New species and records of the genus Syllis Savigny in Lamarck, 1818 (Annelida: Syllidae) from Socotra Archipelago (Indian Ocean) Author Rodríguez, Yolanda Lucas Author Martín, Guillermo San Author Fiege, Dieter text Zootaxa 2020 2020-02-19 4742 1 73 88 journal article 10.11646/zootaxa.4742.1.4 bea08b82-f1da-4fca-987f-820360af0e8f 1175-5326 3674479 D2AA5CB8-118B-4E1B-9646-F23CA492118A Syllis qamhiyn n.sp. Figures 2–6 urn:lsid:zoobank.org:act: A270D267-0901-4185-80E4-E6D0AAC48A49 Material examined. Holotype ( SMF 26713) Soc /ST–726, Ras Qataninh Bay , 12º21.293’N 53º32.659’E , under stones and coral rubble, 8–10 m , coll. T. Wehe 9.4.2000 . 1 paratype , same collection data ( NHCY 0018 ); 1 paratype prepared for SEM, Soc/ST–725, Ras Qataninh Bay , dredge, 12º21.789’N 53º31.399’E to 12º21.780’N 53º31.390’E , 18–20 m , coll. T. Wehe 09.04.2000 , ( SMF 26714, SEM-stub 1311). Diagnosis. Conspicuously thick and short dorsal cirri filled with gelatinous substance; reduced number of compound chaetae from midbody to posterior parapodia, with enlarged shafts and short blades, which become almost unidentate; blades not fused to shafts. FIGURE 2. Syllis qamhiyn n.sp. , holotype (SMF 26713); A, anterior end, dorsal view; B, midbody segments, dorsal view; C, posterior body segments, dorsal view; D, midbody parapodium. A, B and C same scale bar. Description. Holotype complete specimen, 17.5 mm long, 0.69 mm wide, with 151 chaetigers ( Fig. 2A ). One incomplete paratype with 134 chaetigers, and other complete, Paratype (SMF 26714), 18.5 mm long, 0,5 mm wide, with 160 chaetigers ( Fig. 4B ). Body long and slender, filiform, without colour pattern ( Figs 2A, B, C ; 4B ). Prostomium semicircular to oval ( Figs 2A ; 5A ); four small eyes in trapezoidal arrangement. Palps similar in length to prostomium. Median antenna arising between anterior eyes, with 12–13 articles, shorter than combined length of prostomium and palps. Lateral antennae same length as median antenna, with 13 articles each ( Fig. 2A ). Peristomium dorsally shorter than subsequent segments ( Figs. 2A ; 5B ). Dorsal tentacular cirri about 15–21 articles each; ventral tentacular cirri about 13–14 articles each. Dorsal parapodial cirri relatively thin on anterior segments, alternating relatively long ( 0.3 mm ) and short ( 0.2 mm ); longer cirri similar in length to body width at corresponding chaetiger, with about 17–19 articles, shorter ones about 7–11 articles each ( Fig. 2A ); from midbody posteriorwards, dorsal cirri shorter than body width, each cirrus thicker in midlength, with about eight well-marked articles, with acute article distally ( Fig. 2 A–D); most articles of these dorsal cirri filled with gelatinous substance ( Fig. 2D ), articles covered by small pores ( Fig. 5F ). Ventral cirri oval, shorter than parapodial lobes ( Figs 2D ; 6D ). Ventral area of parapodia with almost circular area of pores ( Fig. 6 C–E) and internal gland ( Fig. 2D ). Compound chaetae as heterogomph falcigers; anterior parapodia with about 10 falcigers each; falcigers with slender bidentate blades, proximal tooth distinctly shorter than distal one, and short spines on margin; blades with dorsoventral gradation in length, 42–20 μm long ( Figs 3A ; 5C, D ). Number of chaetae per parapodium progressively diminishing posteriorly, 4–5 in midbody ( Figs 3C ; 5E, G, H ) and 3–5 on mid-posterior and posterior parapodia ( Figs 3E ; 6 A–B), shafts becoming larger and blades shorter and minutely bidentate, with proximal tooth much smaller than distal one ( Fig. 3E ). Midbody falcigers with blades 20–19 μm long, posterior body falcigers with blades similar, about 19 μm long. Dorsal and