Polygordius arafura Avery, Ramey & Wilson, 2009, sp. nov.

Polygordius arafura sp. nov.

Figure 1 A–F

Material examined. Holotype: Australia: Northern Territory. Arafura Sea: Stn SS05/2005 007GR011, 9°50.126' S 135°17.766' E, 4 May 2005, 83 m, calcareous poorly-sorted muddy fine sand, (NTM W22253). Paratypes: same data as for holotype, spirit specimens, 1 paratype NTM W22254, 1 complete paratype and 3 fragments NTM W20934. Paratypes: Australia, Northern Territory, Arafura Sea: Stn SS05/2005 002GR002 9°47.986' S 135°22.007' E, 91.2 m, 1 May 2005, 4 paratypes: NTM W22248, NTM W22249, NTM W22250, NTM W22251, and one SEM stub paratype NTM W22252; 2 paratypes, MV F165642, F165643; 1 paratype, USNM 1121878. One paratype: Australia: Northern Territory. Arafura Sea: Stn SS05/2005 012GR019, 9° 47.593’ S 135° 16.636’ E, 5 May 2005, 85 m, muddy sand, USNM 1121879.

Non-type material: Australia: Northern Territory. Arafura Sea: Stn SS05/2005 012GR019, 9° 47.593’ S 135° 16.636’ E, 5 May 2005, 85 m, muddy sand, 2 spirit specimens (NTM W20939); Stn SS05/2005 005GR007, 9° 50.47’ S 135° 16.099’ E, 4 May 2005, 80 m, muddy sand, 1 spirit specimen and 2 specimens on one SEM stub (NTM W20941); Stn SS05/2005 002BS002, 9° 47.947’ S 135° 22.024’ E, 1 May 2005, 92 m, moderately sorted calcareous medium sand, 1 specimen (NTM W20936); Stn SS05/2005 006GR009, 9° 50.356’ S 135° 20.888’ E, 4 May 2005, 87 m, poorly-sorted muddy fine calcareous sand, 1 specimen (NTM W20937); Stn SS05/2005 011GR018, 9° 47.768’ S 135° 16.935’ E, 5 May 2005, 84 m, muddy sand, 1 specimen (NTM W20942); Stn SS05/2005 009GR015, 9° 49.294’ S 135° 19.599’ E, 4 May 2005, 83 m, 5Y 4/ 2, poorly-sorted calcareous, muddy medium sand, 1 specimen (NTM W20940); Stn SS05/2005 003GR005, 9° 52.788’ S 135° 21.891’ E, 4 May 2005, 69 m, Sandy Mud, 1 specimen and wholemount microslide (NTM W20938); Stn SS05/2005 010GR017, 9° 48.774’ S 135° 15.412’ E, 5 May 2005, 82 m, sandy mud GLEY 1 4/ 10 Y, 1 specimen and wholemount microslide (NTM W20935).

Distribution. Australia. Northern Australia, Arafura Sea, Gulf of Carpentaria (Fig. 1 F). Habitat marine, shelf 69–92 m, mostly from poorly-sorted sediments.

Description. Size range of material examined 2.4–11.6 mm long, 0.08–0.18 mm wide (n =15), inflated pygidial region about 1.2 times maximum body width.

Prostomium conical (0.06–0.12 mm long), pointed at tip (Fig. l A). Eyes absent. Paired antennae 0.04–0.06 mm long, almost attached to each other at the base, and remain parallel for some distance (Fig. l B). Ratio of antenna to prostomium length 0.5–0.86. Head fold deep (Figure l A). Dimensions of holotype given in Table 2.

Pygidium cylindrical, minimally inflated (about 1.2 times body width), pygidial glandular pads absent (Fig. l C, confirmed by examination of whole mounts using compound microscope). Pygidial appendages absent. Anal opening central; anal lobes present; 7–8 approximately equal-sized lobes (Fig. l D). Epidermis of pygidium lacking cilia (Fig. 1 E). Neither eggs nor sperm could be seen in any specimen examined in temporary or permanent whole body mounts.

Discussion. Table 1 groups all known Polygordius species based on presence or absence of pygidial glands, and subterminal or terminal pygidial appendages. Polygordius arafura sp. nov. is similar to three other species that also lack pygidial glands and pygidial appendages. Of these Polygordius uroviridis is easily distinguished from Polygordius arafura sp. nov. by its inflated or bulb-like pygidium, the presence of eyes, and a dark band of pigment encircling the middle region of the pygidium. Polygordius arafura sp. nov. is most similar to Polygordius jouinae and Polygordius triestinus Hempelmann, 1906. Polygordius arafura sp. nov., has shorter antennae (0.04–0.06 mm) than P. jouinae (0.10–0.15 mm), and the length ratio of antennae to prostomium is ~0.5 for P. arafura sp. nov. and ~1 for P. jouinae (see also Table 2). Moreover, Polygordius arafura sp. nov. has a deep head fold while P. j o u i n a e and P. triestinus have a shallow head fold. Although no head fold has been described for P. jouinae, examination indicated that the head fold is shallow. Finally, P. jouinae has a distinctly ciliated pygidial region (Ramey et al. 2006: 1029 figure 2F) whereas P.arafura sp. nov. has the pygidial region bare of cilia (Fig. 1 E). The species description for P. triestinus is incomplete for many characters (Table 2) and Ramey et al. (2006) were unsuccessful in locating type material. Moreover, P. triestinus has not been reported since the original description and is not present in benthic samples taken from the Gulf of Trieste from 1966–2003 (Ramey et al. 2006).

Etymology. The specific name arafura is derived from the name of the indigenous inhabitants of the Molluccas, "the people of mountains", a name subsequently also given to the Arafura Sea, the type locality of P.arafura sp. nov.

Pygidial appendages Pygidial appendages subterminal Pygidial appendages terminal absent

Pygidial glands / P. antarcticus P. appendiculatus P. eschaturus glandular pads present P. erythrophthalmus P. k i a r a m a sp. nov. P. eschaturus brevipapillosus

P. lacteus P. l e o P. madrasensis

P. neapolitanus

P. pacificus

P. pacificus floreanensis

P. triestinus j

Pygidial glands / P. arafura sp. nov. glandular pads absent P. jouinae

P. triestinus h

P. uroviridis

Undetermined P. vil lot i P. ijimai