Two New and Two Poorly Known Species of Ancistrum (Ciliophora, Scuticociliatia, Thigmotrichida) Parasitizing Marine Molluscs from Chinese Coastal Waters of the Yellow Sea

The morphology and taxonomy of two new and two poorly known ciliate species of Ancistrum, found in the mantle cavity (mainly on gills) of marine molluscs from culture beds and pools along the Chinese coast of the Yellow Sea, were investigated using living observation and silver impregnation. Ancistrum haliotis n. sp. was isolated from the abalone Haliotis discus hannai Ino, A. crassum Fenchel, 1965 from the purple clam Saxidomus purpuratus (Sowerby), A. acutum n. sp. from the surf clam Mactra veneriformis Reeve, and A. japonicum Uyemura, 1937 from both the venus clam Cyclina sinensis (Gmelin) and from Dosinia japonica (Reeve). Ancistrum haliotis differs from its most similar relative A. mytili (Quennerstedt, 1867) by the body outline (anterior portion narrower vs. wider than the posterior portion), the macronuclear shape (broadly ellipsoidal vs. reniform or sausage-like), and by having fewer somatic kineties (28–32 vs. usually more than >40). Ancistrum crassum is characterized by the naked area at the apical end of the cell, the relatively short buccal field occupying about two thirds of the body length, and the posterior-dorsal cone-shaped prolongation. Ancistrum acutum n. sp. and A. japonicum are almost identical in morphometry, but differ distinctly in the live morphology (anterior end pointed and posterior end rounded vs. anterior end narrowly rounded and posterior-dorsal end protruded) and ciliary pattern (all right-side kineties extend to posterior body end vs. all right-side kineties excluding somatic kinety 1 distinctly shortened posteriad, forming a glabrous zone). We neotypify Ancistrum japonicum and discuss the taxonomic status of the four species. Based on an evaluation of all nominal species of Ancistrum and Ancistrumina, we recognize nine valid species of Ancistrum and provide a tabular guide to their identification. Fenchelia Raabe, 1970 is regarded as a junior synonym of Ancistrum Maupas, 1883. We synonymize Ancistrumina nucellae Khan, 1970 with Ancistrum japonicum Uyemura, 1937 and Ancistrum edajimanum Oishi, 1978 with A. crassum Fenchel, 1965

Alpha-Tubulin and Small Subunit rRNA Phylogenies of Peritrichs Are Congruent and Do Not Support the Clustering of Mobilids and Sessilids (Ciliophora, Oligohymenophorea)

Peritrich ciliates have been traditionally subdivided into two orders, Sessilida and Mobilida within the subclass Peritrichia. However, all the existing small subunit (SSU) rRNA phylogenetic trees showed that the sessilids and mobilids did not branch together. To shed some light on this disagreement, we tested whether or not the classic Peritrichia is a monophyletic group by assessing the reliability of the SSU rRNA phylogeny in terms of congruency with alpha-tubulin phylogeny. For this purpose, we obtained 10 partial alpha-tubulin sequences from peritrichs and built phylogenetic trees based on alpha-tubulin nucleotide and amino acid data. A phylogenetic tree from the alpha-tubulin and SSU rRNA genes in combination was also constructed and compared with that from the SSU rRNA gene using a similar species sampling. Our results show that the mobilids and sessilids are consistently separated in all trees, which reinforces the idea that the peritrichs do not constitute a monophyletic group. However, in all alpha-tubulin gene trees, the urceolariids and trichodiniids do not group together, suggested mobilids may not be a monophyletic group

