Lagis bocki ( Hessle, 1917 )

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 : 437

Lagis bocki ( Hessle, 1917)

[Japanese name: Umi-isagomushi] ( Figs 4–5 )

Material examined. CBM-ZW 1069, Yokohama, St. 5, mouth of Tsurumi River, Tokyo Bay, 15 m, 35.47423140N, 139.688587E, September 2009, grab sampler, coll. E. Nishi. AM W 45878, Yokohama, Tokyo Bay, September 2009, grab sampler, coll. E. Nishi. CBM-ZW 1047 & CBM-ZW 1048, Haneda, Tokyo Bay, Stn. L2e (L31), 35.52299881N, 139.7961121E, May 2012, sandy mud, 13 m, grab sampler. CBM-ZW 1049, Haneda, Tokyo Bay, Stn. A44b (L11b), 35.57106781N, 139.7833405E, May 2012, sandy mud, grab sampler. CBM-ZW 1050, Haneda, Tokyo Bay, Stn. L21-5, 35.53341675N, 139.7982635E, May 2012, sandy mud, 5 m, grab sampler. CBM-ZW 1051, Haneda, Tokyo Bay, Stn. L21-3, 35.53188324N, 139.7942047E, May 2012, sandy mud, 3 m, grab sampler. YNU- M Iv.—uncatalogued, four specimens, Nakatsu tidal flat, St. A, Okunigawa river mouth, June 2014, intertidal mud bottom, collected by hand. ZIHU Shiro Okuda’s Collection, ZIHU-3858, “ Pectinaria ”, Misaki, 16 April, 1933, 2 dried specimens.

Description. Based on the 6 specimens deposited in CBM. Body length 10–15 mm including scaphe, width 3.0–5.0 mm at cephalic region. Crown (operculum) with 10–12 paleae on each side. Paleae stout, flattened golden bristles, tapering to pointed tip, tip curved ventrally and coiled ( Fig. 4 A, B). Cephalic membrane (cephalic veil) semicircular in shape, bearing 23–26 fimbriae on its free margin ( Fig. 4 B). Cephalic membrane continuous with dorsal semicircular area of cephalic rim, and first tentacular cirri situated between them ( Fig. 4 B). Raised cephalic rim without marginal papillae ( Fig. 4 A).

First pair of tentacular cirri arise from posterolateral margin of segment I ( Fig. 4 B). Second pair of tentacular cirri present on segment II, arise from connecting ridge ( Fig. 4 A). Comb-like branchiae present on segments III–IV, each consisting of series of loose, flat lamellae ( Fig. 4 A, B). Small lobe situated on dorsal side of first pair of branchia ( Fig. 4 A). Glandular median plate (ventral shield) on segments III–VI ( Fig. 4 B). Dorsal chaetigers 15 pairs (on segments V–XIX), each bearing two kinds of bristles; one bordered with serrations along the anterior portion, recurved dorsally, the other chaetae stout, straight, tapering to an acute tip. Uncinigerous tori 12 pairs (on segments VIII–XIX); uncini 7–8 major teeth in lateral view, 6–7 minute (minor) teeth ( Fig. 5 C). Scaphe ovoidal, flattened dorsally, broadly divided into 6–7 lobes on each lateral margin by shallow notches ( Fig. 4 C). Free end of scaphe with spatulate valve, fringed with 18–24 fimbriae with finger-shaped dorsal anal cirrus ( Fig. 4 D). Scaphal hooks 3–4 pairs, straight and bending slightly towards tip ( Figs 4 E, 5B). Tube cone-shaped, composed of minute particles of sand and fragments of shells.

Taxonomic remarks. Okuda (1936: p. 326) noted the occurrence of this species from Misaki, Miura Peninsula. Okuda’s collection and ZIHU 3858 are the ones noted by Okuda (1936), based on the label.

In Asian region, Lagis crenulatus Sun & Qiu, 2012 , L. koreni and Lagis abranchiata ( Fauvel, 1932) have been recorded ( Uschakov 1955; Sun & Qiu 2012). The Japanese species, Lagis bocki can be distinguished from L. crenulatus and L. abranchiata by having thoracic branchiae, whereas the latter two species lack them. Further, the Japanese species has long fringes in the margins of the anal flap, whereas in other species these margins are smooth.

Kitamori (1965) described a subspecies, Lagis bocki naikaiensis , from Hiroshima, Seto Inland Sea. The subspecies was separated from the stem species, L. bocki , by having 10–16 fimbriae on the cephalic membrane (veil) instead of 23–28 in L. bocki , and by having 2–3 pairs of scaphal falcate hooks instead of 4 as in L. bocki . This subspecies is considered invalid as these two characters are highly variable as demonstrated by Sun & Qiu (2012) for L. crenulatus , who examined a range of material from various localities. Our material, CBM-ZW 1069 collected at Yokohama, has 24 fimbriae on the cephalic veil and 3 pairs of hooks, representing a mixture of characters assigned to L. bocki naikaiensis and L. bocki sensu stricto, confirming that these characters are variable within L. bocki sensu stricto thus supporting the rejection of the subspecies.

Figures

FIGURE 4. Lagis bocki. Body of CBM-ZW 1069. (A) Lateral view of head and anterior part. (B) Entire animal, latero-ventral view. (C – D) Scaphe. (E) Posterior part of scaphe. Scale bars (A – E) 1 mm.

FIGURE 5. Lagis bocki. Scanning electron microscope images of chaetae, hook and uncini of CBM-ZW 1050. (A) Chaetae of chaetiger 2. (B) Hooks. (C) Middle abdomen uncini. Scale bars 10 µm (A); 20 µm (B); 5 µm (C).