Hermaea bifida (Montagu, 1816)

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 : 295-297

Hermaea bifida (Montagu, 1816)

( Figure 6 (a))

Material examined

Cala d’Aiguafreda, Begur ( Spain), 41°57 ʹ 49”N, 3°13 ʹ 41”E, 31 March 2017, 1 m depth, 9 spcs, adults, L = 7–12 mm; 25 December 2017, 1 m depth, 5 spcs, adults and juveniles; Cala Maset caves, Sant Feliu de Guíxols ( Spain), 41°47 ʹ 10”N, 3°2 ʹ 44”E, 31 December 2017, 0.7 m depth, 2 spcs, juvenile and adult, L = 2–6 mm; 8 March 2018, 1.4 m depth, 2 spcs, adults and egg masses, L = 12 mm; Cala Sa Tuna, 41°57 ʹ 38”N, 3°13 ʹ 52”E, 3 January 2018, 0.8 m depth, 4 spcs, adults, L = 5–7 mm; Punta del Romaní, L’Escala ( Spain), 42°6 ʹ 54”N, 3° 10 ʹ 9”E, 6 January 2018, 0.7 m depth, 1 spc., juvenile, L = 2 mm; Cala Trons, Lloret de Mar ( Spain), 41°41 ʹ 57”N, 2°51 ʹ 52”E, 20 January 2018, 1.7 m depth, 1 spc., adult, L = 12 mm.

External morphology

Body elongate, narrow, background colour red and semi-transparent, with dispersed white dots concentrated around head, cerata and rhinophore apexes. Cerata globular, leaf-shaped, semi-transparent, with internal lines of red colour running towards apex and surrounded by four tubercles. Rhinophores beige, internally rolled, bifid with superior apex slightly longer than inferior one.

Ecology

Specimens were found on the red alga Bornetia secundiflora (J.Agardh) Thuret, 1855 , where they were mating and laying the eggs. The egg mass is whitish, cylindrical and ‘C’-shaped ( Figure 5 (b), close-up); they were laid under the algae, around B. secundiflora but not on it.

Distribution

Central American coast and England (iNaturalist.org 2021); Portugal ( Cervera et al. 2004); Gibraltar ( García-Gómez 2002); Spain: Galicia ( Rolán 1983), Andalucía ( Cervera et al. 1988), Levantine coast ( Templado 1982; Templado et al. 1983, 1984; Marín and Ros 1988), Balearic Islands, Spain (GROC 2009–2021), Catalonia ( Ballesteros et al. 2016; this study); France ( Rudman 2021).

Remarks

In the Spanish Balearic Islands this species was reported on the invasive alga Lophocladia lallemandii (Montagne) F. Schmitz, 1893 ( GROC 2009–2021 ), off Catalonia we commonly found it on B. secundiflora ; juvenile specimens had a fluorescent orange colouration on their cerata, similar in colour to the latter alga.

Figures

Figure 5. Photographs of live Pteropoda species: (a) Creseis virgula. (b) Hyalocylis striata. (c) Peracle reticulata. (d) Pneumodermopsis canephora. Runcinida: (e) Runcina ornata. Sacoglossa: (f) Aplysiopsis elegans. (g) Caliphylla mediterránea. (h) Cyerce graeca.

Figure 6. Photographs of live Sacoglossa species: (a) Hermaea bifida and close-up on its egg mass at the base of an alga. (b) Hermaea cantabra. (c) Hermaea paucicirra. (d) Limapontia capitata on Ulva lactuca. (e) Placida tardyi. (f) Placida viridis. (g) Elysia flava. Siphonariidae: (h) Williamia gussoni.