Leocrates chinensis Kinberg, 1866

Wang, Zhi, Qiu, Jian-Wen & Salazar-Vallejo, Sergio I., 2018, Redescription of Leocrates chinensis Kinberg, 1866 (Annelida, Hesionidae), Zoological Studies (Zool. Stud.) 57 (5), pp. 11-11 : 3-8

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 (SWIMS- ANN-18-004, SWIMS-ANN-18-005, SWIMS- ANN-18-006, SWIMS-ANN-18-007, SWIMS- ANN-18-008, SWIMS-ANN-18-009, SWIMS- ANN- 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, 9.5- 20 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 as half cirrophore; cirrostyle filiform multiarticulate, superior cirrostyles longer than inferior ones, longest ones reaching chaetiger 5 ( Figs. 1 A-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. 2 E-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. 2 E-G).

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. 3 A-F). Notochaetal numbers more abundant in mid-body segments (20 in chaetigers 5 and 16, 50 in chaetiger 8) ( Figs. 2 E-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. 3 G-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. 3 G-N). Delicately hooded falcigers rarely present, 0 or 2 per parapodia, usually distributed as most ventral neurochaetae, sometimes among non-hooded neurochaetae ( Figs. 2 H-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 ; 2 A-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 , 2 A-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. 1 B-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. 1 D-E). Two swollen lateral vesicles at the base of pharynx are visible in all specimens, but they are more distinct when

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. 2 A-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. 3 G-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 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.

Figures

Fig. 1. Leocrates chinensis Kinberg, 1866. A, C, F: Sample 13 (ECOSUR 2904; middle antenna missing); B, D, G: Sample 10 (SWIMS- ANN-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.

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.

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.