The Annelid Community of a Natural Deep-sea Whale Fall off Eastern Australia

. In the deep ocean, whale falls (deceased whales that sink to the seafloor) act as a boost of productivity in this otherwise generally food-limited setting, nourishing organisms from sharks to microbes during the various stages of their decomposition. Annelid worms are habitual colonizers of whale falls, with new species regularly reported from these settings and their systematics helping to resolve biogeographic patterns among deep-sea organic fall environments. During a 2017 expedition of the Australian research vessel RV Investigator to sample bathyal to abyssal communities off Australia’s east coast, a natural whale fall was opportunistically trawled at ~1000 m depth. In this study, we provide detailed taxonomic descriptions of the annelids associated with this whale-fall community, using both morphological and molecular techniques. From this material we describe nine new species from five families (Dorvilleidae: Ophryotrocha dahlgreni sp. nov. Ophryotrocha hanneloreae sp. nov., Ophryotrocha ravarae sp. nov.; Hesionidae


Introduction
Whales that sink and settle on the seafloor upon their death, known as whale falls, represent an important food source in the generally food-limited deep sea, as well as having a crucial role as dispersal and evolutionary stepping stones for deep-sea fauna (Smith & Baco, 2003;Smith et al., 2015Smith et al., , 1989. As a carcass decomposes it eventually becomes a chemosynthetic habitat, and during its decomposition is colonized by different successional stages of organisms, some of which are highly specialized for life on decaying vertebrate remains. Perhaps the most notable whale-fall specialists are annelids of the genus Osedax (Siboglinidae), also known as "zombie" worms, which embed "root" tissue into decaying vertebrate bones and feed by using bacterial endosymbionts to extract organic compounds from the bones. Annelid taxa are the most abundant and diverse component of whale-fall communities in general (Smith et al., 2015), with families such as Ampharetidae, Dorvilleidae and Hesionidae  being commonly encountered within these habitats.
Since the first observations in a manned submersible of an intact whale skeleton off southern California in 1987 (Smith et al., 1989), several natural whale falls have been opportunistically encountered during remotely operated vehicle (ROV), submersible and trawl deployments, while further understanding of whale-fall communities has been greatly aided by the experimental sinking of cetacean remains (e.g., Smith et al., 2015;Fujiwara et al., 2007;Dahlgren et al., 2006). Both types of whale fall are poorly represented in the western Pacific, and especially around South-East Asia and in Australian waters. From near Australian waters, a whale skull was recovered at 880 m northeast off Chatham Island with new species of gastropod (Marshall, 1987), Sipuncula (Gibbs, 1987), and a bivalve (Dell, 1987(Dell, , 1995. Whale bones with associated molluscs were collected from various other locations off New Zealand including the Chatham Rise at depths of 372-379 m, 587 m, 900 m and 937-955 m, Chatham Islands at 1242 m depth, Banks Peninsula at 844 m and Challenger Plateau at 908-912 m and 1116-1120 m (Marshall, 1994;Dell, 1995). More recently, two new species of Osedax have been reported from a whale skull at 390 m depth on the Pukaki Rise (Berman, 2022), which are the first records of this genus from New Zealand. Further north off the coast of Japan, whale-fall communities are known from a natural whale fall at 4000 m at the Torishima Seamount (Wada et al., 1994) as well as a number of whale carcasses sunk off southern Japan at 219-254 m (Fujiwara et al., 2007). The above studies reported Amphioxiformes, a number of rare species, as well as the unusual presence of protodrilid polychaetes in association with the whale bones.
During a voyage of the RV Investigator (IN2017_V03) to sample bathyal and abyssal zones off the eastern coast of Australia, a natural whale fall was collected during beam trawl sampling in the Byron Bay area ( Fig. 1; Gunton et al., 2021;O'Hara et al., 2020). This study documents in detail the annelid fauna colonizing the first whale fall reported from Australian waters and compares this community with other known whale falls from the Pacific Ocean, as well as whale falls from the Atlantic and Southern Oceans.

Sample collection
The natural whale fall was recovered as part of a 4-metre beam trawl deployment during RV Investigator voyage IN2017_V03 "Sampling the Abyss". The trawl (operation 100) was conducted on 9 June 2017 in the Byron Bay area (start 28.05°S 154.08°E; end 28.10°S 154.08°E), at 999-1013 m depth (Fig. 1). The whale fall consisted of a complete skull and several vertebrae of a pilot whale (Globicephala macrorhynchus), with no remaining soft tissue ( Fig. 2A-D). Upon recovery, the whale bones were temporarily placed in chilled seawater and inspected for associated invertebrates. A subset of the associated annelids was photographed alive, then subsequently preserved in 80% or 95% ethanol. Seawater in which the bones were kept prior to preservation was also sieved using 300 µm mesh, and retained macrofauna were preserved in 80% ethanol. The majority of whale bones were subsequently frozen at -20°C, with the exception of three vertebrae preserved in 95% ethanol.
Annelid specimens were shipped to the Australian Museum, Sydney, Australia (AM) and the Natural History Museum, London, United Kingdom (NHM) for identification. The whale bones were deposited at Museums Victoria, Melbourne, Australia (MV). Material deposited at the AM is registered with the prefix "AM W.", while specimens registered at MV have the prefix "NMV", and those at the NHM bear the prefix "NHMUK". Specimens for which all tissue was used up for the molecular analysis were given the prefix WF_. Registration numbers were assigned to individual specimens. We use "undes." for undescribed.

Morphological and molecular taxonomy
Samples from the whale fall were sorted to genus level and examined using stereo and compound microscopes equipped with camera attachments to identify key morphological features of specimens, which were subsequently photographed. Small fragments of tissue were cut from specimens from non-taxonomically informative body regions and used to extract DNA for molecular taxonomy. Unfortunately, many specimens were in a poor condition, thus morphological data is limited.
DNA extractions were performed using a DNeasy Blood and Tissue Kit (Qiagen) following instructions provided by the manufacturer. Approximately 650 bp of cytochrome c oxidase subunit I (COI), 450 bp of 16S rRNA (16S), and 1800 bp of 18S rRNA (18S) were amplified using primers outlined in Table S1. PCR reactions contained 0.5 μl of each primer (10 μM), 1 μl template DNA and 10.5 μl of Red Taq DNA Polymerase 1.1X MasterMix (VWR) in a mixture of total 12.5 μl. The PCR reaction protocol was as follows: 94°C/5 min, (94°C/45 s, 55°C/45 s, 72°C/2 min) × 35 cycles, 72°C/10 min. PCR products were visualized using 1% agarose gel, purified and subsequently sequenced using either an ABI 3730XL DNA Analyser (Applied Biosystems) at the NHM Sequencing Facility, UK, or for samples deposited at the AM, sent to Macrogen South Korea where they were purified and standard Sanger sequencing was performed.

