Aponuphis annae Paxton 2017, n. sp.

Aponuphis annae n. sp.

Figures 1A–D; 2A–E; 3; Table 1

Material examined. Holotype: Complete specimen, 33 mm long (140 chaetigers), 1.0 mm wide; New South Wales, Bass Point: 34°36’S – 150°54’E, 25–30 m, 03–18 Jan 1991, sta. 4-200 (AM W.49392).

Paratypes: 7 complete specimens, 9–25 mm long (60–130 chaetigers), 0.6–1.0 mm wide and 13 incomplete specimens up to 18 mm (90 chaetigers), 0.6–1.0 mm wide.

Cape Banks: 34°00’S–151°16.00’E, 45–50 m, 0 3 Jan–18 Jan 1991, sta. 4-359 (AM W.49393:9).

Cobblers, Bate Bay: 34°05.9’S – 151°12.00’E, 35–40 m, 29 Oct–14 Nov 1990, sta. 3-113 (AM W.49394:2); same data, sta. 3-116 (AM W.49395:1).

Wattamolla, off Providential Head: 34°08.00’S–151°08.50’E, 35–40 m, 29 Oct–14 Nov 1990, sta. 3-63 (AM W.49396:1); same data, sta. 3-64 (AM W.49397:1).

Bass Point: 34°36’S–150°54’E, 35–40 m, 25 Jun–26 Jul 1990, sta. BP41 (AM W.49398:2); 34°36’S–150°54’E, 35–40 m, 3 Jan–18 Jan 1991, sta. 4-219 (AM W.49399:4).

Additional material examined: 64 complete specimens, 3.8–28 mm long (33–140 chaetigers), 0.3–1.0 mm wide; 148 incomplete specimens 0.3–1.0 mm wide.

Cape Banks: sta. 4-348 (AM W.49400:1); sta. 4-359 (AM W.49447:8).

Cobblers, Bate Bay: sta. C13 (AM W.49401:11); sta. C16 (AM W.49402:6); sta. C20 (AM W.49403:4); sta. C58 (AM W.49404:8); sta. C59 (AM W.49405:4); sta. 4-314 (AM W.49406:3); sta.4-315 (AM W.49407:12); sta. 4- 316 (AM W.49408:2); sta. 4-318 (AM W.49409:1); sta. 4-319 (AM W.49410:2); sta. 4-322 (AM W.49411:1).

Wattamolla, off Providential Head: sta. W5 (AM W.49412:3); sta. W10 (AM W.49413:11); sta. W12 (AM W.49414:1); sta. W34 (AM W.49415:2); sta. 3-72 (AM W.49416:2); sta. 4-261 (AM W.49417:2); sta. 4-262 (AM W.49418:7); sta. 4-264 (AM W.49419:2); sta. 2-265 (AM W.49420:7); sta. 268 (AM W.49421:2); sta. 4-280 (AM W.49422:2).

Bass Point: sta. BP1 (AM W.49423:7); sta. BP3 (AM W.49424:1); sta. BP8 (AM W.49425:6); sta. BP10 (AM W.49426:7); sta. BP11 (AM W.49427:8); sta. BP12 (AM W.49428:21); sta. BP14 (AM W.49429:2); sta. BP37 (AM W.49430:2); sta. BP47 (AM W.49431:2); sta. BP48 (AM W.49432:1); sta. 3-3 (AM W.49433:4); sta. 3-9 (AM W.49434:1); sta. 3-14 (AM W.49435:2); sta. 3-15 (AM W.49436:1); sta. 3-21 (AM W.49437:2); sta. 3-22 (AM W.49438:2); sta. 3-26 (AM W.49439:3); sta. 4-212 (AM W.49440:2); sta. 4-216 (AM W.49441:3); sta. 4-217 (AM W.49442:12); sta. 4-218 (AM W.49443:5); sta. 4-219 (AM W.49444:6); sta. 4-221 (AM W49445:7); sta. 4-229 (AM W.49446:1).

