Streblosoma bingarra Nogueira & Hutchings, 2007, sp. nov.

Streblosoma bingarra sp. nov.

(Figs. 2 D–F, 9–11)

Material examined. Type series. Holotype: AM W30721: coll. south of Dunwich, North Stradbroke Island, Moreton Bay, Queensland, 27°31.9'S 153°24.7'E, sand/mud flat at low tide, by P. Hutchings & K. Attwood, 9th November 2002, fixed in undiluted ethanol; posteriorly incomplete specimen, with 16 segments and measuring 17 mm in length, 3 mm maximum width at mid body.

Comparative material examined. Streblosoma acymatum Hutchings and Rainer, 1979: Type material: holotype: AM W78: coll. Port Jackson, Sydney, New South Wales, Australia, 33° 51' S, 151° 16' E; paratypes: AM W5107-5108: coll. just inshore of Charlotte Bay, Wallis Lake, New South Wales, Australia, 32° 20' " S 152° 33' " E; AM W5766: coll. Careel Bay, New South Wales, Australia, 33° 37' S, 151° 19' E, in Posidonia. Non-type material: AM W22428: 2 incomplete specimens, coll. Port Jackson, Sydney, New South Wales, Australia, 33° 51' S, 151° 16' E.

Description. Preserved body uniformly beige, without distinct patterns of pigmentation. Prostomium at base of upper lip; basal part of prostomium with 2 well separate irregular rows of small eyespots, basal row continuous across prostomium, eyespots well separated from each other mid dorsally, distal row close to distal part of prostomium, leaving wider mid dorsal gap; distal part of prostomium bearing numerous buccal tentacles (Figs 9 A–I; 10A). Peristomium restricted to lips, upper lip short, hood-like, broader than high; lower lip large, swollen, reaching posterior half of segment 2 (Fig. 9 A, C–D, F–I). Segment 1 dorsally and laterally large, ending laterally to expanded lower lip and partially fused to it (Fig. 9 A, D, F–I). Segment 2 with ventrolateral lobes as low flaps, shorter than length of segment, covering posterior part of segment 1 and terminating laterally to lower lip (Fig. 9 A, F). Ventral surface highly glandular between neuropodia, without discrete ventral shields, but markedly tessellated from segment 2 until end of fragment (Fig. 9 A, C–D, F–J).

Three pairs of branchiae, on segments 2–4, each with numerous independent filaments progressively tapering to tips. On segment 2, branchial filaments forming continuous transverse band of 2–3 rows across dorsum, those of anterior row inserted close to anterior margin of segment and extending laterally beyond level of notopodia, those of other rows inserted dorsally to first pair of notopodia (Figs 9 A–C, E–F, H–I; 10A– B). On segment 3, branchial filaments arranged in 2–3 rows, all originating posteriorly to notopodia and leaving narrow mid dorsal gap between filaments from left and right sides of pair (Figs 9 B, E; 10B). On segment 4, branchial filaments arranged as to form wider mid dorsal gap than on segment 3, few branchial filaments inserted posteriorly to notopodia and roughly vertically aligned to them, plus 3 rows of branchial filaments originating dorsally to notopodia and close to posterior border of segment (Fig. 9 B, E; 10C).

Notopodia extending until end of fragment; notopodia on segment 2 shorter than following ones, aligned dorsally to them and originating close to posterior border of segment, notopodia on segment 3 originating close to anterior border of segment (Figs. 9 C, H–I; 10B). Notochaetae graded in length within each tier (Fig. 2 F); chaetae of both tiers limbate, slightly geniculate capillaries, with limbation broader on one side, but narrower than width of shaft (Fig. 2 D–E); chaetae of anterior tier much shorter than those on posterior tier and with limbation starting from close to point at which chaetae emerge from body wall, chaetae of posterior tier with limbation restricted to distal third of chaetae.

Neuropodia inflated throughout (Fig. 9 A, C, F, H–J). Uncini with elongate base, dorsal button nearly terminal, prow reduced to short knob and main fang topped by single row of secondary teeth with 2–4 teeth, varying within torus (Fig. 11 A–D).

Nephridial papillae inserted between parapodial lobes on segments 4–7, papillae on segment 4 much shorter, those on segment 5 longer, digitate, those on segments 6 and 7 larger, spherical (Fig. 9 I).

Remarks. Streblosoma is well represented in Australian waters, with seven other species known so far for the area (Hutchings & Glasby 1990; Hutchings 1997a, b). A comprehensive table comparing most of those species was provided by Hutchings & Glasby (1990).

Of all those species, the only one with branchial filaments forming a continuous row on segment 2 is S. acymatum Hutchings and Rainier, 1979, which also shares with S. bingarra sp. nov., the presence of branchial filaments extending laterally from line of notopodia on segment 2 and the highly glandular ventral surface of anterior body. Streblosoma bingarra sp. nov., however, has remarkably large and swollen, cushion-like lower lip, reaching posterior part of segment 2 (Fig. 9 A, C–D, F–G), highly tessellated ventral surface of the body (Fig. 9 A, C–D, F–I), much more tessellated than in S. acymatum, and the branchial filaments clearly emerging directly from the body wall, while in S. acymatum they originate from characteristic raised glandular areas, which are evident in all specimens belonging to that species so far examined, independent on the state of preservation. Although all these characters could be dependent upon fixation until certain extension, the differences between S. bingarra sp. nov., and S. acymatum are so great, that we can confidently describe it as a new species.

Etymology. The specific name “ bingarra ” refers to an aboriginal word for tree bark (Endacott 1973) and refers to the tessellated ventrum of this species.