Terebellides guangdongensis Zhang & Hutchings 2018
- Dataset
- Taxonomy and distribution of Terebellides (Polychaeta: Trichobranchidae) in the northern South China Sea, with description of three new species
- Rank
- SPECIES
- Published in
- Zhang, Jinghuai, Hutchings, Pat (2018): Taxonomy and distribution of Terebellides (Polychaeta: Trichobranchidae) in the northern South China Sea, with description of three new species. Zootaxa 4377 (3): 387-411, DOI: 10.11646/zootaxa.4377.3.4
Classification
- kingdom
- Animalia
- phylum
- Annelida
- class
- Polychaeta
- order
- Terebellida
- family
- Trichobranchidae
- genus
- Terebellides
- species
- Terebellides guangdongensis
description
Description (Based on both holotype and paratypes). Holotype complete, 29.3 mm in length and 0.3 – 2.6 mm in width (from posterior end to anterior chaetigers (excluding chaetae) respectively), with distinct demarcation between thorax and abdomen; with 39 abdominal segments; body tapering posteriorly with segments. Dorsum and ventrum smooth, colour pale to reddish in preserved specimens. Buccal tentacles of two types on dorsal margin of large tentacular membrane, uniformly tapered and with expanded tips (Figs 2 A – B & 3 A – B, H). Prostomium compact almost completely hidden by tentacular membrane. Eyespots absent. Peristomium consisting of expanded lower lip which forms an elongate rectangular structure and upper lip often covered by lower lip and tentacular membrane (Figs 2 A – B & 3 A – B). Segments 1 – 2 with small lateral lappets and inconspicuous ventral collar (Figs 2 A – B; 3 B – C & 5 A – C). Segments 3 – 7 with distinct lateral lappets, largest on segment 4; forming thickened ventral membranous collars (ventral lobes) on anterior margins of segments 3 – 7, lobes progressively shorter from segment 4 onwards; ventral lobes of segment 3 with undulating margins in the middle, others with smooth margins (Figs 2 A – B; 3 A – B & 5 A – B). Thoracic chaetiger 2 (segment 4) with a nephridial papilla at base of notopodia (Figs 3 B – C & 5 C). Segment 2 with a dorsal lobe anterior to branchial stem (Figs 3 B – C & 5 C). Lateral lappets without projections (Figs 2 A; 3 B & 5 C). Ventral glandular bands and glandular areas around parapodia absent. Branchia as single elongate structure dorsally on segments 2 – 4, consisting of two pairs of posterior lobes (BL 1 – 2 on the outside and BL 3 – 4 in the middle) and pair of anterior lobes, lobes composed of tightly packed lamellae (Figs 2 C; 3 D & 5 B). Anterior lobes (BL 5 – 6) fused completely, and very short about 1 / 12 posterior lobes. Posterior lobes fused for about 3 / 5 their length. BL 1 – 2 as long as BL 3 – 4. BL 1 – 2 and BL 5 – 6 with large lamellae, broad almost 3 times more than BL 3 – 4; lamella of BL 1 – 2 and BL 3 – 4 with longitudinal ridges; outer edges of lamellae with a row of small rounded papilla; inside edges of lamellae smooth; without cilia (Fig. 3 D – G); BL 3 – 4 with small lamellae, without distal tip. Thorax with 20 segments without dorsal hump. Notopodia 18 pairs, present on segments 3 – 20 (chaetigers 1 – 18). First two pairs smaller and inserted more dorsally to subsequent ones; first one markedly reduced with shorter and finer chaetae, notochaetae appearing to arise from body wall (Figs 2 A; 3 A – C; 4 A – B & 5 C). Chaetae arranged in 2 tiers, lower tier with finely pointed chaetae and upper tier with narrowly – winged chaetae; chaetae of lower tier finer and about 1 / 2 length of those upper tier (Figs 2 G – H & 4 A – B, E – G). Neuropodia beginning from segment 8 (chaetiger 6), and present on all subsequent segments. Thoracic neuropodia as sessile pinnules. First neuropodia with geniculate acicular hooks (holotype right 6 and left 7); geniculate hooks arranged in single row throughout with pointed tips and weakly bent, and gradually decreasing in size from dorsal to ventral; the smaller geniculate hooks being sharply bent (Figs 2 E & 4 C – D). Subsequent thoracic neuropodia with one row or partial double rows of 23 – 25 long-handled uncini per torus; uncini with main fang and several rows of secondary teeth, with 3 – 4 large teeth in the first row (Figs 2 F & 4 H – I). Abdomen with 39 segments with length gradually decreasing posteriorly. Abdominal neuropodia as foliaceous pinnules with about 30 avicular uncini; arranged in single row (Fig. 4 J). Abdominal uncini with strongly crested head, covered with numerous small and scale-like teeth (Figs 2 I & 4 K – L). Pygidium blunt without appendages (Figs 2 D & 5 E). The methyl green staining similar to pattern 1 of Schüller & Hutchings (2010), compact green colour on the first five segments, then developing into striped pattern (Fig. 5 A, D). Margin of lower lip with white stripe on peristomium. Thoracic stripes gradually fade from segment 6, and disappearing by about segment 15. Green bands present on lateral thorax and abdominal ventrum. Additionally, staining on thoracic notopodia, base of posterior abdominal neuropodia and ventrum of tips of posterior branchial lobes. Lamellae of branchial lobes without staining. Variability. Complete individuals ranging from 2.3 – 29.2 mm in length, 0.2 – 2.6 mm in width of anterior chaetigers excluding the chaetae and 18 – 40 abdominal segments. The large specimens with greater width and more abdominal segments than smaller ones (Fig. 6 A). The length ratio of thorax and abdomen (LRTA) ranging from 1.2 – 6.2, showing large specimens possibly with a smaller LRTA and relatively long abdomen (Fig. 6 B). Geniculate hooks ranging from 5 – 7 in number, with numbers appearing to increase with body size. Thoracic neuropodia with less than 15 (smaller specimens) to 25 uncini per torus on larger specimens, suggesting that the number increases with size of individual and presumably age.