Type locality. Pacific Ocean, Bass Point, New South Wales; 34°36’S – 150°54’E, depth 25–30 m.

Diagnosis. Brown pigment on peristomium and as dorsal horizontal bands; peristomium anteriorly extended; antennae with 3–4 ceratophoral rings, styles to chaetiger 2–7; 3 pairs of modified parapodia with tridentate long- and short-appendaged pseudocompound hooks, median bidentate pseudocompound hook on chaetiger 4 present or absent; subacicular hooks from chaetiger 10–14; branchiae absent; fragile mucous tube with attached sand grains.

Description. Freshly preserved specimens overall cream coloured with brown pigment on dorsal surface in four different patterns (Fig. 1A–D). Holotype now without pigmentation, originally representing most common colour morph A (Fig. 1A): peristomium brown, chaetiger 1 lacking pigmentation; from chaetiger 2 to 3–12 two bands per segment, one complete anterior and one broken posterior one; both bands moving more posterior until anterior band in median position and posterior bands intersegmental; from chaetiger 4–13 only median band remaining and becoming progressively narrower, disappearing by chaetiger 30–50 (in holotype broken posterior band disappearing by chaetiger 12, leaving single band from chaetiger 12 to about 40). Colour morph B (Fig. 1B): same as morph A, except posterior broken bands from chaetiger 1. Colour morph C (Fig. 1C): similar to morph B, but two solid bands from chaetiger 2. Colour morph D (Fig. 1D): anterior chaetigers coloured like morph C, but from chaetiger 7–12 two bands fusing into wide single band; from chaetiger 13–15 single band changing to double again until chaetiger 16–40 (not illustrated); thereafter lower band disappearing, leaving single median band.

Prostomium about as wide as long, anteriorly extended, forming peak between frontal lips (Fig. 2A, B). Pair of small anterior eyespots between frontal lips and palps (Fig. 3A), pair of larger eyes consisting of group of spots between palps and lateral antennae. Ceratophores of palps and antennae short, with 2–3 proximal rings and longer distal ring, palpostyles about 3–4 times as long as palpophores, reaching chaetiger 1 (1–2); lateral antennostyles to chaetiger 4–5 (4–7), median antennostyles to chaetiger 2 (2–7) (Fig. 2A, B). Nuchal grooves straight with narrow midddorsal separation. Peristomial cirri absent.

First 3 pairs of parapodia modified, directed slightly anterolaterally and slightly prolonged. Prechaetal lobe extremely short, not protruding from prechaetal pocket (Fig. 3B); postchaetal lobe subulate, reduced from chaetiger 4 (Fig. 3C), becoming small knob from chaetiger 10–20 (Fig. 3D), absent by chaetiger 30–40. Dorsal cirri initially subulate, becoming smaller and digitiform after chaetiger 10; ventral cirri subulate to digitiform on anterior 3 chaetigers, then replaced by glandular pads. Branchiae absent.

Exclusively tridentate pseudocompound hooded hooks with short hoods present on anterior 3 chaetigers (Fig. 3B). Distal tooth large and falcate, middle tooth well developed, lowermost tooth small (Fig. 3E, F). Hooks consisting of 2 long-appendaged (Fig. 3E) and 2 short-appendaged (Fig. 3F) ones; short-appendaged hook in median position slightly thicker than lower one. Single median bidentate very short-appendaged pseudocompound hook (Fig. 3G) present or absent on chaetiger 4. Pectinate chaetae often absent, when present, occurring as 1 or 2 per parapodium from chaetiger 4 with slightly oblique combs and 7–9 long teeth (Figs 2C, 3H). Limbate chaetae absent from modified chaetigers, starting at chaetiger 4 as 5–6 long upper and 5–6 shorter lower chaetae; lower bundle replaced by 2 hooded bidentate subacicular hooks from chaetiger 14 (10–14) (Fig 3D).