Onuphis fukianensis Uschakov & Wu 1962

<i>Onuphis fukianensis</i> Uschakov & Wu, 1962 <p>Figures 1–6; Table 1</p> <p> <i>Onuphis fukianensis</i> Uschakov & Wu, 1962: 93 –94, 104, Pl. I, E–K. <i>Heptaceras fukianensis</i> (Uschakov & Wu, 1962). Paxton, 1986: 60.</p> <p> <b>Type material.</b> Neotype: MBM 283399, East China Sea, Nanji Islands, Dasha’ao, 27°28'N, 121°03'E, intertidal sandy beach, coll. Kuidong Xu, Yuhang Li, 12 August 2015. Paraneotypes: MBM283400 (n=12), same collection information as above. MBM 283034 (n=1), same locality as the neotype, 14 May 2014; MBM 283035 (n=1), East China Sea, same locality as the neotype, coll. Kuidong Xu, 8 August 2014. MBM 283080 (n=1), East China Sea, Nanji Islands, Huokun’ao, 27°28'N, 121°05'E, intertidal sandy beach, 14 August 2015.</p> <p> <b>Neotype locality.</b> Intertidal zone of Zhejiang Nanji Islands in the southwest of East China Sea (27°28'N, 121°03'E).</p> <p> <b>Diagnosis.</b> Peristomium and anterior 16–39 chaetigers each with a brown transverse band, gradually becoming narrower and lighter in color posteriorly. Ceratophores very long, with 1–5 distinct pigment spots in underside and 36–46 rings on lateral antennophores. Eyespots usually absent in adults. Branchiae starting from chaetiger 1 as single branchial filament, branched from chaetiger 43–54, with a maximum of 3–6 filaments. Subulate ventral cirri present in first five chaetiger, distinctly subulate postchaetal lobes in first 43–82 chaetigers. Interramal papillae absent. Pseudocompound hooks tridentate in adults, and mostly bidentate in juveniles (less than 2.0 mm in width), present in first four chaetigers; slender long-appendage hook absent. Subacicular hooks from chaetiger 10. Pectinate chaetae flat, distally oblique with about 11 teeth.</p> <p> <b>Description.</b> Mainly based on neotype, complemented with data from paraneotypes.</p> <p>Neotype well-preserved, 48 mm long with 81 chaetigers (without posterior end), maximum width 2.7 mm excluding parapodia (Fig. 2 B). Peristomium and anterior 4 chaetigers cylindrical, becoming dorsoventrally flattened from chaetiger 5.</p> <p>Body flesh colored in alcohol, epithelium slightly iridescent. Peristomium and anterior few chaetigers each with a wide brown transverse band situated near anterior margin; bands gradually becoming narrower and lighter in color posteriorly, disappearing by chaetiger 21 (Fig. 2). Dark pigment forming 2–4 distinct spots in underside of palpophores and antennophores (Figs 2; 3F–H). Brown patches usually occurring on anterior part of prostomium (Fig. 3 F, G), bases of frontal lips (Fig. 3 F), ceratostyles and branchiae after chaetiger 5 or 6.</p> <p>Prostomium small, subtriangular, anterior margin rounded with a pair of subulate frontal lips (Fig. 3 F, G). Palps situated on anterolateral region of prostomium, extending posteriorly to chaetiger 1 or 2 with 19–27 basal rings (Fig. 2). Antennae arranged on median part, lateral antennae reaching chaetiger 11–13 with 36–46 basal rings, median antenna reaching chaetiger 4–7 with 22–34 basal rings (Figs 2; 3H). Eyespots not observed in neotype, but present near bases of palpophores in some paraneotypes (Fig. 3 F, G). Nuchal grooves straight. Peristomium slightly shorter than chaetiger 1, possessing a pair of slender peristomial cirri inserted at anterior margin, as long as peristomium (Fig. 3 H).</p> <p>Maxillae well sclerotized, brown to dark brown. Carriers triangular, about 2/3 as long as Mx I. Maxillary formula: Mx I = 1+1, Mx II =6+7, Mx III = 7+0, Mx IV = 6+9, Mx V = 1+1. Mx V reduced to an edentate plate (Fig. 3 D). Mandibles shorter than maxillae; shafts slender, with posterior part less sclerotized; cutting plate with 3 or 4 irregular denticles in frontal edge (Fig. 3 D).