Amaeana accraensis ( Augener, 1918 )

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 : 46-47

Amaeana accraensis ( Augener, 1918)

Figures 26 and 27

Amaea accraensis Augener 1918: 561 –562, Pl. VII, Fig. 246, Text fig. ZCVIII. Amaeana accraensis .— Hartman 1959: 495.

Material examined. Holotype ( ZMH V- 1710): incomplete specimen, in relatively good state of preservation, missing most buccal tentacles; slides: notochaetae, segment 8; neurochaetae, segment 42.

Type locality. Accra, Ghana, 5°32'00"N, 0°12'00"W.

Description. Holotype incomplete specimen, ~ 14.5 mm long, 2.1 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 large, rounded and flaring lobes, and also rectangular to crescent-like mid-dorsal process, rounded at inferior corners; prostomium covering segment 1 laterally and terminating laterally to lower lip, near mouth ( Fig. 26 A–D, F–I). Most buccal tentacles missing, only few remaining, relatively short and thin, uniformly cylindrical ( Fig. 26 A– D, F–I).

Peristomium restricted to lips, upper lip almost circular, folded into three lobes; lower lip relatively large, rounded to oblong ( Fig. 26 A–D, F–I).

Body progressively broader until segments 7–8, slightly tapered on segments 9–11, then of uniform width through segment 15, more markedly tapering to narrower uniformly cylindrical posterior body, beginning from segment 20; achaetous gap between termination of notopodia and beginning of neuropodia, corresponding to segments 15 (left side of body)–16 (right side) through 20, with poorly marked segmentation and fragile, with thin body wall dorsally, distinctly shorter than region with notopodia ( Fig. 26 A–B).

Segments biannulated, segment 1 short, visible dorsal and ventrally, laterally covered by expanded prostomium; segment 2 narrower and shorter than following segments, with relatively small, rectangular to pentagonal mid-ventral shield at beginning of mid-ventral groove, about same length as that of segment 3 and slightly narrower ( Fig. 26 A–D, F–I). Ventrum highly glandular, covered with small papillae, arranged on paired ventro-lateral pads on segments 2–15; papillae about same size throughout and slightly more numerous on anterior segments, progressively less abundant on segments 12–15, then smooth body wall, with paired longitudinal crests bordering mid-ventral groove through posterior body ( Fig. 26 A–J).

Notopodia extending through 12 (left side of body)–13 (right side) segments, until segments 14 and 15, respectively; elongate, cylindrical notopodia, with equal sized lobes and elongate and distally blunt tips ( Fig. 26 A– D, F–I). Acicular, narrowly-winged notochaetae in anterior row, wings not visible under higher magnifications of light microscopy, distally pinnate notochaetae in posterior row ( Fig. 27 A–C).

Neuropodia present from segment 21, laterally to mid-ventral groove, on outer margins of longitudinal crests ( Fig. 26 A–B, E, J). Neurochaetae up to ~ 8 relatively thin, distally tapered spines, with slightly hooked and distally blunt tips ( Fig. 27 D).

Nephridial and genital papillae ventral and slightly anterior to bases of all notopodia, all relatively small. Pygidium unknown.

Remarks. Members of A. accraensis are unique among all species of Amaeana in having distally pinnate chaetae in posterior row of notochaetae, instead of acicular narrowly-winged chaetae. Amaeana hsiehae sp. nov. also has pinnate chaetae, but in this species they are present in both rows ( Table 1).

Besides, although it is not clear if 12 or 13 pairs of notopodia are present, as the holotype have different numbers from right to left sides of the body, this is a large number of pairs for a species of Amaeana . No other species has 13 pairs, and only two others have 12 pairs, A. occidentalis and A. yirrarn , as already discussed (see above). The differences between members of A. accraensis sp. nov., A. occidentalis and A. yirrarn were discussed above.

Figures

FIGURE 26. Amaeana accraensis holotype ZMH V – 1710. A – B, entire worm, right and left lateral views, respectively; arrows point to last notopodia (upper) and first neuropodia (lower). C – D, anterior end, dorsal and ventral views. E, abdominal segments. F – I, close ups of the anterior end, left dorso-lateral, right ventro-lateral, dorsal and ventral views, respectively. J, posterior end, ventral view. Numbers refer to segments; ll = lower lip, P = basal part of prostomium; PP = prostomial process; ul = upper lip; * = distal part of prostomium. Scale bars: A – B = 0.6 mm; C – E, J = 0.3 mm; F – I = 0.2 mm.

FIGURE 27. Amaeana accraensis holotype ZMH V- 1710. A, notochaetae, segment 8; B, notochaetae from anterior row, segment 8; C, tips of notochaetae from posterior row, segment 8; D, neuropodial spines, segment 42. Scale bars: A = 30 µm; B – D = 10 µm.