Marphysa tompaulingi sp. nov.

LSID urn:lsid:zoobank.org:act: 141FD0EC-8C6E-4262-B346-C7677E63DF58

Figures 8–11, Table 3

Type material. Holotype 1 (NTM W32646), Ludmilla Creek, East Point, near ‘Spot On Marina’, 12.4117°S 130.8372 °E sandy-mud, collected at low tide in mid-channel, coll. O. Biriukova, Lucy Kania, 30 Oct 2023. Paratypes: 1(AM W.54819), 1 (AM W.54820), 1 (AM W.54821), field number CG23-02, same locality as holotype, coll. C. Glasby, O. Biriukova, 20 May 2023.

Description (based on holotype, except for far posterior parapodia/chaetae and pygidium based on AM W.54820). Live worms anteriorly iridescent, crimson base colour, lighter reddish coloured posteriorly with contrasting red branchial filaments; additional pigmentation absent (Fig. 8A). Prostomial appendages cream-coloured except for reddish ceratophores (Fig. 8B, C). Preserved specimen almost complete, posterior end regenerating (24 newer chaetigers), 235 chaetigers, 98 mm long, 4.0 mm width at chaetiger 10, excluding parapodia; chaetigers 195–200 with right-side scar from tissue sampling. Body elongate, widest at anterior-midbody and tapered gradually at both ends, slightly dorsoventrally flattened after widest region (Fig. 8A).

Prostomium rounded anteriorly with two dorsoventrally flattened buccal lips and a deep anterior notch between them (Fig. 8B); wedge-shaped in lateral view (Fig. 8C); approximately equal in length to peristomium. Prostomial appendages comprising two palps and three equal-length antennae (median antenna absent in paratype AM W.54819, see Variation), smooth, slender and tapering, each with short ceratophores, arranged in a shallow arc on posterior margin of prostomium. Antennae slightly longer than palps, about 1.5x longer than prostomium. Eyes absent (not visible in live animals or preserved specimens; Fig. 8B, C). First peristomial ring about 2.5x longer than second one dorsally, with shallow notch on anterior margin, ventrally. Peristomial ventrolateral lips laterally slightly elevated and marked by a longitudinal incision following line of ventral prostomium (Fig. 8C).

Maxillary apparatus not everted in holotype or paratypes; dissected out from the holotype. Maxillae with carriers with four paired elements and one single one, formula as follows: MF = 1+1, 4+5, 7+0, 4+4 1+1 (Fig. 9A). MI approximately 2.2x longer than maxillary carrier; carriers rectangular anteriorly, triangular posteriorly, with a pair of oval wings situated at posterolateral margins. MI forceps-like, without attachment lamellae; well-developed, sub-right-angle falcal arch. Closing system approximately 5x shorter than MI. Ligament between MI and MII rectangular, dark. MII wide, without attachment lamella, teeth triangular, recurved, and distributed in anterior half of plate. Ligament between MII and MIII absent (or not sclerotized). Unpaired MIII arched with 7 teeth (Fig. 9B), slightly shorter than right MIV, curved forming part of distal arc; with recurved, equal-sized triangular teeth; short attachment lamella in centre at base, elongate, light brown (Fig. 9B). Left MIV short (2/3 the size of right MIV) with wide, rounded base, teeth approx. equal in size; attachment lamella black, boomerang shaped; right MIV with teeth triangular, recurved, decreasing in size slightly posteriorly; attachment lamella black, large, sub-triangular, best developed anteriorly (Fig. 9B). MV, paired, rectangular (as long as wide), with a broad cutting edge, and no clearly defined teeth (but following tradition to score as 1+1) (Fig. 9B). MV and anterior edge of MIV calcified, white. Mandibles (Fig. 9C) dark, with outer edges calcified, visible dorsally; slightly shorter than MI plus carriers; distinct cutting plates absent.