</p> <p>Anterior 5–8 chaetigers longer and slightly narrower than followings. Chaetiger 1 longest, gradually decreasing posteriorly to normal length (Fig. 2). First 4 pairs of parapodia modified, directed anterolaterally, slightly larger than following. Dorsal cirri subulate, long and thick in anterior chaetigers (Fig. 4 A–F, H–L), gradually diminishing thereafter and becoming short and slender for majority of body (Fig. 4 G, M, N). Ventral cirri cirriform to subulate in first 5 chaetigers (Fig. 4 A–E, H–K), modified to glandular pads in subsequent chaetigers (Fig. 4 F, G, L–N). Postchaetal lobes distinctly subulate in first 58 chaetigers (Fig. 4 A–F, H–L), then reduced to small knobs posteriorly (Fig. 4 G, M, N). Interramal papillae absent.</p> <p>Branchiae as a single filament from chaetiger 1 to chaetiger 53, then increasing to a maximum of 3 filaments in pectinate arrangement in chaetiger 61. Branchial filaments subulate in anterior chaetigers, initially shorter than corresponding dorsal cirri (Fig. 4 A–D, H–J), becoming as long as or longer than dorsal cirri from chaetiger 5 (Fig. 4 E, F, K, L), then becoming short and digitiform in pectinate branchiae (Fig. 4 G, M, N).</p> <p> <b>Table 1.</b> Comparisons of key characters of the specimens of <i>Onuphis fukianensis</i> Uschakov & Wu, 1962. Abbreviations: <b>MBM,</b> Marine Biological Museum; <b>spec.,</b> specimen; <b>Chs,</b> number of chaetigers; <b>Lt,</b> body length; <b>L10,</b> length from the tip of prostomial lobes to posterior margin of 10th chaetiger; <b>Wm,</b> maximum width with parapodia excluded; <b>A1 rings,</b> maximum number of rings of palpophore; <b>A2 rings,</b> maximum number of rings of lateral antennophore; <b>A3 rings,</b> number of rings of median antennophore; <b>spots,</b> number of spots palps or antennae; <b>Eyes,</b> numbers of eye spots; <b>Bands,</b> chaetigers with dorsal bands; <b>VC,</b> chaetigers with subulate ventral cirri; <b>PCL,</b> chaetigers with subulate postchaetal lobes; <b>PCH,</b> chaetigers with pseudocompound hooks; <b>PCH type,</b> tooth number of pseudocompound hooks; <b>BBr start,</b> first chaetiger with branched branchiae; <b>Br max,</b> maximum number branchial filaments; <b>SH start,</b> first chaetiger with subacicular hooks.</p> <p>Chaetigers 1–4 each consisting of 2 or 3 upper limbate chaetae with very narrow wings (Fig. 5 K) and 4 or 5 tridentate pseudocompound hooks per parapodium (Fig. 4 A–D). Distal tooth large and curved, second one much shorter, proximal one smallest (Fig. 5 A–D), poorly defined or absent in juveniles (Fig. 5 E–G). Some tridentate hooks with middle and proximal teeth worn (Fig. 5 C, D) or with an extra tiny denticle between distal and middle ones (Fig. 5 C). Slender long-appendage hooks absent. Limbate chaetae from unmodified parapodia simple and slender with distinct wings on both sides (Fig. 5 J); lower limbate chaetae replaced by two hooded subacicular hooks from chaetiger 10 (Fig. 5 H). Pectinate chaetae flat and oblique with about 11 teeth, observed from chaetiger 10 with 1 or 2 per parapodium, but difficult to detect in large specimens (Fig. 5 I). Aciculae tapering with pointed tips, as many as 5 per parapodium in anterior chaetigers (Fig. 4 A–C).</p> <p>Tube membranous, cylindrical in shape, encrusted with coarse sand and grains (Fig. 3 E).</p> <p> <b>Methyl green staining pattern.</b> Based on a single paraneotype (MBM283400; Fig. 3 A–C). Prostomium slightly stained. Frontal lips deeply stained in basal portion, upper and lower lips stained evenly to light blue. Palps and antennae unstained. Peristomium and chaetiger 1 stained only on dorso-lateral areas. Dorsum and venter of anterior chaetigers each with a transverse stripe consisting of small blue dots. Branchiae of anterior 34 chaetigers deeply stained in bases to sub-distal part, gradually becoming lighter posteriorly. Dorsal cirri, postchaetal lobes, ventral cirri and ventral glandular pads lightly stained. Areas between neighbouring parapodia strongly stained, forming clear boundary with corresponding parapodia and ventral glandular pads.</p> <p> <b>Variations.