Fauna associated with the whale fall
The most visually dominant colonizer of the whale bones was found to be a small or juvenile mytilid (Fig. 2E), which was observed in high densities on the top and underside of the skull ( Fig. 2A-B), as well as in small clusters on vertebrae (Fig. 2C). COI and 16S sequences for one of the mytilid specimens (NHM_230B) showed 99-100% similarity to sequences available on NCBI GenBank for the species Terua arcuatilis (COI: FJ937036, 16S: HF545067), described from deep waters off New Zealand. In addition to mytilids, actinarians, sponges, nemerteans, gastropods and a holothurian were observed on the whalebones. The tubes of Osedax annelids were also clearly visible on bone surfaces, being abundant on the upper skull surface as well on vertebrae ( Fig. 2A, C-D), while errant annelids found in high numbers in crevices and surfaces of whale bones as well as in the bone washings included phyllodocids, orbiniids, dorvilleids, hesionids and protodrilids. A taxonomic account of two of the observed whale-fall polychaete species, Boudemos sp. (Chrysopetalidae) and Pleijelius sp. (Hesionidae), will be provided in a separate publication (C. Watson, personal communication Notopodia as rounded lobes, with capillary chaetae starting from segment 3 (Fig. 3D). Uncini from segment 5, thoracic uncini arranged in single row of approximately 13 in number (Fig. 3C). Thoracic uncini with teeth arranged in 3 horizontal rows above main rostral tooth and basal prow (Fig. 3E). The rest of body not observed.
Methyl green staining, prostomium speckled on ventral side and ventral bands encompassing whole ventral surface. Notopodia and neuropodia not darkly stained.

Amphinomidae Lamarck, 1818
Paramphinome M. Sars in G. Sars, 1872 Paramphinome cf. australis Monro, 1930 Fig. 5 Paramphinome cf. australis Gunton et al., 2021: 21-22, fig Description. Descriptions based on AM W.52197. Body shape elongate (Fig. 5A), specimen complete, around 4 mm length. Eyes absent. Prostomium rounded. One median unpaired antenna (Fig. 5B), pair of lateral antennae. One or two pairs of strongly curved hooks on chaetiger 1 (Fig.  5C) depending on body size (smaller individuals one, larger individuals two). Arborescent branchiae beginning on chaetiger 4 to chaetiger 7 (Fig. 5D). Parapodia biramous. Notochaetae: capillary chaetae with step-like serrations and smooth unadorned spines. Notoacicula two per fascicle. Neurochaetae long thin capillaries with basal spurs, long thin capillaries no basal spurs, subdistally inflated bifurcate chaetae serrated prongs. Neuroacicula two per fascicle (Fig.  5E). Pygidium unadorned. Remarks. Specimen AM W.52197 closely resembles Paramphinome australis Monro, 1930. A re-description of Paramphinome australis is given in Böggemann (2009). The current specimen differs from Paramphinome australis in the number of strongly curved hooks numbering 1-2 not 2-3 as in Böggemann (2009). There was no difference in the thickness of notochaetae spines (according to Böggemann (2009) andKudenov (1993) and fewer notoacicula and neuroacicula per fascicle were also observed in our material. The type locality of Paramphinome australis is the Southern Ocean off the South Orkney Islands at 244-344 m depth, while Böggemann's (2009) re-description was based on samples from the Angola Basin at 3945-3992 m depth. The author states that the species is "known from Antarctic and Subantarctic regions recorded from subtidal to abyssal depths". This broad bathymetric distribution suggests a species complex. Molecular data recovered our specimens, Paramphinome cf. australis, and Paramphinome jeffreysii McIntosh, 1868 (described from the Shetland Islands) as sister taxa in a well-supported monophyletic group (pp 1.0) (Fig. 6); COI genetic distance between Paramphinome cf. australis and P. jeffreysii was 22% (Table S14). Unfortunately, no molecular data exists for Paramphinome australis and due to the large bathymetric and geographic range suggested for this species, we designate the current material as Paramphinome cf. australis until genetic data is obtained for P. australis.   Description. Small species, body length up to 1.2 mm for examined specimens. Body compressed dorsoventrally, similar width throughout the body until last few segments where it tapers slightly (Fig. 7A). Head of similar width as anterior body, rounded with simple antennae and palps, equal in length (Fig. 7A, 7B). Mandibles rod-like without visible dentition in the examined specimens, apophyse triangular pointing outwards (Fig. 7C). Maxillae of P-type with a pair of forceps and seven pairs of free denticles (D1-7). Forceps with coarse teeth, D1-3 with slightly finer teeth. Denticles 4-7 with fine, evenly sized teeth (Fig. 7D). Parapodia uniramous with large dorsal cirri placed distally, no ventral cirri (Fig. 7E). Supra-acicular chaetae simple (Fig. 7F), sub-acicular chaetae compound with short blades (Fig. 7G), sub-acicular lobe with one simple chaeta. Pygidium with terminal anus, pygidial appendages not observed. Etymology. This species is named in honour of Dr Thomas Dahlgren, NORCE, Norway, and University of Gothenburg, Sweden for his work with whale-fall fauna.
Remarks. This is a small species with few complete specimens. Although pygidial cirri were not observed in any of the most complete specimens, they might not be truly lacking and may have fallen off. In the phylogenetic tree based on 16S (Fig. 8)     Description. Body length up to 3 mm for examined, complete specimens. Body compressed dorsoventrally, anterior body with similar width from head to mid-body, then tapering towards pygidium (Fig. 9A). Head rounded with simple antennae, approximately equal length to palpostyles. Biarticulated palps, palpophores large, equal length to palpostyles (Fig. 9A). Mandibles forked without dentition, inner peak larger than outer peak (Fig. 9B). Maxillae P-type with a pair of forceps and seven pairs of free denticles (D1-7). Forceps with coarse teeth increasing in size from base to tip, D1-3 with progressively slightly finer teeth, D3 with a larger distal fang. Denticles 4-7 with fine evenly sized teeth (Fig. 9B, 9C). Two peristomial achaetous segments, the first twice as long as the second (Fig. 9A). Parapodia uniramous with short distal dorsal cirri, without ventral cirri (Fig. 9D).
Pygidium with terminal anus, two lateral cirri and a midventral stylus. Etymology. This species is named in honour of Dr Hannelore Paxton at Macquarie University, Australia, for her comprehensive work with Ophryotrocha worms, and for sharing her expertise especially regarding the jaw morphology of eunicids.

