Terebellides baliensis Hsueh & Li, 2017, sp. nov.

Terebellides baliensis sp. nov.

Figs 4 A–G, 5A–D, 6A–D

Material examined. Holotype (NMNS 7743-4), station D13 (25°11´35˝ N 121°21´34˝E), Bali, New Taipei City, subtidal muddy bottom, 10 January 2010; paratypes (all type information the same as holotype): one specimen (NMNS7743-5), station D7 (25°13´14˝N 121°22´38˝E), 4 October 2008; one specimen (NMNS7743-6), station D9 (25°12´32˝N 121°22´38˝E), 8 April 2009; two specimens (NMNS7743-7), station B4 (25°11´48˝N 121°23´48˝E), 11 January 2010; one specimen (NMNS7743-8), station D6 (25°12´50˝N 121°22´20˝E), 11 January 2010; one specimen (NMNS7743-9), station D1 (25°12´18˝N 121°23´02˝E), 21 April 2011; one specimen (NMNS7743-10), station B3 (25°10´48˝N 121°23´15˝E), 8 August 2011; one specimen (NMNS7743-11), station D8 (25°11´36˝N 121°21´35˝E), 26 March 2012; one specimen (NMNS7743-12), station D8 (25°11´36˝N 121°21´35˝E), 6 January 2013; one specimen (NMNS7743-13), station D8 (25°11´36˝N 121°21´35˝E), 6 January 2013; three specimens (NMNS7743-14), station D8 (25°11´36˝N 121°21´35˝E), 6 January 2013; one specimen (NMNS7743-15), station D7 (25°13´14˝N 121°22´38˝E), 2 January 2014; one specimen (NMNS7743-16), station B1 (25°8´33˝N 121°20´30˝E), 9 January 2015.

Description. Holotype, complete, branchiae partially deformed; in fresh paratype (NMNS7743-10, Fig. 4 A), anterior body mostly bright yellow; preserved holotype mostly beige in alcohol (Fig. 4 B); body length 24.5 mm with 55 segments, maximum width 1.9 mm on segment 10.

Prostomium attached to dorsal surface of upper lip, basal part without eyespots; buccal tentacles of two forms, mostly simple with tapering tips, regardless of tentacle length, and others tentacles long with expanding tips (Fig. 4 C–D); peristomium forming lips, continuing dorsally; upper lip compact, low ridge; lower lip large, triangular (Fig. 4 C–D). Segment 1 conspicuous dorsally, eversible proboscis protruded, cone-shaped (Fig. 4 A–E); segment 2 to 12 with various degrees of thickened on lateral and ventral body, forming short lobes, collar-like, across ventrum covering posterior portion of preceeding segments; hump-like thickening of ventrum more marked on segment 3 to 7 (Fig. 4 C, E). Branchiae formed by single mid-dorsal stem arising between segment 2 to 4 and four-lobed (two large and two small) lamellate branchiae (Fig. 4 F); large lamellae mostly fused basally, small partly fused basally.

Notopodia as 18 pairs, on segment 3 to 20; first pair of notopodia less developed than subsequent ones (Fig. 4 C, E), second to six pairs with short notopodia, thereafter progressively longer to maximum length on segment 13, similar length on remaining notopodia (Fig. 4 B–C). First pair of notopodia with few notochaetae (Fig. 4 C, E); notopodia on segment 4 to 20 with two rows of narrowly-winged notochaetae (Fig. 4 G).

Neuropodia present from segment 8 to last segment prior to pygidium (48 pairs); neurochaetae emerging from body wall; first thoracic pair bearing geniculate hooks, about 4–7 on each side, moderate to strongly bent, with pointed tip (Fig. 5 A); subsequent thoracic neuropodia with long-handled acicular uncini (Fig. 5 B), with 5–6 rows of secondary teeth (Fig. 5 C–D); abdominal neuropodia present from segment 21, ginkgo leaf-like, bearing single row of avicular uncini on neuropodia margin, uncini short-handled with about 4 rows of secondary teeth (Fig. 5 E– F).

Genital and nephridial papillae not observed. Pygidium round (Fig. 4 B).

Variations: based on complete specimens (NMNS7743-6; 31 mm in length; NMNS7743-15, 22 mm in length). First neuropodia bearing 6–6/7–9 geniculate hooks on right and left side, respectively; tip of geniculate hooks with various degrees of bending; abdomen with 38 and 33+ segments.

Etymology. The name is derived from the name of nearby township south to the Tensui River mouth where the worm was collected.

Type locality. Offshore from Bali, New Taipei City, Taiwan.

Distribution. Known only from the type locality.

Remarks. Of currently known Terebellides, five species were described from the East Asia and one species from the Southeast Asia. They are: Terebellides brevis Imajima & Williams, 1985 (Japan), Terebellides horikoshii Imajima & Williams, 1985 (Japan), Terebellides intoshi Caullery, 1915 (Indonesia), Terebellides japonica Moore, 1903 (Japan), Terebellides kobei Hessle, 1917 (Japan), and Terebellides lineata Imajima & Williams, 1985 (Japan) (Schüller & Hutching 2013). Disregarding the presence of eversible proboscis in T. baliensis sp. nov., only T. brevis, T. japonica and T. lineata of these six species are remotely similar to the former species by having the first thoracic chaetiger distinctively less developed than subsequent ones (Imajima & Williams 1985). Moreover, T. brevis has mucronate tips on geniculate hooks and 20–25 abdominal segments (Imajima & Williams 1985: 12–13, fig. 3e), whereas T. baliensis sp. nov. has no mucronate tips on geniculate hooks (Fig. 5 A) and 35 abdominal segments. Terebellides japonica has pointed sheath covering blunt tipped geniculate hooks and an exceptionally long abdomen, with almost 2/3 the length of the animal (45–50 abdominal segments) (Imajima & Williams 1985). In contrast, T. baliensis sp. nov. has pointed tips and without sheath covering geniculate hooks and 35 abdominal segments. Terebellides lineata can be distinguished from T. baliensis sp. nov. by having four free and subequal sized branchial lobes (Imajima & Williams 1985), comparing to the presence of two large and two small basally fused branchial lobes in the latter species.