Namanereis pilbarensis, Glasby & Fiege & Damme, 2014

Glasby, Christopher J., Fiege, Dieter & Damme, Kay Van, 2014, Stygobiont polychaetes: notes on the morphology and the origins of groundwater Namanereis (Annelida: Nereididae: Namanereidinae), with a description of two new species, Zoological Journal of the Linnean Society 171 (1), pp. 22-37 : 24-26

NAMANEREIS PILBARENSIS SP. NOV.

( FIGS 1A–C , 2A–G , 3A–G )

Specimens examined

Holotype: Australia, Pilbara region , Site PSS330 , Duffers , Ashburton River catchment, 23°47.27′S, 117°48.41′E, 298 m asl, approx 25 km north of Pingandy Road on the Ashburton Downs – Meekatharra Road, coll. M. Scanlon & J. Cocking, 21.vii.2004 ( WAM V8206 ) . Paratypes: Australia, Pilbara region , Site PSS016 , Robe , Onslow Coast Basin, 21°34.88′S, 115°52.23′E, 54 m asl, bore on Yarraloola Station, coll. M. Scanlon & J. Cocking, 14.xi.2002, two specimens ( NTM W19176), one specimen ( NTM W25486), one specimen ( NTM rated with single terminal and seven subterminal teeth. Notochaetae absent. Neurochaetae in type C arrangement as defined by Glasby (1999). Supraneuroacicular falcigers of chaetiger 10 with blades about 4.9 times longer than width of shaft head, blades finely serrat- ed, seven to 11 teeth. Subacicular neurochaetae include heterogomph falcigers, heterogomph spinigers, and heterogomph pseudospinigers.

W25487); Site PSS309 , Wickham Well , De Grey River catchment, 22°2.27′S, 120°35.24′E, 410 m asl, approx. 50 km north-west of Noreena Downs Homestead, coll. M. Scanlon & J. Cocking, 15.vii.2004, four specimens, few plus headless fragments ( SMF 22369, 2 cs and fragments; SMF 22370: SEM stub 1203, 1 cs; SMF 22371: SEM stub 1204, 1 cs); Site FMG13, Dandy Well , De Grey River catchment, 22°11.55′S, 119°53.22′E, 491 m asl, Bonney Downs Station, well located to creekline, coll. M. Scanlon & J. Cocking, 12.iii.2005, one specimen ( SMF 22372: SEM stub1202, 1 cs–p) .

Type locality

Duffers, Ashburton River catchment, Pilbara, Australia.

Etymology

Species name based on region of occurrence.

Diagnosis

Prostomium not cleft anteriorly. Antennae cirriform. Eyes absent. Three pairs of tentacular cirri. Jaws ser- Description

Body elongate, uniform width along most of body, slightly tapering over far posterior body ( Fig. 1A, C ). Dorsal side convex, ventral side flattened. Colour in alcohol specimens yellow-white, epidermal pigment absent; in life semitransparent ( Fig. 1A ). Holotype cs, 10.5 mm long, 0.9 mm wide at chaetiger 10 including parapodia and chaetae, 78 chaetigers. Paratypes range from 4.4– 4.6 mm long, 0.45–0.50 mm wide, 30–36 chaetigers (N = 3).

Prostomium subtriangular, slightly wider than long with widest part near posterior end; anterior end entire without cleft, shallow dorsal depression present ( Fig. 1B ). One pair of antennae inserted over inner-mid palps; cirriform, extending to level with or just beyond tip of palps. Palps massive, biarticulate. Eyes absent ( Fig. 2A, B ).

Peristomium with three pairs of tentacular cirri with indistinct cirrophores; smooth to slightly wrinkled cirrostyles. Anterodorsal and posterodorsal cirri of about same length, anteroventral slightly shorter. Posterodorsal cirri extending to chaetiger 2 ( Fig. 2A ). Pharynx retracted in holotype, everted in some paratypes. Jaws of paratypes serrated with single terminal tooth and about seven subterminal teeth; proximal-most ones ensheathed ( Figs 2C , 3G ).

Parapodia with conical acicular neuropodial ligule. Dorsal cirri cirriform, increasing in length posteriorly, half length of acicular neuropodial ligule anteriorly, about equal length of acicular neuropodial ligule posteriorly. Ventral cirri anteriorly subulate about twothirds length of neuropodial ligule, posteriorly cirriform and about half length of neuropodial ligule ( Figs 2A, D , 3A, B ).

Notochaetae absent. Neurochaetae in type C arrangement, i.e. supraneuroacicular chaetae consist of one sesquigomph spiniger in postacicular fascicle and one heterogomph falciger in preacicular fascicle. Subneuroacicular fascicle in postacicular position comprising two heterogomph falcigers and one to two distally bifid heterogomph pseudospinigers (rarely heterogomph spinigers) ( Figs 2D, F , 3C–F ).

Supraneuroacicular sesquigomph spinigers with boss about 1.8 times length of collar. Supraneuroacicular falcigers of chaetiger 10 with blades about 4.9 times longer than width of shaft head, finely serrated, eight teeth ( Fig. 2E ). Subneuroacicular falcigers of chaetiger 10 with very finely serrated blades, nine to ten teeth, about 5.1 times longer than width of shaft.

Pygidium tripartite, with small subpointed dorsal lobe and two larger ventral lobes bearing pair of smooth, cirriform anal cirri, equal in length to two to three times the width of pygidium. Anus terminal ( Fig. 2G ).

Remarks

Namanereis pilbarensis sp. nov. was first discovered by Scanlon et al. (2006), identified tentatively as an ‘undescribed marine polychaete’. It can be distinguished from all other members of the genus by having distally bifid heterogomph pseudospinigers. It may be distinguished from other groundwater Namanereis species by the combination of jaws with a single terminal tooth and series of subterminal teeth (the typical nereidid condition) and relatively few (seven to 11) serrations on the supraneuroacicular falcigers ( Table 1). Habitat

Bore holes in cattle pastoral areas intermittently flowing river catchments in the Pilbara, 54–491 m asl, salinity 0.5–1.5 ppt, temperature 28–31 °C.

Distribution

Pilbara, north-west Australia.

Figures

Figure 1. Namanereis pilbarensis sp. nov. A, live specimen, dorsal view; B, preserved specimen (WAM V8206), close up of anterior end, dorsal view; C, preserved specimen (WAM V8206), whole body, dorsal view. Scale bars: A = 0.1 mm; B = 0.05 mm; C = 0.2 mm.

Figure 2. Namanereis pilbarensis sp. nov. Paratypes A–F (SMF 22372), G (SMF 22371). Scanning electron micrograph. A, anterior end, ventrolateral from right side. B, anterior end, dorsal view. C, proboscis with jaws partly everted, anterior view. D, parapodium chaetiger 7, right side, anterior view. E, chaetiger 16, right side, supra-acicular falciger. F, chaetae from chaetiger 10, right side, posterior view. G, pygidium, dorsal view. Scale bars: A−C, G = 100 μm; D = 30 μm; E = 3 μm; F = 10 μm.

Figure 3. Namanereis pilbarensis sp. nov. Holotype A–F (WAM V8206), paratype G (NTM W19176). A, parapodium, chaetiger 32; B, parapodium, chaetiger 60; C, supra-acicular falciger, chaetiger 32. D, heterogomph spiniger, chaetiger 60; E, heterogomph spiniger, chaetiger 32; F, subacicular falciger, chaetiger 32. G, jaw, right side, dorsal view. Scale bars: A = 0.2 mm, B = 0.1 mm; C–F = 0.02 mm; G = 0.05 mm.