Remarks.
The new species is morphologically most similar to Ophryotrocha longicollaris Wiklund et al., 2012. The two species differ in shape of parapodia where the new species has larger dorsal cirri, shorter anal cirri, and P-type maxillae while O. longicollaris has only been reported having K-type maxillae. In the phylogenetic tree (Fig. 8), this species does not occur near O. longicollaris, but instead is recovered in an unresolved position in a large clade containing the type species of the genus. The single gene 16S may not be enough to resolve the position. Description. Body length up to 1.6 mm for type material. Body compressed dorsoventrally, width tapering towards pygidium. Rounded head, anterior half flattened with high transverse ridge at level of antennae and palps. Long antennae, simple palps equally long but thinner (Fig. 10A,  10D). Mandibles and maxillae weakly sclerotized, mandibles rod-like with dentate inner ridge, maxillae K-type with blunt forceps tips and seven free denticles (Fig. 10B).

Remarks.
In the phylogenetic tree (Fig. 8), this species falls in a clade with Ophryotrocha nauarchus Wiklund et al., 2012 described from a whale-fall habitat and an undescribed species from a seep, both off the California coast in the eastern Pacific Ocean. However, the support for this clade is low. The head shape of the new species is similar to O. nauarchus, but the new species has longer palps and differs in the shape of the parapodia with the dorsal cirri being placed further distally on the parapodium, and the compound chaetae having short blades. The head shape of the new species is similar to Ophryotrocha scutellus Wiklund, Glover, & Dahlgren, 2009, but the shape of the parapodia is different between the species, with O. scutellus having long ventral cirri on parapodia.
Prostomium semicircular, anteriorly slightly cleft, broader than long (Fig. 11B). Prostomial appendages are all cirriform. One pair of dorsal antennae and one pair of shorter palps terminally located. Median antenna inserted near posterior end of prostomium. Eyes absent. First three segments shorter than others and lack chaetae, bearing six pairs of cirriform tentacular cirri (Fig 11B). Dorsal and ventral cirri present from segment 4. Dorsal cirri shorter on segment 4 than those on segment 5 onwards. Ventral cirri triangular, shorter, and thicker than cirriform dorsal cirri. Body width similar along most of the length (0.14-0.24 mm).

Remarks.
The genus Microphthalmus has been identified in previous studies of whale-fall annelids in the Atlantic (Sumida et al., 2016) and the Pacific (Dahlgren et al., 2004) but no descriptions or molecular data for these have been published to date. This genus is also difficult to place phylogenetically (Fig. 12). Sumida et al. (2016) indicated that the Microphthalmus collected from the Atlantic whale fall was a new species, however whether our specimens represent the same species cannot be determined at present due to the lack of information from previous studies. Male copulatory organs were not examined, which have been suggested to be the most suitable morpho-anatomical character for differentiating between species (Westheide, 2013).

Fig. 13
Vrijenhoekia ketea species complex Gunton et al., 2021: 51-52 Description. Body of AM W.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 thicker than palpostyles, but a similar length to palpostyles. Paired antennae similar in length to palps, tapered, with antennophores not discernible. Eyes absent, median antenna very small relative to others observed for genus, facial tubercle with bulbous end and approximately half length of antennae. Nuchal organs small and not dorsally 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).  (Table S15). In general, for the genus, V. timoharai sp. nov. shows 6-19% distance to all other Vrijenhoekia species while a genetic distance of 0.8% was observed between the two individuals sequenced. Vrijenhoekia timoharai sp. nov. has the shallowest distribution in this genus 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, &V. falenothiras Summers, Pleijel, & 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. In comparison 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.

Nereididae Blainville, 1818
Neanthes Kinberg, 1865 Neanthes adriangloveri sp. nov. Description. Holotype posteriorly incomplete, 41 mm long for 54 chaetigers and with maximum width of 2.6 mm. Body shape cylindrical, tapering towards pygidium. Live specimen with reddish iridescent colouration (Fig. 14A), with a distinct bright red dorsal blood vessel in the anterior half of the specimen. Ethanol-preserved specimen pale yellow. Prostomium ( Fig. 14B) trapezoidal, as wide as long, with dorsal depression that extends from anterior tip to almost posterior margin of prostomium. One pair of cirriform, distally tapering antennae, of similar length to palps. One pair of palps, with robust cylindrical palpophores and smaller broadly conical palpostyles. One pair of eyes faintly visible on living specimen (Fig. 14A), but not discernible after preservation (Fig. 14B); eyes very small, reddish, located near the posterior margin of prostomium. Tentacular belt (first adult annulus) almost twice as long as the first chaetiger (somewhat distorted by the slightly everted pharynx), with four pairs of tentacular cirri. Tentacular cirri with short, cylindrical cirrophores and cirriform, distally tapering styles; the postero-dorsal pair longest extending to the third or fourth chaetiger (Fig. 14B); the ventral pair short with styles reaching the length of palps.
Parapodia of biramous chaetigers (Fig. 14C-E) with notopodial dorsal cirri inserted at the base of, and up to 1.5 times length of dorsal notopodial ligules, longest in anterior third of specimen; those of mid and posterior body area heavily vascularized (Fig. 14D-E). Biramous parapodia progressively changing throughout the body in form and size (Fig. 14C-E), becoming smaller posteriorly. Anterior notopodia (Fig. 14C) with long smooth dorsal cirrus, approximately 1.5× the length of corresponding dorsal notopodial ligule; dorsal notopodial ligule large and broadly conical, prechaetal lobe reduced, ventral notopodial ligule large and conical, slightly smaller than dorsal ligule. Anterior neuropodia (Fig. 14C) with prechaetal ligule short, conical, postchaetal ligule broad and low; ventral ligule broadly conical, extending just short of postchaetal ligule; ventral cirrus slender, cirriform distally tapering, approaching the length of ventral ligule. Mid-body notopodia ( Fig. 14D) with smooth dorsal cirrus shorter than in anterior parapodia, but slightly exceeding the length of the corresponding dorsal ligule to which it is medially attached; dorsal ligule as for anterior ones, prechaetal lobe and ventral notopodial ligules as for anterior ones. Mid-body neuropodia ( Fig. 14D) with prechaetal and postchaetal ligules as for anterior ones; ventral ligule broadly conical extending to level of corresponding postchaetal ligule; ventral cirrus slender, cirriform and distinctly shorter than corresponding ligule. Posterior notopodia (Fig. 14E) with smooth dorsal cirrus approximately 1.5× length of corresponding dorsal ligule to which it is medially attached; dorsal notopodial ligule as for anterior ones, except somewhat constricted at the attachment of dorsal cirrus as basal portion appearing highly vascularized (possible early epitokal modification); prechaetal and ventral notopodial ligules as for anterior ones. Posterior neuropodia ( Fig. 14E) with prechaetal and postchaetal ligules as for anterior ones (Fig. 14C); ventral ligule as for mid-body ones (Fig. 14D); ventral cirrus slender, cirriform and extending just short of corresponding ligule (Fig. 14E).
Pygidium not observed (missing) on holotype AM W.53703. Etymology. This species is named in honour of Dr Adrian Glover of the Natural History Museum, United Kingdom, deep-sea biologist and polychaetologist, for his work with whale-fall fauna.

