Streblosoma curvus, Hutchings, Pat, Nogueira, João Miguel Matos & Carrerette, Orlemir, 2015

Hutchings, Pat, Nogueira, João Miguel Matos & Carrerette, Orlemir, 2015, Telothelepodidae, Thelepodidae and Trichobranchidae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 240-274 : 247-249

Streblosoma curvus n. sp.

( Figs 1 A–C, 4, 5)

Type material. Holotype: AM W.47508, off Crystal Beach, Lizard Island, 14°40'S, 145°28'E, reef rock encrusted with brown algae and alcyonarians, 18 m, coll. P.B. Berents & P.A. Hutchings, 15 Jan 1975: incomplete specimen, in good state, 8 mm long, ~ 1.1 mm wide, 37 segments. Paratypes: AM W.44287, MI Qld. 2375, 18 mm in length, 1 mm in width, incomplete with 19 pairs of notopodia; AM W.47522, Lizard Island, channel bommies, 14°41'19"S, 145°27'50"E, 15 m, by SCUBA, incomplete specimen, in poor condition with 20 segments; AM W.47523, North Direction Island, 14°45'04"S, 145°30'45"E, coral rubble, 28 m, incomplete specimen, in relatively good state, with 24 segments, ~ 5 mm long, ~ 0.9 mm wide.

Other material examined. AM W.47524 (2), Lizard Island, north of Crystal Beach, 14°40'S, 145°28'E, live coral, 11 m, 14 Jan 1975, coll. Hutchings & Weate; AM W.47525 (4), between bommies inside lagoon entrance, 14°40'S, 145°28'E, sand, 18 m, 9 Oct 1978, coll. Jones & Short.

Description. Holotype incomplete, but well preserved. In life, uniformly reddish brown with pale tentacles and with conspicuous blood vessels visible through body wall ( Fig. 1 A–C). Transverse prostomium attached to dorsal surface of upper lip; basal part with eyespots irregularly arranged in thick, continuous row, thicker laterally, a fine line mid-dorsally ( Figs 1 B–C; 4B–E, G–J, L; 5A); distal part of prostomium low, restricted to base of upper lip. Long and relatively thick buccal tentacles. Peristomium forming lips and continuing dorsally; upper lip short, hood-like, about as long as wide; lower lip short, just around mouth, partially hidden by ventral lobe of segment 1 ( Fig. 4 A, C–D, F–H, J–L). Segment 1 narrow, with ventral lobe marginal to mouth; segment 2 with thickened anterior margin ventrally, as low crest across venter; segment 3 ventrally oblique, extending anteriorly and almost completely covering segment 2, with ventral crest higher than segment 2 ( Figs 4 A–L; 5A). Three pairs of branchiae, on segments 2–4, segment 2 with 3–4 filaments on either side, segments 3–4 with 2–3 filaments at each side; branchial filaments thin, originating anterior and dorsally to notopodia, progressively longer dorsally, longest filaments about 1/2–1/3 of corresponding body width ( Figs 1 B; 4B–E, G–J, L; 5A). Entire anterior ventral surface glandular, smooth between neuropodia; glandular surfaces progressively more swollen until segments 8–9, then progressively less inflated through segment 13, mid-ventral stripe visible from segment 13 to end of specimen ( Figs 4 A, C–D, F–H, J–L; 5D). Notopodia starting from segment 2 and extending until segment 32; cylindrical and bilobed notopodia, with rounded lobes of equal size; first pair about same size as following pairs and longitudinally aligned to them ( Figs 4 A–J, L; 5A–B). Narrowly-winged notochaetae throughout, wings broader on one margin, rounded; chaetae from posterior row with wings only on distal third to distal half of chaetae; anterior notopodia with chaetae of anterior row about 1/3 as long as those from posterior row, posterior notopodia with chaetae from anterior row only slightly shorter than those from posterior row ( Fig. 5 E–H). Neuropodia as swollen, fleshy pinnules slightly raised from the surface of the body throughout ( Figs 4 A, C–D, F–H, J–L; 5B–D). Uncini in straight rows until segment 19, segment 20 with dorsal edge slightly curved, with some uncini in the lower part of C-shaped line, more conspicuously curved from segment 21 until end of fragment, with more uncini in anterior end of tori (segment 21: 25 uncini at anterior end, 4 at curve and 11 at posterior end); on mid-body segments, uncini in roughly S-shaped arrangement, with second curve at ventral margin of posterior end of tori, and few uncini in a lower row ( Fig. 5 D, K); uncini with dorsal button at anterior third of base, short, conspicuous prow, curved base and crest with 2 rows of secondary teeth, 2 teeth in basal row and single, minute tooth in distal row, between teeth of basal row ( Fig. 5 I–K). Rounded and small, almost inconspicuous nephridial papillae on segments 4–7, opening dorsal and posteriorly to notopodia. Pygidium unknown.

