Vrijenhoekia timoharai, Georgieva & Wiklund & Ramos & Neal & Glasby & Gunton, 2023

Georgieva, Magdalena N., Wiklund, Helena, Ramos, Dino A., Neal, Lenka, Glasby, Christopher J. & Gunton, Laetitia M., 2023, The Annelid Community of a Natural Deep-sea Whale Fall off Eastern Australia, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 167-213 : 182

Vrijenhoekia timoharai sp. nov.

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Fig. 13

Vrijenhoekia ketea species complex Gunton et al., 2021: 51–52 , fig. 12F

Holotype: AMW.53702, IN2017_ V03 _100; 9 June 2017; off Byron Bay , NSW, Australia, beam trawl, start: 28.05°S 154.08°E, 999 m, end: 28.10°S 154.08°E, 1013 m . Paratype: AMW.52204, samelocalityas holotype. DNA vouchers: AMW.53702 ( COI, 16S, 18S) , AMW.52204 ( COI, 16S) .

Description. Body ofAMW.53702 complete, approximately 2.3 mm wide (including parapodia but not chaetae) and 7.5 mm long, with 32 segments ( Fig. 13A ). Body stout with tapered pygidium. Ethanol-preserved specimen pale yellow.

Prostomium ( Fig. 13B ) rectangular, considerably wider than long, with no posterior incision discernible. Palps biarticulated with palpophores thickerthan palpostyles, but a similarlengthto palpostyles. Pairedantennaesimilarinlength to palps, tapered, with antennophores not discernible. Eyes absent, median antenna verysmallrelative to othersobserved for genus, facial tuberclewith bulbous endandapproximately halflengthof antennae. Nuchal organssmalland notdorsally extended. Everted proboscis ( Fig. 13C ) lacking papillae.

Parapodia triangular and stout ( Fig. 13D ), with long, tapering and terminally rounded dorsal cirri slightly longer than width of body, longest in segments 1 to 5. Cirrophores distinct and small. Ventral cirri similar throughout length of body, distinctly tapered, same length as parapodia, inserted subterminally, with cirrophores indistinct. Notochaetae absent, neurochaetae begin on segment 1, with at least two aciculae per neuropodium. Neurochaetae numerous (at least 50), compound, with blades finely serrated on one side ( Fig. 13E ). Median and dorsal blades appearing longer than ventral blades. Pygidial cirri and papillae either absent or not observed ( Fig. 13F ).

Distribution. IN2017_V03, Station 100. Pilot whale carcass, off Byron Bay, New South Wales, Australia in 999–1013 m.

Etymology. The species is named in honour of Dr Tim O’Hara of Museums Victoria, Australia, the Chief Scientist of the “Sampling the Abyss” voyage, for enabling the deep-sea discoveries herein.

Remarks. Our phylogenetic analysis ( Fig. 12 ) resolves IN2017_V03 Vrijenhoekia timoharai sp. nov. as being a new Vrijenhoekia species, most closely related to Vrijenhoekia ahabi Summers, Pleijel, & Rouse, 2015 (pp 1.0), described from a whale fall in Monterey Canyon off California at 2893 m depth, from which it demonstrates an uncorrected COI geneticdistance of 6% (Table S15). In general, forthe genus, V. timoharai sp. nov. shows 6–19% distance to all other Vrijenhoekia species while a genetic distance of 0.8% was observedbetweenthetwoindividuals sequenced. Vrijenhoekia timoharai sp. nov. hasthe shallowestdistributionin thisgenus to date (all others were collected at ~ 2890 m depth), being closest to that of an undescribed Vrijenhoekia species from the Guaymas Basin reported from 1562 m ( Summers et al., 2015). According to the species authors, it is not possible to distinguish the three Vrijenhoekia species V. ahabi , V. ketea Summers, Pleijel, & Rouse, 2015 and V. falenothiras Summers, Pleijel, & Rouse, 2015 morphologically, despite significant genetic differences between them. IN2017_V03 V. timoharai sp. nov. is larger than V. ahabi , being closer in size to V. ketea but not as large as Vrijenhoekia balaenophila Pleijel, Rouse, Ruta, Wiklund, & Nygren, 2008 . Incomparison to V. ahabi , V. ketea , and V. falenothiras , V. timoharai sp. nov. has a distinctly bulbous facial tubercle that distinguishes it from the former species, as well as less elongated parapodia and slightly longer dorsal cirri.

Figures

Figure 12. Phylogeny for the Hesionidae, Microphthalmidae and Chrysopetalidae families based on Bayesian analysis of a combined dataset of the genes COI, 16S and 18S. Numbers adjacent to nodes indicate posterior probabilities, and taxa for which sequences have been contributed by the present study are indicated in bold.

Figure 13. Vrijenhoekia timoharai sp. nov. holotype AM W.53702. (A) Ethanol-preserved entire specimen (prostomium features have been outlined in grey for clarity), scale bar is 1 mm; (B) dorsal view of prostomium stained with Shirlastain, scale bar is 500 µm; (C) ventral view of partially everted pharynx stained with Shirlastain, scale bar is 1 mm; (D) parapodium, scale bar is 200 µm; (E) neurochaetae, scale bar is 30 µm; (F) dorsal view of pygidium, scale bar is 500 µm. Abbreviations: a, antennae; ft, facial tubercle; ma, median antennae; no, nuchal organ; pp, palpophore; ps, palpostyle; dc, dorsal cirri; dcp, dorsal cirriphore; nra, neuroacicula; vc, ventral cirri; chb, chaetal blade; chs, chaetal shaft.