(Figs. 15 A–K; 17 F)
Zatsepinia rittichae Jirkov, 1986: 289 –290, 1 fig.—Jirkov 2008: 120, tab. 1 Specimens examined. Off Kushiro, Hokkaido, 42 ° 34.99 'N, 144 ° 48.02 'E – 42 ° 34.68 'N, 144 ° 49.91 'E, 1028–1075 m, KT-07- 29, St. K- 1, 11.2007 (2 cs, 3 af); SMF 21696, 42° 27.63 'N, 144 ° 57.44 'E – 42 ° 27.57 'N, 144 ° 59.38 'E, 2025– 2037 m, KT-07- 29, St. K- 3, 11.2007 (6 cs, 5 af). Off Cape Erimo, Hokkaido, 41 °43.00'N, 143 ° 56.37 'E – 41 ° 44.53 'N, 143 ° 56.46 'E, 1008–1031 m, KT-07- 29, St. E- 1, 11.2007 (7 af). Off Hachinohe, 40 °00.00'N, 143 ° 31.37 'E – 41 °00.76'N, 143 ° 30.25 'E, 2032–2055 m, KT-07- 29, St. H- 2, 11.2007 (3 cs, 1 af). Sagami Bay, 35 °09.2'N, 139 ° 22.4 'E – 35 °09.7'N, 139 ° 22.2 'E, 500–520 m, KT- 66 - 12, St. 2, 6.1966 (1 cs); 35 °04.1'N, 139 ° 31.5 'E – 35 °04.2'N, 139 ° 32.1 'E, 750–870 m, KT- 76 - 3, St. BS 4, 3.1976 (3 cs). Shimoda, 34 °41.0'N, 139 °01.1'E – 34 ° 40.7 'N, 139 °00.6'E, 102 – 92 m, St. 12, 11.1981 (6 cs, 2 af). North of Tokunoshima Island, 28 °03.79'N, 128 ° 56.31 'E – 28 °04.71'N, 128 ° 57.59 'E, 533–583 m, KH-05- 1, St. OT- 10, 5.2005 (1 af).
Additional material examined. Holotype: Zoological Museum of Moscow State University, Pol. 301, N Atlantic, off northern Norway, Stn. 11, 71° 10 ’N, 17 °00’E, Transect 105, 354 – 357 m, R/V Tunets, Sigsbee Trawl, 21.07. 1978, leg. & det. Jirkov.
Description. Length 12–16 mm, width 0.8–1 mm. Prostomium simple, without glandular ridges or eyes (Fig. 15 A). Buccal tentacles broad, smooth, with deep ventral groove (Fig. 15 A, B, C). Segment II dorsally reduced or overgrown by segment III (Fig. 15 A, B). Two pairs of cirriform branchiae in a transverse line at anterior end of segment III (Fig. 15 A); branchial groups separated by small median gap (Fig. 15 A); branchiae of segment II in innermost position, branchiae of segment III in outermost position (Fig. 17 F). Chaetae in segments II and III absent. Notopodia with limbate capillary notochaetae from segment IV, present in 12 segments. Notopodia in second-to-last thoracic unciniger elevated, connected by dorsal ridge (Fig. 15 D, E); notochaetae of modified segment with broad wings and hirsute tips (Fig. 15 F, G). Neuropodial tori with uncini from segment VI, present in 10 thoracic uncinigers. Cirri and papillae in thoracic parapodia absent. Continuous ventral shields distinct to thoracic unciniger 8 or 9, faint to abdominal unciniger 1 or 2. Four intermediate uncinigers. 15 abdominal uncinigers. Rudimentary notopodia and glandular pads in intermediate and abdominal uncinigers absent. Pinnules with dorsal papilla (Fig. 15 H). Pygidium with terminal anus surrounded by ring of short papillae (Fig. 15 I). Thoracic uncini with 1 small and 1 large tooth in 1 median row over 2 lateral rows with 2 teeth each, above rostral tooth and basal prow (Fig. 15 J, K). Abdominal uncini with crest of numerous teeth above rostral tooth and basal prow.
Remarks. Three of the examined specimens collected in November 2007 are filled with eggs. The abdominal unciniger count of 15 is slightly higher than in the holotype (13). The tentacles, of which only the tips are visible in the holotype, seem to be smooth, in contrast to Jirkov’s description as “pinnate (?)”, and the uncini are in agreement with our specimens.
We consider the difference in the number of abdominal uncinigers an intraspecific variation.
Distribution. Barents Sea and Norwegian Sea (Jirkov 1986). Newly recorded along the Japanese Pacific coast from off Kushiro, Hokkaido, in the north, to Sagami Bay, central Honshu, in the south, and off the coast of Tokumoshima Island in the East China Sea, in 100–2055 m.