Herpyllobius cluthensis, Boxshall & O’Reilly & Sikorski & Summerfield, 2019

Boxshall, Geoff A., O’Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, Zootaxa 4579 (1), pp. 1-69 : 14-16

Herpyllobius cluthensis sp. nov.

Syn: Herpyllobius polynoes: Chambers & Muir, 1997 (fig. 34)

Type material: Holotype ovigerous ♀ from Malmgrenia andreapolis McIntosh, 1874 , Kingstone Hudds , Firth of Forth (55° 34.75’N, 02° 55.923’E), depth 40 m, 11 October 1991; collected by Lee Heaney ( SEPA); NHMUK Reg. No. 2017.498 . Paratype ovigerous ♀ from Malmgrenia sp., Loch Linnhe , Ardgour , Gorsten Fish Farm, Stn 4-2, depth unknown, 0 7 July 2004 ; collected by P.R. Garwood, NHMUK Reg. No. 2017.499. 2 paratype ♀♀ (1 ovigerous) on single host M. andreapolis, Firth of Clyde , Irvine Bay, Stn H (55° 35.9’N, 04° 47.40’E), depth 38 m, 19 April 2005 ; collected by M. O’Reilly ( SEPA); NHMUK Reg. No. 2017.500 .

Additional Material examined: 1 ovigerous ♀ on Malmgrenia andreapolis, Firth of Clyde , Irvine Bay, SEPA Stn Z, (55 o 34.75’N, 0 4 o 45.20’W), depth 40 m, 12 October 1979 , figured in Chambers & Muir (1997) as H. polynoes , collection date of September 1981 cited in O’Reilly et al. (2011) is erroneous. 1♀ on M. andreapolis, St. Abbs Sludge Disposal Grounds, Stn 13 (56° 04.50’N, 02° 07.25’W), depth 58 m, 0 2 June 1986. 2 ovigerous ♀♀ on single M. andreapolis , north Irish Sea , Block 112, (54 o 38’N 0 4 o 04’E), January 1998 ?, collected by Sue Hamilton (specimen since lost). 1 ♀ ovigerous on M. andreapolis, Firth of Clyde , Irvine Bay, SEPA Stn Z, (55 o 34.75’N, 0 4 o 45.20’W), depth 40 m, 19 April 2001 . 1 ovigerous ♀, on M. andreapolis Solway Firth , CSEMP Stn 25 (54 o 44.97’N, 0 4 o 00.22’W) depth 17.7 m, 0 4 November 2007 . 1♀ on Malmgrenia arenicolae , APEM Sample # 8460, Mourne Coast , EHS Stn ANA_B, (54° 44.12’N, 05° 55.04’W), depth 19 m, 0 7 August 2013 . 1 ovigerous ♀ on Malmgrenia sp., Western Isles , Isle of Harris, Meavaig Fish Farm, collected by P.R. Garwood, 2014? 1 ovigerous ♀ on M. arenicolae, Loch Nevis, collected by J. Hunter, 2015. NHMUK Reg. Nos 2018.122–127 .

Differential diagnosis. Ectosoma of adult female dorsoventrally flattened, with slightly concave undersurface ( Fig. 5A ), about 1.16 times wider than length along midline in dorsal view ( Fig. 5B ). Greatest width just posterior to middle of ectosoma ( Fig. 5B ). Mean ectosoma length 0.96 mm (based on 5 ovigerous specimens), range 0.77 to 1.10 mm, mean maximum width 1.11 mm, range 0.94 to 1.33 mm. Genital swellings located posteroventrally ( Fig. 5D ), moderately sclerotized, about 415 µm high by 360 µm wide. Stalk short, broad, originating anteroventrally at extreme anterior end of ectosoma. Endosoma ( Fig. 5A, C ) about 3.2 mm long, comprising long flattened proximal part terminating in flattened expanded apex, about twice width of proximal part; flattened apical part curved around gut of host. Egg sacs ( Fig. 5A ) multiseriate, up to 1.87 mm long (typically about as long as ectosoma). Male not found but fragments of last copepodid exuviae attached near mid posterior margin of female ectosoma (arrowed in Fig. 5B ).

Etymology. The name of the new species refers to the locality, the Firth of Clyde, where the first specimen was found in 1979; it is a combination of clutha, which is the old name for the River Clyde, and ensis meaning from.

Remarks. The new species can be distinguished from its congeners in European waters by the shape of the ectosoma and by the extraordinary development of the flattened endosoma. The ectosoma is dorsoventrally flattened and slightly concave on the undersurface, and the stalk originates anteroventrally. It differs from H. arcticus which has a more globular ectosoma with the stalk originating on the underside, just anterior to genital swellings. The endosoma of H. cluthensis sp. nov. is elongate and flattened whereas that of H. arcticus is an irregular 3-dimensional mass produced into processes of varying size. In addition, the new species attaches to the head of its host whereas H. arcticus typically attaches to the side of the host in the anterior to middle part of the body ( Lützen 1964a; present account).

Herpyllobius polynoes typically attaches to the head of its host ( Lützen 1964a; present account) and the new species was also found attached to the head of its host. This shared attachment site has led to confusion between the two species. The specimen illustrated by Chambers & Muir (1997, fig. 34) as H. polynoes attached to Malmgrenia andreapolis , belongs to the new species, and is based on a sketch by M. O’Reilly of the first specimen found from Irvine Bay in 1979. Similarly we consider that the specimen from western Ireland figured by Gotto & O’Connor (1980) as H. polynoes from Malmgrenia lunulata (Delle Chiaje, 1830) probably belongs to the new species described here. O’Reilly (2011) had already reported on additional material of this copepod and commented that it may represent a new species. The two species can be readily distinguished: the ectosoma of the new species is wider than long, dorsoventrally flattened and the stalk originates anteroventrally, whereas in H. polynoes it is about 1.5 times longer than wide, strongly convex dorsally and the stalk originates in the posterior half. Both species have an elongate flattened endosoma but in H. cluthensis sp. nov. it has a flattened apical expansion, while in H. polynoes the endosoma tapers towards the apex.

Additional material of this species was found on Malmgrenia andreapolis , M. arenicolae (Saint-Joseph, 1888) , and on unidentified Malmgrenia sp. Several other species of Malmgrenia occur in European seas, including newly described species ( Barnich et al. 2017). It seems likely that H. cluthensis sp. nov. may occur on some of these. To date, its known distribution includes the Firth of Clyde, Firth of Forth, Solway Firth, Loch Nevis, Loch Linnhe, the Western Isles, the northern Irish Sea, the North Sea off St. Abbs, and possibly off western Ireland.

Figures

FIGURE 5. Herpyllbius cluthensis sp. nov. female. A, habitus of holotype female showing small ectosoma (viewed obliquely and appearing foreshortened) bearing paired egg sacs and bipartite endosoma comprising long proximal part and expanded apical part, with small ring of host tissue at penetration site; B, ectosoma of paratype female, dorsal view showing fragments of copepodid exuviae attached near posterior margin (arrowed); C, expanded apical part of endosoma of paratype female; D, paired genital apertures, ventral view. Scale bars: A, 1 mm, B–D, 0.5 mm.