Magelona pulchella Mohammed, 1970

Mortimer, Kate, 2010, Magelonidae (Polychaeta) from the Arabian Peninsula: a review of known species, with notes on Magelona tinae from Thailand, Zootaxa 2628, pp. 1-26: 14-18

publication ID

10.5281/zenodo.198268

persistent identifier

http://treatment.plazi.org/id/03BDDD14-E460-553C-FF41-FDF0BB11FD67

treatment provided by

Plazi

scientific name

Magelona pulchella Mohammed, 1970
status

 

Magelona pulchella Mohammed, 1970 

Figures 9–10View FIGURE 9View FIGURE 10

Magelona pulchella Mohammed, 1970: 305  –306: figs 3–4

Material examined. Kuwait, Arabian Gulf, (29 ° 22 ’N, 48 °02’E), in sand, intertidal zone, Holotype ( BMNH 1969.391, c), collected by Murad-B. M. Mohammed, 5 / 6 / 1969.

Diagnosis. Prostomium as long as wide, subtriangular, with distinct prostomial horns. Notopodia of chaetigers 1–8 with lanceolate postchaetal lamellae and cirriform dorsal superior processes; neuropodia with digitiform ventral processes, those of chaetigers 7 and 8 with additional subtriangular postchaetal lamellae. Notopodia of chaetiger 9 with broadly rounded low postchaetal lamellae basally encircling chaetae to form digitiform processes beneath chaetae, neuropodia with a subtriangular postchaetal lamellae and small triangular prechaetal processes. All thoracic chaetae capillary. Abdominal lateral lamellae spatulate, bluntly pointed, basally constricted. Hooded hooks bidentate, in 2 groups, vis–à–vis. Posteriorly open pouches present on abdominal chaetigers.

Description. A moderately large species, appearing slightly dorso–laterally flattened; marked difference between abdomen and thorax, thorax narrower and thinner than abdomen ( Fig. 9View FIGURE 9 A). Dimensions: Prostomium 0.55 mm long, 0.6 mm wide; thorax (including prostomium) 4.0 mm long, 0.5 mm wide; abdomen 0.65 mm wide; total length ~ 36 mm for 108 chaetigers. Note: measurements less than those recorded by Mohammed, although width measurements may have included parapodia (see Mohammed 1973: p. 40). Chaetigers 7, 11– 13, 17 (notopodium only) and 24 on the left, and chaetigers 6, 9/ 10 (neuropodium only) and 29–30 on the right previously dissected. Body weakly attached between chaetigers 64–65.

Prostomium about as long as wide (L:W ratio 0.92), subtriangular, with distinct prostomial horns, anterior margin smooth, triangular; eyes absent. Two pairs of prominent longitudinal dorsal muscular ridges, outer pair shorter, abutting inners for entire length, inner pair abutting for majority of length, diverging distally into corners of frontal horns ( Figs 9View FIGURE 9 A–B, 10 A–B). Distinct large (muscular?) areas either side of ridges varying in shape and size (rounded rectangular, quadrangular or reniform). Proboscis only partially everted, oval; inferiorly longitudinal ridged. Right–hand palp present (left–hand palp detached, present in tube), long; arising ventrolaterally from base of prostomium, fairly robust in comparison to size of specimen, reaching at least chaetiger 25, non–papillated basal region reaching chaetiger 4. Papillae; short proximally, increasing in size, long distally. Initially 3 rows of papillae, with 1 row medially and distally, either side of inconspicuous ventral groove.

Peristomium achaetous, roughly one and a half times size of chaetiger 1. Chaetigers 18 similar; parapodia biramous; notopodia with low triangular prechaetal lamellae confluent with lanceolate postchaetal lamellae, becoming slightly longer throughout thorax ( Figs 9View FIGURE 9 C–H). Long, slender, tapering cirriform prechaetal superior processes (DML) present on all thoracic chaetigers, except chaetiger 9, all of similar size.

