Opisthosyllis viridis Langerhans, 1879

Martín, Guillermo San, Hutchings, Pat & Aguado, María Teresa, 2008, Syllinae (Polychaeta, Syllidae) from Australia. Part. 2. Genera Inermosyllis, Megasyllis n. gen., Opisthosyllis, and Trypanosyllis, Zootaxa 1840, pp. 1-53 : 35-38

Opisthosyllis viridis Langerhans, 1879

Figs 26E, F, 27A–G, 28A–F, 29A, B

Opisthosyllis viridis Langerhans, 1879: 543 , pl. 31, fig. 9.- Monro 1939: 390, text–fig. 301.- Imajima 1966b: 224, fig. 39.- Núñez et al. 1992: 115.- López & San Martín 1994: 130, fig. 1.- Lee & Rho 1994: 135, fig. 3.

Opisthosyllis australis Augener, 1913 (in part): 218, pl. 3, fig. 35, text-fig. 28 a–d.-Day & Hutchings 1978: 102.- Hartmann-Schröder 1979: 85; 1980: 47; 1981: 24; 1991: 26.

Opisthosyllis papillosa Hartmann-Schröder, 1960: 87 , figs. 59–62; 1965: 108, figs. 33–35; 1980: 48; 1981: 24; 1991: 26.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberleys, Long Reef , 13° 58'S, 125° 38'E, 25 m, coll. P.A. Hutchings, 17 Jul 1988 , 2 on SEM stub ( AM W31429); East Montalivet Island , 15° 06'S , 125°

18'E, 6 m, coll. P.A. Hutchings, 16 Jul 1988, 3 ( AM W31377); Exmouth Gulf, Bundegi Reef, N end of beach, 21° 49'S, 114° 11'E, 2 m, rocky rubble with sediment, brown alga with epiphytic growth, coll. H.E. Stoddart, 4 Jan 1984, 1 ( AM W31380), 8 ( AM W31378), 1 ( AM W31374); SE end of Long Island, 28° 28' 48"S, 113° 46' 30"E, 8 m, dead coral substrate, covered in coralline algae, coll. P.A. Hutchings, 22 May, 1994, 2 ( AM W31379); off S end of Long Island, Beacon Island, 28° 28' 48"S, 113° 46' 18"E, 5 m, dead coral substrate, covered in coralline algae, coll. P.A. Hutchings, 25 May 1994, 2 ( AM W31376); N end of Long Island, Goss Passage, 28° 28' 18"S, 113° 46' 18"E, 8 m, dead coral substrate, coralline algae, boring bivalves, coll. C. Bryce, 22 May 1994, 1 ( AM W31372); E side of West Wallabi Island, 28° 27' 54"S, 113° 40' 54"E, 1.5 m, in Posidonia root mat, plus epifauna, coll. P.A. Hutchings, 26 May 1994, 1 ( AM W31371); Goss Passage, Beacon Island, 28° 25' 30"S, 113° 47'E, 8 m, dead plates of Acropora sp. , covered in coralline algae, coll. P.A. Hutchings, 19 May 1994, 2 ( AM W31373); Vancouver Peninsula, Albany, 35° 04'S, 117° 56'E, weed mat, coll. H.E. Stoddart, 13 Dec 1983, 6 ( AM W27570). TASMAN SEA: Reef flat near "Yoshin Maru Iwaki" wreck, Elizabeth Reef, 29° 55' 48"S, 159° 01' 18"E, intertidal, from small heads of Acropora valida , Pocillopora damicornis, Elizabeth & Middleton Reefs Expedition, 1987 , coll. J.K. Lowry & R.T. Springthorpe, 14 Dec 1987, 3 ( AM W31375). QUEENSLAND: Lizard Island, off Chinaman's Head, 14° 41'S, 145° 27'E, 7 m, reef rock, P.A. Hutchings, 28 Jul 1977, 1 on SEM ( AM W194824).

