Leocrates chinensis Kinberg, 1866

Figs 26, 27

Leocrates chinensis Kinberg, 1866: 244; 1910: 57, Pl. 23, Fig. 7; Horst 1924: 193 (partim), Hartman 1949: 47; Imajima & Hartman 1964: 82; Pettibone 1970: 214–218 (none of the figures, Siboga specimens partim), Wang et al. 2018: 3–9, Figs 1–3 (redescr.).

Leocrates anonymus Hessle, 1925: 15–18, Fig. 4 a–e.

Type material. Western Pacific. Japan. Holotype of Leocrates anonymous Hessle, 1925 (UUZM 672), Sagami, Misaki, intertidal, 5 Jun. 1914, S. Bock, coll.

Additional material. Western Pacific. Hong Kong. Seven specimens (UF 5705), Che Lai Pai, ARMS (autonomous reef monitoring structure), submerged for 2 years (22°27’46.8” N, 114°17’27.6” E), 4 m, sandy bottom, 31 Oct. 2017, D. Baker, coll. [15–25 mm long, 2.0– 3.5 mm wide]. One specimen (UF 5737), juvenile, Tung Pin Chau, ARMS submerged for 2 years (22°32’34.80” N, 114°26’20.40” E), 4 m, patchy corals, 24 Oct. 2017, D. Baker, coll. [15.5 mm long, 1.8 mm wide]. One specimen (UF 5747) Centre Island, ARMS submerged for 2 years (22°28’01.20” N, 114°13’15.60” E), 4 m, sandy bottom, 26 Oct. 2017, D. Baker, coll. [26.5 mm long, 2.5 mm wide]. Two specimens (UF 5748), Centre Island, ARMS submerged for 2 years (22°26’13.20” N, 111°13’15.60” E), 4 m, sandy bottom, 26 Oct. 2017, D. Baker, coll. [data used for variation]. Three specimens (UF 5786), largest specimen without posterior region, Che Lai Pai, ARMS submerged for 2 years (22°27’46.8” N, 114°17’27.6” E), 4 m, sandy bottom, 28 Oct. 2017, D. Baker, coll. [19.5–20.5 mm long, 2 mm wide]. Japan. One specimen (ECOSUR 3076), Hachijo Island, Yaene (33°05’55.3” N, 139°46’16.8” E), 5–12 m, 18 May 2018, N. Jimi, coll. [19 mm long, 2.5 mm wide]. One specimen (ECOSUR 3077), Kagoshima, Bonotsu (31°15’15.04” N, 130°12’53.90” E), 5–15 m, 26 Jul. 2018, N. Jimi, coll. [19 mm long, 3 mm wide]. One specimen (SIO A4147), Izu Peninsula, East Honshu, Suruga Bay, Cape Koganezaki (34°50’34.80” N, 138°45’46.44” E), 4–10 m, 24 Oct. 2008, F. Pleijel, coll. [16 mm long, 2 mm wide]. Indonesia. Two specimens (ZMA V.Pol. 534.6), Irian Jaya, R/ V Siboga Exped., Sta. 273, Aru Islands (06°10’ S, 134°30’ E), Pearl Banks (anchorage off Pulu Jedan), 13 m, trawl, dredge and divers, sand and shells, 23- 26 Dec. 1899 [17–18 mm long, 2–3 mm wide]. One specimen (ZMA V.Pol. 1902), Sulawesi, R/ V Siboga Exped., Sta. 213, Saleyer (06°00’ S, 120°30’ E) anchorage, 36 m, coral reef exploration, muddy bottom + sand, 26 Sep. 1899 [17 mm long, 2.5 mm wide].

Description. Holotype of L. anonymous Hessle, 1925 (UUZM 672) complete, slightly bent laterally (Fig. 26A), integument variably damaged. Body with parallel sides, blunt anteriorly, barely tapered posteriorly, 29 mm long, 3 mm wide (without parapodia), 16 chaetigers; left parapodia of chaetigers 4 and 8 previously removed, left parapodia of chaetigers 7 and 15 dissected (kept in container). Most tentacular and dorsal cirri on site, most without tips, some ventral cirri missing. Body pale, eyes pale brown (barely pigmented).

Prostomium wider than long, slightly wider anteriorly (Fig. 26B). Lateral antennae with ceratophores welldefined, antennae shorter than prostomial length, slightly longer than palps. Palpophores 3–4 times longer than palpostyles. Median antenna broken, probably not reaching anterior prostomial margin, inserted between posterior eyes. Eyes pale brown round, anterior eyes slightly larger than posterior ones.

Nuchal organs lobes concelead by tentacular belt, horizontal C-shaped; lateral ciliated bands barely visible. Tentacular cirri mostly on site, without tips, longer ones reach chaetiger 7. Lateral cushions low, entire, longitudinal striae visible.

Pharynx fully exposed, slightly expanded distally. Lateral vesicles present on both sides, swollen, round (Fig. 26 B–D). Anterior margin smooth, subdistal circle of irregular constrictions, better defined laterally. Dorsal jaw brownish, exposed, inserted in pharynx margin, in lateral view scimitar-like; ventral jaw exposed, submarginal, smaller than upper one.

