Loimia pseudotriloba, Nogueira, João Miguel Matos, Hutchings, Pat & Carrerette, Orlemir, 2015

Nogueira, João Miguel Matos, Hutchings, Pat & Carrerette, Orlemir, 2015, Terebellidae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 484-576 : 561-567

Loimia pseudotriloba n. sp.

( Figs 3 A–C, 51–54)

Type material. Holotype: AM W.47810, MI QLD 2336, complete, 25 mm long, 3 mm wide. Paratypes: AM W.47736 (4), CReefs, LI–10–018, MI QLD 2193, Mermaid Cove (buoy), 14°38'46"S, 145°27'13"E, complete specimen, with 86 segments, 31 mm long, 3.5 mm wide, in good state of preservation; AM W.47737, CReefs, LI– 10–004, MI QLD 2185, channel bommies, 14°41'19"S, 145°27'50"E, complete specimen in 2 pieces, anterior 17 mm long, 3 mm wide, 18 mm long, 2 mm wide; AM W.44594, MI QLD 2393, mounted on SEM pin.

Comparative material examined. Holotype of Loimia batilla Hutchings & Glasby, 1988 , AM W.5162. Paratypes of Loimia batilla , AM W.7097, AM W.7098; AM W.7106, AM W.7107. Non-types of Loimia ingens ( Grube, 1878) , NTM W.6764, NTM W.6775, NTM W.17330. Holotype of Loimia ochracea ( Grube, 1878) , ZMB 906, MPW 583. Holotype of Loimia triloba Hutchings & Glasby, 1988 , BMNH ZB 1986.97.

Description. In life, body anteriorly yellow with reddish mid-ventral shields, green after termination of notopodia, speckled with large dark spots (probably internal contents) ( Fig. 3 A–C). Transverse prostomium attached to dorsal surface of upper lip; basal part without eyespots, distal part shelf-like ( Fig. 52 A, H). Peristomium forming lips, hood-like upper lip, short, almost circular, partially covered by lobes of segment 1; short and swollen lower lip, button-like ( Figs 51 C, H–K; 52A–E, H–K). Segment 1 dorsally narrow, with pair of large lobes directed anteriorly and reaching around mid-length of upper lip; lobes almost circular, dorsal margins inserted at level of first pair of notopodia, laterally to first pair of branchiae; lobes higher laterally, at level of neuropodia, midventrally indented to partially expose lower lip. Segment 2 reduced, dorsally conspicuous, covered by lobes of segment 3 laterally and fused to it ventrally. Segment 3 with pair of elongate and distally rounded lobes, almost triangular, with narrow bases tapering to distally rounded tips, reaching beyond tips of lobes of segment 1; base with ventral edges fused to upper corners of first mid-ventral shield, at mid-length of anterior neuropodial tori, dorsal margins inserted at level of dorsal edges of neuropodia; lobes of segment 4 shorter than lobes of segment 3, rectangular, longer than wide, laterally straight and distally rounded, with distinctly narrow bases, ventral margins inserted at upper corners of second mid-ventral shield, dorsal margins at level of mid-length of anterior neuropodial tori, aligned to ventral margins of lobes of segment 3 ( Figs 51 A–K; 52A–E, H–K). Anterior segments slightly inflated dorsally. Paired dorso-lateral arborescent branchiae present on segments 2–4, dorsal to line of notopodia, with short branchial filaments branching dichotomously from secondary stems originating in a spiral from short basal stems; first pair slightly longer, about half body width at segment 2; pairs all longitudinally aligned ( Figs 51 A–B, D–G, J–K; 52A–B, D–E, H, J–K). Trapezoidal mid-ventral shields present on segments 2–15, those of segments 2–3 completely fused into single crenulated structure, following shields progressively smoother, slightly crenulate until last; blood red region on segments 12–15; first 2 shields, on segments 2–3 and 4, much wider than those of following segments, then about same width, indented posteriorly by tori, last shield almost inconspicuous ( Figs 51 A, C, H–K; 52C, I). Dorsum smooth throughout, rows of rounded tubercles absent. Notopodia beginning on segment 4, extending until segment 20; notopodia short, cylindrical to oblong, notopodia of segments 4–7 inserted progressively more laterally, then longitudinally aligned ( Figs 51 A–K; 52A–K). Narrowly-winged notochaetae in both rows throughout, those from anterior row finely serrated under SEM, chaetae of posterior row with wings at distal half ( Figs 53 E–J; 54F–H). Neuropodia present from segment 5, as low, almost sessile ridges until termination of notopodia, as elongate and thin, rectangular pinnules, from segment 21, inserted progressively more ventrally, lateral to mid-ventral groove on posterior segments ( Figs 51 A–C, F–K; 52B–E, G, I–K; 53A, D). Pectinate short-handled avicular uncini, arranged in partially intercalated to completely separate double rows, in back to back arrangement, from segment 11 until termination of notopodia, on segment 20; uncini with short base, dorsal button at mid-length of base, rounded prow, and crest with single vertical series of 5–6 progressively shorter secondary teeth throughout; main fang larger but not clearly defined, line of teeth aligned with tip of prow; under SEM, series of teeth with lateral fringe of tiny teeth ( Figs 53 K–M; 54A–E, I–L). Nephridial papillae on segments 3 and 4, between dorsal margins of lobes and bases of branchiae, genital papillae on segments 6–8, posterior to notopodia; all papillae minute ( Fig. 52 A–B, D–F, H). Pygidium with digitiform papillae ( Figs 51 A–B; 53A–C). Tube mucous, with small stones and shell fragments embedded.

