Synelmis knoxi Glasby, 2003

Glasby, Christopher J. & Marks, Shona, 2013, Revision of the genus Synelmis Chamberlin, 1919 (Annelida: Phyllodocida: Pilargidae) in Australia, Zootaxa 3646 (5), pp. 561-574 : 563-567

Synelmis knoxi Glasby, 2003

( Fig. 1 A–C)

Synelmis knoxi Glasby, 2003:12 –14 fig. 22A–H.

Synelmis gibbsi . —Hocknull & Glasby, 2009: 544.

Type locality. Bay of Islands, New Zealand, 46– 73 m.

Material examined. Arafura Sea, coll. CSIRO RV Southern Surveyor cruise 05-205, 10–17 May, 2005, Stn DR001, muddy sand, 9º 24.933’S 134º 18.619’E, 89 m, NTM W21982 (1 specimen); Stn GR027, muddy fine to medium sand, some gravel, 9º 24.097’S 134º 11.675’E, 87.2 m, NTM W21983 (1 specimen); Stn GR056, slightly muddy coarse sand & gravel, 9º 5.924’S 133º 11.891’E, 126 m, NTM W21984 (1 specimen); Stn GR057, slightly muddy coarse sand & gravel, 9º 5.925’S 133º 11.897’E, 126 m, NTM W21985 (1 specimen), Stn GR060, slightly muddy sandy gravel, 9º 10.774’S 133º 24.82’E, 129 m, NTM W21986 (1 specimen). Darwin Harbour, 12º 33.15’S 130º 51.38’E, 13 m, NTM W10294 (2 specimens), 12º 34.88’S 130º 51.77’E, 11 m, NTM W10295 (10 specimens), 12º 38.88’S 130º 45.00’E, 4 m, NTM W10293 (4 specimens).

Queensland, Abbot Point, 19m, 19.9 º S 148.1 º E, coll. CRC Reef Research Centre Ltd, 15 Jul 1998, AM W30653 (1 specimen).

Southern Ocean, Great Australian Bight, Stn SARDI-GAB-2006 50, coll. 20 Oct 2006, 33º 21.50’S 131º 6.30’ E, 150 m, MV F 160924 (1 specimen); Stn SARDI-GAB-2006 52, coll. 20 Oct 2006, 33º 22.50’ S 131º 01.367’ E, 177 m, MV F 160925 (1 specimen); Stn SARDI-GAB-2006 39, coll. 19 Oct 2006, 33º 14.267’ S 130º 57.90’ E, 117 m, MV F 160926 (1 specimen). Off Tasmania, coll. K. Gowlett-Holmes, R. Wilson et al., 16–21 Apr 2004, CSIRO RV Southern Surveyor Cruise 404, Bass Strait, King Island Canyons, Stn 25, 39º 49.533’ S 143º 15.983’ E, 196 m, MV F109463 (1 specimen); Stn 35, King Island Canyons, 39º 48.41 S, 143º 0 8.48 E, 348m, MV F124099 (7 specimens); Stn 52, Ling Hole, 41º 19. 48 S, 144º 19.60 E, 163m, MV F124081 (5 specimens).

Western Australia, CSIRO RV Southern Surveyor Cruise 07-2005, 7 Aug 2005, off Pelsart Island, near Geraldton, 29º 00.167’ S 113º 46.433’ E, 409 m, Stn 122, 409m, MV F156434 (1 specimen); Stn 153, off Bunbury region, 33º 00.00’ S, 114º 34.733’ E, 399 m, MV F166528 (1 specimen). CSIRO RV Southern Surveyor Cruise 10- 2005, 24 Nov –5 Dec 2005, Stn 104, off Zuytdorp, 27º 03.10’ S 113º 13.317’ E, 97 m, MV F 161000 (1 specimen); Stn 0 57, off Pt Hillier, 35º 22.417’ S 117º 11.817’ E, 196 m, MV F161746 (1 specimen); Stn 0 35, off Bald Island, 35º 11. 433’S 118º 38.70’ E, 157– 147 m, MV F 161747 (1 specimen).

