Anomopsyllus bifurcus, 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 : 46

Anomopsyllus bifurcus n. sp.

Type material: Holotype ♀ (dissected and mounted on a glass slide) from Notomastus latericeus ; Brattholmen, FFH 3958, Stn B 3 (65.928ºN, 12.2518ºE), depth 105 m, 23 March 2007; BMNH Reg. No. 2012.1395.

Female. Body ( Fig. 26A ) dorso-ventrally flattened and consisting of cephalosome, trunk and urosome. Body length 1.77 mm, excluding caudal rami. Cephalosome ( Fig. 26B ) subcircular, 250×331 µm, with transparent membranous flange along frontal margin. Trunk flattened, trapezoidal, 1.35× 0.68 mm, gradually broadening posteriorly, with truncated posterior margin and no trace of segmentation. Urosome ( Fig. 26C ) small and consisting of genital complex and 1-segmented abdomen. Genital complex strongly tapering in dorsal view, 288 µm wide and wider than long. Abdomen inserted on ventral surface of genital complex ( Fig. 26C ), with deep posteromedian anal cleft. Caudal rami not observed (detached).

Rostrum absent. Antennule ( Fig. 26D ) 197 µm long and 6-segmented; armature formula 1+spine, 6, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; spine on first segment large; second segment with transverse sclerotization near proximal one-third. Antenna 3-segmented, with 0, 1, and 8 (3 middle and 5 distal) setae on first to third segments, respectively; all setae simple and naked; first segment with 2 transverse rows of minute spinules.

Labrum not observed (lost during dissection). Mandible ( Fig. 26F ) with 3 claw-like blades (2 terminal and 1 subdistal) and 1 proximal seta possibly representing palp. Maxillule ( Fig. 26G ) lobate, with 4 distal setae. Maxilla ( Fig. 26H ) 2-segmented; proximal segment unarmed; distal segment with 1 proximal seta and spinulose pad on expanded distal surface. Maxilliped ( Fig. 26I ) 4-segmented; armature formula 0, 2, 0, and 1; first and second segments with numerous minute spinules over surface; terminal segment reflexed, with 2 blunt terminal processes covered apically with fine spinules, broader outer process with trace of articulation at base.

Leg 1 ( Fig. 26J ) represented by small lobe tipped by 2 setae and 1 nearby seta. Legs 2 and 3 ( Fig. 26K, L ) vestigial, each formed by small lobe tipped by 1 seta and 1 nearby (protopodal) seta. Legs 4 and 5 absent. Leg 6 probably represented by 1 seta and 2 small spinules in genital area ( Fig. 26C ).

Male. Unknown.

Etymology. The specific name bifurcus alludes to the distally bifurcate terminal segment of the maxilliped.

Remarks. The most characteristic features of Anomopsyllus bifurcus n. sp. are: the distally blunt, bifurcate terminal segment of the maxilliped, the large spine on the first segment of the antennule, the reduced legs 1–3, each of which is represented by two or three setae, and the absence of legs 4 and 5. The female body of A. pranizoides Sars, 1921 in the illustration of Sars (1921) is almost identical in form to that of A. bifurcus n. sp. However, both A. pranizoides and A. abyssorum Laubier, 1988 share a similar kind of maxilliped in which the terminal segments bears two claw-like processes and two setae, as illustrated by Laubier (1988). This arrangement differs markedly from the blunt terminal processes of the new species. Neither A. pranizoides nor A. abyssorum has a strong spinform setal element on the first antennulary segment.

This is the first nereicolid to be reported from a host belonging to the family Capitellidae .

Figures

FIGURE 26. Anomopsyllus bifurcus n. sp., female. A, habitus, dorsal; B, cephalothorax, dorsal; C, urosome, ventral; D, antennule; E, antenna; F, mandible; G, maxillule; H, maxilla; I, maxilliped; J, leg 1; K, leg 2; L, leg 3. Scale bars: A, 0.2 mm; B, C, 0.1 mm; D–L, 0.02 mm.