Additional material. Red Sea; Schab Anbar, Ghadarqa, Pocillopora , 1.5 m, 4 paratypes (HZM P–14718) of Opisthosyllis papillosa . Opisthosyllis australis , AUSTRALIA: WESTERN AUSTRALIA, Shark Bay, 3 syntypes (HZM V–7947); Freemantle, 2 syntypes (HZM V–5308, 5309). Opisthosyllis papillosa Mahé, Anse Forbans, Seychelles, Indian Ocean, 1 ( SMF 11289) 1 ( SMF 11288) coll. Böggemann & Hessling, 1 ( SMF 11290) coll W. Westheide.

Description. Longest specimen examined 7 mm long, 0.4 mm wide, 76 chaetigers. Body proportionally long, tapered posteriorly, without coloured margins, provided with numerous, apparently rounded papillae, usually scarce anteriorly ( Fig. 27A), more numerous from proventricle to posterior end; with 3–4 lobes ( Fig. 28B–D). Prostomium oval ( Figs 26E, F, 27A); 4 eyes in open trapezoidal arrangement. Palps elongated, longer than length of prostomium. Median antenna arising from middle of prostomium, with about 34 articles, longer than combined length of prostomium and palps; 1/3 longer than lateral ones, with 21 articles, inserted on anterior margin of prostomium ( Figs 26E, F, 27A). Peristomium shorter than subsequent segments. Dorsal tentacular cirri slightly longer than median antenna, with about 35 articles twice longer than ventral tentacular ones. Dorsal cirri all longer than body width ( Figs 26E, 27A), with distinct basal cirrophore, alternating in length and number of articles, most anterior longer than dorsal tentacular cirri, with up to 50–55 articles. Parapodia conical, dorsally bilobed ( Figs 27A, 28A), each lobe ending with distinct papilla. Ventral cirri digitiform, shorter than parapodial lobes. Compound chaetae heterogomph, with bidentate blades, margin with short spines; proximal tooth small, especially on posterior chaetae ( Figs 27B, D, 28E, F, 29A, B), becoming almost unidentate on most posterior parapodia ( Fig. 27D). Marked dorsoventral and anteroposterior gradation, most anterior elongate with slender shafts ( Fig. 27B), becoming thicker posteriorly, with shorter and larger blades ( Figs 27D, 28E, F, 29A, B). Anterior parapodia with about 12 compound chaetae, reducing posteriorly to 6–7. Anterior aciculae distally blunt, 2–4 ( Fig. 27C), decreasing gradually posteriorly to 2, 1 in most posterior parapodia ( Fig. 27E). Pharynx from chaetiger 2–3 to 9–10; pharyngeal tooth on chaetiger 8–9 ( Fig. 27A). Proventricle through 8 segments, with about 32 muscle cell rows.

Remarks. Opisthosyllis viridis seems a very variable species; specimens from the same area may vary in relative length of short and long cirri and shape of papillae (from rounded to rough with minute crests). Specimens from Mahé (as Opisthosyllis papillosa ) have long cirri and rough papillae, but those from Coiba Island ( Panamá) have short cirri and rough papillae ( Capa 2003); and those from Cape Verde Islands have rounded papillae and short cirri ( López & San Martín 1994). In all cases, both the aciculae and compound chaetae are identical, the latter strongly bidentate blades on posterior parapodia on small specimens, and teeth less developed on larger specimens. Another papillated species is Opisthosyllis leslieharrisae Aguado, San Martín & Nygren, 2005 , which differs from O. viridis in chaetal structure and colour pattern ( Aguado et al. 2005). A detailed revision of Opisthosyllis viridis including molecular studies is needed to confirm whether all these correspond to a single species or to a complex of sibling species.

Habitat. Among dead corals, seagrasses, algae, rubble and sediment; intertidal and shallow waters.

Distribution. Circumtropical, Australia (Western Australia, New South Wales, Queensland).