Description. The following description is based on MV F 160925, and variability assessed based on 11 other specimens. Size ranged from 16 (5.1–44) mm long, 0.50 (0.30–1.1) mm wide at widest point (including parapodia) for 78 (36–102) chaetigers.

Body yellow–white, subcylindrical, slender, width similar throughout, body surface smooth, shiny and iridescent ( Fig. 1 A). Lateral subdermal pigmented glands present between chaetigers 1 to 5– 10 in groups of 1–4 spots ( Fig. 1 B), thereafter a single sickle shaped spot in each segment posterior to dorsal cirrus; pigment often faded and glands not visible.

Prostomium wider than long, anteriorly subacute. Eyes present, one pair (each one of the pair may be split into up to 5 small eyespots), located laterally at mid-level of prostomium. Palps biarticulated, free from each other making deep anterior notch, palpostyles button-like. Ventrolateral palpal papilla present, longer than wide. Paired lateral antennae present, located anteriorly, close to bases of palps; subulate. Median antenna present, subulate, 1.2 times as long as lateral antennae (approx.), extends back to chaetiger 1. Pharynx smooth, lacking tooth-like structures, distal ring papillae, and subdistal papillae. Posterior brain lobes visible, tapering to a point posteriorly, pigment spots absent. Nuchal organs not visible. Tentacular cirri present, 2 pairs, same length as dorsal cirri ( Fig. 1 B).

Parapodia sub-biramous. Notopodial lobe low, indistinct. Dorsal cirri present, subulate, similar in size and shape throughout, about 2–3 times length of corresponding neuropodium. Dorsal cirri of chaetiger 1 similar length to subsequent dorsal cirri. Notochaetal spines emerge at dorsal base of dorsal cirrus, present from chaetiger 5, straight to slightly curved anteriorly, becoming more bent posteriorly. Notoaciculae present, 2 per parapodium, knob-tipped or tapering. Neuropodial lobe low, rectangular, about same width as base of dorsal and ventral cirri in mid-body chaetigers. Ventral cirri present from chaetiger 1, basal, subulate. Neurochaetae comprise capillary-like chaetae and short, asymmetrical furcate chaetae (not visible in all parapodia and all specimens). Capillary-like neurochaetae include finely denticulate (along one edge) and smooth types in each parapodium (ratio of two types varies in different populations; in eastern and southern Australia greater number of denticulate types, in northern and western Australia mostly smooth types), 5–6 per neuropodium. Neuroacicula absent.

Pygidium spherical, tapered. Lateral anal cirri present, filiform, located on outside margin of pygidium ( Fig. 1 C). Mid anal cirri absent. Anus opening dorsally.

Remarks. Material identified as Synelmis gibbsi by Hocknull & Glasby (2009) is re-identified here as S. knoxi . The two species are very similar, with the only differences according to Salazar-Vallejo (2003) being the longer relative length of the median antenna and dorsal cirri of chaetiger 1 in S. gibbsi . In the present specimens the dorsal cirri of chaetiger 1 are not appreciably longer than those following, as in S. knoxi . The absence of neuroaciculae in S. knoxi (noted by Glasby (2003)) is confirmed as a good species specific character; it can be used to distinguish this species from other Australian Synelmis . However, the condition in S. gibbsi was not reported by Salazar- Vallejo (2003).

The new material examined in this study extends considerably the distribution of S. knoxi from New Zealand to include the continental shelf and slope of most of Australia. Both S. knoxi and S. gibbsi exhibit a wide range of depth distribution, 19–409 m for the former and intertidal to 831 m for the latter. This fact and the wide distribution of both species suggest that cryptic species may be present.

Distribution. New record for Australia; inshore and offshore on continental shelf and slope. Also New Zealand.

Figures

FIGURE 1. Synelmis knoxi, MV F 156434, A, entire animal, head upper left; note iridescent cuticle; B, head end and anterior region, lateral view; C, tail end, dorsolateral view.