ventral simple chaetae not seen. Anterior parapodia with five slender aciculae each, distally rounded ( Fig. 3B ), three in midbody parapodia ( Fig. 3D ); posterior parapodia with two distally oblique aciculae each ( Fig. 3F ). Pharynx long, extending through about 13 segments ( Figs 2A ; 4B ); pharyngeal tooth elongated, conical, acute, on anterior margin of pharynx ( Figs 2A , 4A ). Proventricle shorter than pharynx, through 9–10 segments ( Fig. 2A ), with about 48–50 muscle cell bands. Pygidium small, with two anal cirri, with 7–8 articles each ( Fig. 6F ). FIGURE 3. Syllis qamhiyn n.sp. , holotype (SMF 26713); A, falcigers, anterior body; B, aciculae, anterior body; C, falcigers, midbody; D, aciculae, midbody; E, falcigers, posterior body; F, aciculae, posterior body. FIGURE 4. Syllis qamhiyn n.sp. , paratype (SMF 26714), before preparation for SEM; A, anterior margin of pharynx, showing pharyngeal tooth; B, complete specimen, dorsal view. FIGURE 5. Syllis qamhiyn n.sp. , paratype (SMF 26714), SEM; A, prostomium, dorsal view; B, prostomium and peristomium, dorsal view; C, falcigers, anterior body; D, falcigers and partial view of dorsal cirri, anterior body; E, midbody segments, dorsal view; F, dorsal cirrus, midbody; G, dorsal cirri, midbody; H, falcigers, midbody. FIGURE 6. Syllis qamhiyn n.sp. , paratype (SMF 26714), SEM; A, posterior body segments, dorsal view; B, falcigers, posterior body; C, circular area of pores, ventral view; D, base of parapodium, ventral view – longer arrow pointing to ventral cirrus, shorter arrow pointing to circular area of pores; E, ventral pores, detail – arrows pointing to pores; F, pygidium and anal cirri, ventral view. Etymology. The name of the species refers to Dendrosicyos socotrana , the only species of Cucurbitaceae growing into tree form and original from Socotra Island . Its trunk resembles the shape of midbody cirri of S. qamhiyn n.sp. In soqotri language it is named qamhiyn . Remarks. Syllis qamhiyn n.sp. is characterized by having short, thick, distally acute dorsal cirri on midbody and posterior parapodia, and reduced number of falcigers in these parapodia, with enlarged shafts and short, almost unidentate blades, not fused to shafts. Syllis qamhiyn n.sp. belongs to the same group of species of Syllis armillaris (O. F. Müller, 1771 ) and related species, the latter considered cosmopolitan but likely a species complex. The mid- and posterior body falcigers of Syllis armillaris also have almost unidentate blades, but they are not so short and the shafts are not as enlarged as in Syllis qamhiyn n.sp. ( San Martín 2003 ); furthermore, the mid- and posterior body dorsal cirri of Syllis armillaris are enlarged, but not so much as in Syllis qamhiyn n.sp. Similar differences are between Syllis qamhiyn n.sp. and S. pseudoarmillaris Nogueira & San Martín, 2002 from Brazil ( Nogueira & San Martín 2002 ); S. pseudoarmillaris has fewer number of articles on midbody dorsal cirri and the compound chaetae of these parapodia are clearly bidentate, with not enlarged shafts; furthermore, the pharynx and proventricle are longer in S. qamhiyn n.sp. Syllis gracilis Grube, 1840 , also considered a cosmopolitan species, and S. picta (Kinberg, 1886) , from the Indo-Pacific (including the Red Sea), have similar bodies, with enlarged mid- and posterior body dorsal cirri, but in these species at least one of the compound chaetae on these parapodia have fused blade and shaft ( San Martín 2003 ; Álvarez-Campos et al . 2015 ; 2017). Habitat. Under stones and coral rubble from 8– 20 m . Distribution. Only known from Socotra Archipelago. Type locality. Ras Qataninh Bay , Socotra Island .