Sigambra hanaokai ( Kitamori 1960 )

Nishi, Eijiroh, Tanaka, Katsuhiko, Fujioka, Yoshimi & Sato, Masanori, 2007, Reinstatement of Sigambra hanaokai (Kitamori, 1960) (Polychaeta, Pilargidae), with an overview of the literature on the genus, Zootaxa 1653, pp. 57-68 : 59-64

Sigambra hanaokai ( Kitamori 1960) reinstated

(Japanese name: Hanaoka Kagi-gokai) Figs 1–2

Ancistrosyllis hanokai Kitamori, 1960:1086 –1088, Fig. 1 A–H.

Sigambra tentaculata: Tamai, 1987 (non Treadwell 1941).

Sigambra phuketensis: Imajima, 2001:186 , Fig. 89; Imajima, 2006:351 (non Licher & Westheide 1997).

Material examined. Seto Inland Sea. NHM-2007.590 Nishinomijima, Hiroshima Bay, 20 m, grab sampler, 25 May 1998, coll. M. Tsujino. SAMA E3667, Nishinomijima, Hiroshima Bay, 20 m, 8 September 1998 coll. M. Tsujino. ZMUC-Pol-1891, Nishinomijima, Hiroshima Bay, 20 m, 8 September 1998, coll. M. Tsujino. KMNH- IvR 500, 203, Kure Bay, Seto Inland Sea, 20 m, by grab sampler, 17 June 1998, by M. Tsujino. BPBM-R 3041, Nishinomijima, Hiroshima Bay, Stn. 6-1, 20 m, 25 May 1998, coll. M. Tsujino. Tokyo Bay. Yatsu tidal flat, intertidal mud bottoms, ASIZW 0000711, Sta. 5, 11 September 2006, coll. T. Furota. MV, F146152, Sta. 11, 2 individuals, 11 September 2006 coll. T. Furota. Shinhamako estuary, mud flat, intertidal, NHM-2007.526. 5 May 1996, coll. E. Nishi. Edogawa-housuiro estuary, mud bottom, SMF 16861, Sta. 3-4, 12 August 2003, coll. E. Nishi. Off Haneda, mouth of Tamagawa River, mud flat: MV, F146153 (3 individuals), Sta. 21- 16, 31 May – 5 June 2006. USNM 1106217, Sta. L4a, 35°32′4.2″N, 139°47′15.0″ E, 8 August 2006. USNM 1106218, Sta. L5f, 35°32′4.2″ N, 139°46′47.4″ E, 8 August 2006. SMF 16862, Sta. L3b, 35°31′51.6″ N, 139°47′24.6″ E, 4 August 2006. SMF 16863, Sta. L3a, 35°31′57.6″ N, 139°47′28.8″ E, 6 August 2006. SMF 16864, Sta. L5b, 35°32′15.6″ N, 139°46′54.0″ E, 6 August 2006. NHM-2007.530-552, August 2006. BPBM-R 3042, Sta. L-31-18b, 31 May – 5 June, 2006. ZMUC-POL-1889, Sta. L3e, 35°31′40.2″ N, 139°47′18.6″ E, 8 August 2006. ZMUC-POL-1890, Sta. L4b, 35°32′0.6″ N, 139°47′10.8″ E, 3 August 2006. ZIHU-3257, Sta. L3d, 35°31′43.8″ N, 139°47′20.4″ E, 5 August 2006. ZIHU-3258, Sta. L4d, 35°31′51.6″ N, 139°47′7.2″ E, 3 August 2006. ZIHU-3259, Sta. L3, 35°31′48.0″ N, 139°47′22.8″ E, 5 August 2006. Sanbamze tidal flat, Ichikawa and Funabashi, on mud bottoms, NHM-632-633, Sta. 3, 2 individuals, 8 May 2005, by hand, coll. E. Nishi 2007. SMRC-POL-4, east of Sanbamze, Sta.3, 26 May 2005, coll. T. Furota. MBM 119720, Sta. 3, 18 May 2003, by hand, coll. T. Furota. MBM 119721, Sta. 5, 18 May 2003, by hand, coll. T. Furota. Nekozanegawa River, subtidal mud bottoms, NHM-2007,634-641, Nekozanegawa River, Sta. 5, 8 July 2003, by grab sampler, coll. E. Nishi. SAMA E3668, Nekozanegawa River, Sta. 8, 8 July 2003, by grab sampler, coll. E. Nishi. off Kasai, mud flat, CBM-ZW- 1002, 8 June 