Remarks. Only five previously known species of Streblosoma have neuropodia with uncini arranged in curved or looped rows, rather than in straight rows. These species are S. duplicata Hutchings, 1990 , S. hesslei Day, 1955 , S. porchatensis Nogueira, Garraffoni & Alves, 2004 , S. toddae Hutchings & Smith, 1997 , and S. uncinatus Kudenov, 1975 . The eight previously recorded species of Streblosoma from Australia all lack such an arrangement of uncini.

A comparative table for all these species was provided by Nogueira et al. (2004) and only one of them, S. duplicata , described from Hong Kong, shares with S. curvus n. sp. the branchial filaments of segment 2 not extending laterally to notopodia ( Hutchings 1990).

Streblosoma duplicata differs from S. curvus n. sp., as members of that species lack eyespots, uncini are arranged in completely closed loops from segment 14 onwards, and nephridial and genital papillae are inconspicuous or absent ( Hutchings 1990; Nogueira et al. 2004). In contrast, in S. curvus n. sp. eyespots are present across entire prostomium, uncini are arranged in curved rows, open on ventral edge of tori, from segments 20–21, and nephridial and genital papillae are small but conspicuous, present on segments 4–7.

Etymology. The specific name “ curvus ” is Latin for “bent” referring to the arrangement of the neuropodial uncini.

Habitat. Collected in amongst coral rubble in depths of 15– 28 m.

Type locality. Off Crystal Beach, 14°40'S, 145°28'E, Lizard Island, Great Barrier Reef, Queensland, Australia.

Distribution. Known only from Lizard Island and nearby North Direction Island.

Figures

FIGURE 1. Live specimens. A, Streblosoma curvus n. sp., AM W. 44276, MI QLD 2355; B – C. AM W. 44287, MI QLD 2375; D – F. Thelepus paiderotos n. sp., AM W. 44600, MI QLD 2397 (D – E), AM W. 44283, MI QLD 2368 (F); G – H. Terebellides akares n. sp., AM W. 45450, MI QLD 2445; I. Trichobranchus hirsutus n. sp., AM W. 45444, MI QLD 2444. Photos: A – I – A. Semenov.

FIGURE 4. Streblosoma curvus n. sp., holotype AM W. 47508. A – D. Entire incomplete worm, ventral, dorsal, right and left lateral views, respectively; E – H. Anterior end, dorsal, ventral, left and right lateral views, respectively; I – L. Close ups of anterior end, dorsal, left lateral, ventral and right lateral views, respectively. Abbreviations: numbers refer to segments, ll = lower lip, P = prostomium, ul = upper lip. Scale bars: A – D = 0.5 mm, E – H = 0.3 mm, I = 0.2 mm, J – L = 0.15 mm.

FIGURE 5. Streblosoma curvus n. sp., holotype AM W. 47508 (A – D), paratype AM W. 47522 (E – K). A. Close up of the anterior end, dorsal view; B. Mid-body segments; arrow begins to first neuropodium with uncini in curved row, on segment 21; C – D. Posterior end of fragment, right and left lateral views, respectively; E – F, Notochaetae from segment 4 under progressively higher magnifications; G – H. Notochaetae, segment 23, in progressively higher magnifications; I – K, Uncini from segment 7 under progressively higher magnifications and from segment 23, respectively. Abbreviations: numbers refer to segments, P = basal part of prostomium, ul = upper lip, * = distal part of prostomium. Scale bars: A – C = 0.2 mm, D = 0.3 mm, E, G = 40 Μm, F, H = 20 Μm, I, K = 10 Μm, J = 5 Μm.