Magelona crenulifrons Gallardo, 1968

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 : 21-24

Magelona crenulifrons Gallardo, 1968

Figures 8, 13J

Magelona crenulifrons Gallardo, 1968: 100 , figs 1–4; Magelona crenulifrons – Mortimer & Mackie (2009:185–190, figs 2–4)

Material examined. Persian Gulf, IRAN—Stn. 24 ( NMW.Z.2010.037.0016; 2 af), 1998; Stn. B1–10 ( NMW.Z.2010.037.0017, grab A, 9 af; NMW.Z.2010.037.0018, grab B, 14 af; NMW.Z.2010.037.0019, grab C, 9 af), 2005; Stn. B1–15C ( NMW.Z.2010.037.0020; 1 af), 2005; Stn. B2–10 ( NMW.Z.2010.037.0021, grab A, 1 af; NMW.Z.2010.037.0022, grab B, 6 af; NMW.Z.2010.037.0023, grab C, 7 af), 2005; Stn. B2–15 ( NMW.Z.2010.037.0024, grab A, 1 af; NMW.Z.2010.037.0025, grab C, 1 af), 2005; Stn. B3–15 ( MNCN.16.01/ 13237, grab A, 3 af; MNCN.16.01/13238, grab B, 5 af; MNCN.16.01/13239, grab C, 1 af), 2005; Stn. B3–20 ( NMW.Z.2010.037.0026, grab A, 3 af; NMW.Z.2010.037.0027, grab B, 1 af; NMW.Z.2010.037.0028, grab C, 1 af), 2005; Stn. B4–10B ( MNCN.16.01/13240; 1 af), 2005; Stn. B4–15 (MB29–000193, grab B, 1 af; MB29– 0 0 0 194, grab C, 2 af), 2005; Stn. B4–20 (MB29–000195, grab A, 2 af; MB29–000196, grab B, 2 af; MB29– 0 0 0 197, grab C, 2 af), 2005; Stn. E10(1) ( MNCN.16.01/13241; 1 af, 1 f), 2006; Stn. E15 ( MNCN.16.01/13242, grab 1, 4 af; MB29–000198, grab 2, 1 af; MB29–000199, grab 3, 1 af), 2006; Stn. F20(1) ( NMW.Z.2010.037.0029; 3 af), 2006. QATAR—Stn. SB 1(1) ( NMW.Z.2010.037.0030; 1 af,), 2007; Stn. SBW 2(1) ( NMW.Z.2010.037.0031; 2 af, 1f), 2007; Stn. SB 3(1) ( NMW.Z.2010.037.0032; 5 af, 3 f, 2 pf), 2007; Stn. SB 4(1) ( NMW.Z.2010.037.0033; 3 af, 9 f), 2007; Stn. SBW 6(1) ( NMW.Z.2010.037.0034; 6 af, and 1 dissected af, 15 f), 2007; Stn. SB 7(1) ( NMW.Z.2010.037.0035; 14 af, 16 f, 1 pf), 2007; Stn. SB 8(1) ( MNCN.16.01/13243; 3 af, 1 f), 2007; Stn. SBW 10(1) ( MNCN.16.01/13244; 2 af), 2007; Stn. SB 11(1) ( MNCN.16.01/13245; 2 af, 1 f), 2007; Stn. SB 12(1) (MB29–000200; 2 af, 5 f), 2007; Stn. SB 13(1) (MB29–000201; 1 af, 1 f), 2007; Stn. SB 14(1) (MB29–000202; 3 af, 1 f), 2007; Stn. SB 15(1) ( NMW.Z.2010.037.0036; 3 af), 2007.

FIGURE 8. Magelona crenulifrons (A, B NMW.Z.2010.037.0036b; C −L, Slide preparations: dissected specimen NMW.Z.2010.037.0034b): (A) anterior, dorsal view, showing interparapodial abdominal glandular regions; (B) prostomium, dorsal view; (C −K) chaetigers 1, 2, 3, 5, 6, 7, 8, 9, 10 respectively (anterior views); (L) notopodium of chaetiger 24 (anterior view); (M) lateralmost thoracic capillary chaeta from notopodia of 3rd chaetiger; (N −P) bidentate abdominal hooded hooks (frontal, oblique lateral and lateral views respectively).

Diagnosis. Prostomium of similar length to width, spatulate, with distinct frontal horns; anterior margin crenulate. Notopodia of chaetigers 1–8 with foliaceous postchaetal lamellae expanded as cirriform dorsal processes. Neuropodia with slender cirriform ventral lobes. Chaetiger 9 with large distally pointed auricular lamellae, dorsal processes absent; neuropodia with short triangular postchaetal lobes and slender prechaetal lobes. Thoracic chaetigers with winged capillary chaetae. Abdominal lateral lamellae broadly spatulate, basally constricted. Abdominal inferior and superior processes, triangular. Hooded hooks bidentate, in two groups, vis-à-vis. Posteriorly open lateral pouches present abdominally.

Description. A moderately sized species, difference between two body regions not marked. Longest specimen, ovigerous (NMW.Z.2010.037.0026; eggs approximately 55 μm diameter, visible from approximately the 45th chaetiger), dimensions: prostomium 0.5 mm long, 0.5 mm wide; thorax 3.0 mm long (including prostomium), 0.4 mm wide; abdomen 0.4 mm wide; total length 22 mm for 54 chaetigers. Figured specimen (NMW.Z.2010.037.0036b) dimensions: prostomium 0.4 mm long, 0.4 mm wide; thorax (including prostomium) 3.0 mm long, 0.5 mm wide; abdomen 0.45 mm wide; total length 11.5 mm for 34 chaetigers. Other material 2.8–18 mm long for 12–57 chaetigers.