2007, coll. M. Taru. off Yokohama, NHM-2007.594-597, 4 individuals, Sta. 12, 10– 20 m, mud bottom, 25 May 2006, coll. H. Mizuo. ZMUC-POL-1892, Sta. 10, 10– 20 m, mud bottom, 25 May 2006, coll. E. Nishi. ZMUC-POL-1893, Umi-no-koen, Yokohama, intertidal sandy shore, 6 April 2007, coll. E. Nishi. CMNH-ZW01747, Umi-nokoen, Yokohama, intertidal sandy shore, 6 April, 2007 coll. E. Nishi. AMNH-Annelida 5429 Umino-Koen, sandy shore, Kanazawa, Yokohama, intertidal sandy beach with small stones, 35¡20′8.5″ N(= 35.335696 N), 139°38′5.25″ E (= 139.634793 E), on 28 August 2007, coll. E. Nishi. Obitsugawa River estuary, Chiba, mud bottoms, NHM-2007.642, Sta. N1-1, 22 May 2005 coll. T. Furota. NHM-2007.643, Sta. T-4, 22 May 2005 coll. T. Furota. SMF 16858, Sta. C-2-2, 22 May 2005 coll. E. Nishi. SMF 16859, Sta. K-1-2, 22 May 2005, coll. E. Nishi. SMF 16860, Sta. H-1-2, 22 May 2005 coll. E. Nishi. Sagami Bay. Odawa Bay, Miura Peninsula (eastern part of Sagami Bay) USNM 1106216, seagrass beds, 5–10 m, by grab sampler, Sta. OD-4, 10 individuals, 23 May 2002, coll. T. Kudo. NHM - 2007.609-631, seagrass bed, mud bottom, May and October, 2001, coll. T. Kudo. ECOSUR - PILA 0 0 0 8, seagrass beds, 5–10m, by grab sampler, St. OD- 4, 12 October, 2001, by T. Kudo. NHM-2007.598-599, Zaimokuza coast, intertidal sandy shore, 2 individuals, May 2003, coll. E. Nishi. Nagaragawa River and Ibigawa River. NHM-2007.591–593. Nagaragawa River estuary, mud bottom, Sta. 4KC-5 (NHM-2007.591–593), Sta. 2KC-4 (NHM-2007.593), 26–28 October 2005, by grab sampler, coll. K. Yamauchi. SAMA E3669–3671, Nagaragawa River and Ibigawa River estuary, mud bottom, Sta. 3KC-4 ( SAMA E3669), Sta. 4KC-4 (E3670), Sta. 35KC-2 (E3671), 26–28 October 2005, by grab sampler, coll. K. Yamauchi. Mikawa Bay. KMNH-IvR500202, Sta.2, 34°48.224′ N, 137°17.420' E, 29 June 2006, coll. A. Mori. NHM-2007.528, Sta.1, 34°48.158′ N, 137°16.709' E, 13 April 2006, coll. A. Mori. NHM-2007.529, Sta.2, 34°48.224′ N, 137°17.420' E, 13 April 2003, coll. A Mori. OMNH-Iv5020, Sta.1, 34°48.158′ N, 137°16.709' E, 29 June 2006, coll. A. Mori. OMNH-Iv5021, Sta. 5, 34°47.806′N, 137°17.226' E, 29 June 2006, coll. A Mori. CBM-ZW-999, Sta. 4, 34°47.829′ N, 137°17.685' E, 29 June 2006, coll.A Mori. CBM- ZW-1000, Sta. 5, 34°47.806′ N, 137°17.226' E, 13 April 2006, coll. A Mori. CMNH-ZW-01734, 1735, 01737- 1746, Stas. 1–9, June to December 2006, coll. A. Mori. Hakata Bay, Kyushu. Imazu tidal flat, muddy bottoms. RBCM 007-00014-001, Stas. 1–2, June 2005, coll. K. Mori. RBCM 007-00015-001, Sta.1.5, June 2005, coll. K. Mori. KMNH IvR 500, 204, Sta. 6-1, East of Hakata Bay, 23 May 2007, coll. M. Yamada. KMNH IvR 500, 205, Sta. DILU 4, 3-6 June 2004, coll. K. Mori. KMNH IvR 500, 206, Sta. DM23, 3–6 June 2004, coll. K. Mori. KMNH IvR 500, 207, Sta.DMI3, 3-6 June 2004, coll. K. Mori. KMNH IvR 500, 208, Sta. DILU 1, 8–9 June 2005, coll. K. Mori.

