Magelona cf. falcifera Mortimer & Mackie, 2003

Mortimer, Kate, Cassà, Susanna, Martin, Daniel & Gil, João, 2012, New records and new species of Magelonidae (Polychaeta) from the Arabian Peninsula, with a re-description of Magelona pacifica and a discussion on the magelonid buccal region, Zootaxa 3331, pp. 1-43 : 24-27

Magelona cf. falcifera Mortimer & Mackie, 2003

Figures 9–10 , 13 K

Magelona falcifera Mortimer & Mackie, 2003: 167 –169, fig. 3?

Material examined. Persian Gulf, IRAN—Stn. 8 ( NMW.Z.2010.037.0008; 11 af, and 1 dissected af), 1998; Stn. 13 ( NMW.Z.2010.037.0009; 1 c, 11 af), 1998; Stn. 14 ( NMW.Z.2010.037.0010; 20 af), 1998; Stn. 24 ( MNCN.16.01/13232; 2 af), 1998; Stn. 8(1) ( NMW.Z.2010.037.0011; 37 af), 2002; Stn. 13(1) (MB29–000189; 23 af), 2002; Stn. B4–10 ( MNCN.16.01/13233, grab A, 15 af; MNCN.16.01/13234, grab B, 22 af; MB29–000190; grab C, 6 af), 2005; Stn. B4–15C ( NMW.Z.2010.037.0012; 1 af), 2005; Stn. F10 ( NMW.Z.2010.037.0013, grab 1, 2 c, 44 af; NMW.Z.2010.037.0014, grab 2, 4 af), 2006; Stn. F20(3) ( NMW.Z.2010.037.0015, 16 af), 2006. QATAR—Stn. E72A ( MNCN.16.01/13235; 1 af), 2005; Stn. G93 ( MNCN.16.01/13236, grab A, 3 af; MB29– 0 0 0 191, grab B, 1 af; MB29–000192, grab C, 1 af), 2005.

Diagnosis. Prostomium width similar to length, subtriangular without prostomial horns. Chaetigers 1–8 with lanceolate postchaetal lamellae, notopodial prechaetal lamellae indistinct and without dorsal superior processes. Chaetiger 9 with broad triangular postchaetal lamellae. All thoracic chaetae capillary. Abdominal chaetigers with lanceolate lateral lamellae and one enlarged hooded hook in anterior abdominal parapodia; other hooded hooks bidentate, those nearest the lateral lamellae more slender. Hooks in 2 groups, vis-à-vis. Lateral pouches absent. Methyl green staining particularly strong between chaetigers 5–9.

Description. A small slender species; difference between abdomen and thorax not marked ( Figure 9 A). Dimensions of figured complete specimen (NMW.Z.2010.037.0009): prostomium 0.4 mm long, 0.4 mm wide; thorax (including prostomium) 1.8 mm long, 0.45 mm wide (measured at widest point around chaetiger 7); abdomen 0.4 mm wide; total length 17.0 mm for 67 chaetigers. Other complete specimens (2) 5.5–6.7 mm for 45–52 chaetigers; remaining material 12–53 chaetigers, 1.3–13.5 mm.

Prostomium as long as, or less than width, subtriangular; anterior margin smooth and rounded, occasionally straight ( Figure 9 B) (Note: prostomium folded and curled in anterior drawing, Figure 9 A). Two pairs of longitudinal dorsal muscular(?) ridges; outer pair shorter and more indistinct, abutting inners for entire length; inner pair separated for majority of length, tips reaching distal prostomial margin. Indistinct (muscular?) areas either side of ridges, visible only under compound microscope. Proboscis everted in many specimens, oval to circular when partially everted, heart - shaped when fully everted. Proboscis ridged inferiorly, superior surface appearing smooth.

Palps present on several specimens, arising ventrolaterally from base of prostomium, reaching at least chaetiger 16–20, non-papillated region reaching chaetiger 3–5. Papillae: long, of similar lengths, digitiform; with 1 row of papillae, either side of inconspicuous ventral groove for length of palp.

Achaetous region behind prostomium roughly one and a half times the size of chaetiger 1; dorsal antero-lateral margins of which are rounded and expand over the base of the prostomium. Chaetigers 1–8 similar; parapodia biramous ( Figures 9 C–G); notopodia with low indistinct prechaetal lamellae. Superior notopodial prechaetal processes (DML) and ventral neuropodial lobes (VNL) absent. Postchaetal lamellae lanceolate, of about equal size in both rami, gradually becoming longer and broader along thorax.

Chaetiger 9: segment slightly narrower and thinner than previous segments. Prechaetal lamellae low; postchaetal lamellae broad triangular, with narrow tips ( Figure 9 H). Chaetae of all thoracic chaetigers simple capillaries.

Abdominal chaetigers with basally constricted lanceolate lateral lamellae of about equal size in both rami (Figures 9I –K), becoming more slender posteriorly. Lamellae do not appear to extend postchaetally. Small triangular processes (DML and VML) present at inner margins of chaetal rows.

A large sickle-shaped hook in both rami of anterior abdominal chaetigers present, no secondary teeth observed ( Figure 9 L); decreasing in size around chaetiger 20 and not apparent after chaetiger 25. A single small slender bidentate hook ( Figure 9 O) is present at the base of the lateral lamellae (and next to the enlarged hooded hooks in the anterior abdomen); appearing to emerge where the lamellae is basally constricted. Remaining hooks ( Figures 9 M–N) bidentate of similar size, hooks in two groups, main fangs vis-à-vis. Approximately four hooks present in anterior abdomen (one slender, one enlarged and two ‘ordinary’ hooks, as seen in figured specimen) increasing medially to approximately 6–8 hooks and posteriorly 4–6. Sporadic tridentate hooks observed in the posterior abdomen.

