Leocrates chinensis Kinberg 1866

© 2018 Academia Sinica, Taiwan Open Access Redescription of Leocrates chinensis Kinberg, 1866 (Annelida, Hesionidae) Zhi Wang1, Jian-Wen Qiu1, and Sergio I. Salazar-Vallejo2,* 1Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong, China 2Depto. Sistemática y Ecología Acuática, El Colegio de la Frontera Sur, Chetumal, Quintana Roo, México (Received 20 December 2017; Accepted 12 January 2018; Published 5 February 2018; Communicated by Benny K.K. Chan) Citation: Wang Z, Qiu JW, Salazar-Vallejo SI. 2018. Redescription of Leocrates chinensis Kinberg, 1866 (Annelida, Hesionidae). Zool Stud 57:5. doi:10.6620/ZS.2018.57-05. Zhi Wang, Jian-Wen Qiu, and Sergio I. Salazar-Vallejo (2018) Leocrates chinensis Kinberg, 1866 is the type species of Leocrates Kinberg, 1866 (Annelida, Hesionidae). Its original description, based upon a single specimen collected in Hong Kong waters, was brief; its illustrations were published almost 50 years afterwards, and the type specimen was dried out before it could be redescribed. The late Marian Pettibone redescribed the species in 1970 but her illustrations of the species were based on specimens from the Mediterranean Sea, the Virgin Islands, and Samoa, not Hong Kong. In order to define the morphological features, we herein redescribe this species based upon newly collected specimens from the type locality. This species is characterized by the following features: prostomium subrectangular with a posterior notch, lateral antennae slightly longer than palps, palps with palpophores about 2.5 times longer than palpostyles, anterior eyes twice larger than posterior ones, slightly emarginated, posterior ones circular, median antenna fixed slightly ahead of posterior eyes, nuchal organs C-shaped; pharynx with a prominent dorsal papilla, a mid-dorsal jaw and a mid-ventral jaw; first four chaetigers subbiramous, others biramous with neuroacicular lobes blunt, as long as wide, or longer than wide; notochaetae spinulose capillaries; most neurochaetae with blades bidentate, guards approaching subdistal tooth; a few neurochaetae with long, tapered hoods. A key to identify all species in the genus is also included. Key words: Taxonomy, Polychaete, Leocrates, Hesionidae, Redescription, Hong Kong. *Correspondence: E-mail: [email protected], [email protected] BACKGROUND As a result of the Eugenie Expedition around the world in 1851-1853, Kinberg (1866, 1910) published a series of articles dealing with the annelid polychaetes. He proposed several families and genera, and described many new species. Diagnoses and descriptions were telegraphic and written in Latin, but the illustrations - prepared by P.D. Holm, C.E. Åkerman, A. Ringdahl, and himself - were of remarkably high quality. However, the plates were mostly published in the posthumous compilation, since only 8 out of 29 ones were available in 1858 (Théel 1910). Leocrates was proposed with L. chinensis as its type and only species, based upon a single specimen collected off Hong Kong (Kinberg 1866). The number of valid species belonging in the genus has changed over time out of the 19 nominal species; Pettibone (1970:212) included only seven, Fauchald (1977:76) indicated 11, and it has currently 13 recognized species (Read and Bellan 2013). However, at least partly due to the brief original description of L. chinensis, morphological features to delineate species in this genus are poorly defined, leading to the proposition of a few doubtful synonyms. The taxonomic history of this species is briefly reviewed below. Kinberg (1866) distinguished Leocrates from Hesione Savigny in Lamarck, 1818 that also has Zoological Studies 57: 5 (2018) doi:10.6620/ZS.2018.57-05 1 © 2018 Academia Sinica, Taiwan 16 chaetigers by three morphological features: a pharynx with jaws, a median antenna, and biramous parapodia with denticulate notochaetae. The original diagnosis for L. chinensis, translated from Latin, was: “prostomium wide, rectangular; first three segments