Remarks.
We were unable to obtain molecular data for this species. The presence of visible eyes (albeit only one pair rather than the typical two pairs) in living specimens distinguishes N. adriangloveri sp. nov. from the deep-sea Neanthes species Neanthes shinkai Shimabukuro, Santos, Alfaro-Lucas, , Neanthes abyssorum Hartman, 1967, Neanthes kermadeca (Kirkegaard, 1995, and Neanthes typhla (Monro, 1930 (Day, 1963) (off Cape Town) and Neanthes donggungensis Hsueh, 2019 (off Taiwan), N. adriangloveri sp. nov. has a greater number of paragnaths in most pharyngeal regions compared to N. articulata. Neanthes kerguelensis has much longer tentacular cirri compared to N. adriangloveri sp. nov., N. papillosa has neuropodial falcigers that are all heterogomph with long blades and slender tips, and N. donggungensis has a larger and thicker body. Finally, the most notable features of this species, which in combination potentially distinguish it from all other Neanthes-the presence of a single pair of eyes and distally curved aciculae (especially pronounced in the neuropodia)-both require further assessment based on more specimens: small eyes that are only visible in live specimens may easily be overlooked and bent aciculae may be attributable to muscle contraction during preservation. Description. Holotype complete, pinkish-purple when alive, with whitish notopodial ligules and noticeable iridescence (Fig. 15A); 85 chaetigers, up to 50 mm long and a maximum of 2.6 mm wide (without parapodia), tapering towards posterior.
Prostomium (Fig. 15B) trapezoidal, longer than wide, with a dorsal depression that extends from anterior tip to just below eyes. One pair of short antennae approximately onequarter length of prostomium and one pair of elongated palps with cylindrical palpophore and oval-shaped palpostyle, extending just beyond antennae. Two pairs of eyes, anterior pair roughly oval-shaped, posterior pair slightly larger, kidney-shaped, and slightly closer together.
Etymology. Named derived from the Latin root "visitar" for a visitor, and "cete", a whale, referring to the new species' occurrence on a whale fall. Noun in apposition.

