Megasyllis heterosetosa ( Hartmann-Schröder, 1991 ) Martín & Hutchings & Aguado, 2008

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 : 8-11

Megasyllis heterosetosa ( Hartmann-Schröder, 1991) , n. comb.

Figs 9A–F, 10A–E

Typosyllis (Typosyllis) heterosetosa Hartmann-Schröder, 1991: 30 , figs 30–35.

“ Typosyllis ” heterosetosa (sic) Licher 1999: 298, fig. 115.

Material examined. AUSTRALIA, NEW SOUTH WALES: Jervis Bay, Montagu Roadstead, 35° 02' 12" S, 150° 46' E, coll. P.A. Hutchings & party, 12 m, 3 Jun 1991, 1 ( AM W27573); off Cararma Creek, Hare Bay , 35° 00' 30" S, 150° 46' E, Posidonia , muddy sand, coll. NSW Fisheries, 18 Oct 1972, 1 ( AM W17558) .

Description. Body long, broad, cylindrical ( Fig. 9A), ventrally flattened; longest specimen 30 mm long, 1 mm wide, about 69 segments; yellowish, opaque in alcohol. Prostomium small, short, oval to bilobed, with two dorsal lobes or cheeks ( Fig. 9B); 4 small eyes in trapezoidal arrangement; antennae shorter than combined length of prostomium and palps, lateral antennae inserted on anterior margin, slightly shorter than median antenna ( Fig. 9B). Palps large, broad, divergent, basally fused, longer than prostomium, ventrally directed ( Fig. 9A). Peristomium similar in length to following segments; segments short, divided into 2–3 rings ( Fig. 9A, B). Tentacular cirri longer than antennae, dorsal ones slightly shorter than half peristomial width and longer than ventral ones ( Fig. 9A, B). Antennae, tentacular and dorsal cirri appearing smooth, unarticulated under low magnifications, under high magnification irregularly articulated, with indistinct articles ( Fig. 9C, D), more distinct on smaller specimens. Dorsal cirri inserted on cirrophores, alternating long inserted more dorsally, shorter than half body width) and short, about half length of long ones ( Fig. 9A–E); most posterior dorsal cirri all short ( Fig. 9E). Parapodial lobes short, triangular, with distinct prechaetal lobe; postchaetal lobes bilobed ( Fig. 9C, D). Ventral cirri digitiform, similar in length or slightly shorter than parapodial lobes. Compound falcigers heterogomph, with thick shafts, provided with subdistal spines on anterior and dorsal chaetae, other chaetae smooth with bidentate blades, with short, straight spines on margin, subdistal spines longest, distally directed, extending beyond proximal tooth ( Fig. 10 A–D); dorsal and anterior chaetae with both teeth similar, teeth becoming disimilar progressively along body and ventrally ( Fig. 10A–D); most posterior ventral chaetae with proximal tooth distinctly larger than distal tooth and distinctly curved blades, subdistal spines long ( Fig. 10D). Two kinds of chaetae per parapodium, most dorsal with elongated blades, 14 chaetae anteriorly ( Fig. 10A), progressively reducing to 2–4 on posterior parapodia ( Fig. 10C) and others with non-elongated falcigers, 16–18 on anterior ( Fig. 10B), 12 on posterior parapodia ( Fig. 10D). Non elongated falcigers with shorter and wider blades, dorsoventral gradation in length, changing from anterior (40 µm – 35 µm) to posterior (35 µm – 26 µm), respectively; blades more strongly bidentate, becoming shorter and wider within fascicle ventrally and on posterior chaetigers ( Fig. 10B, D). Dorsal capillary chaetae not seen (incomplete specimens); dorsal one distinctly slender, bidentate, smooth, according to Hartmann-Schröder (1991). Anterior aciculae 3–4, with short, slightly oblique tips ( Fig. 10E); posterior ones 1–2, straight, distally slightly oblique tips. Pharynx through about 6–7 segments; pharyngeal tooth on anterior margin, surrounded by crown of about 27 soft papillae ( Fig. 9F). Proventricle through 5–10 segments, with about 26–30 muscle cell rows.

Remarks. Originally described from Queensland (Hartmann–Schröder, 1991); this is the first record from NSW.

Habitat. Coralline and muddy sand, seagrasses; intertidal to shallow depths.

Distribution. Australia (New South Wales, Queensland).