Amaeana occidentalis ( Hartman, 1944 )

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 : 34-40

Amaeana occidentalis ( Hartman, 1944)

Figures 18 , 19 , 20 , 21 and 22

Amaea occidentalis Hartman 1944: 277 –278, Pl. 26, figs 68, 69.

Amaeana occidentalis . Hartman 1959: 495. — Hilbig 2000: 238 –240, Fig. 9.1.

Material examined. Holotype LACM-AHF Poly 230 (coll. USA, California, Marin County, Tomales Bay, Inverness, just north of village, 38°05'54"N, 122°51'07"W, mud flat, soft black mud mixed with shell fragments, by O. Hartman, Jul.1935): incomplete, in good state of preservation, ~ 65 mm long, ~ 4 mm wide. Non-type specimens: LACM-AHF Poly 6517 [coll. USA, California, Monterey County, Moss Landing, Elkhorn Slough, several hundreds north of the current mouth (south mouth before mouth shifted), 36°38'31"N, 121°47'10"W, mudflat, Sta. McGinitie 5, coll. T. H. Bullock, 19.Jun.1939]: 6 specimens, some complete, although several in more than one piece, most of them in good state of preservation, dark brown to purple; slides (from complete specimen, in two pieces, LACM-AHF 6517): notochaetae segment 7, neurochaetae mid-abdominal segment, neurochaetae posterior segment. LACM-AHF Poly 6518 (coll. USA, California, Humboldt County, off Eureka, Eel River South, MBARI- Seep, 40°42'14"N, 124°22'22"W, 39.62 m, sediment near cold seep, Shipek grab, R/V McGAW Sta. Shipek 65, by Lisa Levin, Leslie H. Harris et al., 21.Oct.1998, id L. Harris): complete specimen, in excellent state of preservation, ~ 31 mm long, 2 mm wide, mounted on SEM stub.

Type locality. USA, California, Marin County, Tomales Bay, 38°05'54"N, 122°51'07"W, 58 m.

Description. Holotype incomplete specimen, ~ 65 mm long, ~ 4 mm wide at segment 8, maximum width of body. Life specimens yellow sulphur, becoming purple after preservation (L. Harris personal communication).

Prostomium at base of upper lip, both basal and distal parts developed, basal part as thickened crest, distal part with large, rounded flaring lobes, mid-dorsal process not visible, if present, hidden by large number of buccal tentacles; prostomium covering segment 1 laterally and terminating laterally to lower lip, near mouth ( Figs 18 A–E, G–H; 19A, C; 20B–E, G; 21G). Buccal tentacles of three types, short ones thin, uniformly cylindrical, except for expanded sphaerical to elliptical tips; intermediate tentacles thin, uniformly cylindrical, also expanded at tip; long buccal tentacles progressively widening at tip, towards clearly marked subdistal cylindrical inflation, with short and pointed tip ( Figs 18 A–E, G–H; 19A, C; 20A–G; 21A–G); all types with ciliated groove only conspicuous at tips.

Peristomium restricted to lips, upper lip almost circular; lower lip short, rounded ( Figs 18 A, C, E, G–H; 19A, C; 20B, D–E, G; 21G). Body abruptly broader on segments 3–5, of relatively uniform width until segment 10, slightly tapered on segments 11–14, then more markedly tapering to narrower uniformly cylindrical posterior body, beginning from segment 17–18 and tapering near pygidium ( Figs 18 A–H; 19A, C, F; 20A–I); long achaetous gap between termination of notopodia and beginning of neuropodia, corresponding to segments 15–37, with poorly marked segmentation and fragile, with thin body wall dorsally, distinctly longer than region with notopodia ( Figs 18 A, B–D, F; 19A, F; 20A–B, G–H).

Segments biannulated, segment 1 short, visible dorsally and ventrally; segment 2 narrower and shorter than following segments, with relatively small, pentagonal mid-ventral shield at beginning of mid-ventral groove, extending anteriorly through segment 1 until near ventral edge of lower lip, shield about same length as that of segment 3 and slightly broader ( Figs 18 A–E, G–H; 19A, C; 20D–E; 21G). Ventrum highly glandular, covered with small papillae, arranged in paired ventro-lateral pads on segments 2–14; papillae about same size throughout and slightly more numerous on anterior segments; from after termination of notopodia, paired longitudinal crests bordering mid-ventral groove through posterior body ( Figs 18 A, C, E, H; 19A, C, F; 20A–E, G–H; 22A–B).

Notopodia extending through 12 segments, until segment 14; elongate, cylindrical notopodia, with equal sized lobes and elongate and distally blunt tips ( Figs 18 A–E, G–H; 19A, C; 20A–H; 21G; 22G–I). Acicular, narrowlywinged notochaetae in both rows, wings inconspicuous under higher magnifications of light microscopy, those from anterior row ¼ length of chaetae from posterior row, or less, barely protruding from parapodial lobes ( Figs 21 B, D–E; 22G–I).

