A new species of Eunicidae, Marphysa victori sp. n., has been identified from Arcachon Bay, Bay of Biscay, NE Atlantic. This new species, belonging to the sanguinea complex, is characterised by branchiae with long filaments from chaetigers 26–34, the presence of four types of pectinate chaetae with first ones present from chaetiger 2, a large number of both pectinate chaetae and compound spinigers, and the pygidium with only one pair of pygidial cirri. An identification key for European species of the genus Marphysa is provided.

Bait worms, eastern Atlantic, France, Marphysa , molecular, morphology, Polychaeta , taxonomy

In Arcachon Bay, blood worms of the genus Marphysa Quatrefages, 1866 are widely collected as bait both by recreational and professional fishermen. Since 2011, 13 companies (with a total of 26 employees) were operating in the lagoon and they recorded that 1.3–2.5 tons/year (wet weight) of Marphysa were collected which represents approximatively 400,000 worms. In reality, around 1 million of these worms could be fished each year in the bay. Most of these worms are shipped alive by air (in boxes with plant litter) to sellers situated on the western French Mediterranean coasts. Then, they are sold to recreational fishermen and used locally. Until now, these blood worms were misidentified as Marphysa sanguinea (Montagu, 1813), which was originally described from the south coast of Devon, UK (Hutchings and Karageorgopoulos 2003).

The family Eunicidae Berthold, 1827 is a very speciose family with nine genera and with more than 400 valid species distributed worldwide (Zanol and Read 2012). The genus Marphysa comprises around 81 nominal species with five valid species only known from European waters (Read and Bellan 2016): Marphysa bellii (Audouin & Milne Edwards, 1833), Marphysa fallax Marion & Bobretzky, 1875, Marphysa kinbergi McIntosh, 1910, Marphysa sanguinea and Marphysa totospinata Lu & Fauchald, 1998. Marphysa saxicola Langerhans, 1881 was recently transferred to the genus Nicidion Kinberg, 1865 (Arias and Nuñez 2016) and Marphysa simplex (Langerhans, 1884) should be regarded as an invalid species (Gil 2011). Finally, we consider that Marphysa grunwaldi (Risso, 1826) and Marphysa triantennata (Risso, 1826), described from French Mediterranean Sea, should be considered as nomen nuda because of very brief descriptions, lack of any figures, and absence of type material.

According to Fauchald (1970), species of the genus Marphysa can be grouped into four artificial groups based on the type of compound chaetae: no compound chaetae present (Group A), only compound spinigers present (Group B), only compound falcigers present (Group C) and both compound spinigers and falcigers present (Group D). Glasby and Hutchings (2010) added a fifth group, having compound spinigers only anteriorly and posterior segments only with simple limbate chaetae, and also encapsulating embryos in jelly cocoons. Each group can also then be divided into species having branchiae present only on anterior parapodia (subdivision 1) or branchiae present over most of the body (subdivision 2). In European waters, M. sanguinea is the only representative of the Group B2 currently reported.

Marphysa sanguinea has been recorded in Arcachon Bay by numerous workers (Lafont 1871; Boisseau 1962; Auby 1991; Blanchet 2004; Salvo 2010). However, all these papers just list the fauna present as a result of ecological studies without commenting on the species. It appears that no material was deposited in a museum and so could not be examined for this study. These records are not surprising as this species is originally described from the northern coast of the English Channel. Fauvel (1923) in his monograph of French polychaetes lists M. sanguinea and provides description and illustrations but without commenting on what material he examined. Nevertheless, recent re-descriptions of this species (Hutchings and Karageorgopoulos 2003; Hutchings et al. 2012) suggest that records of this species from outside the type locality should be checked, and that many records have been misidentified and represent new species (Zanol et al. 2016, 2017). Hutchings and Kupriyanova (2017) encourage taxonomists to check carefully their specimens.

Both morphological and molecular analyses confirm the existence of an undescribed species of Marphysa in Arcachon Bay. The present paper provides the description of this species as well as a key for European described species of this genus.

Marphysa sanguinea (Montagu, 1813) is the type species of the genus and has been widely reported from around the world. This is partly because the original description was very brief and poorly illustrated, and because all species superficially look similar. Hartman (1959) complicated the issue by synonymising several species with M. sanguinea with no explanation and the species joined a list of so-called “cosmopolitan species” (Hutchings and Kupriyanova 2017). Hutchings and Karageorgopoulos (2003) while trying to resolve the true identity of a commercially important species in Moreton Bay (Queensland, Australia) which had always been called M. sanguinea, examined material from SW England and designated a neotype of M. sanguinea and then redescribed the species. This then allowed the species from Moreton Bay to be described as a new species, and subsequently other species of Marphysa were described from along the east coast of Australia (Zanol et al. 2016, 2017). In the same way, a new species of the sanguinea group from French Atlantic coasts is described in this study. In Europe, only two species belong to the B2 group (Fauchald 1970). Marphysa victori sp. n. can be distinguished from M. sanguinea in having branchiae from chaetiger 26–34 (instead of 13–27), pectinate chaetae of four types (instead of two types, with an absence of anodont, asymmetrical pectinate chaetae with 2–4 large teeth), lacking subacicular hooks (see key above). Moreover, the neotype of M. sanguinea was described from south coast of England living intertidally in rocks which are easily identified and which are in a very different habitat to that of M. victori sp. n. (mudflats).

