Bradophila minuta, 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 : 6-7

Bradophila minuta sp. nov.

Type material: Holotype ovigerous ♀ from Diplocirrus glaucus (Malmgren, 1867) , Finnmark, Stn 657-1 (70.8933°N, 25.54°E), depth 93 m, 18 September 2003; collected by A. Sikorski; NHMUK Reg. No. 2015.2991. 1 ovigerous paratype ♀ from D. glaucus , 4315 Valhall Norflanken, Stn 14-3 (56.323°N, 03.349012°E), depth 66 m, 30 May 2008; collected by A. Sikorski; NHMUK Reg. No. 2015.2992. 1 ovigerous paratype ♀ from D. glaucus, Oseberg Øst, Stn 5-5 (60.6968°N, 02.9406°E), depth 154 m, 25 May 2004; collected by A. Sikorski; NHMUK Reg. No. 2015.2993. 1 paratype ♀ from D. glaucus , FFH 3958, Stn B 1-B (65.9101°N, 12.22313°E), depth 72 m, 23 March 2007; collected by A. Sikorski; NHMUK Reg. No. 2015.2994. 1 ovigerous paratype ♀ from D. glaucus , 7165 Sjøtroll C, Stn Ra 3-2 (60.58243°N, 05.177083°E), depth 203 m, 0 4 September 2014; collected by A. Sikorski; NHMUK Reg. No. 2016.513. 3 ovigerous paratype ♀♀ from 3 specimens of D. glaucus , 8854 Søprvika, Stn C 3 (68° 28.262’N 15° 13.159’E), depth 150 m, 26 April 2017; collected by A. Sikorski, NHMUK Reg. No. 2017.167-169.

Additional non-type material: 1♀ from unidentified polychaete fragment, Oseberg Øst, Stn 9-2 (60.69733°N, 02.929333°E), depth 153 m, 17 May 1997 ; collected by A. Sikorski. 1 ovigerous ♀ in oral cavity of D. glaucus , Western Isles, Loch Seaforth, Maaruig , SEPA Stn Ref. 8 (57 o 57.532’N, 0 6 o 43.343’W), depth 19 m, 23 August 2001 . 1 ovigerous ♀ in oral cavity of D. glaucus , Northumberland, CEFAS End 6/04, Stn 91 (55° 3.690’N, 01° 21.883’W), depth 32 m, 0 3 June 2004 . 1♀ ovigerous, protruding from prostomial region of D. glaucus , Northumberland, Blyth , ENTEC, 2010, collected by P. R. Garwood. 1 ovigerous ♀ in oral cavity of D. glaucus , BEN14-0186 ( APEM 55898 ), Irish Sea (53° 48.947’N, 05° 05.814’W), 24 November 2014 . 1 ovigerous ♀ in oral cavity of D. glaucus, Sound of Jura , 10 km East of the Small Isles, SEPA Stn SJ 1 (55 o 50.507’N, 0 5 o 46.829’W) depth 174 m, 18 May 2016 . NHMUK Reg. No. 2018.110-111 .

Differential diagnosis. Adult female body highly transformed, lacking any external trace of segmentation, consisting of dorsoventrally flattened ectosoma connected to endosoma by broad stalk passing through host’s body wall ( Fig. 1A ). Ectosoma about 1.28 times wider than long (range 1.16 to 1.39 times); mean width 248 µm, range 230 to 264 µm (based on 3 specimens); mean length 192 µm, range 180 to 209 µm. Dorsal surface flat, marked with faint longitudinal cuticular ridges in all specimens ( Fig. 1B, C ); ventral surface smooth ( Fig. 1D ) but protruding posteroventrally to form wedge-shaped transverse expansion ( Fig. 1C ). Genital apertures paired, carried on highly sclerotized genital swellings at posterolateral angles of ectosoma ( Fig. 1E ). Median copulatory pore located on midline between genital apertures (arrowed in Fig. 1E ): copulatory duct extending anteriorly, opening into paired seminal receptacles. No vestiges of paired appendages present; caudal rami absent; anus lacking. Egg sacs paired, up to 1.49 mm long and 0.38 mm wide; multiseriate, with maximum of only 3 or 4 longitudinal series of eggs visible from any one aspect ( Fig. 1A ). Stalk broad, about 60 to 65 µm in diameter; originating at anterior end of ectosoma. Endosoma slender, flattened, and about 2 mm long with more-or-less parallel margins ( Fig. 1A ).

Male unknown.

Etymology. The name of the new species, minuta , alludes to its small body size.

Remarks. The ectosoma of the new species has a slightly different shape from the type species B. pygmaea . The ectosoma is dorsoventrally flattened with a wedge-shaped posteroventral protrusion, while in B. pygmaea it was described as globular and slightly flattened by Marchenkov (2002). The globular ectosoma of B. pygmaea has a diameter in the range of about 0.33 to 0.7 mm according to Levinsen (1878) and Marchenkov (2002), whereas the ectosoma of B. minuta sp. nov. is distinctly wider than long, and its maximum width of 0.23 to 0.26 mm falls outside the range reported for B. pygmaea . The paired genital apertures of B. pygmaea were described as relatively inconspicuous by Marchenkov (2002), whereas those of B. minuta sp. nov. are prominent ( Fig. 1E ). Another obvious difference between the new species and B. pygmaea is the form of the egg sacs: in B. pygmaea the egg sacs are very broad in the middle and taper strongly towards each end, and they contain numerous eggs in a multiseriate arrangement with about 7 or 8 complete rows visible in the middle section of each sac, from any view ( Levinsen 1878). In contrast, in the new species the egg sacs are cylindrical, maintaining a more or less constant diameter along most of their length, and only 3 to 4 rows of eggs are visible from any view ( Fig. 1B ). The differences in size and shape of the ectosoma, in the prominence of the genital apertures, and in the arrangement of eggs within the egg sacs support the establishment of a new species, B. minuta .

The form of the endosoma of adult female B. pygmaea was poorly documented by Levinsen (1878). Marchenkov (2002) described his females as having an elongate endosoma with a tuberculate surface, although he stated that the endosoma was variable in form. The endosoma of the new species is elongate, flattened and lies in the host’s coelom around the outside of the gut, as described by Marchenkov (2002). We found the endosoma difficult to observe and not easy to delimit from the surrounding host tissues.

The only known host of B. pygmaea is the flabelligerid Brada villosa . The new species utilizes a different flabelligerid, Diplocirrus glaucus , as host, and the adult female copepods are usually embedded in the tip of the proboscis of the host. The female copepod is normally mostly concealed within the oral cavity of the host with only the tip of the ectosoma or the ovisacs protruding out of the oral aperture. The known depth range of the new species is 19 to 203 m.

Figures

FIGURE 1. Bradophila minuta sp. nov. A, habitus of embedded adult female, dorsal view showing elongate flattened endosoma; B, ectosoma and basal part of endosoma of ovigerous female, ventral; C, ectosoma and base of endosoma of female, posterior; D, ectosoma of female, dorsal; E, ectosoma of female, ventral view showing outline of seminal receptacles, and median copulatory pore (arrowed). Scale bars: A, 0.5 mm, B–D, 200 µm, E, 100 µm.