Neuropodia present from segment 38, laterally to mid-ventral groove, on outer margins of longitudinal crests. On anterior neuropodia, neurochaetae as up to 12–13 relatively stout, distally tapered spines, slightly expanded subdistally, with oblique tip ( Fig. 19 G); posterior neuropodia with fewer spines, 8–9 ( Fig. 19 H); at least some spines protruding from neuropodia ( Figs 18 A–B, F; 19A, F; 20I; 22A–E).

Nephridial and genital papillae anterior to bases of all notopodia, those of segments 6–9 largest ( Figs 18 B–E, G–H; 19A, C; 20A–H). Pygidium crenulate, with slightly larger ventral papilla ( Figs 19 A, F; 20I; 21H).

Remarks. Amaeana occidentalis is characterised by the great length of the achaetous gap between termination of notopodia and beginning of neuropodia, consisting of more than 20 segments. Also, members of A. occidentalis present the highest numbers of spines per neuropodium, 12–13 on anterior neuropodia, 8–9 on posterior ones, and numbers of pairs of notopodia among all species of Amaeana , 12 pairs, although this latter character is shared with A. accraensis and A. yirrarn ( Table 1).

The only other species with more segments in the achaetous gap is A. antipoda ( Augener 1926) , according to the original description, but members of this species only have 13–15 achaetous segments and have fewer neuropodial spines per neuropodium, about 4–5 spines, and only 11 pairs of notopodia ( Table 1). In addition, as said above, we consider this species as nomem nudum (see Material and methods).

The other species of Amaeana with 12 pairs of notopodia are both easily distinguished from A. occidentalis ( Hartman 1944) , by the number of spines per neuropodium, in addition to the extension of the achaetous gap. The type of A. accraensis has an achaetous gap of 5–6 segments and 8 spines per neuropodium, while in A. yirrarn Hutchings, 1997 , the gap extends for 7–9 segments and there are 1–2 spines per neuropodium ( Table 1). In addition, notochaetae in the posterior row are distally pinnate among specimens of A. accraensis , while in A. occidentalis they are acicular.

Figures

FIGURE 18. Amaeana occidentalis holotype LACM-AHF Poly 230. A – B, entire worm, ventral and dorsal views (anteriorly), respectively. C, anterior end, ventral view. D – E, thorax dorsal and ventral views, respectively. F, abdominal segments; arrow points to first neuropodium. G – H, close ups of the anterior end, dorsal and ventral views, respectively. Numbers refer to segments; ll = lower lip, P = basal part of prostomium; ul = upper lip; * = distal part of prostomium. Scale bars: A – B, E = 1.5 mm; C – D = 1 mm; F – H = 0.5 mm.

FIGURE 19. Amaeana occidentalis LACM-AHF Poly 6518. A, entire worm, left ventro-lateral view (anteriorly). C, anterior end, left ventro-lateral view. F, posterior end. Specimen LACM-AHF Poly 6517. B, notochaetae, segment 7; arrow point to notochaetae from anterior row. D, notochaetae from anterior row, segment 7. E, tips of notochaetae from posterior row, segment 7. G, mid-abdominal neurochaetae. H, posterior neurochaetae. Scale bars: A = 1 mm; C, F = 0.6 mm; B = 100 µm; D, G = 20 µm; E = 30 µm; H = 10 µm.

FIGURE 20. Amaeana occidentalis LACM-AHF Poly 6518. A – B, thorax, right lateral and left dorso-lateral views. C, anterior end, left dorso-lateral view. D – E, progressively closer ventral views of the thorax, ventral views. F – G, thorax, dorsal and left lateral views. H, segments 10 – 15, left lateral view; arrows point to genital papillae. I, posterior end, left ventro-lateral view. Scale bars: A – D, F = 0.7 mm; E, G = 0.4 mm; H = 0.3 mm; I = 0.15 mm.

FIGURE 21. Amaeana occidentalis LACM-AHF Poly 6518. A – F, tips of buccal tentacles. G, close up view of the anterior end, ventral view. H, close up of the posterior end, frontal view. Numbers refer to segments; ll = lower lip; P = basal part of prostomium; ul = upper lip. Scale bars: A, G = 0.2 mm; B, D, F = 0.1 mm; C = 0.15 mm; E = 40 µm; H = 50 µm.

FIGURE 22. Amaeana occidentalis LACM-AHF Poly 6518. A, posterior end, ventral view (anteriorly). B, abdominal segments. C – F, close ups of abdominal neuropodia, with protruding spines. G, notopodia, segments 3 – 5; arrows point to nephridial papillae. H – I, progressively closer views of the notochaetae of segment 5. Scale bars: A = 0.5 mm; B = 0.15 mm; C = 10 µm; D = 3 µm; E = 5 µm; F = 2 µm; G = 70 µm; H – I = 20 µm.