of similar length; palps short, about half as long as lateral antennae; dorsal cirri longer than body width” (Kinberg 1866:244). The illustration, published as part of plate 23 (Kinberg 1910) shows that the prostomium is slightly wider than long; eyes are small, with the anterior pair slightly more separated than the posterior pair, but of about the same size; lateral antennae are about 1/3 longer than palps; the median papilla (facial tubercle ex auctore) has a transverse constriction; the dorsal sharp jaw is exposed and a lateral vesicle is present on the left side of pharynx. In chaetiger 10, the parapodium has a well-defined dorsal cirrophore, but there seems to be no ventral cirrophore, and the ventral cirrus is medial to neurochaetal lobe. Notochaetae are delicate and very finely denticulate, whereas neurochaetae are compound with blades 3-11 times longer than wide. All of Kinberg specimens were deposited in the Swedish Museum of Natural History, Stockholm, and the type material of L. chinensis has been examined by a number of authors. Ehlers (1901:83-84) indicated that the type specimen was in poor condition, and that he found no differences between it and his specimens collected from Juan Fernández off the Pacific coast of Chile. Ehlers’ illustrations (1901, Pl. 11, Figs. 10-15); however, show some differences despite the fact that the pharynx was exposed in both specimens. For example, in the specimens from Juan Fernández the prostomium is trapezoidal without a posterior notch, wider anteriorly, or about as long as wide, median pharyngeal papilla (facial tubercle) is larger than palps, anterior eyes are smaller than posterior ones, and neurochaetal blades are 4-7 times longer than wide. Hartman (1940: 212) thought that a Mediterranean species, L. claparedii (Costa in Claparède, 1868), could be a junior synonym of L. chinensis, and listed several publications recording these two species from Japan, Indonesia, Australia, Juan Fernández archipelago, and the Indian Ocean. Hartman (1949) examined Kinberg’s polychaetes; she indicated the there was a single type specimen of L. chinensis, that it has been dried out in 1913, but confused the type locality by saying it was from Honolulu, Hawaii (Hartman 1949:47). She also added that L. chinensis was recorded “from tropical seas of both hemispheres,” hence cosmopolitan, and cited her previous publication. Pettibone (1970) made a revision of Leocrates, concurred with Hartman’s supposed synonymy of L. claparedii, and included four other species as junior synonyms of L. chinensis: two from the Philippines (L. cupreus Grube, 1867 and L. iridus Grube, 1878), one from Japan (L. anonymus Hessle, 1925), and the other from Saint Thomas, Virgin Islands (L. longicirrata (Treadwell, 1902)). This conclusion indicates the cosmopolitan status for the species. Although the specimens she examined came from around the world, they did not include the type specimen. Thanks to a good editorial idea, the illustrations of some of her specimens were included such that their differences from the original description of the species can be readily noted. For example, there are differences in the size proportions between palpophore and palpostyle, between lateral antennae and median pharyngeal papilla (facial tubercle), the shape and development of nuchal organs, the position of median antenna, and the size of ventral cirri. These differences make the synonymy questionable, and stress the need to properly describe the species. In this contribution, we redescribe L. chinensis and give details about the variation of several diagnostic features based on recently collected topotype specimens, such that delimitation among different species of Leocrates can be made. This is especially relevant because, as indicated above, L. chinensis is the type species of Leocrates. Further, a key to identify all described species is also included. MATERIALS AND METHODS Fourteen specimens of Leocrates chinensis were collected during