Neuropodia of chaetigers 1–8 with ventral digitiform processes (VNL), in distinctly prechaetal positions, increasing slightly in size to mid–thorax, becoming ventral in position. Small postchaetal expansion, becoming well–developed and triangular on chaetigers 7 and 8.

Chaetiger 9: shorter and narrower than preceding chaetigers ( Fig. 9View FIGURE 9 A). Notopodial prechaetal lamellae low, expanded as lateral digitiform processes underneath chaetae, confluent with rounded postchaetal lamellae, smaller than on preceding chaetigers ( Fig. 9View FIGURE 9 I). No superior processes (DML) observed. Neuropodia with triangular postchaetal lamella confluent with low prechaetal ridge, small ventral prechaetal process present (VML of some authors) (right neuropodium unknown due to dissection). Chaetae of all thoracic chaetigers simple winged capillaries (see Mohammed 1970: p. 306, figs 4 a & b).

Abdominal chaetigers with broad, spatulate lateral lamellae, of about equal size in both rami, basally constricted, bluntly pointed, lamellar shape shows some variation ( Fig. 9View FIGURE 9 J). Extension of the lateral lamellae behind chaetal rows well–developed, especially in anterior abdomen, apexes triangular. Small triangular processes (DML & VML) present at inner margins of chaetal rows. Posteriorly, lateral lamellae, much reduced, lanceolate.

Abdominal chaetae bidentate hooded hooks of similar size (not drawn to prevent further damage to the specimen). Hooks in two groups, main fangs vis–à–vis, groups at inner margins of chaetal rows with around twice number of chaetae. Initially around 10–14 hooks per rami.

Posteriorly open pouches (C configuration of Fiege et al. 2000 —see discussion) present posteriorly, initially on alternate chaetigers, then more or less on every segment, alternating again towards pygidium. Pouches differing from those seen on M. obockensis  and M. heteropoda  , less convoluted, simple folds; edges minutely wavy. Pouches observed on 39 R, 41 L, 43–44 L, 43 R– 85 R, 46 L– 82 L, 84 L– 86 L, 87 R, 88 L, 89 R, 90 L, 91 R, 92 L, 93 R, 94 L, 95 R, 96 L, 97 R, 98 L, 99 R, 100 L. Mohammed stated that the posterior end carries “a short anal cirrus on each side”, these were difficult to discern in the specimen, however two slender anal cirri were observed flattened against the pygidium.

Colour. The colouration originally described by Mohammed was “pinkish white anteriorly and greyish white posteriorly”. Preserved colour uniformly cream/yellow in alcohol, glandular areas noticeable interparapodially in abdomen. Staining with methyl green shows a diffuse overall stain dorsally in the thorax, particularly strong between parapodia of chaetigers 2 and 3 ( Figs 9View FIGURE 9 A, 10 A). This staining is retained long after the majority of stain has dissipated. Additional light speckling on the prostomium and in the anterior abdomen (as light transverse bands). Ventrally the staining is strongest between chaetigers 1 and 5 ( Fig. 10View FIGURE 10 B), particularly strong either side of the ventral grooves, staining of the posterior thorax is more diffuse. A distinct white X shape present ventrally between chaetigers 4 and 5 ( Fig. 10View FIGURE 10 C), the upper part being much thicker than lower. Some staining present interparapodially in the abdomen and small speckled patches ventrally either side of the mid–ventral line.

Habitat. Type specimen found in sand, Kuwait, Arabian Gulf. No other records of this species have been found by the author.

Remarks. This redescription details several features either omitted from, or incorrectly reported in the original description. In particular the shape of the prostomium, which in the original drawings is shown with more rounded lateral margins, and which terminates in a somewhat trilobed anterior margin. Further differences are the shape of thoracic neuropodial lamellae (particularly those of chaetigers 7 and 8, which have triangular postchaetal neuropodial lamellae), the presence of a neuropodial ventral process on chaetiger 9, the presence of small processes at the inner margins of chaetal rows on abdominal chaetigers (DML & VML) and abdominal hooded hooks in two groups, vis–à–vis.

