INTRODUCTION
The nudibranch Godiva quadricolor (Barnard, Reference Barnard1927) (Nudibranchia: Facelinidae) is characterized by a pale slender body, with a long tapering tail and numerous blue, yellow and orange cerata. The head is orange, the rhinophores wrinkled and the oral tentacles are long, with a white stripe on them. It feeds on sea anemones and other nudibranchs (Barnard, Reference Barnard1927; Gosliner, Reference Gosliner1987).
This species represents a curious case in terms of geographic distribution; first collected in 1912 in False Bay, South Africa, it was described in 1927 (Barnard, Reference Barnard1927) and nowadays it is considered to be common in shallow waters along the whole east coast of South Africa (Macnae, Reference Macnae1954; Gosliner, Reference Gosliner1987; Fraser, Reference Fraser2001). In 1954, it was recorded in Inhaca, Mozambique (Macnae, Reference Macnae1954), and three years later the same author found the species in the estuarine complex of the Zwartkops River (Port Elizabeth, South Africa) (Macnae, Reference Macnae1957); at these sites, Godiva quadricolor was always found in intertidal areas, on and under stones or in Zostera meadows. The subsequent synonymy with Godiva rachelae Rudman, 1980 extended the distribution range of Godiva quadricolor up to Dar es Salaam, Tanzania (Willan, Reference Willan2004). In 1977, the species was recorded in the Atlantic Ocean for the first time, in a boat hull in Ghana (Edmunds, Reference Edmunds1977). In 1985, it was reported stable and very abundant in Fusaro Lake, a brackish lagoon with a narrow connection to the sea, located in the Gulf of Naples (Mediterranean Sea) (Villani & Martinez, Reference Villani and Martinez1993), but was erroneously reported as Facelina coronata because of a misidentified picture in Cattaneo-Vietti et al., Reference Cattaneo-Vietti, Chemello and Giannuzzi-Savelli1990; the mistake was pointed out by Cervera in Reference Cervera2002. In October 2011, about 20 specimens were found in Pialassa della Baiona, a lagoon directly connected with the North Adriatic Sea and Ravenna Harbour, but researchers successively failed in finding any other specimens, suggesting that the 2011 findings were an occasional bloom (A. Rinaldi, personal communication); it was however hypothesized that the species could have also been present in other Italian lagoons (Crocetta, Reference Crocetta2012). In 1987, Godiva quadricolor was recorded in Fremantle and Cockburn Sound, Western Australia (Willan, Reference Willan1987), and in 2004 it reached the coasts of South Queensland; at both sites, this species is now considered established (Willan, Reference Willan2004). In 2010, the species was found in the north-east Atlantic Ocean, in particular in Morocco, and in the Strait of Gibraltar (Algeciras Bay); moreover, one specimen was found in an aquaculture tank in Salobreña, close to Granada (Cervera et al., Reference Cervera, Tamsouri, Moukrim and Villani2010).
So far, Godiva quadricolor has been found in both tropical and temperate waters, mainly in the intertidal area of brackish lagoons; as pointed out by Cervera et al. (Reference Cervera, Tamsouri, Moukrim and Villani2010) and Willan (Reference Willan2004), it is usually found in areas subjected to important maritime traffic and high anthropization, suggesting that the species, endemic to South Africa, was most likely introduced to other regions through ballast waters. A review of the actual distribution is shown in Figure 1A.
Godiva quadricolor distribution: (A) map of the actual distribution (in yellow, the new record); (B) map of the coast, with Vado Ligure Harbour and the SCI “Fondali Noli – Bergeggi” (in purple); (C) map of the area of the record (black spot) with the border of the first sub-site of the SCI (in purple) and the biocenosis (in green, Posidonia oceanica meadows; in greenish-brown, dead matte of Posidonia oceanica; in grey, sand; in orange, mud). Map B and C obtained through MACISTE software (http://www.remare.org/cartografia-amp-maciste).