macrobenthic ecological surveys conducted in 2012 (Wang et al. 2017) and 2015 (Wang et al. submitted). The two surveys covered the same set of 28 stations across Hong Kong waters, divided into three areas: an estuary, a transitional zone, and an oceanic zone. Benthic samples were taken on board the survey vessel using a Van Veen grab and sieved through a 0.5 mm mesh. Materials retained on the sieve were fixed in a 5% formalin-seawater solution and stained with 1% Rose Bengal, later sorted and the specimens transferred into 75% ethanol for preservation. It must be noted that L. chinensis specimens were found only at two transitional zone page 2 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan sites in Victoria Harbour (stations 11 and 12 in Wang et al. 2017, at water depths of 14 m and 12 m, respectively). Specimens were deposited into two institutions: Swire Marine Institute, University of Hong Kong (SWIMS) and El Colegio de la Frontera Sur, Chetumal, México (ECOSUR). Specimens were observed under an Olympus SZX9 stereo microscope and a Motic BA210 compound microscope. A relatively intact specimen was selected for redescription and selected specimens were prepared for observation under a LEO 1530 FESEM scanning electron microscope for finer details. The dissected materials were dehydrated in graded series of alcohol (75%, 95% and 100%), dried with graded series of hexamethyldisilazane (50%, 75% and 100%), observed under the light microscopes, then coated with gold, and observed under the electron microscope. Light microscopic photographs were taken using either a Canon 550D digital camera mounted on the dissecting microscope, or a True Chrome II camera mounted on the compound microscope. The depth of each photograph was enhanced by stacking 20-30 photographs of the same object with different focuses using the software Helicon Focus 6. RESULTS SYSTEMATICS Family Hesionidae Grube, 1850 Subfamily Hesioninae Grube, 1850 Tribe Hesionini Grube, 1850 Genus Leocrates Kinberg, 1866 Type species: Leocrates chinensis Kinberg, 1866, by monotypy. Type locality: Hong Kong. Leocrates Kinberg, 1866: 244, 1910: 57; Pleijel 1998:108-109 (synonymy). Diagnosis: Body with 16 chaetigers. Prostomium with two pairs of eyes, palps biarticulate; three antennae. Nuchal organs usually exposed, either horizontal C-, Lor U-shaped. Pharynx with prominent dorsal papilla, and a ventral jaw and one or two dorsal jaws. Peristomium with eight pairs of tentacular cirri. Parapodia biramous, except a few anterior subbiramous ones. Notochaetae subidstally spinulose capillaries. Neurochaetae heterogomph compound falcigers; blades unior bidentate, guards present, approaching subdistal tooth or slightly surpassing it. Leocrates chinensis Kinberg, 1866 restricted (Figs. 1-3, Table 1) Leocrates chinensis Kinberg, 1866: 244; Kinberg 1910: 57, pl. 23 fig. 7; Pettibone 1970: 14-20, Figs 12-15 (partim). Material examined: Victoria Harbour, Hong Kong: Three specimens (SWIMS-ANN-18-001, SWIMS-ANN-18-002, SWIMS-ANN-18-003), 22°17'29.91"N, 114°09'29.98"E, 14 m, sand, 6 Jun. 2012, 12.0-20.2 mm long, 4.5-5.0 mm wide including chaetae; 10 specimens (SWIMSANN-18-004, SWIMS-ANN-18-005, SWIMSANN-18-006, SWIMS-ANN-18-007, SWIMSANN-18-008, SWIMS-ANN-18-009, SWIMSANN-18-010, SWIMS-ANN-18-011, and ECOSUR 2905, ECOSUR 2906), 22°17'36.72"N, 114°09'21.06"E, 14 m, sand, 30 Jun. 2015, 9.520 mm long, 2.5-6.0 mm wide including chaetae; 1 specimen (ECOSUR 2904), 22°18'14.34"N, 114°11'46.68"E, 12 m, sandy silt, 8 Jun. 2015, 23.2 mm long, 8.0 mm wide including chaetae. Description: Best preserved specimen (ECOSUR 2904) nearly complete; body stout with most cirri still present; integument without pigmentation in ethanol (Fig. 1A). Prostomium subrectagular, slightly wider anteriorly, posterior notch about 1/4 as long as prostomium (Figs. 1B, C). Lateral antennae tapered, slightly longer than palps, about as long as prostomium. Palps biarticulate, palpophores thicker and about 2.5 times longer than palpostyle. Eyes