First few parapodia located below middle line of body wall but gradually positioned dorsally to about midline in subsequent segments. Notopodial cirri slender, tapering, faintly annulated, more so anteriorly (Fig. 10A), about 3 x length of post-chaetal lobe anteriorly reducing to two times its length in mid and posterior segments (Fig. 10C–F); ventral cirri, smooth conical, anterior ones longer, intermediate in length between notopodial cirri and post-chaetal lobe, from chaetiger 8 only slightly longer than post-chaetal lobes (Fig. 10B). Lateral sense organs not observed. Chaetal lobes comprising a low pre-chaetal lip and a tongue-like post-chaetal lobe. Branchiae palmate (Fig. 10B–F), commencing from chaetiger 40 and continue to near end; number of filaments increasing from 1 or 2 anteriorly to max. 5 filaments in mid-body; filaments of equal length, similar in length to notopodial cirri anteriorly, increasing to 2–3 times longer where maximally developed in mid-posterior body. Branchiae appear ciliated and vascularised at base where best developed (Fig. 10B–F). Ventral cirri thicker than notopodial cirri; with slightly inflated bases except for anterior-most ones; about 2/3 as long as notopodial cirri throughout.

Neuroaciculae black with paler blunt tips, 3 per parapodium in anterior chaetigers, 1 or 2 per parapodium in middle and posterior chaetigers. Supra-acicular chaetae include a superior fascicle of limbate chaetae, with fine basal spinelets (only visible under SEM; Fig. 11C) and an inferior row of pectinates; limbate chaetae present from first chaetiger, extending to near pygidium, maximum up to 30 in anterior chaetigers. Pectinate chaetae commencing from at least chaetiger 2, extending at least to chaetiger 180; up to 6 per parapodium. Pectinates with four types identified: anodont-narrow-long (ANL; Fig. 11A) having 4–12 teeth; isodont-narrow-long (INL; Fig. 11B, E, F) having 18–24 teeth, isodont-wide-short (IWS; Fig. 11F) having 23–27 teeth (posterior parapodia only), and isodontwide-long (IWL; Fig. 6F) having 4–5 teeth (posterior only).

Subacicular chaetae include compound spinigers with fine spinelets on shaft (except tip, which is smooth) and base of blade, the latter concentrated on the two sides of the slightly flattened blade (only visible under SEM; Fig. 11D) and subacicular hooks (Fig. 10E, F, F’). Compound spinigers commencing from first chaetiger and continue to near pygidium, with long, tapered blade bearing bilateral fine serrations and serrated shaft (Fig. 11D); 2 different blade lengths per parapodium (longer ones about 1.5x length of shorter ones); about 40 chaetae where maximally developed in anterior-midbody parapodia. Subacicular hooks amber to black, commencing from anterior chaetiger 55 (range for all types) to near end and inferior to bundle of spinigers, one in every parapodium; slightly thinner than aciculae; subacicular hooks unidentate (Fig. 10E, F, F’).

Pygidium (paratype AM W.54820) round, dorsally positioned, with two pairs of tapering pygidial cirri attached at ventral edge, dorsal pair about 7–8 x longer than ventral pair, which are less than pygidial diameter.

Variation. The paratype material, all sequenced, comprises (1) extreme posterior region (AM W.54821), (2) a medium-large specimen (5 mm wide at chaetiger 10), probably about half complete (head missing central antenna) (AM W.54819), and (3) a large specimen, with anterior 1/5 or so missing and a maximum body width about 9 mm, about 13 cm long about 370 chaetigers; whole animal estimated to be 400 chaetigers (AM W.54820). First peristomial ring about 2.5–3.0x longer than second one dorsally. Branchiae from chaetiger 30, maximum number branchial filaments, 5–7; subacicular hooks from chaetiger 41, unidentate; maximum number of aciculae, 3–4. The missing median antenna of paratype AM W.54810 is curious because it is unlikely the result of damage, as there is no sign of tissue damage—the tissue at the base of the prostomium (under the overhanging peristomium) where the median antenna would normally arise is smooth. We conclude that the missing antenna is most likely a developmental abnormality or damage that occurred during the early stages of development.