Remarks.
Our Nereididae molecular phylogeny (Fig. 16) resolves Neanthes visicete sp. nov. in a clade with Neanthes acuminata Ehlers, 1868, however, with poor support. While a Nereididae phylogenetic analysis by Villalobos-Guerrero et al. (2022) recovered Alitta and Nectoneanthes in a clade with Neanthes acuminata, Alitta, and Nectoneanthes occurred in a separate clade in our phylogenetic analysis, Figure 15. See caption on facing page. perhaps due to the different genetic markers included. No other known Nereididae species for which genetic data are available appear to be genetically closely related to N. visicete sp. nov., with genetic distances being a minimum of 17.7% between N. visicete sp. nov. and other Nereis and Neanthes species for which genetic data is available (Table S16). Neanthes acuminata is recognized as a species complex, of which the species Neanthes arenaceodentata (Moore, 1903) and Neanthes cricognatha (Ehlers, 1904) are also a part (Reish et al., 2014). Of these, N. cricognatha is the only species to have been reported from off Australia, including a recent record at 1194-1257 m depth from the IN2017_V03 expedition (Gunton et al., 2021). Neanthes visicete sp. nov. differs from the IN2017_V03 N. cricognatha specimens visibly due to its whitish notopodia in living specimens, and a different paragnath arrangement of Areas V-VIII (broad continuous band in the latter, areas discrete in the new species). A few other species of Neanthes have been recorded from deep waters off Australia. Neanthes cf. bassi Wilson, 1984 was also recorded from the IN2017_V03 expedition and recent voyages to the Great Australian Bight at depths of 200-4800 m (Gunton et al., 2021). Neanthes bassi, Neanthes tasmani Bakken, 2002 and N. kerguelensis are morphologically very similar, however in comparison to N. visicete sp. nov., none of these species have the whitish grainy notopodia that appear characteristic of N. visicete sp. nov. Additional differences are that N. bassi has smooth bars in pharyngeal Area IV (Wilson 1984) while both N. kerguelensis and N. tasmani have fewer paragnaths in Areas VI-VIII (Bakken, 2002); N. kerguelensis additionally has longer tentacular cirri than N. visicete sp. nov. Finally, all three species have heterogomph falcigers, whereas they are absent from the new species. Neanthes heteroculata (Hartmann-Schröder, 1981) was also recorded from the IN2017_V03 voyage at 3980-4280 m depth (Gunton et al., 2021), but these specimens have very large eyes and are thus again clearly distinguishable from N. visicete sp. nov.
Neanthes visicete sp. nov. and Neanthes adriangloveri sp. nov. are only the second and third formally described Neanthes to be found associated with a whale fall. The first, N. shinkai, was described from abyssal depths of the southwest Atlantic. This species is quite different from the two new Neanthes species described here in lacking prechaetal notopodial lobes, postchaetal neuropodial lobes and eyes; in these features and in our molecular phylogeny N. shinkai more closely resembles our Nereis sp. (see following account).  analysed the carbon and nitrogen isotopes of N. shinkai and concluded that it was an omnivore that was feeding mainly on the organic matter from the whale.  (Fauvel, 1932), N. cricognatha, N. kerguelensis, N. picteti (Malaquin & Dehorne, 1907), N. pleijeli de León-González & Salazar-Vallejo, 2003 and N. suluensis. Considering the paragnath numbers of these nine species, the new species is-as also found using molecular data-closest to Neanthes acuminata, N. arenaceodentata and N. cricognatha, but differs in having a greater number of paragnaths in Area III (c. 45 vs 23-28 in acuminata; 20-34 in N. cricognatha), and fewer in this area than arenaceodentata (82) and having paragnaths absent in Area V, vs present and merging with a broad band of paragnaths in Areas VII-VIII in N. acuminata, N. arenaceodentata and N. cricognatha. Neanthes visicete sp. nov. has a high number of paragnaths in Area I (13) which distinguishes it from N. articulata (1), N. chingrighattensis (2-6; chingrighattensis also has the unusual presence of a neuropodial superior lobe which is absent in the new species), N. kerguelensis (0-4), N. picteti (2) and N. pleijeli (2). The new species can be distinguished from the poorly known N. suluensis by having 2 or 3 rows of paragnaths in Areas VII-VIII (only 1 in suluensis). Finally, the new species can be distinguished from all known Neanthes species by lacking heterogomph falcigers, by its distinct ventral pygidial lobe (although pygidial features are poorly known in Nereididae), and its distinctive living colouration (pinkish-purple with whitish dorsal notopodial ligules and noticeable iridescence).
The presence of a large prechaetal notopodial lobes throughout the body in the new species (and the N. acuminata species complex), such that the notopodia appear to have three similar-sized lobes/ligules, also occurs in Alitta, Nectoneanthes and Leonnates (Bakken, 2006;Bakken et al., 2022). One might therefore question the placement of the new species in Neanthes considering its lack of heterogomph falcigers; however, the new species is here treated as a Neanthes because it lacks the presence of an expanded dorsal notopodial ligule of Alitta, it lacks the ovoid lobe above the dorsal cirrus of Nectoneanthes, and the oral ring papillae of Leonnates.
Although closest to Neanthes in overall morphology (because the concept of Neanthes is currently so broad), the species does not fit the current definition of Neanthes (Bakken et al., 2022;Villalobos-Guerrero et al., 2022), because of its lack of neuropodial heterogomph falcigers. It has homogomph and sesquigomph falcigers, and they are restricted to anterior and mid-body chaetigers. This emendation is best made in a future revision of the genus.
Specimen AM W.52210 posteriorly incomplete, 8.2 mm long and a maximum width of 0.9 mm (excluding parapodia) for 33 chaetigers; in moderately poor condition probably due to fixation in ethanol resulting in paragnath shedding and most cirri and some ligules/lobes in process of falling off.
Prostomium trapezoid (Fig. 17B), approximately as wide as long. One pair of cirriform, distally tapering antennae, approximately the same length as palps. One pair of robust palps, with cylindrical palpophores and smaller oval palpostyles. Eyes not observed. Tentacular belt (first adult annulus) approximately 1.5× length of the subsequent segments, with four pairs of tentacular cirri. Tentacular cirri with cylindrical tentaculophores, only two shorter pairs with styles attached, styles smooth not extending beyond prostomium (Fig. 17B).
First two chaetigers uniramous, the following biramous. Dorsal cirri on uniramous chaetigers slightly longer and inserted at the base of dorsal notopodial ligules. Dorsal and ventral ligules a similar conical shape and size, slightly longer than ligules adjacent to chaetae. Ventral cirri of a similar length to ventral ligules.
Pygidium rounded; cirri not observed. Remarks. Two specimens collected as part of this study likely belong to genus Nereis, as they possess homogomph falcigers in the posterior notopodia. The description above builds upon that of Gunton et al. (2021; referred to as Nereis sp. 1) which was based on one of the two specimens examined here; despite the additional morphological information from the second specimen and the support from sequence data, we are reluctant to formally name the new species for the reasons below.
Nereis is currently the most species-rich genus within Nereididae, with many deep-water species, a problematic taxonomic history, morphological characters affected by the reproductive status of the specimen as well as exhibiting a high level of homoplasy (e.g., Bakken & Wilson, 2005;Santos et al., 2006). Further, molecular information obtained from the specimens included in this study suggests that specimens identified here as Nereis sp. are genetically similar to Neanthes shinkai ( Fig. 16; COI genetic p-distance between Nereis sp. and Neanthes shinkai was 12.6%; Table S16); N. shinkai is also described from a whale fall, but one located at 4200 m depth on the São Paulo Ridge in the Southwest Atlantic . A number of other Nereis species are also included in the well-supported clade containing Nereis sp. and Neanthes shinkai (Fig. 16). We are also aware of colleagues who are in the process of describing a new eyeless species of Nereis from the southwest Atlantic, and there is a chance that it could be the same as our IN2017_V03 specimens. Solving taxonomic problems is beyond the remit of this study and as a result we assign the specimens to genus only.
Prostomium bluntly conical (Fig. 18C), without appendages, eyes absent. Nuchal organs only detected as lateral pits on prostomium. Peristomium approximately twice as long as prostomium, weakly annulated dorsally, but distinct annulation observed ventrally, with two achaetous rings of similar size.
Notopodia low mounds from which chaetae emerge (Fig. 18D); neuropodial postchaetal lobes from chaetiger 4 (5 in specimen AM W.52199), extending posteriorly to approximately start of branchiate region, whereafter they appear to be absent (or minute); best developed about mid-body where they slender, subconical-shaped, approximately 0.25× length of chaetae (Fig. 18E). Branchiae present; absent in anterior-most segments; becoming apparent after segment 55. Branchiae initially small and ovoid (Fig. 18F), increasing in length towards posterior to a maximum size of approximately ⅔ length of chaetae, strap-like (Fig. 18G); reducing slightly in size over the last few chaetigers.
Chaetae include both crenulated capillaries (Fig.  18H) and short acicular spines (Fig. 18H) in both rami; furcate setae absent; no evidence of imbedded aciculae. Notochaetae bundles of crenulated capillaries of various lengths throughout; straight slightly serrated spines present from chaetiger 1 (up to 3 per ramus observed). Neurochaetae generally slenderer than notochaetae composed of crenulated capillaries and up to 3 spines; neuropodial spines slenderer and longer than those in notopodia, distally slightly curved into slender tip. Pygidium with two broad lobes, anal cirri not observed. Etymology. Named for James Hayhurst, for his support to one of the authors (M. Georgieva) during a multitude of scientific endeavours.