Pygidium with two pairs of very thin anal cirri; dorsal pair as long as pygidium and 20 terminal segments, ventral pair about one tenth thereof. Mandibles very delicate even in mature animals; calcareous cutting plates small, only protomandibles sclerotized, remaining parts difficult to make out (Fig. 3I). Maxillae (Fig. 3J) lightly sclerotized, maxillary formula: Mx I = 1+1; Mx II = 6–7+7; Mx III = 7+0; Mx IV = 7+10; Mx V = 1+1. Fragile mucous tubes with attached sand grains.

Remarks. Aponuphis chistikovi from the Reykjanes Ridge in the North Atlantic and the Mediterranean A. willsiei were the only known abranchiate species in the genus; A. annae n. sp. and A. bellani n. sp. (described below) bring this number to four. The four species can be distinguished in that A. chistikovi and A. willsiei lack any pigmentation, while the Australian species have distinct colour patterns. Furthermore, the Australian species have less ceratophoral rings (2–4 vs. 3–6) and a later origin of subacicular hooks (10–28 vs. 8–10). The latter two species can be distinguished from each other in that A. annae n. sp. has a complex banded colour pattern, an extended prostomium, subacicular hooks from chaetiger 10–14, and a sandy tube, whilst A. bellani n. sp. has a median vertical stripe, an incised prostomium, subacicular hooks from chaetiger 23–28, and a transparent tightfitting smooth tube. Aponuphis annae n. sp. and A. bellani n. sp. differ from the third Australian species, A. danicae n. sp. (described below) in being abranchiate whilst the latter has a single branchial filament over a short region of its body, starting from chaetiger 14–26, ending on chaetiger 23–35. The three species differ further in colour patterns and origin of subacicular hooks; these and other differences are detailed in Table 1.

Etymology. This species is dedicated to Anna Murray to thank her for many years of friendship, and drawing my attention to these “peculiar little onuphids” when first encountered.

Biology. Two paratypes are ovigerous. One incomplete specimen (AM W.49394) has oocytes from chaetiger 39 to the end of the fragment (chaetiger 58) and one complete specimen consisting of 130 chaetigers (AM W.49395) has oocytes from chaetiger 50–66. The oocytes are very large, measuring 400 µm in diameter. Two paratypes collected during the 29 October–14 November 1990 sampling were brooding, AM W.49397 with 26 juveniles and AM W.49396 with 15 juveniles in their tubes. Both sets of young (Fig. 2D) consist of 14–17 chaetigers and measure about 1.5 mm in length and 0.3 mm in width without parapodia; they still contain a large amount of yolk. Their prostomium (Fig. 2E) bears two slight frontal protrusions marking the beginnings of the frontal lips, palps and antennae with short ceratophores and styles that reach to chaetiger 1. Anterior eyespots are present between the frontal protrusions and the palps. The first pair of parapodia is directed anteroventrally, the remaining ones laterally. Distinct dorsal cirri are present on chaetigers 1 to 11–12, ventral cirri on chaetiger 1 and 2.

Chaetiger 1 has four to five bidentate pseudocompound hooks. Chaetigers 2 to 8–10 bear one limbate chaeta and three anterior provisional subacicular hooks (similar to those described for juvenile A. ornata (Fauvel, 1928) by Arias & Paxton 2015. The first permanent subacicular hook occurs from chaetiger 9–11 to 10–12 together with a provisional one, while the following four to five parapodia have only one projecting aciculum. A pair of dorsal anal cirri measures about 100 µm and the ventral pair about one tenth thereof.

Small, recently settled juveniles were present during the January collections. The smallest measures 3.8 mm in length for 33 chaetigers, 0.3 mm in width, and possesses already pseudocompound hooks on the first three chaetigers as in adults but its subacicular hooks start on chaetiger 9.

Habitat and distribution. Aponuphis annae n. sp. was the most common of the three new species in the four sampling areas, occurring in 55 out of 100 stations. Whilst it was collected in depths between 25–50 m, its abundance peaked in 35–40 m (Fig. 7).