</b> Maximum width ranged from 1.5 to 3.1 mm. The morphological comparison of all 16 individual specimens is provided (Table 1) and the intraspecific variability of eight selected characters is illustrated in order to determine whether these characters are size-related (Fig. 6). Specimens with a smaller body size (less than 2.0 mm in width) are herein regarded as juveniles for they have rather different characters concerning the eyespots and the pseudocompound hooks, as indicated below.</p> <p> The brown transverse bands were distinct on the peristomium and anterior few chaetigers, faded posteriorly and disappearing by chaetiger 17–40. Juveniles generally possessed 1 or 2 eyespots, which were usually absent in the adults especially in specimens more than 2.3 mm in width. Branched branchiae started from chaetiger 43–54 with a maximum number of 3–6 filaments by chaetiger 61–91. Subulate ventral cirri were usually present in the first 5 chaetigers, and in one specimen (MBM283400-spec.1) they continued to the right parapodium of chaetiger 6. The number of chaetigers with subulate postchaetal lobes varied from 43 to 82, showing no obvious relationship with the <i>Size Index</i>; this character is difficult to determine and is regarded as a poor character for <i>O. fukianensis</i>. Pseudocompound hooks were generally present in the first 4 chaetigers but also occurred in the left parapodium of chaetiger 5 in one specimen (MBM283400-spec.1). Pseudocompound hooks were tridentate in the adults, and bidentate hooks were commonly seen in the juveniles. Subacicular hooks always started from chaetiger 10.</p> <p> <b>Distribution.</b> So far, the species has been reported only from the intertidal areas of Fujian Pingtan Island (holotype) and Zhejiang Nanji Islands (neotype and paraneotypes) in the southwest of the East China Sea (Fig. 1).</p> <p> <b>Remarks.</b> The examined specimens agree well with the original description of <i>Onuphis fukianensis</i> made by Uschakov & Wu (1962) (Table 1), and both the holotype and our specimens were collected from the intertidal zone in the southwest of the East China Sea. The only difference is that the pseudocompound hooks in our material are mostly present in the first 4 chaetigers (with exception of a single specimen, on which they continue to chaetiger 5), while they occur in the first 3 chaetigers in the holotype. Since the original description of <i>O. fukianensis</i> was based on one specimen only, it is possible that it represented an anomalous individual, or was observed incorrectly. Another possibility is that the pseudocompound hooks in the fourth chaetiger of the holotype might have been broken or missing. Thus, we are convinced that the conspecificity is beyond reasonable doubt.</p> <p> <i>Onuphis fukianensis</i> is peculiar in the genus by having very long ceratophores (36–46 rings on lateral antennae) and a very late start of branched branchiae (chaetiger 43–54), which greatly exceed the normal ranges in the genus <i>Onuphis</i> (10–25 ceratophoral rings and branched branchiae from about chaetiger 20) (Paxton 1986; Arias & Paxton 2014). The specific characters give the species some similarity to members of the genus <i>Heptaceras</i> which is characterized by having long ceratophores (20–60 rings) and a mid-dorsal notch on the peristomium. Thus <i>O. fukianensis</i> was transferred to <i>Heptaceras</i> without an investigation of the holotype. However, our examination confirmed that the species has definitely no mid-dorsal notch and thus should not be placed with <i>Heptaceras</i>. Since the type material is not available and the taxonomic identity is threatened, we neotypify <i>Onuphis fukianensis</i> with our specimens collected from the same intertidal area.</p>Published as part of <i>Wu, Xuwen & Xu, Kuidong, 2017, Neotypification of Onuphis fukianensis Uschakov & Wu, 1962 and description of a new species of Onuphis (Annelida: Onuphidae) from China seas, pp. 347-360 in Zootaxa 4291 (2)</i> on pages 348-354, DOI: 10.11646/zootaxa.4291.2.7, <a href="http://zenodo.org/record/829663">http://zenodo.org/record/829663</a&gt