Remarks.
Orbiniella jamesi sp. nov. specimens with neuropodial postchaetal lobes exhibit identical COI sequences to Orbiniella sp. without such lobes (Figs 19, 20). Support values in our phylogenetic analysis are generally low, with our specimens being resolved as most closely related to a Scoloplos acutissimus specimen whereas the only Orbiniella specimen for which genetic data was available falls outside of this group.
Specimens collected in this study belong to Orbiniidae that lack a distinct body division into thorax and abdomen regions due to a dorsal shift of chaetae. Such forms are currently included in genera Methanoaricia, Orbiniella (Parapar, Moreira, & Helgason, 2015), Proscoloplos, Protoariciella, and Uncorbinia (Beesley et al., 2000;Solis-Weiss & Fauchald, 1989;Blake, 2000;Parapar et al., 2015). Methanoaricia however differs from orbiniid specimens presented here in having a long and narrow prostomium, while Proscoloplos are generally small and along with Protoariciella and Uncorbinia have hooked chaetae. Uncorbinia has only a single described species from northwestern Australia and is considered to be a probable synonym of Califia (Blake, 2000).
Assignment of the IN2017_V03 orbiniid specimens to the existing genus Orbiniella also reflects our molecular phylogenetic results for the family Orbiniidae (Fig. 19), which largely do not demonstrate clear genetic definitions. We therefore reserve the establishment of a new genus until current genetic relationships are better known, but we proceed with the formalization of new species Orbiniella jamesi sp. nov. We tentatively assign the new species to genus Orbiniella due to possession of a broadly conical prostomium, bi-annulate peristomium, poorly developed parapodia, lack of furcate chaetae, no obvious division of body into thorax and abdomen, and no dorsal shift of parapodia.
To date, only one other orbiniid species is known from a chemosynthetic environment, Methanoaricia dendrobranchiata Blake, 2000. This species has large branched branchiae which may be advantageous in the generally lower oxygen conditions prevalent in these environments. It is therefore possible that branchiae might be a character common to orbiniids that occur within chemosynthetic environments, however further discoveries are necessary to verify this.
Orbiniella sp. Description. Best preserved specimen NHMUK ANEA 2022.431 complete, ~9 mm long and 0.7 mm wide for ~95 chaetigers. Specimen AM W.52198 anterior fragment with 15 chaetigers. Specimen AM W.52200 anterior end, with ~40 discernible chaetigers. Body somewhat dorsoventrally flattened throughout, not divided into distinct regions; individual chaetigers narrow, similar throughout; posterior parapodia not dorsally elevated (Fig. 20A). Live specimens Figure 19. Phylogeny of the Orbiniidae family 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. not observed, ethanol-preserved specimens tanned (Fig 20A).
Parapodia reduced to low mounds from which chaetae emerge; no neuropodial postchaetal lobes. Branchiae present; absent in anterior-most segments and becoming apparent after approximately 30 segments in adult specimens (Fig.  20A). Branchiae initially small and conical, increasing greatly in length towards posterior where they become straplike, slender and elongated (Fig. 20C); greatly reduced in size again in the few posteriormost chaetigers.
Chaetae include both crenulated capillaries (Fig. 20D) and short acicular spines (Fig. 20E) in both rami; furcate setae absent; no evidence of imbedded aciculae. Notochaetae as bundles of crenulated capillaries of various lengths throughout; straight slightly serrated spines present from chaetiger 1 (up to 3 per ramus observed). Neurochaetae generally slenderer than notochaetae composed of crenulated capillaries and up to 3 spines; neuropodial spines slenderer than in notopodial one, distally slightly curved into slender tip. Pygidium with two broad lobes, anal cirri not observed.
Variation. Juveniles (Fig. 20F) small specimens with length of 1.2-4 mm and width of 0.1-0.2 mm, for 20 to ~50 chaetigers, branchiae always present, appearing ~chaetiger Remarks. Specimens assigned here to Orbiniella sp. are morphologically similar to Orbiniella jamesi sp. nov., but differ in the following characters: neuropodial postchaetal lobes are absent, body is more robust, posterior branchiae are shorter and thicker than in O. jamesi sp. nov. The development and number of neuropodial postchaetal lobes have been suggested to differ among developmental stages in Orbiniidae, but here the differences were observed in specimens of similar length (7-9 mm) and possessing similar number of chaetigers (90-95). A number of very small juveniles (Fig. 20F) were also found in the samples. However, the molecular results indicate that specimens assigned here to Orbiniella sp. and Orbiniella jamesi sp. nov., as well as juvenile specimens represent the same species (Fig. 19). Currently, the understanding of developmental stages in Orbiniidae is limited despite some recent advances (see Blake, 2021) and we thus tentatively ascribe the specimens without neuropodial postchaetal lobes to Orbiniella sp., rather than Orbiniella sp. nov. that has well-developed lobes. Gunton et al. (2021, fig. 18F) assigned a specimen fitting Orbiniella jamesi sp. as described here to an unknown genus of Protoariciinae, but this placement is at odds with the molecular phylogeny of this study which shows protoariciines in a more crown position compared to Orbiniella (Fig. 19).
Prostomium pentagonal with rounded corners, wider than long (Fig. 21B). Anterior end of prostomium with pair of antennae slightly longer than prostomium dorsally and similar pair of palps ventrally. A median antenna, shorter and thinner than frontal antennae, inserted near middle of prostomium. Eyes absent.
Parapodia uniramous with a single acicula and numerous heterogomph spinigers (Fig. 21E). Shaft of chaetae with apical teeth and blade with fine serration.

