Anomopsyllus geminus, 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 : 48

Anomopsyllus geminus n. sp.

Type material: Holotype ♀ (dissected and mounted on a glass slide) from Ampharete cf. lindstroemi ; Sandnessjøen, Lille Åsvaer (66.235ºN, 12.3374ºE), depth 45 m; Stn LA 2-B, 2007; BMNH Reg. No. 2012.1396.

Paratype ♀ (dissected and mounted on glass slide) attached to abdomen of Ampharete lindstroemi ; northern North Sea , Stn BYA03a F2 (59 o 30.49’N, 01 o 29.16’E.), depth 112 m, collected by P. Garwood, 24 August 2006; BMNH Reg. No. 2012.1397 .

Female (holotype). Body ( Fig. 27A ) consisting of cephalosome, inflated trunk, and small urosome. Body length 1.21 mm, excluding caudal setae. Cephalosome subcircular, 200×250 µm, with short anterodorsal ridge and transparent membranous flange along frontal margin. Trunk flattened, 850×539 µm, with slightly undulating, convex lateral margins and truncate posterior margin. Urosome ( Fig. 27B ) consisting of genital complex and 1- segmented abdomen. Genital complex 110×215 µm, much wider than long, with large dorsal hump ( Fig. 27A ); genital apertures located ventrolaterally ( Fig. 27B ). Abdomen much narrower than genital complex, indistinctly articulated from genital complex, and 92×96 µm. Caudal ramus 48×23 µm (ratio 2.09:1), with 6 setae, midterminal seta much larger than other 5, 135 µm long.

Rostrum absent. Antennule ( Fig. 27C ) 123 µm long and indistinctly 5-segmented, with armature formula 6, 3, 2, 2+aesthetasc, and 7+aesthetasc; first segment slightly produced in middle of anterior margin. Antenna ( Fig. 27D ) 3-segmented; first segment unarmed; second segment with 1 medial seta; third segment 29×12 µm, with 3 medial and 5 distal setae, one distinctly smaller than other 4.

Labrum ( Fig. 27E ) with concave posterior margin and stout posteromedian process. Mandible ( Fig. 27F ) with 2 hook-like distal processes and 1 proximal seta representing palp. Maxillule ( Fig. 27G ) lobate, with 3 thick distal setae (1 medial and 2 outer). Maxilla ( Fig. 27H ) 2-segmented; both segments unarmed but distal segment with spinulose pad on expanded distal surface. Maxilliped ( Fig. 27I ) 4-segmented, with armature formula 0, 2, 0, and 2; first and second segments with ornamentation of fine spinules on surface; third segment with membranous flange near outer distal corner; fourth segment reflexed, with blunt tip bearing spinulose pad.

Legs 1–3 ( Fig. 27J–L ) vestigial, each represented by small, spinulose lobe tipped by 2 setae. Legs 4 and 5 absent. Leg 6 probably represented by 1 small seta and 2 spinules in genital area ( Fig. 27B ).

Female (paratype). Body length 1.26 mm, excluding caudal rami (caudal rami detached). Body shape as in holotype. Cephalosome without anterodorsal ridge, otherwise same as that of holotype. Trunk and urosome as in holotype.

Antennule, antenna, labrum, mandible, maxillule, maxilla, and maxilliped also as in holotype in shape, segmentation and setation.

Legs 1–3 better developed than those of holotype. Leg 1 ( Fig. 27M ) with 1 outer seta on protopod and 3 setae on 1-segmented exopod; endopod absent. Leg 2 ( Fig. 27N ) similar to leg 1, but exopod small, with 2 setae. Leg 3 ( Fig. 27O ) lobate, with 3 setae.

Legs 4 and 5 absent as in holotype.

Male. Unknown.

Etymology. The specific name geminus , from the Latin meaning “double”, alludes to legs 1–3 each of which has only two setae.

Remarks. Anomopsyllus geminus n. sp. differs from its three congeners in having lobate legs 1–3, each bearing 2–3 setae or 1 outer seta plus 2 or 3 setae on 1-segmented exopod, the blunt terminal segment of the maxilliped, and three setae on the maxillule. None of these features has been reported in any congeners. In contrast to the legs, the antennule, antenna and maxilliped are consistent in morphology between the two observed specimens. Therefore, these cephalic appendages may be more reliable than the legs for discriminating taxonomically between species in the genus Anomopsyllus .

The holotype was attached to the surface of setiger 14 of the host, with its head end directed towards the posterior end of the worm. The paratype was attached at setiger 16 on the abdomen of its host, the same polychaete species, and was orientated with its head towards the anterior of the worm.

Figures

FIGURE 27. Anomopsyllus geminus n. sp., holotype female. A, habitus, dorsal; B, urosome, ventral; C, antennule; D, antenna; E, labrum; F, mandible; G, maxillule; H, maxilla; I, maxilliped; J, leg 1; K, leg 2; L, leg 3. Paratype female, M–O, legs 1–3. Scale bars: A, 0.2 mm; B, 0.05 mm; C–O, 0.02 mm.