Phelliactis yapensis Li & Xu, 2016, n. sp.

Phelliactis yapensis n. sp. (Figs. 1, 5– 7; Tables 3, 4) Material examined. Holotype: Y 30039, grasped sponge spicules, collected on 15 December 2014 from FX-Dive 16 (137 ° 44.84 ′E, 8 ° 51.90 ′N), 855 m, foraminiferal ooze bottom. Paratypes: Y 30040, one specimen, collected together with the holotype and attached to sponges; Y 30064, one specimen, attached to sponges, collected on 18 December 2014 from FX-Dive 18 (137 °48.00′E, 8 ° 53.98 ′N), 879 m, foraminiferal ooze associated with manganese nodules. Body and Size. Individuals usually grasping or attached to sponges (Fig. 5 A, C, D). In preservation, column sub-cylindrical, height 27–104 mm (104 mm in holotype), greatest diameter of pedal disc 18–98 mm (98 mm in holotype), greatest diameter of column 22–78 mm (78 mm in holotype), greatest diameter of oral disc 11–50 mm (50 mm in holotype). Column divisible into scapus and scapulus. Scapus with thin layer of cuticle, and irregularly arranged tubercles in distal column; tubercles hemispherical, diameter of base to 6 mm. Scapulus without cuticle, but with tubercles smaller than those of scapus; tubercles of varying shapes and sizes, irregularly arranged (Fig. 5 B). Ectoderm of column very thin, mostly stripped off. Mesogloea thick, about 1.5 mm in distal column between tubercles, and about 2.5 mm in margin and proximal column of holotype. Oral disc and Tentacles. Oral disc red, bilobed and asymmetric in holotype, larger part possesses 90 tentacles and 46 pairs of mesenteries, smaller part possesses 75 tentacles and 37 pairs of mesenteries (Fig. 5 B–D). Mouth ovoid, elevated in center of oral disc, same color as oral disc. Actinopharynx well developed, length to 33 mm, occupying near 1 / 3 of column length. Tentacles marginal, smooth, tapered, with mesogloeal thickenings on aboral side (Fig. 6 A); length to 10 mm, diameter of base to 6 mm in preservation. Tentacles alternately arranged in two cycles, with inner and outer ones subequal. Number 165 in holotype (six of them cut off with margin for histological sections), 82 in paratype Y 30040, and 91 in Y 30064. Internal Anatomy. Two elongate, symmetrical siphonoglyphs; each attached to pair of directive mesenteries. Mesenteries not divisible into macrocnemes and microcnemes, arranged in five cycles (Fig. 6 D). Mesenteries more numerous at limbus than margin: holotype has 176 mesenteries at limbus, 168 at middle column, and 166 at margin; paratype Y 30040 has 128 mesenteries at limbus and 114 at margin; paratype Y 30064 has 106 mesenteries at limbus, and 96 at margin. In holotype, mesenteries of first cycle perfect and sterile; those of second cycle rarely with gametogenic tissue, and two pairs of them perfect and sterile; those of third and fourth cycles fertile, with oocytes larger than 180 Μm in diameter; those of fifth cycle incomplete, some fertile, and one excrescent pair (Fig. 6 D). Mesentery arrangement undeterminable in paratypes as their damage in course of dissection and counting number of mesenteries. Longitudinal retractor muscles diffuse, weak (Fig. 6 C). No cinclides. Acontia well developed, not coiled, usually one acontium arises from each larger mesentery proximally. Sphincter mesogloeal, alveolar, and moderately strong (Fig. 6 B). Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal (Fig. 6 A, E). Radial muscles of oral disc weaker and mesoglea thicker over endocoels than over exocoels (Fig. 6 E). Parietobasilar muscles weak (Fig. 6 C). Cnidom. Spirocysts, large basitrichs, small basitrichs, microbasic p -mastigophores (Fig. 7). See Table 3 for distribution and size. Distribution and Habitat. Phelliactis yapensis n. sp. has been found only from a seamount near the Yap Trench in the tropical Western Pacific, where the water depth ranged from 855 m to 879 m and the sediment was foraminiferal ooze sometimes associated with manganese nodules. The holotype grasped sponge spicules with pedal disc and the paratypes attached to sponges. Etymology. Named after the seamount/location (near the Yap Trench) where the species was discovered. Remarks. Phelliactis yapensis n. sp. matches well with the definition of Phelliactis Simon, 1892 in Carlgren (1949). It differs from all congeners by the combination of body size, column structure, the arrangement of mesenteries and tentacles, and the size of cnidae (Table 4). Phelliactis yapensis n. sp. possesses characteristic, very large basitrichs of mesenterial filaments (Fig. 7 J; Table 3), a basitrich type not observed in the known species of Phelliactis. Among the 20 Phelliactis species recognized by Fautin (2013), only three were described by Wassilieff (1908) from the eastern sea area of Japan in the Western Pacific: Ph. crassa, Ph. japonica, and Ph. magna (Table 4). Phelliactis yapensis n. sp. is the first species found from the tropical Western Pacific Ocean (Fig. 1). It differs from the three known species by the distinct scapulus above the scapus (vs. no clear differentiation between the scapus and capitulum) (Stephenson 1918, 1920). In addition, Ph. yapensis n. sp. differs from Ph. crassa by its larger body size (up to 104 mm high and 98 mm wide vs. 50 mm high and 25 mm wide); from Ph. japonica by the stronger sphincter (vs. weak); and from Ph. magna by the strongly asymmetric oral disc (vs. slightly asymmetric), stronger sphincter (vs. weak), fewer tentacles (maximum 165 in 2 cycles vs. 192 in 6 cycles), and the higher number of perfect mesenteries (8 pairs vs. 6 pairs and 2 unpaired). According to Riemann-Zürneck (1973), the species of Phelliactis can be classified into three groups. Phelliactis yapensis n. sp. has six pairs of perfect mesenteries in the first cycle and two additional pairs in the second cycle, and thus belongs to the Phelliactis hertwigi group - together with its ten congeners Ph. algoaensis Carlgren, 1928; Ph. capensis Carlgren, 1938; Ph. capricornis Riemann-Zürneck, 1973; Ph. coccinea (Stephenson, 1918); Ph. hertwigii Simon, 1892; Ph. incerta Carlgren, 1934; Ph. magna (Wassilieff, 1908); Ph. pelophila Riemann-Zürneck, 1973; Ph. pulchra (Stephenson, 1918); and Ph. siberutiensis Carlgren, 1928 (Table 4). By contrast, the seven species of Phelliactis that have only six pairs of perfect mesenteries belong to the Phelliactis robusta group: Ph. callicyclus Riemann-Zürneck, 1973; Ph. carlgreni Doumenc, 1975; Ph. crassa (Wassilieff, 1908); Ph. hydrothermala Sanamyan & Sanamyan, 2007; Ph. japonica (Wassilieff, 1908); Ph. robusta Carlgren, 1928; and Ph. somaliensis Carlgren, 1928. The remaining three species have 12 pairs of perfect mesenteries: Ph. americana Widersten, 1976; Ph. gigantea (Carlgren, 1941); and Ph. lophohelia Riemann-Zürneck, 1973 (Table 4; and references therein). Our holotype has also an excrescent pair of mesenteries in the fifth mesentery cycle. Such a pattern is likely a minor irregularity in the arrangement of mesenteries. Similar case was also observed in Ph. americana Widersten, 1976. TABLE 4. Cοmparisοn οf Phelliactis yapensis n. sp. with knοwn species οf Phelliactis Simοn, 1892. −, Data nοt available.Published as part of Li, Yang & Xu, Kuidong, 2016, Paraphelliactis tangi n. sp. and Phelliactis yapensis n. sp., two new deep-sea species of Hormathiidae (Cnidaria: Anthozoa: Actiniaria) from a seamount in the tropical Western Pacific, pp. 358-372 in Zootaxa 4072 (3) on pages 365-369, DOI: 10.11646/zootaxa.4072.3.5, http://zenodo.org/record/25524