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Etymology. Marphysa tompaulingi sp. nov., is named after Tom Pauling, AO KC, former Administrator of the Northern Territory, Australia, whose interest in fine art and museum science, particularly evolutionary biology, sparked a close friendship with CJG. “We feel Tom would be absolutely honoured to have a new species of seaworm named after him. Tom was a man whose gravitas was only dwarfed by his humility. This would surely sit as one of his proudest moments.” [Zoe Passmore (nee Pauling) and Fred Pauling]. The type locality of the new species is close to the family home of Tom and Tessa Pauling.

Habitat. Type specimens all collected in mid-channel muddy sand at the mouth of the Ludmilla Creek, Darwin. Although co-occurring in the same estuary creek as M. mossambica, as reported by Glasby & Hutchings (2010), the two species have distinct habitats, with the latter restricted to mangrove sediments (higher proportion of mud) and rotting timber and among roots of Rhizophora stylosa Griff.

Distribution. The species is known only from the muddy-sand channel at the mouth of Ludmilla Creek, East Point Reserve, Darwin (Northern Territory, Australia).

Remarks. Marphya tompaulingi sp. nov., is most closely related to M. iloiloensis Glasby, Mandario, Burghardt, Kupriyanova, Gunton & Hutchings, 2019 and M. setiuensis Che Engku Abdullah, Idris, Fahmi, Flaxman & Hutchings, 2024 (Fig. 1). All these species share compound spinigers in the subacicular fascicle of all parapodia and unidentate subacicular hooks. However, M. tompaulingi sp. nov. may be distinguished from these species as follows: M. tompaulingi sp. nov. is a more robust worm than M. iloiloensis, M. setiuensis, M. honkongensa Wang, Zhang & Qiu, 2018 and M. merchangensis Che Engku Abdullah, Idris, Fahmi, Flaxman & Hutchings, 2024 (the new species is almost twice as wide for a similar number of chaetigers), lacks a pair of eyes (present in M. iloiloensis, M. merchangensis and M. setiuensis), lacks a shallow notch on anteroventral margin of the first peristomial ring (present in M. iloiloensis); has 7 teeth on MIII in the new species (only 4–5 teeth in M. iloiloensis and 4–6 teeth in M. setiuensis), branchiae start quite late in the new species (chaetiger 30–40) compared to chaetiger 16–20 in M. iloiloensis, 15–35 in M. hongkongensa, 16–27 in M. merchangensis and 15–25 in M. setiuensis, and finally the relative lengths of the pygidial cirri, in which the dorsal ones are 7–8x longer than the ventral ones in the new species, but only 2–4x longer in the other three species. A comparison of pectinate chaetae between the four species is difficult because of the current non-quantitative methods of characterising them and the likely variation of each type along the body; nevertheless, the new species has four types of pectinates, as does M. honkongensa, and M. setiuensis compared to three types in M. iloiloensis and five types in M. merchangensis.

Table 3 shows a broader comparison of the key characters of M. tompaulingi sp. nov. with other species of the Marphysa B2 sensu Fauchald (sanguinea group), having unidentate subacicular hooks (a convenient and easy way to split the large M. sanguinea group, although some species with intermediate hook morphology exist—see Table 3 caption). In the appearance of the head (presence of a deep anterior notch (or sulcus), and proportions of head appendages (palps and antennae)), the new species bears a superficial resemblance to M. furcellata Crossland, 1903, M. hongkongensa, M. iloiloensis, M. kristiani Zanol, da Silva & Hutchings, 2016, M. parishii Baird, 1869, and M. tripectinata Liu, Hutchings & Sun, 2017. However, the new species may be differentiated from M. iloiloensis, M. kristiani, and M. parishii, which have a pair of eyes (lacking in the new species); from M. furcellata and M. tripectinata by the start of the subacicular hooks on chaetiger 30 and 170, respectively (vs. 41–55 in the new species) and from M. hongkongensa, in the teeth count and symmetry of MIV (4+8, asymmetrical), but 4+4 (symmetrical) in the new species.