Aponuphis danicae, Paxton, 2017

Paxton, Hannelore, 2017, Three new species of Aponuphis (Annelida: Onuphidae) from eastern Australia, Zootaxa 4344 (2) : -

Aponuphis danicae n. sp.

Figure 1F ; 5; Table 1

Type material. Holotype: Incomplete specimen, 11 mm long (54 chaetigers), 0.9 mm wide; New South Wales, Bass Point, 34°36’S – 150°54’E, 65–70 m, 29 Oct–14 Nov 1990, sta. 3-37 (AM W.49485).

Paratypes: One complete specimen, 19.5 mm long (108 chaetigers), 0.8 mm wide (AM W.49486) and one incomplete specimen, 11 mm long (43 chaetigers), 0.9 mm wide (AM W.49487); Bass Point: 34°36’S–150°54’E, 35–40 m, 3 Jan–18 Jan 1991, sta. 4-223.

Additional material examined: Three incomplete juveniles, 4.0– 5.5 mm long (31– 45 chaetigers), 0.3–0.6 mm wide.

Bass Point: sta. 4-223, same data as paratypes (AM W.49488:3).

Type locality. Pacific Ocean , Bass Point, New South Wales; 34°36’S – 150°54’E, depth 65–70 m.

Diagnosis. Brown pigment on peristomium and as dorsal horizontal bands; prostomium anteriorally incised; antennae with 2–4 ceratophoral rings, styles to chaetiger 5–14; 4 pairs of modified parapodia with tridentate short- and long-appendaged pseudocompound hooks; subacicular hooks from chaetiger 12–15; single branchial filament starting from chaetiger 14–26, ending on chaetiger 23–35; fragile mucous tube with attached sand grains.

Description. Freshly preserved specimens overall cream coloured with brown pigment pattern on dorsal surface ( Figs 1F , 5A ); only weakly visible in holotype now: peristomium brown, from chaetiger 1–10 two bands per segment, from chaetiger 7 bands widening laterally, gradually fusing into one median band per segment by chaetiger 15, thereafter becoming progressively paler and narrower, last pale band at about chaetiger 35.

Prostomium wider than long, anteriorly rounded, with slight median incision ( Fig. 5A ). Two pairs of eye spots between frontal lips and palps, and palps and lateral antennae. Ceratophores of palps and antennae short, with 2–3 proximal rings and longer distal ring, palpostyles three times as long as palpophores, reaching chaetiger 2; lateral antennostyles to chaetiger 9–10 (5–14), median antennostyles to 10 (4–10). Nuchal grooves straight with narrow middorsal separation. Peristomial cirri absent.

First 3 pairs of parapodia modified, directed slightly anterolaterally and slightly prolonged ( Fig. 5A ). Prechaetal lobe rounded, very short, hardly protruding from prechaetal fold; postchaetal lobe subulate ( Figs 5B, C ), gradually reduced from chaetiger 10, becoming small knob by chaetiger 20, absent from chaetiger 30. Dorsal cirri initially subulate, becoming smaller and digitiform by chaetiger 20 but remaining as slender cirrus to almost end of body; ventral cirri subulate on anterior 4 chaetigers, then replaced by ventral glandular pads. Branchiae present as single filament ( Fig. 5C ) for relatively few segments, starting on chaetiger 21 (14–26), ending on chaetiger 28 (23– 35).

Tridentate pseudocompound hooded hooks present on anterior 4 chaetigers ( Fig. 5E–G ). Hooks consisting of 2 long-appendaged ( Fig. 5E ) and 2 short-appendaged ( Fig. 5F ) ones; short-appendaged hook in median position slightly thicker than lower one; appendages of all hooks with large distal and median teeth, and small third tooth; hood of median hook of chaetiger 4 with small serrations ( Fig. 5G ). Hardly any pectinate chaetae present, only ones observed present in median body region, slightly oblique with 10–12 teeth ( Fig. 5H ). Limbate chaetae starting at chaetiger 4 as 3 long upper chaetae in addition to pseudocompound hooks ( Fig. 5C ), upper and lower limbate chaetae from chaetiger 5 until lower bundle replaced by 2 bidentate subacicular hooks from chaetiger 15 (12–15) ( Fig. 5D ).

Pygidium with two pairs of very thin anal cirri; dorsal pair as long as terminal 15 segments, ventral pair about one tenth thereof. Mandibles very delicate even in mature animals; cutting plates small, only initial larval mandibles sclerotized ( Fig. 5I ). Maxillae ( Fig. 5J ) lightly sclerotized, maxillary formula: Mx I = 1+1; Mx II = 6+7; Mx III = 8+0; Mx IV = 7+10; Mx V = 1+1. Very thin and fragile mucous tubes with some attached sand grains.

Remarks. The new species is unique in its late origin of branchiae. Other differences to A. annae n. sp. and A. bellani n. sp. have been discussed above and are detailed in Table 1.

Etymology. This species is dedicated to Alexandra Danica Hegedus, with thanks for being a cheerful and helpful laboratory companion.

Biology. Three incomplete juvenile specimens were collected in the same station as the two paratypes; they measure 4.0– 5.5 mm in length for 31–45 chaetigers and 0.3– 0.6 mm in width. The smaller two are abranchiate, but the slightly thicker specimen (0.6 mm width) has tiny branchial filaments on chaetiger 26–27. All three specimens have only three chaetigers with pseudocompound hooks and subulate ventral cirri; subacicular hooks start on chaetiger 11 in all three, but are preceded in the thinnest one by anterior precursor subacicular hooks on chaetigers 4–10.

Habitat and distribution. The new species is only known from the type locality, where it was collected in a depth of 35–70 m.

Figures

FIGURE 1. Diagrammatical dorsal views of anterior ends of Aponuphis spp., showing variations in pigmentation. A, Aponuphis annae n. sp., morph A; B, same, morph B; C, same, morph C; D, same, morph D; E, A. bellani n. sp.; F, A. danicae n. sp.

FIGURE 5. Aponuphis bellani n. sp., scanning electron micrographs. A, specimen in tube; B – D, progressively enlarged image to show microstructure of tube.