Chone australiensis Hartmann-Schroder 1979

Chone australiensis Hartmann-Schröder, 1979

Figure 4

Chone australiensis Hartmann-Schröder, 1979: 151, Figs 363–367.

Material examined. Type material. Australia [ZMH P–15534, holotype], Broome, 8.9.75, Probe 5.

Description. Colour, body shape, and size. Body cream coloured. Holotype complete. Body length 4 mm, width 0.25 mm. Tube unknown.

Branchial lobes and branchial crown. Insertion of the branchial crown exposed beyond collar dorsally (Fig. 4 B). Branchial crown length 2 mm. Five radiolar pairs. Radioles with long pinnules. Radiolar tips extremely long (Figs 4 A–B). The palmate membrane extends a half the length of the branchial crown. Lateral flanges very narrow. Dorsal lips triangular, erect, without mid-rib. Ventral lips rounded, small.

Peristomium. Anterior peristomial ring lobe not exposed beyond collar, distally entire, triangular. Posterior peristomial ring collar: antero-dorsal margins entire (Fig. 4 B), lateral margins folded (not incised), ventral margin sligthly higher than dorsal; entire length of mid-dorsal collar margin forms a narrow gap (Fig. 4 B). Dorsal pockets not developed. Ventral shield of collar horseshoe-shaped, three times wider than long, swollen (Fig. 4 A). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 1:1.

Thorax. Chaetigers 2 to 8: notopodia– two irregular rows of elongate, narrowly hooded chaetae (Figs 4 C, E); one anterior row with bayonet chaetae; two posterior rows with symmetrical; paleate chaetae with a medium-sized mucro (Fig. 4 D); neuropodia– one row of acicular uncini per torus, main fang surmounted by four rows of teeth equal in size, occupying half of the main fang length. Glandular ridge on chaetiger 2 very narrow.

Abdomen. Abdominal segments: 32. Anterior segments: two transverse rows of elongate, narrowly hooded chaetae, chaetae from the upper row half as long as chaetae in lower row; uncini with the main fang surmounted by five regular rows of teeth in frontal view, equal in size, occupying one-half the length of main fang, main fang not extending beyond breast, breast rectangular. Posterior segments: 2–3 very elongate, narrowly hooded chaetae; modified uncini with the main fang surmounted by six to seven regular vertical rows of teeth equal in size, occupying three-quarters the length of main fang, main fang not extending beyond breast, breast rectangular. Pygidium with a triangular posterior margin (Fig. 4 A).

Gametes. Holotype inmature.

Methyl green staining. Ventral collar shield not stained (Fig. 4 A); thorax with epidermis completely glandular, stains uniformly, dorsal and ventrally (Figs 4 A–B); abdomen less coloured (Fig. 4 A).

Remarks. Chone australiensis was described as having the lateral collar margin incised, as Hartmann- Schröder (1979) shows in her figure 364; however, re-examination of the holotype shows that the lateral margin of collar is entire. The drawings of Hartmann-Schröder were made with the holotype mounted in a slide, where the collar is folded, not incised.

Chone australiensis and C. normani have the anterior abdominal uncini with equal sized teeth above the main fang. In C. australiensis, the ratio of posterior peristomial ring collar length versus chaetiger 2 length is 1:1 (1.5: 1 in C. normani); the radiolar flanges are narrow (broad in C. normani); extra long radiolar tips (medium-sized in C. normani); the anterior peristomial ring lobe is triangular, not exposed beyond collar (bilobed, exposed beyond collar in C. normani) and short mucro (long in C. normani) (Table 2).