Eggs observed posteriorly (NMW.Z.2010.037.0008b; dissected af, visible from approximately the 30th chaetiger) packed within the body cavity, approximately 75 μm in diameter. Pygidium small with two slender lateral anal cirri ( Figure 9 P). No pouches observed.

Colour. No living animals observed, preserved colour uniformly cream/white in alcohol. Glandular areas noticeable interparapodially within the abdomen, staining lightly with Rose Bengal in some specimens. Staining with methyl green ( Figure 10 ) shows a diffuse overall stain, particularly strong between chaetigers 5–9. Dorsally, pale green speckled areas are present between chaetigers 1 to 4−5 (also seen as white speckles in unstained material). Darker transverse bands also present, level with parapodia on chaetigers 6–8; two longitudinal lines on chaetigers 7–8 either side of mid - dorsal line, and much darker pigmentation on lateral margins of chaetigers 6–9 (also seen on venter). Staining particularly strong around the parapodia of chaetiger 9; additional stain seen as speckles abdominally. Ventrally, speckled patches (lighter in colour) present medially between chaetigers 3–5 and denser staining medially between chaetigers 5–8. Abdominally, speckled areas interparapodially and ventrally either side of the mid-ventral line.

Habitat. Found at 10 stations from 4 surveys off the coast of Iran, in medium sand, shelly muddy sand, and fine shelly sand, 10–19 m, and 2 stations from one survey off Qatar, in medium sand, 15–18.4 m. Evidence of a sediment tube, present on many specimens.

Distribution. Iran, Qatar (present study), Seychelles ( Mortimer & Mackie 2003).

Remarks. The Persian material in general conforms well with the type material, however, several perceived differences exist. The original description depicts the prostomial shape as subhexagonal, however, having reviewed all material, prostomial shape varies from subtriangular to subhexagonal depending on the degree to which the lateral edges are inverted. Figure 11 A shows the prostomial shape of a dissected paratype, which agrees well with those seen in the Persian material. The figured Persian specimens appear slightly broader than the type material, however, both sets of material are generally of a similar size and breadth. Lastly, there seems to be a variation in the methyl green staining patterns ( Figures 10–11 ). The types of M. falcifera show a diffuse overall stain, with dorsal transverse white bands on chaetigers 6 and 7 and additional white patches on chaetigers 4, 5 and 8. Ventrally, white transverse bands are present between chaetigers 3–6, with additional white patches level with chaetigers 7 and 8, those of the later chaetiger being somewhat triangular. Additional, strong green speckles are often present as a transverse line around chaetigers 4–6 (one transverse line shown on Figure 11 , around chaetiger 5). No abdominal staining observed. The stain dissipated very quickly in the Seychellois material, in contrast to the Persian material that persisted for some time, still evident days after initial staining.

The morphological similarity between the Persian material and the type specimens is strong, with the only major difference appearing to be the variation in staining patterns. However, none of the perceived differences is deemed significant enough to warrant separation of this material at this time.

Figures

FIGURE 9. Magelona cf. falcifera (A, NMW. Z. 2010.037.0009, complete specimen; B – O, dissected 53 chaetiger specimen, NMW. Z. 2010.037.0008 b; P, NMW. Z. 2010.037.0013, 53 chaetiger complete specimen): (A) anterior, dorsal view (Note: prostomium slightly folded on right-hand side, indicated by dashed lines, distal tip folded upwards, marked by black lines either side of prostomium. White speckled areas between chaetigers 1 − 5 as dotted areas); (B) prostomium, dorsal view; (C – K) chaetigers 2, 3, 4, 7, 8, 9, 12, 13, 40 respectively (anterior views); (L) large sickle-shaped abdominal hooded hook; (M – N) bidentate abdominal hooded hooks, frontal and lateral views respectively; (O) small bidentate hooded hook, lateral oblique view (hood omitted for clarity); (P) posterior fragment, ventral view.

FIGURE 10. Persian Magelona cf. falcifera, methyl green staining pattern: (A) anterior, ventral view; (B) anterior, dorsal view.

FIGURE 11. Seychelles Magelona falcifera (A, paratype, NMW. Z. 2000.020.0014): (A) prostomium, dorsal view; (B – C) anterior region, methyl green staining patterns, ventral and dorsal views respectively. White bands and patches shown as dotted areas. Ventral strong green speckled transverse line demarked by darker dotted area in the region of chaetiger 5.

FIGURE 13. Prostomia of Arabian Peninsula Magelona species, dorsal views: (A) M. obockensis, 39 chaetiger anterior fragment, proboscis not everted, both palps attached, syntype, MNHN Type 1357; (B) M. obockensis, BMNH: ZB. 1971.54; (C) M. pulchella, holotype, BMNH 1969.391; (D) M. cornuta, holotype, ZMUC-POL- 969; (E) M. montera sp. nov. MNHN A 895; (F) M. sinbadi sp. nov., NMW. Z. 2010.037.0001; (G) M. cf. agoensis, NMW. Z. 2010.037.0004; (H) M. cf. cincta, NMW. Z. 2010.037.0041; (I) M. conversa, BMNH. 2010.234; (J) M. crenulifrons, NMW. Z. 2010.037.0024; (K) M. cf. falcifera, NMW. Z. 2010.037.0010 b; (L) M. symmetrica, NMW. Z. 2010.037.0047 b.