Comparative material. – Sigambra phuketensis Licher & Westheide, 1997 . Paratype. ZMUC-867, 3 specimens (1 complete and 2 anterior ends), Patang Bay, Phuket Island, Thailand, 20 m, coll. Nateewatha & Hylleberg, 18 June 1982. Non-type material of S. phuketensis : Thailand Mangrove swamps of Samut Songkhram (ca. 90 km west of Bangkok), estuarine muddy bottom, coll. Y. Fujioka, June 2004 (CMNH- ZW01736). Samut Songkhram, Mangrove estuary, intertidal mud flat, coll. Y. Fujioka, June 2003.( ASIZW 0000712, ASIZW 0000712: ECOSUR-PILA 0 0 0 9, NHM-2007.527, SMF 16857, USNM 1106219).

Redescription. Body dorsoventrally flattened, tapering posteriorly, 5–15 mm long, 0.5–1.0 mm width without parapodia, 0.5–1.2 mm with parapodia ( Figs. 1 A,B, 2C). Color in ethanol light brown, slightly whitish or yellowish. Prostomium trapezoidal, rounded, wider than long. Palps biarticulate, palpostyles digitate. Antennae slender; lateral ones short, median antennae long, ca. 0.5 mm length, reaching chaetigers 7–8. Eyes lacking. Pharynx unarmed, without jaws, with 14 subequal, rounded, marginal papillae ( Figs. 1 C, 2C); five upper papillae thinner, alternating in size, four laterals (two per side larger), lower papillae intermediate in thickness, of about the same length. Four to six subdistal papillae on both lateral side of everted pharynx ( Fig. 2 E). No tooth-like or any other papillae type on proboscis, even under scanning electron microscope observation. Peristomium with a dorsolateral transverse line of closely arrayed papillae, present in following few chaetigers (only visible with SEM) ( Fig. 2 E, F). Two pairs of slender peristomial cirri ( Fig. 1 B).

Parapodia biramous ( Fig. 1 D, E), notopodia of middle segments each with conical dorsal cirri, and with a light-coloured acicula; from chaetigers 4–5 or 6–8, to the last chaetiger, all notopodia have a dorsal hook ( Fig. 1 B), usually accompanied by a single, long capillary chaeta (lacking in most anterior and posterior notopodia). Dorsal surface of notopodia smooth, except for a row of 7–10 conspicuous stalk-like papillae over the anterior and posterior sides; each papilla resembles the peristomial ones ( Fig. 2 E, F). Dorsal cirri of chaetiger 1 long, slender; second dorsal cirri much shorter than following ones ( Fig. 1 B).

Neuropodial lobe cylindrical with a single acicula. Chaetae include 10 to ca. 40 neurochaetae of different types; supra-acicular long, slender capillaries ( Fig. 1 H), slightly serrated ( Figs. 1 I, 2I); subacicular short, straight denticulate chaetae ( Fig. 1 J), and short, slightly bent pectinates ( Fig.1 K, 2J). Ventral cirri more slen- der than dorsal cirri. Chaetiger 2 without ventral cirri.

Pygidium rounded, with two slender anal cirri ( Fig. 1 F).

Variations. The posterior body segments are frequently lost during collection; Tamai (1987) used the width of the first chaetiger as a proxy for body size, and found that the maximum width was 0.9 mm, the maximum wet weight 10.3 mg, and the maximum body length was 23 mm with up to 90 chaetigers. The start of dorsal hooks is in chaetigers 4–5 (asymmetrical) in some specimens, and 3–9 in all specimens examined; it was regarded as starting in chaetigers 4–11 ( Tamai 1987). The length of median antennae is 0.4–0.5 mm, and its size is not related to body width, at least in the specimens examined ( Fig. 3 ).

