Trichobranchus hirsutus, 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 : 268

Trichobranchus hirsutus n. sp.

( Figs 1 I, 17–20)

Type material. Holotype: AM W.44608, MI QLD 2399, complete, in excellent state, 6 mm long, 0.6 mm maximum width. Paratypes: AM W.47510, MI QLD 2441, mounted on SEM pin; AM W.44610, MI QLD 2399; AM W.44624, MI QLD 2413; AM W.44946, MI QLD 2410 (13, plus1 mounted on microscope slide); AM W. 45142, MI QLD 2440 (7); AM W.45143, MI QLD 2440 (3); AM W.45147, MI QLD 2441 (2); AM W.45439, MI QLD 2441; AM W.45444, MI QLD 2444.

Description. Minute worms. In life with transparent body wall, base of branchiae bright red with well developed vascular system, buccal tentacles colourless ( Fig. 1 I). Transverse prostomium attached to dorsal surface of upper lip; basal part with large eyespots laterally; distal part low, poorly developed, at base of upper lip ( Figs 17 B, D–E, G, I–J; 18A, C). Deeply grooved buccal tentacles, in two thicknesses; under SEM, buccal tentacles highly ciliated on inner surface, annulated on outer side, with longitudinal track of cilia on each side ( Figs 17 A–B, D–E, G–J; 18A–C; 19A–K). Peristomium forming lips; short, circular upper lip, as long as wide; short lower lip, continuing to form a pair of large flaring lobes terminating dorso-laterally ( Figs 17 A–B, D–E, G– J; 18A–C; 19A–B, D–G, I, K). Segments 1–5 with progressively shorter lateral lobes, lobes triangular, distally rounded; anterior segments, until termination of notopodia, with thickened anterior margins laterally and ventrally, forming low lobes as short collars across ventrum covering posterior part of preceeding segment; segment 1 inconspicuous dorsally, with large eversible ventral process; anterior margins of segments 2–5 thickened dorsally, as raised crests, more developed on segments 2–3 ( Figs 17 A–B, D–E, G–J; 18A–C; 19A–I, L). Two pairs of branchiae, on segments 2–3, each pair with single long and thick filament on either side; filaments annulated and heavily ciliated, second pair originating slightly laterally to first pair ( Figs 17 B, D–E, G, I–J; 18A, C; 19B–D, F–H, K). Notopodia beginning from segment 6; narrowly-winged notochaetae on both rows, wings as short and fine hairs under SEM, chaetae in anterior row ~1/3 as long as those from posterior row ( Figs 18 D–G; 19M; 20A–C). Neuropodia beginning from segment 6, totally sessile on thorax, uncini emerging directly from body wall, as foliaceous pinnules with well separated uncini on abdomen; few uncini per torus, ~10 until termination of notopodia, 10–15 on anterior abdominal segments, 6–8 posteriorly; neurochaetae as acicular uncini with four rows of minute secondary teeth and subrostral beard until end of notopodia ( Figs 18 H; 20F–I); abdominal uncini avicular, with four rows of secondary teeth ( Figs 18 I–J; 20J–L). Nephridial papilla absent; from segment 3, all segments with tuft of cilia between noto- and neuropodia, or corresponding position on segments 3–5 and after notopodia terminate, cilia longer on abdomen ( Figs 19 B, D, F–G, M; 20A, D, J). Bilobed pygidium, heavily ciliated ( Figs 17 A–F; 19B, D; 20D–E).

Remarks. Prior to this study ten species of Trichobranchus were known, of which five have two pairs of branchiae, a character shared with our new species, T. hirsutus n. sp. The major diagnostic characters are given in Table 4 of Hutchings & Peart (2000) and previously two species, T. bunnabus Hutchings & Peart, 2000 and T. gooreekis Hutchings & Peart, 2000 , were known from Australia. Of these Australian species only T. bunnabus , which is only known from southern Australia, has two pairs of branchiae. Trichobranchus hirsutus n. sp. is a tiny species, much smaller than most species in this genus, including both previously known species from Australia, and it can easily be distinguished from T. bunnabus by the well developed triangular lateral lobes on segments 1–5, while in the latter species only the distal margins of the segments 2–4 are thickened. However, several species of Trichobranchus are poorly described as evident in Table 4 ( Hutchings & Peart 2000), with some characters not being scored. This is the first record of the genus from the Lizard Island region.

Etymology. The specific name “ hirsutus ” is Latin and refers to the hairy buccal tentacles, branchiae and pygidium, and scattered tufts of cilia throughout body.

Habitat. Occurs in amongst coral rubble on intertidal reef flat.

Type locality. Coconut Beach, 14°40'52"S, 145°28'12"E, Lizard Island, Great Barrier Reef, Queensland, Australia.

Distribution. Known only from Lizard 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 17. Trichobranchus hirsutus n. sp., holotype AM W. 44608. A – B, D – E. Entire worm, ventral, left lateral and two right lateral views, respectively; C, F. Posterior end, right dorso-lateral and ventral views, respectively; G – I. Anterior end, left lateral, ventral and right lateral views, respectively; J. Close up of anterior end, right dorso-lateral view, numbers refer to segments. Scale bars: A – G, I = 0.2 mm, H, J = 0.15 mm.

FIGURE 18. Trichobranchus hirsutus n. sp., holotype AM W. 44608 (A – C), paratype AM W. 44946 (D – J). A – C. Close ups of anterior end, right dorso-lateral, ventral and left lateral views, respectively; D. Parapodia, segments 20 – 22; E – G. Notochaetae, segment 17, general and chaetae from anterior and posterior rows, under higher magnifications; H – J. Uncini, segments 16, 24 – 25 and 25 under higher magnification, respectively. Abbreviations: numbers refer to segments, ll = lower lip, P = prostomium, Pe = peristomial lobe, ul = upper lip. Scale bars: A – C = 200 Μm, D = 50 Μm, E = 40 Μm, F = 30 Μm, G, I = 20 Μm, H = 10 Μm, J = 5 Μm.

FIGURE 19. Trichobranchus hirsutus n. sp., paratype AM W. 47510. A – D. Entire worm, ventral, left lateral, dorsal and right lateral views, respectively; E – H. Anterior end, ventral, right and left lateral, and dorsal views, respectively; I. Close up of anterior end, ventral view; J – M. Close ups of some tentacles, origin of branchiae, oral area, and segments 3 – 6, left lateral view, respectively. Abbreviations: numbers refer to segments, ll = lower lip, Pe = peristomial lobe, ul = upper lip. Scale bars: A – D = 200 µm, E – I = 100 µm, J – K = 30 µm, L = 40 µm, M = 20 µm.