Remarks. Recognized Eumida species lacking eyes include
Eumida alvini Eibye-Jacobsen, 1991, Eumida angolensis Böggemann, 2009, Eumida (Eumida) longicirrata Hartmann-Schröder, 1975, and Eumida nuchala (Uschakov, 1972). Among these, the IN2017_V03 Eumida specimens most closely resembled E. longicirrata, which has the median antenna inserted slightly anterior to the middle of the prostomium unlike the other species where it is inserted closer to the posterior end. The other species are also distinct from the IN2017_V03 specimens in the following ways: E. alvini have the median antenna longer than the frontal pair as well as very long tentacular and dorsal cirri; E. angolensis have oval prostomium and "bottle-shaped" tentacular cirri (Böggemann, 2009); E. nuchala have enlarged nuchal organs and ventral cirri much longer than the parapodial lobe.
Raised semicircular structures on the posterior end of the prostomium, described for E. longicirrata, were difficult to observe in the IN2017_V03 specimens. This was also the case for other specimens identified as E. longicirrata . The micropapillae observed in the proboscis of the IN2017_V03 specimens is contrary to the smooth proboscis described for E. longicirrata. The presence of >40 oral papillae (NHMUK ANEA 2022.404) is unusual since most Eumida species often have 17, except for E. alvini, which can range from 22-50 (Eibye-Jacobsen, 1991). Estimates of tentacular cirri lengths, measured by the extent of reach along body segments, are similar to E. longicirrata. It should be noted that live specimens were observed to have more contracted segments compared to preserved specimens (Fig. 21), so this measurement differs between the two. Based on the illustrations of the holotype of E. longicirrata, estimates of cirri length were measured from live specimens while the IN2017_V03 specimens were measured from preserved specimens.
Incorporating the COI sequences of IN2017_V03 specimens and all available sequences of the closely allied genus Sige in GenBank with those used by Teixeira et al. (2020) places these samples within a clade of Sige spp. and sister group to Sige fusigera Malmgren, 1865 (Fig. 22). The Australian specimens, however, lack the characteristic pointed superior parapodial lobe of other Sige species (Eklöf et al., 2007). San Martín et al. (2021) found Sige, Eumida and other closely related genera to be paraphyletic and polyphyletic in their analyses. Further investigation is warranted to explore the relationship among these genera. This is the first report of eyeless Eumida species occurring at 1000 m. Previous records were collected at depths >3000 m.   Pseudomystides Bergström, 1914 ?Pseudomystides sp.
Prostomium wider than long and terminally cleft (Fig.  23B). Prostomium sometimes more darkly pigmented than rest of body. Terminal protuberance present where paired antennae and palps inserted. Frontal antennae and palps digitiform, both approximately same length as prostomium. Median antenna smaller and thinner than paired antenna and inserted near center of prostomium. Eyes absent. Proboscis retracted in all specimens.
Pygidium broad and blunt with two tear-drop-shaped anal cirri (Fig. 23D). Median pygidial papilla present. Remarks. Phyllodocid genera that have three tentacular cirri in the first two segments and the third segment lacking a dorsal cirrus include Hesionura Hartmann-Schröder, 1958, Mystides Théel, 1879, and Pseudomystides Bergström, 1914(Eklöf et al., 2007. Hesionura and Mystides both have a pair of antennae and palps, fewer than the IN2017_V03 specimens. We assign these specimens to Pseudomystides since an additional median antenna is described in three of the five described species. Within the genus Pseudomystides, these differ from the other species in having far fewer segments, a broad prostomium, unlike Pseudomystides limbata (Saint-Joseph, 1888) and Pseudomystides rarica (Uschakov, 1958), and digitiform to lanceolate dorsal and ventral cirri, unlike Pseudomystides bathysiphonicola (Hartmann-Schröder, 1983), Pseudomystides brevicirra Böggemann, 2009, andPseudomystides spinachia Petersen &Pleijel in Pleijel, 1993. The median antenna for the Australian specimens is also inserted near the middle of the prostomium, unlike in P. limbata, P. rarica, and P. spinachia where it is inserted posteriorly. We were unable to obtain DNA sequence data from the samples which prevented us from comparing their relationships with other Pseudomystides species. Description. Body shape slender and filiform with head slightly larger than body (Fig. 24). Paired antennae inserted terminally; no eye spots visible. Pygidium with paired lateral lobes and a median cluster of cilia. Description. Female tube long (25 mm, specimen NHMUK ANEA 2022.403), anteriorly thin, semi-transparent and appearing rounded and closed at the tip (Fig. 26A), posterior tube tough and creased. Females with crown of four palps fused for much of their length (6.8 mm in specimen NHMUK ANEA 2022.403), contracted within tubes and without obvious pinnules but slightly wrinkled and with distinct blood vessels in live specimens (Fig. 26B). Trunk (Fig. 26C) short  basal in relation to all other nude palp species, with the exception of Osedax deceptionensis Taboada, Cristobo, Avila, Wiklund, & Glover, 2013. Uncorrected COI genetic distances between O. waadjum sp. nov. and other Osedax species are a minimum of 14% (Table S17), while within species they are less than or equal to 0.4%. Osedax waadjum sp. nov. is described mainly on the basis of genetic data as many of the specimens were damaged during removal from the whale bones. The closed-top tube morphology of this species resembles that of Osedax lonnyi Rouse, Goffredi, Johnson, & Vrijenhoek, 2018 and Osedax jabba Rouse, Goffredi, Johnson, & Vrijenhoek, 2018. Other nude palp Osedax species occupying a similar depth include Osedax antarcticus Glover, Wiklund, & Dahlgren, 2013, Osedax docricketts Rouse, Goffredi, Johnson, & Vrijenhoek, 2018, Osedax knutei Rouse, Goffredi, Johnson, & Vrijenhoek, 2018, and Osedax westernflyer Rouse, Goffredi, Johnson, & Vrijenhoek, 2018, described from the Southern Ocean or Eastern Pacific. Osedax docricketts and O. westernflyer also occur in Sagami Bay off Japan.
in relation to the length of the palps (0.6 mm in specimen NHMUK ANEA 2022.402). Oviduct extends from base of palps (Fig. 26D), opposite side of trunk bears a folded, wrinkled lobe (Fig. 26E). Ovisac not observed. Males 385 µm in length (Fig. 26F), bearing hooked chaetae anteriorly, and observed at various positions within female tubes. Remarks. Genetic data confirms that these specimens comprise a new species that falls within the same clade as other nude palp Osedax species with good support (Fig.  27). The position of Osedax waadjum sp. nov. appears    Etymology. This species is named after the town of Byron Bay, Australia, off which this whale fall was discovered.
Remarks. Osedax byronbayensis sp. nov. is known only from three incomplete specimens, therefore a complete morphological description was not possible. Molecular data demonstrates the three specimens to belong to the same species with high support (Fig. 27)

Remarks. Similar to Sphaerodoropsis exmouthensis
Hartmann-Schröder, 1981 re-described by Capa & Bakken (2015); type locality shallow water from Tantabiddi Creek, Exmouth, Western Australia. Our specimens have more chaetae per fascicle than S. exmouthensis. The species is genetically distinct from all other Sphaerodoridae (Table  S18) and forms an unresolved clade with Sphaerodoropsis cf. martinae Desbruyères, 1980  Description. Specimens AM W.52201, AM W.52202 and AM W.52203 all in poor condition, only two small anterior fragments (max. 4 mm length) and one posterior fragment remaining (Fig. 31A-B Remarks. Bayesian analysis of combined dataset of COI, 16S and 18S sequence data reveals that our species is a sister group to Phascolosoma (Phascolosoma) turnerae Rice, 1985 although support is low (pp 0.5) (Fig. 32); average COI pairwise genetic distance between the two species is 26.7% (Table S19). In our analysis Phascolosoma sp. and all other Phascolosoma species, except Phascolosoma capitatum Gerould, 1913, are recovered as a poorly supported clade (pp. 0.5). This result partly agrees with Bayesian analysis on four genes (18S, 28S, H3 and COI) in Schulze, Cutler, & Giribet (2007), where all species of Phascolosoma except P. capitatum and P. turnerae formed a monophyletic group. Interestingly P. turnerae is also a deep-water species described from 366-1184 m associated with submerged wood (Rice, 1985), whereas all other species of Phascolosoma except for P. capitatum are shallow-water species. Due to the poor morphological condition of the specimens the species is not formally described here.

Discussion
In documenting the annelid community from the first discovery of a natural whale fall in deep Australian waters, this study provides vital information on the nature of whalefall ecosystems in this part of the world, as well as their connections to other organic falls in the western Pacific and beyond. Given the dominance of polychaetes on this whale fall, it was likely in the enrichment/opportunistic stage of its decomposition (Smith et al., 2015).

