Amaeana yirrarn Hutchings, 1997

Nogueira, João Miguel De Matos, Carrerette, Orlemir & Hutchings, Pat, 2015, Review of Amaeana Hartman, 1959 (Annelida, Terebelliformia, Polycirridae), with descriptions of seven new species, Zootaxa 3994 (1), pp. 1-52 : 40-42

Amaeana yirrarn Hutchings, 1997

Figures 23 , 24 A–C

Amaeana yirrarn Hutchings 1997: 136 –138, Fig 1 A–D.

Material examined. Paratype AM W.21888 (coll. Port Essington, West Bay, Northern Australia, Australia; 11°16'S, 132°09'E, 14.Sep.1985): incomplete, in good state of preservation; slides: notochaetae, segment 11; neuropodium, segment 36.

Type locality. Port Essington, West Bay, Northern Territory, Australia, 11°16'S, 132°09'E, at low water.

Description: Paratype incomplete, 7 mm long, 1 mm wide at segment 8, maximum width of body.

Prostomium at base of upper lip, both basal and distal parts developed, basal part as thickened crest, distal part with relatively large, flaring lobes and also short, rounded to squared mid-dorsal process; prostomium covering segment 1 laterally and terminating laterally to lower lip, near mouth ( Fig. 23 A–E). Few buccal tentacles remaining on paratype, of three types, short ones thin, uniformly cylindrical; intermediate tentacles distally spatulate; long buccal tentacles progressively widening towards clearly marked subdistal conical inflation, cup-shaped, with short pointed to distally blunt tip ( Fig. 23 A–E).

Peristomium restricted to lips, upper lip short, almost circular, not clearly folded into three lobes; lower lip short, rounded to rectangular ( Fig. 23 A–C, E). Body distinctly swollen anteriorly, progressively broader until segments 7–8, then of uniform width until segment 14, tapering on segments 15–20, and again of relatively uniform width through posterior body, distinctly narrower than anterior segments ( Fig. 23 A–E); achaetous gap between termination of notopodia and beginning of neuropodia, corresponding to segments 15 to 21–23, slightly shorter than all region with notopodia, with poorly marked segmentation and fragile, with thin body wall dorsally ( Fig. 23 A).

Segments biannulated, segment 1 short, visible dorsal and ventrally, laterally covered by expanded prostomium; segment 2 narrower and shorter than following segments, with relatively short, rectangular to pentagonal mid-ventral shield at beginning of mid-ventral groove, extending anteriorly through segment 1 until near ventral edge of lower lip ( Fig. 23 A–E). Ventrum highly glandular, covered with small papillae, arranged in paired ventro-lateral pads on segments 2–14; papillae larger and more numerous on anterior segments, covering segmental annulations, papillae progressively less numerous on segments 10–14, still present on both annulations of each segment ( Fig. 23 A–C, E).

Notopodia extending through 12 segments, until segment 14; elongate, cylindrical notopodia, with equal sized lobes and elongate and distally blunt tip ( Fig. 23 A–E). Acicular, narrowly-winged notochaetae in both rows, wings not visible under higher magnifications of light microscopy ( Fig. 24 A–B).

Neuropodia present from segments 22–24 (22 in paratype), laterally to mid-ventral groove, on outer margins of longitudinal crests. Neurochaetae as 2 thick, distally tapered spines, apparently with straight tips ( Fig. 24 C).

Nephridial and genital papillae at anterior bases of all notopodia ( Fig. 23 A–E). Pygidium unknown.

Remarks: Amaeana yirrarn Hutchings, 1997 has 12 pairs of notopodia, the largest number of pairs among all known species in this genus, a character shared with A. accraensis and A. occidentalis , as already discussed. The differences between specimens of A. yirrarn and A. occidentalis ( Hartman, 1944) , were discussed above, while the holotype of A. accraensis is distinguished from A. yirrarn in having 5–6 segments in the achaetous gap between termination of notopodia and beginning of neuropodia, neuropodia with 8 slender spines each and also pinnate chaetae in posterior row of notochaetae ( Table 1). Members of A. yirrarn , in contrast have achaetous gap of 7–9 segments, 1–2 stout spines per neuropodium, and acicular, narrowly-winged notochaetae in both rows.

The most diagnostic character of A. yirrarn is the presence of 1–2 stout, distally sharp spines per neuropodium throughout, instead of several slender spines, frequently modified at tips. This character is only shared with members of A. apheles ( Hutchings, 1974) , but those have only 9–10 pairs of notopodia and also a larger upper lip and long buccal tentacles with different morphology (compare our Fig. 9 with Fig. 23 ).

Figures

FIGURE 1. Amaeana ellobophora, paratype 1 AM W. 10341, with egg cocoons: A, entire worm, dorsal view. B, anterior end, dorsal view. Scale bars: A = 0.5 mm; B = 0.3 mm.

FIGURE 9. Amaeana apheles, holotype AM W. 5239. A – C, anterior end, dorsal, right ventro-lateral, and ventral views, respectively. D – F, closer views of the anterior end, left and right ventro-lateral, and ventral views, respectively; arrows point to nephridial / genital papillae. G – H, close ups of the anterior end, dorsal and ventral views, respectively. Specimen AM W. 29203: I – J, notochaetae, segment 9. K, neurochaetae, posterior segment. Numbers refer to segments; ll = lower lip, P = basal part of prostomium; PP = mid-dorsal prostomial process; ul = upper lip; P * = distal part of prostomium. Scale bars: A = 0.7 mm; B – C = 1 mm; D – F = 0.5 mm; G – H = 0.3 mm; I – K = 20 µm.

FIGURE 23. Amaeana yirrarn paratype AM W. 21888. A, entire worm, right lateral view. B – C, thorax right and left lateral views, respectively. D – E, close ups of the anterior end, dorsal and ventral views, respectively. Numbers refer to segments; ll = lower lip, P = basal part of prostomium; PP = prostomial process; P * = distal part of prostomium; ul = upper lip. Scale bars: A = 1.5 mm; B – C, E = 0.7 mm; D = 0.4 mm.

FIGURE 24. Chaetae. Amaeana yirrarn paratype AM W. 21888. A, notochaetae, segment 11. B, close up of the notochaetae from posterior row, segment 11. C, neurochaetae, segment 36. Amaeana dampierensis sp. nov. AM W. 47405. D, tips of notochaetae from posterior row, segment 7. E, neurochaetae, segment 29. Amaeana brasiliensis sp. nov. paratype MZUSP 2726. F – G, notochaetae, segment 4. H, neurochaetae, segment 34. I, neurochaetae, segment 36. Scale bars: A = 50; B – D, H – I = 5 µm; E = 10 µm; F = 40 µm; G = 2 µm.