Amaeana breviachaeta, Nogueira, João Miguel De Matos, Carrerette, Orlemir & Hutchings, Pat, 2015

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 : 13-14

Amaeana breviachaeta sp. nov.

Figures 3 C–E, 4

Material Examined: Holotype AM W.46526 (coll. M. Capa & P. Hutchings, 30.Aug.2010, during CReefs, on SCUBA, 9 m, fine sandy sediment): 1 incomplete specimen, with 28 segments; slides: notopodium, segment 8; neuropodium, segment 21; neuropodium, segment 27.

Type locality. Australia, Queensland, Great Barrier Reef, Lizard Island, Watsons Bay, 14°39'30"S, 145°26'56"E, 9 m.

Description. Holotype incomplete specimen, ~ 5 mm long, 1.1 mm wide at segment 7, maximum width of body.

Prostomium at base of upper lip, basal part as thickened crest, distal part with large, flaring lobes; mid-dorsal process on distal part of prostomium absent or, at least, not visible; prostomium covering segment 1 laterally and terminating laterally to lower lip, near mouth ( Fig. 4 A–F). Numerous buccal tentacles remaining, of three types, short ones thin, uniformly cylindrical; intermediate tentacles distally broader, spatulate; long tentacles progressively widening towards pair of globular and highly papillate subdistal swellings, followed by short and tapered tip ( Fig. 4 A–F).

Peristomium restricted to lips, upper lip relatively short, circular and somewhat convoluted, not clearly folded into three lobes; lower lip rounded, button-like ( Fig. 4 A, C, F).

Body distinctly swollen anteriorly, from segment 3, progressively broader until segments 6–7, then narrowing progressively until termination of notopodia, of uniform width on abdomen; short achaetous gap between termination of notopodia and beginning of neuropodia, corresponding to segments 12–14, much shorter than region with notopodia, with poorly marked segmentation and fragile, thin body wall dorsally ( Fig. 4 A–D, G).

Segments biannulated, segment 1 distinctly short, only visible mid-dorsally and ventrally, laterally covered by expanded prostomium; segment 2 narrow and much shorter than following segments, with relatively short midventral shield at beginning of mid-ventral groove ( Fig. 4 A, C, F). Ventrum highly glandular, covered with minute papillae, paired ventro-lateral pads poorly marked, present on segments 2–11, papillae progressively less conspicuous on segments 9–11, then smooth body wall, with paired longitudinal crests bordering mid-ventral groove through posterior body ( Fig. 4 A–G).

Notopodia extending through 9 segments, until segment 11; elongate, cylindrical notopodia, with equal lobes and elongate and distally blunt tips ( Fig. 4 A–G). Acicular notochaetae in both rows, as nearly alimbate capillaries, wings not visible under higher magnifications of light microscopy, only tips of chaetae from posterior row protruding from notopodial lobes ( Fig. 3 C).

Neuropodia present from segment 15, laterally to mid-ventral groove, on outer margins of longitudinal crests ( Fig. 4 A–B, G). Neurochaetae up to 5–6 thin, distally tapered spines, at least some with slightly hooked tip ( Fig. 3 D–E).

Nephridial and genital papillae anterior to bases of notopodia, larger on segments 5–8. Pygidium unknown.

Remarks. Amaeana breviachaeta sp. nov. is characterised by the distinctively short achaetous region between termination of notopodia and beginning of neuropodia, 3 segments only, from segments 12–14. Of the known species of Amaeana , only A. trilobata has a similar gap of 3 segments, although in this species the achaetous segments are 13–15. Amaeana ellobophora sp. nov. and A. accraensis ( Augener, 1918) also have a short achaetous gap, extending for 5 and 5–6 segments, respectively, segments 13–17 in A. ellobophora sp. nov., 14–15 to 20 in A. accraensis .

Members of A. trilobata differ from A. breviachaeta sp. nov. in having a different number of pairs of notopodia, 10 pairs, with notopodia present until segment 12, against 9 pairs as in A. breviachaeta sp. nov., extending to segment 11. As a consequence, these species also differ in the number of pairs of ventral glandular pads and nephridial and genital papillae, which are directly correlated with the number of pairs of notopodia. In addition, a prostomial process is absent and the modified type of buccal tentacles is present among members of A. breviachaeta sp. nov., which differs from A. trilobata ( Table 1).

In addition to the larger number of segments present in the achaetous gap between termination of notopodia and beginning of neuropodia, A. ellobophora sp. nov. also differs from A. breviachaeta sp. nov., in having a prostomial process on distal part of prostomium, 10 pairs of notopodia, with consequent differences in the number of pairs of ventral pads and nephridial and genital papillae, and 8–11 spines per neuropodium, while in A. breviachaeta sp. nov. there are only 5–6 spines per neuropodium.

Finally, members of A. accraensis have notopodia extending to segment 14, with distally pinnate notochaetae in posterior row, and ~ 8 spines per neuropodium. In contrast, members of A. breviachaeta sp. nov., have acicular, narrowly-winged chaetae in both rows, together with the numbers of pairs of notopodia and spines per neuropodium as just discussed (see Table 1).

Etymology. The epithet “ breviachaeta ” refers to the short achaetous region, between termination of notopodia and beginning of neuropodia; brevis = short, from the Latin.

Figures

FIGURE 3. Chaetae. Amaeana trilobata NMO C 3208: A, notochaetae, segment 5. B, neurochaetae, segment 45. Amaeana breviachaeta sp. nov., holotype AM W. 46526: C, notochaetae, segment 8. D – E, neurochaetae, segments 21 and 27, respectively. Amaeana angulus sp. nov., holotype AM W. 13640: F – G, notochaetae, segment 3. H, neurochaetae, segment 25. Scale bars: A, G – H = 80 µm; B, D – E = 10 µm; C = 20 µm; F = 150 µm.

FIGURE 4. Amaeana breviachaeta sp. nov., holotype AM W. 46526. A – B, incomplete worm, right ventro-lateral and left dorso-lateral views, respectively. C – D, anterior end, right ventro-lateral and left dorso-lateral views, respectively; arrows point to last notopodium. E – F, close ups of the anterior end, left dorso-lateral and ventral views, respectively. G, transition between thorax and abdomen; upper arrow points to last notopodium, lower arrow points to first neuropodium. Numbers refer to segments; ll = lower lip, P = basal part of prostomium; ul = upper lip; * = distal part of prostomium. Scale bars: A – B = 0.4 mm; C – D, G = 0.3 mm; E – F = 0.2 mm.