Remarks. The only other known Australian species of Loimia with lobes also on segment 4 are L. triloba Hutching & Glasby, 1988 and L. juani n. sp., this latter species also found in Lizard Island and described above. These species differ from L. pseudotriloba n. sp., however, because L. juani n. sp. has lobes of segment 1 almost reaching the tip of the upper lip and with dorsal margins inserted at the level of branchiae; lobes of segment 3 almost circular and not reaching the tips of lobes of segment 1, with dorsal margins inserted at mid-length of neuropodial tori; and lobes of segment 4 with dorsal margins reaching the level of notopodia. In contrast, in L. pseudotriloba n. sp. the lobes of segment 1 do not reach beyond mid-length of upper lip and the dorsal margins are inserted at the level of notopodia, laterally to branchiae; lobes of segment 3 are almost triangular, with narrow bases and elongate tips, reaching beyond the tips of the lobes of segment 1 and inserted dorsally at the level of the dorsal edges of neuropodia; while the dorsal margins of the lobes of segment 4 are fused to the body wall at midlength of anterior neuropodial tori. In addition, L. juani n. sp. has mid-ventral shields extending to segment 13, while in L. pseudotriloba n. sp. the mid-ventral shields extend to segment 15, and the uncini of L. juani n. sp. have distally pointed prow, with ligaments continuing downwards, while in L. pseudotriloba n. sp., the uncinial prow is rounded. However the most striking differences between members of these species are easily seen in the different body colour patterns of live specimens (compare Fig. 3 A–C and D–F).

The other Australian species with lobes on segment 4 besides L. juani n. sp., described above, L. triloba , differs from L. pseudotriloba n. sp. because in that species prostomial eyespots are present laterally and all lobes are shorter, those of segment 1 not reaching mid-length of the upper lip; lobes of segment 3 rectangular, not reaching mid-length of lobes of segment 1 and with bases extending from the level of mid-length of the neuropodial tori to the level of notopodia (see Carrerette & Nogueira 2015).

Etymology. We name this species as “ pseudotriloba ” due to the similarities with L. triloba , both species having lobes on segment 4.

Type locality. Big Vicki's reef, 14°41'10"S, 145°26'32"E, Lizard Island, GBR, Australia.

Distribution. Widely distributed along Lizard Island region.

Figures

FIGURE 3. Live specimens. A – C. Loimia pseudotriloba n. sp. AM W. 47810, MI QLD 2336; D – F. Loimia juani n. sp.; D. AM W. 44261, MI QLD 2335; E. AM W. 44518, MI QLD 2381; F. AM W. 44263, MI QLD 2336; G – I. Lanice viridis n. sp. AM W. 44611, MI QLD 2400. Photos: A – I—Alexander Semenov.

FIGURE 51. Loimia pseudotriloba n. sp. AM W. 47810: A – B. Entire worm, left and right lateral views, respectively; C. Thorax, ventral view; D – K. Progressively higher magnifications of the anterior end, dorsal, right lateral, ventral and left lateral views, respectively. Numbers refer to segments. Abbreviations: ll = lower lip, ul = upper lip. Scale bars: A – C = 1 mm, D – E, G, I, K = 0.5 mm, F = 0.6 mm, H, J = 0.8 mm.

FIGURE 52. Loimia pseudotriloba n. sp. AM W. 44594: A – E. Anterior end, dorsal, left lateral, ventral and right lateral (2) views, respectively; F. Close up of the notopodia of segments 5 – 9, arrows point to genital papillae; G. Transition between anterior and posterior body; H – K. Close ups of the anterior end, dorsal, ventral, right and left lateral views, respectively. Numbers refer to segments. Abbreviations: ll = lower lip, ul = upper lip. Scale bars: A, C = 700 µm, B, H = 500 µm, D = 800 µm, E = 400 µm, F, J – K = 200 µm, G = 600 µm, I = 300 µm.

FIGURE 53. Loimia pseudotriloba n. sp. AM W. 44594: A – C. Posterior end in progressively higher magnifications, left ventrolateral, frontal and dorsal views, respectively; D. Posterior body, ventro-lateral view; E, H – J. Notochaetae of segment 17; F – G. Notochaetae of segment 5 under increasing magnifications; K – L. Uncini of segment 16 under different magnifications; M. Uncini, segment 9. Scale bars: A = 400 µm, B = 200 µm, C = 100 µm, D = 7 µm, E = 50 µm, F = 20 µm, G = 5 µm, H = 40 µm, I = 6 µm, J, M = 10 µm, K = 3 µm, L = 4 µm.