discussion
Remarks. Terebellides guangdongensis n. sp. is characterised by the following morphological characters: one branchia has two pairs of posterior lobes and pair of anterior lobes not distinctly prolonged; all branchial lobes have densely packed lamellae; BL 1 – 2 are as long as BL 3 – 4, and broader than BL 3 – 4; thoracic chaetigers of which the first five have lateral lappets, without conspicuous projections; first notopodia are strongly reduced, and have shorter and finer chaetae compared to subsequent ones; only chaetiger 6 has geniculate hooks.
distribution
Distribution. Known only from Shantou waters, Guangdong of the northern South China Sea (Fig. 1). Habitat. Found in muddy substrates in shallow water (7.5 – 40 m depths).
etymology
Etymology. The specific name guangdongensis is derived from guang dong, latinized Chinese characters for the locality, which refers to the type locality in the Guangdong Province waters.
materials_examined
Material examined. Holotype. MBM 286009 in IOCAS, Guangdong, Nanao Island, South China Sea, 23.4982 ° N 117.2546 ° E, 15.0 m, mud, Sep 2015. Paratypes. MBM 286010 (2 specimens), MBM 286024 (1 specimen mounted for SEM) in IOCAS: Guangdong, Nanao Island, South China Sea, 23.4982 ° N 117.2546 ° E, 15.0 m, mud, Sep 2015; MBM 286011 (3 specimens) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.6078 ° N 114.7286 ° E, 12.0 m, mud sand, Sep 2013; MBM 286012 (2 specimens), MBM 286021 (4 specimens) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.5764 ° N 114.6839 ° E, 17.0 m, mud, Jun 2015; MBM 286013 (1 specimen), MBM 286015 (1 specimen) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.7158 ° N 114.6644 ° E, 9.0 m, mud, Jun 2015; MBM 286014 (1 specimen) in IOCAS: Zhanjiang, Guangdong, Beibu Gulf, South China Sea, 20.4099 ° N 109.7840 ° E, 17.5 m, mud, May 2016; MBM 286016 (4 specimens) in IOCAS: Maoming, Guangdong, the coast of Yuexi, South China Sea, 21.2500 ° N 111.1500 ° E, 19.0 m, mud, Jun 2016; MBM 286017 (1 specimen) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.6083 ° N 114.7289 ° E, 7.5 m, silt, Jun 2015; MBM 286018 (5 specimens) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.6675 ° N 114.6642 ° E, 10 m, silt, Aug 2016; MBM 286019 (1 specimen) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.7050 ° N 114.7217 ° E, 9.0 m, mud, Aug 2016; MBM 286020 (1 specimen) in IOCAS: Shanwei, Guangdong, the coast of Yuedong, South China Sea, 22.2888 ° N 115.1530 ° E, 40.0 m, mud, Aug 2015; MBM 286022 (2 specimens) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.6247 ° N 114.6719 ° E, 14 m, mud, Jun 2015; MBM 286023 (1 specimen) in IOCAS, P 20161225001 (2 specimens) in SCSEM: Guangdong, Daya Bay, South China Sea, 22.5750 ° N 114.5186 ° E, 14 m, mud, Jun 2015; MBM 286025 (1 specimen) in IOCAS: Guangdong, Daya Bay, South China Sea, 22.6672 ° N 114.6639 ° E, 10.5 m, silt, Jun 2015.