Herpyllobius cordiformis Lützen, 1964

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 : 16-18

Herpyllobius cordiformis Lützen, 1964

Syn: Herpyllobius affinis: Stephensen, 1936

Material examined: 5 ovigerous ♀♀ from Eunoe cf. oerstedi, COPOL 1 (78° 57.3’N, 03° 34.8’E), depth 242 m, 0 2 October 2007; collected by A. Sikorski; NHMUK Reg. Nos 2015.2962-2965.

Differential diagnosis. Ectosoma of adult female subrectangular ( Fig. 6D ), tapering slightly anteriorly, in dorsal view, about 1.22 times longer than maximum width. Mean ectosoma length 2.56 mm (based on 5 specimens), range 2.40 to 2.76 mm, mean maximum width 2.10 mm, range 1.80 to 2.28 mm. Posterior end wider than anterior and bearing conspicuous median posterior lobe about 300 µm in diameter (arrowed in Fig. 6C, D ) on posterior margin, located on midline between and just dorsal to paired genital openings. Genital swellings prominent ( Fig. 6D ), heavily sclerotized, about 640 µm high by 425 µm wide. Stalk short, broad, originating on underside of ectosoma almost beneath genital apertures. Endosoma forming irregular mass with numerous small, flattened lobate processes around margins. Egg sacs ( Fig. 6C ) elongate, slightly curved, multiseriate, up to 5.46 mm long (twice as long as ectosoma).

Remarks. Three of the females in this sample were already detached from the host but two were still attached to parapodia with the lobate endosoma extending towards the body of the host. These are large parasites: the new material is up to 2.76 mm in ectosomal length with slightly curved egg sacs up to 5.46 mm long. However, this is smaller than the material described by Lützen (1964a). The female from Cape Elisabeth in Maine, figured by Lützen (1964a, fig. 13), was 3.5 mm long with egg sacs about 4.1 mm long, but he also reported a female from “a giant specimen” of Eunoe nodosa which was 4.5 mm long and had egg sacs up to 12 mm in length. This species appears somewhat variable in size, perhaps dependent in part upon host species. Despite this difference in body size, the material from Eunoe cf. oerstedi is identified as H. cordiformis due to the possession of the conspicuous rounded median posterior lobe located just dorsal to the genital apertures, a unique feature among Herpyllobius species, combined with the extreme posterior location of the stalk, which originates almost beneath the genital apertures ( Fig. 6C ).

This species was originally described based on material from the Atlantic coast of Maine ( USA) on the host Nychia cerosa (probably Gattyana cirrhosa , according to Lützen (1964a)) and from Greenland on Eunoe nodosa ( Lützen 1964b) . In addition, the material from Inglefield Bay, Greenland, identified by Stephensen (1936) as Herpyllobius affinis Hansen, 1887 , was considered to belong to H. cordiformis by Lützen (1964a). This is the first record from European waters and, at 78°N, is located well into the Arctic Circle.

Figures

FIGURE 6. Herpyllobius polynoes (Krøyer, 1864). A, habitus of ovigerous female, posterior view with swelling in midline arrowed; B, ectosoma, lateral. Herpyllobius cordiformis Lützen, 1964. C, habitus of ovigerous female, lateral view with median posterior lobe arrowed; D, ectosoma of female, dorsal. All scale bars 1 mm.