Remarks. As shown in Fig. 2 , Sigambra hanaokai has small papillae as in S. bassi ( Hartman 1947) . This character is only observable with SEM, and this feature might be present in other species as well, as already reported for S. tentaculata and S. parva ( Moreira & Parapar 2002) . The Thailand specimens of S. phuketensis Licher and Westheide (1997) also have similar papillae on the peristomium and parapodia (Sato and Nishi, personal observation). Moreira and Parapar (2002) reported that S. tentaculata and S. parva have tooth-like papillae on the proboscis. Except for some subdistal proboscidal papillae ( Fig. 2 E), we could not find similar characters in Japanese and South Asian specimens, even with scanning electron microscope observations. However, peristomial and parapodial papillae and tooth-like proboscidial papillae might be found in other species after close observation on a scanning electron microscope and with observation of stained materials.

In comparing S. hanaokai to S. phuketensis paratypes and recently collected specimens, the greatest morphological similarities were the head, parapodia, and chaetae. They differed slightly in size, with S. phuketensis being generally smaller (3–8 mm in S. phuketensis , 5–15 mm in S. hanaokai ). The type materials of S. phuketensis were smaller (4.0– 5.5 mm), and S. hanaokai larger (length 30–80 mm, max. 9.5 mm for Tokyo Bay specimens, max. 150 mm for Hakata Bay specimens). The body size varied among collection date and reproductive season, thus general body size should not be used as a taxonomic index in two morphologically similar species, although size might be useful for distinguishing among other species of the genus. Sigambra hanaokai and S. phuketensis closely resemble S. tentaculata , but the former two taxa differ by having pectinate neurochaetae. Licher and Westheide (1997) noted that S. phuketensis is smaller than 10 mm and S. tentaculata is large, exceeding 20 mm in body length, but the body length of S. hanaokai (= S. phuketensis sensu Imajima (2001) or S. tentaculata sensu Tamai (1987) is even larger than in their review, as noted in Tamai (1987) and this study.

The most obvious difference between S. hanaokai and S. phuketensis is the relative length of the median antennae: in S. hanaokai it is long, reaching chaetigers 4–8, often chaetiger 10, but in S. phuketensis the median antennae is short (usually up to 0.4 mm), barely reaching chaetigers 1–2 ( Fig. 3 ). The relative length of the median antenna compared with the lateral antennae might be a useful character for distinguishing related taxa (Table 1).

By studying Japanese specimens, Tamai (1987) showed that S. hanaokai could be separated into two groups: one having the dorsal hooks starting on chaetiger 4, and a second in which the dorsal hooks start on chaetigers 7 or 8. However, the first chaetiger with a hook varies even within the same population, as in the case of Hiroshima Bay and Kure Bay; the Seto Inland Sea population includes both groups ( Tamai 1987), and this character varies there as well. Thus, in this situation, the first chaetiger provided with hooks does not have a distinctive taxonomic value.

Figures

FIGURE 1. Sigambra hanaokai (Kitamori 1960). A. Hakata Bay specimen (KMNH IvR 500, 206) in dorsal view. B. Hiroshima Bay specimen (NHM- 2007.590), dorsal view of head and anterior part. C. Same, ventral view of anterior end. D. Hakata Bay specimen, anterior parapodium in posterior view. E. Hakata Bay specimen, last parapodium in posterior view. F. Hiroshima Bay specimen (NHM- 2007.590), ventral view of pygidium. G. Hakata Bay specimen, dorsal hook. H. Same, simple capillary chaeta. I. Same, long serrated chaeta. J. Same, short serrated chaeta. K. Same, pectinate chaeta.

FIGURE 2. Sigambra hanaokai (Kitamori 1960). Tokyo Bay specimen (A, B, photos taken by M. Taru) and Hakata Bay specimen (C – J, scanning electron micrographs). A. whole view of live worm. B. close-up view of anterior end, showing eggs in central dorsal parts. C. anterior end in frontal view showing the everted pharynx. D. anterior end (ma: median antennae, arrow shows hook). E. anterior end showing rows of peristomial papillae (arrow) and subdistal papillae in everted pharynx (pp with arrow). F. close-up of peristomial papillae. G. anterior parapodial papillae. H. dorsal hook of middle chaetiger. I. chaetiger of middle part. J. close-up of pectinate chaetae and short serrated chaetae on middle chaetiger.

FIGURE 3. Median antenna length and body size (width) in Sigambra hanaokai and S. phuketensis. Data for S. phuketensis include paratypes and recently collected specimens, data for S. hanaokai Sagami Bay is a sample from Kamakura and Odawa. The figure shows the clear difference of median antennae length relative to the body size (body width in anterior chaetiger) in two closely similar species.