(Figs 1–3)
Scolecolepis viridis Verrill, 1873: 345, 600–601.
Marenzelleria viridis: Maciolek 1984 (Part.): 51–55, fig. 2. Atkins et al. 1987: 311–320, fig. 2. Bastrop et al. 1995: North Sea population. Röhner et al. 1996a: North Sea population. Dauer 1997: 512–515, figs 1, 2 (palp morphology). Sikorski & Bick 2004 (Part.): 261–264, figs 2C, 3B, 4A–F. Bastrop & Blank 2006: 1197–1199. David & Williams 2016: 821–827, figs 1–5 (regeneration). Whitford & Williams 2016: 357–367, figs 1–3 (regeneration). Kauppi et al. 2018: 48–55. Wasmund et al. 2018: 78. O’Reilly & Nowacki 2019: 1–4, fig. 1.
Scolecolepides viridis: Hartman 1942: 13. George 1966: 76–92, figs 1–21 (adult, gamete and larval morphology). Foster 1971: 37–40, figs 57–65.
Scolelepides viridis: Hartman 1944: 340.
Marenzelleria jonesi Maciolek, 1984: 55–58, figs 3, 4. Fide Rodi & Dauer 1996: 72.
Marenzelleria type I: Röhner et al. 1996b: 279–281. Bastrop et al. 1997: 125–127; 1998: 98–102. Fide Sikorski & Bick 2004: 264.
Marenzelleria cf. wireni: Bick & Zettler 1997: 138–141, figs 1, 2. Fide Sikorski & Bick 2004: 264.
Scolecolepis tenuis Verrill, 1873: 345, 601. Fide Foster 1971: 37.
Remarks. Verrill (1873) described Scolecolepis viridis based on material from Connecticut, Massachusetts, New Jersey, and Rhode Island, USA. Maciolek (1984) transferred Verrill’s species to Marenzelleria. Sikorski & Bick (2004) established a lectotype and designated the type locality for M. viridis as Naushon Is., off Martha’s Vineyard, Massachusetts (Fig. 2). They also referred to this species Marenzelleria Type I, which was earlier distinguished in genetic studies by Röhner et al. (1996a, b) and Bastrop et al. (1997, 1998). Invasion of North American M. viridis into northern European waters resulted in numerous studies on this species (see brief review in the Introduction).
In Europe, M. viridis was collected for the first time in 1979 from the western part of the North Sea: Fourth Estuary (Scotland) (Elliott 1983; Elliott & Kingston 1987; as M. wireni). In 1983, it was recorded from the southern part of the North Sea: Ems Estuary (The Netherlands / Germany) (Essink & Kleef 1988). In the late 1980s–1990s, M. viridis spread over the North Sea and also appeared in the Baltic Sea (see reviews by Essink & Kleef 1993; Röhner et al. 1996b; Bastrop et al. 1997; Zettler 1997; Essink 1999; Olenin & Leppäkoski 1999; Leppäkoski & Olenin 2000; Simm et al. 2003; Bastrop & Blank 2006; Blank & Bastrop 2009; Kauppi et al. 2017, 2018).
We collected M. viridis from the Oslofjord in October 2018 and here for the first time report the species for Norwegian waters. Two collected specimens had about 20 narrow yellowish-brown bands on each palp. However, this species was first collected in the region in 2008. A single Marenzelleria specimen was collected from Idefjorden (see VIR ID 24704 in Table S1) and photographed by Fredrick Pleijel in June 2008 (Fig. 3B). Idefjorden is next to the Oslofjord, separating the southern parts of Norway and Sweden (Fig. 3A). The specimen was not preserved, but, according to the features shown on the picture (i.e., about 20 narrow dark bands on each palp, arrangement of branchiae), we identify it as M. viridis.
Marenzelleria viridis was reported from San Francisco Bay (California) based upon specimens collected during the Benthic Pilot Study (BPS) in 1994–1997 (Cohen & Carlton 1995; Thompson et al. 2000, 2013; Ranasinghe et al. 2012) and Rapid Assessment Survey (RAS) for Exotic Species in May 2004 (Cohen et al. 2005). No samples were left in public museums from the BPS 1994–1997, but Sikorski & Bick (2004) identified Marenzelleria collected from that same area (Grizzly Bay, a northern embayment of San Francisco Bay; SIO BIC A 660, ZSRO P-869) in 1999 as M. neglecta. Moreover, Leslie H. Harris, who first identified specimens from the RAS-2004 as M. viridis, re-examined the same specimens after the publication of Sikorski & Bick (2004) and referred them to M. neglecta (Harris, L.H., in litt. 2 June 2021). The taxonomists at the San Francisco Public Utilities Commission’s Marine Biology Laboratory, who identified M. viridis specimens cited in Cohen & Carlton (1995), Thompson et al. (2000, 2013) and Ranasinghe et al. (2012), also re-assessed them as M. neglecta following Sikorski & Bick (2004) (Norris, D., pers. comm.). We assume that it might be the only Marenzelleria species widely distributed in San Francisco Bay in areas with low salinity.
Carr et al. (2011) reported M. viridis from St. Andrews (New Brunswick, Canada). However, the photos of two specimens (NBPOL181–08, NBPOL262–08) provided by the authors in BOLD (http://boldsystems.org) clearly show features characteristic for Spiophanes Grube, 1860: absence of branchiae, and enlarged neuropodial lamellae of chaetigers 5–13(14) bearing glandular organs. We compared the COI sequences of these specimens (HQ024089, HQ024090) provided by Carr et al. (2011) with those of other spionids and found them nested among Spiophanes, probably representing a new and not yet described species.
Chertoprood et al. (2004) reported M. viridis from Kandalaksha Bay of the White Sea (Russia). One of the authors, however, clarified that it was a mistake in the manuscript and that only M. arctia was collected and identified in that study (Udalov, A.A., in litt. 3 Apr 2019).
Distribution worldwide. Atlantic coast of North America: from Nova Scotia (Canada) and Maine (USA) south to Delaware (USA). North Europe: Northern Ireland, North Sea, Baltic Sea (Figs 2, 3A).