black, trapezoidally distributed; anterior pair about twice as large as posterior ones, wider apart, oval, with a small anterolateral notch; posterior eyes smaller, oval. Median antenna tapered; base slightly anterior to top of posterior notch, parallel with posterior eyes. Nuchal organs C-shaped; refringent ciliated bands along posterolateral and posterior prostomial edges (Fig. 1C). Pharynx with prominent dorsal papilla located immediately anterior to frontal edge of prostomium; subconical, wider than long, not apparently constricted subdistally, base width about 1.5 times of palpophores, half as long as lateral antennae (Figs. 1D, E). Pair of swollen vesicles, located laterofrontally to prostomium (Fig. 1D); 20 papillae on outer edge (Fig. 1E, Table 1). Two chitinous sharp jaws (Fig. 1E); dorsal jaw single, larger than ventral one (Fig. 1F). Tentacular cirri biarticulate; cirrophores cylindrical with 8-9 rings; aciculae black, as long page 3 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan Fig. 1. Leocrates chinensis Kinberg, 1866. A, C, F: Sample 13 (ECOSUR 2904; middle antenna missing); B, D, G: Sample 10 (SWIMSANN-18-007); E: Sample 7 (SWIMS-ANN-18-003). (A) dorsal view; (B-C) dorsal view of prostomium; (D-E) ventral view of pharynx; (F) dorsal (larger) and ventral (smaller) jaws, lateral view. (G) tentacular cirri, showing cirrophore and basis of cirrostyle; (H) posterior end, dorsal view (right anal cirrus missing). Scale bars: A = 2 mm; B-E, G = 500 μm; F = 200 μm. as half cirrophore; cirrostyle filiform multiarticulate, superior cirrostyles longer than inferior ones, longest ones reaching chaetiger 5 (Figs. 1A-B, G). First 4 chaetigers with subbiramous parapodia (Fig. 2D). Dorsal cirri biarticulate, similar in shape and length to superior tentacular cirri, longer than body width (Fig. 1A); aciculae extending along half the length of cirrophores. Parapodia lobeshaped with upper acicular lobes globose, prechaetal; about twice longer than wide; aciculae black, extended into acicular lobes. Ventral cirri without cirrophore, filiform, extending to tip of neurochaetae. Chaetigers 5-16 with biramous parapodia (Figs. 2E-G). Dorsal cirri biarticulate; cirrophore cylinder-shaped, with 8-12 rings; cirrostyle filiform, as long as 4-5 chaetigers (Fig. 1A). Notopodia conical, positioned anteriorly to dorsal cirri. Notoaciculae black, extending to near tip. Neuropodia much larger than notopodia, lobeshaped with upper acicular lobes globose, prechaetal, 1.5 times longer than wide. Ventral cirri without cirrophore, filiform, extending to near tips of neurochaetae (Figs. 2E-G). (A) (F) (B) (G) (C) (D) (H) (E) page 4 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan Notochaetae capillaries, cross-striated, subdistally spinulose to near tips, spines arranged in transverse series, decreasing in number distally (9-10 spines per series basally, 1-2 distally) (Figs. 3A-F). Notochaetal numbers more abundant in mid-body segments (20 in chaetigers 5 and 16, 50 in chaetiger 8) (Figs. 2E-G). Most neurochaetae heterogomph falcigers; blades bidentate; distal teeth stronger in longer blades, while subdistal teeth stronger in shorter blades, but variable due to abrasion; guard (spine) extending to or slightly beyond subdistal tooth; (Figs. 3G-P). Blade cutting edges finely spinous, especially distinct in longer blades. Neurochaetal numbers variable; more abundant in median parapodia (about 30 in chaetiger 2, 50 in chaetiger 5, 35 in chaetiger 8, 15 in chaetiger 16); shorter blades straight; longer blades bending downward slightly (Figs. 3G-N). Delicately hooded falcigers rarely present, 0 or 2 per parapodia, usually distributed as most ventral neurochaetae, sometimes among non-hooded neurochaetae (Figs. 2H-I, 3O-P). Pre-anal segment without chaetae but with two pairs of lateral cirri; dorsal cirri with cirrophore, ventral ones without it; ventral cirri shorter and thinner than dorsal ones (Fig. 1G). Pygidium with anus dorsally, pair of anal