Paralamprophaea diplognatha ( Monro, 1926 ) Salazar-Vallejo, 2020

Salazar-Vallejo, Sergio I., 2020, Revision of Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 (Annelida, Errantia, Hesionidae), Zootaxa 4739 (1), pp. 1-114 : 94-96

Paralamprophaea diplognatha ( Monro, 1926) n. comb.

Figs 54 , 55

Leocrates diplognathus Monro, 1926: 313–315 , Figs. 1–2 ; Pettibone 1970: 218–219, Fig. 16 a–h.

Type material. South China Sea. Four syntypes ( BMNH 1926.4.30.123–125), Macclesfield Bank, no further data [largest syntype used for description; others used for variation] .

Additional material. Japan. One specimen ( ECOSUR 3080 ), off Yakushinsone, TR / V Toyoshio, Sta. 3’-2 (29°49.073’ N, 130°22.549’ E), 172–182 m, 21 Oct. 2016, N. Jimi, coll. [27 mm long, 4 mm wide]. Sulu Sea . Six specimens ( MNHN Musorstom 3-131), Philippines, Sta. 131 (11°37’ N, 121°46’ E), 111–113 m, 5 Jun. 1985 [7.5–

11.0 mm long, 1.0 mm wide]. Philippines. Nine specimens ( MNHN Musorstom 3-117), Timor Sea, R / V Coriolis, Sta. 117 (12°31’ S, 120°39’ E), 92–97 m, 3 Jun. 1985 [7.5–16.5 mm long, 1–2 mm wide] . One specimen ( MNHN Musorstom 3-121), Timor Sea, R / V Coriolis, Sta. 121 (12°08’ S, 121°17’ E), 73–84 m, 3 Jun. 1985 [15 mm long, 2 mm wide] . Five specimens ( MNHN Musorstom 3-131), Timor Sea, R / V Coriolis, Sta. 131 (11°37’ S, 121°43’ E), 120–122 m, 5 Jun. 1985 [10–15 mm long, 1 mm wide] . Two specimens ( MNHN Musorstom 3-134), R/ V Coriolis, Sta. 134 (12°01’ S, 121°57’ E), 92–95 m, 5 Jun. 1985 [17–18 mm long, 2.0– 2.5 mm wide] .

Description. Largest syntype (BMNH 1926.4.30.123–125) complete; body slightly wider medially, first four chaetigers with dark wide transverse band, interrupted by an irregular, barely paler intersegmental thin band ( Fig. 54A ); middle and posterior chaetigers without banding (probably faded out). Body 22 mm long, 2.5 mm wide, (without parapodia); pharynx exposed, previously cut transversely and laterally; left parapodium of chaetiger 8 and right parapodia of chaetigers 7 and 12 previously removed (some kept in container, unspecified), an irregular fracture of the body wall by chaetigers 12–13. Venter with a longitudinal middle pale area and two longitudinal darker bands along body.

Prostomium slightly wider than long, wider anteriorly, laterally constricted before anterior eyes, laterally expanded along eyes region ( Fig. 54A ). Lateral antennae with distinct ceratophores, slightly shorter than prostomium, longer than palps; palpophores slightly longer than palpostyles. Median antenna missing, inserted between anterior eyes.

Eyes round, barely pigmented, anterior eyes twice larger and more distant to each other than posterior eyes.

Nuchal organs lobes L-shaped, lateral branches markedly surpassing lateral prostomial margins; lateral ciliated bands visible dorsally ( Fig. 54A ). Longest tentacular cirri without tips, reaching chaetiger 6. Lateral cushions projected, bifid along first body half, entire along posterior one, longitudinal striae visible in some parapodia.

Peristomium with three dorsal tubercles, lateral ones projected anteriorly into 5 short lobes, middle one larger, more projected; ventrally with two triangular, blunt cones; papillae minute (visible under dorsolateral tubercles); lateral tubercles blunt, smaller than dorsolateral ones.

Pharynx fully exposed ( Fig. 54B ). Anterior margin smooth. Jaws hyaline, core brownish; upper jaw double, lower one transverse plate ( Fig. 54C, D ), exposed blades transparent, core brownish. Lateral vesicles present on both sides, globose (right one damaged by dissection). Middle ring corrugated, without papillae.

Dorsal tentacular cirri as long as body width (including parapodia). Chaetigers 1–4 without notochaetae; notochaetae present along chaetigers 5–16, first notaciular lobes minute, barely visible, notacicular lobes basally swollen, tapered, slightly capitate ( Fig. 54E , inset); notochaetae up to 20 per bundle, delicate, denticles fine. Neurochaetae about 20 per bundle, most blades missing, blades decreasing in size ventrally (and in posterior chaetigers), bidentate, 4–8 times longer than wide (3–4 times longer than wide in posterior chaetigers), guards approaching subdistal tooth ( Fig. 54E , insets).

Posterior region tapered into a truncate lobe. Prepygidial segment with dorsal cirri 3–4 times longer than ventral ones. Pygidium with anus terminal, anal cirri missing.

Oocytes grouped in a gonad fragment in a posterior chaetiger, each oocyte about 100 µm in diameter.