Prostomium slightly longer than, or of similar length to width (L:W ratio 1.0–1.33) (width measurements sometimes underestimated as lateral edges occasionally squashed); spatulate to rounded triangular, with distinct frontal horns; lateral margins rounded. Anterior margin crenulate, with 0–9 crenulations (generally 3–7) (degree of crenulation highly variable, some specimens appearing almost smooth with minute crenulations, others wavy or with distinct triangular crenulations (Figures 8A–B, 13J). Two pairs of prominent dorsal longitudinal muscular(?) ridges, inner pair diverging anteriorly and extending into frontal horns, outer pair abutting inners for entire length. Distinct muscular(?) areas either side of ridges. The proboscis is everted in 19 specimens, heart-shaped when fully everted, oval to round when partially everted. Proboscis longitudinally ridged inferiorly; superiorly appearing as a smooth pad. Palps retained (fully or partially) on 70 specimens; long and slender, reaching between chaetigers 9– 29. Non-papillated region long, reaching between chaetigers 1–5 (usually 3–4). Palps with 1–2 rows of papillae proximally either side of inconspicuous groove, and 1 (occasionally 2 in shorter palps) row either side distally. Papillae long at distal tips.

Achaetous region behind prostomium, around one and half times the length of chaetiger 1. Notopodia of chaetigers 1–8 similar, with large foliaceous postchaetal lamellae gradually increasing in size along thorax, inferiorly encircling chaetae, forming low triangular prechaetal lamellae (Figures 8C–I). Superiorly, single long, cirriform processes (DML) present. Neuropodia of chaetigers 1–8 similar, with slender cirriform ventral neuropodial lobes (VNL) decreasing gradually in size along thorax and expanding postchaetally from chaetiger 1. Postchaetal expansion increasing gradually in size along thorax, becoming quite distinct from chaetiger 7. Chaetiger 8 with conspicuous triangular postchaetal lamellae and single small slender cirriform ventral neuropodial lobes (Figure 8I).

Chaetiger 9: notopodial postchaetal lamellae shorter than those of preceding chaetigers; auricular and distally pointed; prechaetal lamellae low; superior prechaetal processes absent (Figure 8J). Neuropodial postchaetal lamellae of chaetiger 9 triangular, with slender lobes in prechaetal positions. All thoracic chaetae simple winged capillaries (Figure 8M).

Abdomen with large, spatulate lateral lamellae (toad-stool shape in profile), basally constricted, and of a similar size in both rami (Figures 8K, L). Postchaetal expansion behind chaetal rows evident in anterior abdomen. Triangular processes (DML and VML) evident throughout at inner margins of chaetal rows. Posteriorly open pouches present, from as early as chaetiger 24. Some variation in pouch location observed, however, often initially unpaired, alternating from one side of the body to the other, on alternate segments, then later appearing on alternate segments. Several posterior fragments present in samples (hook dentition would suggest they may belong to this species), no pygidial cirri observed, presumed missing(?).

Abdominal hooded hooks bidentate (Figures 8N–P). Hooks in two groups, vis-à-vis (Figures 8K, L), initially 7–10 per ramus. Both groups with approximately similar numbers of hooks. Small curved acicular support chaetae present, emerging at bases of lateral lamellae.

Colour. No live specimens observed. All specimens preserved in alcohol, cream-white in colour. Specimens stained with Rose Bengal, although pigmentation now weak in many specimens such as those collected during the Iran 2005 survey (however, initial concentration of Rose Bengal used may have been lower). Staining seen as very intense interparapodial abdominal patches, especially in the anterior abdomen; a large dorsal round spot present between chaetigers 1–2 in several specimens.

Methyl green staining pattern conspicuous, as described for type material ( Mortimer & Mackie 2009). Thoracic dorsal surface speckled all over, apart from mid-dorsal line and surrounding parapodia, slightly less staining in posterior thorax. Venter of thorax striped longitudinally, stripes narrowing to a point at the thoracic-abdominal junction. Staining slightly stronger between chaetigers 1–5. Characteristic medial V-shape observed on venter of most specimens (around chaetigers 5 to 6), usually visible without staining, although more difficult in smaller specimens. Staining in abdomen seen as small speckles along mid-ventral line, and small speckles surrounding interparapodial patches. Slight speckles on prostomium ( Figure 13 J). Methyl green staining pattern very constant throughout material.

Habitat. Known from Iranian waters in fine silt to coarse sand, 9–74.5 m ( Mortimer & Mackie 2009). Described here from a further 13 stations from 3 surveys off Iran in medium sand, shelly sand with low mud, shelly muddy sand, coarse shelly muddy sand, muddy sand, fine muddy sand, and sandy mud, 10–20 m, and 13 stations from a single survey off Qatar in muddy sand with shell debris, mud with some shelly sand, and mud, 57– 60 m.

Distribution. Vietnam ( Gallardo 1968), Iran, Qatar (present study; Mortimer & Mackie 2009), Hong Kong ( Mortimer & Mackie 2009), Natuna Islands, South China Sea ( Al-Hakin & Glasby 2004), Thailand (Nateewathana & Hylleberg 1991; Hylleberg & Nateewathana 1991), and Hong Kong ( Shin 1998; 2003).

Remarks. These specimens conform well to the re-description of the type material by Mortimer & Mackie (2009).

This material highlights the importance of making observations on pouch morphology and location from as many specimens as possible, as variations in pattern may be present. However, the patterns observed here were similar to that seen for Hong Kong specimens. Some pouches were observed to be paired, sometimes on consecutive segments, whilst others were present on alternating segments.

Figures

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.