Neanthes adriangloveri, 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 : 182-185

Neanthes adriangloveri sp. nov.

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Fig. 14

Neanthes sp. 2 . Gunton et al., 2021: 70–71, fig. 15E, F

Holotype: AMW.53703, 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.

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 withreddishiridescentcolouration ( 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 pairof palps, withrobust cylindricalpalpophores andsmaller 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 twiceas long asthe 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.

Pharynx with smooth brown jaws with 9 teeth on cutting edge. Paragnaths all conical, arranged as follows: Area I—3 paragnathslongitudinally aligned; II—16–17 paragnaths ina patchof 3 rows; III—clusterof>60 paragnathsinrectangular patch 4–5 rows deep; IV—cluster of>30 paragnaths in each triangular patch; V—none; VI—circular cluster of 7–9 paragnaths; VII–VIII—>120 paragnaths in two bands, with slightly smaller paragnaths distally; bands joined by a series of paragnaths in the pharyngeal grooves (absent on the ridges).

First two chaetigers sub-biramous (notoaciculae absent), following biramous (with two acicula) ( Fig. 14C–E ). Dorsal cirri on sub-biramouschaetigers slightlylonger and inserted at base of dorsal notopodial ligules. Dorsal notopodial ligule and ventral notopodial ligules similar conicalshape and size, slightly longer than neuropodial ligules. Ventral cirri of a similar length to ventral neuropodial ligules.

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 lengthof 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 extendingjust short of corresponding ligule ( Fig. 14E ).

Chaetae of three main types: homogomph and heterogomph spinigers and heterogomph falcigers ( Fig. 14F–J ). Blades of spinigers finely serrated ( Fig. 14F ), blades of falcigers unidentate (with a tendon), finely serrated along their entirelength, 20–30 teeth ( Fig. 14G–I ). Their presence/ absence and number changing throughout the body. Each ramus with dark internal acicula ( Fig. 14C–E ); notoaciculae slightly curved distally; neuroaciculae curved almost 90° distally. In anterior parapodia (represented by chaetiger 5) the chaetae as follows: notochaetae all supra-acicular, 11 per fascicle all homogomph spinigers; supra-acicular neurochaetae consisting of 12 homogomph spinigers and 7 heterogomph falcigers; sub-acicular neurochaetae composed of 3 heterogomph spinigers and 17 heterogomph falcigers. In mid-body parapodia (represented by chaetiger 35) the chaetae are as follow: notochaetae all supra-acicular, 7 per fascicle all homogomph spinigers; supra-acicular neurochaetae consisting of 12 homogomph spinigers and 3 heterogomph falcigers; sub-acicular neurochaetae composed of 6 heterogomph spinigers and ~3 heterogomph falcigers. In posterior parapodia (represented by chaetiger 48) the chaetae as follows: all notochaetae homogomph spinigers, 5 per fascicle; supra-acicular neurochaetae composed of 10 homogomph spinigers and 2 heterogomph falcigers, sub-acicular neurochaetae composed of 5 heterogomph spinigers and 4 heterogomph falcigers ( Fig. 14J ).

Pygidium not observed (missing) on holotype AM W.53703.

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

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, Fujiwara, & Sumida, 2017 , Neanthes abyssorum Hartman, 1967 , Neanthes kermadeca ( Kirkegaard, 1995) , and Neanthes typhla ( Monro, 1930) . The eyes of N. adriangloveri sp. nov. are also different from those of the deep-sea Neanthes species with large or four clearly visible eyes, such as Neanthes goodayi Drennan, Wiklund, Rabone, Georgieva, Dahlgren, & Glover, 2021 and Neanthes suluensis Kirkegaard, 1995 . In comparison to the geographically close deep-sea Neanthes species Neanthes articulata Knox, 1960 (type locality: Chatham Islands), Neanthes kerguelensis ( McIntosh, 1885) (Kerguelen Islands) , Neanthes papillosa ( 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.

Figures

Figure 14. Neanthes adriangloveri sp. nov., holotype AM W.53703. (A) Live specimen, scale bar is 5 mm; (B) detail of prostomium, scale bar is 500 µm; (C) anterior parapodium (number 5), scale bar is 200 µm; (D) mid-body parapodium (number 35), scale bar is 200 µm; (E) parapodium from near end of incomplete holotype specimen (number 48), scale bar is 200 µm; (F) notospinigers (parapodium number 5), scale bar is 20 µm; (G) subneurofalcigers (parapodium number 5), scale bar is 20 µm; (H) supraneurofalcigers (parapodium number 5), scale bar is 20 µm; (I) supraneurofalcigers (parapodium number 35), scale bar is 20 µm; (J) neuropodium of parapodium number 48, scale bar is 100 µm.