Terebellides akares, 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 : 261-266

Terebellides akares n. sp.

( Figs 1 G–H, 12–16)

Type material. Holotype: NTM W. 023143, Lizard Island, S end of Coconut Beach, reef flat, 14°41'42.120"S, 145°28'11.280"E, coll. C. Glasby, 5 Apr 2008, CReefs, complete, 7 mm long, 1 mm wide, with 45 segments. Paratypes: NTM W.025894 (2, 1 mounted on SEM pin), both complete, 10 mm long, 1.5 mm wide, 45 segments, gravid; 5 mm long, 1.0 mm wide, 37 segments; AM W.45831, MI QLD 2441 (1 mounted on 2 SEM pins); AM W.47596, CReefs, intertidal, mounted on SEM pin.

Other material examined. AM W.47624, MI QLD 2205, South of Mermaid Cove, 14°38'53"S, 145°27'E, coarse coral rubble, 14.5 m, 1 Sep 2010, CReefs, LI–10–047, complete, small, 34 segments; AM W.47625, Lizard Island, MacGillivray Reef, 14°38'51"S, 145°29'16"E, coral rubble, 7–16 m, 3 Sep 2010, CReefs, LI–10–062, complete, 40–41 segments, 7 mm long, ~ 1.5 mm maximum width (segs 11–12); AM W.47626, MI QLD 2244, High Rock, 14°49'34"S, 145°33'08"E, coral rubble, 20 m, 11 Sep 2010, CReefs, LI–10–134, very small specimen, in poor state of preservation, with ~40 segments; AM W.44168, MI QLD 2359; AM W.44573, MI QLD 2406.

Description. In life with reddish body and dark red branchiae, with well developed vascular system, buccal tentacles colourless ( Fig. 1 G–H). Transverse prostomium attached to dorsal surface of upper lip; basal part without eyespots; distal part extending along dorsal margin of upper lip until near anterior margin. Buccal tentacles of two types, short tentacles uniformly cylindrical, slightly expanded at tips, long tentacles more expanded at tips, foliaceous ( Figs 12 A–M; 14A–G, K; 15A–B; 16A–E, H). Peristomium forming lips, continuing dorsally as narrow annulation; upper lip large, longer than wide, convoluted; lower lip developed, projecting forwards, with laterally rounded nearly straight distally marginal lobe ( Figs 12 B–G, I–M; 14K; 15A–B; 16B–C, E). Anterior segments, until segment 10, with thickened anterior margins lateral and ventrally, forming low lobes as short collars across ventrum covering posterior part of preceeding segment, lobes progressively shorter from segment 3; segment 1 short, conspicuous dorsally, much shorter than following segments, more developed laterally and ventrally, below expanded lower lip, with almost inconspicuous ventral collar; segment 2 dorsally thin, with main stem of branchiae, more developed laterally and ventrally; segment 3 dorsally fused to segment 2, more developed ventrally, as protruding crest, at an angle with anterior segments; following segments aligned with segment 4 ( Figs 1 G–H; 12A–M; 12A–M; 14A–B, K–L; 15A–B; 16B–C, E). Single 5-lobed lamellate branchia, lamellae on both sides with several rows of cilia and distal row of scattered papillae ciliated at tips; posterior pair of lobes much shorter, completely free ( Figs 1 H; 12A–M; 14A, C–D, G–J; 15A–B; 16A–B, D, F, H–J). Notopodia beginning from segment 3, first two pairs shorter than following ones, especially first one ( Figs 12 A–M; 14A–D, G, K–L; 15A–B, D–E, H–I; 16A–E); narrowly-winged notochaetae in both rows, wings barely visible under light microscopy, visible as short and fine hairs under SEM, those of chaetae of posterior row only present on distal half of chaetae; chaetae of anterior row about 2/3 length of those of posterior row ( Figs 13 A–D; 15D–I). Neuropodia beginning from segment 7, sessile, chaetae emerging directly from body wall. Neurochaetae of first 1–2 segments as thin, distally tapered acicular spines subdistally bent at right angle, those of first pair (segment 7) shorter and with bayonet-like tip ( Figs 13 E–F; 15H–I, L); following neuropodia with acicular uncini with 4 rows of secondary teeth until end of notopodia; abdominal neuropodia as foliaceous pinnules, bearing avicular uncini with 3–4 rows of secondary teeth; relatively few uncini per torus throughout ( Figs 13 G–M; 14A–B, K–L; 15A–C, H–N; 16B, G). Remarkably short abdomen, with compact segments, about 1/3–1/4 of extension of region with notopodia ( Figs 12 A–D, N–O; 14A–B; 15C). Nephridial papillae on segment 3, genital papillae on segments 6–7, not always conspicuous ( Figs 15 D; 16C). Pygidium smooth to slightly crenulate ( Figs 12 A–D, N–O; 15C).

