Leocrates rousei, 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 : 70-71

Leocrates rousei n. sp.

Fig. 40

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Type material. Western Pacific. Papua New Guinea. Holotype (SIO A5973), Bismarck Sea , Kimbe Bay, Rest Orff Island, Sta. 8 (05°17’35.58” S, 150°06’15.4202” E), 5–10 m, dead Acropora with brittle stars, Breviturma (olim Ophiocoma) pica ( Müller & Troschel, 1842), 23 Apr. 2008, F. Pleijel, coll.

Description. Holotype (SIO A5973), complete, distorted ( Fig. 40A ), bent laterally after a lateral dissection of right parapodia of chaetigers 5–7, and posterior region bent dorsally; left parapodia of chaetigers 7 and 9 removed for observing parapodial features. Body 10 mm long, 1.8 mm wide (by chaetiger 4); prostomium and dorsum brownish, trunk pigmentation as about 12 transverse thin lines per segment; venter with two longitudinal brownish bands; many cirri on site, anterior ones banded.

Prostomium slightly longer than wide, slightly wider in anterior eyes region ( Fig. 40B ). Dorsal surface with a thin, pale ‘M’ with basal tynes divergent, directed to posterior eyes, connected to an inverted truncate pentagonal area, two larger tear-drop pale areas, narrowing anteriorly, ahead of anterior eyes, and two smaller pale areas before lateral ceratophores. Lateral antennae shorter than prostomium, slightly longer than palps, bent laterally with welldefined ceratophores; palpophores 2–3 times longer than palpostyles. Median antenna directed posteriorly, short (not reaching anterior prostomial margin if bent anteriorly), inserted between posterior eyes.

Eyes reddish; anterior eyes each 1 / 4 prostomial width, emarginate anteriorly, twice larger than posterior ones, barely more distant to each other than posterior, round eyes; in lateral view anterior and posterior eyes fused.

Nuchal organs lobes horizontal C-shaped, slightly projected posteriorly, semicircular, prostomial posterior projections with similar pigmentation as prostomium, ciliateds bands pale; lateral ciliated bands not visible. Tentacular cirri long, some feebly banded, blackish bands thinner than pale ones, longest one reaching chaetiger 10. Lateral cushions low, many distorted, entire, longitudinal striae visible.

Pharynx invaginated, observed by a slight dissection to avoid further damage. Anterior margin smooth; jaws single, upper one visible, hyaline, lower one not seen.

Dorsal cirri longer than body width (including parapodia). Chaetigers 1–4 without notochaetae. Notacicular lobes tapered; neuracicular lobes blunt, slightly longer than wide ( Fig. 40C , inset). Notochaetae present along chaetigers 5–16, scarce (about 30 per bundle), subdistally denticulate, denticles fine. Neurochaetae about 30 per bundle, blades decreasing in size ventrally, 3–15 times longer than wide; blades bidentate, guard approaching subdistal tooth ( Fig. 40D ).

Posterior region tapered, distorted ( Fig. 40E ), retaining pigmentation pattern. Prepygidial segment with dorsal cirri 2–3 times longer than ventral ones, both damaged. Pygidium with anus retracted, terminal, anal cirri missing.

Gonads not seen, probably a juvenile.

Etymology. The specific epithet is to honor Dr. Gregory Rouse, University of California, San Diego, Scripps Institution of Oceanography, in recognition of his many contributions to polychaetes systematics, and by his longstanding support of my research activities. The species-group name is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Remarks. Leocrates rousei n. sp. belongs in the group of species with large eyes, and with notacicular lobes tapered with entire tips. However, L. rousei is unique by having reddish to purple eyes (others have brown or black eyes), and a pigmentation pattern over prostomium and dorsum which is unique among all species in the genus.

Distribution. Only known from a single locality in Papua New Guinea, in dead coral fragments, in 10 m water depth.

Figures

FIGURE 40. Leocrates rousei n. sp., holotype (SIO A5973).A. Complete, dorsal view, posterior region bent dorsally, depressed by glass slide. B. Anterior end, dorsal view. C. Chaetiger 7, left parapodium, anterior view, MGS (inset: notacicular lobe). D. Same, neurochaetae (insets: longer and shorter blades). E. Posterior region, depressed by glass slide, dorsal view. Scale bars: A: 1 mm, B: 0.4 mm, C: 0.3 mm, D: 120 µm, E: 0.9 mm.