Amphictene japonica ( Nilsson, 1928 )

Nishi, Eijiroh, Matsuo, Kanako, Kazama-Wakabayashi, Maki, Mori, Atsushi, Tomioka, Shinri, Kajihara, Hiroshi, Hamaguchi, Masami, Kajihara, Naoto & Hutchings, Pat, 2014, Partial revision of Japanese Pectinariidae (Annelida: Polychaeta), including redescriptions of poorly known species, Zootaxa 3895 (3), pp. 433-445 : 435

Amphictene japonica ( Nilsson, 1928)

[new Japanese name: Nihon-umi-isagomushi] ( Figs 2–3 )

Pectinaria (Amphictene) japonica Nilsson, 1928: 52 .

Amphictene japonica: Okuda (1934, 321) ; Imajima & Hartman (1964, 327).

Material examined. CBM-ZW 497, 1 specimen, Incheon, Songdo, North Korea, 26 August, 1987. ZIHU Shiro Okuda’s Collection, “ Pectinaria japonica ”, 6 specimens (3 complete, 3 separated into two or three parts), 1932, Choshi, Chiba Prefecture (see Fig. 1), coll. Mr. K. Ose.

Description. Body length 55.0 mm including scaphe, width 5.0 mm at cephalic region. Crown (operculum) with 12 paleae on each side. Paleae stout, flattened golden bristles, tapering to curved pointed tip ( Fig. 3 A–C). Cephalic membrane (cephalic veil) damaged and poorly preserved. Raised cephalic rim with 26 marginal papillae ( Fig. 3 B, C).

First pair of tentacular cirri arise from posterolateral margin of segment I. Second pair of tentacular cirri present on segment II, arise from a connecting ridge ( Fig. 3 B). Segment II with small posterodorsal ear-lobe (lappet) on base of tentacular cirri ( Fig. 3 B). Venter of segments III–IV slightly glandular and smooth. First chaetiger (segment V) with an anteroventral lobe and a small ear-lobe situated on ventral side of chaetal tuft ( Fig. 3 A, B). Second chaetiger (segment VI) with anteroventral lobe, anterior margin nearly smooth ( Fig. 3 B).

Comb-like branchiae present on segments III–IV, each consisting of a series of loose, flat lamellae ( Fig. 3 A, B). Large subquadrate glandular flaps (lobes) present ventrally at base of second pair of branchiae on segment IV ( Fig. 3 A, B). Glandular median plate (ventral shield) on segments III–IV ( Fig. 3 A). Dorsal chaetigers 16 pairs (on segments V–XX), each bearing two kinds of bristles; one bordered with serrations along anterior portion, recurved dorsally, the other chaetae stout, straight, tapering to very acute tip. Uncinigerous tori 13 pairs (on segments VIII–XX); uncini with 8 major teeth in lateral view, 6–7 minute teeth ( Fig. 3 E). Scaphe ovoidal, flattened dorsally, broadly divided into 2–3 lobes on each lateral margin by shallow notches, each lobe with small cirriform papillae ( Fig. 3 D). Free end of scaphe with spatulate valve. Scaphal hooks 21–22 pairs, straight and slightly bending near tip. Tube not retained with specimen.

Taxonomic remarks. Amphictene japonica specimens of Shiro Okuda’s collection have been dried and subsequently placed in ethanol and are thus poorly preserved and in a poor condition ( Fig. 2 B). According to the label ( Fig. 2 A), Okuda’s description is based on those six specimens (1934: p. 323–324).

Amphictene japonica can be distinguished from other Japanese pectinariid species by the cephalic rim having marginal papillae and by presence of a large number of scaphal hooks (usually more than 20 pairs).

Figures

FIGURE 2. Amphictene japonica. Label of Shiro Okuda’s collection and preserved specimens. (A) Label of the collection “ Pectinaria japonica 1932 Choshi, Chiba pref. by Ose ” A locality name “ Choshi ” in Japanese (in Chinese character). (B) Three individuals in the collection. Scale bar 10 mm.

FIGURE 3. Amphictene japonica. Body and chaeta (uncinus) of CBM-ZW 497. (A – C) Anterior body, ventral, lateral and dorsal side view. (D) Scaphe and posterior-most part. E. uncinus drawn from scanning electron microscope image. Scale bars 1 mm (A – D); 10 µm (E).