cirri attached ventrally, about as long as those in previous segment. Variation: All specimens have 16 chaetigers and the parapodia become biramous from chaetiger 5. The prostomium is wider than long, but the width/length ratio depends upon pharynx eversion, ranging from 1.20 to 1.40 when only slightly exposed, and 1.33 to 1.76 when nearly fully exposed (Table 1). The posterior notch in prostomium is always visible, even in pharynx extended specimens where the nuchal organs are partially hidden by the posterior prostomial edge and the anterior margin of tentacular segments (Figs. 1B, C; 2A-C). The ratio of palp length/ lateral antenna length varies slightly according to the condition of fixation, but close to 1 in most specimens. The anterior eyes are always roughly twice the size of anterior eyes, but the eye shape varies slightly: in most specimens the anterior eyes are oval with a small anterolateral notch, while few others are fully oval without notch; posterior eyes are always round, sometimes with a small black spot near one of them (Figs. 1B, 2A-C). The middle antenna is tapered, 1/4 as long as prostomium; in some specimens the median antenna is lost but its place of attachment is indicated by a scar (Figs. 1B-C, 2A-C). The palpophores are always much thicker and about 2.5 times the length of the palpostyles. The pharynx has a circlet of 20 terminal papillae along the outer edge, but they are only visible when the pharynx is nearly fully extended (Figs. 1D-E). Two swollen lateral vesicles at the base of pharynx are visible in all specimens, but they are more distinct when Table 1. Morphological features of Leocrates chinensis. Body width data (with chaetae, and without chaetae) were taken from a middle chaetiger. Prostomium (W/L) are ratios of prostomial width/length. Hooded neurochaetae represent the number of hooded chaetae and hooded chaetae bearing parapodia in one specimen. Blade (L/W) are the range of blade length/width ratio Catalogue Body length (mm) Body width (mm) Prostomium (W/L) Pharynx extension Marginal papillae* Hooded neurochaetae Blade (L/W) SWIMS-ANN-18-001 20.2 5.0, 4.0 1.50 near fully 20 9 in 9 parapodia 5.2-14.8 SWIMS-ANN-18-002 12 4.5, 3.5 1.20 slightly 12 7 in 7 parapodia 4.6-19.6 SWIMS-ANN-18-003 16.9 4.5, 3.5 1.33 near fully 20 6 in 5 parapodia 4.0-18.8 SWIMS-ANN-18-004 20 6.0, 5.0 1.40 slightly 20 4 in 4 parapodia 5.3-20.0 SWIMS-ANN-18-005 20 5.0, 4.0 1.29 slightly 20 1 in 1 parapodium 5.0-15.0 SWIMS-ANN-18-006 16.5 5.0, 4.0 1.38 slightly 20 4 in 4 parapodia 5.2-16.9 SWIMS-ANN-18-007 16.6 5.5, 4.5 1.38 slightly 12 2 in 2 parapodia 4.4-18.1 SWIMS-ANN-18-008 15 5.0, 4.0 1.25 slightly 20 4 in 4 parapodia 5.5-18.5 SWIMS-ANN-18-009 20 5.0, 4.0 1.64 near fully 20 2 in 2 parapodia 5.3-17.6 SWIMS-ANN-18-010 15 5.0, 4.0 1.69 near fully 20 4 in 4 parapodia 5.8-12.6 SWIMS-ANN-18-011 9.5 2.5, 1.8 1.28 slightly not distinct 1 in 1 parapodium 5.1-19.2 ECOSUR 2904 23.2 8.0, 6.0 1.33 slightly 12 9 in 9 parapodia 5.2-18.7 ECOSUR 2905 14.9 5.0, 3.5 1.45 near fully 20 4 in 4 parapodia 4.6-16.3 ECOSUR 2906 18.2 5.5, 4.5 1.76 near fully 20 1 in 1 parapodium 4.3-14.4 *These are not papillae; they are wrinkles. Some have 12 only because the pharynx is not fully extended. page 5 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan the pharynx is nearly fully extended. The dorsal papilla in all specimens is subconical, without apparent constriction in any specimens; the length of the dorsal papilla apparently varies substantially among the specimens, but when the pharynx is extended and the papilla, lateral antennae and palps are in the same plane, it is 1/2 to 2/3 as long as the lateral antennae (Figs. 2A-C). The falciger blade length/width (L/W) ratios are smaller in the inferior chaetae than in the superior ones in all chaetigers. The largest ratio in each chaetiger declined from anterior to posterior. For instance, in the largest specimen, the largest ratio changes from 18.7 in chaetiger 3 to 14.6 in chaetiger 7 and to 11.4 in