Helmutneris vadum, Borisova & Budaeva, 2020

Borisova, Polina & Budaeva, Nataliya, 2020, Helmutneris vadum, a new species of Lumbrineridae (Annelida) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4877 (3), pp. 413-421 : 414-417

Helmutneris vadum n. sp.

( Figs 1 , 2 ; Appendix 1)

Type material. Holotype: AM W.43952 coral rubble, 14.694º S 145.466º E, 1–1.5 m, 14.08.2013, collected by: J.M. Nogueira, collecting method: by hand during snorkeling (incomplete wet specimen dissected dorsally at jaw region, DNA voucher) . Paratypes: AM W.44341(1 wet specimen); W.44399 (1 wet specimen, DNA voucher); W.46013 (4 wet specimens); W.46031 (1 wet specimen); W.46032 (3 wet specimens plus 1 on SEM stub, jaw apparatuses dissected from three specimens); W.46034 (1 wet specimen, jaw apparatus dissected); W.46035 (3 wet specimens plus 1 on SEM stub); W.46040 (3 wet specimens, jaw apparatus dissected from one specimen) (for details on paratype localities see Appendix 1) .

Other material examined. AM W.40740 (2), W.40742 (1, jaw apparatus dissected), W.40743 (1, jaw apparatus dissected), W.40849 (1, jaw apparatus dissected), W.40851 (1, jaw apparatus dissected), W.44150 (1), W.46019 (1, jaw apparatus dissected), W.46020 (1, jaw apparatus dissected), W.46021 (1), W.46023 (1), W.46033 (1, jaw apparatus dissected), W.46036 (2, jaw apparatus dissected from two specimens), W.46037 (1), W.46038 (1), W.46039 (1), W.46041 (1, jaw apparatus dissected), W.46042 (1, jaw apparatus dissected) (for details on localities see Appendix 1).

Diagnosis. Prostomium rounded, as long as wide. Prechaetal lobes inconspicuous, rounded, always shorter than postchaetal lobes; postchaetal lobes digitiform. Dorsal limbate chaetae present from chaetiger 1 to chaetiger 13–20. No ventral limbate chaetae. Simple multidentate hooded hooks on all chaetigers. MII as long as MI, pale with 6 (5–8) dark brown teeth of similar shape. MIII bidentate, with whitish central area, attachment lamella wide along whole posterior lateral edge. MIV with whitish central area, unidentate. Poorly sclerotized MV present in some specimens.

Description. Holotype (W.43952, DNA-voucher) incomplete with 126 chaetigers, L10= 1.9 mm, W10= 0.55 mm; single complete specimen (W.44150, non-type material) 15 mm long with 98 chaetigers (L10= 1.5 mm, W10= 0.45 mm); all other examined specimens incomplete anterior fragments; size variation in studied material: L10=1.68± 0.22 mm, W10=0.5± 0.07 mm. Preserved specimens whitish, without any distinct colour pattern ( Fig. 1 A–C).

Prostomium rounded, 0.33± 0.06 mm long, 0.32± 0.05 mm wide, without nuchal antennae, without eyes or visible eyespots ( Figs 1 B–C, 2A). Peristomium shorter than prostomium, 0.2± 0.05 mm long, consisting of two rings of similar size. All parapodia well developed, first 4–6 pairs of parapodia smaller than the following ones. Prechaetal lobes in anterior parapodia inconspicuous ( Fig. 2B ), in posterior parapodia small, rounded, always smaller than postchaetal lobes ( Fig. 2D ). Postchaetal lobes well developed in all parapodia, digitiform, with narrow base, always longer than prechaetal lobes, longer in anterior parapodia than in posterior ( Fig. 2 B–D).

Simple multidentate hooded hooks from chaetiger 1 to posterior end, with short hood and up to 10 teeth ( Fig. 2 E–G). Limbate chaetae from chaetiger 1 to chaetiger 13–20 (in smaller specimens to chaetiger 8), only dorsal limbate chaetae present ( Fig. 2B, C ). Usually anterior parapodia with 2–3 limbate chaetae and 2–3 simple multidentate hooded hooks. Aciculae yellow, up to two in anterior chaetigers and one in posterior ones. Pygidium with two anal cirri.

Mandibles translucent, with wide distal end narrowing posteriorly, fused up to 4/5 of length ( Fig. 1G ). Maxillary apparatus with four pairs of maxillae, small poorly sclerotizes MV present in some specimens. Carriers as long as MI or slightly shorter, brown. MI pale, forceps-like, without internal teeth, with attachment lamella ( Fig. 1D ). MII as long as MI, pale with 5–8 (usually 6, including holotype) dark brown teeth of similar shape; right and left maxillae in some specimens with different number of teeth (5+6, 7+8); with dark narrow (slightly narrower than MII) attachment lamella along 1/2–1/3 of posterior lateral edge ( Fig. 1E ). MIII with whitish central area close to triangular shape, clearly bidentate, with two teeth subequal in size, with wide attachment lamella along posterior lateral edge. MIV with whitish central area close to oval-triangular shape, unidentate, with wide oval dark attachment lamella ( Fig. 1F ). Several specimens (including holotype) with small pale poorly sclerotized MV .

Remarks. Helmutneris vadum n. sp. differs from the other species of the genus by having bidentate MIII with wide attachment lamella along whole posterior lateral edge and lacking ventral limbate chaetae while H. corallicola and H. flabellicola have unidentate MIII with attachment lamella along 1/4 of posterior lateral edge and dorsal and ventral limbate chaetae ( Table 1 ).

Etymology. The species epithet refers to Latin vadum meaning “shallow water”. Unlike its congeners, this species was reported from shallow depths, from one to twelve meters.

Type locality. Australia, Queensland, Lizard Island, south of lagoon entrance, reef near Bird Islet , 14.694° S, 145.466° E .

Distribution and habitat. This species is only known from Lizard Island, depth range 1– 12 m. The species, although often reported from the old coral reef rocks, did not show association with a particular species of corals, and was also reported from fine sediments.

Genetic information. The 16S rDNA and COI fragments were sequenced for two specimens: W.43952 (holotype) and W.44399 (paratype). Sequences are deposited in GenBank under accession numbers MT 763200 – MT 763203 .

Figures

FIGURE 1. Helmutneris vadum n. sp. A. Holotype AM W.43952, general view; B. the same, anterior part, ventral view; C. the same, dorsal view; D. Paratype W.46032, maxillary apparatus, dorsal view; E. W.40849, maxilla II, dorsal view; F, the same, maxillae III and IV, dorsal view; G. W.46042, mandibles. Abbreviations: MI—maxilla I, MII—maxilla II, MIII—maxilla III, MIV—maxilla IV, al—attachment lamella, C—maxillary carriers.

FIGURE 2. Helmutneris vadum n. sp. Paratype W.46035. A. Anterior part, ventral view; B. Parapodium 1; C. Parapodia 14– 15; D. Parapodia 31–32; E. Simple multidentate hooded hook, parapodium 12; F. Simple multidentate hooded hook, parapodium 17. G. The same, enlarged. Abbreviations: psl—postchaetal lobe.