, 8 spcs, adults and egg masses, L = 10–20 mm.

External morphology

Body short, thick, background colour black. Mantle margin white with numerous appendages of black and yellow, yellow close to apex, white papillae scattered all over body. Rhinophores lamellar, black forwards and white backwards, yellow on top. Gill leaves black, tips yellow.

Ecology

All specimens in each locality were found in shallow waters on the bryozoan Bugula neritina (Linnaeus, 1758), feeding and laying the egg masses.

Distribution

Originally from the north-central Pacific coast of America, this species is reported from Australia, Japan, South Africa, Morocco (Moro et al. 2017); Cantabrian Sea (Cervera et al. 2004); and in the Mediterranean Sea from Italy, Croatia (Servello et al. 2019); France (GBIF. org 2021; this study); and Spain: Catalonia (this study).

Remarks

Its bryozoan prey grows on boat hulls, and thus movement via boats could be responsible for this species’ range expansion. However, although this bryozoan is abundant at marine ports, P. hedgpethi has not been recorded in biofouling samples containing B. neritina (X. Salvador pers. obs.). Notably, this species, when found in the Mediterranean, is often in environments with variable salinity, such as the Étang de Thau, or the Espigó de Roses, where there is a fresh water supply.

Genus Polycerella A.E. Verrill, 1880