Dalhousia indica Salazar-Vallejo 2020, n. comb.
Creators: name: Salazar-Vallejo, Sergio I.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Phyllodocida
Hesionidae
Dalhousia
Dalhousia indica

description: Dalhousia indica (Horst, 1921) n. comb., reinst.
Figs 11, 12
Leocrates indicus Horst, 1921: 82–83; 1924: 195–196, Pl. 36, Fig. 13.
Leocrates atlanticus: Pettibone 1970: 222, Fig. 21 (non McIntosh, 1885).
Type material. Indonesia. Holotype (ZMA V.Pol. 2481), Sulawesi, Banda Sea, R / V Siboga Exped., Sta. 221 (06°24’ S, 124°39’ E), 2798 m, deep sea trawl, muddy bottom, 4 Nov. 1899.
Additional material. Wallis and Futuna. Two specimens (MNHN Musorstom 7-631), Sta. 631 (11°54.0’ S, 179°31.6’ W), 600 m, 29 May 1992 [21–22 mm long, 3 mm wide]. New Caledonia. One specimen (MNHN Halipro 2-04), R/V Tangaroa, Sta. 4 (23°30.90’ S, 169°33.93’ E to 23°30.74’ S, 169°33.66’ E), 790–845 m, 6 Nov. 1996 [8 mm long, 1 mm wide]. Two specimens (MNHN Halipro 2-25), R/V Tangaroa, Sta. 25 (25°16.64’ S, 170°23.69’ E to 25°17.45’ S, 170°23.93’ E), 1100–1380 m, 11 Nov. 1996 [30–33 mm long, 3–5 mm wide]. One specimen (MNHN Halipro 2-60), R/V Tangaroa, Sta. 60 (24°52.06’ S, 168°42.31’ E to 24°52.11’ S, 168°43.68’ E), 1133–1280 m, 18 Nov. 1996 [27 mm long, 3 mm wide]. One specimen (MNHN Halipro 2-83), R/V Tangaroa, Sta. 83 (23°38.95’ S, 168°15.79’ E to 23°38.54’ S, 168°15.80’ E), 820–1060 m, 22 Nov. 1996 [27 mm long, 4 mm wide].
Description. Holotype (ZMA V.Pol. 2481) complete, straight, integument, damaged (Fig. 11A), without pygidium; posterior chaetigers almost broken off, damaged after several previous manipulations and dissections. Two pin perforations middorsally by chaetigers 6 and 7/8; left parapodia of chaetigers 1, 2, 6, 7, 13, and right parapodium of chaetiger 6 previously removed; two irregular ventral dissections along chaetigers 1–6/7 (Fig. 11C). Body 17 mm long, 2 mm wide, 16 chaetigers; dorsum colorless, venter with brownish margins along midventral depression, interrupted segmentally.
Prostomium as long as wide, slightly wider anteriorly and posteriorly (Fig. 11B). Lateral antennae with ceratophores distinct, slightly shorter than prostomium, longer than palps; palpophores twice longer than palpostyles. Eyes brownish, barely defined. Median antenna broken, inserted centrally between eyes.
Eyes brownish, anterior left eye reniform, right one round, larger and more distant to each other than posterior round ones (illustrated as round by Pettibone).
Nuchal organs lobes as long as wide, parallel, slightly expanded posteriorly, well separated, barely pigmented in holotype, darker in non-type specimens. Tentacular cirri missing. Lateral cushions low, barely projected, entire, longitudinal striae visible.
Peristomial dorsolateral and ventrolateral tubercles low, barely projected. Pharynx not exposed, inner features observed by previous dissection (Fig. 11C). Anterior margin smooth. Upper jaw double, delicate, small; lower jaw not visible, probably damaged by dissection.
Chaetigers 1–3 without notochaetae; following parapodia biramous, notochaetae present along chaetigers 4–16, about 40 per bundle, reaching neurochaetal tips, delicate, tips curled, subdistally denticulate, denticles fine. Notacicular lobes tapered, blunt in anterior (Fig. 11D) and posterior chaetigers (Fig. 11F). Neuracicular lobes round, blunt, barely projected in anterior chatigers (Fig. 11D), blunt, conical in posterior chaetigers (Fig. 11F). Neurochaetae about 20 per bundle (30 in posterior segments), blades bidentate, 6–50 times longer than wide (Fig. 11E, G), in middle chaetigers blades slightly narrower than handle width, or 1 / 3 – 1 / 5 as wide as handle’s width, longest thin blades subdistally expanded, denticles tiny, guards approaching subdistal tooth.
Posterior region tapered. Prepygidial segment and pygidum missing.
Oocytes not seen.
Variation. Body size 8–33 mm long; neurochaetal blade length smaller in larger specimens. Body dorsum, nuchal organs and neurochaetal pigmentation variable; usually darker in larger specimens; dorsal cirrophores and neuropodia paler. Best preserved specimen (Fig. 12A) with brownish pigmentation dorsally, progressively paler medially and posteriorly. Nuchal organs depressed, medially darker, expanded laterally (Fig. 12B). Peristomial middorsal and dorsolateral tubercles darker, ventrolateral tubercles paler (Fig. 12C). Notacicular and neuracicular lobes blunt, tapered (Fig. 12D); neurochaetae golden to brownish, blades 10-20 times longer than wide (Fig. 12E, insets).
Remarks. Dalhousia indica (Horst, 1921) was included as a junior synonym of D. atlantica McIntosh, 1885 by Pettibone (1970) and Pleijel (1998: 160). They are different species because D. indica has nuchal organs lobes as long as wide and its eyes are brownish, anterior ones twice larger than posterior ones, whereas in D. atlantica nuchal organs lobes are slightly longer than wide, and eyes are blackish, anterior ones 2–3 times larger than posterior ones. Consequently, D. indica is reinstated. It has been newly combined into Dalhousia because of the development of the nuchal organs, being posteriorly expanded, and by the large size of notochaetae which reach neurochaetal tips in the same parapodia.
The brownish pigmentation of neurochaetae has faded off in the type specimen, which is a damaged juvenile, but in more recently collected specimens, neurochaetal handles and at least the basal to middle part of blades are brownish, and even notochaetal bases are brownish as well, as indicated in the original description.
Distribution. Originally described from the Banda Sea, Indonesia in deep water (2798 m), it has been found in Wallis and Futuna, and New Caledonia, in sediments at depths of 600–1380 m.
description: Published as part of Salazar-Vallejo, Sergio I., 2020, Revision of Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 (Annelida, Errantia, Hesionidae), pp. 1-114 in Zootaxa 4739 (1) on pages 25-28, DOI: 10.11646/zootaxa.4739.1.1, http://zenodo.org/record/3672547