Mohammed stated that M. pulchella  most resembled M. cornuta  (Mohammed 1970: p. 306), but differed in not possessing branchiae (cf. Wesenberg-Lund 1949: p. 328). Wesenberg-Lund when describing M. cornuta  stated “The parapodia are all biramous, those of the first 8 chaetigers with small foliaceous dorsal and ventral cirri or “postsetal lobes”. In front of the dorsal cirrus a small cirriform branchia is found.” The ‘dorsal and ventral cirri’ described by Wesenberg-Lund are likely to be those structures currently termed lateral lamellae, and the ‘small branchia’ the dorsal superior processes (DML), as shown by Mortimer & Mackie (2009).

Magelona pulchella  shares similarities with M. cornuta  , M. gemmata Mortimer & Mackie, 2003  , M. lenticulata Gallardo, 1968  , M. tehuanensis Hernández-Alcántara & Solís-Weiss, 2000  , M. berkeleyi Jones, 1971  , M. nonatoi Bolívar & Lana, 1986  and two unnamed species (J and L) from the Gulf of Mexico ( Uebelacker & Jones 1984) in possessing prostomial horns and in the nature of the thoracic lamellae.

However, it differs from them in possessing bidentate and not tridentate abdominal hooded hooks. It further shares similarities with M. annulata Hartmann-Schröder, 1962  , M. crenulifrons  , M. longicornis Johnson, 1901  , M. methae Nateewathana & Hylleberg, 1991  , M. pacifica Monro, 1933  and one unnamed species (G) from the Gulf of Mexico ( Uebelacker & Jones 1984), all of which possess bidentate hooded hooks. Magelona pulchella  can be distinguished from M. annulata  in possessing dorsal superior processes on chaetigers 1–8 and can be distinguished from M. crenulifrons  and M. methae  in not having a crenulate anterior prostomial margin. The anterior margin of M. longicornis  can also be crenulate, however M. longicornis  further differs from M. pulchella  in possessing abdominal hooded hooks in one group, main fangs facing laterally. It appears to most closely resemble M. pacifica  and M. sp. G. but differs in possessing more slender lanceolate postchaetal thoracic lamellae, however, further descriptions of these species would enable better cross– comparisons.

The presence of a characteristic unstained V shape on the venter of M. crenulifrons  was noted by Mortimer & Mackie (2009; p. 190), the point of which was often at the junction between chaetigers 5 and 6. This feature shares many similarities with the unstained X shape present on the venter of M. puchella  between chaetigers 4 and 5, particularly the thicker upper region. However, M. pulchella  is also distinguished from M. crenulifrons  by deep staining on dorsum between parapodia of chaetigers 2 & 3.

Kingdom

Animalia

Phylum

Annelida

Class

Polychaeta

Order

Spionida

Family

Magelonidae

Genus

Magelona

Loc

Magelona pulchella Mohammed, 1970

Mortimer, Kate 2010

2010
Loc

M. gemmata

Mortimer & Mackie 2003

2003
Loc

M. tehuanensis Hernández-Alcántara & Solís-Weiss, 2000

Hernandez-Alcantara & Solis-Weiss 2000

2000
Loc

M. methae

Nateewathana & Hylleberg 1991

1991
Loc

M. nonatoi Bolívar & Lana, 1986

Bolivar & Lana 1986

1986
Loc

M. berkeleyi

Jones 1971

1971
Loc

Magelona pulchella

Mohammed 1970: 305

1970
Loc

M. lenticulata

Gallardo 1968

1968
Loc

M. annulata Hartmann-Schröder, 1962

Hartmann-Schroder 1962

1962
Loc

M. pacifica

Monro 1933

1933
Loc

M. longicornis

Johnson 1901

1901