chaetiger 16; however, the smallest ratio does not change substantially, ranging from 5.2 to 5.5 along the whole worms (Figs. 3G-N; Table 1). The hooded neurochaetae are present in all 14 specimens, from chaetiger 2 to 16, but their number varies from 0-2 per parapodium, 1-9 per specimen, and 1-8 parapodia with this type of chaetae (Figs. 2D, H-I, 3O-P; Table 1). However, since the hooked chaetae are shorter than other neurochaetae and are difficult to see without dissecting the parapodia, the true numbers of this type of chaetae might be underestimated. The Fig. 2. Leocrates chinensis Kinberg, 1866. Anterior end of three specimens with extended pharynx, dorsal view, and parapodial features. (A) Sample 9 (ECOSUR 2905); (B) Sample 11-3 (ECOSUR 2906); (C) Sample 11-1 (SWIMS-ANN-18-009). Sample 13 (ECOSUR 2906). (D) chaetiger 2, anterior view (cirrostyle missing); (E) chaetiger 5, anterior view (cirrostyle broken); (F) chaetiger 8, anterior view; (G) chaetiger 16, anterior view; (H) chaetiger 2, anterior view, with a hooded neurochaeta in inferior position; (I) chaetiger 7, posterior view, with two hooded neurochaetae. Scale bars: A-C = 500 μm; D-G = 500 μm; H-I = 200 μm. (A) (B) (G) (D) (C) (H) (I) (E) (F) page 6 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan Fig. 3. Leocrates chinensis Kinberg, 1866. Sample 13 (ECOSUR 2904). A-D, H, L: Chaetiger 6; E, J: Chaetiger 16; F: Chaetiger 8; G, K: Chaetiger 3; I: Chaetiger 9; M: Chaetiger 7; N: Chaetiger 15. (A) notochaetae; (B) notochaetal basal region; (C) notochaetal median region; (D) notochaetal tip; (E) notochaetal median region with transverse series of spines; (F) same, under lower magnification; (G-J) subdorsal neurochaetae with longest blades; (K-N) ventral neurochaetae with shortest blades; (O-P) hooded neurochaetae. Scale bars: A-D, K-P = 100 μm; E-F = 3 μm; G-J = 250 μm. (A) (B) (G) (H) (I) (C) (J) (D) (O) (K) (L) (M) (N) (P) (E) (F) page 7 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan anal cirri are usually lost; if present, they can reach chaetiger 14. The anus is dorsal in all specimens. No oocytes were observed in any specimens. Distribution: Victoria Harbour, Hong Kong. Other records require confirmation. DISCUSSION The holotype and only specimen of Leocrates chinensis Kinberg, 1866 was collected by the Swedish naval frigate Eugenie during a round-theworld cruise in 1851-1853. The original locality of L. chinensis, translated from Latin, is “China, sea next to the castle near Hong Kong, bottom 2 fathoms”. During that period, the Hong Kong Island was under British control, and the castle Kinberg referred to was likely the Murray Barracks (22°16'40.8"N, 114°09'39.6"E), which was at the shore of Victoria Harbour. Since the water depth of the type locality was only 2 fathoms (about 3.7 meters), we suspect that the frigate Eugenie was anchored just in front of the military base, and specimens were collected near shore using a smaller boat. Specimens of L. chinensis studied here were all collected inside Victoria Harbour, close to the original locality, but in slightly deeper waters (12-14 m). Our specimens match the description by Kinberg (1866 1910) in several key morphological features including the shape of the prostomium, the locations and relative sizes of the antennae, the palps and the dorsal papilla, the locations of the four eyes, the shape of the mid-dorsal tooth, the shapes of the dorsal capillaries and ventral non-hooked falcigers, the shape of the parapodia, and the length of the dorsal cirri. However, the newly collected specimens show the following differences: 1) in the original description the eyes are similar in size, but in our specimens the anterior pair is consistently twice as large as the posterior pair; 2) the C-shaped nuchal organs (i.e. cilia band along posterolateral and posterior prostomial edges) were not mentioned or illustrated in the original description, probably due to the fully everted pharynx that compressed the prostomium towards