Three species are known to occur in Arcachon bay: M. bellii, M. fallax, and M. sanguinea. In the absence of specimens stored in a collection, it is very difficult to know how long M. victori sp. n. has been present in Arcachon Bay and confused with M. sanguinea. Moreover, the hypothesis that this new species is a non-indigenous species (NIS) cannot be completely dismissed. Arcachon Bay is one of the major French oyster farming sites with a production of 7,000–8,000 t per year of exotic Pacific cupped oyster Crassostrea gigas (Thunberg, 1793). In the early 1970s, the Portuguese cupped oyster Crassostrea angulata (Lamarck, 1819), which has been farmed in the bay since the end of the 19^th century, was decimated by a viral disease (Goulletquer et al. 2002). To sustain the local oyster industry, the exotic Pacific cupped oyster C. gigas was then introduced into Arcachon Bay between 1971 and 1975, as spat from Senday Bay, NE Honshu Island, Japan (1,176 t of spat collectors from 1971 to 1975) and as adults from British Columbia, Canada (137.5 t from 1971 to 1973) (Grizel and Héral 1991). Several non-indigenous species, probably introduced with oyster transfers, were recently found in Arcachon Bay (see references in Gouillieux et al. 2016). As M. victori sp. n. is very abundant close to oyster reefs, specimens could have been hitchhiked in oyster shells coming from Japan or Pacific coasts of USA. Worldwide, among the B2 group, only two species are characterized by the presence of four types of pectinate chaetae: Marphysa multipectinata (Liu, Hutchings & Sun, 2017) recently described from south coast of China and M. victori sp. n. Marphysa multipectinata differs from M. victori sp. n. in the appearance of pectinate chaetae (from chaetiger ~ 70 instead of chaetiger 2 for M. victori sp. n.), the maximal number of spiniger compound chaetae (27 vs >40 for M. victori sp. n.) and pectinate chaetae (22 vs 34 for M. victori sp. n.), the presence of subacicular hooks, the absence of inflated base of ventral cirri, the number of teeth of Mx II (3+3 vs 5+5 for M. victori sp. n.) and the presence of two pairs of pygidial cirri (instead of one single pair for M. victori sp. n.).

Alternatively, M. victori sp. n. could be native from Arcachon Bay and subsequently have been introduced into other European localities. Indeed, local oyster farmers often transfer their spat and juveniles between rearing areas in France (both on the Atlantic and Mediterranean coasts) (Goulletquer et al. 2002) or even to other European countries (Gouillieux et al. 2016). Moreover, thousands (probably millions) of specimens of M. victori sp. n. are shipped alive with litter to resellers situated on the western French Mediterranean coasts and then are used as bait by anglers. Recent studies have highlighted the possibility of these practises facilitating the introduction of invasive species (Olive 1994). Bait worm packaging are considered to be an important vector for transporting non-native algae, microorganisms and other invertebrates (Haska et al. 2012; Fowler et al. 2016). For example, a total of 114 taxa have been identified by Fowler et al. (2016) in baitworm shipments from Maine. Moreover, use of live baits contributes to the dispersal of worms in new marine ecosystems. Kilian et al. (2012) showed that a certain number of anglers in Maryland (USA) released their unused baits into the water at the end of a fishing trip. In this way, M. victori sp. n. might become a non-indigenous species in the Mediterranean Sea. Finally, the presence of M. victori sp. n. in driftwood could also lead to an extension of its geographical distribution in the Bay of Biscay via water currents.

To conclude, we suggest that all records of Marphysa from northern Europe need to be carefully checked to see if they represent a currently known species including M. sanguinea or represent an undescribed species. As well, the pattern of chaetal arrangement along the body need to be examined under the SEM, and combined with molecular data to correctly identify these species which often superficially resemble each other and vouchers need to be deposited in a museum.

We would like to thank Gaby Binois and Benoit Planella, the best bait fishers in Arcachon Bay for providing us with many complete specimens and for indicating the different locations in the bay where they collect the species. Many thanks to Benoit Gouillieux who provided us with some specimens. Sue Lindsay mounted the parapodia for the SEM and took the images. Finally, we also thank Joana Zanol, Greg Rouse, and an anonymous reviewer to provide helpful comments on the submitted manuscript.