Variation. Some specimens, such as paratype AM W.45831, examined under SEM, have a single pair of neuropodia bearing acicular spines, on segment 8, instead of two pairs, on segments 7 and 8. Those specimens are otherwise similar to animals with acicular spines on segments 7 and 8, and so we consider this as a variable character in T. akares n. sp. In addition, in specimens with two pairs of neuropodia with acicular spines, those of the first pair are always much shorter than spines from the second pair, indicating that they may be so small as to be difficult to see under the SEM, as they do not protrude from the body wall.

Remarks. According to Parapar & Hutchings (2014), there is another species of Terebellides having two pairs of neuropodia with spines, on segments 7 and 8, T. bigeniculatus Parapar, Moreira & Helgason, 2013 . Terebellides bigeniculatus differs from T. akares n. sp. by having branchial lamellae distally smooth, lacking papillae (visible under light microscopy); neuropodial spines of segments 7 and 8 similar to each other, bent at right angle and gently tapering; abdominal neuropodia as rounded pinnules, with uncini originating all around and separated from each other by deep grooves; and smaller nephridial and genital papillae of segments 6–7. In contrast, branchial lamellae of T. akares n. sp. have a distal row of scattered papillae on both sides; neuropodial spines of segment 7 are bayonet-like chaetae and those of segment 8 are bent at right angle and gently tapering; and abdominal neuropodia are wider than long, with uncini only on top, with shallower grooves in between.

Currently five species are recorded from Australia and none from the Great Barrier Reef. Of these, only T. narribri Hutchings & Peart, 2000 and T. woolawa Hutchings & Peart, 2000 have five branchial lobes, all the others have four pairs. Terebellides akares n. sp. can be distinguished from T. woolawa that has all branchial lobes similar in size in contrast to our new species where the posterior pair is much shorter. Terebellides narribri has only the first pair of notopodia reduced, in contrast, our new species has the first two pairs much shorter and with short chaetae, whereas in T. narribri it is only the podia which are reduced, not the length of the chaetae. Both these previously described Australian species only have the first pair of neuropodia with acicular chaetae, whereas T. akares n. sp. has the first two pairs of neuropodia with such chaetae.

Etymology. The specific name “ akares ” refers to the distinctly short abdomen, with compacted segments, from the Greek word “ akares ”, meaning short.

Habitat. In amongst coral rubble in the intertidal zone.

Type locality. Reef flat at south end of Coconut Beach, 14°41'42"S, 145°28'11”E, Lizard Island, Great Barrier Reef, Queensland, Australia.

Distribution. Known only from Lizard Island and 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 12. Terebellides akares n. sp., holotype NTM W. 023143. A – D. Entire worm, right dorso-lateral, right and left laterals, and ventral view, respectively; E – H. Anterior end, ventral, left and right laterals, and right dorso-lateral views; I – M. Close ups of anterior end, left and right lateral, each in two progressively closer views, and ventral view, respectively, unspecified arrow in J points to nephridial papilla, arrows in M point to neuropodia; N – O. Posterior end, right and left lateral views, respectively. Abbreviations: numbers refer to segments, ll = lower lip, ul = upper lip. Scale bars: A – D = 0.7 mm, E – F, H – I, K, N – O = 0.3 mm, G = 0.5 mm, J, L – M = 0.2 mm.

FIGURE 13. Terebellides akares n. sp., AM W. 44168. A – D. Notochaetae, segments 8 and 16, respectively, both under progressively higher magnifications; E – F. Neuropodial spines, segments 7 and 8, respectively; G – I. Uncini, segment 15, under progressively higher magnifications; J – L. Uncini, segment 22, under lower and higher magnifications; M. Uncini, segment 33. Scale bars: A, C = 50 Μm, B, E – F, H, J = 20 Μm, D, G = 30 Μm, I, M = 10 Μm, K – L = 5 Μm.

FIGURE 15. Terebellides akares n. sp., paratype NTM W. 025894. A – B. Progressively closer views of anterior end, left lateral view; C. Posterior end, right lateral view; D. Notopodia, segments 5 – 10, arrows point to genital papillae of segments 6 – 7; E – G. Notochaetae, segment 7, in progressively closer views; H – I. Neuropodia, segments 7 – 8, from right and left sides of body; J. Neuropodium, segment 22; K. Uncini, segment 22; L. Neuropodial spines, segment 7; M. Uncini, segment 13; N. Uncini, segment 22. Scale bars: A = 300 Μm, B = 200 Μm, C – D = 100 Μm, E, H = 50 Μm, F = 20 Μm, G, J = 10 Μm, I = 40 Μm, K, M = 5 Μm, L = 6 Μm, N = 2 Μm.