Composition and diversity of the whale-fall annelid community
Visually dominant taxa associated with this whale fall included a small mussel genetically near-identical to the species Terua arcuatilis described from whale falls off New Zealand (Dell, 1995) (Fujiwara et al., 2007) as well as to a South Atlantic whale fall (Sumida et al., 2016), polychaete species richness seems to be similar but the composition of taxa somewhat different. However, given the different sampling techniques between studies (some also sampled sediments around whale falls), it is difficult to directly relate this whale-fall community to others. While Terua arcuatilis may be a regular colonizer of whale falls in this part of the world, to the best of our knowledge this is the first whale fall to include a dominant Orbiniella species, although orbiniids were also reported from sperm whale falls off Japan (Fujiwara et al., 2007). In addition,  the annelid family Sphaerodoridae has not been recorded on whale bones to date; only one species Sphaerephesia kitazatoi  has been observed in sediments around a whale-fall carcass from the south-west Atlantic Ocean at the base of the São Paulo Ridge (4204 m depth). The genus Pseudomystides (Phyllodocidae) has also not been recorded on whale bones (Böggemann, 2009). The majority of other annelids reported from this whale fall belong to genera that have been previously observed on whale falls and/or other chemosynthetic habitats. High abundances of protodrilids occurred on whale falls in western Pacific off Japan (Fujiwara et al., 2007), off California (Braby et al., 2007), as well as recently having been observed on Mid-Atlantic Ridge (near the Azores) (Silva et al., 2021). Protodrilids are interstitial annelids with a worldwide distribution (Westheide, 1990), and might thus be expected to appear at whale falls globally. The dorvilleid genus Ophryotrocha is known for its preference for sites of organic enrichment and is also a frequent whale-fall colonizer globally (Wiklund, Glover, & Dahlgren, 2009). The genus Osedax, described from Australian waters for the first time, also appears to be diverse in this part of the world with two species detected from this whale fall alone (Fig.  27), a further species known to occur off South Australia (G. Rouse, personal communication), and two additional species recently reported off New Zealand (Berman, 2022). The hesionid genus Pleijelius has been documented from both whale-and wood falls in the Atlantic (Sumida et al., 2016;Silva et al., 2021;Salazar-Vallejo & Orensanz, 2006;Saeedi et al., 2019) and thus seems to also favour sites of organic enrichment. The phyllodocid Eumida longicirrata has also been reported from mud volcanoes in the Gulf of Cadiz , but this genus is not generally exclusive to chemosynthetic environments (De Oliveira et al., 2015).
Less abundant polychaetes associated with the IN2017_ V03 whale fall that are also already documented from whale falls include Paramytha cf. ossicola, Microphthalmus sp., Vrijenhoekia timoharai sp. nov., Neanthes adriangloveri sp. nov., Neanthes visicete sp. nov., Phascolosomatidae and Amphinomidae. Of these taxa, the genera Microphthalmus and Vrijenhoekia (along with Pleijelius sp.) were also 208 Records of the Australian Museum (2023) Vol. 75 discovered to co-occur on a south-west Atlantic whale fall (Sumida et al., 2016), Vrijenhoekia is also known from a Mid-Atlantic Ridge (Azores) whale fall as well as from the north-east Pacific (Summers, Pleijel, & Rouse, 2015;Pleijel et al., 2008), and Microphthalmus also from the Pacific (Dahlgren et al., 2004). The ampharetid genus Paramytha is known from sunken cow bones in the north-east Atlantic and the Arctic vent site Loki's Castle (Queirós et al., 2017;Kongsrud et al., 2017), at which Paramytha ossicola was reported at high abundances of 2173 specimens (up to 3.37 individuals cm -2 ) on cow bones in the Setúbal Canyon (NE Atlantic) (Queirós et al., 2017). However, its absence was noted at the Mid-Atlantic Ridge (Azores) whale fall documented by Silva et al. (2021), and the finding of only three specimens in our material may be a result of the timing of sampling relative to decomposition as Paramytha is likely a deposit or detritus feeder best adapted to the enrichmentopportunistic successional stage. Nereidid species including the genus Neanthes also commonly occur on whale falls and are often associated with the late enrichment-opportunist and sulfophilic stages of deep-sea whale-fall successions . Two unidentified Sipuncula species were reported in this study from an unusual whalefall community in Monterey Bay (Goffredi et al., 2004), while unidentified Amphinomidae have been observed on whale falls from the above region (Braby et al., 2007).

Biogeographic and evolutionary observations
As well as revealing for the first time the composition of a whale-fall annelid community in the Australian region, this whale-fall discovery fills an important gap in the distribution of one of the most iconic whale-fall taxa, the bone-eating siboglinid genus Osedax. The occurrence and distribution of this genus is poorly known in the southern hemisphere as only six out of a current total of 27 described species are known from this part of the world (five Osedax species from the Southern Ocean (Amon et al., 2014;Glover et al., 2013) and a single species reported off Brazil (Fujiwara et al., 2019)). The phylogenetic position of O. waadjum sp. nov. is also interesting (Fig. 27), as this species appears to have a basal position with respect to the majority of other nude-palp species. Interestingly, the above is also mirrored by a new Osedax species from New Zealand (Berman, 2022). Notably, an Osedax sp. tissue fragment from IN2017_V03 operation 088, Central Eastern Marine Park, 4400 m depth, is closely related to the unusual palpless species O. jabba along with which it forms a clade basal to all pinnulate palp species (Fig. 27). In addition to unexplored diversity, it is likely that the southern hemisphere may reveal much about the evolution of this iconic genus.
The occurrences of Paramytha cf. ossicola and Pleijelius sp. on the IN2017_V03 whale fall represent the first records of these genera in the Pacific Ocean (Gunton et al., 2021), and suggest a potentially global distribution for these likely chemosynthetic habitat-specialist genera. Vrijenhoekia and Microphthalmus sp. are recorded from the western Pacific for the first time, while the close genetic similarity between the Protodrilus cf. puniceus from this study and P. puniceus from off Japan (Fig. 21) may suggest potential connectivity along the western Pacific for certain taxa, but more genetic data is needed to resolve this. Additionally, the close relationship between Nereis sp. and Neanthes shinkai (Fig. 16) may indicate the existence of nereidid lineage that specializes on whale falls, as well as indicating the inadequate generic concepts. The record of an eyeless Eumida species reported herein is also the shallowest documented so far (others are known from >3000 m depth).
Whale falls can act as species dispersal "stepping stones" (Smith et al., 2015) and given that a number of whale species regularly traverse Australian waters bridging the Southern Ocean (such as humpback, fin and southern right whales (Aulich et al., 2019;Carroll et al., 2011;Groß et al., 2020), New Zealand and the South Pacific region, natural whale falls in this region are also likely to be plentiful. Indeed, capturing a whale fall opportunistically during the IN2017_V03 voyage attests to this, and suggests connectivity in whale-fall taxa between these regions may be high. Further exploration of the deep ocean around Australia likely has much to reveal about these fascinating ecosystems, as well as about southern hemisphere deep-sea chemosynthetic environments in general.