the peristomium, making them unobservable, as is the case for some of our specimens with extended pharynx (Figs. 2A-C); 3) in the original description, the dorsal papilla on the pharynx - located immediately anterior to the frontal prostomial margin - has a delicate transverse constriction, which could be an artifact of preservation; none of our samples show this; and 4) the original illustration shows a swollen vesicle on the left side, close to the tip of the extended pharynx; in our samples, there are two swollen vesicles near the base, but this difference could be due to the difference in the extend of eversion of the pharynx, or an artifact of preservation. Further, Kinberg also showed that the notochaetae of L. chinensis are capillary; the neurochaetae are compound heterogomph with bidentate blade, longer in superior position, straight guard reaching subdistal tooth. However, he did not observe the hooded neurochaetae, probably because this type of chaetae is not present in every parapodia, or because he did not check all parapodia. Previous studies noticed the prominent dorsal papilla as a diagnostic feature for Leocrates (Pettibone 1970; Pleijel 1998), but the term “facial tubercle” they used might be inappropriate as it gives a false impression that it is a prostomial structure. Our observations (Fig. 2B) confirm Grube’s (1878) and Ehlers’ conclusions (1901) that it is a pharyngeal structure. It is homologous to the middorsal pharynx papilla in Hesione (e.g., Kinberg 1910, Pl. 23, Fig. 8B for H. eugeniae Kinberg, 1866), but it is more basal in Leocrates. Therefore, we use dorsal papilla instead of facial tubercle when referring to this structure. Nevertheless, there are two differences between the dorsal papilla of Leocrates and that of Hesione: 1) this structure in Leocrates is much larger, and 2) as a consequence of this hypertrophy, when the pharynx is withdrawn, the dorsal papilla of Leocrates is clearly visible, whereas that of Hesione is not. The additional morphological details of L. chinensis provided in the present study should help clarify the statuses of several species that were synonymized. For instance, among the 10 species and one subspecies proposed as junior synonyms of L. chinensis by Pettibone (1970), three specimens were illustrated. The specimens collected from St. Thomas in the Western Atlantic (Fig. 14 in Pettibone 1970) and Samoa in the Western Pacific (Fig. 15 in Pettibone 1970) both have prominent L-shaped rather than C-shaped nuchal organs. Consequently, they should not be included under the same species name. The specimen from the Mediterranean Sea has a prostomium that closely matches that of L. chinensis, but its notopodia are stronger and the notochaetae form a fan-shaped array (Fig. 13 in Pettibone 1970), rather than a bundle as in L. chinensis; further, the blade of the longest page 8 of 11Zoological Studies 57: 5 (2018) © 2018 Academia Sinica, Taiwan neurochaetae appears to have lower L/W ratio than those present in our specimens of L. chinensis. However, L. claparedii was redescribed recently by Parapar et al. (2004) and their study helps to clarify the differences with L. chinensis and to restrict it. In L. chinensis palpophores are twice longer than palpostyles, anterior eyes are twice larger than posterior ones, and neurochaetal blades in median chaetigers are 5-15 times longer than wide, whereas in L. claparedii palpophores are three times longer than palpostyles, anterior eyes are slightly larger than posterior ones, and neurochaetal blades in median chaetigers are 3-10 times longer than wide. On the other hand, there are two figures of specimens identified as L. chinensis in Pleijel’s revision. The first one (Pleijel 1998:111, Fig. 6) depicts a juvenile (8 chaetigers; 1 mm long) specimen from the Great Barrier Reef which has C-shaped nuchal organs, groups of cilia over the median papilla, no notochaetae, and very long, delicate, twisted neurochaetae. We cannot confirm its identity because