Variation. Syntypes (BMNH 1926.4.30.123–125) 13–16 mm long, 2–3 mm wide, 16 chaetigers; smallest one almost broken in two, larger one with transverse bands barely visible dorsally. Prostomium with lateral margins curved, wider anteriorly and in ocular region. Lateral antennae damaged; palpophores up to twice longer than palpostyles; median antenna present in one syntype, short, tapered, not reaching anterior prostomial margin, inserted between anterior eyes. Nuchal organs lateral branches reaching prostomial lateral margins or slightly surpassing them ( Fig. 55A, D ). Peristomium with three dorsal tubercles, lateral ones projected anteriorly into a blunt lobe; ventrally with two tubercles projected into a larger lobe ( Fig. 55B ). Upper jaw double ( Fig. 55C ), ventral one transverse plate, transparent margin eroded in some syntypes. Lateral vesicles visible in larger syntypes, blunt, damaged by dissection in two of them. Basal pharynx ring smooth. Notochaetae start in chaetiger 5.

Remarks. Paralamprophaea diplognatha ( Monro, 1926) n. comb. is newly combined because of the development of nuchal organs lobes and the type of pharynx armature. Further, P. diplognatha resembles P. leslieae n. sp. from Kiribati by having a similar pigmentation pattern, with transverse brownish entire (rarely indented) bands. The main differences between these two species is the shape of the dorsolateral peristomial tubercles, and the size of papillae in the basal pharynx ring. In P. diplognatha dorsolateral tubercles are anteriorly projected, and papillae are minute, whereas in P. leslieae the tubercles are semicircular, not projected, and papillae are large.

Some remarks about the wrong inclusion of this and other species as part of the HMS Alert Expedition by Monro (1926) were made for Paradalhousia papillosa (see above). Field data deserve improvement, but solving that is beyond my current objectives. Suffice it to say that the specimens from the Macclesfield Bank were collected in 1888 by the HMS Rambler, or in 1892 by the HM Surveying Vessel Penguin , but nothing can be assured about precise dates, localites or depths.

Distribution. South China Sea to the Philippines, in sediments, in 73–182 m depth.

Figures

FIGURE 1. Anterior end in dorsal view and exposed pharynx in frontal or oblique ventral view, rearranged after Pettibone (1970). A. Leocrates claparedii (Costa in Claparède, 1868), anterior end. B. Same, exposed pharynx. C. Leocrates oculatus (Treadwell, 1906), anterior end. D. Same, exposed pharynx. E. Leocrates diplognathus (Monro, 1926), anterior end. F. Same, exposed pharynx. G. Leocratides filamentosus Ehlers, 1908. H. Same, exposed pharynx. Scale bars: A, B: 0.4 mm, C, D, F: 0.8 mm, E: 0.3 mm, G, H: 1.0 mm (asterisk indicates nuchal organ; De: denticles; DJ: double jaw; DT: dorsolateral tubercles; LV: lateral vesicle, SJ: single jaw; TJ: transverse jaw) (Images produced by Marian Pettibone; reproduced with permission of the National Museum of Natural History, Smithsonian Institution).

FIGURE 2. A. Leocrates claparedii (Costa in Claparède, 1868), non-type specimens (USNM 5131), anterior end, dorsal view, pharynx everted. B. Another specimen, anterior end, dorsal view, pharynx fully everted. C. Same, pharynx and jaws, left lateral view (1: Pharynx ring I, 2: Pharynx ring II, AM: anterior margin, DT: dorsolateral tubercle, LJ: lower jaw, LV: lateral vesicle, Pe: peristomium, TB: tentacular belt, UJ: upper jaw). D. Lamprophaea poupini n. sp., holotype (UF 858), anterior end, right lateral view, after SAS (1–8: tentacular cirri, Ch: chaetiger, LA: lateral antenna, NO: nuchal organ lobe, Pa: palp, TB: tentacular belt). Scale bars: A, C: 0.5 mm, B: 0.7 mm, D: 0.3 mm.

FIGURE 16. Lamprophaea cuprea Grube, 1867, reinstated, lectotype (ZMH V-1275). A. Complete, dorsal view. B. Anterior region, dorsal view, SAS. C. Anterior region, ventral view. D. Chaetiger 7, left parapodium, anterior view, larger neuracicularemoved, MGS (*: chaetal blades for E). E. Superior longest and inferior shortest neurochaetal blades. Scale bars: A: 1.4 mm, B: 0.6 mm, C: 0.7 mm, D: mm, E left: 60 µm, E right: 35 µm.

FIGURE 54. Paralamprophaea diplognatha (Monro, 1926), new combination, syntypes (BMNH 1926.4.30.123–125). A. Largest syntype, anterior region, dorsal view (*: left lateral vesicle). B. Same, anterior end, left lateral view (LV: lateral vesicle). C. Another syntype, anterior region, ventral view (*: left lateral vesicle). D. Largest syntype, pharynx, frontal view. E. Same, chaetiger 7, right parapodium, anterior view (insets: notacicular lobe, neurochaetae with blade, blade of posterior chaetiger). Scale bars: A: 0.8 mm, B: 0.6 mm, C: 0.7 mm, D: 0.4 mm, E: 0.3 mm.

FIGURE 55. Paralamprophaea diplognatha (Monro, 1926), new combination, syntypes (BMNH 1926.4.30.123–125). A. Smallest syntype, anterior end, dorsal view. B. Same, left lateral view (DLT: dorsolateral tubercle, LT: lateral tubercle). C. Same, ventral view. D. Another syntype, anterior region, dorsal view (LV: lateral vesicle). Scale bars: A: 0.6 mm, B: 0.4 mm, C: 0.7 mm, D: 0.5 mm.