Sternaspis sunae Wu & Xu, 2017, sp. nov.

<i>Sternaspis sunae</i> sp. nov. <p>Figure 8</p> <p> <b>Type material.</b> South China Sea. Holotype: MBM 198787, R/V sy3, Nansha Islands, Sta. 59, 224 m, 22 Sep. 1994. Paratype: MBM238398 (1 spec.), same collection information as the holotype. Body partly shrinks, 30 mm long, 10.9 mm wide; abdomen 16.2 mm long; left shield plate 4.84 mm long, 5.65 mm wide.</p> <p> <b>Description</b>. Holotype (MBM198787) complete, 38 mm long, 17 mm wide; abdomen 25 mm long; left shield plate 5.23 mm long, 6.21 mm wide. Body pale to yellowish, introvert fully exposed, with similar pigmentation as abdomen, constriction or waist segments relaxed (Fig. 8 A).</p> <p>Prostomium hemispherical, translucent pale (Fig. 8 B). Eyespots not seen. Boundary distinct on side and back of prostomium. Peristomium projected, covered with sediment particles, barely extending laterally and ventrally to anterior margin of first chaetiger. Mouth circular, projected, wider than prostomium, covered by minute papillae (Fig. 8 B).</p> <p>First three chaetigers each with 14–17 light brown hooks per side. Hooks slightly expanded sub-distally, spearhead-like with a medial furrow; hooks gradually shortened towards ventrolateral side (Fig. 8 B–D). Introvert covered by minute papillae. Genital papillae conical, with indistinct annular rings, protruding ventro-laterally from inter-segmental groove between segments 7 and 8. Anterior abdomen with 7 segments, partly covered by sediment; papillae minute, evenly distributed (Fig. 8 A, E). Capillaries not seen.</p> <p>Ventro-caudal shield brick red, with distinct concentric lines near margin; shield nearly rectangular, much wider than long (width-length ratio: 2.33–2.37) (Fig. 8 G, H). Anterior margins angular, anterior depression shallow; anterior keels covered by translucent integument layer. Suture restricted to anterior region, fused posteriorly into a furrow. Lateral margins straight, smooth, expanded posteriorly. Main ribs distinct, forming a shallow groove between lateral plates and fan; fan slightly ribbed, truncate, not extending beyond posterolateral corners; margin smooth or slightly crenulated, without a distinct median notch (Fig. 8 G, H).</p> <p>Marginal chaetae golden yellow, including 10 lateral fascicles and 6 posterior ones (Fig. 8 G, H); lateral fascicles successively longer from anterior to posterior, chaetae arranged in semi-closed oval; posterior fascicles similar in length, chaetae in linear arrangement. Peg chaetae tapering, with stout base. A small fascicle of very long, delicate capillary chaetae located in upper edge of peg chaetae. A fascicle of shorter capillary chaetae inserted between peg chaetae and outermost posterior fascicle, at least 3 times as long as posterior chaetae.</p> <p>Branchiae abundant, inserted on two plates. Branchial filaments slender, spiraled or curled; inter-branchial papillae long, curled, covered with fine sediment particles. Branchial plates oval, nearly parallel, with unclear boundaries (Fig. 8 F).</p> <p> <b>Variations.</b> The lateral margins of the shield are nearly straight (Fig. 8 G) or slightly expanded posteriorly (Fig. 8 H). The branchial plates are almost parallel in the holotype (Fig. 8 F) but divergent in the paratype.</p> <p> <b>Etymology.</b> <i>Sternaspis sunae</i> is named to honor Professor Ruiping Sun, in recognition of her contribution to the polychaete taxonomy in China, and in appreciation of her mentoring to the first author during the graduate student period.</p> <p> <b>Distribution.</b> South China Sea off the Nansha Islands (water depth 224 m).</p> <p> <b>Remarks.</b> The introvert hooks of <i>Sternaspis sunae</i> <b>sp. nov.</b> are spearhead-like with a median longitudinal furrow in the end portion, resembling those present in the genus <i>Petersenaspis</i> (Figs 2 F; 8D). However, all species of <i>Petersenaspis</i> have 8 segments in the pre-shield abdomen, and their shields have feebly developed ribs and no concentric lines. By contrast, <i>S. sunae</i> <b>sp. nov.</b> has seven segments in the pre-shield region and both radial ribs and concentric lines are well developed in the shield, like members of <i>Sternaspis</i>. These distinct features indicate the new species should be classified into the genus <i>Sternaspis</i>, though most species of <i>Sternaspis</i> have tapering introvert hooks.</p> <p> <i>Sternaspis sunae</i> <b>sp. nov.</b> is most similar to the new species <i>S. wui</i> <b>sp. nov.</b> described above because they have nearly rectangular ventro-caudal shields, six posterior chaetal fascicles, and similar color and arrangement of the chaetal fascicles. The two species differ clearly in the shape of the introvert hooks, which are spearhead-like with a median longitudinal furrow in <i>S. sunae</i> <b>sp. nov.</b>, but are tapering in <i>S. wui</i> <b>sp. nov.</b> (Figs 7 D; 8D). Besides, the two species can also be distinguished by the features of the shield. <i>Sternaspis sunae</i> <b>sp. nov.</b> has the shield suture restricted only in the anterior region and the concentric lines only visible near the margin, while in <i>S. wui</i> <b>sp. nov.</b> the suture extends throughout the shield and the concentric lines are distinct from the margin to the center.</p>Published as part of <i>Wu, Xuwen & Xu, Kuidong, 2017, Diversity of Sternaspidae (Annelida: Terebellida) in the South China Sea, with descriptions of four new species, pp. 403-415 in Zootaxa 4244 (3)</i> on page 413, DOI: 10.11646/zootaxa.4244.3.8, <a href="http://zenodo.org/record/430600">http://zenodo.org/record/430600</a&gt