we have not studied juveniles or newly recruited larvae. The second is a larger specimen (Pleijel 1998:112, Fig. 7), collected from Madang, Papua New Guinea, which has a longer than wide prostomium, medially attached median antennae, and U-shaped nuchal organs (posterior notch extending to the middle of prostomium); these features differ from both the original description and our redescription. We think this specimen belongs to another species. Pettibone (1970) recognized seven species of Leocrates. Among them, L. djangkarensis Augener & Pettibone in Pettibone, 1970 and L. wesenberglundae Pettibone, 1970 could be distinguished from L. chinensis by having unidentate, rather than bidentate neurochaetae. Two species of Leocrates have been reported from Hong Kong (Shin and Thompson 1982, Shin 1998, Wang et al. 2017). L. chinensis occurs in the coarser sandy to sandy silt bottom in Victoria Harbour, whereas L. wesenberglundae, having compound neurochaetae with a tapered fine tip, is distributed in muddy bottoms in more southern waters. Sun and Yang (2004:82) keyed out two Leocrates species in China seas: L. chinensis and L. claparedii. They separated the former from latter according to the presence of balloon-like vesicles and bilateral spinous notochaetae. We think that, if no other difference is found, both records should belong to the same species. First, vesicles are present and visible in all our Leocrates specimens, though in some they are not distinct due to slightly extended pharynx; their presence could be widely distributed in Leocrates species, and consequently, they cannot be diagnostic. Second, the successive transverse series of spines in notochaetae have a variable number of spines; when they are more abundant, they could extend up to half the chaetal diameter, and this would explain why they have been illustrated as being present along a single side, or along both sides. After the examination of these structures, and in confirmation of the findings by Parapar et al. (2004:223, Fig. 79C), these notochaetae have transverse series of spines instead of having lateral denticles. Again, the extent of the series of denticles along chaetae varies in the same chaetal bundle, and could not be used as a diagnostic character. Several studies had shown the presence of hooded neurochaetae in Leocrates species. Ehlers (1901) illustrated this kind of chaetae for what he regarded as L. chinensis collected from the coast of Juan Fernández, but his illustration shows that the posterior eyes are twice the size of anterior eyes, therefore they differ from L. chinensis. Fauvel (1923:236, repeated in 1953:106) provided a figure of it in what he regarded as L. claparedii from India. However, no details about the number and distribution of hooded chaetae along body were presented. Our examination of the L. chinensis specimens indicates that the hooded chaetae, when present, are usually located among chaetae in the lower chaetal bundle, and that a large part of the shaft is usually embedded in the parapodia, with only the blade exposed, and this explains why they can be referred to as newly exposed chaetae. These chaetae are present in either side of the body, from anterior to posterior (except chaetiger 1) parapodia. These chaetae are more frequent in chaetigers 5-10, and 13-15, with frequencies of 52% and 28% respectively. In most parapodia when the hooded chaetae are present, the number is just one, and rarely two per bundle. Since the hooded neurochaetae are similar and as complex as the other neurochaetae, we conclude that their hoods are due to their recent emergence of the body wall, and that they could be widely distributed in Leocrates species. Key to species of Leocrates Kinberg, 1866 (modif. Pettibone 1970; references therein) 1 Neurochaetal tips bidentate .......................................... 2 - Neurochaetal tips entire, not bidentate; upper neurochaetae with very long blades; notochaetae from page 9 of 11Zoological Studies 57: 5 (2018)