In the last decades, the Mediterranean Sea has been subjected to an increasing ingression of alien species, mainly due to the warming of shallow waters, which promotes the entrance and the establishment of tropical species from Gibraltar and the Suez Channel, and to marine traffic and aquaculture (Galil, Reference Galil2009; Zenetos et al., Reference Zenetos, Gofas, Morri, Rosso, Violanti, Garcia Raso, Cinar, Almogi-Labin, Ates, Azzurro, Ballesteros, Bianchi, Bilecenoglu, Gambi, Giangrande, Gravili, Hyams-Kaphzan, Karachle, Katsanevakis, Lipej, Mastrototaro, Mineur, Pancucci-Papadopoulou, Ramos Esplà, Salas, San Martin, Sfriso, Streftaris and Verlaque2012). Molluscs are the dominant taxa of the alien species in the Mediterranean Sea, with more than 200 recorded species (Zenetos et al., Reference Zenetos, Gofas, Morri, Rosso, Violanti, Garcia Raso, Cinar, Almogi-Labin, Ates, Azzurro, Ballesteros, Bianchi, Bilecenoglu, Gambi, Giangrande, Gravili, Hyams-Kaphzan, Karachle, Katsanevakis, Lipej, Mastrototaro, Mineur, Pancucci-Papadopoulou, Ramos Esplà, Salas, San Martin, Sfriso, Streftaris and Verlaque2012). In Italy, 35 mollusc alien taxa are known, of which 18 are gastropods and 12 are Opisthobranchia (Crocetta, Reference Crocetta2012). Due to its low winter water temperatures, it appears to be difficult for the Ligurian Sea to be colonized by alien species (Astraldi et al., Reference Astraldi, Bianchi, Gasparini and Morri1995; Brasseur et al., Reference Brasseur, Beckers, Brankart and Schoenauen1996).
MATERIAL AND METHODS
The coast between the town of Bergeggi and the Noli Cape is partially protected by the MPA ‘Isola di Bergeggi’ and the Site of Community Importance (SCI) IT1323271 ‘Fondali Noli – Bergeggi’, which covers different habitats, such as submerged sandbanks, Posidonia oceanica beds, rocky reefs and caves (Figure 1B, C). Several investigations, by means of snorkelling activities and scuba diving, are regularly carried out during the year by the authors, monitoring the environment and the species living in the whole area; Godiva quadricolor was observed during a scuba dive on 21 October 2014, inside the borders of the first of the four sub-sites of the SCI, between the town of Noli and the homonymous cape, at the WGS 84 coordinates 44°12′07″N 08°25′12″E. Underwater pictures of the animal were taken using a Nikon D7000 in Isotta housing, equipped with a Nikon Nikkor 60 mm micro lens and two Sea & Sea external strobes.
A review of the existing literature regarding the distribution of G. quadricolor was performed to better describe the novelty of information provided by this new record.
RESULTS
One specimen of Godiva quadricolor was found in the study area (Table 1). The record is based on the in vivo examination of the specimen and identification was confirmed by the underwater pictures (Figure 2). It was easy to spot, crawling on the surface of small stones, at a depth of 3.5 m, about 10 m away from the shore, on a plateau; the water temperature was 20°C. The total length, measured underwater, was 4 cm.
Underwater picture of the specimens of Godiva quadricolor reported in the present paper.
Summary of Godiva quadricolor records in the Mediterranean Sea.
The main features of the species, such as the colour pattern and the wrinkled rhinophores, perfectly match the original description (Barnard, Reference Barnard1927) and in particular the detailed analysis performed by Willan (Reference Willan2004).
DISCUSSION
This report represents the northernmost record of this species, about 400 km farther north than the previous record from Fusaro Lake and the farthest to be recorded from the equator. It is also the second record of Godiva quadricolor to be made along the Italian coasts and the first for the whole Ligurian Sea. Moreover, while the species is typically found in brackish waters and lagoons, the Ligurian specimen was found in an open shore area; its proximity to Vado Ligure Harbour, about 7 km north, may also suggest in this case, as reported in literature, an introduction of the species via shipping transportation. The same introduction pattern is plausible for the Moroccan specimens found by Cervera et al. (Reference Cervera, Tamsouri, Moukrim and Villani2010) in Aghroud and Anza, both in the proximity of the important harbour of Agadir, and for the Pialassa della Baiona specimens, close and directly connected to Ravenna Harbour. Further observations are required to know if the presence of this alien species is occasional and restricted to the Noli coast, or if it is more widespread along the Ligurian Sea.
ACKNOWLEDGEMENTS
The authors would like to thank Dr Attilio Rinaldi (Fondazione Centro Ricerche Marine Cesenatico, Italy) for the important data regarding the presence of Godiva quadricolor in the Adriatic Sea.
