Anomopsyllus hamiltonae, Kim & Sikorski & O’Reilly & Boxshall, 2013

Kim, Il-Hoi, Sikorski, Andrey, O’Reilly, Myles & Boxshall, Geoff A., 2013, Copepods associated with polychaete worms in European seas, Zootaxa 3651 (1), pp. 1-62 : 50-52

Anomopsyllus hamiltonae n. sp.

Type material: Holotype ♀ ovigerous (intact specimen) from Mugga wahrbergi ; northern North Sea , Norwegian sector, Pan Pandora Field, Stn 13 (61 o 18.51’N, 02 o 21.33’E), depth 291 m, collected by S. Hamilton, 02 February 2011; BMNH Reg. No. 2012.1398.

Paratype ♀ (dissected on glass slide) from M. wahrbergi ; Stn S2, 02 October 2007; BMNH Reg. No. 2012.1399 .

Paratype ♀ on M. wahrbergi , northern North Sea , Norwegian sector, Pan Pandora, Stn 6 (61 o 17.48’N, 02 o 22.02’E), depth 285 m; 03 January 2011; BMNH Reg. No. 2012.1400 .

Paratype ♀ on M. wahrbergi , northern North Sea , Norwegian sector, Pan Pandora, Stn 8 (61 o 17.97’N, 02 o 21.45’E), depth 287 m; 10 January 2011; BMNH Reg. No. 2012.1401 .

Paratype ♀ ovigerous on M. wahrbergi , northern North Sea , Norwegian sector Pan Pandora, Stn.9 (61 o 17.93’N, 02 o 20.64’E), depth 285 m; 14 January 2011; BMNH Reg. No. 2012.1402 .

Paratype ♀ on M. wahrbergi , northern North Sea , Norwegian sector Pan Pandora, Stn.10 (61 o 17.86’N, 02 o 22.02’E), depth 283 m; 25 January 2011; BMNH Reg. No. 2012.1403 .

2 paratype ♀ on 2 M. wahrbergi, northern North Sea , Norwegian sector Pan Pandora, Stn.11 (61 o 18.13’N, 02 o 21.62’E), depth 289 m; 27 January 2011; BMNH Reg. No. 2012.1404-1405 .

Female. Body ( Fig. 28A ) consisting of cephalosome, inflated trunk, and small urosome. Body length 846 µm, excluding caudal setae. Cephalosome subcircular, small and indistinctly articulated from trunk, 115×138 µm, with transparent membranous flange along frontal margin. Trunk flattened, 601×323 µm, with 5 indistinct segments corresponding to first to fifth pedigerous somites divided by 4 faint suture lines and weak lateral constrictions. Urosome ( Fig. 28B ) consisting of clearly defined genital complex and 1-segmented abdomen. Genital complex 93×115 µm, with laterally expanded anterior two thirds and narrower posterior third; genital apertures located ventrolaterally ( Fig. 28B ). Abdomen 70×54 µm, distinctly longer than wide. Caudal ramus 29×16 µm (ratio 1.81:1), with convex medial margin and 5 setae, one much larger than other 4.

Rostrum absent. Antennule ( Fig. 28C ) 93 µm long and 6-segmented but articulations indistinct especially among distal 4 segments; armature formula 1, 4, 2, 2, 2+aesthetasc, and 7+aesthetasc. Antenna ( Fig. 28D ) very small, indistinctly 2-segmented, both segments similar in length; proximal segment with 1 seta; distal segment with 8 setae.

Labrum with concave posterior margin and posteromedian process ( Fig. 28E ). Mandible ( Fig. 28F ) with 2 hook-like distal processes and 1 proximal seta representing palp. Maxillule ( Fig. 28G ) lobate with 3 distal setae (1 medial and 2 outer). Maxilla ( Fig. 28H ) 2-segmented; both segments unarmed but distal segment with spinulose pad on flat distal surface. Maxilliped ( Fig. 28I ) 4-segmented, with armature formula 0, 2, 0, and 2; proximal of 2 medial setae on second segment bilaterally spinulate; third segment with membranous flange near outer distal corner; fourth segment with blunt spinulose tip.

Legs 1–5 absent. Leg 6 probably represented by 1 small seta and 2 spinules in genital area ( Fig. 28B ).

Male. Unknown.

Etymology. The specific name honours Sue Hamilton (freelance marine biologist, Edinburgh) who has found numerous parasitic copepods over many years, including most of the material of this new species, as well as many specimens of other copepod species studied in this paper.

Remarks. In possessing a distally bifurcate mandible and an unarmed but blunt terminal segment on the female maxilliped, Anomopsyllus hamiltonae n. sp. resembles A. geminus n. sp., described above. However, the small, two-segmented antenna and the absence of legs 1–5 are the characteristics that serve to separate the new species from A. geminus n. sp. and all other congeners.

Anomopsyllus hamiltonae n. sp. and other two new species of Anomopsyllus described in the present paper share a distally bifurcate mandible with a single proximal seta (although an additional, hook-like subdistal process is present in A. bifurcus n. sp.), the presence of a brim-like hyaline membrane on the frontal margin of the cephalosome, and the stout terminal segment of the maxilliped. These synapomorphic traits have not been reported in the two previously recorded congeners, A. pranizoides and A. abyssorum , although the morphology of the mandible of the latter two species is not known precisely. However, the five known species can be assigned to the genus Anomopsyllus , as they share the similar body form consisting of a small cephalosome, inflated trunk and two-segmented urosome, a four-segmented maxilliped with a stout terminal segment, the unmodified, simple setae on the two- or three segmented antenna, and the reduction or absence of swimming legs.

All the copepods in the northern North Sea in the Pan Pandora sector were attached dorsally on the host worm, near the last thoracic segment.

Genus Vectoriella Stock, 1968

Figures

FIGURE 28. Anomopsyllus hamiltonae n. sp., female. A, habitus, dorsal; B, urosome, ventral; C, antennule; D, antenna; E, mouthparts; F, mandible; G, maxillule; H, maxilla; I, maxilliped. Scale bars: A, 0.1 mm; B, I, 0.02 mm; C–H, 0.01 mm.