Levensteiniella manusensis sp. nov., a new polychaete species (Annelida: Polynoidae) from deep-sea hydrothermal vents in the Manus Back-Arc Basin, Western Pacific

Wu, Xuwen, Xu, Kuidong (2018): Levensteiniella manusensis sp. nov., a new polychaete species (Annelida: Polynoidae) from deep-sea hydrothermal vents in the Manus Back-Arc Basin, Western Pacific. Zootaxa 4388 (1): 102-110, DOI: https://doi.org/10.11646/zootaxa.4388.1.

Four new species of Epacanthion Wieser, 1953 (Nematoda: Thoracostomopsidae) in intertidal sediments of the Nanji Islands from the East China Sea

Shi, Benze, Xu, Kuidong (2016): Four new species of Epacanthion Wieser, 1953 (Nematoda: Thoracostomopsidae) in intertidal sediments of the Nanji Islands from the East China Sea. Zootaxa 4085 (4): 557-574, DOI: http://doi.org/10.11646/zootaxa.4085.4.

Paroctonchus nanjiensis gen. nov., sp. nov. (Nematoda, Enoplida, Oncholaimidae) from intertidal sediments in the East China Sea

Shi, Benze, Xu, Kuidong (2016): Paroctonchus nanjiensis gen. nov., sp. nov. (Nematoda, Enoplida, Oncholaimidae) from intertidal sediments in the East China Sea. Zootaxa 4126 (1): 97-106, DOI: http://doi.org/10.11646/zootaxa.4126.1.