Chaetigers 1–4 without notochaetae; notochaetae present along chaetigers 5–16, up to 30 per bundle, most broken, delicate, arranged in transverse fans, notochaetae subdistally denticulate, denticles fine. Dorsal cirri as long as body width (including parapodia). Notacicular lobes tapered, neuracicular lobes projected, blunt, tips round, 1.5 times longer than wide (Fig. 26E); aciculae black, tapered; ventral cirri surpassing neurochaetal lobes. Neurochaetae about 20 per bundle (only one with hood), blades decreasing in size ventrally, bidentate, 4–10 times longer than wide, guards approaching subdistal tooth.

Posterior region tapered, with several lateral and anal cirri on site, but tips broken. Prepygidial segment with dorsal cirri three times longer than ventral ones. Pygidium with anus terminal, a small lateral fracture, anal cirri long, without tips, reaching chaetiger 15.

Oocytes not seen.

Variation. Two topotypes (UF 5748) complete, 26 mm long (other topotypes 15.0– 26.5 mm long), 2–3 mm wide, 16 chaetigers. Left parapodium of chaetiger 8 removed. Both specimens with lateral antennae longer than prostomium, slightly longer than palps; palpophores three times longer than palpostyles (Fig. 27A, D). Eyes brownish, anterior ones each 1 / 10 prostomial width, twice larger, anterolaterally slightly emarginate, and farther apart to each other than posterior ones, round. Median antenna shorter than prostomium. Pharynx partially exposed in smaller specimen; lateral vesicles present only on left side, round; anterior margin with 24 regular constrictions, ventral ones smaller (Fig. 27B). Dorsal and ventral jaws hyaline, yellowish, exposed, tapered, ventral jaw smaller than dorsal one. Dorsal cirri as long as body width including parapodia (Fig. 27C, E). Chaetigers 1–4 without notochaetae; notochaetae present along chaetigers 5–16, about 50 per bundle, delicate, denticles coarse (visible in 10X). Neurochaetae about 30 per bundle, bidentatae, 4–11 times longer than wide, teeth of about the same size. Oocytes not seen.

Remarks. Leocrates chinensis Kinberg, 1866 resembles L. giardi Gravier, 1900 from the Red Sea because both species have small eyes, but anterior ones larger than posterior ones, and straight prostomial lateral margins. However, there are some differences between these two species, especially regarding length of neurochaetal blades, and notochaetal denticulation. In L. chinensis neurochaetal blades are 3–18 times longer than wide, and notochaetae have coarse denticles, whereas in L. giardi neurochaetal blades are 3–10 times longer than wide, and notochaetae have fine denticles.

Further, L. chinensis resembles L. ahlfeldae n. sp. from India because both have small eyes, notacicular lobes tapered, and neurochaetal blade with teeth of similar size. There is a difference regarding the relative position of eyes when seen from above, that deserves explanation. The anterior eyes are always set farther apart than posterior eyes; however, posterior eyes might be sligthly, or markedly displaced medially. In the first condition, the posterior eyes can have a higher relative overlap along the level of the anterior eyes, and be more distant to each other, whereas if they are more displaced dorsally, they will have a smaller relative overlap with anterior eyes, and be closer to each other. Consequently, the differences between these two species are that in L. chinensis the lateral vesicles are round, and their posterior eyes have a slight overlap with anterior eyes, appearing slightly closer to each other than anterior eyes; whereas in L. ahlfeldae lateral vesicles are tapered, and posterior eyes position falls within anterior eyes level, with a slight overlap, appearing closer to each other than anterior eyes.

Leocrates anonymus Hessle, 1925 has been regarded as a possible junior synonym of L. chinensis Kinberg, 1866 by Hessle (1925: 17), Monro (1926: 313), Pettibone (1970: 215), and Pleijel (1998: 160). Their conclusions are herein confirmed. The only difference relies on the shape of the pharynx upper jaw because in the holotype of L. anonymous it is scimitar-shaped, whereas it is subcylindrical and tapered in L. chinensis. This difference can be explained by the size of the specimen, such that larger specimens have a midventral keel projection, and this was also confirmed in some larger topotypes of L. chinensis.

Leocrates chinensis Kinberg, 1866 was redescribed recently based upon topotype specimens (Wang et al. 2018); however, these additional topotypes are slightly larger (previously studied ones up to 23 mm long), and some features are indicated and illustrated, such as the pharynx lateral vesicle.

The records for the Mediterranean Sea were probably following Pettibone’s (1970) synonymy, which was probably derived from Hartman (1965: 24), such as Sordino (1990: 37-38), should be referred to L. claparedii (Costa in Claparède, 1868). On the other hand, there are several records from the Western Pacific, but could not be confirmed because no specimens were available, such as Augener (1922a: 22, 1927: 131–132), Monro (1931: 12), Pleijel (1998: 111, Figs 6–8 (partim, perhaps only Fig. 6), and Pleijel & Gustavsson (2010: 95, Fig. 1d).

Distribution. Japan to Indonesia, including Hong Kong, in sandy or mixed bottoms in shallow areas (4–15 m depth).