Polyodontes australiensis (McIntosh 1885)

Polyodontes australiensis (McIntosh, 1885)

Eupompe australiensis McIntosh, 1885:135, pl. 21: figs. 4, 5, pl. 23: fig. 8, pl. 24: fig. 4, pl. 13A: figs. 2–6.—Benham, 1915:202.

Polyodontes (Eupompe) australiensis.—Buchanan, 1894:446, pl. 27: fig.11A,B.

Polyodontes australiensis.—Hartman, 1939b:82; 1966:361, pl. 36a,b.—Hutchings and Murray, 1984:17, fig. 5.1–5.

MATERIAL EXAMINED.—AUSTRALIA. Near Wednesday Island, NW of Cape York, Queensland, 10°30′S, 142°18′E, 15 m, coral sand, Challenger sta 186, 8 Sep 1874, holotype (BMNH 1885.12.1.107). The Basin, Pittwater, Port Jackson, New South Wales, attached to baited fish hook, Jun 1962, Mrs. C.J. Mom, collector, 1 specimen (AMS 3754, identified by O. Hartman).

TYPE MATERIAL.—Holotype consisting of anterior fragment of 30 segments and small fragment of 3 segments, with total length of 44 mm, and 22 mm wide with setae; setae mostly broken; pharynx not extended and not examined by McIntosh. Specimen from New South Wales consisting of anterior fragment of about 100 segments, 150 mm long, 38 mm wide examined and figured (AMS 3754).

DESCRIPTION.—Body long, tapered anteriorly, dorsally arched in anterior region, flattened ventrally. Dorsum brownish, not banded. Anterior few pairs of elytra covering dorsum, following ones leaving middorsum uncovered; first pair of elytra with anterolateral part extended and lobulated; elytra rather delicate, transversely elongate, with shallow lateral fold, opaque, brownish, minutely areolate (Figure 73C–F; McIntosh, 1885, pl. 21: fig. 4).

Prostomium bilobed, with bulbous ommatophores having slightly narrower neck and distal lenses; median antenna with ceratophore attached near anterior notch, extending posteriorly as slightly raised ridge, style with filamentous tip extending to tips of ommatophores; posterior pair of small eyespots lateral to ceratophore; lateral antennae inserted ventral to ommatophores with only distal tips visible dorsally; palps elongate, tapered, smooth, splotched with pigment on dorsal sides (Figure 73A). Tentacular segment visible dorsally; tentaculophores lateral to prostomium, each with 2 acicula, bundle of capillary setae, and pair of dorsal and ventral tentacular cirri, with styles similar to median antenna, with basal and subdistal rings of pigment (Figure 73A,G).

Second segment with first pair of elytrophores, ventral buccal cirri larger and longer than following ventral cirri, and biramous parapodia; notopodium conical, with bundle of long, finely spinous, capillary notosetae; neuropodium rather thick, truncate, with arched vertical row of neurosetae; neurosetae emerging in groups from series of slit-like openings; neurosetae all similar, slender, finely spinous, tapering to capillary tips, lower ones more slender (Figure 73H–J). Distal border of pharynx with 15 pairs of papillae, middorsal one longer than others, on wide base, midventral one represented by wide base; 2 pairs of hooked jaws, each with 6 or 7 lateral teeth (Figure 73B). Ventral upper lip medial to 2nd parapodia, lateral and lower lips medial to parapodia of segments 3–8 (McIntosh, 1885, pl. 21: fig. 5).

Third segment with first pair of dorsal cirri with short cirrophores and styles extending to tips of setae; notopodium and notosetae similar to those of segment 2; neuropodium with few upper slender neurosetae similar to those of segment 2, middle stout neurosetae missing, lower group of neurosetae, within prominent ventral bract, with prominent spinous rows basally and close-set finely spinous rows on tapering distal tips (Figure 73K–N). Parapodia of segments 4–8 with smaller notopodia and larger neuropodia, with 3 groups of neurosetae, middle stout acicular ones with slightly hooked smooth tips (Figure 73O–R).

Beginning with segment 9, notopodium wide, truncate, flattened, on anterodorsal side of larger neuropodium, with notoaciculum, spinning glands, short notosetae emerging from inner lower side of notopodium, and slit for emergence of spinning fibers (hidden from view unless notopodium pulled back); lower group of neurosetae, within anteroventral bract, numerous, similar to more anterior neurosetae; middle group of neurosetae stout, acicular, upper group of neurosetae, emanating from low dorsoanterior bract, hidden by notopodium, of 2 types: (a) long, wide basally, with numerous spinous rows on tapering capillary tips; (b) shorter, extending only slightly beyond notopodium, more numerous, slender, with widely-spaced spinous rows, tapering to fine tips (Figure 73S–U).

Middle parapodia becoming larger, with more numerous neurosetae of same types; dorsal cirri with wide cirrophores and short, wide styles extending slightly beyond neuropodia (Figure 74A–C; McIntosh, 1885, pl. 23: fig. 8, pl. 13A: figs. 2–6). Digitiform branchiae on anterior and posterior bases of elytrophores and dorsal cirrophores, beginning about segment 10, more numerous on segments 12–30 or so, then fewer and larger more posteriorly (Figure 74A,B,E). Ventrally, up to 3 or 4 oval branchial areas medial to ventral cirri beginning on segment 11. Some of stout acicular neurosetae in more posterior parapodia with aristae and subdistal spines on one side (Figure 74D–F).

DISTRIBUTION.—Australia–Queensland, New South Wales, Victoria (Bass Strait). In 10 to 119 meters.