Pectinaria okudai ( Imajima & Hartman, 1964 )

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 : 441-443

Pectinaria okudai ( Imajima & Hartman, 1964)

[Japanese name: Okuda-umi-isagomushi] ( Figs 8–9 )

Pectinaria (Cistenides) sp.: Okuda (1938, 128).

Cistenides okudai Imajima & Hartman, 1964: 328 .

Pectinaria okudai: Kitamori (1965:46) .— Nishi et al. (2012, 142).

Material examined. IzRO-Pol-001-005, Shinjiko Lake, brackish water, 1–2 m, sandy mud, coll. D. Kataoka, deposited in Izumo Office of River, Chugoku Regional Development Bureau, Ministry of Land, Infrastructure and Transport, Japan.

CBM-ZW 1053, Nakatsu Tidal Flat, Suo-Nada, Seto Inland Sea ( Fig. 1), 33.6047636884N, 131.2378156185E, July 2012, intertidal muddy bottom, collected by hand, coll. E. Nishi. AM W 45877, Shinjiko Lake, and Nakaumi Lake, Shimane, muddy bottom, July 2012.

Description. Based on 5 individuals of IRO-001-005. Body length 10–22 mm including scaphe, width 5 mm at cephalic region, 2 mm at tail. Crown (operculum) with 13–16 paleae on each side. Paleae tapering to pointed tip. Tips with rough teeth on inner side, recurved. Cephalic membrane (cephalic veil) with 10–15 papillae. Raised cephalic rim without marginal papillae.

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. 8 A). Second segment without posterodorsal lobe ( Fig. 8 A).

Comb-like branchiae present on segments III–IV, each consisting of a series of loose, flat lamellae ( Fig. 8 A). Glandular median plate (ventral shield) on segments III–V ( Fig. 8 A). Dorsal chaetigers 16 pairs (on segments V–XX), each bearing two kinds of bristles; one bordered with serrations along anterior portion, recurved dorsally, other stout, straight, tapering to acute tip ( Figs 8 F, G, 9A, B). Uncinigerous tori 12 pairs (on segments VIII–XIX), segment XX (= 16th chaetiger) with lateral lobe without uncini; uncini with 7–9 major teeth in lateral view, arranged in 3–4 irregular rows, with over 30 minute (minor) teeth ( Figs 8 H, J, 9D). Scaphe ovoidal, flattened dorsally, broadly divided into 6 lobes on each lateral margin ( Fig. 8 A, D). Free end of scaphe with spatulate valve. Scaphal hooks 12–13 pairs, straight with slightly curved tip ( Figs 8 E, 9C). Tube made of sand, ca. 30 mm in length, tube opening 2.0–3.0 mm in width, posterior aperture 1.5–2.0 mm wide.

Taxonomic remarks. This species was first described from the Ise Sea (= currently Ise Bay) by Okuda (1938) and later redescribed by Imajima and Hartman (1964) as Cistenides okudai , new name. Kitamori (1965) recorded the same species with a note on uncini, as a species of Pectinaria . Recently the species was recorded in Shinjiko and Nakaumi Lakes and Seto Inland Sea ( Nishi et al. 2012, 2013). The genera Cistenides and Pectinaria are distinguishable by the number of rows of large teeth in the uncini, the former has a single row of large teeth, the latter has two or three (or four) rows of large teeth. Based on scanning electron microscope observations, Pectinaria okudai (= Cistenides sp. sensu Okuda 1938) has 3–4 rows of teeth ( Fig. 9 D; Nishi et al. (2012) and thus it had moved to the Pectinaria from Cistenides ( Nishi et al. 2012) . Hutchings & Peart (2002) showed the diagnosis of Pectinaria as “Neurochaetal uncini with major teeth arranged in two rows” (p. 110). Then we have changed the generic character to “uncini with 2 or 3 (or more) rows of teeth” (see above diagnosis of the genus) because some Pectinaria have 3 or more rows of large teeth in uncini.

Pectinaria okudai is differentiated from other species in the genus by the number of uncinigerous tori and uncini shape.

Figures

FIGURE 8. Pectinaria okudai (partly revised after Nishi et al. 2012; Fig. 2). Body, hooks, chaetae and uncinus of IzRO-Pol- 0 0 1 (A – E) and IzRO-Pol- 002 (E – J). (A) Whole animal, ventral view. (B) Ventral view of head and anterior segments. (C) Dorsal view of anterior end. (D) Scaphe and posterior-most segments. (E) Hooks. (F – G) Chaetae. (H – J) Uncini (drawn from scanning electron microscope images). Scale bars 1 mm (A – D); 10 µm (E); 50 µm (F); 5 µm (G, H, J).

FIGURE 9. Pectinaria okudai. Scanning electron microscope images of IzRO-Pol- 002. (A) Thorax chaetae. (B) Tip of chaeta. (C) Hooks. (D) Uncini. Scale bars 50 µm (A); 10 µm (C); and 5 µm (B, D).